The phosphoinositide binding Phox Homology domain of RPK118-like proteins; The PX domain is a phosphoinositide (PI) binding module present in many proteins with diverse functions such as cell signaling, vesicular trafficking, protein sorting, and lipid modification, among others. Members of this subfamily bear similarity to human RPK118, which contains an N-terminal PX domain, a Microtubule Interacting and Trafficking (MIT) domain, and a kinase domain. RPK118 binds sphingosine kinase, a key enzyme in the synthesis of sphingosine 1-phosphate (SPP), a lipid messenger involved in many cellular events. RPK118 may be involved in transmitting SPP-mediated signaling. It also binds the antioxidant peroxiredoxin-3 (PRDX3) and may be involved in the transport of PRDX3 from the cytoplasm to its site of function in the mitochondria. Members of this subfamily also show similarity to sorting nexin 15 (SNX15), which contains PX and MIT domains but does not contain a kinase domain. SNXs make up the largest group among PX domain containing proteins. They are involved in regulating membrane traffic and protein sorting in the endosomal system. The PX domain of SNXs binds PIs and targets the protein to PI-enriched membranes. SNX15 plays a role in protein trafficking processes in the endocytic pathway and the trans-Golgi network. The PX domain of SNX15 interacts with the PDGF receptor and is responsible for the membrane association of the protein.

                           10        20        30        40        50        60        70        80
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1564316791   10 IVRFYTVTDPTTHKKGYTVYKVTARIISRKNPEDIQEITVWKRYSDFKKLHQNLWQIHRNLYGQSELFPPFAKAKVFGRF 89
Cdd:cd07287      1 LARFYTVTDPRRHPKGYTVYKVTARIVSRKNPEDVQEIVVWKRYSDFKKLHKDLWQIHKNLCRQSELFPPFAKAKVFGRF 80

                           90       100       110
                   ....*....|....*....|....*....|....*...
gi 1564316791   90 DESVIEKRRQCSEDLLQFSANIPALYGSHYIQDFFKGG 127
Cdd:cd07287     81 DESVIEERRQCAEDLLQFSANIPALYNSSQLEDFFKGG 118

Kunitz domain 1 of hepatocyte growth factor activator inhibitor-1 (HAI-1); This model includes Kunitz domain 1 (KD1) of hepatocyte growth factor activator inhibitor type 1 (HAI1 or HAI-1, also known as Kunitz-type protease inhibitor 1), a membrane-bound multidomain protein essential to the integrity of the basement membrane during placental development. HAI-1 contains an extracellular region and several internal domains that include two Kunitz domains separated in sequence but spatially closed to each other, and their interdomain interactions have evolved to stimulate the inhibitory activity of an integrated Kunitz. KD1, the major inhibitory domain of HAI-1, is involved in auto-inhibition of the extracellular region via steric blockage of its active site in the HAI-1 compact tertiary structure; presence of the target protease causes changes in the HAI-1 structure to an extended conformation. HAI-1 has been shown to inhibit several serine proteases such as matripase, hepsin, trypsin, hepatocyte growth factor activator (HGFA), and prostasin. It is also important in maintaining postnatal homeostasis in many tissues, including keratinization of the epidermis, hair development, colonic epithelium integrity, proliferation and cell fate of neural progenitor cells, and tissue injury and repair. The interaction between HAI-1 and matriptase is critical for tissue morphogenesis and cellular biology. HAI-1:matriptase ratio imbalance results in tumorigenesis; slight overexpression of matriptase relative to HAI-1 causes spontaneous squamous cell carcinoma, a phenotype that can be effectively reversed back to wild type by additional expression of HAI-1, indicating the need for a tight functional relationship between the two to maintain homeostasis. The structures of these domains are similar to those of Kunitz-type proteinase inhibitors such as BPTI (bovine pancreatic trypsin inhibitor), showing an alpha/beta fold with irregular secondary structure stabilized by three disulfide bonds.

                           10        20        30        40        50
                   ....*....|....*....|....*....|....*....|....*....|....*...
gi 1564316791  946 QSERHCLAPKKVGPCRGYFPRWHYNAASKNCEQFYFGGCKENNNNYLSKQECLNACKN 1003
Cdd:cd22623      1 QSELYCLAPKKVGPCRGSFPRWHYNAASGKCEEFVFGGCKGNKNNYLSEEECLSACRG 58

MIT: domain contained within Microtubule Interacting and Trafficking molecules. This MIT domain sub-family is found in sorting nexin 15 and related proteins. The molecular function of the MIT domain is unclear.

                           10        20        30        40        50        60
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*..
gi 1564316791  248 DYLEEASEQIALAVQKEVEQDFAVAFSYYRRGVDLLLQGVQGEVSPSRREAVKRKTAEYLMRAELIS 314
Cdd:cd02677      1 DYLEQAAELIRLALEKEEEGDYEAAFEFYRAGVDLLLKGVQGDSSPERREAVKRKIAEYLKRAEEIL 67

The phosphoinositide binding Phox Homology domain of RPK118-like proteins; The PX domain is a phosphoinositide (PI) binding module present in many proteins with diverse functions such as cell signaling, vesicular trafficking, protein sorting, and lipid modification, among others. Members of this subfamily bear similarity to human RPK118, which contains an N-terminal PX domain, a Microtubule Interacting and Trafficking (MIT) domain, and a kinase domain. RPK118 binds sphingosine kinase, a key enzyme in the synthesis of sphingosine 1-phosphate (SPP), a lipid messenger involved in many cellular events. RPK118 may be involved in transmitting SPP-mediated signaling. It also binds the antioxidant peroxiredoxin-3 (PRDX3) and may be involved in the transport of PRDX3 from the cytoplasm to its site of function in the mitochondria. Members of this subfamily also show similarity to sorting nexin 15 (SNX15), which contains PX and MIT domains but does not contain a kinase domain. SNXs make up the largest group among PX domain containing proteins. They are involved in regulating membrane traffic and protein sorting in the endosomal system. The PX domain of SNXs binds PIs and targets the protein to PI-enriched membranes. SNX15 plays a role in protein trafficking processes in the endocytic pathway and the trans-Golgi network. The PX domain of SNX15 interacts with the PDGF receptor and is responsible for the membrane association of the protein.

