Immunoglobulin domain; The members here are composed of the immunoglobulin (Ig) domain found in the Ig superfamily. The Ig superfamily is a heterogenous group of proteins, built on a common fold comprised of a sandwich of two beta sheets. Members of this group are components of immunoglobulin, neuroglia, cell surface glycoproteins, including T-cell receptors, CD2, CD4, CD8, and membrane glycoproteins, including butyrophilin and chondroitin sulfate proteoglycan core protein. A predominant feature of most Ig domains is a disulfide bridge connecting the two beta-sheets with a tryptophan residue packed against the disulfide bond. Ig superfamily (IgSF) domains can be divided into 4 main classes based on their structures and sequences: the Variable (V), Constant 1 (C1), Constant 2 (C2), and Intermediate (I) sets. Typically, the V-set domains have A, B, E, and D strands in one sheet and A', G, F, C, C' and C" in the other. The structures in C1-set are smaller than those in the V-set; they have one beta sheet that is formed by strands A, B, E, and D and the other by strands G, F, C, and C'. Moreover, a C1-set Ig domain contains a short C' strand (three residues) and lacks A' and C" strand. Unlike other Ig domain sets, C2-set structures do not have a D strand. Like the V-set Ig domains, members of the I-set have a discontinuous A strand, but lack a C" strand.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1905406208 182 PYISEAKGTGVPVGQKGTLQCEASAV-PSAEFQWYKDDKRLIEGK-KGVKVENRPFLSKLIFFNVSEHDYGNYTCVASNK 259
Cdd:cd05750     1 PKLKEMKSQTVQEGSKLVLKCEATSEnPSPRYRWFKDGKELNRKRpKNIKIRNKKKNSELQINKAKLEDSGEYTCVVENI 80

                  ....*..
gi 1905406208 260 LGHTNAS 266
Cdd:cd05750    81 LGKDTVT 87

Immunoglobulin domain; The members here are composed of the immunoglobulin (Ig) domain found in the Ig superfamily. The Ig superfamily is a heterogenous group of proteins, built on a common fold comprised of a sandwich of two beta sheets. Members of this group are components of immunoglobulin, neuroglia, cell surface glycoproteins, including T-cell receptors, CD2, CD4, CD8, and membrane glycoproteins, including butyrophilin and chondroitin sulfate proteoglycan core protein. A predominant feature of most Ig domains is a disulfide bridge connecting the two beta-sheets with a tryptophan residue packed against the disulfide bond. Ig superfamily (IgSF) domains can be divided into 4 main classes based on their structures and sequences: the Variable (V), Constant 1 (C1), Constant 2 (C2), and Intermediate (I) sets. Typically, the V-set domains have A, B, E, and D strands in one sheet and A', G, F, C, C' and C" in the other. The structures in C1-set are smaller than those in the V-set; they have one beta sheet that is formed by strands A, B, E, and D and the other by strands G, F, C, and C'. Moreover, a C1-set Ig domain contains a short C' strand (three residues) and lacks A' and C" strand. Unlike other Ig domain sets, C2-set structures do not have a D strand. Like the V-set Ig domains, members of the I-set have a discontinuous A strand, but lack a C" strand.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1905406208   3 NVTVRQGESATLRCTIDNRV-TRVAWLN--RSTILYagNDKWCL-DPRVVLLSNTQTQYSIEIQNVDVYDEGPYTCSVQT 78
Cdd:cd05717     5 DVTVVEGETLTLKCQVSLRDdSSLQWLNpnGQTIYF--NDKRALrDSRYQLLNHSASELSISVSNVTLSDEGVYTCLHYT 82

                          90
                  ....*....|...
gi 1905406208  79 DNhPKTSRVHLIV 91
Cdd:cd05717    83 DP-VSTKKVTVTV 94

Immunoglobulin (Ig)-like domain in neuregulins; The members here are composed of the immunoglobulin (Ig)-like domain in neuregulins (NRGs). NRGs are signaling molecules which participate in cell-cell interactions in the nervous system, breast, heart, and other organ systems, and are implicated in the pathology of diseases including schizophrenia, multiple sclerosis, and breast cancer. There are four members of the neuregulin gene family (NRG-1, NRG-2, NRG-3, and NRG-4). The NRG-1 protein, binds to and activates the tyrosine kinases receptors ErbB3 and ErbB4, initiating signaling cascades. The other NRGs proteins bind one or the other or both of these ErbBs. NRG-1 has multiple functions: in the brain it regulates various processes such as radial glia formation and neuronal migration, dendritic development, and expression of neurotransmitters receptors, while in the peripheral nervous system NRG-1 regulates processes such as target cell differentiation, and Schwann cell survival. There are many NRG-1 isoforms which arise from the alternative splicing of mRNA. Less is known of the functions of the other NRGs. NRG-2 and NRG-3 are expressed predominantly in the nervous system. NRG-2 is expressed by motor neurons and terminal Schwann cells, and is concentrated near synaptic sites and may be a signal that regulates synaptic differentiation. NRG-4 has been shown to direct pancreatic islet cell development towards the delta-cell lineage.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1905406208 182 PYISEAKGTGVPVGQKGTLQCEASAV-PSAEFQWYKDDKRLIEGK-KGVKVENRPFLSKLIFFNVSEHDYGNYTCVASNK 259
Cdd:cd05750     1 PKLKEMKSQTVQEGSKLVLKCEATSEnPSPRYRWFKDGKELNRKRpKNIKIRNKKKNSELQINKAKLEDSGEYTCVVENI 80

                  ....*..
gi 1905406208 260 LGHTNAS 266
Cdd:cd05750    81 LGKDTVT 87

Immunoglobulin domain; This family contains immunoglobulin-like domains.

