Analysis of the Streptomyces coelicolor sigE gene reveals the existence of a subfamily of eubacterial RNA polymerase σ factors involved in the regulation of extracytoplasmic functions

Michael A. Lonetto, Kelly L. Brown, Kenneth E. Rudd, Mark J. Buttner

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σ(E), an RNA polymerase σ factor of apparent M(r) 28,000, was previously identified by its ability to direct transcription from the P2 promoter of the agarase gene (dagA) of Streptomyces coelicolor. A degenerate oligonucleotide probe, designed from the N-terminal sequence of purified σ(E), was used to isolate the σ(E) gene (sigE). The predicted sequence of σ(E) shows greatest similarity to sequences of seven other proteins: Myxococcus xanthus CarQ, Pseudomonas aeruginosa AlgU, Pseudomonas syringae HrpL, Escherichia coli σ(E), Alcaligenes eutrophus CnrH, E. coli FecI, and Bacillus subtilis SigX, a protein of unknown function. These eight proteins define a subfamily of eubacterial RNA polymerase factors sufficiently different from other σs that, in many cases, they are not identified by standard similarity searching methods. Available information suggests that all of them regulate extracytoplasmic functions and that they function as effector molecules responding to extracytoplasmic stimuli. A. eutrophus CnrH appears to be a plasmid-encoded factor.

Original languageEnglish (US)
Pages (from-to)7573-7577
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number16
StatePublished - Aug 2 1994


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