SH2B adapter protein 1, 2, and 3 Pleckstrin homology (PH) domain; SH2B family/APS proteins are a family of intracellular adaptor proteins that influences a variety of signaling pathways mediated by Janus kinase (JAK) and receptor tyrosine kinases (RTKs) including receptors for insulin, insulin-like growth factor-1, Janus kinase 2 (Jak2), platelet derived growth factor, fibroblast growth factor and nerve growth factor. They function in glucose homeostasis, energy metabolism, hematopoesis and reproduction. Mutations in human SH2B orthologs are associated with metabolic disregulation and obesity. There are several SH2B members in mammals: SH2B1 (splice variants: SH2B1alpha, SH2B1beta, SH2B1gamma, and SH2B1delta), SH2B2 (APS) and SH2B3 (Lnk). They contain a PH domain, a SH2 domain, a proline rich region, multiple consensus sites for tyrosine and serine/threonine phosphorylation and a highly conserved c-Cbl recognition motif. These domains function as protein-protein interaction motifs which allows SH2B proteins to integrate and transduce intracellular signals from multiple signaling networks in the absence of intrinsic catalytic activity. SH2B proteins bind via their SH2 domains to phosphotyrosine residues within the intracellular tails of several activated RTKs thereby contributing to receptor activation. SH2B proteins have been shown to interact with insulin receptor substrates IRS1 and IRS2, Grb2, Shc and c-Cbl which may or may not require RTK-stimulated tyrosine phosphorylation of SH2B. positively and negatively regulating RTK signaling. Understanding the physiological functions of SH2B proteins in mammals has been complicated by the presence of multiple SH2B isoforms and conflicting data. Both SH2-Bbeta and APS associate with JAKs, but the former facilitates JAK/STAT signaling while the latter inhibits it. Lnk plays a role in cell growth and proliferation with mutations resulting in growth reduction, developmental delay and female sterility. Recently Lnk Drosophila has been shown to be an important regulator of the insulin/insulin-like growth factor (IGF)-1 signaling (IIS) pathway during growth. PH domains have diverse functions, but in general are involved in targeting proteins to the appropriate cellular location or in the interaction with a binding partner. They share little sequence conservation, but all have a common fold, which is electrostatically polarized. Less than 10% of PH domains bind phosphoinositide phosphates (PIPs) with high affinity and specificity. PH domains are distinguished from other PIP-binding domains by their specific high-affinity binding to PIPs with two vicinal phosphate groups: PtdIns(3,4)P2, PtdIns(4,5)P2 or PtdIns(3,4,5)P3 which results in targeting some PH domain proteins to the plasma membrane. A few display strong specificity in lipid binding. Any specificity is usually determined by loop regions or insertions in the N-terminus of the domain, which are not conserved across all PH domains. PH domains are found in cellular signaling proteins such as serine/threonine kinase, tyrosine kinases, regulators of G-proteins, endocytotic GTPases, adaptors, as well as cytoskeletal associated molecules and in lipid associated enzymes.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 24650177 197 ECRKEGTVNNLTPESLdQPTGSQKWEKCRLVLVKAVGG---YMLEFYTPHKATKPRSGVFCFLISEARETTALEMPDRLN 273
Cdd:cd01231   1 ECRKEGIVNYLSGEET-ASDGGPRWQKCRLVLVKAAGGegeYLLEFYVPPKSSKPKLGIFCSLIQEVRETTALEMPDNEN 79

                        90       100       110
                ....*....|....*....|....*....|....*
gi 24650177 274 TFVLKADNNMEYVIEAESAEEMRSWLATIRYCMRT 308
Cdd:cd01231  80 TFVLKVENSTEYIIEAGDEQQMRSWLAEIRECMSP 114

SH2B adapter protein 1, 2, and 3 Pleckstrin homology (PH) domain; SH2B family/APS proteins are a family of intracellular adaptor proteins that influences a variety of signaling pathways mediated by Janus kinase (JAK) and receptor tyrosine kinases (RTKs) including receptors for insulin, insulin-like growth factor-1, Janus kinase 2 (Jak2), platelet derived growth factor, fibroblast growth factor and nerve growth factor. They function in glucose homeostasis, energy metabolism, hematopoesis and reproduction. Mutations in human SH2B orthologs are associated with metabolic disregulation and obesity. There are several SH2B members in mammals: SH2B1 (splice variants: SH2B1alpha, SH2B1beta, SH2B1gamma, and SH2B1delta), SH2B2 (APS) and SH2B3 (Lnk). They contain a PH domain, a SH2 domain, a proline rich region, multiple consensus sites for tyrosine and serine/threonine phosphorylation and a highly conserved c-Cbl recognition motif. These domains function as protein-protein interaction motifs which allows SH2B proteins to integrate and transduce intracellular signals from multiple signaling networks in the absence of intrinsic catalytic activity. SH2B proteins bind via their SH2 domains to phosphotyrosine residues within the intracellular tails of several activated RTKs thereby contributing to receptor activation. SH2B proteins have been shown to interact with insulin receptor substrates IRS1 and IRS2, Grb2, Shc and c-Cbl which may or may not require RTK-stimulated tyrosine phosphorylation of SH2B. positively and negatively regulating RTK signaling. Understanding the physiological functions of SH2B proteins in mammals has been complicated by the presence of multiple SH2B isoforms and conflicting data. Both SH2-Bbeta and APS associate with JAKs, but the former facilitates JAK/STAT signaling while the latter inhibits it. Lnk plays a role in cell growth and proliferation with mutations resulting in growth reduction, developmental delay and female sterility. Recently Lnk Drosophila has been shown to be an important regulator of the insulin/insulin-like growth factor (IGF)-1 signaling (IIS) pathway during growth. PH domains have diverse functions, but in general are involved in targeting proteins to the appropriate cellular location or in the interaction with a binding partner. They share little sequence conservation, but all have a common fold, which is electrostatically polarized. Less than 10% of PH domains bind phosphoinositide phosphates (PIPs) with high affinity and specificity. PH domains are distinguished from other PIP-binding domains by their specific high-affinity binding to PIPs with two vicinal phosphate groups: PtdIns(3,4)P2, PtdIns(4,5)P2 or PtdIns(3,4,5)P3 which results in targeting some PH domain proteins to the plasma membrane. A few display strong specificity in lipid binding. Any specificity is usually determined by loop regions or insertions in the N-terminus of the domain, which are not conserved across all PH domains. PH domains are found in cellular signaling proteins such as serine/threonine kinase, tyrosine kinases, regulators of G-proteins, endocytotic GTPases, adaptors, as well as cytoskeletal associated molecules and in lipid associated enzymes.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 24650177 197 ECRKEGTVNNLTPESLdQPTGSQKWEKCRLVLVKAVGG---YMLEFYTPHKATKPRSGVFCFLISEARETTALEMPDRLN 273
Cdd:cd01231   1 ECRKEGIVNYLSGEET-ASDGGPRWQKCRLVLVKAAGGegeYLLEFYVPPKSSKPKLGIFCSLIQEVRETTALEMPDNEN 79

                        90       100       110
                ....*....|....*....|....*....|....*
gi 24650177 274 TFVLKADNNMEYVIEAESAEEMRSWLATIRYCMRT 308
Cdd:cd01231  80 TFVLKVENSTEYIIEAGDEQQMRSWLAEIRECMSP 114

Src homology 2 domains; Src homology 2 domains bind phosphotyrosine-containing polypeptides via 2 surface pockets. Specificity is provided via interaction with residues that are distinct from the phosphotyrosine. Only a single occurrence of a SH2 domain has been found in S. cerevisiae.