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....
gi 1905406208 181 PPYIS-EAKGTGVPVGQKGTLQCEASAVPSAEFQWYKDDKRLIEGKKGVKVENRPFLSkLIFFNVSEHDYGNYTCVASN 258
Cdd:pfam13927   1 KPVITvSPSSVTVREGETVTLTCEATGSPPPTITWYKNGEPISSGSTRSRSLSGSNST-LTISNVTRSDAGTYTCVASN 78

First (N-terminal) immunoglobulin (Ig)-like domain of the nectin-like molecules; member of the V-set of Ig superfamily (IgSF) domains; The members here are composed of the N-terminal immunoglobulin (Ig)-like domain of the nectin-like molecules Necl-1 (also known as cell adhesion molecule 3 (CADM3)), Necl-2 (CADM1), Necl-3 (CADM2), and similar proteins. At least five nectin-like molecules have been identified (Necl-1 to Necl-5). They all have an extracellular region containing three Ig-like domains, a transmembrane region, and a cytoplasmic region. The N-terminal Ig-like domain of the extracellular region belongs to the V-type subfamily of Ig domains, is essential to cell-cell adhesion, and plays a part in the interaction with the envelope glycoprotein D of various viruses. Necl-1, Necl-2, and Necl-3 have Ca(2+)-independent homophilic and heterophilic cell-cell adhesion activity. Necl-1 is specifically expressed in neural tissue, and is important to the formation of synapses, axon bundles, and myelinated axons. Necl-2 is expressed in a wide variety of tissues and is a putative tumour suppressor gene which is downregulated in aggressive neuroblastoma. Necl-3 accumulates in central and peripheral nervous system tissue and has been shown to selectively interact with oligodendrocytes. This group also contains Class-I MHC-restricted T-cell-associated molecule (CRTAM), whose expression pattern is consistent with its expression in Class-I MHC-restricted T-cells.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1905406208   3 NVTVRQGESATLRCTIDNRV-TRVAWLN--RSTILYagNDKWCL-DPRVVLLSNTQTQYSIEIQNVDVYDEGPYTCSVQT 78
Cdd:cd05717     5 DVTVVEGETLTLKCQVSLRDdSSLQWLNpnGQTIYF--NDKRALrDSRYQLLNHSASELSISVSNVTLSDEGVYTCLHYT 82

                          90
                  ....*....|...
gi 1905406208  79 DNhPKTSRVHLIV 91
Cdd:cd05717    83 DP-VSTKKVTVTV 94

agrin-responsive first immunoglobulin-like domains (Ig1) of the MuSK ectodomain; a member of the I-set of IgSF domains; The members here are composed of the first immunoglobulin-like domains (Ig1) of the Muscle-specific kinase (MuSK). MuSK is a receptor tyrosine kinase specifically expressed in skeletal muscle, where it plays a central role in the formation and maintenance of the neuromuscular junction (NMJ). MuSK is activated by agrin, a neuron-derived heparan sulfate proteoglycan. The activation of MUSK in myotubes regulates the formation of NMJs through the regulation of different processes including the specific expression of genes in subsynaptic nuclei, the reorganization of the actin cytoskeleton and the clustering of the acetylcholine receptors (AChR) in the postsynaptic membrane. The Ig superfamily (IgSF) is a heterogenous group of proteins, built on a common fold comprised of a sandwich of two beta sheets. IgSF domains can be divided into 4 main classes based on their structures and sequences: the Variable (V), Constant 1 (C1), Constant 2 (C2), and Intermediate (I) sets. Unlike the V-set, one of the distinctive features of I-set domains is the lack of a C" strand. The structure of the MuSK lacks this strand and thus it belongs to the I-set of the IgSF. I-set domains are found in several cell adhesion molecules (such as VCAM, ICAM, and MADCAM), and are also present in numerous other diverse protein families, including several tyrosine-protein kinase receptors, the hemolymph protein hemolin, the muscle proteins titin, telokin, and twitchin, the neuronal adhesion molecule axonin-1, and the signaling molecule semaphorin 4D that is involved in axonal guidance, immune function and angiogenesis.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1905406208 101 SSDISINEGNNISLTCIATGRPEPTVTWRH--ISPKA----VGFVSEDEYLEIQGITREQSGDYECSASNDVAAPVVRRV 174
Cdd:cd20970     9 SFTVTAREGENATFMCRAEGSPEPEISWTRngNLIIEfntrYIVRENGTTLTIRNIRRSDMGIYLCIASNGVPGSVEKRI 88

                  ....
gi 1905406208 175 KVTV 178
Cdd:cd20970    89 TLQV 92

Immunoglobulin V-set domain; This domain is found in antibodies as well as neural protein P0 and CTL4 amongst others.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1905406208   4 VTVRQGESATLRCTI----DNRVTRVAWL-------NRSTILYAGND--KWCLDPRVVLLSNT-QTQYSIEIQNVDVYDE 69
Cdd:pfam07686   6 VTVALGGSVTLPCTYsssmSEASTSVYWYrqppgkgPTFLIAYYSNGseEGVKKGRFSGRGDPsNGDGSLTIQNLTLSDS 85

                          90       100
                  ....*....|....*....|...
gi 1905406208  70 GPYTCSVQTDNHPKTSR-VHLIV 91
Cdd:pfam07686  86 GTYTCAVIPSGEGVFGKgTRLTV 108

Immunoglobulin (Ig)-like domain in neuregulins; The members here are composed of the immunoglobulin (Ig)-like domain in neuregulins (NRGs). NRGs are signaling molecules which participate in cell-cell interactions in the nervous system, breast, heart, and other organ systems, and are implicated in the pathology of diseases including schizophrenia, multiple sclerosis, and breast cancer. There are four members of the neuregulin gene family (NRG-1, NRG-2, NRG-3, and NRG-4). The NRG-1 protein, binds to and activates the tyrosine kinases receptors ErbB3 and ErbB4, initiating signaling cascades. The other NRGs proteins bind one or the other or both of these ErbBs. NRG-1 has multiple functions: in the brain it regulates various processes such as radial glia formation and neuronal migration, dendritic development, and expression of neurotransmitters receptors, while in the peripheral nervous system NRG-1 regulates processes such as target cell differentiation, and Schwann cell survival. There are many NRG-1 isoforms which arise from the alternative splicing of mRNA. Less is known of the functions of the other NRGs. NRG-2 and NRG-3 are expressed predominantly in the nervous system. NRG-2 is expressed by motor neurons and terminal Schwann cells, and is concentrated near synaptic sites and may be a signal that regulates synaptic differentiation. NRG-4 has been shown to direct pancreatic islet cell development towards the delta-cell lineage.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1905406208 182 PYISEAKGTGVPVGQKGTLQCEASAV-PSAEFQWYKDDKRLIEGK-KGVKVENRPFLSKLIFFNVSEHDYGNYTCVASNK 259
Cdd:cd05750     1 PKLKEMKSQTVQEGSKLVLKCEATSEnPSPRYRWFKDGKELNRKRpKNIKIRNKKKNSELQINKAKLEDSGEYTCVVENI 80

                  ....*..
gi 1905406208 260 LGHTNAS 266
Cdd:cd05750    81 LGKDTVT 87

Immunoglobulin domain; This family contains immunoglobulin-like domains.

