Figure 4.

Single-filament TIRF analysis of chimeric β tubulins. TIRF image overlays (A, C, E, and G) and kymographs (B, D, F, and H) showing microtubule extensions (red) growing from GMPCPP seeds (green) assembled with α/βIIB-tail-III (A–D) or α/βIII-tail-IIB (E–H). (I and J) Plus-end polymerization rates (I) and catastrophe frequencies (J) for chimeric α/βIIB-tail-III or α/βIII-tail-IIB microtubules at different free tubulin concentrations. Catastrophe frequency measurements for full-length α/βIIB (blue dashed line) and α/βIII (red dashed line) are shown for reference. The data were pooled from at least three independent experiments. Error bars are SD. For catastrophe frequency (f_cat), SD were calculated as f_cat/$\sqrt{n}$ (assuming a Poisson distribution), where n is the number of catastrophe events. Bars: (horizontal) 3 µm; (vertical) 2 min. Table 1 summarizes these measurements.