Peptide Loading on Class-I MHC Proteins (IMAGE) University of California - Santa Cruz Caption In this schematic of peptide loading on class-I MHC proteins, the molecular chaperone TAPBPR (blue) catalyzes the loading of a small peptide antigen (purple), derived from a viral or tumor protein, on the peptide-binding groove of a class-I MHC protein (gray/green). The interplay between a highly polymorphic set of MHC-I alleles and molecular chaperones shapes the repertoire of peptide antigens displayed on the cell surface for T-cell surveillance. Credit Nikolaos Sgourakis Usage Restrictions For use only with news coverage of this research. License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.