title: Horizontal membrane-intrinsic α-helices in the stator a-subunit of an F-type ATP synthase.
abstract: ATP, the universal energy currency of cells, is produced by F-type ATP synthases, which are ancient, membrane-bound nanomachines. F-type ATP synthases use the energy of a transmembrane electrochemical gradient to generate ATP by rotary catalysis. Protons moving across the membrane drive a rotor ring composed of 8-15 c-subunits. A central stalk transmits the rotation of the c-ring to the catalytic F1 head, where a series of conformational changes results in ATP synthesis. A key unresolved question in this fundamental process is how protons pass through the membrane to drive ATP production. Mitochondrial ATP synthases form V-shaped homodimers in cristae membranes. Here we report the structure of a native and active mitochondrial ATP synthase dimer, determined by single-particle electron cryomicroscopy at 6.2 Å resolution. Our structure shows four long, horizontal membrane-intrinsic α-helices in the a-subunit, arranged in two hairpins at an angle of approximately 70° relative to the c-ring helices. It has been proposed that a strictly conserved membrane-embedded arginine in the a-subunit couples proton translocation to c-ring rotation. A fit of the conserved carboxy-terminal a-subunit sequence places the conserved arginine next to a proton-binding c-subunit glutamate. The map shows a slanting solvent-accessible channel that extends from the mitochondrial matrix to the conserved arginine. Another hydrophilic cavity on the lumenal membrane surface defines a direct route for the protons to an essential histidine-glutamate pair. Our results provide unique new insights into the structure and function of rotary ATP synthases and explain how ATP production is coupled to proton translocation.
authors.affiliation: Department of Structural Biology, Max Planck Institute of Biophysics, Max-von-Laue-Strasse 3, 60438 Frankfurt am Main, Germany.
authors.forename: Matteo
authors.initials: M
authors.lastname: Allegretti
authors.affiliation: Department of Structural Biology, Max Planck Institute of Biophysics, Max-von-Laue-Strasse 3, 60438 Frankfurt am Main, Germany.
authors.forename: Niklas
authors.initials: N
authors.lastname: Klusch
authors.affiliation: Department of Structural Biology, Max Planck Institute of Biophysics, Max-von-Laue-Strasse 3, 60438 Frankfurt am Main, Germany.
authors.forename: Deryck J
authors.initials: DJ
authors.lastname: Mills
authors.affiliation: Department of Structural Biology, Max Planck Institute of Biophysics, Max-von-Laue-Strasse 3, 60438 Frankfurt am Main, Germany.
authors.forename: Janet
authors.initials: J
authors.lastname: Vonck
authors.affiliation: Department of Structural Biology, Max Planck Institute of Biophysics, Max-von-Laue-Strasse 3, 60438 Frankfurt am Main, Germany.
authors.forename: Werner
authors.initials: W
authors.lastname: Kühlbrandt
authors.affiliation: Department of Structural Biology, Max Planck Institute of Biophysics, Max-von-Laue-Strasse 3, 60438 Frankfurt am Main, Germany.
authors.forename: Karen M
authors.initials: KM
authors.lastname: Davies
mesh_terms: D000255:Adenosine Triphosphate / Q000096:biosynthesis / Q000378:metabolism; D001120:Arginine / Q000378:metabolism; D000460:Chlorophyta / Q000201:enzymology*; D020285:Cryoelectron Microscopy; D018698:Glutamic Acid / Q000378:metabolism; D006639:Histidine / Q000378:metabolism; D017136:Ion Transport; D008051:Lipid Bilayers / Q000737:chemistry / Q000378:metabolism; D008958:Models, Molecular; D055503:Protein Multimerization; D017433:Protein Structure, Secondary; D021122:Protein Subunits / Q000737:chemistry* / Q000378:metabolism; D006180:Proton-Translocating ATPases / Q000737:chemistry* / Q000378:metabolism / Q000648:ultrastructure*; D011522:Protons; D012399:Rotation; D014867:Water / Q000378:metabolism
chemical_list: D008051:Lipid Bilayers; D021122:Protein Subunits; D011522:Protons; D014867:Water; D018698:Glutamic Acid; D006639:Histidine; D000255:Adenosine Triphosphate; D001120:Arginine; D006180:Proton-Translocating ATPases