                           10        20        30        40        50        60        70        80
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 24650177    441 PWFHGTLTRSEAARMVLHsdaAGHGYFLVRQSETRRGEFVLTFNFQGRAKHLRLTISEKGQCRVQ-HLWFPSIQEMLEHF 519
Cdd:smart00252   2 PWYHGFISREEAEKLLKN---EGDGDFLVRDSESSPGDYVLSVRVKGKVKHYRIRRNEDGKFYLEgGRKFPSLVELVEHY 78

                   ....*.
gi 24650177    520 RHNPIP 525
Cdd:smart00252  79 QKNSLG 84

Pleckstrin homology domain; Domain commonly found in eukaryotic signalling proteins. The domain family possesses multiple functions including the abilities to bind inositol phosphates, and various proteins. PH domains have been found to possess inserted domains (such as in PLC gamma, syntrophins) and to be inserted within other domains. Mutations in Brutons tyrosine kinase (Btk) within its PH domain cause X-linked agammaglobulinaemia (XLA) in patients. Point mutations cluster into the positively charged end of the molecule around the predicted binding site for phosphatidylinositol lipids.

                           10        20        30        40        50        60        70        80
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 24650177    215 PTGSQKWEKCRLVLVKAvggyMLEFYTPHKATKPRSGVFCFLISEA--RETTALEMPDRLNTFVLKADNNMEYVIEAESA 292
Cdd:smart00233  12 GGGKKSWKKRYFVLFNS----TLLYYKSKKDKKSYKPKGSIDLSGCtvREAPDPDSSKKPHCFEIKTSDRKTLLLQAESE 87

                           90
                   ....*....|....*
gi 24650177    293 EEMRSWLATIRYCMR 307
Cdd:smart00233  88 EEREKWVEALRKAIA 102

SH2B adapter protein 1, 2, and 3 Pleckstrin homology (PH) domain; SH2B family/APS proteins are a family of intracellular adaptor proteins that influences a variety of signaling pathways mediated by Janus kinase (JAK) and receptor tyrosine kinases (RTKs) including receptors for insulin, insulin-like growth factor-1, Janus kinase 2 (Jak2), platelet derived growth factor, fibroblast growth factor and nerve growth factor. They function in glucose homeostasis, energy metabolism, hematopoesis and reproduction. Mutations in human SH2B orthologs are associated with metabolic disregulation and obesity. There are several SH2B members in mammals: SH2B1 (splice variants: SH2B1alpha, SH2B1beta, SH2B1gamma, and SH2B1delta), SH2B2 (APS) and SH2B3 (Lnk). They contain a PH domain, a SH2 domain, a proline rich region, multiple consensus sites for tyrosine and serine/threonine phosphorylation and a highly conserved c-Cbl recognition motif. These domains function as protein-protein interaction motifs which allows SH2B proteins to integrate and transduce intracellular signals from multiple signaling networks in the absence of intrinsic catalytic activity. SH2B proteins bind via their SH2 domains to phosphotyrosine residues within the intracellular tails of several activated RTKs thereby contributing to receptor activation. SH2B proteins have been shown to interact with insulin receptor substrates IRS1 and IRS2, Grb2, Shc and c-Cbl which may or may not require RTK-stimulated tyrosine phosphorylation of SH2B. positively and negatively regulating RTK signaling. Understanding the physiological functions of SH2B proteins in mammals has been complicated by the presence of multiple SH2B isoforms and conflicting data. Both SH2-Bbeta and APS associate with JAKs, but the former facilitates JAK/STAT signaling while the latter inhibits it. Lnk plays a role in cell growth and proliferation with mutations resulting in growth reduction, developmental delay and female sterility. Recently Lnk Drosophila has been shown to be an important regulator of the insulin/insulin-like growth factor (IGF)-1 signaling (IIS) pathway during growth. PH domains have diverse functions, but in general are involved in targeting proteins to the appropriate cellular location or in the interaction with a binding partner. They share little sequence conservation, but all have a common fold, which is electrostatically polarized. Less than 10% of PH domains bind phosphoinositide phosphates (PIPs) with high affinity and specificity. PH domains are distinguished from other PIP-binding domains by their specific high-affinity binding to PIPs with two vicinal phosphate groups: PtdIns(3,4)P2, PtdIns(4,5)P2 or PtdIns(3,4,5)P3 which results in targeting some PH domain proteins to the plasma membrane. A few display strong specificity in lipid binding. Any specificity is usually determined by loop regions or insertions in the N-terminus of the domain, which are not conserved across all PH domains. PH domains are found in cellular signaling proteins such as serine/threonine kinase, tyrosine kinases, regulators of G-proteins, endocytotic GTPases, adaptors, as well as cytoskeletal associated molecules and in lipid associated enzymes.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 24650177 197 ECRKEGTVNNLTPESLdQPTGSQKWEKCRLVLVKAVGG---YMLEFYTPHKATKPRSGVFCFLISEARETTALEMPDRLN 273
Cdd:cd01231   1 ECRKEGIVNYLSGEET-ASDGGPRWQKCRLVLVKAAGGegeYLLEFYVPPKSSKPKLGIFCSLIQEVRETTALEMPDNEN 79

                        90       100       110
                ....*....|....*....|....*....|....*
gi 24650177 274 TFVLKADNNMEYVIEAESAEEMRSWLATIRYCMRT 308
Cdd:cd01231  80 TFVLKVENSTEYIIEAGDEQQMRSWLAEIRECMSP 114

Src homology 2 (SH2) domain found in SH2B adapter proteins (SH2B1, SH2B2, SH2B3); SH2B2 (APS), like other members of the SH2B adapter protein family, contains a pleckstrin homology domain, at least one dimerization domain, and a C-terminal SH2 domain which binds to phosphorylated tyrosines in a variety of tyrosine kinases. SH2B1 and SH2B2 function in signaling pathways found downstream of growth hormone receptor and receptor tyrosine kinases, including the insulin, insulin-like growth factor-I (IGF-I), platelet-derived growth factor (PDGF), nerve growth factor, hepatocyte growth factor, and fibroblast growth factor receptors. SH2B2beta, a new isoform of SH2B2, is an endogenous inhibitor of SH2B1 and/or SH2B2 (SH2B2alpha), negatively regulating insulin signaling and/or JAK2-mediated cellular responses. In general SH2 domains are involved in signal transduction. They typically bind pTyr-containing ligands via two surface pockets, a pTyr and hydrophobic binding pocket, allowing proteins with SH2 domains to localize to tyrosine phosphorylated sites.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 24650177 435 AEMSVFPWFHGTLTRSEAARMVLHSDAAGHGYFLVRQSETRRGEFVLTFNFQGRAKHLRLTISEKGQCRVQHLWFPSIQE 514
Cdd:cd10411   3 LELSDYPWFHGTLSRVKAAQLVLAGGPRSHGLFVIRQSETRPGEYVLTFNFQGKAKHLRLSLNGHGQCHVQHLWFQSVFD 82

                        90
                ....*....|....*
gi 24650177 515 MLEHFRHNPIPLESG 529
Cdd:cd10411  83 MLRHFHTHPIPLESG 97

Phenylalanine zipper; The phenylalanine zipper consists of aromatic side chains from ten phenylalanine residues that are stacked within a hydrophobic core. This zipper mediates dimerization of various proteins, such as APS and SH2-B/Lnk.