                           10        20        30        40        50        60        70        80
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1564316791   10 IVRFYTVTDPTTHKKGYTVYKVTARIISRKNPEDIQEITVWKRYSDFKKLHQNLWQIHRNLYGQSELFPPFAKAKVFGRF 89
Cdd:cd07287      1 LARFYTVTDPRRHPKGYTVYKVTARIVSRKNPEDVQEIVVWKRYSDFKKLHKDLWQIHKNLCRQSELFPPFAKAKVFGRF 80

                           90       100       110
                   ....*....|....*....|....*....|....*...
gi 1564316791   90 DESVIEKRRQCSEDLLQFSANIPALYGSHYIQDFFKGG 127
Cdd:cd07287     81 DESVIEERRQCAEDLLQFSANIPALYNSSQLEDFFKGG 118

Kunitz domain 1 of hepatocyte growth factor activator inhibitor-1 (HAI-1); This model includes Kunitz domain 1 (KD1) of hepatocyte growth factor activator inhibitor type 1 (HAI1 or HAI-1, also known as Kunitz-type protease inhibitor 1), a membrane-bound multidomain protein essential to the integrity of the basement membrane during placental development. HAI-1 contains an extracellular region and several internal domains that include two Kunitz domains separated in sequence but spatially closed to each other, and their interdomain interactions have evolved to stimulate the inhibitory activity of an integrated Kunitz. KD1, the major inhibitory domain of HAI-1, is involved in auto-inhibition of the extracellular region via steric blockage of its active site in the HAI-1 compact tertiary structure; presence of the target protease causes changes in the HAI-1 structure to an extended conformation. HAI-1 has been shown to inhibit several serine proteases such as matripase, hepsin, trypsin, hepatocyte growth factor activator (HGFA), and prostasin. It is also important in maintaining postnatal homeostasis in many tissues, including keratinization of the epidermis, hair development, colonic epithelium integrity, proliferation and cell fate of neural progenitor cells, and tissue injury and repair. The interaction between HAI-1 and matriptase is critical for tissue morphogenesis and cellular biology. HAI-1:matriptase ratio imbalance results in tumorigenesis; slight overexpression of matriptase relative to HAI-1 causes spontaneous squamous cell carcinoma, a phenotype that can be effectively reversed back to wild type by additional expression of HAI-1, indicating the need for a tight functional relationship between the two to maintain homeostasis. The structures of these domains are similar to those of Kunitz-type proteinase inhibitors such as BPTI (bovine pancreatic trypsin inhibitor), showing an alpha/beta fold with irregular secondary structure stabilized by three disulfide bonds.

                           10        20        30        40        50
                   ....*....|....*....|....*....|....*....|....*....|....*...
gi 1564316791  946 QSERHCLAPKKVGPCRGYFPRWHYNAASKNCEQFYFGGCKENNNNYLSKQECLNACKN 1003
Cdd:cd22623      1 QSELYCLAPKKVGPCRGSFPRWHYNAASGKCEEFVFGGCKGNKNNYLSEEECLSACRG 58

MIT: domain contained within Microtubule Interacting and Trafficking molecules. This MIT domain sub-family is found in sorting nexin 15 and related proteins. The molecular function of the MIT domain is unclear.

                           10        20        30        40        50        60
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*..
gi 1564316791  248 DYLEEASEQIALAVQKEVEQDFAVAFSYYRRGVDLLLQGVQGEVSPSRREAVKRKTAEYLMRAELIS 314
Cdd:cd02677      1 DYLEQAAELIRLALEKEEEGDYEAAFEFYRAGVDLLLKGVQGDSSPERREAVKRKIAEYLKRAEEIL 67

Kunitz/Bovine pancreatic trypsin inhibitor domain; Indicative of a protease inhibitor, usually a serine protease inhibitor. Structure is a disulfide rich alpha+beta fold. BPTI (bovine pancreatic trypsin inhibitor) is an extensively studied model structure. Certain family members are similar to the tick anticoagulant peptide (TAP). This is a highly selective inhibitor of factor Xa in the blood coagulation pathways. TAP molecules are highly dipolar, and are arranged to form a twisted two- stranded antiparallel beta-sheet followed by an alpha helix.

                           10        20        30        40        50
                   ....*....|....*....|....*....|....*....|....*....|..
gi 1564316791  951 CLAPKKVGPCRGYFPRWHYNAASKNCEQFYFGGCKENNNNYLSKQECLNACK 1002
Cdd:pfam00014    2 CSLPPDSGPCKASIPRWYYNPTTGTCEPFTYGGCGGNANNFESLEECESTCR 53

BPTI/Kunitz family of serine protease inhibitors; Serine protease inhibitors. One member of the family is encoded by an alternatively-spliced form of Alzheimer's amyloid beta-protein.

                            10        20        30        40        50
                    ....*....|....*....|....*....|....*....|....*....|.
gi 1564316791  1065 CTDPPVVGPCRASFNRWYYDPLHKKCHRFTYGGCDGNENNFETTDKCMNNC 1115
Cdd:smart00131    3 CLLPPDTGPCGGSIPRYYYDPETGTCEPFTYGGCGGNANNFESLEECERTC 53

MIT (microtubule interacting and transport) domain; The MIT domain forms an asymmetric three-helix bundle and binds ESCRT-III (endosomal sorting complexes required for transport) substrates.

                           10        20        30        40        50        60
                   ....*....|....*....|....*....|....*....|....*....|....*....|....
gi 1564316791  250 LEEASEQIALAVQKEVEQDFAVAFSYYRRGVDLLLQGVQGEVSPSRREAVKRKTAEYLMRAELI 313
Cdd:pfam04212    1 LSKALELVKKAVEEDNAGNYEEALELYKEALDYLLLALKETKNEERRELLRAKIAEYLERAEEL 64

Serine/threonine protein kinase [Signal transduction mechanisms];

                           10        20        30        40        50        60        70        80
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1564316791  771 RIPEALVRSWAADMVMALDALHQEGIICRDLNPSNILLNHAGRVQLTYF--CSWSDVEESCDPNAI--SKMYCAPEV--G 844
Cdd:COG0515    103 PLPPAEALRILAQLAEALAAAHAAGIVHRDIKPANILLTPDGRVKLIDFgiARALGGATLTQTGTVvgTPGYMAPEQarG 182

                           90       100       110       120       130       140
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*...
gi 1564316791  845 GicEETLACDWWSLGALLFELIVGKSLYQCHPAG--IGRHsslnipefVSEEARSLLEQKTDLPDQVR 910
Cdd:COG0515    183 E--PVDPRSDVYSLGVTLYELLTGRPPFDGDSPAelLRAH--------LREPPPPPSELRPDLPPALD 240

protein kinase A catalytic subunit; Provisional

                           10        20        30        40        50        60        70        80
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1564316791  771 RIPEALVRSWAADMVMALDALHQEGIICRDLNPSNILLNHAGRVQLTYFCSWSDVEESCDPNAISKMYCAPEVGGICEET 850
Cdd:PTZ00263   114 RFPNDVAKFYHAELVLAFEYLHSKDIIYRDLKPENLLLDNKGHVKVTDFGFAKKVPDRTFTLCGTPEYLAPEVIQSKGHG 193

                           90       100       110       120       130       140       150
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....
gi 1564316791  851 LACDWWSLGALLFELIVG-KSLYQCHPAGI------GRhssLNIPEFVSEEARSLLEQKTDLPDQVRVSKLVPGVYKFK 922
Cdd:PTZ00263   194 KAVDWWTMGVLLYEFIAGyPPFFDDTPFRIyekilaGR---LKFPNWFDGRARDLVKGLLQTDHTKRLGTLKGGVADVK 269

