The -16 region of Bacillus subtilis and other gram-positive bacterial promoters

The Bacillus subtilis alpha-amylase promoter amy P contains an essential TGTG motif (-16 region) upstream of the -10 region. Mutations of this region significantly reduced in vitro promoter strength. A -15 G-->C transversion eliminated transcription from amy P by both B.subtilis and Escherichia coli RNA polymerase (RNAP). A second alpha-amylase promoter ( amy P2) also required the -16 region for function. To determine conserved sequences in promoters containing -16 region elements, sequences of 64 B.subtilis promoters with the second TG motif of the -16 region were aligned and analyzed. Unlike the E.coli class of 'extended -10 promoters', with a similar TG motif but lacking a -35 region, the -16 region promoters contain highly conserved -35 regions. They also contain conserved A n and T n tracts upstream of the -35 region. In addition, we analyzed all available gram-positive bacterial promoter compilations to determine the generality of the -16 region. From this analysis, the -16 region TRTG motif (R = purine) appears to be a basic element found in a large portion of gram-positive bacterial promoters and is, in the case of at least the alpha-amylase promoters, necessary for transcription by the major form of B.subtilis and E.coli RNAP.