Cloning and characterization of the rpoH gene of Rhodobacter capsulatus
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- Emetz, D. & Klug, G. Mol Gen Genet (1998) 260: 212. doi:10.1007/s004380050888
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By using an oligonucleotide mixture corresponding to a region highly conserved among alternative sigma factors we identified a new σ factor gene (rpoH) from Rhodobacter capsulatus. This gene encodes a protein of 34 kDa with strong similarity to the RpoH (σ32) factors from other bacterial species. It was not possible to inactivate the R. capsulatusrpoH 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 σ 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.