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J. Bacteriol., 11 1995, 6652-6656, Vol 177, No. 22
SJ Park, PA Cotter and RP Gunsalus
Malate dehydrogenase catalyzes the interconversion of malate and
oxaloacetate. It participates as a member of the tricarboxylic acid cycle
and the branched noncyclic pathways under aerobic and anaerobic cell growth
conditions, respectively. To investigate how the mdh gene is expressed
under these different conditions, an mdh-lacZ operon fusion was constructed
and analyzed in vivo. The mdh-lacZ fusion was expressed about twofold
higher under aerobic conditions than under anaerobic cell growth conditions
on most media tested. This anaerobic response is modulated by the ArcA
protein, which functions as a repressor of mdh gene expression under both
aerobic and anaerobic conditions. In contrast, mutations in the fnr gene
did not affect mdh gene expression. Interestingly, cells grown
anaerobically with glycerol and trimethylamine N-oxide or fumarate showed
higher levels of mdh expression than did cells that were grown aerobically.
Depending on the type of carbon compound used for cell growth, mdh
expression varied by 11-fold and 5-fold under aerobic and anaerobic
conditions, respectively. While mdh transcription was shown to be inversely
proportional to the cell growth rate, cellular heme limitation stimulated a
fivefold increase in mdh gene expression. The mdh gene appears to be highly
regulated to adapt to changing conditions of aerobic and anaerobic cell
growth with various types of carbon substrates.
Copyright © 1995, American Society for Microbiology
Regulation of malate dehydrogenase (mdh) gene expression in Escherichia coli in response to oxygen, carbon, and heme availability
Department of Microbiology and Molecular Genetics, University of California, Los Angeles 90095, USA.
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