                          10        20        30        40        50
                  ....*....|....*....|....*....|....*....|....*....|....*....
gi 24650177    67 SWEEFCERHARVAASDFAKACITYINGNlpPEEARNIQHRSFAQKFVESFSAHYDTEFF 125
Cdd:pfam08916   1 GWKEFCELHARAAASDFARAFRRFVREN--PQYAAPLAHRDFSRKFAELFLEHFESEVK 57

Src homology 2 (SH2) domain; In general, SH2 domains are involved in signal transduction; they bind pTyr-containing polypeptide ligands via two surface pockets, a pTyr and hydrophobic binding pocket, allowing proteins with SH2 domains to localize to tyrosine phosphorylated sites. They are present in a wide array of proteins including: adaptor proteins (Nck1, Crk, Grb2), scaffolds (Slp76, Shc, Dapp1), kinases (Src, Syk, Fps, Tec), phosphatases (Shp-1, Shp-2), transcription factors (STAT1), Ras signaling molecules (Ras-Gap), ubiquitination factors (c-Cbl), cytoskeleton regulators (Tensin), signal regulators (SAP), and phospholipid second messengers (PLCgamma), amongst others.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 24650177 441 PWFHGTLTRSEAARMVLHSDaagHGYFLVRQSETRRGEFVLTFNFQ-GRAKHLRLTISEKGQCRV--QHLWFPSIQEMLE 517
Cdd:cd00173   1 PWFHGSISREEAERLLRGKP---DGTFLVRESSSEPGDYVLSVRSGdGKVKHYLIERNEGGYYLLggSGRTFPSLPELVE 77

                ..
gi 24650177 518 HF 519
Cdd:cd00173  78 HY 79

SH2 domain;

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....
gi 24650177   442 WFHGTLTRSEAARMVLHSDAAGHgyFLVRQSETRRGEFVLTFNFQGRAKHLR-LTISEKGQCRVQHLWFPSIQEMLEHF 519
Cdd:pfam00017   1 WYHGKISRQEAERLLLNGKPDGT--FLVRESESTPGGYTLSVRDDGKVKHYKiQSTDNGGYYISGGVKFSSLAELVEHY 77

N-terminal Src homology 2 (N-SH2) domain in Phospholipase C gamma; Phospholipase C gamma is a signaling molecule that is recruited to the C-terminal tail of the receptor upon autophosphorylation of a highly conserved tyrosine. PLCgamma is composed of a Pleckstrin homology (PH) domain followed by an elongation factor (EF) domain, 2 catalytic regions of PLC domains that flank 2 tandem SH2 domains (N-SH2, C-SH2), and ending with a SH3 domain and C2 domain. N-SH2 SH2 domain-mediated interactions represent a crucial step in transmembrane signaling by receptor tyrosine kinases. SH2 domains recognize phosphotyrosine (pY) in the context of particular sequence motifs in receptor phosphorylation sites. Both N-SH2 and C-SH2 have a very similar binding affinity to pY. But in growth factor stimulated cells these domains bind to different target proteins. N-SH2 binds to pY containing sites in the C-terminal tails of tyrosine kinases and other receptors. Recently it has been shown that this interaction is mediated by phosphorylation-independent interactions between a secondary binding site found exclusively on the N-SH2 domain and a region of the FGFR1 tyrosine kinase domain. This secondary site on the SH2 cooperates with the canonical pY site to regulate selectivity in mediating a specific cellular process. C-SH2 binds to an intramolecular site on PLCgamma itself which allows it to hydrolyze phosphatidylinositol-4,5-bisphosphate into diacylglycerol and inositol triphosphate. These then activate protein kinase C and release calcium. In general SH2 domains are involved in signal transduction. They typically bind pTyr-containing ligands via two surface pockets, a pTyr and hydrophobic binding pocket, allowing proteins with SH2 domains to localize to tyrosine phosphorylated sites.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 24650177 441 PWFHGTLT--RSEAARMVLHSDAAGHGYFLVRQSETRRGEFVLTFNFQGRAKHLRL-TISEKGQCR---VQHLWFPSIQE 514
Cdd:cd10341   5 PWFHGKLGdgRDEAEKLLLEYCEGGDGTFLVRESETFVGDYTLSFWRNGKVQHCRIrSRQENGEKKyylTDNLVFDSLYE 84

                        90
                ....*....|
gi 24650177 515 MLEHFRHNPI 524
Cdd:cd10341  85 LIDYYRQNPL 94

Src homology 2 (SH2) domain found in Src-related kinase lacking C-terminal regulatory tyrosine and N-terminal myristoylation sites (srm); Srm is a nonreceptor protein kinase that has two SH2 domains, a SH3 domain, and a kinase domain with a tyrosine residue for autophosphorylation. However it lacks an N-terminal glycine for myristoylation and a C-terminal tyrosine which suppresses kinase activity when phosphorylated. Srm is most similar to members of the Tec family who other members include: Tec, Btk/Emb, and Itk/Tsk/Emt. However Srm differs in its N-terminal unique domain it being much smaller than in the Tec family and is closer to Src. Srm is thought to be a new family of nonreceptor tyrosine kinases that may be redundant in function. In general SH2 domains are involved in signal transduction. They typically bind pTyr-containing ligands via two surface pockets, a pTyr and hydrophobic binding pocket, allowing proteins with SH2 domains to localize to tyrosine phosphorylated sites.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 24650177 441 PWFHGTLTRSEAARMVLhSDAAGHGYFLVRQSETRRGEFVLTFNFQGRAKHLRLTISEKGQCRVQ--HLwFPSIQEMLEH 518
Cdd:cd10360   1 PWYFSGISRTQAQQLLL-SPPNEPGAFLIRPSESSLGGYSLSVRAQAKVCHYRICMAPSGSLYLQkgRL-FPGLEELLAY 78

                .
gi 24650177 519 F 519
Cdd:cd10360  79 Y 79

C-terminal Src homology 2 (SH2) domain found in Ras GTPase-activating protein 1 (GAP); RasGAP is part of the GAP1 family of GTPase-activating proteins. The protein is located in the cytoplasm and stimulates the GTPase activity of normal RAS p21, but not its oncogenic counterpart. Acting as a suppressor of RAS function, the protein enhances the weak intrinsic GTPase activity of RAS proteins resulting in RAS inactivation, thereby allowing control of cellular proliferation and differentiation. Mutations leading to changes in the binding sites of either protein are associated with basal cell carcinomas. Alternative splicing results in two isoforms. The shorter isoform which lacks the N-terminal hydrophobic region, has the same activity, and is expressed in placental tissues. In general longer isoform contains 2 SH2 domains, a SH3 domain, a pleckstrin homology (PH) domain, and a calcium-dependent phospholipid-binding C2 domain. The C-terminus contains the catalytic domain of RasGap which catalyzes the activation of Ras by hydrolyzing GTP-bound active Ras into an inactive GDP-bound form of Ras. This model contains the C-terminal SH2 domain. In general SH2 domains are involved in signal transduction. They typically bind pTyr-containing ligands via two surface pockets, a pTyr and hydrophobic binding pocket, allowing proteins with SH2 domains to localize to tyrosine phosphorylated sites.

