Predicted interactions of MLCK/N75 that affect the frequency of motion according to our simple percolation model. The left side of each box shows barriers to MLCK/N75 motion, and the right side shows molecules moving where barrier concentration is lower. Frequency of motion from Figs. 3 and 6 is shown in red type above each molecule. Top (A–D) and bottom (E–G) rows at 150 mM KCL and 300 mM KCl, respectively. In vitro actin bundles (A and E) or stress fibers (B–D and F and G) are parallel blue lines (actins shown apart for clarity). Text at top summarizes conditions (blue) and acto-myosin state (black). The key is in the bottom right box.