Universal Aspects of the Chemomechanical Coupling for Molecular Motors

The directed movement of molecular motors is studied theoretically within a general class of nonuniform ratchet models in which the motor can attain $M$ internal states and undergo transitions between these states at $K$ spatial locations. The functional relationship between the motor velocity and the concentration of the fuel molecule is analyzed for arbitrary values of $M$ and $K$. This relationship is found to exhibit universal features which depend on the number of unbalanced transitions per motor cycle arising from the enzymatic motor activity. This agrees with experimental results on dimeric kinesin and is predicted to apply to other cytoskeletal motors.