PepR1, a CcpA-like transcription regulator of Lactobacillus delbrueckii subsp. lactis.

The PepR1 protein from Lactobacillus delbrueckii subsp. lactis DSM 7290 shares extensive homology with catabolite-control proteins from various Gram-positive bacteria. Expression of the subcloned pepR1 gene allowed for partial complementation of a ccpA defect in Staphylococcus xylosus. The influence of PepR1 on transcription of the prolidase gene pepQ, which is located adjacent to pepR1, was examined by use of lacZ reporter gene fusions in Escherichia coli. PepR1 stimulated transcription initiation at the pepQ promoter about twofold, and this effect required the integrity of a 14 bp palindromic cre-like sequence located 74 nt upstream of pepQ. In gel-mobility-shift assays, PepR1 specifically interacted with the pepQ promoter region and also with DNA fragments covering the promoters of the pepX, pepl and brnQ genes of Lb. delbrueckii subsp. lactis, which encode two additional peptidases and a branched-chain amino acid transporter, respectively. cre-like elements were identified in each of these DNA fragments. Catabolite control of PepQ was demonstrated in Lb. delbrueckii subsp. lactis. During growth with lactose the enzyme activity was twofold higher than in the presence of glucose, and corresponding differences were also detected in the level of pepQ transcription.