Low Density Lipoprotein Receptor Class A domain, a cysteine-rich repeat that plays a central role in mammalian cholesterol metabolism; the receptor protein binds LDL and transports it into cells by endocytosis; 7 successive cysteine-rich repeats of about 40 amino acids are present in the N-terminal of this multidomain membrane protein; other homologous domains occur in related receptors, including the very low-density lipoprotein receptor and the LDL receptor-related protein/alpha 2-macroglobulin receptor, and in proteins which are functionally unrelated, such as the C9 component of complement; the binding of calcium is required for in vitro formation of the native disulfide isomer and is necessary in establishing and maintaining the modular structure

                           10        20        30
                   ....*....|....*....|....*....|....*
gi 1564316791 1010 CREDEFECSNGCCVKKEFECDEQQQCSDGSDEQNC 1044
Cdd:cd00112      1 CPPNEFRCANGRCIPSSWVCDGEDDCGDGSDEENC 35

Protein kinase domain;

                           10        20        30        40        50        60        70
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|.
gi 1564316791  838 YCAPEVGGICEETLACDWWSLGALLFELIVGKSLYQCHP-AGIGRH------SSLNIPEFVSEEARSLLEQ 901
Cdd:pfam00069  126 YMAPEVLGGNPYGPKVDVWSLGCILYELLTGKPPFPGINgNEIYELiidqpyAFPELPSNLSEEAKDLLKK 196

Stk1 family PASTA domain-containing Ser/Thr kinase;

                           10        20        30        40
                   ....*....|....*....|....*....|....*....|....*.
gi 1564316791  774 EALvrSWAADMVMALDALHQEGIICRDLNPSNILLNHAGRVQLTYF 819
Cdd:NF033483   108 EAV--EIMIQILSALEHAHRNGIVHRDIKPQNILITKDGRVKVTDF 151

The phosphoinositide binding Phox Homology domain of RPK118-like proteins; The PX domain is a phosphoinositide (PI) binding module present in many proteins with diverse functions such as cell signaling, vesicular trafficking, protein sorting, and lipid modification, among others. Members of this subfamily bear similarity to human RPK118, which contains an N-terminal PX domain, a Microtubule Interacting and Trafficking (MIT) domain, and a kinase domain. RPK118 binds sphingosine kinase, a key enzyme in the synthesis of sphingosine 1-phosphate (SPP), a lipid messenger involved in many cellular events. RPK118 may be involved in transmitting SPP-mediated signaling. It also binds the antioxidant peroxiredoxin-3 (PRDX3) and may be involved in the transport of PRDX3 from the cytoplasm to its site of function in the mitochondria. Members of this subfamily also show similarity to sorting nexin 15 (SNX15), which contains PX and MIT domains but does not contain a kinase domain. SNXs make up the largest group among PX domain containing proteins. They are involved in regulating membrane traffic and protein sorting in the endosomal system. The PX domain of SNXs binds PIs and targets the protein to PI-enriched membranes. SNX15 plays a role in protein trafficking processes in the endocytic pathway and the trans-Golgi network. The PX domain of SNX15 interacts with the PDGF receptor and is responsible for the membrane association of the protein.

                           10        20        30        40        50        60        70        80
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1564316791   10 IVRFYTVTDPTTHKKGYTVYKVTARIISRKNPEDIQEITVWKRYSDFKKLHQNLWQIHRNLYGQSELFPPFAKAKVFGRF 89
Cdd:cd07287      1 LARFYTVTDPRRHPKGYTVYKVTARIVSRKNPEDVQEIVVWKRYSDFKKLHKDLWQIHKNLCRQSELFPPFAKAKVFGRF 80

                           90       100       110
                   ....*....|....*....|....*....|....*...
gi 1564316791   90 DESVIEKRRQCSEDLLQFSANIPALYGSHYIQDFFKGG 127
Cdd:cd07287     81 DESVIEERRQCAEDLLQFSANIPALYNSSQLEDFFKGG 118

The phosphoinositide binding Phox Homology domain of Sorting Nexin 15; The PX domain is a phosphoinositide (PI) binding module present in many proteins with diverse functions. Sorting nexins (SNXs) make up the largest group among PX domain containing proteins. They are involved in regulating membrane traffic and protein sorting in the endosomal system. The PX domain of SNXs binds PIs and targets the protein to PI-enriched membranes. SNXs differ from each other in PI-binding specificity and affinity, and the presence of other protein-protein interaction domains, which help determine subcellular localization and specific function in the endocytic pathway. SNX15 contains an N-terminal PX domain and a C-terminal Microtubule Interacting and Trafficking (MIT) domain. It plays a role in protein trafficking processes in the endocytic pathway and the trans-Golgi network. The PX domain of SNX15 interacts with the PDGF receptor and is responsible for the membrane association of the protein.

                           10        20        30        40        50        60        70        80
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1564316791   12 RFYTVTDPTTHKKGYTVYKVTARIISRKNPEDIQEITVWKRYSDFKKLHQNLWQIHRNLYGQSELFPPFAKAKVFGRFDE 91
Cdd:cd07288      3 RFYSVTDPRTHPKGYTEYKVTAQFISKKQPEDVKEVVVWKRYSDLKKLHGELAYTHRNLFRRQEEFPPFPRAQVFGRFEA 82

                           90       100       110
                   ....*....|....*....|....*....|....*.
gi 1564316791   92 SVIEKRRQCSEDLLQFSANIPALYGSHYIQDFFKGG 127
Cdd:cd07288     83 AVIEERRNAAEAMLLFTVNIPALYNSPQLKEFFRDG 118

Catalytic domain of AGC family Serine/Threonine Kinases; STKs catalyze the transfer of the gamma-phosphoryl group from ATP to serine/threonine residues on protein substrates. AGC kinases regulate many cellular processes including division, growth, survival, metabolism, motility, and differentiation. Many are implicated in the development of various human diseases. Members of this family include cAMP-dependent Protein Kinase (PKA), cGMP-dependent Protein Kinase (PKG), Protein Kinase C (PKC), Protein Kinase B (PKB), G protein-coupled Receptor Kinase (GRK), Serum- and Glucocorticoid-induced Kinase (SGK), and 70 kDa ribosomal Protein S6 Kinase (p70S6K or S6K), among others. AGC kinases share an activation mechanism based on the phosphorylation of up to three sites: the activation loop (A-loop), the hydrophobic motif (HM) and the turn motif. Phosphorylation at the A-loop is required of most AGC kinases, which results in a disorder-to-order transition of the A-loop. The ordered conformation results in the access of substrates and ATP to the active site. A subset of AGC kinases with C-terminal extensions containing the HM also requires phosphorylation at this site. Phosphorylation at the HM allows the C-terminal extension to form an ordered structure that packs into the hydrophobic pocket of the catalytic domain, which then reconfigures the kinase into an active bi-lobed state. In addition, growth factor-activated AGC kinases such as PKB, p70S6K, RSK, MSK, PKC, and SGK, require phosphorylation at the turn motif (also called tail or zipper site), located N-terminal to the HM at the C-terminal extension. The AGC family is part of a larger superfamily that includes the catalytic domains of other STKs, protein tyrosine kinases, RIO kinases, aminoglycoside phosphotransferase, choline kinase, and Phosphoinositide 3-Kinase.

