title: Unconstrained steps of myosin VI appear longest among known molecular motors.
abstract: 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.
authors.affiliation: Okazaki Institute for Integrative Bioscience, National Institutes of Natural Sciences, Higashiyama 5-1, Myodaiji, Okazaki 444-8787, Japan.
authors.forename: M Yusuf
authors.initials: MY
authors.lastname: Ali
authors.forename: Kazuaki
authors.initials: K
authors.lastname: Homma
authors.forename: Atsuko Hikikoshi
authors.initials: AH
authors.lastname: Iwane
authors.forename: Kengo
authors.initials: K
authors.lastname: Adachi
authors.forename: Hiroyasu
authors.initials: H
authors.lastname: Itoh
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Kinosita
authors.forename: Toshio
authors.initials: T
authors.lastname: Yanagida
authors.forename: Mitsuo
authors.initials: M
authors.lastname: Ikebe
mesh_terms: D000199:Actins / Q000378:metabolism*; D000818:Animals; D016547:Kinesins / Q000378:metabolism*; D020409:Molecular Motor Proteins / Q000378:metabolism*; D009068:Movement / Q000502:physiology*; D018995:Myosin Heavy Chains / Q000378:metabolism*; D024701:Myosin Type V / Q000378:metabolism; D011485:Protein Binding; D012399:Rotation
chemical_list: D000199:Actins; D020409:Molecular Motor Proteins; C089785:myosin VI; D024701:Myosin Type V; D018995:Myosin Heavy Chains; D016547:Kinesins