title: Domain compliance and elastic power transmission in rotary F(O)F(1)-ATPase.
abstract: The 2 nanomotors of rotary ATP synthase, ionmotive F(O) and chemically active F(1), are mechanically coupled by a central rotor and an eccentric bearing. Both motors rotate, with 3 steps in F(1) and 10-15 in F(O). Simulation by statistical mechanics has revealed that an elastic power transmission is required for a high rate of coupled turnover. Here, we investigate the distribution in the F(O)F(1) structure of compliant and stiff domains. The compliance of certain domains was restricted by engineered disulfide bridges between rotor and stator, and the torsional stiffness (kappa) of unrestricted domains was determined by analyzing their thermal rotary fluctuations. A fluorescent magnetic bead was attached to single molecules of F(1) and a fluorescent actin filament to F(O)F(1), respectively. They served to probe first the functional rotation and, after formation of the given disulfide bridge, the stochastic rotational motion. Most parts of the enzyme, in particular the central shaft in F(1), and the long eccentric bearing were rather stiff (torsional stiffness kappa > 750 pNnm). One domain of the rotor, namely where the globular portions of subunits gamma and epsilon of F(1) contact the c-ring of F(O), was more compliant (kappa congruent with 68 pNnm). This elastic buffer smoothes the cooperation of the 2 stepping motors. It is located were needed, between the 2 sites where the power strokes in F(O) and F(1) are generated and consumed.
authors.affiliation: Department of Biophysics, University of Osnabrück, 49069 Osnabrück, Germany.
authors.forename: Hendrik
authors.initials: H
authors.lastname: Sielaff
authors.forename: Henning
authors.initials: H
authors.lastname: Rennekamp
authors.forename: André
authors.initials: A
authors.lastname: Wächter
authors.forename: Hao
authors.initials: H
authors.lastname: Xie
authors.forename: Florian
authors.initials: F
authors.lastname: Hilbers
authors.forename: Katrin
authors.initials: K
authors.lastname: Feldbauer
authors.forename: Stanley D
authors.initials: SD
authors.lastname: Dunn
authors.forename: Siegfried
authors.initials: S
authors.lastname: Engelbrecht
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Junge
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism; D003187:Compliance; D004789:Enzyme Activation; D004800:Enzymes, Immobilized / Q000737:chemistry / Q000378:metabolism; D004926:Escherichia coli / Q000201:enzymology*; D020035:Holoenzymes / Q000737:chemistry / Q000378:metabolism; D006868:Hydrolysis; D008280:Magnetics; D008863:Microspheres; D025261:Mitochondrial Proton-Translocating ATPases / Q000737:chemistry* / Q000378:metabolism*; D008958:Models, Molecular; D010084:Oxidation-Reduction; D017434:Protein Structure, Tertiary; D045663:Quantum Dots; D012399:Rotation
chemical_list: D004800:Enzymes, Immobilized; D020035:Holoenzymes; D025261:Mitochondrial Proton-Translocating ATPases