                           10        20        30        40        50        60        70        80
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1564316791  729 MDFVEheevglrskgtGGEqeneevskLFQELDKLAaisldtRIPEALVRSWAADMVMALDALHQEGIICRDLNPSNILL 808
Cdd:cd05123     72 LDYVP-----------GGE--------LFSHLSKEG------RFPEERARFYAAEIVLALEYLHSLGIIYRDLKPENILL 126

                           90       100       110       120       130       140       150       160
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1564316791  809 NHAGRVQLTYFCSWSDVE---ESCDPNAISKMYCAPEVGGICEETLACDWWSLGALLFELIVGKSLYQCHPAGI----GR 881
Cdd:cd05123    127 DSDGHIKLTDFGLAKELSsdgDRTYTFCGTPEYLAPEVLLGKGYGKAVDWWSLGVLLYEMLTGKPPFYAENRKEiyekIL 206

                          170       180
                   ....*....|....*....|
gi 1564316791  882 HSSLNIPEFVSEEARSLLEQ 901
Cdd:cd05123    207 KSPLKFPEYVSPEAKSLISG 226

Catalytic domain of the Serine/Threonine Kinase, RPK118, and similar proteins; STKs catalyze the transfer of the gamma-phosphoryl group from ATP to serine/threonine residues on protein substrates. RPK118 contains an N-terminal Phox homology (PX) domain, a Microtubule Interacting and Trafficking (MIT) domain, and a kinase domain containing a long uncharacterized insert. Also included in the family is human RPK60 (or ribosomal protein S6 kinase-like 1), which also contains MIT and kinase domains but lacks a PX domain. RPK118 binds sphingosine kinase, a key enzyme in the synthesis of sphingosine 1-phosphate (SPP), a lipid messenger involved in many cellular events. RPK118 may be involved in transmitting SPP-mediated signaling. RPK118 also binds the antioxidant peroxiredoxin-3. RPK118 may be involved in the transport of PRDX3 from the cytoplasm to its site of function in the mitochondria. The RPK118-like subfamily is part of a larger superfamily that includes the catalytic domains of other STKs, protein tyrosine kinases, RIO kinases, aminoglycoside phosphotransferase, choline kinase, and phosphoinositide 3-kinase.

                           10        20        30        40        50        60        70        80
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1564316791  347 DELRHYRVLGIIDK----------------GLRKSSACGRVKKTVVPRSVPNMVQLEKYIISEDSIFLLLQYAEGGKLWS 410
Cdd:cd05576      1 EELKAFRVLGVIDKvllvmdtrtqetfilkGLRKSSEYSRERKTIIPRCVPNMVCLRKYIISEESVFLVLQHAEGGKLWS 80

                   ....*..
gi 1564316791  411 HICKYLH 417
Cdd:cd05576     81 YLSKFLN 87

Kunitz-type domain 1 (KD1) of hepatocyte growth factor activator inhibitor type 2 (HAI-2), and similar proteins; This model includes the Kunitz domain 1 (KD1) of hepatocyte growth factor activator inhibitor type 2 (HAI-2 or HAI2, also known as placental bikunin or Kunitz-type protease inhibitor 2). HAI-2 is composed of two Kunitz domains that strongly inhibit many serine proteases with sub-nanomolar affinities. HAI-2 Kunitz domain 1 (KD1) has been found to be the domain responsible for inhibition of hepatocyte growth factor (HGF) activator; activated HGF/scatter factor (HGF/SF) binds to its receptor tyrosine kinase MET to induce dimerization and initiate phosphorylation cascades leading to comprehensive cellular changes that, in the deregulated context of cancer, drive malignant transformation and progression. HAI-2 has been found to be a natural tumor suppressor in renal cell carcinoma, breast cancer and prostate cancer; its loss leads to tumor growth and progression in part due to increased MET signaling. HAI-2 is also a specific substrate for mesotrypsin, which is up-regulated with progression in prostate cancers and shown to contribute to invasion and metastasis; these activities of mesotrypsin may in part be mediated through cleavage and inactivation of HAI-2, resulting in increases in HGF/SF activation and MET signaling. HAI-2 is a physiological inhibitor of hepsin and matriptase, two type II transmembrane serine proteases that, like HGF activator, can convert latent pro-HGF/SF into the two-chain active signaling heterodimer. The structures of these KD1 domains are similar to those of Kunitz-type proteinase inhibitors such as BPTI (bovine pancreatic trypsin inhibitor), showing an alpha/beta fold with irregular secondary structure stabilized by three disulfide bonds.

                           10        20        30        40        50
                   ....*....|....*....|....*....|....*....|....*....|..
gi 1564316791  950 HCLAPKKVGPCRGYFPRWHYNAASKNCEQFYFGGCKENNNNYLSKQECLNAC 1001
Cdd:cd22621      2 FCHLPKVVGRCRASFPRWWYNATSQSCQEFIFGGCKGNLNNFLSEQECLQKC 53

Kunitz/Bovine pancreatic trypsin inhibitor (BPTI) domain; This family contains the Kunitz domain which is a common structural fold found in a family of reversible serine protease inhibitors. This domain is thought to have evolved over 500 million years and is ubiquitous in all kingdoms of life and has been incorporated into many different genes. In general, each domain is encoded by a single exon. Some genes encode proteins with a single Kunitz domain, e.g. bovine pancreatic trypsin inhibitor (BPTI), trophoblast Kunitz domain protein (TKDP), amyloid beta-protein precursor (ABPP), as well as Kunitz-type venom peptides such as dendrotoxin. Genes that encode multiple Kunitz domains include hepatocyte growth factor activator inhibitors HAI1 and HAI2 (two domains), tissue factor pathway inhibitor TFPI1 and TFPI2 (three domains) and Caenorhabditis elegans papilin (eleven domains). In addition, the Kunitz domain has been integrated into multi-domain proteins, e.g. the collagen alpha3(VI), alpha1(VII) and alpha1(XXVIII) chains, WFIKKN1 (containing WAP, Follistatin/Kazal, Immunoglobulin, two Kunitz and NTR domains) and papilin. Furthermore, each domain within a multi-Kunitz domain protein may exhibit different protease activity, such as for the three tandemly repeated domains within both tissue factor pathway inhibitors 1 and 2. The Kunitz domain is a representative of alpha/beta proteins with irregular secondary structure stabilized by three disulfide bonds and presenting three peptide loops that can be varied without introducing much destabilization to the scaffold. Protease inhibitors meet the scaffold criteria in that they are small, stable and capable of evolving the binding activity of exposed peptide loops through targeted randomization to construct combinatorial libraries. Kunitz domain-based scaffolds have been successfully utilized to construct and select a library of protease inhibitors with the potential for therapeutic application.

