title: Structural basis of energy transduction in the transport cycle of MsbA.
abstract: We used site-directed spin-labeling and electron paramagnetic resonance spectroscopy to characterize the conformational motion that couples energy expenditure to substrate translocation in the multidrug transporter MsbA. In liposomes, ligand-free MsbA samples conformations that depart from the crystal structures, including looser packing and water penetration along the periplasmic side. Adenosine triphosphate (ATP) binding closes the substrate chamber to the cytoplasm while increasing hydration at the periplasmic side, consistent with an alternating access model. Accentuated by ATP hydrolysis, the changes in the chamber dielectric environment and its geometry provide the likely driving force for flipping amphipathic substrates and a potential exit pathway. These results establish the structural dynamic basis of the power stroke in multidrug-resistant ATP-binding cassette (MDR ABC) transporters.
authors.affiliation: Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, TN 37232, USA.
authors.forename: Jinhui
authors.initials: J
authors.lastname: Dong
authors.forename: Guangyong
authors.initials: G
authors.lastname: Yang
authors.forename: Hassane S
authors.initials: HS
authors.lastname: McHaourab
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000737:chemistry* / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism*; D001059:Apoproteins / Q000737:chemistry / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism*; D001692:Biological Transport; D002462:Cell Membrane / Q000737:chemistry / Q000378:metabolism; D003593:Cytoplasm / Q000737:chemistry; D019281:Dimerization; D004492:Edetic Acid / Q000031:analogs & derivatives*; D004578:Electron Spin Resonance Spectroscopy; D004734:Energy Metabolism; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000378:metabolism; D006868:Hydrolysis; D008024:Ligands; D008050:Lipid A / Q000378:metabolism; D008051:Lipid Bilayers; D008081:Liposomes / Q000737:chemistry*; D008958:Models, Molecular; D010100:Oxygen / Q000378:metabolism; D019897:Periplasm / Q000737:chemistry; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D013113:Spin Labels; D013816:Thermodynamics; D014638:Vanadates / Q000378:metabolism
chemical_list: D018528:ATP-Binding Cassette Transporters; D001059:Apoproteins; D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D008024:Ligands; D008050:Lipid A; D008051:Lipid Bilayers; D008081:Liposomes; C079726:MsbA protein, Bacteria; D013113:Spin Labels; D014638:Vanadates; C026058:EDDA; D000255:Adenosine Triphosphate; D004492:Edetic Acid; D010100:Oxygen