ISOLATION OF THE 2ND BACILLUS-THURINGIENSIS RNA-POLYMERASE THAT TRANSCRIBES FROM A CRYSTAL PROTEIN GENE PROMOTER

A crystal protein gene of Bacillus thuringiensis subsp. kurstaki HD-1-Dipel is transcribed in vivo from two overlapping promoters that are activated at different times during sporulation. We reported earlier (K.L. Brown and H.R. Whiteley, Proc. Natl. Acad. Sci. USA 85:4166-4170, 1988) that an RNA polymerase containing a σ subunit with an apparent M(r) of 35,000 can transcribe in vitro from the promoter utilized from early to midsporulation. We now report the isolation of an RNA polymerase containing a σ subunit with an M(r) of ca. 28,000; this polymerase activates transcription in vitro from the promoter used from mid- to late sporulation. This form of RNA polymerase also directs transcription in vitro from promoters preceding two other crystal protein genes and a gene coding for a spore coat protein. On the basis of a comparison of the four promoters, we propose the following consensus sequence of the -10 region recognized by RNA polymerase containing the M(r)-28,000 σ subunit: 5'-TNATANNaTGag-3'. No consensus sequence could be derived for the -35 region. When the N-terminal amino acid sequence of the σ28 polypeptide was aligned with the amino acid sequence of known σ subunits, significant homology was found with the N terminus of the mature form of the σ(K) subunit of RNA polymerase isolated from sporulating cells of Bacillus subtilis.