                           10        20        30        40        50
                   ....*....|....*....|....*....|....*....|....*....|.
gi 1564316791  951 CLAPKKVGPCRGYFPRWHYNAASKNCEQFYFGGCKENNNNYLSKQECLNAC 1001
Cdd:cd00109      1 CLLPPDPGPCRAYFPRWYYNSETGQCEEFIYGGCGGNANNFETKEECEATC 51

Kunitz domain 1 of hepatocyte growth factor activator inhibitor-1 (HAI-1); This model includes Kunitz domain 1 (KD1) of hepatocyte growth factor activator inhibitor type 1 (HAI1 or HAI-1, also known as Kunitz-type protease inhibitor 1), a membrane-bound multidomain protein essential to the integrity of the basement membrane during placental development. HAI-1 contains an extracellular region and several internal domains that include two Kunitz domains separated in sequence but spatially closed to each other, and their interdomain interactions have evolved to stimulate the inhibitory activity of an integrated Kunitz. KD1, the major inhibitory domain of HAI-1, is involved in auto-inhibition of the extracellular region via steric blockage of its active site in the HAI-1 compact tertiary structure; presence of the target protease causes changes in the HAI-1 structure to an extended conformation. HAI-1 has been shown to inhibit several serine proteases such as matripase, hepsin, trypsin, hepatocyte growth factor activator (HGFA), and prostasin. It is also important in maintaining postnatal homeostasis in many tissues, including keratinization of the epidermis, hair development, colonic epithelium integrity, proliferation and cell fate of neural progenitor cells, and tissue injury and repair. The interaction between HAI-1 and matriptase is critical for tissue morphogenesis and cellular biology. HAI-1:matriptase ratio imbalance results in tumorigenesis; slight overexpression of matriptase relative to HAI-1 causes spontaneous squamous cell carcinoma, a phenotype that can be effectively reversed back to wild type by additional expression of HAI-1, indicating the need for a tight functional relationship between the two to maintain homeostasis. The structures of these domains are similar to those of Kunitz-type proteinase inhibitors such as BPTI (bovine pancreatic trypsin inhibitor), showing an alpha/beta fold with irregular secondary structure stabilized by three disulfide bonds.

                           10        20        30        40        50
                   ....*....|....*....|....*....|....*....|....*....|....*
gi 1564316791 1064 HCTDPPVVGPCRASFNRWYYDPLHKKCHRFTYGGCDGNENNFETTDKCMNNCSGV 1118
Cdd:cd22623      5 YCLAPKKVGPCRGSFPRWHYNAASGKCEEFVFGGCKGNKNNYLSEEECLSACRGV 59

Kunitz/Bovine pancreatic trypsin inhibitor domain; Indicative of a protease inhibitor, usually a serine protease inhibitor. Structure is a disulfide rich alpha+beta fold. BPTI (bovine pancreatic trypsin inhibitor) is an extensively studied model structure. Certain family members are similar to the tick anticoagulant peptide (TAP). This is a highly selective inhibitor of factor Xa in the blood coagulation pathways. TAP molecules are highly dipolar, and are arranged to form a twisted two- stranded antiparallel beta-sheet followed by an alpha helix.

                           10        20        30        40        50
                   ....*....|....*....|....*....|....*....|....*....|..
gi 1564316791  951 CLAPKKVGPCRGYFPRWHYNAASKNCEQFYFGGCKENNNNYLSKQECLNACK 1002
Cdd:pfam00014    2 CSLPPDSGPCKASIPRWYYNPTTGTCEPFTYGGCGGNANNFESLEECESTCR 53

BPTI/Kunitz family of serine protease inhibitors; Serine protease inhibitors. One member of the family is encoded by an alternatively-spliced form of Alzheimer's amyloid beta-protein.

                            10        20        30        40        50
                    ....*....|....*....|....*....|....*....|....*....|.
gi 1564316791  1065 CTDPPVVGPCRASFNRWYYDPLHKKCHRFTYGGCDGNENNFETTDKCMNNC 1115
Cdd:smart00131    3 CLLPPDTGPCGGSIPRYYYDPETGTCEPFTYGGCGGNANNFESLEECERTC 53

Catalytic domain of the Serine/Threonine Kinase, 70 kDa ribosomal protein S6 kinase; STKs catalyze the transfer of the gamma-phosphoryl group from ATP to serine/threonine residues on protein substrates. p70S6K (or S6K) contains only one catalytic kinase domain, unlike p90 ribosomal S6 kinases (RSKs). It acts as a downstream effector of the STK mTOR (mammalian Target of Rapamycin) and plays a role in the regulation of the translation machinery during protein synthesis. p70S6K also plays a pivotal role in regulating cell size and glucose homeostasis. Its targets include S6, the translation initiation factor eIF3, and the insulin receptor substrate IRS-1, among others. Mammals contain two isoforms of p70S6K, named S6K1 and S6K2 (or S6K-beta). The p70S6K subfamily is part of a larger superfamily that includes the catalytic domains of other protein STKs, protein tyrosine kinases, RIO kinases, aminoglycoside phosphotransferase, choline kinase, and phosphoinositide 3-kinase.

                           10        20        30        40        50        60        70        80
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1564316791  773 PEALVRSWAADMVMALDALHQEGIICRDLNPSNILLNHAGRVQLTYF--CswsdvEESCDPNAISKMYC------APEVG 844
Cdd:cd05584     98 MEDTACFYLAEITLALGHLHSLGIIYRDLKPENILLDAQGHVKLTDFglC-----KESIHDGTVTHTFCgtieymAPEIL 172

                           90       100       110       120       130       140
                   ....*....|....*....|....*....|....*....|....*....|....*....|...
gi 1564316791  845 GICEETLACDWWSLGALLFELIVGKSLYqchpAGIGR--------HSSLNIPEFVSEEARSLL 899
Cdd:cd05584    173 TRSGHGKAVDWWSLGALMYDMLTGAPPF----TAENRkktidkilKGKLNLPPYLTNEARDLL 231

Catalytic domain of Protein Kinases; PKs catalyze the transfer of the gamma-phosphoryl group from ATP to serine/threonine or tyrosine residues on protein substrates. PKs make up a large family of serine/threonine kinases (STKs), protein tyrosine kinases (PTKs), and dual-specificity PKs that phosphorylate both serine/threonine and tyrosine residues of target proteins. Majority of protein phosphorylation occurs on serine residues while only 1% occurs on tyrosine residues. Protein phosphorylation is a mechanism by which a wide variety of cellular proteins, such as enzymes and membrane channels, are reversibly regulated in response to certain stimuli. PKs often function as components of signal transduction pathways in which one kinase activates a second kinase, which in turn, may act on other kinases; this sequential action transmits a signal from the cell surface to target proteins, which results in cellular responses. The PK family is one of the largest known protein families with more than 100 homologous yeast enzymes and more than 500 human proteins. A fraction of PK family members are pseudokinases that lack crucial residues for catalytic activity. The mutiplicity of kinases allows for specific regulation according to substrate, tissue distribution, and cellular localization. PKs regulate many cellular processes including proliferation, division, differentiation, motility, survival, metabolism, cell-cycle progression, cytoskeletal rearrangement, immunity, and neuronal functions. Many kinases are implicated in the development of various human diseases including different types of cancer. The PK family is part of a larger superfamily that includes the catalytic domains of RIO kinases, aminoglycoside phosphotransferase, choline kinase, phosphoinositide 3-kinase (PI3K), and actin-fragmin kinase.