                        10        20        30        40        50        60        70
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....
gi 24650177 441 PWFHGTLTRSEAARMVLHsdAAGHGYFLVRQSETRRGEFVLTFNFQGRAKHLRLTISEKGQCRVQHLWFPSIQEMLEHF 519
Cdd:cd10354   1 IWFHGKISREEAYNMLVK--VGGPGSFLVRESDNTPGDYSLSFRVNEGIKHFKIIPTGNNQFMMGGRYFSSLDDVIDRY 77

Src homology 2 (SH2) domain found in the Nck family; Nck proteins are adaptors that modulate actin cytoskeleton dynamics by linking proline-rich effector molecules to tyrosine kinases or phosphorylated signaling intermediates. There are two members known in this family: Nck1 (Nckalpha) and Nck2 (Nckbeta and Growth factor receptor-bound protein 4 (Grb4)). They are characterized by having 3 SH3 domains and a C-terminal SH2 domain. Nck1 and Nck2 have overlapping functions as determined by gene knockouts. Both bind receptor tyrosine kinases and other tyrosine-phosphorylated proteins through their SH2 domains. In addition they also bind distinct targets. Neuronal signaling proteins: EphrinB1, EphrinB2, and Disabled-1 (Dab-1) all bind to Nck-2 exclusively. And in the case of PDGFR, Tyr(P)751 binds to Nck1 while Tyr(P)1009 binds to Nck2. Nck1 and Nck2 have a role in the infection process of enteropathogenic Escherichia coli (EPEC). Their SH3 domains are involved in recruiting and activating the N-WASP/Arp2/3 complex inducing actin polymerization resulting in the production of pedestals, dynamic bacteria-presenting protrusions of the plasma membrane. A similar thing occurs in the vaccinia virus where motile plasma membrane projections are formed beneath the virus. Recently it has been shown that the SH2 domains of both Nck1 and Nck2 bind the G-protein coupled receptor kinase-interacting protein 1 (GIT1) in a phosphorylation-dependent manner. In general SH2 domains are involved in signal transduction. They typically bind pTyr-containing ligands via two surface pockets, a pTyr and hydrophobic binding pocket, allowing proteins with SH2 domains to localize to tyrosine phosphorylated sites.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 24650177 441 PWFHGTLTRSEAaRMVLhsDAAGH-GYFLVRQSETRRGEFVLTFNFQGRAKHLRLTISEKGQCRVQHLwFPSIQEMLEHF 519
Cdd:cd09943   2 PWYYGRITRHQA-ETLL--NEHGHeGDFLIRDSESNPGDYSVSLKAPGRNKHFKVQVVDNVYCIGQRK-FHTMDELVEHY 77

                ....*
gi 24650177 520 RHNPI 524
Cdd:cd09943  78 KKAPI 82

Src homology 2 domain found in Growth factor receptor-bound protein 2 (Grb2) and similar proteins; The adaptor proteins here include homologs Grb2 in humans, Sex muscle abnormal protein 5 (Sem-5) in Caenorhabditis elegans, and Downstream of receptor kinase (drk) in Drosophila melanogaster. They are composed of one SH2 and two SH3 domains. Grb2/Sem-5/drk regulates the Ras pathway by linking the tyrosine kinases to the Ras guanine nucleotide releasing protein Sos, which converts Ras to the active GTP-bound state. The SH2 domain of Grb2/Sem-5/drk binds class II phosphotyrosyl peptides while its SH3 domain binds to Sos and Sos-derived, proline-rich peptides. Besides it function in Ras signaling, Grb2 is also thought to play a role in apoptosis. Unlike most SH2 structures in which the peptide binds in an extended conformation (such that the +3 peptide residue occupies a hydrophobic pocket in the protein, conferring a modest degree of selectivity), Grb2 forms several hydrogen bonds via main chain atoms with the side chain of +2 Asn. In general SH2 domains are involved in signal transduction. They typically bind pTyr-containing ligands via two surface pockets, a pTyr and hydrophobic binding pocket, allowing proteins with SH2 domains to localize to tyrosine phosphorylated sites.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 24650177 441 PWFHGTLTRSEAARMVlhSDAAGHGYFLVRQSETRRGEFVLTFNFQGRAKHLRLTISEKGQcrvQHLW---FPSIQEMLE 517
Cdd:cd09941   4 PWFHGKISRAEAEEIL--MNQRPDGAFLIRESESSPGDFSLSVKFGNDVQHFKVLRDGAGK---YFLWvvkFNSLNELVD 78

                ....*..
gi 24650177 518 HFRHNPI 524
Cdd:cd09941  79 YHRTTSV 85

Src homology 2 (SH2) domain found in the growth factor receptor bound, subclass 7 (Grb7) proteins; The Grb family binds to the epidermal growth factor receptor (EGFR, erbB1) via their SH2 domains. There are 3 members of the Grb7 family of proteins: Grb7, Grb10, and Grb14. They are composed of an N-terminal Proline-rich domain, a Ras Associating-like (RA) domain, a Pleckstrin Homology (PH) domain, a phosphotyrosine interaction region (PIR, BPS) and a C-terminal SH2 domain. The SH2 domains of Grb7, Grb10 and Grb14 preferentially bind to a different RTK. Grb7 binds strongly to the erbB2 receptor, unlike Grb10 and Grb14 which bind weakly to it. Grb14 binds to Fibroblast Growth Factor Receptor (FGFR). Grb10 has been shown to interact with many different proteins, including the insulin and IGF1 receptors, platelet-derived growth factor (PDGF) receptor-beta, Ret, Kit, Raf1 and MEK1, and Nedd4. Grb7 family proteins are phosphorylated on serine/threonine as well as tyrosine residues. In general SH2 domains are involved in signal transduction. They typically bind pTyr-containing ligands via two surface pockets, a pTyr and hydrophobic binding pocket, allowing proteins with SH2 domains to localize to tyrosine phosphorylated sites.

                        10        20        30        40        50        60
                ....*....|....*....|....*....|....*....|....*....|....*....|..
gi 24650177 441 PWFHGTLTRSEAARmVLHSDAAGHGYFLVRQSETRRGEFVLTFNFQGRAKHLRLTISEKGQC 502
Cdd:cd09944   6 PWFHGGISRDEAAR-LIRQQGLVDGVFLVRESQSNPGAFVLSLKHGQKIKHYQIIPIEDEGQ 66

Src homology 2 (SH2) domain found in Abelson murine lymphosarcoma virus (ABL) proteins; ABL-family proteins are highly conserved tyrosine kinases. Each ABL protein contains an SH3-SH2-TK (Src homology 3-Src homology 2-tyrosine kinase) domain cassette, which confers autoregulated kinase activity and is common among nonreceptor tyrosine kinases. Several types of posttranslational modifications control ABL catalytic activity, subcellular localization, and stability, with consequences for both cytoplasmic and nuclear ABL functions. Binding partners provide additional regulation of ABL catalytic activity, substrate specificity, and downstream signaling. By combining this cassette with actin-binding and -bundling domain, ABL proteins are capable of connecting phosphoregulation with actin-filament reorganization. Vertebrate paralogs, ABL1 and ABL2, have evolved to perform specialized functions. ABL1 includes nuclear localization signals and a DNA binding domain which is used to mediate DNA damage-repair functions, while ABL2 has additional binding capacity for actin and for microtubules to enhance its cytoskeletal remodeling functions. SH2 is involved in several autoinhibitory mechanism that constrain the enzymatic activity of the ABL-family kinases. In one mechanism SH2 and SH3 cradle the kinase domain while a cap sequence stabilizes the inactive conformation resulting in a locked inactive state. Another involves phosphatidylinositol 4,5-bisphosphate (PIP2) which binds the SH2 domain through residues normally required for phosphotyrosine binding in the linker segment between the SH2 and kinase domains. The SH2 domain contributes to ABL catalytic activity and target site specificity. It is thought that the ABL catalytic site and SH2 pocket have coevolved to recognize the same sequences. Recent work now supports a hierarchical processivity model in which the substrate target site most compatible with ABL kinase domain preferences is phosphorylated with greatest efficiency. If this site is compatible with the ABL SH2 domain specificity, it will then reposition and dock in the SH2 pocket. This mechanism also explains how ABL kinases phosphorylates poor targets on the same substrate if they are properly positioned and how relatively poor substrate proteins might be recruited to ABL through a complex with strong substrates that can also dock with the SH2 pocket. In general SH2 domains are involved in signal transduction. They typically bind pTyr-containing ligands via two surface pockets, a pTyr and hydrophobic binding pocket, allowing proteins with SH2 domains to localize to tyrosine phosphorylated sites.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 24650177 440 FPWFHGTLTRsEAARMVLHSDAagHGYFLVRQSETRRGEFVLTFNFQGRAKHLRLTISEKGQCRV-QHLWFPSIQEMLEH 518
Cdd:cd09935   3 HSWYHGPISR-NAAEYLLSSGI--NGSFLVRESESSPGQYSISLRYDGRVYHYRISEDSDGKVYVtQEHRFNTLAELVHH 79

