Electron transfer and catalytic control by the iron-sulfur clusters in a respiratory enzyme, E. coli fumarate reductase.
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.
Hudson
Janette M
JM
Department of Chemistry, Inorganic Chemistry Laboratory, Oxford University, South Parks Road, Oxford OX1 3QR, U.K.
Heffron
Kerensa
K
Kotlyar
Violetta
V
Sher
Yelizaveta
Y
Maklashina
Elena
E
Cecchini
Gary
G
Armstrong
Fraser A
FA
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*
D005415:Flavins; D007506:Iron-Sulfur Proteins; D013385:Succinate Dehydrogenase