Crystal Structure of a γδ T Cell Receptor Ligand T22: A Truncated MHC-Like Fold

Abstract

Murine T10 and T22 are highly related nonclassical major histocompatibility complex (MHC) class Ib proteins that bind to certain γδ T cell receptors (TCRs) in the absence of other components. The crystal structure of T22^bat 3.1 angstroms reveals similarities to MHC class I molecules, but one side of the normal peptide-binding groove is severely truncated, which allows direct access to the β-sheet floor. Potential γδ TCR-binding sites can be inferred from functional mapping of T10 and T22 point mutants and allelic variants. Thus, T22 represents an unusual variant of the MHC-like fold and indicates that γδ and αβ TCRs interact differently with their respective MHC ligands.