                           10        20        30        40        50        60        70        80
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1564316791  756 LFQELDKLAAisldtRIPEALVRSWAADMVMALDALHQEGIICRDLNPSNILLNHAGRVQLTYFCSWSDVEESCD----- 830
Cdd:cd00180     78 LKDLLKENKG-----PLSEEEALSILRQLLSALEYLHSNGIIHRDLKPENILLDSDGTVKLADFGLAKDLDSDDSllktt 152

                           90       100       110
                   ....*....|....*....|....*....|....*
gi 1564316791  831 PNAISKMYCAPEVGGICEETLACDWWSLGALLFEL 865
Cdd:cd00180    153 GGTTPPYYAPPELLGGRYYGPKVDIWSLGVILYEL 187

Kunitz-type domain 2 (KD2) of hepatocyte growth factor activator inhibitor type 2 (HAI-2), and similar proteins; This model includes Kunitz domain 2 (KD2) of hepatocyte growth factor activator inhibitor type 2 (HAI-2 or HAI2, also known as placental bikunin or Kunitz-type protease inhibitor 2). HAI-2 is composed of two Kunitz domains that strongly inhibit many serine proteases with sub-nanomolar affinities. It has been found to be a natural tumor suppressor in renal cell carcinoma, breast cancer and prostate cancer, the loss of which leads to tumor growth and progression attributable at least in part to increased MET signaling. HAI-2 is a specific substrate of mesotrypsin which is up-regulated with progression in prostate cancers and shown to contribute to invasion and metastasis; these activities of mesotrypsin may in part be mediated through cleavage and inactivation of HAI-2, resulting in increases in hetatocyte growth factor/scatter factor (HGF/SF) activation and MET signaling. HAI-2 is a physiological inhibitor of hepsin and matriptase, two type II transmembrane serine proteases that, like HGF activator, can convert latent pro-HGF/SF into the two-chain active signaling heterodimer. KD2 is similar to KD1, whose structure is similar to those of Kunitz-type proteinase inhibitors such as BPTI (bovine pancreatic trypsin inhibitor), showing an alpha/beta fold with irregular secondary structure stabilized by three disulfide bonds.

                           10        20        30        40        50
                   ....*....|....*....|....*....|....*....|....*....|..
gi 1564316791  950 HCLAPKKVGPCRGYFPRWHYNAASKNCEQFYFGGCKENNNNYLSKQECLNAC 1001
Cdd:cd22622      2 YCAAPRVTGPCRAAFPRWYYDPESQSCKEFIYGGCRGNKNNYLSEEECMDRC 53

Kunitz domain 1 (KD1) of tissue factor pathway inhibitor 2 (TFPI2) and similar proteins; This model represents the Kunitz-type domain 1 (KD1) of tissue factor pathway inhibitor 2 (TFPI2 or TFPI-2) and similar proteins. TFPI2 exhibits inhibitory activity primarily toward trypsin, plasmin, and factor VIIa (FVIIa)/tissue factor (TF) via its KD1. It is believed to be the major inhibitor of plasmin in the extracellular matrix (ECM) but has little inhibitory activity toward urokinase-type plasminogen activator, tissue-type plasminogen activator, or thrombin. TFPI2 specifically inhibits the proteases via the P1 arginine residue in KD1. The TFPI2 domains KD2 and KD3 appear to have no discernible inhibitory activity and may serve to bind to nearby proteins to localize TFPI2 in the ECM. Structure studies of KD1 complexed with proteases may help in the development of specific and potent KD1 domain protein that may have a large pharmacologic impact in preventing tumor metastasis, retinal degeneration, and degradation of collagen in the ECM. The structure of this domain is similar to that of Kunitz-type proteinase inhibitors such as BPTI (bovine pancreatic trypsin inhibitor), showing an alpha/beta fold with irregular secondary structure stabilized by three disulfide bonds.

                           10        20        30        40        50
                   ....*....|....*....|....*....|....*....|....*....|..
gi 1564316791 1065 CTDPPVVGPCRASFNRWYYDPLHKKCHRFTYGGCDGNENNFETTDKCMNNCS 1116
Cdd:cd22616      5 CLLPPDEGPCRALIPRYYYDRYTQTCREFSYGGCEGNANNFESLEDCEKTCW 56

Kunitz domain 1 (KD1) of tissue factor pathway inhibitor 2 (TFPI2) and similar proteins; This model represents the Kunitz-type domain 1 (KD1) of tissue factor pathway inhibitor 2 (TFPI2 or TFPI-2) and similar proteins. TFPI2 exhibits inhibitory activity primarily toward trypsin, plasmin, and factor VIIa (FVIIa)/tissue factor (TF) via its KD1. It is believed to be the major inhibitor of plasmin in the extracellular matrix (ECM) but has little inhibitory activity toward urokinase-type plasminogen activator, tissue-type plasminogen activator, or thrombin. TFPI2 specifically inhibits the proteases via the P1 arginine residue in KD1. The TFPI2 domains KD2 and KD3 appear to have no discernible inhibitory activity and may serve to bind to nearby proteins to localize TFPI2 in the ECM. Structure studies of KD1 complexed with proteases may help in the development of specific and potent KD1 domain protein that may have a large pharmacologic impact in preventing tumor metastasis, retinal degeneration, and degradation of collagen in the ECM. The structure of this domain is similar to that of Kunitz-type proteinase inhibitors such as BPTI (bovine pancreatic trypsin inhibitor), showing an alpha/beta fold with irregular secondary structure stabilized by three disulfide bonds.

                           10        20        30        40        50
                   ....*....|....*....|....*....|....*....|....*....|.
gi 1564316791  951 CLAPKKVGPCRGYFPRWHYNAASKNCEQFYFGGCKENNNNYLSKQECLNAC 1001
Cdd:cd22616      5 CLLPPDEGPCRALIPRYYYDRYTQTCREFSYGGCEGNANNFESLEDCEKTC 55

third Kunitz domain of Carboxypeptidase Inhibitor SmCI and similar domains; This group includes Sabellastarte magnifica carboxypeptidase inhibitor (SmCI), Bombyx mori cocoon shell-associated trypsin inhibitor (CSTI), Bombus terrestris Kunitz-type serine protease inhibitor Bt-KTI, and similar domains. SmCI is a tri-domain BPTI-Kunitz inhibitor capable of inhibiting serine proteases and A-like metallocarboxypeptidases. While the BPTI-Kunitz family of proteins includes voltage gated channel blockers and inhibitors of serine proteases, SmCI is the only BPTI-Kunitz protein capable of inhibiting metallocarboxypeptidases. Binding studies show that SmCI is able to bind three trypsin molecules under saturating conditions, but only one elastase interacts with the inhibitor. Additionally, SmCI can bind serine proteases and carboxypeptidases at the same time (at least in the ratio 1:1:1), thus becoming the first protease inhibitor that simultaneously blocks these two mechanistic classes of enzymes. CSTI and Bt-KTI are single Kunitz domain proteins that inhibit trypsin; in addition, Bt-KTI also inhibits plasmin. This model contains the third Kunitz domain of SmCI which has a structure similar to those of Kunitz-type proteinase inhibitors such as BPTI (bovine pancreatic trypsin inhibitor), showing an alpha/beta fold with irregular secondary structure stabilized by three disulfide bonds.

