Regulated expression in vitro of genes coding for formate hydrogenlyase components of Escherichia coli.
Purified FHLA, the transcriptional activator of the formate regulon from Escherichia coli, is able to efficiently stimulate transcription from the sigma 54-dependent promoters of the fdhF, hyp, and hyc transcriptional units. Expression was dependent on the presence of sigma 54, of the upstream activatory sequence (UAS), and of formate. Hypophosphite, a formate analogue, could substitute for formate in vitro suggesting that formate per se was active in regulation. The integration host factor (IHF) had a direct effect on the expression (in vivo and in vitro) of the hyp and hyc genes but not of the fdhF gene. Binding of IHF within the region between the hyp and the hyc operon could be shown. A model is proposed for the transcriptional regulation of the inversely oriented hyp and hyc operons. It involves two upstream regulatory sequences, one between the hyp and the hyc operon (IR1), and the other between hycA and hycB (IR2). The UAS situated within IR1 is responsible for activation of the hyc operon, that within IR2 for activation of the hyp operon. A supramolecular transcription complex is proposed which involves the binding of IHF to a site located between the UAS and the promoter responsible for transcription of the hyc operon.
Lehrstuhl für Mikrobiologie der Universität München, Germany.
S
S
Hopper
M
M
Babst
V
V
Schlensog
H M
HM
Fischer
H
H
Hennecke
A
A
Böck
D001426:Bacterial Proteins / Q000378:metabolism; D001483:Base Sequence; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics*; D029968:Escherichia coli Proteins; D005560:Formate Dehydrogenases / Q000235:genetics*; D005561:Formates / Q000494:pharmacology; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects; D006864:Hydrogenase / Q000235:genetics*; D034982:Integration Host Factors; D008957:Models, Genetic; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes / Q000235:genetics*; D009876:Operon / Q000235:genetics; D010721:Phosphinic Acids / Q000494:pharmacology; D011401:Promoter Regions, Genetic / Q000235:genetics; D015183:Restriction Mapping; D015534:Trans-Activators; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic
D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D005561:Formates; D034982:Integration Host Factors; D009097:Multienzyme Complexes; D010721:Phosphinic Acids; D015534:Trans-Activators; D014157:Transcription Factors; C030544:formic acid; C067189:fhlA protein, E coli; C009287:sodium hypophosphite; D006864:Hydrogenase; D005560:Formate Dehydrogenases; C054017:formate hydrogenlyase