Src Homology 3 domain superfamily; Src Homology 3 (SH3) domains are protein interaction domains that bind proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. Thus, they are referred to as proline-recognition domains (PRDs). SH3 domains are less selective and show more diverse specificity compared to other PRDs. They have been shown to bind peptide sequences that lack the PxxP motif; examples include the PxxDY motif of Eps8 and the RKxxYxxY sequence in SKAP55. SH3 domain containing proteins play versatile and diverse roles in the cell, including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies, among others. Many members of this superfamily are adaptor proteins that associate with a number of protein partners, facilitating complex formation and signal transduction.

                          10        20        30        40        50        60
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*..
gi 2217391247  19 RSLYVRALFDYDRTRDSCLPSQGLSFSYGDILHVINASDDEWWQARLVTPHGESEQIGVIPSKKRVE 85
Cdd:cd12029     1 RSLYVRALFDYDRTRDSCLPSQGLSFSYGDILHVINASDDEWWQARLVTPHGESEQIGVIPSKKRVE 67

Guanylate kinase homologues; Active enzymes catalyze ATP-dependent phosphorylation of GMP to GDP. Structure resembles that of adenylate kinase. So-called membrane-associated guanylate kinase homologues (MAGUKs) do not possess guanylate kinase activities; instead at least some possess protein-binding functions.

                           10        20        30        40        50        60        70        80
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 2217391247  186 KDRVNDDLISEFPHKFGSCVPHTTRPRRDNEVDGQDYHFVvSREQMEKDIQDNKFIEAGQFNDNLYGTSIQSVRAVAERG 265
Cdd:smart00072   5 KGTLLAELIQEIPDAFERVVSHTTRPPRPGEVNGVDYHFV-SKEEFEDDIKSGLFLEWGEYEGNYYGTSKETIRQVAEKG 83

                           90       100       110       120       130       140       150       160
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 2217391247  266 KHCILDVSGNAIKRLQQAQLYPIAIFIKPKSIEALMEMNRRQTYEQANKIYDKAMKLEQEFGEY--FTAIVQGDSLEEIY 343
Cdd:smart00072  84 KHCLLDIDPQGVKQLRKAQLYPIVIFIAPPSSEELERRLRQRGTETSERIQKRLAAAQKEAQEYhlFDYVIVNDDLEDAY 163

                          170
                   ....*....|
gi 2217391247  344 NKIKQIIEDQ 353
Cdd:smart00072 164 EELKEILEAE 173

guanylate kinase

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 2217391247 177 RPVIILGPM---KDRVNDDLISEFPHKFGSCVPHTTRPRRDNEVDGQDYHFVvSREQMEKDIQDNKFIEAGQFNDNLYGT 253
Cdd:PLN02772  136 KPIVISGPSgvgKGTLISMLMKEFPSMFGFSVSHTTRAPREMEKDGVHYHFT-ERSVMEKEIKDGKFLEFASVHGNLYGT 214

                          90       100       110       120       130       140       150       160
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 2217391247 254 SIQSVRAVAERGKHCILDVSGNAIKRLQQAQLYPIAIFIKPKSIEAL---MEMNRRQTYEQANKIYDKAmKLEQEFGE-- 328
Cdd:PLN02772  215 SIEAVEVVTDSGKRCILDIDVQGARSVRASSLEAIFIFICPPSMEELekrLRARGTETEEQIQKRLRNA-EAELEQGKss 293

                         170       180       190
                  ....*....|....*....|....*....|....*...
gi 2217391247 329 -YFTAIVQGDSLEEIYNKIKQIIE-DQSGHYIWVPSPE 364
Cdd:PLN02772  294 gIFDHILYNDNLEECYKNLKKLLGlDGLAAVNGVEAPE 331

guanylate kinase; Members of this family are the enzyme guanylate kinase, also called GMP kinase. This enzyme transfers a phosphate from ATP to GMP, yielding ADP and GDP. [Purines, pyrimidines, nucleosides, and nucleotides, Nucleotide and nucleoside interconversions]

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 2217391247 177 RPVIILGPM---KDRVNDDLISEFPHKFGScVPHTTRPRRDNEVDGQDYHFVvSREQMEKDIQDNKFIEAGQFNDNLYGT 253
Cdd:TIGR03263   1 LLIVISGPSgagKSTLVKALLEEDPNLKFS-ISATTRKPRPGEVDGVDYFFV-SKEEFEEMIKAGEFLEWAEVHGNYYGT 78

                          90       100       110       120       130       140       150       160
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 2217391247 254 SIQSVRAVAERGKHCIL--DVSG-NAIKRlqqaqLYP--IAIFIKPKSIEALME--MNRRQ-TYEQANKIYDKAMKlEQE 325
Cdd:TIGR03263  79 PKSPVEEALAAGKDVLLeiDVQGaRQVKK-----KFPdaVSIFILPPSLEELERrlRKRGTdSEEVIERRLAKAKK-EIA 152

                         170       180
                  ....*....|....*....|....*
gi 2217391247 326 FGEYFTAIVQGDSLEEIYNKIKQII 350
Cdd:TIGR03263 153 HADEFDYVIVNDDLEKAVEELKSII 177

Src homology 3 domains; Src homology 3 (SH3) domains bind to target proteins through sequences containing proline and hydrophobic amino acids. Pro-containing polypeptides may bind to SH3 domains in 2 different binding orientations.

