Premium
Anaerobic activation of arcA transcription in Escherichia coli : roles of Fnr and ArcA
Author(s) -
Compan Inès,
Touati Danlèle
Publication year - 1994
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.1994.tb00374.x
Subject(s) - biology , transcription (linguistics) , escherichia coli , gene , promoter , coding region , gene expression , anaerobic exercise , transcription factor , microbiology and biotechnology , genetics , physiology , philosophy , linguistics
Summary The ArcA and Fnr regulators of Escherichia coli , both of which are activated in anaerobic conditions, negatively regulate the sodA gene (coding for manganese superoxide dismutase), but Fnr has no effect on anaerobic sodA expression in a δ arcA δ fnr background (Compan and Touati, 1993). We show here that the sdh gene (coding for succinate dehydrogenase) is also negatively regulated by Fnr, but again Fnr exerts no control in a δ arcA background. One interpretation of these results is that Fnr activates arcA transcription. Using arcA–lac transcriptional and translational fusions, we show that arcA expression increases (about fourfold) in anaerobiosis and that both Fnr and ArcA are required for full expression, in a δ fnr background, there is no autoactivation, suggesting that ArcA enhances activation by Fnr. Transcript and sequence analyses reveal that the arcA upstream regulatory region lies within a 530 bp non‐coding DNA fragment, which contains five putative promoter sequences and a putative Fnr‐binding site, identification of the transcription start sites indicates that transcription occurs in aerobiosis from three constitutive upstream promoters (P e , P d , P c ). In anaerobiosis an additional completely Fnr‐dependent transcript starting at P a , is present; expression from Pa is reduced in the absence of ArcA, and Fnr activation at P a blocks the weak anaerobic‐dependent expression from P b Fnr activation of arcA transcription may play an important role in the co‐ordination of expression of genes associated with aerobic and anaerobic metabolism during environmental changes.