title: Distinct conformations of the kinesin Unc104 neck regulate a monomer to dimer motor transition.
abstract: Caenhorhabditis elegans Unc104 kinesin transports synaptic vesicles at rapid velocities. Unc104 is primarily monomeric in solution, but recent motility studies suggest that it may dimerize when concentrated on membranes. Using cryo-electron microscopy, we observe two conformations of microtubule-bound Unc104: a monomeric state in which the two neck helices form an intramolecular, parallel coiled coil; and a dimeric state in which the neck helices form an intermolecular coiled coil. The intramolecular folded conformation is abolished by deletion of a flexible hinge separating the neck helices, indicating that it acts as a spacer to accommodate the parallel coiled-coil configuration. The neck hinge deletion mutation does not alter motor velocity in vitro but produces a severe uncoordinated phenotype in transgenic C. elegans, suggesting that the folded conformation plays an important role in motor regulation. We suggest that the Unc104 neck regulates motility by switching from a self-folded, repressed state to a dimerized conformation that can support fast processive movement.
authors.affiliation: Department of Cell Biology, The Scripps Research Institute, La Jolla, CA 92037, USA.
authors.forename: Jawdat
authors.initials: J
authors.lastname: Al-Bassam
authors.forename: Yujia
authors.initials: Y
authors.lastname: Cui
authors.forename: Dieter
authors.initials: D
authors.lastname: Klopfenstein
authors.forename: Bridget O
authors.initials: BO
authors.lastname: Carragher
authors.forename: Ronald D
authors.initials: RD
authors.lastname: Vale
authors.forename: Ronald A
authors.initials: RA
authors.lastname: Milligan
mesh_terms: D000244:Adenosine Diphosphate / Q000378:metabolism; D000251:Adenosine Triphosphatases / Q000235:genetics / Q000378:metabolism; D000266:Adenylyl Imidodiphosphate / Q000494:pharmacology; D000595:Amino Acid Sequence; D000818:Animals; D030801:Animals, Genetically Modified; D017173:Caenorhabditis elegans; D029742:Caenorhabditis elegans Proteins; D020134:Catalytic Domain / Q000502:physiology; D019281:Dimerization; D016547:Kinesins / Q000737:chemistry* / Q000235:genetics / Q000648:ultrastructure; D008958:Models, Molecular; D020409:Molecular Motor Proteins / Q000737:chemistry* / Q000235:genetics; D008969:Molecular Sequence Data; D009069:Movement Disorders / Q000235:genetics; D009154:Mutation / Q000502:physiology; D009419:Nerve Tissue Proteins / Q000737:chemistry* / Q000235:genetics / Q000648:ultrastructure; D009711:Nucleotides / Q000235:genetics / Q000378:metabolism; D017434:Protein Structure, Tertiary / Q000502:physiology; D017386:Sequence Homology, Amino Acid; D013572:Synaptic Vesicles / Q000378:metabolism* / Q000648:ultrastructure
chemical_list: D029742:Caenorhabditis elegans Proteins; D020409:Molecular Motor Proteins; D009419:Nerve Tissue Proteins; D009711:Nucleotides; C423186:UNC-104 protein, C elegans; D000266:Adenylyl Imidodiphosphate; D000244:Adenosine Diphosphate; D000251:Adenosine Triphosphatases; D016547:Kinesins