Multidrug transporter MdfA and similar multidrug resistance (MDR) transporters of the Major Facilitator Superfamily
This family is composed of bacterial multidrug resistance (MDR) transporters including several proteins from Escherichia coli such as MdfA (also called chloramphenicol resistance pump Cmr), EmrD, MdtM, MdtL, bicyclomycin resistance protein (also called sulfonamide resistance protein), and the uncharacterized inner membrane transport protein YdhC. EmrD is a proton-dependent secondary transporter, first identified as an efflux pump for uncouplers of oxidative phosphorylation. It expels a range of drug molecules and amphipathic compounds across the inner membrane of E. coli. Similarly, MdfA is a secondary multidrug transporter that exports a broad spectrum of structurally and electrically dissimilar toxic compounds. These MDR transporters are drug/H+ antiporters (DHA) belonging to the Major Facilitator Superfamily (MFS) of membrane transport proteins, which are thought to function through a single substrate binding site, alternating-access mechanism involving a rocker-switch type of movement.
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