Article abstract
Nature Chemical Biology 1, 342 - 347 (2005)
Published online: 9 October 2005 | doi:10.1038/nchembio741
Entropy rectifies the Brownian steps of kinesin
Yuichi Taniguchi1,2, Masayoshi Nishiyama3, Yoshiharu Ishii1 & Toshio Yanagida1,4,5
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 kBT, 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.
- Soft Nanomachine Project, Japan Science and Technology Agency, 1-3, Yamadaoka, Suita, Osaka, 565-0871, Japan.
- Department of Mechanical Science and Bioengineering, Graduate School of Engineering Science, Osaka University, 1-3, Machikaneyama, Toyonaka, Osaka 560-8531, Japan.
- Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto, 606-8502, Japan.
- Laboratories for Nanobiology, Graduate School of Frontier Biosciences, Osaka University, 1-3, Yamadaoka.
- Department of Physiology and Biosignaling, Graduate School of Medicine, Osaka University, 2-2, Yamadaoka, Suita, Osaka, 565-0871, Japan.
Correspondence to: Toshio Yanagida1,4,5 e-mail: yanagida@phys1.med.osaka-u.ac.jp
