Fig. 2. UNC-60B inhibits actin-bundling activity of UNC-87. (A) 10 µM rabbit F-actin was pre-incubated with 0-20 µM UNC-60B for 30 minutes, and varied concentrations of UNC-87 (0-20 µM) were added to the mixtures. After 30 minutes, the samples were centrifuged at 18,000 g for 10 minutes, and the supernatant (s) and pellets (p) were analyzed by SDS-PAGE. Representative gels of the experiments in the absence (a) and presence of 20 µM UNC-60B (b) are shown. Quantitative analysis of the results by densitometry is shown in (c), in which the percentages of sedimented (bundled) actin were plotted as a function of total UNC-87 concentrations (µM). Data are means ± s.d. of three experiments. (B) 1 µM Alexa Fluor 488-biotin-labeled rabbit F-actin was incubated with buffer only (a), 0.4 µM UNC-87 (b), 1 µM UNC-60B (c), or 1 µM UNC-60B and 0.4 µM UNC-87, and the filaments were observed by fluorescence microscopy. UNC-87 induced actin bundling (b, arrows), but the bundling was inhibited by the presence of UNC-60B (d). Bar, 20 µm.