Succinate dehydrogenase and fumarate reductase from Escherichia coli.
Succinate-ubiquinone oxidoreductase (SQR) as part of the trichloroacetic acid cycle and menaquinol-fumarate oxidoreductase (QFR) used for anaerobic respiration by Escherichia coli are structurally and functionally related membrane-bound enzyme complexes. Each enzyme complex is composed of four distinct subunits. The recent solution of the X-ray structure of QFR has provided new insights into the function of these enzymes. Both enzyme complexes contain a catalytic domain composed of a subunit with a covalently bound flavin cofactor, the dicarboxylate binding site, and an iron-sulfur subunit which contains three distinct iron-sulfur clusters. The catalytic domain is bound to the cytoplasmic membrane by two hydrophobic membrane anchor subunits that also form the site(s) for interaction with quinones. The membrane domain of E. coli SQR is also the site where the heme b556 is located. The structure and function of SQR and QFR are briefly summarized in this communication and the similarities and differences in the membrane domain of the two enzymes are discussed.
Cecchini
Gary
G
Molecular Biology Division, VA Medical Center, San Francisco, CA 94121, USA. ceccini@itsa.ucsf.edu
Schröder
Imke
I
Gunsalus
Robert P
RP
Maklashina
Elena
E
D001665:Binding Sites; D002462:Cell Membrane / Q000201:enzymology; D042963:Electron Transport Complex II; D004926:Escherichia coli / Q000201:enzymology*; D015964:Gene Expression Regulation, Bacterial; D015971:Gene Expression Regulation, Enzymologic; D006863:Hydrogen-Ion Concentration; D007425:Intracellular Membranes / Q000201:enzymology; D007506:Iron-Sulfur Proteins / Q000378:metabolism; D007700:Kinetics; D008958:Models, Molecular; D009097:Multienzyme Complexes / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D005810:Multigene Family; D010088:Oxidoreductases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D013329:Structure-Activity Relationship; D013385:Succinate Dehydrogenase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
D007506:Iron-Sulfur Proteins; D009097:Multienzyme Complexes; D010088:Oxidoreductases; D042963:Electron Transport Complex II; C424907:quinol fumarate reductase; D013385:Succinate Dehydrogenase