Structure of the γ-chain of the human IgE FcεR1 receptor: NMR and molecular dynamics studies

Abstract

The solution structure of the 37-residue intracellular γ-chain of the human Fc_εR1 receptor protein has been determined using high field ¹H nuclear magnetic resonance (NMR) spectroscopy combined with molecular dynamics simulations. Two closely related groups of α-helical structures were found, with disruptions of the helix between residues 20 to 24; for one group the disruption is a type I β-turn, and in the second this region is less structured and acts as a loose ‘hinge’ between the α-helical regions. All structures exhibited a major and a minor hydrophobic region. The two tyrosines of the ARAM (antigen recognition activation motif) consensus motif lie on a single face of the helix, as do the two hydrophobic ARAM leucine and isoleucine residues. Three of the five threonines define a third face. These data are used to propose a model for the in vivo dimer of the γ-chain which is consistent with the susceptibility of the tyrosines and threonines to phosphorylation as an important feature of signal transduction.