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....
gi 1905406208 181 PPYIS-EAKGTGVPVGQKGTLQCEASAVPSAEFQWYKDDKRLIEGKKGVKVENRPFLSkLIFFNVSEHDYGNYTCVASN 258
Cdd:pfam13927   1 KPVITvSPSSVTVREGETVTLTCEATGSPPPTITWYKNGEPISSGSTRSRSLSGSNST-LTISNVTRSDAGTYTCVASN 78

Immunoglobulin domain; Members of the immunoglobulin superfamily are found in hundreds of proteins of different functions. Examples include antibodies, the giant muscle kinase titin and receptor tyrosine kinases. Immunoglobulin-like domains may be involved in protein-protein and protein-ligand interactions.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1905406208 185 SEAKGTGVPVGQKGTLQCEAS-AVPSAEFQWYKDDKRLIEGKKGVKVENRPFLSKLIFFNVSEHDYGNYTCVASNKLGHT 263
Cdd:pfam00047   1 SAPPTVTVLEGDSATLTCSAStGSPGPDVTWSKEGGTLIESLKVKHDNGRTTQSSLLISNVTKEDAGTYTCVVNNPGGSA 80

                  ....
gi 1905406208 264 NASI 267
Cdd:pfam00047  81 TLST 84

First (N-terminal) immunoglobulin (Ig)-like domain of the nectin-like molecules; member of the V-set of Ig superfamily (IgSF) domains; The members here are composed of the N-terminal immunoglobulin (Ig)-like domain of the nectin-like molecules Necl-1 (also known as cell adhesion molecule 3 (CADM3)), Necl-2 (CADM1), Necl-3 (CADM2), and similar proteins. At least five nectin-like molecules have been identified (Necl-1 to Necl-5). They all have an extracellular region containing three Ig-like domains, a transmembrane region, and a cytoplasmic region. The N-terminal Ig-like domain of the extracellular region belongs to the V-type subfamily of Ig domains, is essential to cell-cell adhesion, and plays a part in the interaction with the envelope glycoprotein D of various viruses. Necl-1, Necl-2, and Necl-3 have Ca(2+)-independent homophilic and heterophilic cell-cell adhesion activity. Necl-1 is specifically expressed in neural tissue, and is important to the formation of synapses, axon bundles, and myelinated axons. Necl-2 is expressed in a wide variety of tissues and is a putative tumour suppressor gene which is downregulated in aggressive neuroblastoma. Necl-3 accumulates in central and peripheral nervous system tissue and has been shown to selectively interact with oligodendrocytes. This group also contains Class-I MHC-restricted T-cell-associated molecule (CRTAM), whose expression pattern is consistent with its expression in Class-I MHC-restricted T-cells.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1905406208   3 NVTVRQGESATLRCTIDNRV-TRVAWLN--RSTILYagNDKWCL-DPRVVLLSNTQTQYSIEIQNVDVYDEGPYTCSVQT 78
Cdd:cd05717     5 DVTVVEGETLTLKCQVSLRDdSSLQWLNpnGQTIYF--NDKRALrDSRYQLLNHSASELSISVSNVTLSDEGVYTCLHYT 82

                          90
                  ....*....|...
gi 1905406208  79 DNhPKTSRVHLIV 91
Cdd:cd05717    83 DP-VSTKKVTVTV 94

Immunoglobulin (Ig)-like domain found in neuregulin (NRG)-1; The members here are composed of the immunoglobulin (Ig)-like domain found in neuregulin (NRG)-1. There are many NRG-1 isoforms which arise from the alternative splicing of mRNA. NRG-1 belongs to the neuregulin gene family which is comprised of four genes. This group represents NRG-1. NRGs are signaling molecules which participate in cell-cell interactions in the nervous system, breast, and heart, and other organ systems, and are implicated in the pathology of diseases including schizophrenia, multiple sclerosis, and breast cancer. The NRG-1 protein binds to and activates the tyrosine kinases receptors ErbB3 and ErbB4, initiating signaling cascades. NRG-1 has multiple functions, for example, in the brain it regulates various processes such as radial glia formation and neuronal migration, dendritic development, and expression of neurotransmitters receptors in the peripheral nervous system NRG-1 regulates processes such as target cell differentiation, and Schwann cell survival.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1905406208 182 PYISEAKGTGVPVGQKGTLQCEA-SAVPSAEFQWYKDDKRLIEGKK--GVKVENRPFLSKLIFFNVSEHDYGNYTCVASN 258
Cdd:cd05895     1 PKLKEMKSQEVAAGSKLVLRCETsSEYPSLRFKWFKNGKEINRKNKpeNIKIQKKKKKSELRINKASLADSGEYMCKVSS 80

                  ....*....
gi 1905406208 259 KLGHTNASI 267
Cdd:cd05895    81 KLGNDSASA 89

Immunoglobulin like; IG domains that cannot be classified into one of IGv1, IGc1, IGc2, IG.

                           10        20        30        40        50        60        70        80
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1905406208  101 SSDISINEGNNISLTCIATGRPEPTVTWRHISPKAVGF--------VSEDEYLEIQGITREQSGDYECSASNDvAAPVVR 172
Cdd:smart00410   1 PPSVTVKEGESVTLSCEASGSPPPEVTWYKQGGKLLAEsgrfsvsrSGSTSTLTISNVTPEDSGTYTCAATNS-SGSASS 79

