FIGURE 1.

Structure of an RND efflux pump. The figure shows a scheme of the structure of the E. coli AcrAB-TolC system. As shown, the system is a tripartite complex formed by the inner membrane AcrB protein, the outer membrane protein TolC and the membrane fusion protein AcrA. The activity of the AcrB RND protein is coupled to the proton gradient. It has been shown that these efflux pumps can extrude different compounds form the bacterial cytoplasm and the periplasm. Adapted from Blair and Piddock (2009).