title: Torque generation and utilization in motor enzyme F0F1-ATP synthase: half-torque F1 with short-sized pushrod helix and reduced ATP Synthesis by half-torque F0F1.
abstract: ATP synthase (F(0)F(1)) is made of two motors, a proton-driven motor (F(0)) and an ATP-driven motor (F(1)), connected by a common rotary shaft, and catalyzes proton flow-driven ATP synthesis and ATP-driven proton pumping. In F(1), the central γ subunit rotates inside the α(3)β(3) ring. Here we report structural features of F(1) responsible for torque generation and the catalytic ability of the low-torque F(0)F(1). (i) Deletion of one or two turns in the α-helix in the C-terminal domain of catalytic β subunit at the rotor/stator contact region generates mutant F(1)s, termed F(1)(1/2)s, that rotate with about half of the normal torque. This helix would support the helix-loop-helix structure acting as a solid "pushrod" to push the rotor γ subunit, but the short helix in F(1)(1/2)s would fail to accomplish this task. (ii) Three different half-torque F(0)F(1)(1/2)s were purified and reconstituted into proteoliposomes. They carry out ATP-driven proton pumping and build up the same small transmembrane ΔpH, indicating that the final ΔpH is directly related to the amount of torque. (iii) The half-torque F(0)F(1)(1/2)s can catalyze ATP synthesis, although slowly. The rate of synthesis varies widely among the three F(0)F(1)(1/2)s, which suggests that the rate reflects subtle conformational variations of individual mutants.
authors: Chemical Resources Laboratory, Tokyo Institute of Technology, Nagatsuta 4259, Yokohama 226-8503.
authors: Eiji
authors: E
authors: Usukura
authors: Toshiharu
authors: T
authors: Suzuki
authors: Shou
authors: S
authors: Furuike
authors: Naoki
authors: N
authors: Soga
authors: Ei-Ichiro
authors: E
authors: Saita
authors: Toru
authors: T
authors: Hisabori
authors: Kazuhiko
authors: K
authors: Kinosita
authors: Masasuke
authors: M
authors: Yoshida
mesh_terms: D000255:Adenosine Triphosphate / Q000096:biosynthesis*; D002384:Catalysis; D020134:Catalytic Domain; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D018257:Helix-Loop-Helix Motifs; D009154:Mutation; D017434:Protein Structure, Tertiary; D018892:Proton-Motive Force / Q000502:physiology*; D006180:Proton-Translocating ATPases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
chemical_list: D029968:Escherichia coli Proteins; D000255:Adenosine Triphosphate; D006180:Proton-Translocating ATPases