PMID: 25925696
Kiyoshi M, Caaveiro JM, Kawai T, Tashiro S, Ide T, Asaoka Y, Hatayama K, Tsumoto K
Structural basis for binding of human IgG1 to its high-affinity human receptor FcgammaRI.
Nat Commun. 2015 Apr 30;6:6866. doi: 10.1038/ncomms7866.
Cell-surface Fcgamma receptors mediate innate and adaptive immune responses. Human Fcgamma receptor I (hFcgammaRI) binds IgGs with high affinity and is the only Fcgamma receptor that can effectively capture monomeric IgGs. However, the molecular basis of hFcgammaRI's interaction with Fc has not been determined, limiting our understanding of this major immune receptor. Here we report the crystal structure of a complex between hFcgammaRI and human Fc, at 1.80 A resolution, revealing an unique hydrophobic pocket at the surface of hFcgammaRI perfectly suited for residue Leu235 of Fc, which explains the high affinity of this complex. Structural, kinetic and thermodynamic data demonstrate that the binding mechanism is governed by a combination of non-covalent interactions, bridging water molecules and the dynamic features of Fc. In addition, the hinge region of hFcgammaRI-bound Fc adopts a straight conformation, potentially orienting the Fab moiety. These findings will stimulate the development of novel therapeutic strategies involving hFcgammaRI.