                           10        20        30        40        50
                   ....*....|....*....|....*....|....*....|....*....|....*....
gi 2217391247   22 YVRALFDYDRTRDsclpsQGLSFSYGDILHVINASDDEWWQARLvtphgESEQIGVIPS 80
Cdd:smart00326   4 QVRALYDYTAQDP-----DELSFKKGDIITVLEKSDDGWWKGRL-----GRGKEGLFPS 52

Guanylate kinase homologues; Active enzymes catalyze ATP-dependent phosphorylation of GMP to GDP. Structure resembles that of adenylate kinase. So-called membrane-associated guanylate kinase homologues (MAGUKs) do not possess guanylate kinase activities; instead at least some possess protein-binding functions.

                           10        20        30        40        50        60        70        80
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 2217391247  186 KDRVNDDLISEFPHKFGSCVPHTTRPRRDNEVDGQDYHFVvSREQMEKDIQDNKFIEAGQFNDNLYGTSIQSVRAVAERG 265
Cdd:smart00072   5 KGTLLAELIQEIPDAFERVVSHTTRPPRPGEVNGVDYHFV-SKEEFEDDIKSGLFLEWGEYEGNYYGTSKETIRQVAEKG 83

                           90       100       110       120       130       140       150       160
                   ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 2217391247  266 KHCILDVSGNAIKRLQQAQLYPIAIFIKPKSIEALMEMNRRQTYEQANKIYDKAMKLEQEFGEY--FTAIVQGDSLEEIY 343
Cdd:smart00072  84 KHCLLDIDPQGVKQLRKAQLYPIVIFIAPPSSEELERRLRQRGTETSERIQKRLAAAQKEAQEYhlFDYVIVNDDLEDAY 163

                          170
                   ....*....|
gi 2217391247  344 NKIKQIIEDQ 353
Cdd:smart00072 164 EELKEILEAE 173

Src Homology 3 domain of Disks large homolog proteins; The DLG-like proteins are scaffolding proteins that cluster at synapses and are also called PSD (postsynaptic density)-95 proteins or SAPs (synapse-associated proteins). They play important roles in synaptic development and plasticity, cell polarity, migration and proliferation. They are members of the MAGUK (membrane-associated guanylate kinase) protein family, which is characterized by the presence of a core of three domains: PDZ, SH3, and guanylate kinase (GuK). The GuK domain in MAGUK proteins is enzymatically inactive; instead, the domain mediates protein-protein interactions and associates intramolecularly with the SH3 domain. DLG-like proteins contain three PDZ domains and varying N-terminal regions. All DLG proteins exist as alternatively-spliced isoforms. Vertebrates contain four DLG proteins from different genes, called DLG1-4. DLG4 and DLG2 are found predominantly at postsynaptic sites and they mediate surface ion channel and receptor clustering. DLG3 is found axons and some presynaptic terminals. DLG1 interacts with AMPA-type glutamate receptors and is critical in their maturation and delivery to synapses. The SH3 domain of DLG4 binds and clusters the kainate subgroup of glutamate receptors via two proline-rich sequences in their C-terminal tail. It also binds AKAP79/150 (A-kinase anchoring protein). SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

                          10        20        30        40        50        60
                  ....*....|....*....|....*....|....*....|....*....|....*....|.
gi 2217391247  22 YVRALFDYDRTRDSCLPSQGLSFSYGDILHVINASDDEWWQARLVTPHGESEQIGVIPSKK 82
Cdd:cd11861     1 YVRALFDYDPSRDSGLPSQGLSFKFGDILHVTNASDDEWWQARRVTPNGEEEEVGVIPSKR 61

Src Homology 3 domain of Disks Large homolog 1; DLG1, also called synapse-associated protein 97 (SAP97), is a scaffolding protein that clusters at synapses and plays an important role in synaptic development and plasticity. DLG1 plays roles in regulating cell polarity, proliferation, migration, and cycle progression. It interacts with AMPA-type glutamate receptors and is critical in their maturation and delivery to synapses. It also interacts with PKCalpha and promotes wound healing. DLG1 is a member of the MAGUK (membrane-associated guanylate kinase) protein family, which is characterized by the presence of a core of three domains: PDZ, SH3, and guanylate kinase (GuK). The GuK domain in MAGUK proteins is enzymatically inactive; instead, the domain mediates protein-protein interactions and associates intramolecularly with the SH3 domain. DLG1 contains three PDZ domains. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

                          10        20        30        40        50        60
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*..
gi 2217391247  19 RSLYVRALFDYDRTRDSCLPSQGLSFSYGDILHVINASDDEWWQARLVTPHGESEQIGVIPSKKRVE 85
Cdd:cd12031     1 RSLYVRALFDYDKTKDSGLPSQGLNFKFGDILHVVNASDDEWWQARQVTADGESEEIGVIPSKRRVE 67

Guanosine monophosphate kinase (GMPK, EC 2.7.4.8), also known as guanylate kinase (GKase), catalyzes the reversible phosphoryl transfer from adenosine triphosphate (ATP) to guanosine monophosphate (GMP) to yield adenosine diphosphate (ADP) and guanosine diphosphate (GDP). It plays an essential role in the biosynthesis of guanosine triphosphate (GTP). This enzyme is also important for the activation of some antiviral and anticancer agents, such as acyclovir, ganciclovir, carbovir, and thiopurines.

