Involvement of Fnr and ArcA in anaerobic expression of the tdc operon of Escherichia coli.
Anaerobic expression of the tdcABC operon in Escherichia coli, as measured by LacZ activity from single-copy tdc-lacZ transcriptional and translational fusions, is greatly reduced in strains lacking two global transcriptional regulators, Fnr and ArcA. The nucleotide sequence of the tdc promoter around -145 shows significant similarity with the consensus Fnr-binding site; however, extensive base substitutions within this region had no effect on Fnr regulation of the tdc genes. A genetic analysis revealed that the effect of Fnr on tdc is not mediated via ArcA. Furthermore, addition of cyclic AMP to the anaerobic incubation medium completely restored tdc expression in fnr and arcA mutants as well as in strains harboring mutations in the Fnr- and ArcA-dependent pfl gene and the Fnr-regulated glpA and frd genes. These results, taken together with the earlier finding that tdc expression is subject to catabolite repression by intermediary metabolites, strongly suggest that the negative regulatory effects of mutations in the fnr and arcA genes are mediated physiologically due to accumulation of a metabolite(s) which prevents tdc transcription in vivo.
Chattopadhyay
S
S
Department of Biological Chemistry, The University of Michigan, Ann Arbor 48109-0606, USA.
Wu
Y
Y
Datta
P
P
D026921:Amino Acid Transport Systems, Neutral; D000693:Anaerobiosis; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics / Q000502:physiology*; D001426:Bacterial Proteins / Q000235:genetics / Q000502:physiology*; D002244:Carbon / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics; D029968:Escherichia coli Proteins; D015964:Gene Expression Regulation, Bacterial; D015971:Gene Expression Regulation, Enzymologic; D007506:Iron-Sulfur Proteins / Q000235:genetics / Q000502:physiology*; D026901:Membrane Transport Proteins / Q000235:genetics; D009876:Operon; D012097:Repressor Proteins; D013913:Threonine Dehydratase / Q000235:genetics; D015534:Trans-Activators / Q000235:genetics
D026921:Amino Acid Transport Systems, Neutral; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; C060704:FNR protein, E coli; D007506:Iron-Sulfur Proteins; D026901:Membrane Transport Proteins; D012097:Repressor Proteins; C083450:TdcA protein, E coli; D015534:Trans-Activators; C041610:arcA protein, E coli; C065101:tdcC protein, E coli; D002244:Carbon; D013913:Threonine Dehydratase