Fluctuation in the microtubule sliding movement driven by kinesin in vitro

Abstract

We studied the fluctuation in the translational sliding movement of microtubules driven by kinesin in a motility assay in vitro. By calculating the mean-square displacement deviation from the average as a function of time, we obtained motional diffusion coefficients for microtubules and analyzed the dependence of the coefficients on microtubule length. Our analyses suggest that 1) the motional diffusion coefficient consists of the sum of two terms, one that is proportional to the inverse of the microtubule length (as the longitudinal diffusion coefficient of a filament in Brownian movement is) and another that is independent of the length, and 2) the length-dependent term decreases with increasing kinesin concentration. This latter term almost vanishes within the length range we studied at high kinesin concentrations. From the length-dependence relationship, we evaluated the friction coefficient for sliding microtubules. This value is much larger than the solvent friction and thus consistent with protein friction. The length independence of the motional diffusion coefficient observed at sufficiently high kinesin concentrations indicates the presence of correlation in the sliding movement fluctuation. This places significant constraint on the possible mechanisms of the sliding movement generation by kinesin motors in vitro.

Fluctuation of actin sliding over myosin thick filaments in vitro

“…where r(∆t) is the net displacement of an actin filament along its trajectory in a given time interval (∆t), <⋅> shows the average, D m is the effective diffusion coefficient, and σ r0 2 is a term due to position measurement errors 14,16 . As a result, we used the overlap method in this study.…”

“…The positional data were then processed with a computer, as described previously 14 . Since native thick filaments are bipolar 9,10 , care was taken so as to determine the positions of a sliding actin filament while its entire length stayed within the range of a half side of a thick filament.…”

“…3, thus showing that the variance grew over time. This time-dependent term is due to the fluctuation inherent in the sliding motion rather than artifactual noises (see Imafuku et al for further clarification 14,16 ). The half of the slope of the fitted regression line in Fig.…”

Direction and speed of microtubule movements driven by kinesin motors arranged on catchin thick filaments

“…The images were recorded with a digital videocassette recorder (DSR-45, Sony, Tokyo, Japan). The images were then analyzed essentially as described previously [Imafuku et al, 1996;Noda et al, 2005]. In brief, the recorded images were transferred to a computer frame by frame, and the x and y coordinates of the leading end of the microtubules on each frame was digitized by using a mouse-driven cursor on the screen.…”

Protein Linear Molecular Motor‐Powered Nanodevices

“…The past four decades have witnessed extensive investigations into the molecular mechanisms that underpin the operation of these motors, which are central to biology. These fundamental investigations have been (i) experimental-aided by advances in molecular imaging, single molecule manipulation techniques, such as optical trapping, and development of motility assays, [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] and (ii) theoretical-analyzing and attempting to explain the solely understanding their mechanisms per se. These devices are hybrids: consisting of naturally evolved protein motors, biochemically interfaced and housed in glass or polymeric microstructures, possibly with external (fluidic or EM) control of motility.…”