                ....*
gi 24650177 519 FRHNP 523
Cdd:cd09935  80 HSKNA 84

Src homology 2 (SH2) domain found in the Vav family; Vav proteins are involved in several processes that require cytoskeletal reorganization, such as the formation of the immunological synapse (IS), phagocytosis, platelet aggregation, spreading, and transformation. Vavs function as guanine nucleotide exchange factors (GEFs) for the Rho/Rac family of GTPases. Vav family members have several conserved motifs/domains including: a leucine-rich region, a leucine-zipper, a calponin homology (CH) domain, an acidic domain, a Dbl-homology (DH) domain, a pleckstrin homology (PH) domain, a cysteine-rich domain, 2 SH3 domains, a proline-rich region, and a SH2 domain. Vavs are the only known Rho GEFs that have both the DH/PH motifs and SH2/SH3 domains in the same protein. The leucine-rich helix-loop-helix (HLH) domain is thought to be involved in protein heterodimerization with other HLH proteins and it may function as a negative regulator by forming inactive heterodimers. The CH domain is usually involved in the association with filamentous actin, but in Vav it controls NFAT stimulation, Ca2+ mobilization, and its transforming activity. Acidic domains are involved in protein-protein interactions and contain regulatory tyrosines. The DH domain is a GDP-GTP exchange factor on Rho/Rac GTPases. The PH domain in involved in interactions with GTP-binding proteins, lipids and/or phosphorylated serine/threonine residues. The SH3 domain is involved in localization of proteins to specific sites within the cell interacting with protein with proline-rich sequences. The SH2 domain mediates a high affinity interaction with tyrosine phosphorylated proteins. There are three Vav mammalian family members: Vav1 which is expressed in the hematopoietic system, Vav2 and Vav3 are more ubiquitously expressed. The members here include insect and amphibian Vavs. In general SH2 domains are involved in signal transduction. They typically bind pTyr-containing ligands via two surface pockets, a pTyr and hydrophobic binding pocket, allowing proteins with SH2 domains to localize to tyrosine phosphorylated sites.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 24650177 436 EMSVFPWFHGTLTRSEAA-RMVLHSDaaghGYFLVRQSETRRGEFVLTFNFQGRAKHLRLTISEKGQCRV-QHLWFPSIQ 513
Cdd:cd09940   1 DLSEFLWFVGEMERDTAEnRLENRPD----GTYLVRVRPQGETQYALSIKYNGDVKHMKIEQRSDGLYYLsESRHFKSLV 76

                ....*....
gi 24650177 514 EMLEHFRHN 522
Cdd:cd09940  77 ELVNYYERN 85

Pleckstrin homology domain; Domain commonly found in eukaryotic signalling proteins. The domain family possesses multiple functions including the abilities to bind inositol phosphates, and various proteins. PH domains have been found to possess inserted domains (such as in PLC gamma, syntrophins) and to be inserted within other domains. Mutations in Brutons tyrosine kinase (Btk) within its PH domain cause X-linked agammaglobulinaemia (XLA) in patients. Point mutations cluster into the positively charged end of the molecule around the predicted binding site for phosphatidylinositol lipids.

                           10        20        30        40        50        60        70        80
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 24650177    215 PTGSQKWEKCRLVLVKAvggyMLEFYTPHKATKPRSGVFCFLISEA--RETTALEMPDRLNTFVLKADNNMEYVIEAESA 292
Cdd:smart00233  12 GGGKKSWKKRYFVLFNS----TLLYYKSKKDKKSYKPKGSIDLSGCtvREAPDPDSSKKPHCFEIKTSDRKTLLLQAESE 87

                           90
                   ....*....|....*
gi 24650177    293 EEMRSWLATIRYCMR 307
Cdd:smart00233  88 EEREKWVEALRKAIA 102

Src homology 2 domain found in SH2 domain-containing adapter proteins D (SHD); The expression of SHD is restricted to the brain. SHD may be a physiological substrate of c-Abl and may function as an adapter protein in the central nervous system. It is also thought to be involved in apoptotic regulation. SHD contains five YXXP motifs, a substrate sequence preferred by Abl tyrosine kinases, in addition to a poly-proline rich region and a C-terminal SH2 domain. In general SH2 domains are involved in signal transduction. They typically bind pTyr-containing ligands via two surface pockets, a pTyr and hydrophobic binding pocket, allowing proteins with SH2 domains to localize to tyrosine phosphorylated sites.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 24650177 441 PWFHGTLTRSEAARMVlhsDAAGHGYFLVRQSETRRGEFVLTFNFQGRAKHLRLTISEKGQCRV-QHLW-FPSIQEMLEH 518
Cdd:cd10390   2 PWFHGPLSRADAENLL---SLCKEGSYLVRLSETRPQDCSLSLRSSQGFLHLKFARTRENQVVLgQHSGpFPSVPELVLH 78

                ....*....
gi 24650177 519 FRHNPIPLE 527
Cdd:cd10390  79 YSSRPLPVQ 87

Src homology 2 domain found in hematopoietic SH2 (HSH2) protein; HSH2 is thought to function as an adapter protein involved in tyrosine kinase signaling. It may also be involved in regulating cytokine signaling and cytoskeletal reorganization in hematopoietic cells. HSH2 contains several putative protein-binding motifs, SH3-binding proline-rich regions, and phosphotyrosine sites, but lacks enzymatic motifs. HSH2 was found to interact with cytokine-regulated tyrosine kinase c-FES and an activated Cdc42-associated tyrosine kinase ACK1. HSH2 binds c-FES through both its C-terminal region and its N-terminal region including the SH2 domain and binds ACK1 via its N-terminal proline-rich region. Both kinases bound and tyrosine-phosphorylated HSH2 in mammalian cells. In general SH2 domains are involved in signal transduction. They typically bind pTyr-containing ligands via two surface pockets, a pTyr and hydrophobic binding pocket, allowing proteins with SH2 domains to localize to tyrosine phosphorylated sites.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 24650177 436 EMSVFP-WFHGTLTRsEAARMVLHSDAAghGYFLVRQSETRRGeFVLTFNFQGRAKHLRLTISEKGQCRV--QHLWFPSI 512
Cdd:cd09946   2 AQDGVPeWFHGAISR-EAAENMLESQPL--GSFLIRVSHSHVG-YTLSYKAQSSCRHFMVKLLDDGTFMIpgEKVAHTSL 77

