title: Electron transfer and catalytic control by the iron-sulfur clusters in a respiratory enzyme, E. coli fumarate reductase.
abstract: Factors governing the efficacy of long-range electron relays in enzymes have been examined using protein film voltammetry in conjunction with site-directed mutagenesis. Investigations of the fumarate reductase from Escherichia coli, in which three Fe-S clusters relay electrons over more than 30 A, lead to the conclusion that varying the medial [4Fe-4S] cluster potential over a 100 mV range does not have a significant effect on the inherent kinetics of electron transfer to and from the active-site flavin. The results support a proposal that the reduction potential of an individual electron relay site in a multicentered enzyme is not a strong determinant of activity; instead, as deduced from the potential dependence of catalytic electron transfer, electron flow through the intramolecular relay is rapid and reversible, and even uphill steps do not limit the catalytic rate.
authors.affiliation: Department of Chemistry, Inorganic Chemistry Laboratory, Oxford University, South Parks Road, Oxford OX1 3QR, U.K.
authors.forename: Janette M
authors.initials: JM
authors.lastname: Hudson
authors.forename: Kerensa
authors.initials: K
authors.lastname: Heffron
authors.forename: Violetta
authors.initials: V
authors.lastname: Kotlyar
authors.forename: Yelizaveta
authors.initials: Y
authors.lastname: Sher
authors.forename: Elena
authors.initials: E
authors.lastname: Maklashina
authors.forename: Gary
authors.initials: G
authors.lastname: Cecchini
authors.forename: Fraser A
authors.initials: FA
authors.lastname: Armstrong
mesh_terms: D000595:Amino Acid Sequence; D002384:Catalysis; D004563:Electrochemistry; D004926:Escherichia coli / Q000201:enzymology*; D005415:Flavins / Q000737:chemistry / Q000378:metabolism; D007506:Iron-Sulfur Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D007700:Kinetics; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D020125:Mutation, Missense; D010084:Oxidation-Reduction; D016415:Sequence Alignment; D013329:Structure-Activity Relationship; D013385:Succinate Dehydrogenase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*
chemical_list: D005415:Flavins; D007506:Iron-Sulfur Proteins; D013385:Succinate Dehydrogenase