title: Processivity of the single-headed kinesin KIF1A through biased binding to tubulin.
abstract: Conventional isoforms of the motor protein kinesin behave functionally not as 'single molecules' but as 'two molecules' paired. This dimeric structure poses a barrier to solving its mechanism. To overcome this problem, we used an unconventional kinesin KIF1A (refs 5, 6) as a model molecule. KIF1A moves processively as an independent monomer, and can also work synergistically as a functional dimer. Here we show, by measuring its movement with an optical trapping system, that a single ATP hydrolysis triggers a single stepping movement of a single KIF1A monomer. The step size is distributed stochastically around multiples of 8 nm with a gaussian-like envelope and a standard deviation of 15 nm. On average, the step is directional to the microtubule's plus-end against a load force of up to 0.15 pN. As the source for this directional movement, we show that KIF1A moves to the microtubule's plus-end by approximately 3 nm on average on binding to the microtubule, presumably by preferential binding to tubulin on the plus-end side. We propose a simple physical formulation to explain the movement of KIF1A.
authors.affiliation: Department of Cell Biology and Anatomy, University of Tokyo, Graduate School of Medicine, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Okada
authors.forename: Hideo
authors.initials: H
authors.lastname: Higuchi
authors.forename: Nobutaka
authors.initials: N
authors.lastname: Hirokawa
mesh_terms: D000244:Adenosine Diphosphate / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D006868:Hydrolysis; D016547:Kinesins / Q000378:metabolism*; D008870:Microtubules / Q000737:chemistry / Q000378:metabolism; D009068:Movement; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D011485:Protein Binding; D016008:Statistical Distributions; D013269:Stochastic Processes; D014404:Tubulin / Q000378:metabolism*
chemical_list: C094065:KIF1A protein, human; D009419:Nerve Tissue Proteins; D014404:Tubulin; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D016547:Kinesins