                        90
                ....*....|..
gi 24650177 513 QEMLEHFRHNPI 524
Cdd:cd09946  78 HALVTFHQQKPI 89

Src homology 2 (SH2) domain found in the Fyn-related kinase (Frk); Frk is a member of the Src non-receptor type tyrosine kinase family of proteins. The Frk subfamily is composed of Frk/Rak and Iyk/Bsk/Gst. It is expressed primarily epithelial cells. Frk is a nuclear protein and may function during G1 and S phase of the cell cycle and suppress growth. Unlike the other Src members it lacks a glycine at position 2 of SH4 which is important for addition of a myristic acid moiety that is involved in targeting Src PTKs to cellular membranes. FRK and SHB exert similar effects when overexpressed in rat phaeochromocytoma (PC12) and beta-cells, where both induce PC12 cell differentiation and beta-cell proliferation. Under conditions that cause beta-cell degeneration these proteins augment beta-cell apoptosis. The FRK-SHB responses involve FAK and insulin receptor substrates (IRS) -1 and -2. Frk has been demonstrated to interact with retinoblastoma protein. Frk regulates PTEN protein stability by phosphorylating PTEN, which in turn prevents PTEN degradation. Frk also plays a role in regulation of embryonal pancreatic beta cell formation. Frk has a unique N-terminal domain, an SH3 domain, an SH2 domain, a kinase domain and a regulatory tail, as do the other members of the family. Like the other members of the Src family the SH2 domain in addition to binding the target, also plays an autoinhibitory role by binding to its activation loop. The tryosine involved is at the same site as the tyrosine involved in the autophosphorylation of Src. In general SH2 domains are involved in signal transduction. They typically bind pTyr-containing ligands via two surface pockets, a pTyr and hydrophobic binding pocket, allowing proteins with SH2 domains to localize to tyrosine phosphorylated sites.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 24650177 441 PWFHGTLTRSEAARMVLHSDAAGhGYFLVRQSETRRGEFVLTFNFQGRAKHLRLTISEKGQCRVQHL-WFPSIQEMLEHF 519
Cdd:cd10369   4 PWFFGAIKRADAEKQLLYSENQT-GAFLIRESESQKGEFSLSVLDGGVVKHYRIRRLDEGGFFLTRRkTFSTLNEFVNYY 82

                ...
gi 24650177 520 RHN 522
Cdd:cd10369  83 TTT 85

Src homology 2 (SH2) domain found in B-cell linker (BLNK) protein and SH2 domain-containing leukocyte protein of 76 kDa (SLP-76); BLNK (also known as SLP-65 or BASH) is an important adaptor protein expressed in B-lineage cells. BLNK consists of a N-terminal sterile alpha motif (SAM) domain and a C-terminal SH2 domain. BLNK is a cytoplasmic protein, but a part of it is bound to the plasma membrane through an N-terminal leucine zipper motif and transiently bound to a cytoplasmic domain of Iga through its C-terminal SH2 domain upon B cell antigen receptor (BCR)-stimulation. A non-ITAM phosphotyrosine in Iga is necessary for the binding with the BLNK SH2 domain and/or for normal BLNK function in signaling and B cell activation. Upon phosphorylation BLNK binds Btk and PLCgamma2 through their SH2 domains and mediates PLCgamma2 activation by Btk. BLNK also binds other signaling molecules such as Vav, Grb2, Syk, and HPK1. BLNK has been shown to be necessary for BCR-mediated Ca2+ mobilization, for the activation of mitogen-activated protein kinases such as ERK, JNK, and p38 in a chicken B cell line DT40, and for activation of transcription factors such as NF-AT and NF-kappaB in human or mouse B cells. BLNK is involved in B cell development, B cell survival, activation, proliferation, and T-independent immune responses. BLNK is structurally homologous to SLP-76. SLP-76 and (linker for activation of T cells) LAT are adaptor/linker proteins in T cell antigen receptor activation and T cell development. BLNK interacts with many downstream signaling proteins that interact directly with both SLP-76 and LAT. New data suggest functional complementation of SLP-76 and LAT in T cell antigen receptor function with BLNK in BCR function. In general SH2 domains are involved in signal transduction. They typically bind pTyr-containing ligands via two surface pockets, a pTyr and hydrophobic binding pocket, allowing proteins with SH2 domains to localize to tyrosine phosphorylated sites.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 24650177 435 AEMSVFPWFHGTLTRSEAARMVLHSDAagHGYFLVRQSETRRGE--FVL-------TFN----FQGRAKHLRLTISEKGQ 501
Cdd:cd09929   6 ADLLPKEWYAGNIDRKEAEEALRRSNK--DGTFLVRDSSGKDSSqpYTLmvlyndkVYNiqirFLENTRQYALGTGLRGE 83

                        90       100
                ....*....|....*....|....*
gi 24650177 502 CRvqhlwFPSIQEMLEHFRHNPIPL 526
Cdd:cd09929  84 ET-----FSSVAEIIEHHQKTPLLL 103

Src homology 2 (SH2) domain found in B lymphoid kinase (Blk); Blk is a member of the Src non-receptor type tyrosine kinase family of proteins. Blk is expressed in the B-cells. Unlike most other Src members Blk lacks cysteine residues in the SH4 domain that undergo palmitylation. Blk is required for the development of IL-17-producing gamma-delta T cells. Furthermore, Blk is expressed in lymphoid precursors and, in this capacity, plays a role in regulating thymus cellularity during ontogeny. Blk has a unique N-terminal domain, an SH3 domain, an SH2 domain, a kinase domain and a regulatory tail, as do the other members of the family. In general SH2 domains are involved in signal transduction. They typically bind pTyr-containing ligands via two surface pockets, a pTyr and hydrophobic binding pocket, allowing proteins with SH2 domains to localize to tyrosine phosphorylated sites.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 24650177 442 WFHGTLTRSEAARMVLhSDAAGHGYFLVRQSETRRGEFVLT---FNFQGRA-KHLRL-TISEKGQCRVQHLWFPSIQEML 516
Cdd:cd10371   5 WFFRTISRKDAERQLL-APMNKAGSFLIRESESNKGAFSLSvkdVTTQGEVvKHYKIrSLDNGGYYISPRITFPTLQALV 83

                ...
gi 24650177 517 EHF 519
Cdd:cd10371  84 QHY 86

Src homology 2 domain found in the SH2 domain containing protein 2A and 7 (SH2D2A and SH2D7); SH2D2A and SH7 both contain a single SH2 domain. In general SH2 domains are involved in signal transduction. They typically bind pTyr-containing ligands via two surface pockets, a pTyr and hydrophobic binding pocket, allowing proteins with SH2 domains to localize to tyrosine phosphorylated sites.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 24650177 441 PWFHGTLTRSEAARMVlhSDAAgHGYFLVRQSETRRGeFVLTFNFQGRAKHLRLTiSEKGQCRV---QHLWFPSIQEMLE 517
Cdd:cd10349   1 AWFHGFITRREAERLL--EPKP-QGCYLVRFSESAVT-FVLSYRSRTCCRHFLLA-QLRDGRHVvlgEDSAHARLQDLLL 75

