Cloning and characterization of the rpoH gene of Rhodobacter capsulatus.
By using an oligonucleotide mixture corresponding to a region highly conserved among alternative sigma factors we identified a new sigma factor gene (rpoH) from Rhodobacter capsulatus. This gene encodes a protein of 34 kDa with strong similarity to the RpoH (sigma32) factors from other bacterial species. It was not possible to inactivate the R. capsulatus rpoH gene by introducing a resistance cassette, implying that it is essential for growth. The 5' ends of the mRNAs were mapped to two sequences with similarity to an rpoH- and an rpoD-dependent promoter, respectively. The amounts of both these mRNAs increased after heat shock, but were unaffected by a decrease in oxygen tension. Western analysis using a sigma factor-specific antibody revealed the accumulation of a protein of about 34 kDa after heat shock, and an increase in the amounts of a protein with the same size after reduction of oxygen tension in R. capsulatus cultures.
Emetz
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Institut für Mikrobiologie und Molekularbiologie, Giessen, Germany.
Klug
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D000595:Amino Acid Sequence; D003001:Cloning, Molecular; D015964:Gene Expression Regulation, Bacterial; D006360:Heat-Shock Proteins / Q000235:genetics* / Q000378:metabolism; D006358:Hot Temperature; D008969:Molecular Sequence Data; D010100:Oxygen / Q000378:metabolism; D016354:Rhodobacter capsulatus / Q000737:chemistry / Q000235:genetics* / Q000254:growth & development; D017421:Sequence Analysis; D017386:Sequence Homology, Amino Acid; D012808:Sigma Factor; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism
D006360:Heat-Shock Proteins; D012808:Sigma Factor; D014157:Transcription Factors; C069774:heat-shock sigma factor 32; D010100:Oxygen