title: High-resolution structure of the soluble, respiratory-type Rieske protein from Thermus thermophilus: analysis and comparison.
abstract: The structure of the soluble Rieske protein from Thermus thermophilus has been determined at a resolution of 1.3 A at pH 8.5 using multiwavelength anomalous dispersion (MAD) techniques. This is the first report of a Rieske protein from a menaquinone-utilizing organism. The structure shows an overall fold similar to previously reported Rieske proteins. A novel feature of this crystal form appears to be a shared hydrogen between the His-134 imidazole ring ligated to Fe2 of the [2Fe-2S] cluster and its symmetry partner, His-134', one being formally an imidazolate anion, Fe2-(His-134)N(epsilon)(-)...H-N(epsilon')(His-134')-Fe2', in which crystallographic C(2) axes pass equidistant between N(epsilon)...N(epsilon') and normal to the line defined by N(epsilon)...N(epsilon'). This provides evidence for a stable, oxidized cluster with a His(-) ligand and lends support to a previously proposed mechanism of coupled proton and electron transfer. A detailed comparison of the Thermus Rieske protein with six other Rieske and Rieske-type proteins indicates: (a) The cluster binding domain is tightly conserved. (b) The 3-D structure of the 10 beta-strand fold is conserved, even among the most divergent proteins. (c) There is an approximately linear relation between acid-pH redox potential and number of H-bonds to the cluster. (d) These proteins have two faces, one points into the larger complex (bc(1), b(6)f, or other), is involved in the proton coupled electron transfer function, and is highly conserved. The second is oriented toward the solvent and shows wide variation in charge, sequence, length, hydrophobicity, and secondary elements in the loops that connect the beta-sheets.
authors.affiliation: Division of Biology, the University of California at San Diego, 9500 Gilman Drive, La Jolla, California 92093, USA.
authors.forename: Laura M
authors.initials: LM
authors.lastname: Hunsicker-Wang
authors.forename: Andreas
authors.initials: A
authors.lastname: Heine
authors.forename: Ying
authors.initials: Y
authors.lastname: Chen
authors.forename: Eugene P
authors.initials: EP
authors.lastname: Luna
authors.forename: Thomas
authors.initials: T
authors.lastname: Todaro
authors.forename: Yan Ming
authors.initials: YM
authors.lastname: Zhang
authors.forename: Pamela A
authors.initials: PA
authors.lastname: Williams
authors.forename: Duncan E
authors.initials: DE
authors.lastname: McRee
authors.forename: Judy
authors.initials: J
authors.lastname: Hirst
authors.forename: C David
authors.initials: CD
authors.lastname: Stout
authors.forename: James A
authors.initials: JA
authors.lastname: Fee
mesh_terms: D000595:Amino Acid Sequence; D018360:Crystallography, X-Ray / Q000379:methods; D014450:Electron Transport Complex III; D006860:Hydrogen Bonding; D007506:Iron-Sulfur Proteins / Q000032:analysis / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011336:Probability; D011485:Protein Binding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid; D012995:Solubility; D055672:Static Electricity; D016963:Thermus thermophilus / Q000737:chemistry*
chemical_list: D007506:Iron-Sulfur Proteins; C037989:Rieske iron-sulfur protein; D014450:Electron Transport Complex III