Aerobic regulation of isocitrate dehydrogenase gene (icd) expression in Escherichia coli by the arcA and fnr gene products.
Isocitrate dehydrogenase, the icd gene product, has been studied extensively regarding the regulation of enzymatic activity and its relationship to the metabolic flux between the tricarboxylic acid cycle and the glyoxylate bypass. In this study, the transcriptional regulation of icd gene expression was monitored by using an icd-lacZ gene fusion and shown to vary over a 15-fold range in response to changes in oxygen and carbon availability. Anaerobic cell growth resulted in fivefold-lower icd-lacZ expression than during aerobic growth. This negative control is mediated by the arcA and fnr gene products. When different carbon compounds were used for cell growth, icd-lacZ expression varied threefold. The results of continuous cell culture studies indicated that this control may be due to variations in cell growth rate rather than to catabolite repression. DNase I footprinting at the icd promoter revealed a 42-bp ArcA-phosphate-protected region that overlaps the start site of icd transcription. Phosphorylation of ArcA considerably enhanced its binding to DNA, while ArcA-phosphate exhibited an apparent dissociation value of approximately 0.1 microM. Based on these studies, ArcA appears to function as a classical repressor of transcription by binding at a site overlapping the icd promoter during anaerobic cell growth conditions.
Chao
G
G
Department of Microbiology and Molecular Genetics and Molecular Biology Institute, University of California, Los Angeles 90095, USA.
Shen
J
J
Tseng
C P
CP
Park
S J
SJ
Gunsalus
R P
RP
D000085:Acetates / Q000494:pharmacology; D000332:Aerobiosis; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics*; D001426:Bacterial Proteins / Q000235:genetics*; D001483:Base Sequence; D001665:Binding Sites; D002455:Cell Division; D003470:Culture Media; D004269:DNA, Bacterial; D004926:Escherichia coli / Q000201:enzymology* / Q000254:growth & development; D029968:Escherichia coli Proteins; D015964:Gene Expression Regulation, Bacterial; D015971:Gene Expression Regulation, Enzymologic; D005947:Glucose / Q000494:pharmacology; D007506:Iron-Sulfur Proteins / Q000235:genetics*; D007521:Isocitrate Dehydrogenase / Q000235:genetics*; D007763:Lac Operon; D008969:Molecular Sequence Data; D010100:Oxygen; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins / Q000235:genetics; D012097:Repressor Proteins
D000085:Acetates; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D003470:Culture Media; D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; C060704:FNR protein, E coli; D007506:Iron-Sulfur Proteins; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; D012097:Repressor Proteins; C041610:arcA protein, E coli; D007521:Isocitrate Dehydrogenase; D005947:Glucose; D010100:Oxygen