                           10        20        30        40        50
                   ....*....|....*....|....*....|....*....|....*....|..
gi 1564316791  950 HCLAPKKVGPCRGYFPRWHYNAASKNCEQFYFGGCKENNNNYLSKQECLNAC 1001
Cdd:cd22603      2 DCLLPSETGPCKGSFPRYYYDKETGKCKEFIYGGCQGNANNFETKEECERAC 53

Catalytic domain of the Serine/Threonine kinase, Unc-51-like kinase 4; STKs catalyze the transfer of the gamma-phosphoryl group from ATP to serine/threonine residues on protein substrates. ULK4 is a functionally uncharacterized kinase that shows similarity to ATG1/ULKs. The ATG1/ULK complex is conserved from yeast to humans and it plays a critical role in the initiation of autophagy, the intracellular system that leads to the lysosomal degradation of cellular components and their recycling into basic metabolic units. The ULK4 subfamily is part of a larger superfamily that includes the catalytic domains of other protein STKs, protein tyrosine kinases, RIO kinases, aminoglycoside phosphotransferase, choline kinase, and phosphoinositide 3-kinase.

                           10        20        30        40        50        60        70        80
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1564316791  761 DKLAAISLDTRIPEALVRSWAADMVMALDALHQEGIICRDLNPSNILLNHAGRVQLTYFC--------------SWSDVE 826
Cdd:cd14010     80 DLETLLRQDGNLPESSVRKFGRDLVRGLHYIHSKGIIYCDLKPSNILLDGNGTLKLSDFGlarregeilkelfgQFSDEG 159

                           90       100       110       120       130       140       150       160
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1564316791  827 ESCDPNAISKM-----YCAPEV--GGicEETLACDWWSLGALLFELIVGKslyqchpagigrhsslniPEFVSEEARSLL 899
Cdd:cd14010    160 NVNKVSKKQAKrgtpyYMAPELfqGG--VHSFASDLWALGCVLYEMFTGK------------------PPFVAESFTELV 219

                   ..
gi 1564316791  900 EQ 901
Cdd:cd14010    220 EK 221

Pseudocerastes persicus trypsin inhibitor (PPTI), Kunitz-type serine protease inhibitor bitisilin, and similar proteins; This group contains Pseudocerastes persicus trypsin inhibitor (PPTI), Bitis gabonica Kunitz-type serine protease inhibitor bitisilin-1 (BG-11), -2 (BG-15) and -3 (two-Kunitz protease inhibitor), Oxyuranus scutellatus scutellatus taicatoxin, and serine protease inhibitor component (TSPI, also called venom protease inhibitor 1 or venom protease inhibitor 2), among others. PPTI from P. persicus venom shows inhibitory effect against trypsin proteolytic activity and has similarities to dendrotoxins (DTXs), with corresponding functionally important residues. Studies have shown the ability of PPTI to inhibit voltage-gated potassium channels, and consequently have dual functionality. Bitilisins 1, 2, and 3 are serine protease inhibitors expressed in snake venom glands; bitsilin-3 consists of two Kunitz protease inhibitor domains. Taicatoxin inhibits trypsin, tissue kallikrein, elastase, plasmin and factor Xa, and is also known to block the voltage-dependent L-type calcium channels from the heart, and the small conductance calcium-activated potassium channels (KCa) in chromaffin cells and in the brain. The structures of these Kunitz-type proteins are similar to other Kunitz-type proteinase inhibitors such as BPTI (bovine pancreatic trypsin inhibitor), showing an alpha/beta fold with irregular secondary structure stabilized by three disulfide bonds.

                           10        20        30        40        50
                   ....*....|....*....|....*....|....*....|....*....|...
gi 1564316791  949 RHCLAPKKVGPCRGYFPRWHYNAASKNCEQFYFGGCKENNNNYLSKQECLNAC 1001
Cdd:cd22608      2 KFCYLPADPGPCKAYIPRFYYNSASNKCQQFIYGGCKGNANNFETKDECRYTC 54

Catalytic domain of Microtubule-associated serine/threonine (MAST) kinase-like proteins; STKs catalyze the transfer of the gamma-phosphoryl group from ATP to serine/threonine residues on protein substrates. This subfamily includes MAST kinases, MAST-like (MASTL) kinases (also called greatwall kinase or Gwl), and fungal kinases with similarity to Saccharomyces cerevisiae Rim15 and Schizosaccharomyces pombe cek1. MAST kinases contain an N-terminal domain of unknown function, a central catalytic domain, and a C-terminal PDZ domain that mediates protein-protein interactions. MASTL kinases carry only a catalytic domain which contains a long insert relative to other kinases. The fungal kinases in this subfamily harbor other domains in addition to a central catalytic domain, which like in MASTL, also contains an insert relative to MAST kinases. Rim15 contains a C-terminal signal receiver (REC) domain while cek1 contains an N-terminal PAS domain. MAST kinases are cytoskeletal associated kinases of unknown function that are also expressed at neuromuscular junctions and postsynaptic densities. MASTL/Gwl is involved in the regulation of mitotic entry, mRNA stabilization, and DNA checkpoint recovery. The fungal proteins Rim15 and cek1 are involved in the regulation of meiosis and mitosis, respectively. The MAST-like kinase subfamily is part of a larger superfamily that includes the catalytic domains of other STKs, protein tyrosine kinases, RIO kinases, aminoglycoside phosphotransferase, choline kinase, and phosphoinositide 3-kinase.