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 2217391247 178 PVIILGPM---KDRVNDDLISEFPHKFGSCVPHTTRPRRDNEVDGQDYHFVvSREQMEKDIQDNKFIEAGQFNDNLYGTS 254
Cdd:cd00071     1 LIVLSGPSgvgKSTLLKRLLEEFDPNFGFSVSHTTRKPRPGEVDGVDYHFV-SKEEFERLIENGEFLEWAEFHGNYYGTS 79

                          90       100       110       120
                  ....*....|....*....|....*....|....*....|
gi 2217391247 255 IQSVRAVAERGKHCILDVSGNAIKRLQQAQLYPIAIFIKP 294
Cdd:cd00071    80 KAAVEEALAEGKIVILEIDVQGARQVKKSYPDAVSIFILP 119

Src Homology 3 domain of Disks Large homolog 4; DLG4, also called postsynaptic density-95 (PSD95) or synapse-associated protein 90 (SAP90), is a scaffolding protein that clusters at synapses and plays an important role in synaptic development and plasticity. It is responsible for the membrane clustering and retention of many transporters and receptors such as potassium channels and PMCA4b, a P-type ion transport ATPase, among others. DLG4 is a member of the MAGUK (membrane-associated guanylate kinase) protein family, which is characterized by the presence of a core of three domains: PDZ, SH3, and guanylate kinase (GuK). The GuK domain in MAGUK proteins is enzymatically inactive; instead, the domain mediates protein-protein interactions and associates intramolecularly with the SH3 domain. DLG4 contains three PDZ domains. The SH3 domain of DLG4 binds and clusters the kainate subgroup of glutamate receptors via two proline-rich sequences in their C-terminal tail. It also binds AKAP79/150 (A-kinase anchoring protein). SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

                          10        20        30        40        50        60
                  ....*....|....*....|....*....|....*....|....*....|....*....|....
gi 2217391247  22 YVRALFDYDRTRDSCLPSQGLSFSYGDILHVINASDDEWWQARLVTPHGESEQIGVIPSKKRVE 85
Cdd:cd12030     3 YIRALFDYDKTKDCGFLSQALSFRFGDVLHVIDAGDEEWWQARRVHSDSETEEIGFIPSKRRVE 66

guanylate kinase; Provisional

                          10        20        30        40        50        60        70        80
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 2217391247 205 VPHTTRPRRDNEVDGQDYHFVvSREQMEKDIQDNKFIEAGQFNDNLYGTSIQSVRAVAERGKHCIL--DVSGnAikrLQQ 282
Cdd:PRK00300   36 VSATTRAPRPGEVDGVDYFFV-SKEEFEEMIENGEFLEWAEVFGNYYGTPRSPVEEALAAGKDVLLeiDWQG-A---RQV 110

                          90       100       110       120       130       140       150       160
                  ....*....|....*....|....*....|....*....|....*....|....*....|....*....|....*....|
gi 2217391247 283 AQLYP--IAIFIKPKSIEALME-MNRRQTyEQANKIydkAMKLEQ------EFGEYFTAIVQgDSLEEIYNKIKQIIEDQ 353
Cdd:PRK00300  111 KKKMPdaVSIFILPPSLEELERrLRGRGT-DSEEVI---ARRLAKareeiaHASEYDYVIVN-DDLDTALEELKAIIRAE 185

Src Homology 3 domain of Membrane Protein, Palmitoylated 1 (or MAGUK p55 subfamily member 1)-like proteins; This subfamily includes MPP1, CASK (Calcium/calmodulin-dependent Serine protein Kinase), Caenorhabditis elegans lin-2, and similar proteins. MPP1 and CASK are scaffolding proteins from the MAGUK (membrane-associated guanylate kinase) protein family, which is characterized by the presence of a core of three domains: PDZ, SH3, and guanylate kinase (GuK). In addition, they also have the Hook (Protein 4.1 Binding) motif in between the SH3 and GuK domains. The GuK domain in MAGUK proteins is enzymatically inactive; instead, the domain mediates protein-protein interactions and associates intramolecularly with the SH3 domain. CASK and lin-2 also contain an N-terminal calmodulin-dependent kinase (CaMK)-like domain and two L27 domains. MPP1 is ubiquitously-expressed and plays roles in regulating neutrophil polarity, cell shape, hair cell development, and neural development and patterning of the retina. CASK is highly expressed in the mammalian nervous system and plays roles in synaptic protein targeting, neural development, and gene expression regulation. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

                          10        20        30        40        50        60
                  ....*....|....*....|....*....|....*....|....*....|....*....|.
gi 2217391247  22 YVRALFDYDRTRDSCLPSQ--GLSFSYGDILHVINASDDEWWQARLvtPHGESEQIGVIPS 80
Cdd:cd12035     1 YVRAQFDYDPSKDDLIPCQqaGIAFKTGDILQIISKDDHNWWQARK--PGASKEPAGLIPS 59

