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Exchange catalysis by tapasin exploits conserved and allele-specific features of MHC-I molecules.
- Source :
- Nature Communications; 7/9/2021, Vol. 12 Issue 1, p1-13, 13p
- Publication Year :
- 2021
-
Abstract
- The repertoire of peptides presented by major histocompatibility complex class I (MHC-I) molecules on the cell surface is tailored by the ER-resident peptide loading complex (PLC), which contains the exchange catalyst tapasin. Tapasin stabilizes MHC-I molecules and promotes the formation of stable peptide-MHC-I (pMHC-I) complexes that serve as T cell antigens. Exchange of suboptimal by high-affinity ligands is catalyzed by tapasin, but the underlying mechanism is still elusive. Here we analyze the tapasin-induced changes in MHC-I dynamics, and find the catalyst to exploit two essential features of MHC-I. First, tapasin recognizes a conserved allosteric site underneath the α<subscript>2-1</subscript>-helix of MHC-I, 'loosening' the MHC-I F-pocket region that accomodates the C-terminus of the peptide. Second, the scoop loop<subscript>11–20</subscript> of tapasin relies on residue L18 to target the MHC-I F-pocket, enabling peptide exchange. Meanwhile, tapasin residue K16 plays an accessory role in catalysis of MHC-I allotypes bearing an acidic F-pocket. Thus, our results provide an explanation for the observed allele-specificity of catalyzed peptide exchange. Tapasin is part of the peptide loading complex necessary for presenting antigenic peptides on MHC-I for the induction of adaptive immunity. Here the authors show that tapasin interacts with MHC-I in both conserved and allele-specific regions to promote antigen presentation, with tapasin L18 and K16 residues both implicated in this molecular interaction. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 20411723
- Volume :
- 12
- Issue :
- 1
- Database :
- Complementary Index
- Journal :
- Nature Communications
- Publication Type :
- Academic Journal
- Accession number :
- 151332417
- Full Text :
- https://doi.org/10.1038/s41467-021-24401-4