The regulatory region of the Bacillus subtilis glucitol dehydrogenase (gutB) gene was divided into three subregions: a promoter, an upstream positive regulatory region, and a downstream negative regulatory region. Data from primer extension, deletion, and site-directed mutagenesis analyses were consistent with two possible models for the gutB promoter. It is either a sigma A-type promoter with an unusually short spacer region (15 bp) or a special sigma A promoter which requires only the hexameric -10 sequence for its function. Sequence carrying just the promoter region (from -48 to +6) failed to direct transcription in vivo. An upstream regulatory sequence was essential for glucitol induction. When this sequence was inserted in a high-copy-number plasmid, an effect characteristic of titration of a transcriptional activator was seen. Downstream from the promoter, there is an imperfect, AT-rich inverted repeat sequence. Deletion of this element did not lead to constitutive expression of gutB. However, the induced gutB expression level was enhanced three- to fourfold.
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