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Critical residues within the TAPBPR scoop loop for HLA-A2 binding and peptide loading are determined by deep mutational scanning

ABSTRACT: The loading of high affinity peptides onto nascent class I MHC (MHC-I) molecules is facilitated by chaperones, including the class I-specific chaperone TAP-binding protein-related (TAPBPR). TAPBPR features a loop (amino acids 24-35) that projects towards the empty MHC-I peptide binding groove and rests above the F pocket. The 24-35 loop is much shorter in the closely related homologue tapasin, and therefore may be partly responsible for the unique antigen editing properties of TAPBPR. Previously we reported a deep mutational scan of human TAPBPR focused on the 24-35 loop, and determined the relative effects of single amino acid mutations on binding and peptide-mediated release of the murine H2-Dd MHC-I allomorph. Here, we extend our studies to determine the mutational landscape of the 24-35 loop when TAPBPR binds a human MHC-I allomorph, HLA-A*02:01. The data highlights how TAPBPR affinity can be increased or decreased for different MHC-I allomorphs by tuning the electrostatic complementarity of the 24-35 loop for surfaces on the rim of the peptide-binding groove. By changing the selection pressure from HLA-A2 binding to HLA-A2 loading and processing, we find that TAPBPR is reasonably tolerant of mutations in the 24-35 loop for efficient peptide-MHC-I processing and surface trafficking.

ORGANISM(S): Homo sapiens

PROVIDER: GSE126206 | GEO | 2019/09/01

REPOSITORIES: GEO

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Deep mutagenesis of HLA-A*02:01 reveals elements of folded structure necessary for MHC-I-specific chaperone interactions and plasma membrane trafficking

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