2hdv
Crystal structure of the Src Homology-2 domain of the adapter protein SH2-B
Structural highlights
FunctionSH2B1_MOUSE Adapter protein for several members of the tyrosine kinase receptor family. Involved in multiple signaling pathways mediated by Janus kinase (JAK) and receptor tyrosine kinases, including the receptors of insulin (INS), insulin-like growth factor I (IGF1), nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), glial cell line-derived neurotrophic factor (GDNF), platelet-derived growth factor (PDGF) and fibroblast growth factors (FGFs). In growth hormone (GH) signaling, autophosphorylated ('Tyr-813') JAK2 recruits SH2B1, which in turn is phosphorylated by JAK2 on tyrosine residues. These phosphotyrosines form potential binding sites for other signaling proteins. GH also promotes serine/threonine phosphorylation of SH2B1 and these phosphorylated residues may serve to recruit other proteins to the GHR-JAK2-SH2B1 complexes, such as RAC1. In leptin (LEP) signaling, binds to and potentiates the activation of JAK2 by globally enhancing downstream pathways. In response to leptin, binds simultaneously to both, JAK2 and IRS1 or IRS2, thus mediating formation of a complex of JAK2, SH2B1 and IRS1 or IRS2. Mediates tyrosine phosphorylation of IRS1 and IRS2, resulting in activation of the PI 3-kinase pathway. Acts as positive regulator of NGF-mediated activation of the Akt/Forkhead pathway; prolongs NGF-induced phosphorylation of AKT1 on 'Ser-473' and AKT1 enzymatic activity. Enhances the kinase activity of the cytokine receptor-associated tyrosine kinase JAK2 and of other receptor tyrosine kinases, such as FGFR3 and NTRK1. For JAK2, the mechanism seems to involve dimerization of both, SH2B1 and JAK2. Enhances RET phosphorylation and kinase activity (By similarity). Isoforms seem to be differentially involved in IGF-I and PDGF-induced mitogenesis, according the order: isoform 3 > isoform 4 > isoform 1 > isoform 2.[1] [2] [3] [4] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedSH2-B, APS, and Lnk constitute a family of adapter proteins that modulate signaling by protein tyrosine kinases. These adapters contain an N-terminal dimerization region, a pleckstrin homology domain, and a C-terminal Src homology-2 (SH2) domain. SH2-B is recruited via its SH2 domain to various protein tyrosine kinases, including Janus kinase-2 (Jak2) and the insulin receptor. Here, we present the crystal structure at 2.35 A resolution of the SH2 domain of SH2-B in complex with a phosphopeptide representing the SH2-B recruitment site in Jak2 (pTyr813). The structure reveals a canonical SH2 domain-phosphopeptide binding mode, but with specific recognition of a glutamate at the +1 position relative to phosphotyrosine, in addition to recognition of a hydrophobic residue at the +3 position. Biochemical studies of SH2-B and APS demonstrate that, although the SH2 domains of these two adapter proteins share 79% sequence identity, the SH2-B SH2 domain binds preferentially to Jak2, whereas the APS SH2 domain has higher affinity for the insulin receptor. This differential specificity is attributable to the difference in the oligomeric states of the two SH2 domains: monomeric for SH2-B and dimeric for APS. Structural basis for phosphotyrosine recognition by the Src homology-2 domains of the adapter proteins SH2-B and APS.,Hu J, Hubbard SR J Mol Biol. 2006 Aug 4;361(1):69-79. Epub 2006 Jun 16. PMID:16824542[5] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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