The <i>Escherichia coli cmlA</i> Gene Encodes the Multidrug Efflux Pump Cmr/MdfA and Is Responsible for Isopropyl-β- <scp>d</scp> -Thiogalactopyranoside Exclusion and Spectinomycin Sensitivity

Abstract

Expression of cloned genes from isopropyl-beta-D-thiogalactopyranoside (IPTG)-regulated promoters is lowered when the Escherichia coli CmlA/Cmr/MdfA efflux pump is overexpressed, probably due to IPTG exclusion from the cytoplasm. The previously reported cmlA1 mutation confers a similar phenotype. cmlA1 contains an IS30 insertion upstream of cmr/mdfA, which creates a putative promoter. CmlA overproduction also causes spectinomycin hypersensitivity.