Graduate School of Frontier Biosciences, Osaka University


Entropy rectifies the Brownian steps of kinesin.

Journal Nat Chem Biol 1, 346-351 (2005)
Authors Taniguchi, Y., Nishiyama, M., Ishii, Y. and Yanagida, T.
Title Entropy rectifies the Brownian steps of kinesin.
PubMed 16408074
Abstract Kinesin is a stepping motor that successively produces forward and backward 8-nm steps along microtubules. Under physiological conditions, the steps powering kinesin's motility are biased in one direction and drive various biological motile processes. The physical mechanism underlying the unidirectional bias of the kinesin steps is not fully understood. Here we explored the mechanical kinetics and thermodynamics of forward and backward kinesin steps by analyzing their temperature and load dependence. Results show that the frequency asymmetry between forward and backward steps is produced by entropy. Furthermore, the magnitude of the entropic asymmetry is 6 k(B)T, more than three times greater than expected from a current model, in which a mechanical conformational change within the kinesin molecular structure directly biases the kinesin steps forward. We propose that the stepping direction of kinesin is preferably caused by an entropy asymmetry resulting from the compatibility between the kinesin and microtubule interaction based on their polar structures.
Heat or thermal noise causes a serious problem to make some artificial machines smaller to nanometer level. We found a mechanism where a nanometer-sized motor protein, kinesin, uses the thermal noise to move, contrary to well-known machines. It is expected that the application of proteins to nano-technology may enable us to create new nano-machines that function even if surrounded by the thermal noise.