                ..
gi 24650177 518 HF 519
Cdd:cd10349  76 HY 77

Src homology 2 (SH2) domain found in the Vav1 proteins; Proto-oncogene vav is a member of the Dbl family of guanine nucleotide exchange factors (GEF) for the Rho family of GTP binding proteins. All vavs are activated by tyrosine phosphorylation leading to their activation. There are three Vav mammalian family members: Vav1 which is expressed in the hematopoietic system, and Vav2 and Vav3 are more ubiquitously expressed. Vav1 plays a role in T-cell and B-cell development and activation. It has been identified as the specific binding partner of Nef proteins from HIV-1, resulting in morphological changes, cytoskeletal rearrangements, and the JNK/SAPK signaling cascade, leading to increased levels of viral transcription and replication. Vav1 has been shown to interact with Ku70, PLCG1, Lymphocyte cytosolic protein 2, Janus kinase 2, SIAH2, S100B, Abl gene, ARHGDIB, SHB, PIK3R1, PRKCQ, Grb2, MAPK1, Syk, Linker of activated T cells, Cbl gene and EZH2. Vav proteins are involved in several processes that require cytoskeletal reorganization, such as the formation of the immunological synapse (IS), phagocytosis, platelet aggregation, spreading, and transformation. Vavs function as guanine nucleotide exchange factors (GEFs) for the Rho/Rac family of GTPases. Vav family members have several conserved motifs/domains including: a leucine-rich region, a leucine-zipper, a calponin homology (CH) domain, an acidic domain, a Dbl-homology (DH) domain, a pleckstrin homology (PH) domain, a cysteine-rich domain, 2 SH3 domains, a proline-rich region, and a SH2 domain. Vavs are the only known Rho GEFs that have both the DH/PH motifs and SH2/SH3 domains in the same protein. The leucine-rich helix-loop-helix (HLH) domain is thought to be involved in protein heterodimerization with other HLH proteins and it may function as a negative regulator by forming inactive heterodimers. The CH domain is usually involved in the association with filamentous actin, but in Vav it controls NFAT stimulation, Ca2+ mobilization, and its transforming activity. Acidic domains are involved in protein-protein interactions and contain regulatory tyrosines. The DH domain is a GDP-GTP exchange factor on Rho/Rac GTPases. The PH domain in involved in interactions with GTP-binding proteins, lipids and/or phosphorylated serine/threonine residues. The SH3 domain is involved in localization of proteins to specific sites within the cell interacting with protein with proline-rich sequences. The SH2 domain mediates a high affinity interaction with tyrosine phosphorylated proteins. In general SH2 domains are involved in signal transduction. They typically bind pTyr-containing ligands via two surface pockets, a pTyr and hydrophobic binding pocket, allowing proteins with SH2 domains to localize to tyrosine phosphorylated sites.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 24650177 436 EMSVFPWFHGTLTRSEAARMVLH-SDaaghGYFLVRQSETRRGEFVLTFNFQGRAKHLRLTISEkGQCRV-QHLWFPSIQ 513
Cdd:cd10405   1 DLSVHLWYAGPMERAGAESILANrSD----GTYLVRQRVKDAAEFAISIKYNVEVKHIKIMTAE-GLYRItEKKAFRGLT 75

                        90
                ....*....|.
gi 24650177 514 EMLEHFRHNPI 524
Cdd:cd10405  76 ELVEFYQQNSL 86

Src homology 2 (SH2) domain in lymphocyte cell kinase (Lck); Lck is a member of the Src non-receptor type tyrosine kinase family of proteins. It is expressed in the brain, T-cells, and NK cells. The unique domain of Lck mediates its interaction with two T-cell surface molecules, CD4 and CD8. It associates with their cytoplasmic tails on CD4 T helper cells and CD8 cytotoxic T cells to assist signaling from the T cell receptor (TCR) complex. When the T cell receptor is engaged by the specific antigen presented by MHC, Lck phosphorylase the intracellular chains of the CD3 and zeta-chains of the TCR complex, allowing ZAP-70 to bind them. Lck then phosphorylates and activates ZAP-70, which in turn phosphorylates Linker of Activated T cells (LAT), a transmembrane protein that serves as a docking site for proteins including: Shc-Grb2-SOS, PI3K, and phospholipase C (PLC). The tyrosine phosphorylation cascade culminates in the intracellular mobilization of a calcium ions and activation of important signaling cascades within the lymphocyte, including the Ras-MEK-ERK pathway, which goes on to activate certain transcription factors such as NFAT, NF-kappaB, and AP-1. These transcription factors regulate the production cytokines such as Interleukin-2 that promote long-term proliferation and differentiation of the activated lymphocytes. The N-terminal tail of Lck is myristoylated and palmitoylated and it tethers the protein to the plasma membrane of the cell. Lck also contains a SH3 domain, a SH2 domain, and a C-terminal tyrosine kinase domain. Lck has 2 phosphorylation sites, the first an autophosphorylation site that is linked to activation of the protein and the second which is phosphorylated by Csk, which inhibits it. Lck is also inhibited by SHP-1 dephosphorylation and by Cbl ubiquitin ligase, which is part of the ubiquitin-mediated pathway. In general SH2 domains are involved in signal transduction. They typically bind pTyr-containing ligands via two surface pockets, a pTyr and hydrophobic binding pocket, allowing proteins with SH2 domains to localize to tyrosine phosphorylated sites.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 24650177 441 PWFHGTLTRSEAARMVLhsdAAG--HGYFLVRQSETRRGEFVLTF----NFQGRA-KHLRLTISEKGQCRVQ-HLWFPSI 512
Cdd:cd10362   4 PWFFKNLSRNDAERQLL---APGntHGSFLIRESETTAGSFSLSVrdfdQNQGEVvKHYKIRNLDNGGFYISpRITFPGL 80

                ....*..
gi 24650177 513 QEMLEHF 519
Cdd:cd10362  81 HELVRHY 87

Src homology 2 domain found in dual adaptor for phosphotyrosine and 3-phosphoinositides ( DAPP1)/B lymphocyte adaptor molecule of 32 kDa (Bam32)-like proteins; DAPP1/Bam32 contains a putative myristoylation site at its N-terminus, followed by a SH2 domain, and a pleckstrin homology (PH) domain at its C-terminus. DAPP1 could potentially be recruited to the cell membrane by any of these domains. Its putative myristoylation site could facilitate the interaction of DAPP1 with the lipid bilayer. Its SH2 domain may also interact with phosphotyrosine residues on membrane-associated proteins such as activated tyrosine kinase receptors. And finally its PH domain exhibits a high-affinity interaction with the PtdIns(3,4,5)P(3) PtdIns(3,4)P(2) second messengers produced at the cell membrane following the activation of PI 3-kinases. DAPP1 is thought to interact with both tyrosine phosphorylated proteins and 3-phosphoinositides and therefore may play a role in regulating the location and/or activity of such proteins(s) in response to agonists that elevate PtdIns(3,4,5)P(3) and PtdIns(3,4)P(2). This protein is likely to play an important role in triggering signal transduction pathways that lie downstream from receptor tyrosine kinases and PI 3-kinase. It is likely that DAPP1 functions as an adaptor to recruit other proteins to the plasma membrane in response to extracellular signals. In general SH2 domains are involved in signal transduction. They typically bind pTyr-containing ligands via two surface pockets, a pTyr and hydrophobic binding pocket, allowing proteins with SH2 domains to localize to tyrosine phosphorylated sites.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 24650177 436 EMSVFPWFHGTLTRSEAARMVLHSDAAGHgyFLVRQSETRRGEFVLTFNFQGRAKHLRLTISEKGQcRVQHLWFPSIQEM 515
Cdd:cd10355   2 LLQSLGWYHGNLTRHAAEALLLSNGVDGS--YLLRNSNEGTGLFSLSVRAKDSVKHFHVEYTGYSF-KFGFNEFSSLQDF 78

                ....*....
gi 24650177 516 LEHFRHNPI 524
Cdd:cd10355  79 VKHFANQPL 87

Pleckstrin homology (PH) domain; PH domains have diverse functions, but in general are involved in targeting proteins to the appropriate cellular location or in the interaction with a binding partner. They share little sequence conservation, but all have a common fold, which is electrostatically polarized. Less than 10% of PH domains bind phosphoinositide phosphates (PIPs) with high affinity and specificity. PH domains are distinguished from other PIP-binding domains by their specific high-affinity binding to PIPs with two vicinal phosphate groups: PtdIns(3,4)P2, PtdIns(4,5)P2 or PtdIns(3,4,5)P3 which results in targeting some PH domain proteins to the plasma membrane. A few display strong specificity in lipid binding. Any specificity is usually determined by loop regions or insertions in the N-terminus of the domain, which are not conserved across all PH domains. PH domains are found in cellular signaling proteins such as serine/threonine kinase, tyrosine kinases, regulators of G-proteins, endocytotic GTPases, adaptors, as well as cytoskeletal associated molecules and in lipid associated enzymes.