                   ....*.
gi 1905406208  173 RVKVTV 178
Cdd:smart00410  80 GTTLTV 85

Fourth immunoglobulin domain of the Drosophila melanogaster Dscam protein, and similar domains; a member of the I-set of IgSF domains; The members here are composed of the fourth immunoglobulin domain of the Drosophila melanogaster Down syndrome cell adhesion molecule (DSCAM) protein and similar proteins. Down syndrome cell adhesion molecule (DSCAM) is a cell adhesion molecule that plays critical roles in neural development, including axon guidance and branching, axon target recognition, self-avoidance and synaptic formation. DSCAM belongs to the immunoglobulin superfamily and contributes to defects in the central nervous system in Down syndrome patients. Vertebrate DSCAMs differ from Drosophila Dscam1 in that they lack the extensive alternative splicing that occurs in the insect gene. Drosophila melanogaster Dscam has 38,016 isoforms generated by the alternative splicing of four variable exon clusters, which allows every neuron in the fly to display a distinctive set of Dscam proteins on its cell surface. Drosophila Dscam1 is a cell-surface protein that plays important roles in neural development and axon tiling of neurons. It is shown that thousands of isoforms bind themselves through specific homophilic (self-binding) interactions, a process which mediates cellular self-recognition. Drosophila Dscam2 is also alternatively spliced and plays a key role in the development of two visual system neurons, monopolar cells L1 and L2. This group is a member of the I-set Ig domains, having A-B-E-D strands in one beta-sheet and A'-G-F-C-C' in the other. Like the V-set Ig domains, members of the I-set have a discontinuous A strand but lack a C" strand.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1905406208  95 PKIVEISSDISINEGNNISLTCIATGRPEPTVTW----RHISPKA---VG-FVSED----EYLEIQGITREQSGDYECSA 162
Cdd:cd20956     2 PVLLETFSEQTLQPGPSVSLKCVASGNPLPQITWtldgFPIPESPrfrVGdYVTSDgdvvSYVNISSVRVEDGGEYTCTA 81

                  ....*.
gi 1905406208 163 SNDVAA 168
Cdd:cd20956    82 TNDVGS 87

First (N-terminal) immunoglobulin (Ig)-like domain of nectin-like molecule-3; member of the V-set of Ig superfamily (IgSF) domains; The members here are composed of the N-terminal immunoglobulin (Ig)-like domain of nectin-like molecule-3, Necl-3 (also known as cell adhesion molecule 2 (CADM2), SynCAM2, IGSF4D). Nectin-like molecules have similar domain structures to those of nectins. At least five nectin-like molecules have been identified (Necl-1 - Necl-5). They all have an extracellular region containing three Ig-like domains, a transmembrane region, and a cytoplasmic region. The N-terminal Ig-like domain of the extracellular region, belongs to the V-type subfamily of Ig domains, is essential to cell-cell adhesion, and plays a part in the interaction with the envelope glycoprotein D of various viruses. Necl-3 accumulates in central and peripheral nervous system tissue, and has been shown to selectively interact with oligodendrocytes.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1905406208   3 NVTVRQGESATLRCTID-NRVTRVAWLNRST-ILYAGNDKWCLDPRVVLLSNTQTQYSIEIQNVDVYDEGPYTCSVQTdn 80
Cdd:cd07701     6 NVTVVEGGTANLTCRVDqNDNTSLQWSNPAQqTLYFDDKKALRDNRIELVRASWHELSISISDVSLSDEGQYTCSLFT-- 83

                          90
                  ....*....|..
gi 1905406208  81 HP-KTSRVHLIV 91
Cdd:cd07701    84 MPvKTSKAYLTV 95

Second immunoglobulin (Ig)-like domain of fibroblast growth factor (FGF) receptor_like-1(FGFRL1); member of the I-set of IgSF domains; The members here are composed of the second immunoglobulin (Ig)-like domain of fibroblast growth factor (FGF) receptor like-1(FGFRL1). FGFRL1 is comprised of a signal peptide, three extracellular Ig-like modules, a transmembrane segment, and a short intracellular domain. FGFRL1 is expressed preferentially in skeletal tissues. Similar to FGF receptors, the expressed protein interacts specifically with heparin and with FGF2. FGFRL1 does not have a protein tyrosine kinase domain at its C-terminus; neither does its cytoplasmic domain appear to interact with a signaling partner. It has been suggested that FGFRL1 may not have any direct signaling function, but instead acts as a decoy receptor trapping FGFs and preventing them from binding other receptors.

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....
gi 1905406208 193 PVGQKGTLQCEASAVPSAEFQWYKDDKRLIEGKKGvkvENRPFLSKLIFFNVSEHDYGNYTCVASNKLGHTNAS 266
Cdd:cd05856    17 PVGSSVRLKCVASGNPRPDITWLKDNKPLTPPEIG---ENKKKKWTLSLKNLKPEDSGKYTCHVSNRAGEINAT 87

Second immunoglobulin (Ig)-like domain of fibroblast growth factor (FGF) receptor, and similar domains; member of the I-set of IgSF domains; The members here are composed of the second immunoglobulin (Ig)-like domain of fibroblast growth factor (FGF) receptor. FGF receptors bind FGF signaling polypeptides. FGFs participate in multiple processes such as morphogenesis, development, and angiogenesis. FGFs bind to four FGF receptor tyrosine kinases (FGFR1, FGFR2, FGFR3, FGFR4). Receptor diversity is controlled by alternative splicing producing splice variants with different ligand binding characteristics and different expression patterns. FGFRs have an extracellular region comprised of three Ig-like domains, a single transmembrane helix, and an intracellular tyrosine kinase domain. Ligand binding and specificity reside in the Ig-like domains 2 and 3, and the linker region that connects these two. FGFR activation and signaling depend on FGF-induced dimerization, a process involving cell surface heparin or heparin sulfate proteoglycans. This group also contains fibroblast growth factor (FGF) receptor like-1(FGFRL1). FGFRL1 does not have a protein tyrosine kinase domain at its C-terminus; neither does its cytoplasmic domain appear to interact with a signaling partner. It has been suggested that FGFRL1 may not have any direct signaling function, but instead acts as a decoy receptor trapping FGFs and preventing them from binding other receptors.

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*..
gi 1905406208 192 VPVGQKGTLQCEASAVPSAEFQWYKDDKRL--IEGKKGVKVENRPFLskLIFFNVSEHDYGNYTCVASNKLGHTNAS 266
Cdd:cd05729    16 LPAANKVRLECGAGGNPMPNITWLKDGKEFkkEHRIGGTKVEEKGWS--LIIERAIPRDKGKYTCIVENEYGSINHT 90

Immunoglobulin domain; This domain contains immunoglobulin-like domains.

