Analysis of movement of MLCK and N75 on HASMC stress fibers. MLCK (shaded bars) and N75 (open bars). (A and B) Experimental conditions are summarized at the bottom. Buffers are as in Fig. 3. (A) QDs localized on stress fibers were counted, and the percentage of those that clearly moved are plotted. Error bars represent SEM. Within each ionic strength and molecule group, only the comparison between rigor and +ATP for N75 and for MLCK at 150 mM salt was not statistically different (P < 0.05; two-tailed t test). (B) Average D. Error bars represent SEM. For bars labeled “zero,” very few QD-MLCKs moved (see A), and D could not be determined reliably.