Analysis of movement of MLCK and N75 on MLCK-induced actin bundles. MLCK (shaded bars) and N75 (open bars). All data are for actin bundles, except for those indicated as for actin-Tm bundles. (A and B) Conditions are summarized at the bottom. The 150-mM KCl corresponding to buffers A–D and the 300-mM KCl is the same except with added salt. (A) QDs localized on actin were counted, and those that clearly moved were plotted as a percentage of total. Error bars represent SEM. Each bar for MLCK motion is an analysis of the behaviors of at least 500 QDs (average number counted was 1,212) that met the criteria described in Determination of frequency of QD motion in Materials and methods. Data for the first three bars in the 150-mM KCl group and the sole N75 bar were not significantly different from one another (P > 0.05; two-tailed t test). This was also true for the first two bars in the 300-mM KCl group. All other comparisons within each ionic strength group were significantly different (P < 0.05). (B) Average D. Error bars represent SEM.