2ixg
From Proteopedia
Crystal structure of the ATPase domain of TAP1 with ATP (S621A, G622V, D645N mutant)
Structural highlights
FunctionTAP1_RAT Involved in the transport of antigens from the cytoplasm to the endoplasmic reticulum for association with MHC class I molecules. Also acts as a molecular scaffold for the final stage of MHC class I folding, namely the binding of peptide. Nascent MHC class I molecules associate with TAP via tapasin (By similarity). Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedThe ABC transporter associated with antigen processing (TAP) shuttles cytosolic peptides into the endoplasmic reticulum for loading onto class I MHC molecules. Transport is fueled by ATP binding and hydrolysis at two distinct cytosolic ATPase sites. One site comprises consensus motifs shared among most ABC transporters, while the second has substituted, degenerate motifs. Biochemical and crystallography experiments with a TAP cytosolic domain demonstrate that the consensus ATPase site has high catalytic activity and facilitates ATP-dependent dimerization of the cytosolic domains, which is an important conformational change during transport. In contrast, the degenerate site is defective in dimerization and ATP hydrolysis. Full-length TAP mutagenesis demonstrates the necessity for at least one consensus site, supporting our conclusion that the consensus site is the principal facilitator of substrate transport. Since asymmetry of the ATPase site motifs is a feature of many mammalian homologs, our proposed model has broad implications for ABC transporters. Distinct structural and functional properties of the ATPase sites in an asymmetric ABC transporter.,Procko E, Ferrin-O'Connell I, Ng SL, Gaudet R Mol Cell. 2006 Oct 6;24(1):51-62. PMID:17018292[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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