Figure 3.

Kinesin-8^Klp67A regulates MT plus end dynamics in vitro. (A) Schematic presentation of the in vitro MT polymerization assay. (B) Inhibitory effect of kinesin-8^Klp67A on MT polymerization from the seed (n = 84, 74, 84, 74, and 94; from left to right). (C) MT dynamics are represented by kymographs. MTs stabilized with GMPCPP are colored blue, dynamic MTs are magenta, and kinesin-8^Klp67A-GFP (0 or 10 nM) is green. Horizontal bar, 5 µm; vertical bar, 120 s. (D–H) Parameters of MT plus end dynamics. Experiments were performed twice, and the combined data are displayed (the change in rate/frequency by kinesin-8^Klp67A was reproduced). n = 41 + 33 (0 nM), 25 + 31 (5 nM), and 20 + 41 (10 nM). Each dot represents a value obtained from a single MT, and error bars represent SEM. Note that rescue was rarely observed in the absence of kinesin-8^Klp67A. *, P < 0.03; ***, P < 0.002; ****, P < 0.0001 or by Games-Howell (D–F) or Steel Dwass (G) tests. (I and J) Correlation between the amount of kinesin-8^Klp67A-GFP at the tip and growth (I; n = 397 [5 nM] and 494 [10 nM]) or shrinkage (J; n = 116 [5 nM] and 293 [10 nM]) rate. Negative correlation was found for shrinkage rate (P < 2 × 10⁻¹⁶, likelihood ratio test).