CLONING, FUNCTIONAL-ANALYSIS, AND TRANSCRIPTIONAL REGULATION OF THE BACILLUS-SUBTILIS ARAE GENE INVOLVED IN L-ARABINOSE UTILIZATION

The Bacillus subtilis araR locus (mapped at about 294 degrees on the g enetic map) comprises two open reading frames with divergently arrange d promoters, the regulatory gene, araR, encoding a repressor, and a pa rtially cloned gene, termed araE by analogy to the Escherichia coli L- arabinose permease gene, Here, ive report the cloning and sequencing o f the entire araE gene encoding a 50.4-kDa polypeptide. The araE gene is monocistronic (as determined by Northern blot analysis), and its pu tative product is very similar to a number of prokaryotic proton-linke d monosaccharide transporters (the group I family of membrane transpor t proteins), Insertional inactivation of the araE gene leads to a cond itional Ara-phenotype dependent on the concentration of L-arabinose in the medium, Therefore, we assume that araE encodes a permease involve d in L-arabinose transport into the cell. The araE promoter region con tains -10 and -35 regions (as determined by primer extension analysis) very similar to those recognized by RNA polymerase containing the maj or vegetative-cell sigma factor sigma(A) and the -35 region of the tra nscription start point for araE is located 2 bp from the -35 region of the araR gene, Transcriptional studies demonstrated that the expressi on from the araE promoter is induced by L-arabinose, repressed by gluc ose, and negatively regulated by AraR. These observations are consiste nt with a model according to which in the absence of L-arabinose, AraR binds to a site(s) within the araE/araR promoter; preventing transcri ption from the araE promoter and simultaneously limiting the frequency of initiation from its own promoter; the addition of L-arabinose will allow transcription from the araE promoter and increase the frequency of initiation from the araR promoter.