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Inhibitor-Binding Mode of Homobelactosin C to Proteasomes: New Insights into Class I MHC Ligand Generation

Michael Groll, Oleg V. Larionov, Robert Huber and Armin de Meijere
Proceedings of the National Academy of Sciences of the United States of America
Vol. 103, No. 12 (Mar. 21, 2006), pp. 4576-4579
Stable URL: http://www.jstor.org/stable/30048983
Page Count: 4
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Inhibitor-Binding Mode of Homobelactosin C to Proteasomes: New Insights into Class I MHC Ligand Generation
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Abstract

Most class I MHC ligands are generated from the vast majority of cellular proteins by proteolysis within the ubiquitin-proteasome pathway and are presented on the cell surface by MHC class I molecules. Here, we present the crystallographic analysis of yeast 20S proteasome in complex with the inhibitor homobelactosin C. The structure reveals a unique inhibitor-binding mode and provides information about the composition of proteasomal primed substrate-binding sites. IFN-γ inducible substitution of proteasomal constitutive subunits by immunosubunits modulates characteristics of generated peptides, thus producing fragments with higher preference for binding to MHC class I molecules. The structural data for the proteasome:homobelactosin C complex provide an explanation for involvement of immunosubunits in antigen generation and open perspectives for rational design of ligands, inhibiting exclusively constitutive proteasomes or immunoproteasomes.

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