Microtubule binding kinetics of membrane-bound kinesin-1 predicts high motor copy numbers on intracellular cargo

• DOI: 10.1073/pnas.1916204116
• Publication Date: 2019-12-10T22:45:43Z
• Authors: Rui Jiang; Steven Vandal; SooHyun Park; Sheereen Majd; Erkan Tüzel; William O. Hancock
• Keywords: Kinesin; Molecular motor; Vesicular Transport Proteins

Bidirectional vesicle transport along microtubules is necessary for cell viability and function, particularly in neurons. When multiple motors are attached to a vesicle, the distance travels before dissociating determined by race between detachment of bound attachment unbound motors. Motor rate constants (koff) can be measured via single-molecule experiments, but motor reattachment (kon) generally unknown, as they involve diffusion through bilayer, geometrical considerations tether length, intrinsic microtubule binding motor. To understand dynamics fluid lipid bilayers, we quantified accumulation fluorescently labeled kinesin-1 2-dimensional (2D) system where were linked supported bilayer. From first-order at varying densities, extrapolated koff that matched measurements 2D kon membrane-bound microtubule. This consistent with being able reach roughly 20 tubulin subunits when attaching By incorporating cholesterol reduce membrane diffusivity, demonstrate this not limited rate, instead rate. For intracellular trafficking, predicts long-range 100-nm-diameter vesicles requires 35 motors, suggesting teamwork different classes clustering may play significant roles transport.