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J. Bacteriol., 08 1995, 4587-4592, Vol 177, No. 16
G Cecchini, H Sices, I Schroder and RP Gunsalus
Fumarate reductase from Escherichia coli functions both as an anaerobic
fumarate reductase and as an aerobic succinate dehydrogenase. A site-
directed mutation of E. coli fumarate reductase in which FrdB Pro-159 was
replaced with a glutamine or histidine residue was constructed and
overexpressed in a strain of E. coli lacking a functional copy of the
fumarate reductase or succinate dehydrogenase complex. The consequences of
these mutations on bacterial growth, assembly of the enzyme complex, and
enzymatic activity were investigated. Both mutations were found to have no
effect on anaerobic bacterial growth or on the ability of the enzyme to
reduce fumarate compared with the wild-type enzyme. The FrdB
Pro-159-to-histidine substitution was normal in its ability to oxidize
succinate. In contrast, however, the FrdB Pro-159-to-Gln substitution was
found to inhibit aerobic growth of E. coli under conditions requiring a
functional succinate dehydrogenase, and furthermore, the aerobic activity
of the enzyme was severely inhibited upon incubation in the presence of its
substrate, succinate. This inactivation could be prevented by incubating
the mutant enzyme complex in an anaerobic environment, separating the
catalytic subunits of the fumarate reductase complex from their membrane
anchors, or blocking the transfer of electrons from the enzyme to quinones.
The results of these studies suggest that the succinate-induced
inactivation occurs by the production of hydroxyl radicals generated by a
Fenton-type reaction following introduction of this mutation into the
[3Fe-4S] binding domain. Additional evidence shows that the
substrate-induced inactivation requires quinones, which are the
membrane-bound electron acceptors and donors for the succinate
dehydrogenase and fumarate reductase activities.(ABSTRACT TRUNCATED AT 250
WORDS)
Copyright © 1995, American Society for Microbiology
Aerobic inactivation of fumarate reductase from Escherichia coli by mutation of the [3Fe-4S]-quinone binding domain
Molecular Biology Division, Veterans Administration Medical Center, San Francisco, California 94121, USA.
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