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1905406208 192 VPVGQKGTLQCEASAVPSAEFQWYKDDKRLIEGKkgvkvenrpflsKLIFFNVSEHDYGNYTCVASNKLG 261
Cdd:pfam13895  11 VTEGEPVTLTCSAPGNPPPSYTWYKDGSAISSSP------------NFFTLSVSAEDSGTYTCVARNGRG 68

Fourth Ig-like domain from smooth muscle myosin light chain kinase and similar domains ; a member of the I-set of IgSF domains; The members here are composed of the fourth immunoglobulin (Ig)-like domain from smooth muscle myosin light chain kinase (MYLK) and similar domains. The Ig superfamily (IgSF) is a heterogenous group of proteins, built on a common fold comprised of a sandwich of two beta sheets. IgSF domains can be divided into 4 main classes based on their structures and sequences: the Variable (V), Constant 1 (C1), Constant 2 (C2), and Intermediate (I) sets. Unlike the V-set, one of the distinctive features of I-set domains is the lack of a C" strand. The structure of this group shows that the fourth Ig-like domain from myosin light chain kinase lacks this strand and thus belongs to the I-set of the IgSF. I-set domains are found in several cell adhesion molecules (such as VCAM, ICAM, and MADCAM), and are also present in numerous other diverse protein families, including several tyrosine-protein kinase receptors, the hemolymph protein hemolin, the muscle proteins titin, telokin, and twitchin, the neuronal adhesion molecule axonin-1, and the signaling molecule semaphorin 4D that is involved in axonal guidance, immune function and angiogenesis.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1905406208 181 PPYISEAKGTGVPVGQKGTLQCEASAVPSAEFQWYKDDKRLieGKKGVKVENRPFLSKLIFFNVSEHDYGNYTCVASNKL 260
Cdd:cd20976     2 PSFSSVPKDLEAVEGQDFVAQCSARGKPVPRITWIRNAQPL--QYAADRSTCEAGVGELHIQDVLPEDHGTYTCLAKNAA 79

                  ....*....
gi 1905406208 261 GHTNASIML 269
Cdd:cd20976    80 GQVSCSAWV 88

Seventh immunoglobulin domain of the Drosophila melanogaster Dscam protein, and similar domains; a member of the I-set of IgSF domains; The members here are composed of the seventh immunoglobulin domain of the Drosophila melanogaster Down syndrome cell adhesion molecule (DSCAM) protein and similar proteins. Down syndrome cell adhesion molecule (DSCAM) is a cell adhesion molecule that plays critical roles in neural development, including axon guidance and branching, axon target recognition, self-avoidance and synaptic formation. DSCAM belongs to the immunoglobulin superfamily and contributes to defects in the central nervous system in Down syndrome patients. Vertebrate DSCAMs differ from Drosophila Dscam1 in that they lack the extensive alternative splicing that occurs in the insect gene. Drosophila melanogaster Dscam has 38,016 isoforms generated by the alternative splicing of four variable exon clusters, which allows every neuron in the fly to display a distinctive set of Dscam proteins on its cell surface. Drosophila Dscam1 is a cell-surface protein that plays important roles in neural development and axon tiling of neurons. It is shown that thousands of isoforms bind themselves through specific homophilic (self-binding) interactions, a process which mediates cellular self-recognition. Drosophila Dscam2 is also alternatively spliced and plays a key role in the development of two visual system neurons, monopolar cells L1 and L2. This group is a member of the I-set Ig domains, having A-B-E-D strands in one beta-sheet and A'-G-F-C-C' in the other. Like the V-set Ig domains, members of the I-set have a discontinuous A strand but lack a C" strand.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1905406208  95 PK-IVEiSSDISINEGNNISLTCIATGRPEPTVTWRhispKAVGfVSEDEY----------------LEIQGITREQSGD 157
Cdd:cd20954     2 PRwIVE-PVDANVAAGQDVMLHCQADGFPTPTVTWK----KATG-STPGEYkdllydpnvrilpngtLVFGHVQKENEGH 75

                          90       100
                  ....*....|....*....|.
gi 1905406208 158 YECSASNDVAAPVVRRVKVTV 178
Cdd:cd20954    76 YLCEAKNGIGSGLSKVIFLKV 96

agrin-responsive first immunoglobulin-like domains (Ig1) of the MuSK ectodomain; a member of the I-set of IgSF domains; The members here are composed of the first immunoglobulin-like domains (Ig1) of the Muscle-specific kinase (MuSK). MuSK is a receptor tyrosine kinase specifically expressed in skeletal muscle, where it plays a central role in the formation and maintenance of the neuromuscular junction (NMJ). MuSK is activated by agrin, a neuron-derived heparan sulfate proteoglycan. The activation of MUSK in myotubes regulates the formation of NMJs through the regulation of different processes including the specific expression of genes in subsynaptic nuclei, the reorganization of the actin cytoskeleton and the clustering of the acetylcholine receptors (AChR) in the postsynaptic membrane. The Ig superfamily (IgSF) is a heterogenous group of proteins, built on a common fold comprised of a sandwich of two beta sheets. IgSF domains can be divided into 4 main classes based on their structures and sequences: the Variable (V), Constant 1 (C1), Constant 2 (C2), and Intermediate (I) sets. Unlike the V-set, one of the distinctive features of I-set domains is the lack of a C" strand. The structure of the MuSK lacks this strand and thus it belongs to the I-set of the IgSF. I-set domains are found in several cell adhesion molecules (such as VCAM, ICAM, and MADCAM), and are also present in numerous other diverse protein families, including several tyrosine-protein kinase receptors, the hemolymph protein hemolin, the muscle proteins titin, telokin, and twitchin, the neuronal adhesion molecule axonin-1, and the signaling molecule semaphorin 4D that is involved in axonal guidance, immune function and angiogenesis.

