Figure 5
From: Step Sizes and Rate Constants of Single-headed Cytoplasmic Dynein Measured with Optical Tweezers
Movement and force generation of single molecules of dimeric dynein (GST-D384). (A) Typical displacement of the trap bead toward the minus end of the microtubule at 1 mM ATP. Red lines: dwell time analyzed by the step-finding algorithm in figure 5D. Orange lines: peak force immediately before dynein dissociates from the microtubule. Numbers in figures: the step size was analyzed in figure 5B. (B) The histograms of the step size were fit to multiple Gaussian distributions. Over a 1.1 pN force, the step size was calculated to be 8.23 ± 0.09 nm, 16.26 nm and −8.23 nm. (C) The histograms of the dwell time were fit to a single-exponential curve with a constant of 45 ± 1 ms (<0.5 pN), 69 ± 1 ms (0.5–1.1 pN) or 101 ± 1 ms (>1.1 pN). (D) The stepping rate depending on the force was fitted to a single-exponential curve. The maximum stepping rate under no load was 25.3 ± 0.2 s−1. (E) Relationship between force and velocity. The velocity was calculated as the stepping rate multiplied by the mean step size. The stall force and maximum velocity were calculated to be 1.85 ± 0.01 pN and 387 ± 5 nm/s, respectively, by fitting the data with a linear approximation. The error bars in D and E are almost within the symbols. (F) The histogram of the peak force was fit to a single-exponential curve with a constant of 0.75 ± 0.03 pN. N and R2 in panels B-F indicate the number of measurements and the square of the regression error, respectively.
