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Visualization of ATP Synthase Dimers in Mitochondria by Electron Cryo-tomography
Published on: September 14, 2014
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Structural Asymmetry and Kinetic Limping of Single Rotary F-ATP Synthases
Hendrik Sielaff1, Seiga Yanagisawa2, Wayne D Frasch3
1Single-Molecule Microscopy Group, Jena University Hospital, Friedrich Schiller University, 07743 Jena, Germany. hendrik.sielaff@med.uni-jena.de.
Molecules (Basel, Switzerland)
|February 2, 2019
Summary
F-ATP synthases, crucial for ATP production, exhibit slight rotational asymmetry. This structural asymmetry causes one step in their rotary progression to be longer than others, a subtle effect due to internal elastic coupling.
Area of Science:
- Biochemistry and Molecular Biology
- Enzyme kinetics
- Bioenergetics
Background:
- F-ATP synthases are molecular machines that convert proton flow into ATP synthesis.
- The Escherichia coli enzyme comprises a membrane-embedded FO domain and a soluble F₁ domain, with distinct rotor and stator subunits.
- Structural asymmetry arises from the stator stalk, breaking the enzyme's overall rotational symmetry.
Purpose of the Study:
- To investigate the functional consequences of structural asymmetry in F-ATP synthase.
- To precisely measure the rotary progression during ATP hydrolysis at the single-molecule level.
- To quantify the impact of broken symmetry on enzyme kinetics.
Main Methods:
- Employed three single-molecule techniques: fluorescence video-microscopy with actin filaments, Förster resonance energy transfer (FRET), and a gold nanorod polarization assay.
- Monitored the enzyme's rotary motion during ATP hydrolysis.
- Analyzed the dwell times at different steps of the rotary cycle.
Main Results:
- Observed a three-stepped rotary progression during ATP hydrolysis.
- One dwell time in the rotary cycle was significantly longer (up to 1.6 times) than the other two.
- The effect of structural asymmetry on dwell times was modest, attributed to internal elastic coupling.
Conclusions:
- The structural asymmetry in F-ATP synthase leads to a measurable kinetic heterogeneity in its rotary cycle.
- Internal elastic coupling within the enzyme mitigates the impact of asymmetry on rotational progression.
- Provides insights into the precise mechanical coupling and energy transduction mechanisms in F-ATP synthases.
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