Crystal structure of the extracellular domain of a human FcγRIII

Abstract

Fc receptors play a major role in immune defenses against pathogens and in inflammatory processes. The crystal structure of a human immunoglobulin receptor, FcγRIIIb, has been determined to 1.8 Å resolution. The overall fold consists of two immunoglobulin-like domains with an acute interdomain hinge angle of approximately 50°. Trp-113, wedged between the N-terminal D1 and the C-terminal D2 domains, appears to further restrict the hinge angle. The putative Fc binding region of the receptor carries a net positive charge complementary to the negative-charged receptor binding regions on Fc. A 1:1 binding stoichiometry between the receptor and Fc was measured by both the equilibrium and nonequili..