A Broad-Specificity Multidrug Efflux Pump Requiring a Pair of Homologous SMR-Type Proteins

Abstract

The Bacillus subtilis genome encodes seven homologues of the small multidrug resistance (SMR) family of drug efflux pumps. Six of these homologues are paired in three distinct operons, and coexpression in Escherichia coli of one such operon, ykkCD, but not expression of either ykkC or ykkD alone, gives rise to a broad specificity, multidrug-resistant phenotype including resistance to cationic, anionic, and neutral drugs.