The choreography of multidrug export

Abstract

Multidrug transporters have a crucial role in causing the drug resistance that can arise in infectious micro-organisms and tumours. These integral membrane proteins mediate the export of a broad range of unrelated compounds from cells, including antibiotics and anticancer agents, thus reducing the concentration of these compounds to subtoxic levels in target cells. In spite of intensive research, it is not clear exactly how multidrug transporters work. The present review focuses on recent advancements in the biochemistry and structural biology of bacterial and human multidrug ABC (ATP-binding cassette) transporters. These advancements point to a common mechanism in which polyspecific drug-binding surfaces in the membrane domains are alternately exposed to the inside and outside surface of the membrane in response to the ATP-driven dimerization of nucleotide-binding domains and their dissociation following ATP hydrolysis.

Substrate Binding Stabilizes a Pre-translocation Intermediate in the ATP-binding Cassette Transport Protein MsbA

“…These studies provide an overall view of the dynamic movements associated with an ATP hydrolysis (ATPase) cycle that is in agreement with an alternating access model of transport (1,7,16). Briefly, this model suggests that an ABC exporter alternates between an inward-facing and outward-facing conformation to present the substrate-binding pocket in the MDs to the inside and outside of the cell, respectively.…”

“…Substrate Binding to MsbA Causes NBD Dimerization-We previously described the use of inter-molecular cysteine crosslinking between E208C and E208CЈ in the cysteine-less MsbA (MsbA-cl) homodimer in ISOVs to dissect the conformational changes associated with the ATPase cycle in the absence of added transport substrates (13,14,16). Here, we used this assay to test the effect of typical MsbA substrates, including Hoechst 33342 and verapamil and the physiological substrate lipid A (2,3,5,6,26,28), in the absence of added nucleotides.…”

Molecular Disruption of the Power Stroke in the ATP-binding Cassette Transport Protein MsbA

“…transporter returns to an inward-facing conformation in the presence of ADP alone (38). Based on these nucleotide-dependent cross-linking/labeling data obtained under near-physiological conditions, we conclude that cysteines at position Ala-281 in MsbA can be used to detect the conformational switch associated with nucleotide-dependent wing formation in the MDs.…”

Mechanisms of resistance to antimicrobial peptides in staphylococci

“…In many organisms, multi-drug exporters with broad substrate specificity provide resistance to a variety of antimicrobial compounds [88]. Although many transporters have been discovered in staphylococci that confer resistance to antibiotics [89], most staphylococcal multi-drug exporters are not active against human AMPs.…”