title: Two single-headed myosin V motors bound to a tetrameric adapter protein form a processive complex.
abstract: Myo4p, one of two class V myosins in budding yeast, continuously transports messenger RNA (mRNA) cargo in the cell but is nonprocessive when characterized in vitro. The adapter protein She3p tightly binds to the Myo4p rod, forming a single-headed motor complex. In this paper, we show that two Myo4p-She3p motors are recruited by the tetrameric mRNA-binding protein She2p to form a processive double-headed complex. The binding site for She3p was mapped to a single α helix that protrudes at right angles from She2p. Processive runs of several micrometers on yeast actin-tropomyosin filaments were observed only in the presence of She2p, and, thus, motor activity is regulated by cargo binding. While moving processively, each head steps ~72 nm in a hand-over-hand motion. Coupling two high-duty cycle monomeric motors via a common cargo-binding adapter protein creates a complex with transport properties comparable with a single dimeric processive motor such as vertebrate myosin Va.
authors.affiliation: Department of Molecular Physiology and Biophysics, University of Vermont, Burlington, VT 05405, USA.
authors.forename: Elena B
authors.initials: EB
authors.lastname: Krementsova
authors.forename: Alex R
authors.initials: AR
authors.lastname: Hodges
authors.forename: Carol S
authors.initials: CS
authors.lastname: Bookwalter
authors.forename: Thomas E
authors.initials: TE
authors.lastname: Sladewski
authors.forename: Mirko
authors.initials: M
authors.lastname: Travaglia
authors.forename: H Lee
authors.initials: HL
authors.lastname: Sweeney
authors.forename: Kathleen M
authors.initials: KM
authors.lastname: Trybus
mesh_terms: D008958:Models, Molecular; D018995:Myosin Heavy Chains / Q000737:chemistry / Q000378:metabolism*; D024701:Myosin Type V / Q000737:chemistry / Q000378:metabolism*; D011487:Protein Conformation; D012333:RNA, Messenger / Q000737:chemistry / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000378:metabolism*
chemical_list: C098732:Myo4 protein, S cerevisiae; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; C471175:SHE2 protein, S cerevisiae; C471176:SHE3 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D024701:Myosin Type V; D018995:Myosin Heavy Chains
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