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The homodimeric ATP‐binding cassette transporter LmrA mediates multidrug transport by an alternating two‐site (two‐cylinder engine) mechanism
Author(s) -
van Veen Hendrik W.,
Margolles Abelardo,
Müller Michael,
Higgins Christopher F.,
Konings Wil N.
Publication year - 2000
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1093/emboj/19.11.2503
Subject(s) - atp binding cassette transporter , atp hydrolysis , biology , p glycoprotein , binding site , transporter , biophysics , biochemistry , transport protein , multiple drug resistance , efflux , plasma protein binding , enzyme , atpase , gene , antibiotics
The bacterial LmrA protein and the mammalian multidrug resistance P‐glycoprotein are closely related ATP‐binding cassette (ABC) transporters that confer multidrug resistance on cells by mediating the extrusion of drugs at the expense of ATP hydrolysis. The mechanisms by which transport is mediated, and by which ATP hydrolysis is coupled to drug transport, are not known. Based on equilibrium binding experiments, photoaffinity labeling and drug transport assays, we conclude that homodimeric LmrA mediates drug transport by an alternating two‐site transport (two‐cylinder engine) mechanism. The transporter possesses two drug‐binding sites: a transport‐competent site on the inner membrane surface and a drug‐release site on the outer membrane surface. The interconversion of these two sites, driven by the hydrolysis of ATP, occurs via a catalytic transition state intermediate in which the drug transport site is occluded. The mechanism proposed for LmrA may also be relevant for P‐glycoprotein and other ABC transporters.