                           10        20        30        40        50        60        70        80
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1564316791  773 PEALVRSWAADMVMALDALHQEGIICRDLNPSNILLNHAGRVQLTYF-------------CSWSDVEESCDPNAISKM-- 837
Cdd:cd05579     91 DEDVARIYIAEIVLALEYLHSHGIIHRDLKPDNILIDANGHLKLTDFglskvglvrrqikLSIQKKSNGAPEKEDRRIvg 170

                           90       100       110
                   ....*....|....*....|....*....|....
gi 1564316791  838 ---YCAPEVGGICEETLACDWWSLGALLFELIVG 868
Cdd:cd05579    171 tpdYLAPEILLGQGHGKTVDWWSLGVILYEFLVG 204

second Kunitz domain of WAP, Kazal, immunoglobulin, Kunitz and NTR domain-containing proteins; This subfamily includes WAP, Kazal, immunoglobulin, Kunitz and NTR domain-containing protein 1 (WFIKKN1, WFKN1), WFIKKN2 (WFKN2), and similar proteins. WFIKKN proteins are protease inhibitors that contain two distinct Kunitz-type protease inhibitor domains. They may have serine protease- and metalloprotease-inhibitor activity. This model represents the second Kunitz (KU2) domain, which has been shown to inhibit trypsin, but not chymotrypsin, elastase, plasmin, pancreatic kallikrein, lung tryptase, plasma kallikrein, thrombin, urokinase or tissue plasminogen activator. However, the inhibition constant of this domain for bovine trypsin is about five orders of magnitudes lower than that of bovine pancreatic trypsin inhibitor (BPTI) for trypsin. This could be due to unfavorable side-chain conformation of a tryptophan at P2' site which is incompatible with a trypsin complex; typical trypsin inhibitors of the Kunitz family feature a tyrosine residue or other less bulky residues at this site. The structure of KU2 is similar to those of Kunitz-type proteinase inhibitors such as BPTI (bovine pancreatic trypsin inhibitor), showing an alpha/beta fold with irregular secondary structure stabilized by three disulfide bonds.

                           10        20        30        40        50
                   ....*....|....*....|....*....|....*....|....*....|.
gi 1564316791 1065 CTDPPVVGPCRASFNRWYYDPLHKKCHRFTYGGCDGNENNFETTDKCMNNC 1115
Cdd:cd22606      2 CSLPAVQGPCKAWEPRWAYNSLLKQCQSFVYGGCEGNENNFESKEACEDAC 52

Kunitz protease inhibitor (KPI) domain 2 (KPI-2 or K2) of tissue factor pathway inhibitor (TFPI); This model represents the second Kunitz-type domain (K2 or KPI-2) of tissue factor pathway inhibitor (TFPI or TFPI1), also known as extrinsic pathway inhibitor (EPI) or lipoprotein-associated coagulation inhibitor (LACI). TFPI down-regulates the extrinsic coagulation pathway via inhibition of activated factor X (FXa or Xa) and FVIIa (VIIa). It inhibits activated FXa via a "slow-tight binding mechanism", i.e. rapid formation of a loose FXa-TFPI complex that then slowly isomerizes to a tight FXa-TFPI* complex. Subsequent inhibition of FVIIa is facilitated by the presence of tissue factor (TF) and FXa, which together rapidly and efficiently form a quaternary FXa-TFPI-TF-FVIIa complex in which the activity of FXa and FVIIa are inhibited. TFPI consists of 3 Kunitz-type protease inhibitor (KPI) domains in a tandem arrangement; the K2 domain is exposed on functionally active TFPI pools in circulation in blood, in platelets, and attached to the endothelium. While the K1 (or KPI-1) domain of TFPI has been shown to bind and inhibit FVIIa, the K2 domain inhibits FXa by binding directly to the active site and forming a FXa:TFPI complex. A close interaction between the TFPI K2 domain and the FXa active site is essential for the FXa inhibitory action of TFPI and for the formation of an inactive TF/FVIIa/FXa/TFPI complex which then prevents FXa generation. Thus, blockage of K2 would prevent TFPI binding to both FXa and FVIIa/TF, and fully abolish TFPI inhibition of the coagulation cascade. The structure of the K2 domain is similar to those of Kunitz-type proteinase inhibitors such as BPTI (bovine pancreatic trypsin inhibitor), showing an alpha/beta fold with irregular secondary structure stabilized by three disulfide bonds.

                           10        20        30        40        50
                   ....*....|....*....|....*....|....*....|....*....|.
gi 1564316791  951 CLAPKKVGPCRGYFPRWHYNAASKNCEQFYFGGCKENNNNYLSKQECLNAC 1001
Cdd:cd22614      5 CFLEEDPGICRGLITRYFYNNQSKQCERFKYGGCLGNQNNFESLEECQNTC 55

bovine pancreatic trypsin inhibitor; This model contains bovine pancreatic trypsin inhibitor (BPTI, also known as pancreatic Kunitz inhibitor, aprotinin, or trypsin-kallikrein inhibitor), a small protein that inhibits the action of the trypsin, and is thus a member of the serine protease family of inhibitors. This class of enzymes contains conserved cysteine residues that form 3 disulfide bonds to stabilize the three-dimensional structure. BPTI has a relatively broad specificity, inhibiting trypsin as well as chymotrypsin, and elastase-like serine (pro)enzymes capable of very different primary specificity. It reacts rapidly with serine proteases to form stable complexes, but the enzyme:inhibitor complex formation may involve several intermediates corresponding to discrete reaction steps. Furthermore, BPTI inhibits the nitric oxide synthase type-I and -II action, and impairs K+ transport by Ca2+-activated K+ channels. Clinically, BPTI is used in certain surgical interventions, such as cardiopulmonary surgery and orthotopic liver transplantation since it significantly reduces hemorrhagic complications.

                           10        20        30        40        50
                   ....*....|....*....|....*....|....*....|....*....|.
gi 1564316791 1065 CTDPPVVGPCRASFNRWYYDPLHKKCHRFTYGGCDGNENNFETTDKCMNNC 1115
Cdd:cd22592      2 CLEPPYTGPCKARIIRYFYNAKSGLCETFVYGGCRAKRNNFLSAEDCMRTC 52

Catalytic domain of the Serine/Threonine Kinase, G protein-coupled Receptor Kinase; STKs catalyze the transfer of the gamma-phosphoryl group from ATP to serine/threonine residues on protein substrates. GRKs phosphorylate and regulate G protein-coupled receptors (GPCRs), the largest superfamily of cell surface receptors, which regulate some part of nearly all physiological functions. Phosphorylated GPCRs bind to arrestins, which prevents further G protein signaling despite the presence of activating ligand. GRKs play important roles in the cardiovascular, immune, respiratory, skeletal, and nervous systems. They contain a central catalytic domain, flanked by N- and C-terminal extensions. The N-terminus contains an RGS (regulator of G protein signaling) homology (RH) domain and several motifs. The C-terminus diverges among different groups of GRKs. There are seven types of GRKs, named GRK1 to GRK7, which are subdivided into three main groups: visual (GRK1/7); beta-adrenergic receptor kinases (GRK2/3); and GRK4-like (GRK4/5/6). Expression of GRK2/3/5/6 is widespread while GRK1/4/7 show a limited tissue distribution. The substrate spectrum of the widely expressed GRKs partially overlaps. The GRK subfamily is part of a larger superfamily that includes the catalytic domains of other STKs, protein tyrosine kinases, RIO kinases, aminoglycoside phosphotransferase, choline kinase, and phosphoinositide 3-kinase.

                           10        20        30        40        50        60        70        80
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 1564316791  773 PEALVRSWAADMVMALDALHQEGIICRDLNPSNILLNHAGRVQLtyfcswSDVEESCDPNAISKM--------YCAPEVg 844
Cdd:cd05577     93 SEARAIFYAAEIICGLEHLHNRFIVYRDLKPENILLDDHGHVRI------SDLGLAVEFKGGKKIkgrvgthgYMAPEV- 165