Metal-triggered conformational reorientation of a self-peptide bound to a disease-associated HLA-B*27 subtyp
R. Driller, M. Ballaschk, P. Schmieder, B. Uchanska-Ziegler, A. Ziegler, B. Loll*
J. Biol. Chem. 294, 13269 - 13279 (2019)
Conformational changes of major histocompatibility complex (MHC) antigens have the potential to be recognized by T cells and may arise from polymorphic variation of the MHC molecule, the binding of modifying ligands, or both. Here, we investigated whether metal ions could affect allele-dependent structural variation of the two minimally distinct human leukocyte antigen (HLA)-B*27:05 and HLA-B*27:09 subtypes, which exhibit differential association with the rheumatic disease ankylosing spondylitis (AS). We employed NMR spectroscopy and X-ray crystallography coupled with ensemble refinement to study the AS-associated HLA-B*27:05 subtype and the AS non-associated HLA-B* 27:09 in complex with the self-peptide pVIPR (RRKWRRWHL). Both techniques revealed that pVIPR exhibits a higher degree of flexibility when complexed with HLA-B* 27:05 than with HLA-B*27:09. Furthermore, we found that the binding of the metal ions Cu2+ or Ni2+, but not Mn2+, Zn2+, or Hg2+ affects the structure of a pVIPR-bound HLA-B*27 molecule in a subtype-dependent manner. In HLA-B*27:05, the metals triggered conformational reorientations of pVIPR, but no such structural changes were observed in the HLA-B*27:09 subtype, with or without bound metal ion. These observations provide the first demonstration that not only MHC class II, but also class I molecules can undergo metal ion–induced conformational alterations. Our findings suggest that metals may have role in triggering rheumatic diseases such as AS and also have implications for the molecular basis of metal-induced hypersensitivities and allergies.