4g1e
Crystal structure of integrin alpha V beta 3 with coil-coiled tag.
Structural highlights
FunctionITAV_HUMAN The alpha-V integrins are receptors for vitronectin, cytotactin, fibronectin, fibrinogen, laminin, matrix metalloproteinase-2, osteopontin, osteomodulin, prothrombin, thrombospondin and vWF. They recognize the sequence R-G-D in a wide array of ligands. In case of HIV-1 infection, the interaction with extracellular viral Tat protein seems to enhance angiogenesis in Kaposi's sarcoma lesions. Publication Abstract from PubMedMany questions about the significance of structural features of integrin alpha(V)beta(3) with respect to its mechanism of activation remain. We have determined and re-refined crystal structures of the alpha(V)beta(3) ectodomain linked to C-terminal coiled coils (alpha(V)beta(3)-AB) and four transmembrane (TM) residues in each subunit (alpha(V)beta(3)-1TM), respectively. The alpha(V) and beta(3) subunits with four and eight extracellular domains, respectively, are bent at knees between the integrin headpiece and lower legs, and the headpiece has the closed, low-affinity conformation. The structures differ in the occupancy of three metal-binding sites in the betaI domain. Occupancy appears to be related to the pH of crystallization, rather than to the physiologic regulation of ligand binding at the central, metal ion-dependent adhesion site. No electron density was observed for TM residues and much of the alpha(V) linker. alpha(V)beta(3)-AB and alpha(V)beta(3)-1TM demonstrate flexibility in the linker between their extracellular and TM domains, rather than the previously proposed rigid linkage. A previously postulated interface between the alpha(V) and beta(3) subunits at their knees was also not supported, because it lacks high-quality density, required rebuilding in alpha(V)beta(3)-1TM, and differed markedly between alpha(V)beta(3)-1TM and alpha(V)beta(3)-AB. Together with the variation in domain-domain orientation within their bent ectodomains between alpha(V)beta(3)-AB and alpha(V)beta(3)-1TM, these findings are compatible with the requirement for large structural changes, such as extension at the knees and headpiece opening, in conveying activation signals between the extracellular ligand-binding site and the cytoplasm. alpha(V)beta(3) Integrin Crystal Structures and Their Functional Implications.,Dong X, Mi LZ, Zhu J, Wang W, Hu P, Luo BH, Springer TA Biochemistry. 2012 Nov 6;51(44):8814-28. doi: 10.1021/bi300734n. Epub 2012 Oct, 29. PMID:23106217[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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