title: Discrete Step Sizes of Molecular Motors Lead to Bimodal Non-Gaussian Velocity Distributions under Force.
abstract: Fluctuations in the physical properties of biological machines are inextricably linked to their functions. Distributions of run lengths and velocities of processive molecular motors, like kinesin-1, are accessible through single-molecule techniques, but rigorous theoretical models for these probabilities are lacking. Here, we derive exact analytic results for a kinetic model to predict the resistive force (F)-dependent velocity [P(v)] and run length [P(n)] distribution functions of generic finitely processive molecular motors. Our theory quantitatively explains the zero force kinesin-1 data for both P(n) and P(v) using the detachment rate as the only parameter. In addition, we predict the F dependence of these quantities. At nonzero F, P(v) is non-Gaussian and is bimodal with peaks at positive and negative values of v, which is due to the discrete step size of kinesin-1. Although the predictions are based on analyses of kinesin-1 data, our results are general and should hold for any processive motor, which walks on a track by taking discrete steps.
authors: Biophysics Program, Institute for Physical Science and Technology, University of Maryland, College Park, Maryland 20742, USA.
authors: Huong T
authors: HT
authors: Vu
authors: Biophysics Program, Institute for Physical Science and Technology, University of Maryland, College Park, Maryland 20742, USA.
authors: Shaon
authors: S
authors: Chakrabarti
authors: Department of Physics, Case Western Reserve University, Cleveland, Ohio 44106, USA.
authors: Michael
authors: M
authors: Hinczewski
authors: Biophysics Program, Institute for Physical Science and Technology, University of Maryland, College Park, Maryland 20742, USA.
authors: D
authors: D
authors: Thirumalai
mesh_terms: D016547:Kinesins; D007700:Kinetics; D055595:Mechanical Phenomena; D008870:Microtubules; D008962:Models, Theoretical; D020409:Molecular Motor Proteins
chemical_list: D020409:Molecular Motor Proteins; D016547:Kinesins