SIGMA(E) CHANGED TO SIGMA(B) SPECIFICITY BY AMINO-ACID SUBSTITUTIONS IN ITS -10 BINDING REGION

The association of a sigma factor (sigma) with RNA polymerase in bacte ria determines its specificity of promoter utilization. To identify am ino acid residues in sigma(E) from Bacillus subtilis that determine th e specificity of its interaction with the nucleotides at the -10 regio n of its cognate promoters, we tested whether base pair substitutions in the -10 region of a sigma(B)-dependent promoter could signal its ut ilization by sigma(E)-RNA polymerase. We found that a combination of b ase pair substitutions at positions -15 and -14 of the sigma(B)-depend ent etc promoter resulted in its utilization by sigma(E)-RNA polymeras e in vivo, We also found that the combination of two amino acid substi tutions at positions 119 and 120 in sigma(E) changed its specificity f or promoter utilization, resulting in a sigma factor that directed tra nscription from the sigma(E)-dependent etc promoter, but not from sigm a(E)-dependent promoters. These results suggest that amino acid residu es at positions 119 and 120 determine, at least in part, the specifici ty of interactions between sigma(E) and the nucleotides in the -10 reg ion of its cognate promoters.