title: Energy transduction and alternating access of the mammalian ABC transporter P-glycoprotein.
abstract: ATP binding cassette (ABC) transporters of the exporter class harness the energy of ATP hydrolysis in the nucleotide-binding domains (NBDs) to power the energetically uphill efflux of substrates by a dedicated transmembrane domain (TMD). Although numerous investigations have described the mechanism of ATP hydrolysis and defined the architecture of ABC exporters, a detailed structural dynamic understanding of the transduction of ATP energy to the work of substrate translocation remains elusive. Here we used double electron-electron resonance and molecular dynamics simulations to describe the ATP- and substrate-coupled conformational cycle of the mouse ABC efflux transporter P-glycoprotein (Pgp; also known as ABCB1), which has a central role in the clearance of xenobiotics and in cancer resistance to chemotherapy. Pairs of spin labels were introduced at residues selected to track the putative inward-facing to outward-facing transition. Our findings illuminate how ATP energy is harnessed in the NBDs in a two-stroke cycle and elucidate the consequent conformational motion that reconfigures the TMD, two critical aspects of Pgp transport mechanism. Along with a fully atomistic model of the outward-facing conformation in membranes, the insight into Pgp conformational dynamics harmonizes mechanistic and structural data into a novel perspective on ATP-coupled transport and reveals mechanistic divergence within the efflux class of ABC transporters.
authors.affiliation: Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee 37232, USA.
authors.forename: Brandy
authors.initials: B
authors.lastname: Verhalen
authors.affiliation: Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee 37232, USA.
authors.forename: Reza
authors.initials: R
authors.lastname: Dastvan
authors.affiliation: Department of Biochemistry, Center for Biophysics and Quantitative Biology, and Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
authors.forename: Sundarapandian
authors.initials: S
authors.lastname: Thangapandian
authors.affiliation: Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, Virginia 22908, USA.
authors.forename: Yelena
authors.initials: Y
authors.lastname: Peskova
authors.affiliation: Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee 37232, USA.
authors.forename: Hanane A
authors.initials: HA
authors.lastname: Koteiche
authors.affiliation: Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, Virginia 22908, USA.
authors.forename: Robert K
authors.initials: RK
authors.lastname: Nakamoto
authors.affiliation: Department of Biochemistry, Center for Biophysics and Quantitative Biology, and Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
authors.forename: Emad
authors.initials: E
authors.lastname: Tajkhorshid
authors.affiliation: Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee 37232, USA.
authors.forename: Hassane S
authors.initials: HS
authors.lastname: Mchaourab
mesh_terms: D018435:ATP Binding Cassette Transporter, Subfamily B / Q000737:chemistry* / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D055162:Biocatalysis; D004583:Electrons; D051379:Mice; D008958:Models, Molecular; D056004:Molecular Dynamics Simulation; D013113:Spin Labels
chemical_list: D018435:ATP Binding Cassette Transporter, Subfamily B; D013113:Spin Labels; D000255:Adenosine Triphosphate; C095122:multidrug resistance protein 3