期刊
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
卷 107, 期 51, 页码 22219-22224出版社
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1014708107
关键词
bidirectional binding; antigen presentation; peptide loading
资金
- Bundesministerium fur Bildung und Forschung [01 EZ 1010B]
- Deutsche Forschungsgemeinschaft [SFB765]
T-cell recognition of peptides bound to MHC class II (MHCII) molecules is a central event in cell-mediated adaptive immunity. The current paradigm holds that prebound class II-associated invariant chain peptides (CLIP) and all subsequent antigens maintain a canonical orientation in the MHCII binding groove. Here we provide evidence for MHCII-bound CLIP inversion. NMR spectroscopy demonstrates that the interconversion from the canonical to the inverse alignment is a dynamic process, and X-ray crystallography shows that conserved MHC residues form a hydrogen bond network with the peptide backbone in both orientations. The natural catalyst HLA-DM accelerates peptide reorientation and the exchange of either canonically or inversely bound CLIP against antigenic peptide. Thus, noncanonical MHC-CLIP displays the hallmarks of a structurally and functionally intact antigen-presenting complex.
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