Figure 9.

E421K reduces the localization of kinesin Kip3p at microtubule plus-ends. (A) Representative Z-series maximum projections showing fluorescently labeled Kip3p (red) and α-tubulin (green) in live diploid WT, heterozygous tub2-E410K and heterozygous tub2-E421K yeast cells. Kip3p-3YFP forms bright foci at the plus-ends of most WT astral microtubules, but these bright foci are rarely found at the plus-ends of mutant astral microtubules (solid white arrowheads). Similar to microtubules in tub2-E410K cells, most astral microtubule plus-ends in tub2-E421K cells had a significant reduction in Kip3p-3YFP localization (open white arrowheads). Signal intensities were adjusted equally in both channels for all strains. (B) Quantification of Kip3p-3YFP levels at the plus-ends of microtubules in cells containing Tub2, tub2p-E410K and tub2p-E421K. Localization of Kip3p intensity was reduced by 58% in tub2-E421K cells and by 81% in tub2-E410K cells. 60–150 microtubules from three to four clones on two separate days each were imaged for each condition. n≥ 6 for all conditions. n represents the averaged values for each clone from 1 day. Error represented as SEM in graphs. P < 0.001 versus WT by unpaired Student's t-test.