Kinesin hydrolyses one ATP per 8-nm step

Area of Science:

• Biochemistry
• Molecular Biology
• Cellular Biophysics

Background:

• Kinesin is an ATP-dependent motor protein that moves along microtubules.
• Understanding the mechanochemical coupling (ATP consumption per step) is crucial for kinesin function.
• Previous studies on similar motor proteins like actomyosin have faced experimental challenges and controversy.

Purpose of the Study:

• To determine the precise number of ATP molecules hydrolyzed per step for kinesin.
• To elucidate the mechanochemical coupling ratio of kinesin without direct ATPase activity measurements.
• To constrain theoretical models of kinesin's molecular motor mechanism.

Main Methods:

• Utilized single kinesin molecules attached to beads, moving on microtubules.
• Employed high-resolution interferometry for precise tracking of bead movement.
• Analyzed step intervals at limiting ATP concentrations and motor speed fluctuations versus ATP concentration.

Main Results:

• Kinesin molecules hydrolyze a single ATP molecule for each 8-nm step taken.
• This 1:1 ATP-to-step ratio was observed at near-zero load conditions.
• The findings exclude complex one-to-many or many-to-one ATP hydrolysis schemes.

Conclusions:

• Kinesin operates with a strict one ATP per 8 nm step coupling ratio.
• This finding simplifies models of kinesin's energy transduction mechanism.
• The results provide critical data for understanding molecular motor function and dynamics.