Regulation of the ndh gene of Escherichia coli by integration host factor and a novel regulator, Arr.
The ndh gene of Escherichia coli encodes the non-proton-translocating NADH dehydrogenase II. Expression of the ndh gene is subject to a complex network of regulatory controls at the transcriptional level. Under anaerobic conditions ndh is repressed by the regulator of fumarate and nitrate reduction (FNR). However, in the absence of FNR, ndh expression is activated by the amino acid response regulator (Arr) during anaerobic growth in rich medium. Expression of the ndh gene varies during the growth cycle in response to the intracellular concentration of the heat-stable DNA-binding protein, Fis. In this work two additional heat-stable proteins, integration host factor (IHF) and the histone-like protein HU were found to interact with the ndh promoter. IHF was shown to bind at three sites centred at +26, -17 and -58 in the ndh promoter (Kd = 10(-8) M), to prevent open-complex formation and to repress ndh transcription in vitro. Studies with an ndh-lacZ fusion confirmed that IHF represses ndh expression in vivo. Two putative binding sites for Arr, which overlap the two FNR boxes in the ndh promoter, were identified. Studies with the FNR-activated and amino-acid-inducible asparaginase II gene (ansB) showed that IHF and a component of the Arr-containing fraction (but not HU) interact with the corresponding ansB promoter.
Green
Jeffrey
J
Department of Molecular Biology & Biotechnology, University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, UK.
Anjum
Muna F
MF
Department of Molecular Biology & Biotechnology, University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, UK.
Guest
John R
JR
Department of Molecular Biology & Biotechnology, University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, UK.
D000595:Amino Acid Sequence; D000596:Amino Acids / Q000378:metabolism; D001215:Asparaginase / Q000235:genetics; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D004269:DNA, Bacterial / Q000235:genetics / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism*; D029968:Escherichia coli Proteins; D005798:Genes, Bacterial; D034982:Integration Host Factors; D007506:Iron-Sulfur Proteins / Q000378:metabolism; D009245:NADH Dehydrogenase / Q000235:genetics*; D011401:Promoter Regions, Genetic
D000596:Amino Acids; D001426:Bacterial Proteins; D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; C060704:FNR protein, E coli; D034982:Integration Host Factors; D007506:Iron-Sulfur Proteins; C088908:NADH dehydrogenase II; D009245:NADH Dehydrogenase; D001215:Asparaginase