Nucleotide Exchange Mechanism Involving Angle-Dependent Rate Constants Extracted from F1-ATPase Single-Molecule...

Area of Science:

• Biochemistry and Molecular Biology
• Enzyme kinetics
• Biophysical chemistry

Background:

• F1-ATPase is a rotary motor enzyme crucial for cellular energy production.
• Previous studies suggested a million-fold acceleration in ADP release due to concerted ATP binding and ADP release.
• Understanding the kinetics of nucleotide exchange is vital for elucidating F1-ATPase function.

Purpose of the Study:

• To investigate the relationship between concerted nucleotide exchange and experimental data for F1-ATPase.
• To develop a theoretical framework explaining the observed kinetics of F1-ATPase.
• To uncover the underlying mechanisms driving the accelerated ADP release.

Main Methods:

• Developed a theory of reaction kinetics to model F1-ATPase rotational cycles.
• Extracted angle-dependent rate constants for nucleotide binding and release from single-molecule data.
• Integrated these rate constants into a unified kinetic scheme to derive analytical equations for nucleotide occupancy.

Main Results:

• The developed kinetic scheme accurately predicts nucleotide occupancy across a wide range of ATP concentrations.
• Identified correlated conformational changes in the F1-ATPase ring as the basis for the concerted mechanism.
• Demonstrated that the kinetic signature of this mechanism is an angle-dependent function of rate constants, independent of ATP concentration.

Conclusions:

• The concerted nucleotide exchange mechanism in F1-ATPase is driven by coordinated conformational dynamics.
• This mechanism provides a unified explanation for accelerated ADP release observed in various experimental settings.
• The findings offer novel insights into the intricate rotary mechanism of F1-ATPase.