RT Journal Article SR Electronic T1 Kinesin-8-specific loop-2 controls the dual activities of the motor domain according to tubulin protofilament shape JF bioRxiv FD Cold Spring Harbor Laboratory SP 2022.02.28.480783 DO 10.1101/2022.02.28.480783 A1 Hunter, Byron A1 Benoit, Matthieu P.M.H. A1 Asenjo, Ana B. A1 Doubleday, Caitlin A1 Trofimova, Daria A1 Sosa, Hernando A1 Allingham, John S. YR 2022 UL http://biorxiv.org/content/early/2022/03/14/2022.02.28.480783.abstract AB Kinesin-8s are dual-activity motor proteins that can move processively on microtubules and depolymerize microtubule plus-ends, but their mechanism of combining these distinct activities remains unclear. We addressed this by obtaining cryo-EM structures (2.6-3.9 Å) of Candida albicans Kip3 in different catalytic states on the microtubule lattice and on a curved microtubule end mimic, as well as a microtubule-unbound CaKip3-ADP crystal structure (2.0 Å). Together with biochemical analyses of CaKip3 and kinesin-1 mutants, we define a model that explains the kinesin-8 mechanism. The microtubule depolymerization activity originates in conformational changes of the kinesin-8 motor core that are amplified by its dynamic loop-2. On curved microtubule ends, loop-1 assists depolymerization by inserting into preceding motor domains, forming head-to-tail arrays of kinesin-8s that complement loop-2 contacts with curved tubulin. On straight tubulin protofilaments in the microtubule lattice, extended loop-2-tubulin contacts inhibit conformational changes in the motor core, but in the ADP-Pi state these contacts are relaxed, allowing neck-linker docking for motility. These tubulin shape-induced alternations between pro-microtubule-depolymerization and pro-motility kinesin states, regulated by loop-2, are the key to the dual activity of kinesin-8 motors.Competing Interest StatementThe authors have declared no competing interest.