1y1a | pdb_00001y1a
CRYSTAL STRUCTURE OF CALCIUM AND INTEGRIN BINDING PROTEIN
Structural highlights
Function[CIB1_HUMAN] May convert the inactive conformation of integrin alpha-IIb/beta3 to an active form through binding to the integrin cytoplasmic domain. Induces cell migration and spreading mediated through integrin (possibly via focal adhesion complexes). Functions as a negative regulator of stress activated MAP kinase (MAPK) signaling pathways. May play a role in regulation of apoptosis. Interacts with and up-regulates PTK2/FAK1 activity. Down regulates inositol 1,4,5-trisphosphate receptor-dependent calcium signaling. Participates in endomitotic cell cycle, a form of mitosis in which both karyokinesis and cytokinesis are interrupted and is a hallmark of megakaryocyte differentiation.[1] [2] [3] [4] [5] [6] 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 PubMedCalcium- and integrin-binding protein 1 (CIB1) is involved in the process of platelet aggregation by binding the cytoplasmic tail of the alpha(IIb) subunit of the platelet-specific integrin alpha(Iib)beta(3). Although poorly understood, it is widely believed that CIB1 acts as a global signaling regulator because it is expressed in many tissues that do not express integrin alpha(Iib)beta(3). We report the structure of human CIB1 to a resolution of 2.3 A, crystallized as a dimer. The dimer interface includes an extensive hydrophobic patch in a crystal form with 80% solvent content. Although the dimer form of CIB1 may not be physiologically relevant, this intersub-unit surface is likely to be linked to alpha(IIb) binding and to the binding of other signaling partner proteins. The C-terminal domain of CIB1 is structurally similar to other EF-hand proteins such as calmodulin and calcineurin B. Despite structural homology to the C-terminal domain, the N-terminal domain of CIB1 lacks calcium-binding sites. The structure of CIB1 revealed a complex with a molecule of glutathione in the reduced state bond to the N-terminal domain of one of the two subunits poised to interact with the free thiol of C35. Glutathione bound in this fashion suggests CIB1 may be redox regulated. Next to the bound GSH, the orientation of residues C35, H31, and S48 is suggestive of a cysteine-type protein phosphatase active site. The potential enzymatic activity of CIB1 is discussed and suggests a mechanism by which it regulates a wide variety of proteins in cells in addition to platelets. The crystal structure of calcium- and integrin-binding protein 1: insights into redox regulated functions.,Blamey CJ, Ceccarelli C, Naik UP, Bahnson BJ Protein Sci. 2005 May;14(5):1214-21. PMID:15840829[7] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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