Src Homology 3 domain of Membrane Protein, Palmitoylated 5 (or MAGUK p55 subfamily member 5); MPP5, also called PALS1 (Protein associated with Lin7) or Nagie oko protein in zebrafish or Stardust in Drosophila, is a scaffolding protein which associates with Crumbs homolog 1 (CRB1), CRB2, or CRB3 through its PDZ domain and with PALS1-associated tight junction protein (PATJ) or multi-PDZ domain protein 1 (MUPP1) through its L27 domain. The resulting tri-protein complexes are core proteins of the Crumb complex, which localizes at tight junctions or subapical regions, and is involved in the maintenance of apical-basal polarity in epithelial cells and the morphogenesis and function of photoreceptor cells. MPP5 is critical for the proper stratification of the retina and is also expressed in T lymphocytes where it is important for TCR-mediated activation of NFkB. Drosophila Stardust exists in several isoforms, some of which show opposing functions in photoreceptor cells, which suggests that the relative ratio of different Crumbs complexes regulates photoreceptor homeostasis. MPP5 contains two L27 domains followed by the core of three domains characteristic of MAGUK (membrane-associated guanylate kinase) proteins: PDZ, SH3, and guanylate kinase (GuK). In addition, it also contains the Hook (Protein 4.1 Binding) motif in between the SH3 and GuK domains. The GuK domain in MAGUK proteins is enzymatically inactive; instead, the domain mediates protein-protein interactions and associates intramolecularly with the SH3 domain. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

                          10        20        30        40        50        60
                  ....*....|....*....|....*....|....*....|....*....|....*....|..
gi 2217391247  22 YVRALFDYDRTRDSCLPSQ--GLSFSYGDILHVINASDDEWWQARLVTPHGESEQIGVIPSK 81
Cdd:cd12036     1 HVRAHFDYDPEDDPYIPCRelGLSFQKGDILHVISQEDPNWWQAYREGEEDNQSLAGLIPSK 62

Src Homology 3 domain of Calcium/calmodulin-dependent Serine protein Kinase; CASK is a scaffolding protein that is highly expressed in the mammalian nervous system and plays roles in synaptic protein targeting, neural development, and gene expression regulation. CASK interacts with many different binding partners including parkin, neurexin, syndecans, calcium channel proteins, caskin, among others, to perform specific functions in different subcellular locations. Disruption of the CASK gene in mice results in neonatal lethality while mutations in the human gene have been associated with X-linked mental retardation. Drosophila CASK is associated with both pre- and postsynaptic membranes and is crucial in synaptic transmission and vesicle cycling. CASK contains an N-terminal calmodulin-dependent kinase (CaMK)-like domain, two L27 domains, followed by the core of three domains characteristic of MAGUK (membrane-associated guanylate kinase) proteins: PDZ, SH3, and guanylate kinase (GuK). In addition, it also contains the Hook (Protein 4.1 Binding) motif in between the SH3 and GuK domains. The GuK domain in MAGUK proteins is enzymatically inactive; instead, the domain mediates protein-protein interactions and associates intramolecularly with the SH3 domain. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

                          10        20        30        40        50        60
                  ....*....|....*....|....*....|....*....|....*....|....*....|.
gi 2217391247  22 YVRALFDYDRTRDSCLPSQ--GLSFSYGDILHVINASDDEWWQARLVTPHGESEqiGVIPS 80
Cdd:cd12081     1 YVRAQFEYDPLKDDLIPCKqaGIRFRVGDILQIISKDDHNWWQAKLENSKNGTA--GLIPS 59

Src homology 3 domains; Src homology 3 (SH3) domains bind to target proteins through sequences containing proline and hydrophobic amino acids. Pro-containing polypeptides may bind to SH3 domains in 2 different binding orientations.

                           10        20        30        40        50
                   ....*....|....*....|....*....|....*....|....*....|....*....
gi 2217391247   22 YVRALFDYDRTRDsclpsQGLSFSYGDILHVINASDDEWWQARLvtphgESEQIGVIPS 80
Cdd:smart00326   4 QVRALYDYTAQDP-----DELSFKKGDIITVLEKSDDGWWKGRL-----GRGKEGLFPS 52

Src Homology 3 domain of Membrane Protein, Palmitoylated 3 (or MAGUK p55 subfamily member 3); MPP3 is a scaffolding protein that colocalizes with MPP5 and CRB1 at the subdpical region adjacent to adherens junctions and may function in photoreceptor polarity. It interacts with some nectins and regulates their trafficking and processing. Nectins are cell-cell adhesion proteins involved in the establishment apical-basal polarity at cell adhesion sites. It is one of seven vertebrate homologs of the Drosophila Stardust protein, which is required in establishing cell polarity, and it contains two L27 domains followed by the core of three domains characteristic of MAGUK (membrane-associated guanylate kinase) proteins: PDZ, SH3, and guanylate kinase (GuK). The GuK domain in MAGUK proteins is enzymatically inactive; instead, the domain mediates protein-protein interactions and associates intramolecularly with the SH3 domain. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

