Cell News 3/2013
20
Figure 3.
Xenopus
Spindle Length Is Directly Proportional to XMAP215 Microtubule Polymerase Activity:
(a) XMAP215 acts as a processive polymerase. (b) Schematic of
Xenopus laevis
XMAP215’s domain structure indicating the point mutations introduced.
(c) Tubulin affinity and maximal microtubule growth promoted by XMAP215 and the mutants. (d)
Xenopus
egg extract was MOCK or XMAP215 depleted,
different point mutants of XMAP215 were added back. Depletion efficiency and accuracy of add-back were controlled by Western blot analysis, tubulin
served as a loading control. (e) Spindles were assembled in the presence of different XMAP215 mutants. The upper rows show a representative spindle
(red: microtubules, blue: DNA), the lower rows show an average image of all spindles from three independent experiments, the average spindle length is
indicated. SE, n=40. Scale bars: 10 µm. (f) Average spindle length measured in the presence of different XMAP215 point mutants. Error bars indicate SE
(n=40). (g) Spindle length plotted versus the maximal
in vitro
microtubule growth velocity promoted by different XMAP215 mutants. Grey areas indicate
the 95% confidence intervals of the fitted curves. Adapted from
17
.
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