MULTIDRUG-RESISTANCE PUMPS IN BACTERIA - VARIATIONS ON A THEME

Multidrug resistance pumps (MDRs) arise from three different gene fami lies and are widespread in bacteria. For example, in Escherichia coli alone, there seem to be seven distinct MDRs. The most common belong to the major facilitator family of membrane translocases; this type of M DR is closely related to specific antibiotic extrusion pumps such as t he tetracycline/H+ antiporter. This similarity in design, and the high incidence of apparently independent evolution of MDRs, suggests that the property of multidrug resistance might have resulted from a loss o f specificity in a specific hydrophobic-drug efflux pump.