                          10        20        30        40        50        60
                  ....*....|....*....|....*....|....*....|....*....|....*....|....
gi 2217391247  22 YVRALFDYDRTRDSCLPSQ--GLSFSYGDILHVINASDDEWWQARLVtphGESE-QIGVIPSKK 82
Cdd:cd12039     1 FMRALFDYNPYEDRAIPCQeaGLPFKRRDILEVVSQDDPTWWQAKRV---GDTNlRAGLIPSKQ 61

Src Homology 3 domain superfamily; Src Homology 3 (SH3) domains are protein interaction domains that bind proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. Thus, they are referred to as proline-recognition domains (PRDs). SH3 domains are less selective and show more diverse specificity compared to other PRDs. They have been shown to bind peptide sequences that lack the PxxP motif; examples include the PxxDY motif of Eps8 and the RKxxYxxY sequence in SKAP55. SH3 domain containing proteins play versatile and diverse roles in the cell, including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies, among others. Many members of this superfamily are adaptor proteins that associate with a number of protein partners, facilitating complex formation and signal transduction.

                          10        20        30        40        50
                  ....*....|....*....|....*....|....*....|....*....|....*....
gi 2217391247  22 YVRALFDYDRTRDsclpsQGLSFSYGDILHVINASDDEWWQARLvtphgESEQIGVIPS 80
Cdd:cd00174     1 YARALYDYEAQDD-----DELSFKKGDIITVLEKDDDGWWEGEL-----NGGREGLFPA 49

Src Homology 3 domain of Membrane Protein, Palmitoylated 4 (or MAGUK p55 subfamily member 4); MPP4, also called Disks Large homolog 6 (DLG6) or Amyotrophic lateral sclerosis 2 chromosomal region candidate gene 5 protein (ALS2CR5), is a retina-specific scaffolding protein that plays a role in organizing presynaptic protein complexes in the photoreceptor synapse, where it localizes to the plasma membrane. It is required in the proper localization of calcium ATPases and for maintenance of calcium homeostasis. MPP4 is one of seven vertebrate homologs of the Drosophila Stardust protein, which is required in establishing cell polarity, and it contains two L27 domains followed by the core of three domains characteristic of MAGUK (membrane-associated guanylate kinase) proteins: PDZ, SH3, and guanylate kinase (GuK). The GuK domain in MAGUK proteins is enzymatically inactive; instead, the domain mediates protein-protein interactions and associates intramolecularly with the SH3 domain. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

                          10        20        30        40        50        60
                  ....*....|....*....|....*....|....*....|....*....|....*....|.
gi 2217391247  22 YVRALFDYDRTRDSCLP--SQGLSFSYGDILHVINASDDEWWQARLVTPHGESEqiGVIPS 80
Cdd:cd12034     1 YVRAMVDYWPQQDPSIPcaDAGLPFRKGDILQIVDQNDSLWWQARKLSDLAACA--GLIPS 59

SH3 domain; SH3 (Src homology 3) domains are often indicative of a protein involved in signal transduction related to cytoskeletal organization. First described in the Src cytoplasmic tyrosine kinase. The structure is a partly opened beta barrel.

                          10        20        30        40        50
                  ....*....|....*....|....*....|....*....|....*....|....*..
gi 2217391247  24 RALFDYDRTRDSclpsqGLSFSYGDILHVINASDDEWWQARLVTphgesEQIGVIPS 80
Cdd:pfam00018   1 VALYDYTAQEPD-----ELSFKKGDIIIVLEKSEDGWWKGRNKG-----GKEGLIPS 47

Src Homology 3 domain of metazoan osteoclast stimulating factor 1; OSTF1, also named OSF or SH3P2, is a signaling protein containing SH3 and ankyrin-repeat domains. It acts through a Src-related pathway to enhance the formation of osteoclasts and bone resorption. It also acts as a negative regulator of cell motility. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

                          10        20        30        40        50
                  ....*....|....*....|....*....|....*....|....*....|....*...
gi 2217391247  23 VRALFDYDRTRDsclpsQGLSFSYGDILHVINASDDEWWQARLvtphgeSEQIGVIPS 80
Cdd:cd11772     2 FRALYDYEAQHP-----DELSFEEGDLLYISDKSDPNWWKATC------GGKTGLIPS 48

C-terminal Src homology 3 domain of Growth factor receptor-bound protein 2; GRB2 is a critical signaling molecule that regulates the Ras pathway by linking tyrosine kinases to the Ras guanine nucleotide releasing protein Sos (son of sevenless), which converts Ras to the active GTP-bound state. It is ubiquitously expressed in all tissues throughout development and is important in cell cycle progression, motility, morphogenesis, and angiogenesis. In lymphocytes, GRB2 is associated with antigen receptor signaling components. GRB2 contains an N-terminal SH3 domain, a central SH2 domain, and a C-terminal SH3 domain. The C-terminal SH3 domain of GRB2 binds to Gab2 (Grb2-associated binder 2) through epitopes containing RxxK motifs, as well as to the proline-rich C-terminus of FGRF2. SH3 domains are protein interaction domains that typically bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

                          10        20        30        40        50
                  ....*....|....*....|....*....|....*....|....*....|....*....
gi 2217391247  22 YVRALFDYDRTRDSclpsqGLSFSYGDILHVINASDDEWWQArlvTPHGeseQIGVIPS 80
Cdd:cd11949     1 YVQALFDFDPQEDG-----ELGFRRGDFIEVMDNSDPNWWKG---ACHG---QTGMFPR 48

