title: A single-headed fission yeast myosin V transports actin in a tropomyosin-dependent manner.
abstract: Myo51, a class V myosin in fission yeast, localizes to and assists in the assembly of the contractile ring, a conserved eukaryotic actomyosin structure that facilitates cytokinesis. Rng8 and Rng9 are binding partners that dictate the cellular localization and function of Myo51. Myo51 was expressed in insect cells in the presence or absence of Rng8/9. Surprisingly, electron microscopy of negatively stained images and hydrodynamic measurements showed that Myo51 is single headed, unlike most class V myosins. When Myo51-Rng8/9 was bound to actin-tropomyosin, two attachment sites were observed: the typical ATP-dependent motor domain attachment and a novel ATP-independent binding of the tail mediated by Rng8/9. A modified motility assay showed that this additional binding site anchors Myo51-Rng8/9 so that it can cross-link and slide actin-tropomyosin filaments relative to one another, functions that may explain the role of this motor in contractile ring assembly.
authors.affiliation: Department of Molecular Physiology and Biophysics, University of Vermont, Burlington, VT 05405.
authors.forename: Qing
authors.initials: Q
authors.lastname: Tang
authors.affiliation: Laboratory of Molecular Physiology, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892.
authors.forename: Neil
authors.identifier: 0000-0003-2306-0228
authors.initials: N
authors.lastname: Billington
authors.affiliation: Department of Molecular Physiology and Biophysics, University of Vermont, Burlington, VT 05405.
authors.forename: Elena B
authors.initials: EB
authors.lastname: Krementsova
authors.affiliation: Department of Molecular Physiology and Biophysics, University of Vermont, Burlington, VT 05405.
authors.forename: Carol S
authors.initials: CS
authors.lastname: Bookwalter
authors.affiliation: Department of Molecular Physiology and Biophysics, University of Vermont, Burlington, VT 05405.
authors.forename: Matthew
authors.initials: M
authors.lastname: Lord
authors.affiliation: Department of Molecular Physiology and Biophysics, University of Vermont, Burlington, VT 05405 kathleen.trybus@uvm.edu.
authors.forename: Kathleen M
authors.identifier: 0000-0002-5583-8500
authors.initials: KM
authors.lastname: Trybus
mesh_terms: D000199:Actins / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism; D001665:Binding Sites; D055767:Immobilized Proteins / Q000378:metabolism; D008856:Microscopy, Fluorescence; D008954:Models, Biological; D009218:Myosins / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D016624:Negative Staining; D011485:Protein Binding; D000072417:Protein Domains; D021381:Protein Transport; D012568:Schizosaccharomyces / Q000378:metabolism*; D029702:Schizosaccharomyces pombe Proteins / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D000072760:Single Molecule Imaging; D014335:Tropomyosin / Q000378:metabolism*; D014461:Ultracentrifugation
chemical_list: D000199:Actins; D055767:Immobilized Proteins; D029702:Schizosaccharomyces pombe Proteins; D014335:Tropomyosin; D000255:Adenosine Triphosphate; C554096:Myo51 protein, S pombe; D009218:Myosins