Fluctuation analysis of mechanochemical coupling depending on the type of bio-molecular motor

TL;DR

This study compares the mechanochemical coupling mechanisms of myosin V and myosin II, revealing tight coupling in myosin V for cargo transport and loose coupling in myosin II for force generation, with implications for their physiological roles.

Contribution

It provides a detailed analysis of how different bio-molecular motors utilize mechanochemical coupling, highlighting the distinct mechanisms underlying their functions.

Findings

Myosin V exhibits tight mechanochemical coupling with Michaelis-Menten kinetics.

Myosin II shows loose coupling with variable step sizes depending on ATP concentration.

Myosin II can generate larger steps (~200 nm) per ATP hydrolysis through cooperative action.

Abstract

Mechanochemical coupling was studied for two different types of myosin motors in cells: myosin V, which carries cargo over long distances by as a single molecule; and myosin II, which generates a contracting force in cooperation with other myosin II molecules. Both mean and variance of myosin V velocity at various [ATP] obeyed Michaelis-Menten mechanics, consistent with tight mechanochemical coupling. Myosin II, working in an ensemble, however, was explained by a loose coupling mechanism, generating variable step sizes depending on the ATP concentration and realizing a much larger step (200 nm) per ATP hydrolysis than myosin V through its cooperative nature at zero load. These different mechanics are ideal for the respective myosin's physiological functions.