Src homology 3 domain of Signal Transducing Adaptor Molecule 1; STAM1 is part of the endosomal sorting complex required for transport (ESCRT-0) and is involved in sorting ubiquitinated cargo proteins from the endosome. It may also be involved in the regulation of IL2 and GM-CSF mediated signaling, and has been implicated in neural cell survival. STAMs were discovered as proteins that are highly phosphorylated following cytokine and growth factor stimulation. They function in cytokine signaling and surface receptor degradation, as well as regulate Golgi morphology. They associate with many proteins including Jak2 and Jak3 tyrosine kinases, Hrs, AMSH, and UBPY. STAM adaptor proteins contain VHS (Vps27, Hrs, STAM homology), ubiquitin interacting (UIM), and SH3 domains. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

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gi 2217391247  23 VRALFDYDRTRDSclpsqGLSFSYGDILHVINASDDEWWQARlvTPHGeseqIGVIPS 80
Cdd:cd11964     3 VRAIYDFEAAEDN-----ELTFKAGDIITILDDSDPNWWKGE--TPQG----TGLFPS 49

C-terminal Src homology 3 domain of Growth factor receptor-bound protein 2 (GRB2) and related proteins; This family includes the adaptor protein GRB2 and related proteins including Drosophila melanogaster Downstream of receptor kinase (DRK), Caenorhabditis elegans Sex muscle abnormal protein 5 (Sem-5), GRB2-related adaptor protein (GRAP), GRAP2, and similar proteins. Family members contain an N-terminal SH3 domain, a central SH2 domain, and a C-terminal SH3 domain. GRB2/Sem-5/DRK is a critical signaling molecule that regulates the Ras pathway by linking tyrosine kinases to the Ras guanine nucleotide releasing protein Sos (son of sevenless), which converts Ras to the active GTP-bound state. GRAP2 plays an important role in T cell receptor (TCR) signaling by promoting the formation of the SLP-76:LAT complex, which couples the TCR to the Ras pathway. GRAP acts as a negative regulator of T cell receptor (TCR)-induced lymphocyte proliferation by downregulating the signaling to the Ras/ERK pathway. The C-terminal SH3 domains (SH3c) of GRB2 and GRAP2 have been shown to bind to classical PxxP motif ligands, as well as to non-classical motifs. GRB2 SH3c binds Gab2 (Grb2-associated binder 2) through epitopes containing RxxK motifs, while the SH3c of GRAP2 binds to the phosphatase-like protein HD-PTP via a RxxxxK motif. SH3 domains are protein interaction domains that typically bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

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gi 2217391247  22 YVRALFDYDRTRdsclPSQgLSFSYGDILHVINASDDEWWQARL 65
Cdd:cd11805     1 RVQALYDFNPQE----PGE-LEFRRGDIITVLDSSDPDWWKGEL 39

Src homology 3 domain of Abl Interactor proteins; Abl interactor (Abi) proteins are adaptor proteins serving as binding partners and substrates of Abl tyrosine kinases. They are involved in regulating actin cytoskeletal reorganization and play important roles in membrane-ruffling, endocytosis, cell motility, and cell migration. They localize to sites of actin polymerization in epithelial adherens junction and immune synapses, as well as to the leading edge of lamellipodia. Vertebrates contain two Abi proteins, Abi1 and Abi2. Abi1 displays a wide expression pattern while Abi2 is highly expressed in the eye and brain. Abi proteins contain a homeobox homology domain, a proline-rich region, and a SH3 domain. The SH3 domain of Abi binds to a PxxP motif in Abl. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

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gi 2217391247  22 YVRALFDYDRTRDSclpsqGLSFSYGDILHVINASDDEWWQ 62
Cdd:cd11826     1 KVVALYDYTADKDD-----ELSFQEGDIIYVTKKNDDGWYE 36

Src Homology 3 domain of Sdc25/Cdc25 guanine nucleotide exchange factors; This subfamily is composed of the Saccharomyces cerevisiae guanine nucleotide exchange factors (GEFs) Sdc25 and Cdc25, and similar proteins. These GEFs regulate Ras by stimulating the GDP/GTP exchange on Ras. Cdc25 is involved in the Ras/PKA pathway that plays an important role in the regulation of metabolism, stress responses, and proliferation, depending on available nutrients and conditions. Proteins in this subfamily contain an N-terminal SH3 domain as well as REM (Ras exchanger motif) and RasGEF domains at the C-terminus. SH3 domains bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs; they play a role in the regulation of enzymes by intramolecular interactions, changing the subcellular localization of signal pathway components and mediate multiprotein complex assemblies.

