title: Conventional kinesin mediates microtubule-microtubule interactions in vivo.
abstract: Conventional kinesin is a ubiquitous organelle transporter that moves cargo toward the plus-ends of microtubules. In addition, several in vitro studies indicated a role of conventional kinesin in cross-bridging and sliding microtubules, but in vivo evidence for such a role is missing. In this study, we show that conventional kinesin mediates microtubule-microtubule interactions in the model fungus Ustilago maydis. Live cell imaging and ultrastructural analysis of various mutants in Kin1 revealed that this kinesin-1 motor is required for efficient microtubule bundling and participates in microtubule bending in vivo. High levels of Kin1 led to increased microtubule bending, whereas a rigor-mutation in the motor head suppressed all microtubule motility and promoted strong microtubule bundling, indicating that kinesin can form cross-bridges between microtubules in living cells. This effect required a conserved region in the C terminus of Kin1, which was shown to bind microtubules in vitro. In addition, a fusion protein of yellow fluorescent protein and the Kin1tail localized to microtubule bundles, further supporting the idea that a conserved microtubule binding activity in the tail of conventional kinesins mediates microtubule-microtubule interactions in vivo.
authors.affiliation: Max-Planck-Institut für terrestrische Mikrobiologie, D-35043 Marburg, Germany.
authors.forename: Anne
authors.initials: A
authors.lastname: Straube
authors.forename: Gerd
authors.initials: G
authors.lastname: Hause
authors.forename: Gero
authors.initials: G
authors.lastname: Fink
authors.forename: Gero
authors.initials: G
authors.lastname: Steinberg
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D001692:Biological Transport; D017124:Conserved Sequence; D005656:Fungal Proteins / Q000235:genetics / Q000502:physiology*; D016547:Kinesins / Q000235:genetics / Q000502:physiology*; D008870:Microtubules / Q000378:metabolism* / Q000502:physiology / Q000648:ultrastructure; D008969:Molecular Sequence Data; D009154:Mutation; D011485:Protein Binding; D011993:Recombinant Fusion Proteins / Q000032:analysis; D016415:Sequence Alignment; D017384:Sequence Deletion; D014588:Ustilago / Q000737:chemistry / Q000166:cytology / Q000378:metabolism*
chemical_list: D005656:Fungal Proteins; C107102:KIN1 protein, Ustilago maydis; D011993:Recombinant Fusion Proteins; D016547:Kinesins