@article {Ecker1169, author = {Gerhard F. Ecker and Karin Pleban and Stephan Kopp and Edina Csaszar and Gerrit J. Poelarends and Monique Putman and Dominik Kaiser and Wil N. Konings and Peter Chiba}, title = {A Three-Dimensional Model for the Substrate Binding Domain of the Multidrug ATP Binding Cassette Transporter LmrA}, volume = {66}, number = {5}, pages = {1169--1179}, year = {2004}, doi = {10.1124/mol.104.001420}, publisher = {American Society for Pharmacology and Experimental Therapeutics}, abstract = {Multidrug resistance presents a major obstacle to the treatment of infectious diseases and cancer. LmrA, a bacterial ATP-dependent multidrug transporter, mediates efflux of hydrophobic cationic substrates, including antibiotics. The substrate-binding domain of LmrA was identified by using photo-affinity ligands, proteolytic degradation of LmrA, and identification of ligand-modified peptide fragments with matrix-assisted laser desorption ionization/time of flight mass spectrometry. In the nonenergized state, labeling occurred in the α-helical transmembrane segments (TM) 3, 5 and 6 of the membrane-spanning domain. Upon nucleotide binding, the accessibility of TM5 for substrates increased, whereas that of TM6 decreased. Inverse changes were observed upon ATP-hydrolysis. An atomic-detail model of dimeric LmrA was generated based on the template structure of the homologous transporter MsbA from Vibrio cholerae, allowing a three-dimensional visualization of the substrate-binding domain. Labeling of TM3 of one monomer occurred in a predicted area of contact with TM5 or TM6 of the opposite monomer, indicating substrate-binding at the monomer/monomer interface. Inverse changes in the reactivity of TM segments 5 and 6 suggest that substrate binding and release involves a repositioning of these helices during the catalytic cycle.}, issn = {0026-895X}, URL = {https://molpharm.aspetjournals.org/content/66/5/1169}, eprint = {https://molpharm.aspetjournals.org/content/66/5/1169.full.pdf}, journal = {Molecular Pharmacology} }