Yeoman Kay H, Mitelheiser Sylvain, Sawers Gary, Johnston Andrew W B
School of Biological Sciences, University of East Anglia, Norwich NR4 7TJ, UK.
FEMS Microbiol Lett. 2003 Jun 27;223(2):239-44. doi: 10.1016/S0378-1097(03)00386-0.
When complexed with Escherichia coli RNA polymerase core enzyme, purified RpoI protein of Rhizobium leguminosarum initiated transcription in vitro from promoters of the vbsADL and vbsGSO operons, which are needed to synthesise the siderophore vicibactin. There is a single transcription initiation site for rpoI, regardless of whether the cells are grown in Fe-replete or Fe-depleted media, but levels of rpoI mRNA were reduced, though not abolished, in the presence of Fe. Unlike PvdS, a similar Pseudomonas sigma factor needed to transcribe genes involved in pyoverdine synthesis, RpoI transcribes vbsADL and vbsGSO in the absence of the cognate siderophore. The RpoI sigma factor is not required for transcription of rpoI.
