Science 25 May 2007:
Vol. 316. no. 5828, pp. 1208 - 1212
DOI: 10.1126/science.1140468

Reports

Myosin V Walks by Lever Action and Brownian Motion

Katsuyuki Shiroguchi and Kazuhiko Kinosita, Jr.*

Myosin V is a molecular motor that moves cargo along actin filaments. Its two heads, each attached to a long and relatively stiff neck, move alternately forward in a "hand-over-hand" fashion. To observe under a microscope how the necks move, we attached a micrometer-sized rod to one of the necks. The leading neck swings unidirectionally forward, whereas the trailing neck, once lifted, undergoes extensive Brownian rotation in all directions before landing on a site ahead of the leading head. The neck-neck joint is essentially free, and the neck motion supports a mechanism where the active swing of the leading neck biases the random motion of the lifted head to let it eventually land on a forward site.

Department of Physics, Faculty of Science and Engineering, Waseda University, Okubo 3-4-1, Shinjuku-ku, Tokyo 169-8555, Japan.


* To whom correspondence should be addressed. E-mail: kazuhiko[at]waseda.jp