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) ...
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-nonassociated 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 ion Cu 2+ or Ni 2+ , but not Mn 2+ , Zn 2+ , or Hg 2+ , 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 major histocompatibility complex class II, but also class I, molecules can undergo metal ion-induced conformational alterations. Our findings suggest that metals may have a role in triggering rheumatic diseases such as AS and also have implications for the molecular basis of metal-induced hypersensitivities and allergies.
Organizational Affiliation:
Institut für Chemie/Biochemie, AG Strukturbiochemie, Freie Universität Berlin, Takustrasse 6, 14195 Berlin, Germany; MoloX GmbH, Takustrasse 6, 14195 Berlin, Germany. Electronic address: loll@chemie.fu-berlin.de.
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