                        10        20        30        40        50        60        70        80
                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 24650177 220 KWEKCRLVLVKAVggymLEFYTPHKATKPRSGVFCFLISEARETTALEmPDRLNTFVLKADNNMEYVIEAESAEEMRSWL 299
Cdd:cd00821  15 SWKKRWFVLFEGV----LLYYKSKKDSSYKPKGSIPLSGILEVEEVSP-KERPHCFELVTPDGRTYYLQADSEEERQEWL 89

                ...
gi 24650177 300 ATI 302
Cdd:cd00821  90 KAL 92

Src homology 2 (SH2) domain found in SH2-containing inositol-5'-phosphatase (SHIP) and SLAM-associated protein (SAP); The SH2-containing inositol-5'-phosphatase, SHIP (also called SHIP1/SHIP1a), is a hematopoietic-restricted phosphatidylinositide phosphatase that translocates to the plasma membrane after extracellular stimulation and hydrolyzes the phosphatidylinositol-3-kinase (PI3K)-generated second messenger PI-3,4,5-P3 (PIP3) to PI-3,4-P2. As a result, SHIP dampens down PIP3 mediated signaling and represses the proliferation, differentiation, survival, activation, and migration of hematopoietic cells. PIP3 recruits lipid-binding pleckstrin homology(PH) domain-containing proteins to the inner wall of the plasma membrane and activates them. PH domain-containing downstream effectors include the survival/proliferation enhancing serine/threonine kinase, Akt (protein kinase B), the tyrosine kinase, Btk, the regulator of protein translation, S6K, and the Rac and cdc42 guanine nucleotide exchange factor, Vav. SHIP is believed to act as a tumor suppressor during leukemogenesis and lymphomagenesis, and may play a role in activating the immune system to combat cancer. SHIP contains an N-terminal SH2 domain, a centrally located phosphatase domain that specifically hydrolyzes the 5'-phosphate from PIP3, PI-4,5-P2 and inositol-1,3,4,5- tetrakisphosphate (IP4), a C2 domain, that is an allosteric activating site when bound by SHIP's enzymatic product, PI-3,4-P2; 2 NPXY motifs that bind proteins with a phosphotyrosine binding (Shc, Dok 1, Dok 2) or an SH2 (p85a, SHIP2) domain; and a proline-rich domain consisting of four PxxP motifs that bind a subset of SH3-containing proteins including Grb2, Src, Lyn, Hck, Abl, PLCg1, and PIAS1. The SH2 domain of SHIP binds to the tyrosine phosphorylated forms of Shc, SHP-2, Doks, Gabs, CD150, platelet-endothelial cell adhesion molecule, Cas, c-Cbl, immunoreceptor tyrosine-based inhibitory motifs (ITIMs), and immunoreceptor tyrosine-based activation motifs (ITAMs). The X-linked lymphoproliferative syndrome (XLP) gene encodes SAP (also called SH2D1A/DSHP) a protein that consists of a 5 residue N-terminus, a single SH2 domain, and a short 25 residue C-terminal tail. XLP is characterized by an extreme sensitivity to Epstein-Barr virus. Both T and natural killer (NK) cell dysfunctions have been seen in XLP patients. SAP binds the cytoplasmic tail of Signaling lymphocytic activation molecule (SLAM), 2B4, Ly-9, and CD84. SAP is believed to function as a signaling inhibitor, by blocking or regulating binding of other signaling proteins. SAP and the SAP-like protein EAT-2 recognize the sequence motif TIpYXX(V/I), which is found in the cytoplasmic domains of a restricted number of T, B, and NK cell surface receptors and are proposed to be natural inhibitors or regulators of the physiological role of a small family of receptors on the surface of these cells. In general SH2 domains are involved in signal transduction. They typically bind pTyr-containing ligands via two surface pockets, a pTyr and hydrophobic binding pocket, allowing proteins with SH2 domains to localize to tyrosine phosphorylated sites.

                        10        20        30        40        50        60
                ....*....|....*....|....*....|....*....|....*....|....*....|....*
gi 24650177 441 PWFHGTLTRSEAARmvLHSDAAGHGYFLVRQSETRRGEFVLTFNFQGRAKHLRLTISEKGQCRVQ 505
Cdd:cd10343   4 PWYHGNITRSKAEE--LLSKAGKDGSFLVRDSESVSGAYALCVLYQNCVHTYRILPNAEDKLSVQ 66

Src homology 2 (SH2) domain found in the growth factor receptor bound, subclass 7 (Grb7) proteins; The Grb family binds to the epidermal growth factor receptor (EGFR, erbB1) via their SH2 domains. Grb7 is part of the Grb7 family of proteins which also includes Grb10, and Grb14. They are composed of an N-terminal Proline-rich domain, a Ras Associating-like (RA) domain, a Pleckstrin Homology (PH) domain, a phosphotyrosine interaction region (PIR, BPS) and a C-terminal SH2 domain. The SH2 domains of Grb7, Grb10 and Grb14 preferentially bind to a different RTK. Grb7 binds strongly to the erbB2 receptor, unlike Grb10 and Grb14 which bind weakly to it. Grb7 family proteins are phosphorylated on serine/threonine as well as tyrosine residues. In general SH2 domains are involved in signal transduction. They typically bind pTyr-containing ligands via two surface pockets, a pTyr and hydrophobic binding pocket, allowing proteins with SH2 domains to localize to tyrosine phosphorylated sites.

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gi 24650177 441 PWFHGTLTRSEAARMVLHSDAAgHGYFLVRQSETRRGEFVLTFNFQGRAKH-LRLTISEKGQ 501
Cdd:cd10413   6 PWFHGRISREESQRLIGQQGLV-DGVFLVRESQRNPQGFVLSLCHLQKVKHyLILPSEEEGR 66

C-terminal Src homology 2 (SH2) domain found in Zeta-chain-associated protein kinase 70 (ZAP-70); ZAP-70 and Syk comprise a family of hematopoietic cell specific protein tyrosine kinases (PTKs) that are required for antigen and antibody receptor function. ZAP-70 is expressed in T and natural killer (NK) cells and Syk is expressed in B cells, mast cells, polymorphonuclear leukocytes, platelets, macrophages, and immature T cells. They are required for the proper development of T and B cells, immune receptors, and activating NK cells. They consist of two N-terminal Src homology 2 (SH2) domains and a C-terminal kinase domain separated from the SH2 domains by a linker or hinge region. Phosphorylation of both tyrosine residues within the Immunoreceptor Tyrosine-based Activation Motifs (ITAM; consensus sequence Yxx[LI]x(7,8)Yxx[LI]) by the Src-family PTKs is required for efficient interaction of ZAP-70 and Syk with the receptor subunits and for receptor function. ZAP-70 forms two phosphotyrosine binding pockets, one of which is shared by both SH2 domains. In Syk the two SH2 domains do not form such a phosphotyrosine-binding site. The SH2 domains here are believed to function independently. In addition, the two SH2 domains of Syk display flexibility in their relative orientation, allowing Syk to accommodate a greater variety of spacing sequences between the ITAM phosphotyrosines and singly phosphorylated non-classical ITAM ligands. This model contains the C-terminus SH2 domains of Zap70. In general SH2 domains are involved in signal transduction. They typically bind pTyr-containing ligands via two surface pockets, a pTyr and hydrophobic binding pocket, allowing proteins with SH2 domains to localize to tyrosine phosphorylated sites.

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                ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 24650177 441 PWFHGTLTRSEAARMvLHSDAAGHGYFLVRQSEtRRGEFVLTFNFQGRAKHLRLTISEKGQ-CRVQHLWFPSIQEMLEHF 519
Cdd:cd10402  11 PWYHGSIARDEAERR-LYSGAQPDGKFLLRERK-ESGTYALSLVYGKTVYHYRIDQDKSGKySIPEGTKFDTLWQLVEYL 88

                ....
gi 24650177 520 RHNP 523
Cdd:cd10402  89 KLKP 92