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gi 2217391247  22 YVRALFDYDRTRDSCLpsqglSFSYGDILHVINASDDEWW 61
Cdd:cd11883     1 VVVALYDFTPKSKNQL-----SFKAGDIIYVLNKDPSGWW 35

Src Homology 3 domain of Voltage-dependent L-type calcium channel subunit beta4; The beta4 subunit of voltage-dependent calcium channels (Ca(V)s) is one of four beta subunits present in vertebrates. It is the only beta subunit expressed in the cochlea and is highly expressed in the brain, predominantly in the cerebellum. Ca(V)s are multi-protein complexes that regulate the entry of calcium into cells. They impact muscle contraction, neuronal migration, hormone and neurotransmitter release, and the activation of calcium-dependent signaling pathways. They are composed of four subunits: alpha1, alpha2delta, beta, and gamma. The beta subunit is a soluble and intracellular protein that interacts with the transmembrane alpha1 subunit. It facilitates the trafficking and proper localization of the alpha1 subunit to the cellular plasma membrane. Vertebrates contain four different beta subunits from distinct genes (beta1-4); each exists as multiple splice variants. All are expressed in the brain while other tissues show more specific expression patterns. The beta subunits show similarity to MAGUK (membrane-associated guanylate kinase) proteins in that they contain SH3 and inactive guanylate kinase (GuK) domains; however, they do not appear to contain a PDZ domain. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

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gi 2217391247  34 DSCLPSQGLSFSYGDILHVINASDDEWWQARLVTphgESEQIGVIPSKKRVE 85
Cdd:cd12043    20 DVPVPGTAISFDAKDFLHIKEKYNNDWWIGRLVK---EGCEIGFIPSPLRLE 68

Fifth Src homology 3 domain (or SH3E) of Intersectin; Intersectins (ITSNs) are adaptor proteins that function in exo- and endocytosis, actin cytoskeletal reorganization, and signal transduction. They are essential for initiating clathrin-coated pit formation. They bind to many proteins through their multidomain structure and facilitate the assembly of multimeric complexes. Vertebrates contain two ITSN proteins, ITSN1 and ITSN2, which exist in alternatively spliced short and long isoforms. The short isoforms contain two Eps15 homology domains (EH1 and EH2), a coiled-coil region and five SH3 domains (SH3A-E), while the long isoforms, in addition, contain RhoGEF (also called Dbl-homologous or DH), Pleckstrin homology (PH) and C2 domains. ITSN1 and ITSN2 are both widely expressed, with variations depending on tissue type and stage of development. The fifth SH3 domain (or SH3E) of ITSN1 has been shown to bind many protein partners including SGIP1, Sos1, dynamin1/2, CIN85, c-Cbl, SHIP2, N-WASP, and synaptojanin-1, among others. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

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gi 2217391247  23 VRALFDYDRTRDSclpsqGLSFSYGDILHVINASDDEWWQARLvtphgeSEQIGVIPS 80
Cdd:cd11840     2 VIALFPYTAQNED-----ELSFQKGDIINVLSKDDPDWWRGEL------NGQTGLFPS 48

Src homology 3 domain of Yes Protein Tyrosine Kinase; Yes (or c-Yes) is a member of the Src subfamily of proteins, which are cytoplasmic (or non-receptor) PTKs. c-Yes kinase is the cellular homolog of the oncogenic protein (v-Yes) encoded by the Yamaguchi 73 and Esh sarcoma viruses. It displays functional overlap with other Src subfamily members, particularly Src. It also shows some unique functions such as binding to occludins, transmembrane proteins that regulate extracellular interactions in tight junctions. Yes also associates with a number of proteins in different cell types that Src does not interact with, like JAK2 and gp130 in pre-adipocytes, and Pyk2 in treated pulmonary vein endothelial cells. Although the biological function of Yes remains unclear, it appears to have a role in regulating cell-cell interactions and vesicle trafficking in polarized cells. Src kinases contain an N-terminal SH4 domain with a myristoylation site, followed by SH3 and SH2 domains, a tyr kinase domain, and a regulatory C-terminal region containing a conserved tyr. They are activated by autophosphorylation at the tyr kinase domain, but are negatively regulated by phosphorylation at the C-terminal tyr by Csk (C-terminal Src Kinase). The SH3 domain of Src kinases contributes to substrate recruitment by binding adaptor proteins/substrates, and regulation of kinase activity through an intramolecular interaction. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

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gi 2217391247  25 ALFDYD-RTRDSclpsqgLSFSYGDILHVINASDDEWWQARLVTPhGESeqiGVIPS 80
Cdd:cd12007     5 ALYDYEaRTTED------LSFKKGERFQIINNTEGDWWEARSIAT-GKN---GYIPS 51

Src homology 3 domain of High osmolarity signaling protein Sho1p; Sho1p (or Sho1), also called SSU81 (Suppressor of SUA8-1 mutation), is a yeast membrane protein that regulates adaptation to high salt conditions by activating the HOG (high-osmolarity glycerol) pathway. High salt concentrations lead to the localization to the membrane of the MAPKK Pbs2, which is then activated by the MAPKK Ste11 and in turn, activates the MAPK Hog1. Pbs2 is localized to the membrane though the interaction of its PxxP motif with the SH3 domain of Sho1p. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

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gi 2217391247  23 VRALFDYDRTRDSclPSQgLSFSYGDILHVINASdDEWWQARlvTPHGEseqIGVIPS 80
Cdd:cd11855     2 ARALYPYDASPDD--PNE-LSFEKGEILEVSDTS-GKWWQAR--KSNGE---TGICPS 50