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1905406208 192 VPVGQKGTLQCEASAVPSAEFQWYKDDKRLIEGKKGVKVENRPflSKLIFFNVSEHDYGNYTCVASNKLG 261
Cdd:cd20970    14 AREGENATFMCRAEGSPEPEISWTRNGNLIIEFNTRYIVRENG--TTLTIRNIRRSDMGIYLCIASNGVP 81

Third immunoglobulin (Ig)-like domain of the L1 cell adhesion molecule (CAM), and similar domains; The members here are composed of the third immunoglobulin (Ig)-like domain of the L1 cell adhesion molecule (CAM). L1 belongs to the L1 subfamily of cell adhesion molecules (CAMs) and is comprised of an extracellular region having six Ig-like domains and five fibronectin type III domains, a transmembrane region and an intracellular domain. L1 is primarily expressed in the nervous system and is involved in its development and function. L1 is associated with an X-linked recessive disorder, X-linked hydrocephalus, MASA syndrome, and spastic paraplegia type 1, that involves abnormalities of axonal growth. This group also contains the chicken neuron-glia cell adhesion molecule, Ng-CAM and human neurofascin.

                          10        20        30        40        50        60
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*...
gi 1905406208 101 SSDISINEGNNISLTCIATGRPEPTVTWRHIS----PKAVGFVSEDEYLEIQGITREQSGDYECSASN 164
Cdd:cd05731     2 ESSTMVLRGGVLLLECIAEGLPTPDIRWIKLGgelpKGRTKFENFNKTLKIENVSEADSGEYQCTASN 69

Fourth immunoglobulin (Ig)-like domain of hemolin, and similar domains; a member of the I-set of IgSF domains; The members here are composed of the fourth immunoglobulin (Ig)-like domain of hemolin and similar proteins. Hemolin, an insect immunoglobulin superfamily (IgSF) member containing four Ig-like domains, is a lipopolysaccharide-binding immune protein induced during bacterial infection. Hemolin shares significant sequence similarity with the first four Ig-like domains of the transmembrane cell adhesion molecules (CAMs) of the L1 family. IgSF domains can be divided into 4 main classes based on their structures and sequences: the Variable (V), Constant 1 (C1), Constant 2 (C2), and Intermediate (I) sets. The fourth Ig-like domain of hemolin is a member of the I-set Ig domains, having A-B-E-D strands in one beta-sheet and A'-G-F-C-C' in the other. Like the V-set domains, members of the I-set have a discontinuous A strand but lack a C" strand. I-set domains are found in several cell adhesion molecules (such as VCAM, ICAM, and MADCAM), and are also present in numerous other diverse protein families, including several tyrosine-protein kinase receptors, the muscle proteins titin, telokin, and twitchin, the neuronal adhesion molecule axonin-1, and the signaling molecule semaphorin 4D that is involved in axonal guidance, immune function and angiogenesis.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1905406208  95 PKIV-EISSDISINEGNNISLTCIATGRPEPTVTW----RHISPKAVGFVSEDEYLEIQGITREQSGDYECSASNdVAAP 169
Cdd:cd20978     1 PKFIqKPEKNVVVKGGQDVTLPCQVTGVPQPKITWlhngKPLQGPMERATVEDGTLTIINVQPEDTGYYGCVATN-EIGD 79

                  ....*....
gi 1905406208 170 VVRRVKVTV 178
Cdd:cd20978    80 IYTETLLHV 88

Fourth immunoglobulin (Ig)-like domain of peroxidasin; The members here are composed of the fourth immunoglobulin (Ig)-like domain in peroxidasin. Peroxidasin has a peroxidase domain and interacting extracellular motifs containing four Ig-like domains. It has been suggested that peroxidasin is secreted, and has functions related to the stabilization of the extracellular matrix. It may play a part in various other important processes such as removal and destruction of cells which have undergone programmed cell death and protection of the organism against non-self.

                          10        20        30        40        50
                  ....*....|....*....|....*....|....*....|....*....|....*..
gi 1905406208 112 ISLTCIATGRPEPTVTWR----HISPKAVGFVSEDEYLEIQGITREQSGDYECSASN 164
Cdd:cd05746     1 VQIPCSAQGDPEPTITWNkdgvQVTESGKFHISPEGYLAIRDVGVADQGRYECVARN 57

Third immunoglobulin (Ig) domain of contactin-1; member of the I-set of Ig superfamily (IgSF) domains; The members here are composed of the third immunoglobulin (Ig) domain of the neural cell adhesion molecule contactin-1. Contactins are comprised of six Ig domains followed by four fibronectin type III (FnIII) domains anchored to the membrane by glycosylphosphatidylinositol. Contactin-1 is differentially expressed in tumor tissues and may through a RhoA mechanism, facilitate invasion and metastasis of human lung adenocarcinoma. This group belongs to the I-set of IgSF domains.

                          10        20        30        40        50
                  ....*....|....*....|....*....|....*....|....*....|....*....
gi 1905406208 109 GNNISLTCIATGRPEPTVTWRHIS---PKAVGFVSEDEYLEIQGITREQSGDYECSASN 164
Cdd:cd05851    16 GQNVTLECFALGNPVPVIRWRKILepmPATAEISMSGAVLKIFNIQPEDEGTYECEAEN 74

Second immunoglobulin (Ig)-like domain of fibroblast growth factor (FGF) receptor; member of the I-set of IgSF domains; The members here are composed of the second immunoglobulin (Ig)-like domain of fibroblast growth factor (FGF) receptor. FGF receptors bind FGF signaling polypeptides. FGFs participate in multiple processes such as morphogenesis, development, and angiogenesis. FGFs bind to four FGF receptor tyrosine kinases (FGFR1, FGFR2, FGFR3, FGFR4). Receptor diversity is controlled by alternative splicing producing splice variants with different ligand binding characteristics and different expression patterns. FGFRs have an extracellular region comprised of three IG-like domains, a single transmembrane helix, and an intracellular tyrosine kinase domain. Ligand binding and specificity reside in the Ig-like domains 2 and 3, and the linker region that connects these two. FGFR activation and signaling depend on FGF-induced dimerization, a process involving cell surface heparin or heparin sulfate proteoglycans.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1905406208 186 EAKGTGVPVGQKGTLQCEASAVPSAEFQWYKDDKRLIEGKK--GVKVENRPFlsKLIFFNVSEHDYGNYTCVASNKLGHT 263
Cdd:cd05857    10 EKKLHAVPAANTVKFRCPAAGNPTPTMRWLKNGKEFKQEHRigGYKVRNQHW--SLIMESVVPSDKGNYTCVVENEYGSI 87

