This Article Full Text Full Text (PDF) Supplemental Material Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Ali, M. Y. Articles by Ikebe, M. Search for Related Content PubMed PubMed Citation Articles by Ali, M. Y. Articles by Ikebe, M.

Unconstrained Steps of Myosin VI Appear Longest among Known Molecular Motors

M. Yusuf Ali ^* , Kazuaki Homma , Atsuko Hikikoshi Iwane , Kengo Adachi ^*, Hiroyasu Itoh ^¶ ||, Kazuhiko Kinosita, Jr. ^*, Toshio Yanagida  and Mitsuo Ikebe 

^* Okazaki Institute for Integrative Bioscience, National Institutes of Natural Sciences, Higashiyama 5-1, Myodaiji, Okazaki 444-8787, Japan; Department of Physics, Faculty of Physical Sciences, Shahjalal University of Science and Technology, Sylhet-3114, Bangladesh; Department of Physiology, University of Massachusetts Medical School, Worcester, Massachusetts 01655-0127, USA; Department of Physiology and Biosignaling, Graduate School of Medicine, Osaka University, Yamadaoka 2-2, Suita 565-0871, Japan; ^¶ Tsukuba Research Laboratory, Hamamatsu Photonics KK, Tokodai, Tsukuba 300-2635, Japan; and ^|| Core Research for Evolutional Science and Technology "Creation and Application of Soft Nano-Machine, the Hyperfunctional Molecular Machine" Team 13^*, Tokodai, Tsukuba 300-2635, Japan

Correspondence: Address reprint requests to Kazuhiko Kinosita Jr., Okazaki Institute for Integrative Bioscience, National Institutes of Natural Sciences, Higashiyama 5-1, Myodaiji, Okazaki 444-8787, Japan. Tel.: 81-564-59-5230; Fax: 81-59-564-5234; E-mail: kazuhiko{at}ims.ac.jp.

Myosin VI is a two-headed molecular motor that moves along an actin filament in the direction opposite to most other myosins. Previously, a single myosin VI molecule has been shown to proceed with steps that are large compared to its neck size: either it walks by somehow extending its neck or one head slides along actin for a long distance before the other head lands. To inquire into these and other possible mechanism of motility, we suspended an actin filament between two plastic beads, and let a single myosin VI molecule carrying a bead duplex move along the actin. This configuration, unlike previous studies, allows unconstrained rotation of myosin VI around the right-handed double helix of actin. Myosin VI moved almost straight or as a right-handed spiral with a pitch of several micrometers, indicating that the molecule walks with strides slightly longer than the actin helical repeat of 36 nm. The large steps without much rotation suggest kinesin-type walking with extended and flexible necks, but how to move forward with flexible necks, even under a backward load, is not clear. As an answer, we propose that a conformational change in the lifted head would facilitate landing on a forward, rather than backward, site. This mechanism may underlie stepping of all two-headed molecular motors including kinesin and myosin V.

This article has been cited by other articles:

				G. Lan and S. X. Sun Flexible Light-Chain and Helical Structure of F-Actin Explain the Movement and Step Size of Myosin-VI Biophys. J., December 1, 2006; 91(11): 4002 - 4013. [Abstract] [Full Text] [PDF]

				T. M. Watanabe, H. Tanaka, A. H. Iwane, S. Maki-Yonekura, K. Homma, A. Inoue, R. Ikebe, T. Yanagida, and M. Ikebe A one-headed class V myosin molecule develops multiple large ({approx}32-nm) steps successively PNAS, June 29, 2004; 101(26): 9630 - 9635. [Abstract] [Full Text] [PDF]