Vectorial loading of processive motor proteins: implementing a landscape picture.

Area of Science:

• Biophysics
• Molecular Biology
• Cellular Mechanics

Background:

• Molecular motors like kinesin move along tracks, transporting cellular components.
• Understanding motor mechanics requires analyzing their response to forces and fuel (ATP).
• Previous models simplified force interactions, limiting comprehensive analysis.

Purpose of the Study:

• To develop a mechanochemical model incorporating the full vectorial nature of forces on molecular motors.
• To analyze kinesin motor behavior under diverse load conditions (parallel, perpendicular, assisting).
• To explain experimental observations, such as microtubule buckling induced by kinesin.

Main Methods:

• Extended existing mechanochemical kinetic models.
• Implemented a free-energy landscape approach to account for vectorial forces.
• Introduced load distribution vectors and compliance matrices to describe force-dependent transition rates.
• Applied the model to analyze specific experimental data on kinesin-induced microtubule buckling.

Main Results:

• The model successfully incorporates vectorial forces (F(x), F(y), F(z)) acting on molecular motors.
• Analysis suggests kinesin motors may adopt a 'crouched' state upon ATP binding.
• Derived an expression for motor velocity dependent on forces and ATP concentration, V(F(x), F(z); [ATP]).

Conclusions:

• The developed model provides a more accurate framework for understanding molecular motor mechanics under complex force loads.
• The 'crouching' mechanism offers a potential explanation for kinesin's behavior in specific experimental setups.
• The derived velocity expression is crucial for interpreting experiments like microtubule buckling.