Elastic coupling power stroke mechanism of the F1-ATPase molecular motor

James L. Martin, Robert Ishmukhametov, David Spetzler, Tassilo Hornung, Wayne Frasch

Research output: Contribution to journalArticle

15 Scopus citations

Abstract

The angular velocity profile of the 120° F1-ATPase power stroke was resolved as a function of temperature from 16.3 to 44.6 °C using a ΔμATP = −31.25 kBT at a time resolution of 10 μs. Angular velocities during the first 60° of the power stroke (phase 1) varied inversely with temperature, resulting in negative activation energies with a parabolic dependence. This is direct evidence that phase 1 rotation derives from elastic energy (spring constant, κ = 50 kBT·rad−2). Phase 2 of the power stroke had an enthalpic component indicating that additional energy input occurred to enable the γ-subunit to overcome energy stored by the spring after rotating beyond its 34° equilibrium position. The correlation between the probability distribution of ATP binding to the empty catalytic site and the negative Ea values of the power stroke during phase 1 suggests that this additional energy is derived from the binding of ATP to the empty catalytic site. A second torsion spring (κ = 150 kBT·rad−2; equilibrium position, 90°) was also evident that mitigated the enthalpic cost of phase 2 rotation. The maximum ΔGǂ was 22.6 kBT, and maximum efficiency was 72%. An elastic coupling mechanism is proposed that uses the coiled-coil domain of the γ-subunit rotor as a torsion spring during phase 1, and then as a crankshaft driven by ATP-binding–dependent conformational changes during phase 2 to drive the power stroke.

Original languageEnglish (US)
Pages (from-to)5750-5755
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume115
Issue number22
DOIs
StatePublished - May 29 2018

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Keywords

  • F-type ATP synthase
  • F1-ATPase
  • FOF1 ATP synthase
  • Power stroke mechanism
  • Single molecule

ASJC Scopus subject areas

  • General

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