Isolation and physical mapping of the gene encoding the major sigma factor of Bacillus subtilis RNA polymerase.

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Abstract
At least 4 .sigma. factors separately bind the B. subtilis RNA polymerase core (.beta..beta.''.alpha.2), each conferring a different promoter specificity on the holoenzyme in vitro. Using the Broome-Gilbert immunological screening, one isolated recombinant .lambda. phages that carry rpoD, the gene for the most abundant .sigma. factor, .sigma.55. These phages encode a 55,000-dalton protein whose size, immunological properties and peptide map identify it as .sigma.55. All the phages have in common 2 adjacent 3.5-kilobase EcoRI fragments from the B. subtilis chromosome; most carry additional genomic DNA. Deletion analysis localized rpoD to a 1.6-kilobase region, suggested the direction of its transcription and found 2 additional genes near rpoD, which code for proteins of 62,000 and 17,000 daltons.