Oxidation of Reduced Menaquinone by the Fumarate Reductase Complex in Escherichia coli Requires the Hydrophobic Frdd Peptide


Plasmids carrying cloned segements of the frd operon of Escherichia coli have been used in genetic complementation studies to identify two independent mutants defective in the frdD gene, which encodes the hydrophobic FrdD polypeptide of the fumarate reductase complex. Mutations in the frdA and frdB genes have also been mapped by this technique. One of the FrdD peptide mutants, DW109 (frdD-109), showed that fumarate reductase was not as tightly bound to the membrane in this mutant. In addition, the mutation in the FrdD peptide caused an almost total loss of the ability of the enzyme to oxidize either menaquinol-6, a physiological donor for fumarate reduction, or reduced benzyl viologen. However, the mutation did not impair the ability of the membrane-bound furmarate reductase complex to function with succinate as substrate, as evidenced by unchanged turnover numbers for phenazine methosulfate and 2,3-dimethoxy-5-methyl-6-pentyl-1,4-benzoquinone (a quinone analogue) reductase activities. These data establish the essential role of the FrdD polypeptide both in the interaction of the enzyme with reduced menaquinone and thus in anaerobic respiration with fumarate as electron acceptor, and in binding the enzyme to the membrane.


Biological Sciences


National Institutes of Health (U.S.)


This work was supported by National Institutes of Health Grant HL-16251 and the Veterans Administration (G.C. and B.A.C.A.) and by National Science Foundation Grant PCM-8402974 and the Univ. of California, Los Angeles, Biomedical Program (R.P.G.). One of us (D.J.W.) was supported by Public Health Service Cellular and Molecular Biology Training Grant GM-07185 from the National Institutes of Health.

Keywords and Phrases

Fumarate Reductase; Menaquinone; Escherichia coli; Heredity; Nonhuman

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Article - Journal

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© 1986 National Academy of Sciences, All rights reserved.

Publication Date

01 Dec 1986

PubMed ID