2VSD

crystal structure of CHIR-AB1

Summary for 2VSD

• Entry DOI: 10.2210/pdb2vsd/pdb
• Descriptor: CHIR AB1, beta-D-mannopyranose-(1-4)-2-acetamido-2-deoxy-beta-D-glucopyranose-(1-4)-2-acetamido-2-deoxy-beta-D-glucopyranose (3 entities in total)
• Functional Keywords: immune system receptor, fc receptor
• Biological source: GALLUS GALLUS (CHICKEN)
• Total number of polymer chains: 1
• Total formula weight: 12613.90

Authors

Arnon, T.I.,Kaiser, J.T.,Bjorkman, P.J. (deposition date: 2008-04-22, release date: 2008-07-29, Last modification date: 2024-11-20)

Primary citation

Arnon, T.I.,Kaiser, J.T.,West, A.P.,Olson, R.,Diskin, R.,Viertlboeck, B.C.,Gobel, T.W.,Bjorkman, P.J.
The Crystal Structure of Chir-Ab1: A Primordial Avian Classical Fc Receptor.
J.Mol.Biol., 381:1012-, 2008

PubMed Abstract: CHIR-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.

PubMed: 18625238
DOI: 10.1016/J.JMB.2008.06.082

Experimental method

X-RAY DIFFRACTION (1.82 Å)