title: A unique mechanism for the processive movement of single-headed myosin-IX.
abstract: It has been puzzled that in spite of its single-headed structure, myosin-IX shows the typical character of processive motor in multi-molecule in vitro motility assay, because this cannot be explained by hand-over-hand mechanism of the two-headed processive myosins. Here, we show direct evidence of the processive movement of myosin-IX using two different single molecule techniques. Using optical trap nanometry, we found that myosin-IX takes several large ( approximately 20nm) steps before detaching from an actin filament. Furthermore, we directly visualized the single myosin-IX molecules moving on actin filaments for several hundred nanometers without dissociating from actin filament. Since myosin-IX processively moves without anchoring the neck domain, the result suggests that the neck tilting is not involved for the processive movement of myosin-IX. We propose that the myosin-IX head moves processively along an actin filament like an inchworm via a unique long and positively charged insertion in the loop 2 region of the head.
authors.affiliation: Department of Biophysical Engineering, Osaka University 1-3, Machikaneyama, Toyonaka, Osaka 560-8531, Japan.
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Nishikawa
authors.forename: So
authors.initials: S
authors.lastname: Nishikawa
authors.forename: Akira
authors.initials: A
authors.lastname: Inoue
authors.forename: Atsuko Hikikoshi
authors.initials: AH
authors.lastname: Iwane
authors.forename: Toshio
authors.initials: T
authors.lastname: Yanagida
authors.forename: Mitsuo
authors.initials: M
authors.lastname: Ikebe
mesh_terms: D008841:Actin Cytoskeleton / Q000737:chemistry; D000244:Adenosine Diphosphate / Q000737:chemistry; D000818:Animals; D006801:Humans; D008856:Microscopy, Fluorescence; D008954:Models, Biological; D020409:Molecular Motor Proteins / Q000737:chemistry*; D009218:Myosins / Q000737:chemistry*; D011487:Protein Conformation; D011817:Rabbits; D011994:Recombinant Proteins / Q000737:chemistry
chemical_list: D020409:Molecular Motor Proteins; D011994:Recombinant Proteins; C113469:myosin IXB; D000244:Adenosine Diphosphate; D009218:Myosins