Characterization of the sacQ genes from Bacillus licheniformis and Bacillus subtilis

The sacQ gene from Bacillus licheniformis was cloned and expressed in Bacillus subtilis. Deletion analysis shows that it encodes a 46-amino-acid polypeptide homologous to the B. subtilis sacQ gene product. The polypeptide, when it is overexpressed, activates the expression of a number of target genes in B. subtilis, all encoding secreted enzymes: alkaline protease, levansucrase, beta-glucanase(s), xylanase, and alpha-amylase. The maximum stimulations measured for alkaline protease and levansucrase were by a factor of 70 and 50, respectively, when the sacQ gene from B. licheniformis was present on a multicopy plasmid in B. subtilis. The sacQ genes from B. subtilis and B. licheniformis, cloned in the same multicopy plasmid, were compared under the same conditions. The sacQ gene from B. licheniformis was more efficient than the sacQ gene from B. subtilis in producing the hypersecretion phenotype. The sacQ structural genes from B. subtilis and B. licheniformis were placed under the control of the same inducible promoter. Hypersecretion was specifically obtained under conditions of full induction of the promoter. The target site of levansucrase regulation by sacQ was identified as a 440-base-pair fragment located in the 5' noncoding region of sacB, suggesting transcriptional control.