                  .
gi 1905406208 264 N 264
Cdd:cd05857    88 N 88

Second immunoglobulin (Ig)-like domain of interleukin-1 receptor (IL1R), and similar domains; The members here are composed of the second immunoglobulin (Ig)-like domain of interleukin-1 receptor (IL1R; also known as cluster of differentiation (CD) 121). IL-1 alpha and IL-1 beta are cytokines which participate in the regulation of inflammation, immune responses, and hematopoiesis. These cytokines bind to the IL-1 receptor type 1 (IL1R1), which is activated on additional association with interleukin-1 receptor accessory protein (IL1RAP). IL-1 also binds a second receptor designated type II (IL1R2). Mature IL1R1 consists of three IG-like domains, a transmembrane domain, and a large cytoplasmic domain. Mature IL1R2 is organized similarly except that it has a short cytoplasmic domain. The latter does not initiate signal transduction. A naturally occurring cytokine IL-1RA (IL-1 receptor antagonist) is widely expressed and binds to IL-1 receptors, inhibiting the binding of IL-1 alpha and IL-1 beta. This group also contains ILIR-like 1 (IL1R1L) which maps to the same chromosomal location as IL1R1 and IL1R2.

                          10        20        30        40
                  ....*....|....*....|....*....|....*....|....*....
gi 1905406208 209 SAEFQWYKDDKrLIEGKKGVKVENrpflSKLIFFNVSEHDYGNYTCVAS 257
Cdd:cd05757    29 LPPIQWYKDCK-PLQGDKRFIPKG----SKLLIQNVTEEDAGNYTCKFT 72

Fourth immunoglobulin (Ig)-like domain of L1, Ng-CAM (Neuron-glia CAM cell adhesion molecule), and NrCAM (Ng-CAM-related); The members here are composed of the fourth immunoglobulin (Ig)-like domain of L1, Ng-CAM (Neuron-glia CAM cell adhesion molecule), and NrCAM (Ng-CAM-related). These proteins belong to the L1 subfamily of cell adhesion molecules (CAMs) and are comprised of an extracellular region having six Ig-like domains and five fibronectin type III domains, a transmembrane region and an intracellular domain. These molecules are primarily expressed in the nervous system. L1 is associated with an X-linked recessive disorder, X-linked hydrocephalus, MASA syndrome, or spastic paraplegia type 1, that involves abnormalities of axonal growth.

                          10        20        30        40        50        60
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....
gi 1905406208 102 SDISINEGNNISLTCIATGRPEPTVTWR------HISPKAVGFVSEDEYLEIQGITREQSGDYECSASN 164
Cdd:cd04978     7 PSLVLSPGETGELICEAEGNPQPTITWRlngvpiEPAPEDMRRTVDGRTLIFSNLQPNDTAVYQCNASN 75

Fourth immunoglobulin (Ig)-like domain of hemolin, and similar domains; a member of the I-set of IgSF domains; The members here are composed of the fourth immunoglobulin (Ig)-like domain of hemolin and similar proteins. Hemolin, an insect immunoglobulin superfamily (IgSF) member containing four Ig-like domains, is a lipopolysaccharide-binding immune protein induced during bacterial infection. Hemolin shares significant sequence similarity with the first four Ig-like domains of the transmembrane cell adhesion molecules (CAMs) of the L1 family. IgSF domains can be divided into 4 main classes based on their structures and sequences: the Variable (V), Constant 1 (C1), Constant 2 (C2), and Intermediate (I) sets. The fourth Ig-like domain of hemolin is a member of the I-set Ig domains, having A-B-E-D strands in one beta-sheet and A'-G-F-C-C' in the other. Like the V-set domains, members of the I-set have a discontinuous A strand but lack a C" strand. I-set domains are found in several cell adhesion molecules (such as VCAM, ICAM, and MADCAM), and are also present in numerous other diverse protein families, including several tyrosine-protein kinase receptors, the muscle proteins titin, telokin, and twitchin, the neuronal adhesion molecule axonin-1, and the signaling molecule semaphorin 4D that is involved in axonal guidance, immune function and angiogenesis.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1905406208 181 PPYISEA-KGTGVPVGQKGTLQCEASAVPSAEFQWYKDDKRLIEGKKGVKVENrpflSKLIFFNVSEHDYGNYTCVASNK 259
Cdd:cd20978     1 PKFIQKPeKNVVVKGGQDVTLPCQVTGVPQPKITWLHNGKPLQGPMERATVED----GTLTIINVQPEDTGYYGCVATNE 76

                          90
                  ....*....|
gi 1905406208 260 LGHTNASIML 269
Cdd:cd20978    77 IGDIYTETLL 86

Second Ig-like domain of Junctional adhesion molecule-1 (JAM1); a member of the I-set of IgSF domains; The members here are composed of the second Ig-like domain of Junctional adhesion molecule-1 (JAM1). JAM1 is an immunoglobulin superfamily (IgSF) protein with two Ig-like domains in its extracellular region; it plays a role in the formation of endothelial and epithelial tight junction and acts as a receptor for mammalian reovirus sigma-1. The IgSF is a heterogenous group of proteins, built on a common fold comprised of a sandwich of two beta sheets. The two sheets are linked together by a conserved disulfide bond between B strand and F strand. IgSF domains can be divided into 4 main classes based on their structures and sequences: the Variable (V), Constant 1 (C1), Constant 2 (C2), and Intermediate (I) sets. The second Ig-like domain of JAM1 is a member of the I-set Ig domains, having A-B-E-D strands in one beta-sheet and A'-G-F-C-C' in the other. Like the V-set Ig domains, the A strand of the I-set is discontinuous but lacks a C" strand. I-set domains are found in several cell adhesion molecules (such as VCAM, ICAM, and MADCAM), and are also present in numerous other diverse protein families, including several tyrosine-protein kinase receptors.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1905406208 177 TVNYPpyiseakgTGVPVGQKGTLQC-EASAVPSAEFQWYKD------DKRLIEGKKGVKVENRPFLSKLIFFNVSEHDY 249
Cdd:cd20950     2 TVNIP--------SSATIGNRAVLTCsEPDGSPPSEYTWFKDgvvmptNPKSTRAFSNSSYSLDPTTGELVFDPLSASDT 73

