Structural basis of redox modulation on chloroplast ATP synthase
Jay-How Yang1, Dewight Williams2, Eaazhisai Kandiah3
1Center for Applied Structural Discovery (CASD), Biodesign Institute, Arizona State University, Tempe, AZ, USA.
Communications Biology
|September 4, 2020
Summary
Chloroplast ATP synthase activity is regulated by a redox switch on its gamma subunit. This switch stabilizes the enzyme in its oxidized state and facilitates ATP synthesis when reduced, revealing key energy regulation mechanisms.
Area of Science:
- Biochemistry
- Structural Biology
- Plant Physiology
Background:
- Chloroplast ATP synthase regulates energy production in plants.
- A unique redox switch on the gamma subunit modulates enzyme activity, particularly limiting ATP hydrolysis at night.
- Understanding the molecular basis of this redox modulation is crucial for plant energy regulation.
Purpose of the Study:
- To elucidate the molecular mechanisms of redox modulation in spinach chloroplast ATP synthase.
- To determine the high-resolution structures of the enzyme in both reduced and oxidized states.
- To provide mechanistic insights into how redox state affects enzyme activity and energy regulation.
Main Methods:
- Single-particle cryo-electron microscopy (cryo-EM) was employed to visualize the enzyme.
- Structures were determined for both reduced and oxidized states of chloroplast ATP synthase.
- An uncompetitive inhibitor, tentoxin, was used to stabilize the reduced enzyme for high-resolution imaging.
Main Results:
- The oxidized gamma subunit, stabilized by a disulfide linkage, introduces a torsional constraint.
- Reduction of the gamma subunit releases this constraint, allowing for enzyme complex motion and smoother transitions between rotary states.
- High-resolution cryo-EM structures revealed the structural basis for redox-dependent modulation of enzyme activity.
Conclusions:
- The study provides detailed structural insights into the redox switch mechanism of chloroplast ATP synthase.
- This mechanism is critical for regulating ATP synthesis and hydrolysis, optimizing energy management in plants.
- The findings enhance our understanding of energy regulation at the molecular level in chloroplasts.
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