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The catalytic transition state in ATP synthase
A E Senior1, J Weber, S Nadanaciva
1Department of Biochemistry and Biophysics, Box 712, University of Rochester Medical Center, Rochester, New York 14642, USA. alan_senior@urmc.rochester.edu
Journal of Bioenergetics and Biomembranes
|July 16, 2004
Summary
Researchers modeled the ATP synthase transition state using analogs and fluorescence probes. Mobility of an "arginine finger" residue explains rate acceleration via positive cooperativity.
Area of Science:
- Biochemistry
- Enzyme kinetics
- Molecular biology
Background:
- ATP synthase is crucial for cellular energy production.
- Understanding its catalytic mechanism, particularly the transition state, is key to elucidating energy transduction.
- Previous models lacked detailed characterization of the transition state structure and dynamics.
Purpose of the Study:
- To characterize and model the catalytic transition state of ATP synthase.
- To identify key residues and interactions stabilizing the transition state.
- To explain the mechanism of rate acceleration through catalytic site cooperativity.
Main Methods:
- Utilized transition-state analogs (e.g., Mg-ADP-fluoroaluminate) to mimic the transition state.
- Employed fluorescence spectroscopy with beta-Trp331 and beta-Trp148 as probes.
- Introduced mutations in critical catalytic residues to assess stabilization requirements.
Main Results:
- Successfully characterized the ATP synthase transition state using combined analog and fluorescence approaches.
- Identified alpha-Arg376 as a mobile "arginine finger" residue critical for transition state stabilization.
- Demonstrated that this residue interacts specifically with nucleotides at the transition state, not ground states.
Conclusions:
- The mobility of the alpha-Arg376 "arginine finger" explains rate acceleration via positive catalytic site cooperativity.
- Transition state formation and collapse likely induce conformational changes linked to enzyme rotation.
- This study provides a refined model of ATP synthase catalysis at the transition state.