title: Myo4p is a monomeric myosin with motility uniquely adapted to transport mRNA.
abstract: The yeast Saccharomyces cerevisiae uses two class V myosins to transport cellular material into the bud: Myo2p moves secretory vesicles and organelles, whereas Myo4p transports mRNA. To understand how Myo2p and Myo4p are adapted to transport physically distinct cargos, we characterize Myo2p and Myo4p in yeast extracts, purify active Myo2p and Myo4p from yeast lysates, and analyze their motility. We find several striking differences between Myo2p and Myo4p. First, Myo2p forms a dimer, whereas Myo4p is a monomer. Second, Myo4p generates higher actin filament velocity at lower motor density. Third, single molecules of Myo2p are weakly processive, whereas individual Myo4p motors are nonprocessive. Finally, Myo4p self-assembles into multi-motor complexes capable of processive motility. We show that the unique motility of Myo4p is not due to its motor domain and that the motor domain of Myo2p can transport ASH1 mRNA in vivo. Our results suggest that the oligomeric state of Myo4p is important for its motility and ability to transport mRNA.
authors: Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06520, USA.
authors: Brian D
authors: BD
authors: Dunn
authors: Takeshi
authors: T
authors: Sakamoto
authors: Myoung-Soon S
authors: MS
authors: Hong
authors: James R
authors: JR
authors: Sellers
authors: Peter A
authors: PA
authors: Takizawa
mesh_terms: D003432:Cross-Linking Reagents / Q000494:pharmacology; D005022:Ethyldimethylaminopropyl Carbodiimide / Q000494:pharmacology; D049452:Green Fluorescent Proteins / Q000378:metabolism; D008854:Microscopy, Electron; D020409:Molecular Motor Proteins / Q000378:metabolism; D018995:Myosin Heavy Chains / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism* / Q000648:ultrastructure; D024701:Myosin Type V / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism* / Q000648:ultrastructure; D009218:Myosins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism* / Q000648:ultrastructure; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D021381:Protein Transport / Q000187:drug effects; D034443:RNA Transport / Q000187:drug effects; D012333:RNA, Messenger / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism* / Q000648:ultrastructure
chemical_list: D003432:Cross-Linking Reagents; C077512:MYO2 protein, S cerevisiae; D020409:Molecular Motor Proteins; C098732:Myo4 protein, S cerevisiae; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins; D049452:Green Fluorescent Proteins; D024701:Myosin Type V; D018995:Myosin Heavy Chains; D009218:Myosins; D005022:Ethyldimethylaminopropyl Carbodiimide