The nucleotide sequence of the bacteriocin promoters of plasmids Clo DF13 and Col El: role of lexA repressor and cAMP in the regulation of promoter activity

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Abstract
Treatment of cells, harbouring the bacteriocinogenic plasmid Clo DF13 with mitomycin-C, which induces the cellulair SOS response, results in a significantly increased transcription of the operon encoding the bacteriocin cloacin DF13, the immunity protein and the lysis protein H. The nucleotide sequences of the promoter regions and N-terminal parts of the bacteriocin genes of Clo DF13, Col El and the pMB1 derivative pBR324 have been determined. A comparison of these sequences with those of corresponding regions of the lexA, recA and uvrB genes revealed that the promoter regions of the bacteriocin genes studied contain binding sites for the lexA protein, which is the repressor of the E. coli DNA-repair system. Using both, a thermosensltive lexA host strain and a host with pACYC184 into which the lexA gene had been cloned, we were able to demonstrate, that invivo the lexA protein is involved in the regulation of bacteriocin synthesis. From the data presented, we conclude that bacteriocin synthesis is controlled at least by the lexA repressor. It has been reported that also catabolite repression might play an essential role in the control of bacteriocin synthesis. Computer analysis of the DNA sequence data indicated that the promoter regions of both, the cloacin DF13 and colicln El genes contain potential binding sites for the cyclic AMP-cyclic AMP Receptor Protein complex.