title: Secretory vesicle transport velocity in living cells depends on the myosin-V lever arm length.
abstract: Myosins are molecular motors that exert force against actin filaments. One widely conserved myosin class, the myosin-Vs, recruits organelles to polarized sites in animal and fungal cells. However, it has been unclear whether myosin-Vs actively transport organelles, and whether the recently challenged lever arm model developed for muscle myosin applies to myosin-Vs. Here we demonstrate in living, intact yeast that secretory vesicles move rapidly toward their site of exocytosis. The maximal speed varies linearly over a wide range of lever arm lengths genetically engineered into the myosin-V heavy chain encoded by the MYO2 gene. Thus, secretory vesicle polarization is achieved through active transport by a myosin-V, and the motor mechanism is consistent with the lever arm model.
authors.affiliation: Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA.
authors.forename: Daniel H
authors.initials: DH
authors.lastname: Schott
authors.forename: Ruth N
authors.initials: RN
authors.lastname: Collins
authors.forename: Anthony
authors.initials: A
authors.lastname: Bretscher
mesh_terms: D000199:Actins / Q000378:metabolism; D001693:Biological Transport, Active; D015153:Blotting, Western; D005089:Exocytosis; D006056:Golgi Apparatus / Q000378:metabolism; D008856:Microscopy, Fluorescence; D016253:Microscopy, Immunoelectron; D008954:Models, Biological; D009154:Mutation / Q000235:genetics; D018995:Myosin Heavy Chains / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D024701:Myosin Type V / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D020449:Repetitive Sequences, Amino Acid; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D022142:Secretory Vesicles / Q000378:metabolism* / Q000648:ultrastructure; D013696:Temperature; D013997:Time Factors
chemical_list: D000199:Actins; C077512:MYO2 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D024701:Myosin Type V; D018995:Myosin Heavy Chains