3w9j
Structural basis for the inhibition of bacterial multidrug exporters
Structural highlights
FunctionMEXB_PSEAE The inner membrane transporter component of the MexAB-OprM efflux system that confers multidrug resistance. Also functions as the major efflux pump for n-hexane and p-xylene efflux. Over-expression of the pump increases antibiotic and solvent efflux capacities. Implicated in the secretion of the siderophore pyoverdine.[1] [2] [3] The ability to export antibiotics and solvents is dramatically decreased in the presence of the proton conductor carbonyl cyanide m-chlorophenylhydrazone (CCCP), showing that an energized inner membrane is required for efflux. It is thought that the MexB subunit is a proton antiporter.[4] [5] [6] Publication Abstract from PubMedThe multidrug efflux transporter AcrB and its homologues are important in the multidrug resistance of Gram-negative pathogens. However, despite efforts to develop efflux inhibitors, clinically useful inhibitors are not available at present. Pyridopyrimidine derivatives are AcrB- and MexB-specific inhibitors that do not inhibit MexY; MexB and MexY are principal multidrug exporters in Pseudomonas aeruginosa. We have previously determined the crystal structure of AcrB in the absence and presence of antibiotics. Drugs were shown to be exported by a functionally rotating mechanism through tandem proximal and distal multisite drug-binding pockets. Here we describe the first inhibitor-bound structures of AcrB and MexB, in which these proteins are bound by a pyridopyrimidine derivative. The pyridopyrimidine derivative binds tightly to a narrow pit composed of a phenylalanine cluster located in the distal pocket and sterically hinders the functional rotation. This pit is a hydrophobic trap that branches off from the substrate-translocation channel. Phe 178 is located at the edge of this trap in AcrB and MexB and contributes to the tight binding of the inhibitor molecule through a pi-pi interaction with the pyridopyrimidine ring. The voluminous side chain of Trp 177 located at the corresponding position in MexY prevents inhibitor binding. The structure of the hydrophobic trap described in this study will contribute to the development of universal inhibitors of MexB and MexY in P. aeruginosa. Structural basis for the inhibition of bacterial multidrug exporters.,Nakashima R, Sakurai K, Yamasaki S, Hayashi K, Nagata C, Hoshino K, Onodera Y, Nishino K, Yamaguchi A Nature. 2013 Aug 1;500(7460):102-6. doi: 10.1038/nature12300. Epub 2013 Jun 30. PMID:23812586[7] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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