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The transport complex TAP and the art of substrate selection

3 May 2010 . The adaptive immune system plays an essential role in protecting vertebrates against pathogens and cancer. The major histocompatibility complex (MHC) class I-dependent pathway of antigen presentation represents a sophisticated strategy to recognize and eliminate infected or malignantly transformed cells, taking advantage of the constant proteasomal turnover of the cellular proteome. The transporter associated with antigen processing (TAP) is a crucial component of this pathway, catalyzing the peptide translocation and loading of MHC I complexes in the ER-lumen.

By a tour-de-force approach, the group of Robert Tampé identified one single cysteinyl residue out of 19 cysteines, which controls the substrate binding and translocation of human TAP, thereby restricting the epitope repertoire. As part of an unexpected mechanism, this residue is crucial in complementing the binding pocket for a given subset of epitopes as well as in maintaining a substrate-receptive conformation of the translocation complex. The residues are published in the latest issue of the Proceedings of the National Academy of the USA by Baldauf et al.

Links
Full paper
Robert Tampé's website

Veröffentlichung: Baldauf, C., Schrodt, S., Herget, M., Koch, J. & Tampé, R. (2010) Single residue within the antigen translocation complex TAP controls the epitope repertoire by stabilizing a receptive conformation. Proc. Natl. Acad. Sci. U.S.A., online publication 3 May 2010, in press.