C-terminal Src homology 3 domain of GRB2-related adaptor protein 2; GRAP2 is also called GADS (GRB2-related adapter downstream of Shc), GrpL, GRB2L, Mona, or GRID (Grb2-related protein with insert domain). It is expressed specifically in the hematopoietic system. It plays an important role in T cell receptor (TCR) signaling by promoting the formation of the SLP-76:LAT complex, which couples the TCR to the Ras pathway. It also has roles in antigen-receptor and tyrosine kinase mediated signaling. GRAP2 is unique from other GRB2-like adaptor proteins in that it can be regulated by caspase cleavage. It contains an N-terminal SH3 domain, a central SH2 domain, and a C-terminal SH3 domain. The C-terminal SH3 domain of GRAP2 binds to different motifs found in substrate peptides including the typical PxxP motif in hematopoietic progenitor kinase 1 (HPK1), the RxxK motif in SLP-76 and HPK1, and the RxxxxK motif in phosphatase-like protein HD-PTP. SH3 domains are protein interaction domains that typically bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

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gi 2217391247  23 VRALFDYDRTRDSclpsqGLSFSYGDILHVINASDDEWWQARLvtphgeSEQIGVIPS 80
Cdd:cd11950     2 VRALYDFEALEDD-----ELGFNSGDVIEVLDSSNPSWWKGRL------HGKLGLFPA 48

Src homology 3 domain of ARHGEF9-like Rho guanine nucleotide exchange factors; Members of this family contain a SH3 domain followed by RhoGEF (also called Dbl-homologous or DH) and Pleckstrin Homology (PH) domains. They include the Rho guanine nucleotide exchange factors ARHGEF9, ASEF (also called ARHGEF4), ASEF2, and similar proteins. GEFs activate small GTPases by exchanging bound GDP for free GTP. ARHGEF9 specifically activates Cdc42, while both ASEF and ASEF2 can activate Rac1 and Cdc42. ARHGEF9 is highly expressed in the brain and it interacts with gephyrin, a postsynaptic protein associated with GABA and glycine receptors. ASEF plays a role in angiogenesis and cell migration. ASEF2 is important in cell migration and adhesion dynamics. ASEF exists in an autoinhibited form and is activated upon binding of the tumor suppressor APC (adenomatous polyposis coli), leading to the activation of Rac1 or Cdc42. In its autoinhibited form, the SH3 domain of ASEF forms an extensive interface with the DH and PH domains, blocking the Rac binding site. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

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gi 2217391247  22 YVRALFDYdRTRDSclpsQGLSFSYGDILHVINASDDEWWQARLVTPHG 70
Cdd:cd11828     1 LAEALWDH-VTMDP----EELGFKAGDVIEVLDMSDKDWWWGSIRDEEG 44

Second Src Homology 3 domain of FCH and double SH3 domains protein 2; FCHSD2 has a domain structure consisting of an N-terminal F-BAR (FES-CIP4 Homology and Bin/Amphiphysin/Rvs), two SH3, and C-terminal proline-rich domains. It has only been characterized in silico and its function is unknown. SH3 domains are protein interaction domains that bind to proline-rich ligands with moderate affinity and selectivity, preferentially to PxxP motifs. They play versatile and diverse roles in the cell including the regulation of enzymes, changing the subcellular localization of signaling pathway components, and mediating the formation of multiprotein complex assemblies.

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gi 2217391247  22 YVRALFDYDRTRDsclpsQGLSFSYGDILHVIN---ASDDEWWQARLvtphgeSEQIGVIPS 80
Cdd:cd11894     1 FVKALYDYEGQTD-----DELSFPEGAIIRILNkenQDDDGFWEGEF------NGRIGVFPS 51

Third Src Homology 3 domain of Nck adaptor proteins; This group contains the third SH3 domain of Nck, the first SH3 domain of Caenorhabditis elegans Ced-2 (Cell death abnormality protein 2), and similar domains. Nck adaptor proteins regulate actin cytoskeleton dynamics by linking proline-rich effector molecules to protein tyrosine kinases and phosphorylated signaling intermediates. They contain three SH3 domains and a C-terminal SH2 domain. They function downstream of the PDGFbeta receptor and are involved in Rho GTPase signaling and actin dynamics. Vertebrates contain two Nck adaptor proteins: Nck1 (also called Nckalpha) and Nck2 (also called Nckbeta or Growth factor receptor-bound protein 4, Grb4), which show partly overlapping functions but also bind distinct targets. Their SH3 domains are involved in recruiting downstream effector molecules, such as the N-WASP/Arp2/3 complex, which when activated induces actin polymerization that results in the production of pedestals, or protrusions of the plasma membrane. The third SH3 domain of Nck appears to prefer ligands with a PxAPxR motif. SH3 domains are protein interaction domains that usually bind to proline-rich ligands with moderate affinity and selectivity, preferentially a PxxP motif. Ced-2 is a cell corpse engulfment protein that interacts with Ced-5 in a pathway that regulates the activation of Ced-10, a Rac small GTPase.

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gi 2217391247  23 VRALFDYDRTRDsclpsQGLSFSYGDILHVIN--ASDDEWWQARlvtphGESEQIGVIPS 80
Cdd:cd11767     2 VVALYPFTGEND-----EELSFEKGERLEIIEkpEDDPDWWKAR-----NALGTTGLVPR 51