Dataset Information

Nonequilibrium fluctuations of lipid membranes by the rotating motor protein F₁F₀-ATP synthase.

ABSTRACT: ATP synthase is a rotating membrane protein that synthesizes ATP through proton-pumping activity across the membrane. To unveil the mechanical impact of this molecular active pump on the bending properties of its lipid environment, we have functionally reconstituted the ATP synthase in giant unilamellar vesicles and tracked the membrane fluctuations by means of flickering spectroscopy. We find that ATP synthase rotates at a frequency of about 20 Hz, promoting large nonequilibrium deformations at discrete hot spots in lipid vesicles and thus inducing an overall membrane softening. The enhanced nonequilibrium fluctuations are compatible with an accumulation of active proteins at highly curved membrane sites through a curvature-protein coupling mechanism that supports the emergence of collective effects of rotating ATP synthases in lipid membranes.

SUBMITTER: Almendro-Vedia VG

PROVIDER: S-EPMC5664490 | biostudies-literature | 2017 Oct

REPOSITORIES: biostudies-literature

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Nonequilibrium fluctuations of lipid membranes by the rotating motor protein F<sub>1</sub>F<sub>0</sub>-ATP synthase.

Almendro-Vedia Víctor G VG Natale Paolo P Mell Michael M Bonneau Stephanie S Monroy Francisco F Joubert Frederic F López-Montero Iván I

Proceedings of the National Academy of Sciences of the United States of America 20171009 43

ATP synthase is a rotating membrane protein that synthesizes ATP through proton-pumping activity across the membrane. To unveil the mechanical impact of this molecular active pump on the bending properties of its lipid environment, we have functionally reconstituted the ATP synthase in giant unilamellar vesicles and tracked the membrane fluctuations by means of flickering spectroscopy. We find that ATP synthase rotates at a frequency of about 20 Hz, promoting large nonequilibrium deformations at ...[more]

PMID: 29073046

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Project description:The F-ATP synthase, consisting of F1 and FO motors connected by a central rotor and the stators, is the enzyme responsible for synthesizing the majority of ATP in all organisms. The F1 (αβ)3 ring stator contains three catalytic sites. Single-molecule F1 rotation studies revealed that ATP hydrolysis at each catalytic site (0°) precedes a power-stroke that rotates subunit-γ 120° with angular velocities that vary with rotational position. Catalytic site conformations vary relative to subunit-γ position (βE, empty; βD, ADP bound; βT, ATP-bound). During a power stroke, βE binds ATP (0°-60°) and βD releases ADP (60°-120°). Årrhenius analysis of the power stroke revealed that elastic energy powers rotation via unwinding the γ-subunit coiled-coil. Energy from ATP binding at 34° closes βE upon subunit-γ to drive rotation to 120° and forcing the subunit-γ to exchange its tether from βE to βD, which changes catalytic site conformations. In F1FO, the membrane-bound FO complex contains a ring of c-subunits that is attached to subunit-γ. This c-ring rotates relative to the subunit-a stator in response to transmembrane proton flow driven by a pH gradient, which drives subunit-γ rotation in the opposite direction to force ATP synthesis in F1. Single-molecule studies of F1FO embedded in lipid bilayer nanodisks showed that the c-ring transiently stopped F1-ATPase-driven rotation every 36° (at each c-subunit in the c10-ring of E. coli F1FO) and was able to rotate 11° in the direction of ATP synthesis. Protonation and deprotonation of the conserved carboxyl group on each c-subunit is facilitated by separate groups of subunit-a residues, which were determined to have different pKa's. Mutations of any of any residue from either group changed both pKa values, which changed the occurrence of the 11° rotation proportionately. This supports a Grotthuss mechanism for proton translocation and indicates that proton translocation occurs during the 11° steps. This is consistent with a mechanism in which each 36° of rotation the c-ring during ATP synthesis involves a proton translocation-dependent 11° rotation of the c-ring, followed by a 25° rotation driven by electrostatic interaction of the negatively charged unprotonated carboxyl group to the positively charged essential arginine in subunit-a.

Dataset Information

Nonequilibrium fluctuations of lipid membranes by the rotating motor protein F₁F₀-ATP synthase.

Publications

Nonequilibrium fluctuations of lipid membranes by the rotating motor protein F<sub>1</sub>F<sub>0</sub>-ATP synthase.

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Dataset Information

Nonequilibrium fluctuations of lipid membranes by the rotating motor protein F1F0-ATP synthase.

Publications

Nonequilibrium fluctuations of lipid membranes by the rotating motor protein F<sub>1</sub>F<sub>0</sub>-ATP synthase.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

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Nonequilibrium fluctuations of lipid membranes by the rotating motor protein F₁F₀-ATP synthase.