Insights into MHC class I peptide loading from the structure of the tapasin-ERp57 thiol oxidoreductase heterodimer.
Publication Type:Journal Article
Source:Immunity, Volume 30, Issue 1, p.21-32 (2009)
Keywords:Animals, Cell Line, Crystallography, X-Ray, Dimerization, Histocompatibility Antigens Class I, Humans, Membrane Transport Proteins, Models, Molecular, Peptides, Protein Disulfide Reductase (Glutathione), Protein Disulfide-Isomerases, Protein Structure, Quaternary
<p>Tapasin is a glycoprotein critical for loading major histocompatibility complex (MHC) class I molecules with high-affinity peptides. It functions within the multimeric peptide-loading complex (PLC) as a disulfide-linked, stable heterodimer with the thiol oxidoreductase ERp57, and this covalent interaction is required to support optimal PLC activity. Here, we present the 2.6 A resolution structure of the tapasin-ERp57 core of the PLC. The structure revealed that tapasin interacts with both ERp57 catalytic domains, accounting for the stability of the heterodimer, and provided an example of a protein disulfide isomerase family member interacting with substrate. Mutational analysis identified a conserved surface on tapasin that interacted with MHC class I molecules and was critical for peptide loading and editing functions of the tapasin-ERp57 heterodimer. By combining the tapasin-ERp57 structure with those of other defined PLC components, we present a molecular model that illuminates the processes involved in MHC class I peptide loading.</p>