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Bailey A, Dalchau N, Carter R, Emmott S, Phillips A, Werner JM, Elliott T. Selector function of MHC I molecules is determined by protein plasticity. Sci Rep 2015; 5:14928. [PMID: 26482009 PMCID: PMC5224517 DOI: 10.1038/srep14928] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2015] [Accepted: 09/09/2015] [Indexed: 12/27/2022] Open
Abstract
The selection of peptides for presentation at the surface of most nucleated cells by major histocompatibility complex class I molecules (MHC I) is crucial to the immune response in vertebrates. However, the mechanisms of the rapid selection of high affinity peptides by MHC I from amongst thousands of mostly low affinity peptides are not well understood. We developed computational systems models encoding distinct mechanistic hypotheses for two molecules, HLA-B*44:02 (B*4402) and HLA-B*44:05 (B*4405), which differ by a single residue yet lie at opposite ends of the spectrum in their intrinsic ability to select high affinity peptides. We used in vivo biochemical data to infer that a conformational intermediate of MHC I is significant for peptide selection. We used molecular dynamics simulations to show that peptide selector function correlates with protein plasticity, and confirmed this experimentally by altering the plasticity of MHC I with a single point mutation, which altered in vivo selector function in a predictable way. Finally, we investigated the mechanisms by which the co-factor tapasin influences MHC I plasticity. We propose that tapasin modulates MHC I plasticity by dynamically coupling the peptide binding region and α3 domain of MHC I allosterically, resulting in enhanced peptide selector function.
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Affiliation(s)
- Alistair Bailey
- Institute for Life Sciences, Building 85, University of Southampton, SO17 1BJ, UK
- Cancer Sciences Unit, Faculty of Medicine, University of Southampton, Southampton, SO16 6YD, UK
- Centre for Biological Sciences, Faculty of Natural & Environmental Sciences, Building 85, University of Southampton, SO17 1BJ, UK
| | - Neil Dalchau
- Computational Science Laboratory, Microsoft Research, 21 Station Road, Cambridge, CB1 2FB, UK
| | - Rachel Carter
- Institute for Life Sciences, Building 85, University of Southampton, SO17 1BJ, UK
- Cancer Sciences Unit, Faculty of Medicine, University of Southampton, Southampton, SO16 6YD, UK
| | - Stephen Emmott
- Computational Science Laboratory, Microsoft Research, 21 Station Road, Cambridge, CB1 2FB, UK
| | - Andrew Phillips
- Computational Science Laboratory, Microsoft Research, 21 Station Road, Cambridge, CB1 2FB, UK
| | - Jörn M. Werner
- Institute for Life Sciences, Building 85, University of Southampton, SO17 1BJ, UK
- Centre for Biological Sciences, Faculty of Natural & Environmental Sciences, Building 85, University of Southampton, SO17 1BJ, UK
| | - Tim Elliott
- Institute for Life Sciences, Building 85, University of Southampton, SO17 1BJ, UK
- Cancer Sciences Unit, Faculty of Medicine, University of Southampton, Southampton, SO16 6YD, UK
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