Characterization of MarR, the repressor of the multiple antibiotic resistance (mar) operon in Escherichia coli

Transcriptional fusion of marOII-lacZ into the chromosome of wild-type and purified marR mutants was examined to determine the factors affecting the expression of the marRAB operon in Escherichia coli. Wild-type cells exhibited a two- to seven-fold increase in LacZ expression, while mar-deleted cells exhibited a 20-fold increase. Results of the fusion of MarR with a fusion protein MarE indicated repressor ability and a dissociation constant of 5 x 10(sub -9) M, suggesting that repression in cells are reversed to facilitate the response of the bacteria to stress.