title: F1-ATPase conformational cycle from simultaneous single-molecule FRET and rotation measurements.
abstract: Despite extensive studies, the structural basis for the mechanochemical coupling in the rotary molecular motor F1-ATPase (F1) is still incomplete. We performed single-molecule FRET measurements to monitor conformational changes in the stator ring-α3β3, while simultaneously monitoring rotations of the central shaft-γ. In the ATP waiting dwell, two of three β-subunits simultaneously adopt low FRET nonclosed forms. By contrast, in the catalytic intermediate dwell, two β-subunits are simultaneously in a high FRET closed form. These differences allow us to assign crystal structures directly to both major dwell states, thus resolving a long-standing issue and establishing a firm connection between F1 structure and the rotation angle of the motor. Remarkably, a structure of F1 in an ε-inhibited state is consistent with the unique FRET signature of the ATP waiting dwell, while most crystal structures capture the structure in the catalytic dwell. Principal component analysis of the available crystal structures further clarifies the five-step conformational transitions of the αβ-dimer in the ATPase cycle, highlighting the two dominant modes: the opening/closing motions of β and the loosening/tightening motions at the αβ-interface. These results provide a new view of tripartite coupling among chemical reactions, stator conformations, and rotary angles in F1-ATPase.
authors.affiliation: Department of Physics, Faculty of Science, Gakushuin University, Tokyo 171-8588, Japan; mitsuhiro.sugawa@bio.c.u-tokyo.ac.jp takayuki.nishizaka@gakushuin.ac.jp.
authors.forename: Mitsuhiro
authors.initials: M
authors.lastname: Sugawa
authors.affiliation: Department of Theoretical Biophysics, Max Planck Institute of Biophysics, 60438 Frankfurt am Main, Germany;
authors.forename: Kei-Ichi
authors.initials: K
authors.lastname: Okazaki
authors.affiliation: Department of Physics, Faculty of Science, Gakushuin University, Tokyo 171-8588, Japan;
authors.forename: Masaru
authors.initials: M
authors.lastname: Kobayashi
authors.affiliation: Department of Physics, Faculty of Science, Gakushuin University, Tokyo 171-8588, Japan;
authors.forename: Takashi
authors.initials: T
authors.lastname: Matsui
authors.affiliation: Department of Theoretical Biophysics, Max Planck Institute of Biophysics, 60438 Frankfurt am Main, Germany;
authors.forename: Gerhard
authors.initials: G
authors.lastname: Hummer
authors.affiliation: Department of Physics, Faculty of Science, Gakushuin University, Tokyo 171-8588, Japan; Department of Applied Biological Science, Tokyo University of Science, Chiba-ken 278-8510, Japan; Precursory Research for Embryonic Science and Technology, Japan Science and Technology Agency, Saitama 332-0012, Japan.
authors.forename: Tomoko
authors.initials: T
authors.lastname: Masaike
authors.affiliation: Department of Physics, Faculty of Science, Gakushuin University, Tokyo 171-8588, Japan; mitsuhiro.sugawa@bio.c.u-tokyo.ac.jp takayuki.nishizaka@gakushuin.ac.jp.
authors.forename: Takayuki
authors.initials: T
authors.lastname: Nishizaka
mesh_terms: D001407:Bacillus / Q000201:enzymology*; D001426:Bacterial Proteins / Q000737:chemistry*; D031541:Fluorescence Resonance Energy Transfer; D011487:Protein Conformation; D006180:Proton-Translocating ATPases / Q000737:chemistry*
chemical_list: D001426:Bacterial Proteins; D006180:Proton-Translocating ATPases
keywords: F1-ATPase; FRET; principal component analysis; single molecule