title: Structure of Escherichia coli succinate:quinone oxidoreductase with an occupied and empty quinone-binding site.
abstract: Three new structures of Escherichia coli succinate-quinone oxidoreductase (SQR) have been solved. One with the specific quinone-binding site (Q-site) inhibitor carboxin present has been solved at 2.4 A resolution and reveals how carboxin inhibits the Q-site. The other new structures are with the Q-site inhibitor pentachlorophenol and with an empty Q-site. These structures reveal important details unresolved in earlier structures. Comparison of the new SQR structures shows how subtle rearrangements of the quinone-binding site accommodate the different inhibitors. The position of conserved water molecules near the quinone binding pocket leads to a reassessment of possible water-mediated proton uptake networks that complete reduction of ubiquinone. The dicarboxylate-binding site in the soluble domain of SQR is highly similar to that seen in high resolution structures of avian SQR (PDB 2H88) and soluble flavocytochrome c (PDB 1QJD) showing mechanistically significant structural features conserved across prokaryotic and eukaryotic SQRs.
authors.affiliation: Membrane Protein Crystallography Group, Molecular Biosciences Division, Imperial College, London SW72AZ, United Kingdom.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Ruprecht
authors.forename: Victoria
authors.initials: V
authors.lastname: Yankovskaya
authors.forename: Elena
authors.initials: E
authors.lastname: Maklashina
authors.forename: So
authors.initials: S
authors.lastname: Iwata
authors.forename: Gary
authors.initials: G
authors.lastname: Cecchini
mesh_terms: D000818:Animals; D001665:Binding Sites / Q000502:physiology; D001717:Birds; D002261:Carboxin / Q000737:chemistry; D042963:Electron Transport Complex II / Q000737:chemistry*; D004926:Escherichia coli / Q000201:enzymology*; D029968:Escherichia coli Proteins / Q000737:chemistry*; D020836:Protein Structure, Quaternary / Q000502:physiology; D040681:Structural Homology, Protein; D014451:Ubiquinone / Q000737:chemistry*
chemical_list: D029968:Escherichia coli Proteins; D014451:Ubiquinone; D002261:Carboxin; D042963:Electron Transport Complex II