title: Myosin VI must dimerize and deploy its unusual lever arm in order to perform its cellular roles.
abstract: It is unclear whether the reverse-direction myosin (myosin VI) functions as a monomer or dimer in cells and how it generates large movements on actin. We deleted a stable, single-α-helix (SAH) domain that has been proposed to function as part of a lever arm to amplify movements without impact on in vitro movement or in vivo functions. A myosin VI construct that used this SAH domain as part of its lever arm was able to take large steps in vitro but did not rescue in vivo functions. It was necessary for myosin VI to internally dimerize, triggering unfolding of a three-helix bundle and calmodulin binding in order to step normally in vitro and rescue endocytosis and Golgi morphology in myosin VI-null fibroblasts. A model for myosin VI emerges in which cargo binding triggers dimerization and unfolds the three-helix bundle to create a lever arm essential for in vivo functions.
authors.affiliation: Department of Physiology, University of Pennsylvania Perelman School of Medicine, 415 Curie Boulevard, 700 CRB, Philadelphia, PA 19104-6085, USA.
authors.forename: Monalisa
authors.initials: M
authors.lastname: Mukherjea
authors.affiliation: Department of Molecular Physiology and Biophysics, University of Vermont, Burlington, VT 05405, USA.
authors.forename: M Yusuf
authors.initials: MY
authors.lastname: Ali
authors.affiliation: Structural Motility, Centre de Recherche, Institut Curie, 75248 Paris, France; CNRS, UMR144, 26 rue d'Ulm, 75248 Paris Cedex 05, France.
authors.forename: Carlos
authors.initials: C
authors.lastname: Kikuti
authors.affiliation: Department of Physiology, University of Pennsylvania Perelman School of Medicine, 415 Curie Boulevard, 700 CRB, Philadelphia, PA 19104-6085, USA.
authors.forename: Daniel
authors.initials: D
authors.lastname: Safer
authors.affiliation: Department of Physiology, University of Pennsylvania Perelman School of Medicine, 415 Curie Boulevard, 700 CRB, Philadelphia, PA 19104-6085, USA.
authors.forename: Zhaohui
authors.initials: Z
authors.lastname: Yang
authors.affiliation: Structural Motility, Centre de Recherche, Institut Curie, 75248 Paris, France; CNRS, UMR144, 26 rue d'Ulm, 75248 Paris Cedex 05, France.
authors.forename: Helena
authors.initials: H
authors.lastname: Sirkia
authors.affiliation: Structural Motility, Centre de Recherche, Institut Curie, 75248 Paris, France; CNRS, UMR144, 26 rue d'Ulm, 75248 Paris Cedex 05, France.
authors.forename: Virginie
authors.initials: V
authors.lastname: Ropars
authors.affiliation: Structural Motility, Centre de Recherche, Institut Curie, 75248 Paris, France; CNRS, UMR144, 26 rue d'Ulm, 75248 Paris Cedex 05, France.
authors.forename: Anne
authors.initials: A
authors.lastname: Houdusse
authors.affiliation: Department of Molecular Physiology and Biophysics, University of Vermont, Burlington, VT 05405, USA.
authors.forename: David M
authors.initials: DM
authors.lastname: Warshaw
authors.affiliation: Department of Physiology, University of Pennsylvania Perelman School of Medicine, 415 Curie Boulevard, 700 CRB, Philadelphia, PA 19104-6085, USA. Electronic address: lsweeney@mail.med.upenn.edu.
authors.forename: H Lee
authors.initials: HL
authors.lastname: Sweeney
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D004705:Endocytosis; D005347:Fibroblasts / Q000378:metabolism; D006056:Golgi Apparatus / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D018995:Myosin Heavy Chains / Q000737:chemistry* / Q000378:metabolism; D055503:Protein Multimerization; D017434:Protein Structure, Tertiary; D013552:Swine
chemical_list: C089785:myosin VI; D018995:Myosin Heavy Chains