title: Atomic-level characterization of transport cycle thermodynamics in the glycerol-3-phosphate:phosphate antiporter.
abstract: Membrane transporters actively translocate their substrate by undergoing large-scale structural transitions between inward- (IF) and outward-facing (OF) states ('alternating-access' mechanism). Despite extensive structural studies, atomic-level mechanistic details of such structural transitions, and as importantly, their coupling to chemical events supplying the energy, remain amongst the most elusive aspects of the function of these proteins. Here we present a quantitative, atomic-level description of the functional thermodynamic cycle for the glycerol-3-phosphate:phosphate antiporter GlpT by using a novel approach in reconstructing the free energy landscape governing the IF↔OF transition along a cyclic transition pathway involving both apo and substrate-bound states. Our results provide a fully atomic description of the complete transport process, offering a structural model for the alternating-access mechanism and substantiating the close coupling between global structural transitions and local chemical events.
authors.affiliation: Department of Biochemistry, Beckman Institute for Advanced Science and Technology, and Center for Biophysics and Computational Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
authors.forename: Mahmoud
authors.initials: M
authors.lastname: Moradi
authors.affiliation: Department of Biochemistry, Beckman Institute for Advanced Science and Technology, and Center for Biophysics and Computational Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
authors.forename: Giray
authors.initials: G
authors.lastname: Enkavi
authors.affiliation: Department of Biochemistry, Beckman Institute for Advanced Science and Technology, and Center for Biophysics and Computational Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
authors.forename: Emad
authors.identifier: http://orcid.org/0000-0001-8434-1010
authors.initials: E
authors.lastname: Tajkhorshid
mesh_terms: D017920:Antiporters / Q000737:chemistry* / Q000378:metabolism; D001692:Biological Transport; D005990:Glycerol / Q000378:metabolism*; D056004:Molecular Dynamics Simulation; D010710:Phosphates / Q000378:metabolism*; D011487:Protein Conformation; D013816:Thermodynamics
chemical_list: D017920:Antiporters; D010710:Phosphates; D005990:Glycerol