Crystal structure of HLA-G: a nonclassical MHC class I molecule expressed at the fetal–maternal interface

CS Clements, L Kjer-Nielsen… - Proceedings of the …, 2005 - National Acad Sciences
CS Clements, L Kjer-Nielsen, L Kostenko, HL Hoare, MA Dunstone, E Moses, K Freed…
Proceedings of the National Academy of Sciences, 2005National Acad Sciences
HLA-G is a nonclassical major histocompatibility complex class I (MHC-I) molecule that is
primarily expressed at the fetal–maternal interface, where it is thought to play a role in
protecting the fetus from the maternal immune response. HLA-G binds a limited repertoire of
peptides and interacts with the inhibitory leukocyte Ig-like receptors LIR-1 and LIR-2 and
possibly with certain natural killer cell receptors. To gain further insights into HLA-G function,
we determined the 1.9-Å structure of a monomeric HLA-G complexed to a natural …
HLA-G is a nonclassical major histocompatibility complex class I (MHC-I) molecule that is primarily expressed at the fetal–maternal interface, where it is thought to play a role in protecting the fetus from the maternal immune response. HLA-G binds a limited repertoire of peptides and interacts with the inhibitory leukocyte Ig-like receptors LIR-1 and LIR-2 and possibly with certain natural killer cell receptors. To gain further insights into HLA-G function, we determined the 1.9-Å structure of a monomeric HLA-G complexed to a natural endogenous peptide ligand from histone H2A (RIIPRHLQL). An extensive network of contacts between the peptide and the antigen-binding cleft reveal a constrained mode of binding reminiscent of the nonclassical HLA-E molecule, thereby providing a structural basis for the limited peptide repertoire of HLA-G. The α3 domain of HLA-G, a candidate binding site for the LIR-1 and -2 inhibitory receptors, is structurally distinct from the α3 domains of classical MHC-I molecules, providing a rationale for the observed affinity differences for these ligands. The structural data suggest a head-to-tail mode of dimerization, mediated by an intermolecular disulfide bond, that is consistent with the observation of HLA-G dimers on the cell surface.
National Acad Sciences