2vsd | pdb_00002vsd
crystal structure of CHIR-AB1
Structural highlights
FunctionEvolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedCHIR-AB1 is a newly identified avian immunoglobulin (Ig) receptor that includes both activating and inhibitory motifs and was therefore classified as a potentially bifunctional receptor. Recently, CHIR-AB1 was shown to bind the Fc region of chicken IgY and to induce calcium mobilization via association with the common gamma-chain, a subunit that transmits signals upon ligation of many different immunoreceptors. Here we describe the 1.8-A-resolution crystal structure of the CHIR-AB1 ectodomain. The receptor ectodomain consists of a single C2-type Ig domain resembling the Ig-like domains found in mammalian Fc receptors such as FcgammaRs and FcalphaRI. Unlike these receptors and other monomeric Ig superfamily members, CHIR-AB1 crystallized as a 2-fold symmetrical homodimer that bears no resemblance to variable or constant region dimers in an antibody. Analytical ultracentrifugation demonstrated that CHIR-AB1 exists as a mixture of monomers and dimers in solution, and equilibrium gel filtration revealed a 2:1 receptor/ligand binding stoichiometry. Measurement of the 1:1 CHIR-AB1/IgY interaction affinity indicates a relatively low affinity complex, but a 2:1 CHIR-AB1/IgY interaction allows an increase in apparent affinity due to avidity effects when the receptor is tethered to a surface. Taken together, these results add to the structural understanding of Fc receptors and their functional mechanisms. The crystal structure of CHIR-AB1: a primordial avian classical Fc receptor.,Arnon TI, Kaiser JT, West AP Jr, Olson R, Diskin R, Viertlboeck BC, Gobel TW, Bjorkman PJ J Mol Biol. 2008 Sep 12;381(4):1012-24. Epub 2008 Jul 3. PMID:18625238[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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