2IXG: Crystal Structure Of The Atpase Domain Of Tap1 With Atp (S621a, G622v, D645n Mutant)

The 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.
PDB ID: 2IXGDownload
MMDB ID: 53583
PDB Deposition Date: 2006/7/8
Updated in MMDB: 2012/11
Experimental Method:
x-ray diffraction
Resolution: 2.7  Å
Source Organism:
Similar Structures:
Biological Unit for 2IXG: monomeric; determined by author and by software (PQS)
Molecular Components in 2IXG
Label Count Molecule
Protein (1 molecule)
Antigen Peptide Transporter 1(Gene symbol: Tap1)
Molecule annotation
Chemicals (2 molecules)
* Click molecule labels to explore molecular sequence information.

Citing MMDB