Expression of the bglH gene of Lactobacillus plantarum is controlled by carbon catabolite repression.

A newly identified bglH gene coding for a phospho-beta-glucosidase of Lactobacillus plantarum was isolated and expressed in Escherichia coli. The sequence analysis of the cloned DNA fragment showed an open reading frame encoding a 480-amino-acid protein with a calculated molecular mass of 53 kDa. The bglH gene was shown to be expressed on a monocistronic transcriptional unit. Its transcription was repressed 10-fold in L. plantarum cells grown on glucose compared to the beta-glucoside salicin as a sole carbon source. A catabolite-responsive element (CRE) spanning from -3 to +11 with respect to the transcriptional start point was found, and its functionality was assessed by mutational analysis. In vitro and in vivo DNA binding experiments suggested the occurrence of a DNA-protein complex at the CRE site, which would mediate glucose repression of bglH expression.