title: Orientation of the g-tensor axes of the Rieske subunit in the cytochrome bc1 complex.
abstract: The orientation of the g-tensors of the Rieske iron-sulfur protein subunit was determined in a single crystal of the bovine mitochondrial cytochrome bc1 complex with stigmatellin in the Qo quinol binding site. The g-tensor principal axes are skewed with respect to the Fe-Fe and S-S atom direction in the 2Fe2S cluster, which is allowed by the lack of rigorous symmetry of the cluster. The asymmetric unit in the crystal is the active dimer, and the g-tensor axes have slightly different orientations relative to the iron-sulfur cluster in the two halves of the dimer. The g approximately 1.79 axis makes an average angle of 30 degrees with respect to the Fe-Fe direction and the g approximately 2.024 axis an average angle of 26 degrees with respect to the S-S direction. This assignment of the g-tensor axis directions indicates that conformations of the Rieske protein are likely the same in the cytochrome bc1 and b6f complexes and that the extent of motion of the Rieske head domain during the catalytic cycle has been highly conserved during evolution of these distantly related complexes.
authors.affiliation: W. R. Wiley Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, P.O. Box 999, K8-98, Richland, Washington 99352-0999, USA. Michael.bowman@pnl.gov
authors.forename: Michael K
authors.initials: MK
authors.lastname: Bowman
authors.forename: Edward A
authors.initials: EA
authors.lastname: Berry
authors.forename: Arthur G
authors.initials: AG
authors.lastname: Roberts
authors.forename: David M
authors.initials: DM
authors.lastname: Kramer
mesh_terms: D000818:Animals; D002384:Catalysis; D002417:Cattle; D003460:Crystallization; D019281:Dimerization; D004578:Electron Spin Resonance Spectroscopy; D004579:Electron Transport; D014450:Electron Transport Complex III / Q000037:antagonists & inhibitors / Q000737:chemistry*; D004791:Enzyme Inhibitors / Q000737:chemistry; D007506:Iron-Sulfur Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry*; D008024:Ligands; D008928:Mitochondria / Q000201:enzymology*; D011090:Polyenes / Q000737:chemistry; D021122:Protein Subunits / Q000037:antagonists & inhibitors / Q000737:chemistry*
chemical_list: D004791:Enzyme Inhibitors; D007506:Iron-Sulfur Proteins; D008024:Ligands; D011090:Polyenes; D021122:Protein Subunits; C037989:Rieske iron-sulfur protein; C041573:stigmatellin; D014450:Electron Transport Complex III