                          90
                  ....*....|..
gi 1905406208 250 GNYTCVASNKLG 261
Cdd:cd20950    74 GEYSCEARNGYG 85

First immunoglobulin (Ig)-like constant domain in Robo (roundabout) receptors, and similar domains; The members here are composed of the first immunoglobulin (Ig)-like domain in Roundabout (Robo) receptors. Robo receptors play a role in the development of the central nervous system (CNS), and are receptors of Slit protein. Slit is a repellant secreted by the neural cells in the midline. Slit acts through Robo to prevent most neurons from crossing the midline from either side. Three mammalian Robo homologs (Robo1, Robo2, and Robo3), and three mammalian Slit homologs (Slit1, Slit2, Slit3), have been identified. Commissural axons, which cross the midline, express low levels of Robo; longitudinal axons, which avoid the midline, express high levels of Robo. Robo1, Robo2, and Robo3 are expressed by commissural neurons in the vertebrate spinal cord and Slit1, Slit2,and Slit3 are expressed at the ventral midline. Robo3 is a divergent member of the Robo family which instead of being a positive regulator of Slit responsiveness, antagonizes Slit responsiveness in precrossing axons. The Slit-Robo interaction is mediated by the second leucine-rich repeat (LRR) domain of Slit and the two N-terminal Ig domains of Robo, Ig1 and Ig2. The primary Robo binding site for Slit2 has been shown by surface plasmon resonance experiments and mutational analysis to be is the Ig1 domain, while the Ig2 domain has been proposed to harbor a weak secondary binding site.

                          10        20        30
                  ....*....|....*....|....*....|....
gi 1905406208  95 PKIVEISSDISINEGNNISLTCIATGRPEPTVTW 128
Cdd:cd07693     1 PRIVEHPSDLIVSKGDPATLNCKAEGRPTPTIQW 34

Immunoglobulin V-set domain; This domain is found in antibodies as well as neural protein P0 and CTL4 amongst others.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1905406208   4 VTVRQGESATLRCTI----DNRVTRVAWL-------NRSTILYAGND--KWCLDPRVVLLSNT-QTQYSIEIQNVDVYDE 69
Cdd:pfam07686   6 VTVALGGSVTLPCTYsssmSEASTSVYWYrqppgkgPTFLIAYYSNGseEGVKKGRFSGRGDPsNGDGSLTIQNLTLSDS 85

                          90       100
                  ....*....|....*....|...
gi 1905406208  70 GPYTCSVQTDNHPKTSR-VHLIV 91
Cdd:pfam07686  86 GTYTCAVIPSGEGVFGKgTRLTV 108

Fifth Ig-like domain of Roundabout (Robo) homolog 1/2, and similar domains; a member of the I-set of IgSF domains; The members here are composed of the fifth Ig-like domain of Roundabout (Robo) homolog 1/2 and similar domains. Robo receptors play a role in the development of the central nervous system (CNS), and are receptors of Slit protein. Slit is a repellant secreted by the neural cells in the midline. Slit acts through Robo to prevent most neurons from crossing the midline from either side. Three mammalian Robo homologs (Robo1, -2, and -3), and three mammalian Slit homologs (Slit-1,-2, -3), have been identified. Commissural axons, which cross the midline, express low levels of Robo; longitudinal axons, which avoid the midline, express high levels of Robo. Robo1, -2, and -3 are expressed by commissural neurons in the vertebrate spinal cord and Slits 1, -2, -3 are expressed at the ventral midline. Robo-3 is a divergent member of the Robo family which instead of being a positive regulator of slit responsiveness, antagonizes slit responsiveness in precrossing axons. The Slit-Robo interaction is mediated by the second leucine-rich repeat (LRR) domain of Slit and the two N-terminal Ig domains of Robo, Ig1 and Ig2. The primary Robo binding site for Slit2 has been shown by surface plasmon resonance experiments and mutational analysis to be is the Ig1 domain, while the Ig2 domain has been proposed to harbor a weak secondary binding site. The fifth Ig-like domain of Robo 1 and 2 is a member of the I-set Ig domains, having A-B-E-D strands in one beta-sheet and A'-G-F-C-C' in the other. Like the V-set Ig domains, members of the I-set have a discontinuous A strand but lack a C" strand. I-set domains are found in several cell adhesion molecules (such as VCAM, ICAM, and MADCAM), and are also present in numerous other diverse protein families, including several tyrosine-protein kinase receptors

                          10        20        30        40        50        60        70
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*.
gi 1905406208  97 IVEISSDISINEGNNISLTCIATGRPEPTVTWRHispKAVGFVSEDEY--------LEIQGITREQSGDYECSASN 164
Cdd:cd20952     2 ILQGPQNQTVAVGGTVVLNCQATGEPVPTISWLK---DGVPLLGKDERittlengsLQIKGAEKSDTGEYTCVALN 74

Fourth Ig-like domain from smooth muscle myosin light chain kinase and similar domains ; a member of the I-set of IgSF domains; The members here are composed of the fourth immunoglobulin (Ig)-like domain from smooth muscle myosin light chain kinase (MYLK) and similar domains. The Ig superfamily (IgSF) is a heterogenous group of proteins, built on a common fold comprised of a sandwich of two beta sheets. IgSF domains can be divided into 4 main classes based on their structures and sequences: the Variable (V), Constant 1 (C1), Constant 2 (C2), and Intermediate (I) sets. Unlike the V-set, one of the distinctive features of I-set domains is the lack of a C" strand. The structure of this group shows that the fourth Ig-like domain from myosin light chain kinase lacks this strand and thus belongs to the I-set of the IgSF. I-set domains are found in several cell adhesion molecules (such as VCAM, ICAM, and MADCAM), and are also present in numerous other diverse protein families, including several tyrosine-protein kinase receptors, the hemolymph protein hemolin, the muscle proteins titin, telokin, and twitchin, the neuronal adhesion molecule axonin-1, and the signaling molecule semaphorin 4D that is involved in axonal guidance, immune function and angiogenesis.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1905406208  95 PKIVEISSDISINEGNNISLTCIATGRPEPTVTW----RHISPKAVGFVSEDEY--LEIQGITREQSGDYECSASNdVAA 168
Cdd:cd20976     2 PSFSSVPKDLEAVEGQDFVAQCSARGKPVPRITWirnaQPLQYAADRSTCEAGVgeLHIQDVLPEDHGTYTCLAKN-AAG 80

                          90
                  ....*....|
gi 1905406208 169 PVVRRVKVTV 178
Cdd:cd20976    81 QVSCSAWVTV 90