Figure 2.
Figure 2. Competition of antagonistic motors in antiparallel microtubule sliding. (A) Scheme of a pair of polarity-marked microtubules in a sliding assay (symbols as in Fig. 1 A). (B) Different motility states of microtubule pairs. Example kymographs of a freely movable Alexa Fluor 568–microtubule (MT; green) bound via motor cross-links to a surface-immobilized Cy5-microtubule (red) in the presence of 0.5 nM XCTK2 and 0.66 nM Eg5-GFP, illustrating Eg5-dominated unidirectional antiparallel sliding, XCTK2-dominated unidirectional antiparallel sliding, movement with unstable directionality, and static parallel binding (from left to right). All kymographs are taken from the same sample. (C) Histograms of the instantaneous velocities of antiparallel sliding microtubules during the competition between 0.5 nM XCTK2 and varying concentrations of Eg5 (indicated to the right). Histograms contain all data of three independent experiments. (D) Fractions of Eg5-GFP– and XCTK2-dominated movement during microtubule sliding, calculated as described in Materials and methods. (E) Mean velocities of all microtubule movements and mean velocities separately determined for only the XCTK2-dominated microtubule movements and for the Eg5-GFP–dominated movements compiled from C. (F) Mean displacement curves of antiparallel sliding microtubules during the competition. Color code as in C and G. The highest, the lowest, and the balance point Eg5 concentrations are emphasized by thick lines. (G, left) MSD curves of antiparallel sliding microtubules. (top right) MSD curve of antiparallel sliding microtubules in the presence of 0.5 nM XCTK2 (black) fitted with a parabolic function (red). (bottom right) MSD curve of antiparallel sliding microtubules in the presence of 0.5 nM XCTK2 and 0.66 nM Eg5-GFP (black) fitted with a parabolic function (from 0 to 36 s; red) and a linear function (from 36 s onward; blue). The dashed lines show continuations of the fit equation in the data range that was not used for the fit. Error bars in D and E are standard errors of the mean. Dotted lines in F and G are 95% confidence intervals. All experiments shown were performed in assay buffer containing 50 mM KCl. Bars: (B, horizontal) 5 µm; (B, vertical) 120 s.

Competition of antagonistic motors in antiparallel microtubule sliding. (A) Scheme of a pair of polarity-marked microtubules in a sliding assay (symbols as in Fig. 1 A). (B) Different motility states of microtubule pairs. Example kymographs of a freely movable Alexa Fluor 568–microtubule (MT; green) bound via motor cross-links to a surface-immobilized Cy5-microtubule (red) in the presence of 0.5 nM XCTK2 and 0.66 nM Eg5-GFP, illustrating Eg5-dominated unidirectional antiparallel sliding, XCTK2-dominated unidirectional antiparallel sliding, movement with unstable directionality, and static parallel binding (from left to right). All kymographs are taken from the same sample. (C) Histograms of the instantaneous velocities of antiparallel sliding microtubules during the competition between 0.5 nM XCTK2 and varying concentrations of Eg5 (indicated to the right). Histograms contain all data of three independent experiments. (D) Fractions of Eg5-GFP– and XCTK2-dominated movement during microtubule sliding, calculated as described in Materials and methods. (E) Mean velocities of all microtubule movements and mean velocities separately determined for only the XCTK2-dominated microtubule movements and for the Eg5-GFP–dominated movements compiled from C. (F) Mean displacement curves of antiparallel sliding microtubules during the competition. Color code as in C and G. The highest, the lowest, and the balance point Eg5 concentrations are emphasized by thick lines. (G, left) MSD curves of antiparallel sliding microtubules. (top right) MSD curve of antiparallel sliding microtubules in the presence of 0.5 nM XCTK2 (black) fitted with a parabolic function (red). (bottom right) MSD curve of antiparallel sliding microtubules in the presence of 0.5 nM XCTK2 and 0.66 nM Eg5-GFP (black) fitted with a parabolic function (from 0 to 36 s; red) and a linear function (from 36 s onward; blue). The dashed lines show continuations of the fit equation in the data range that was not used for the fit. Error bars in D and E are standard errors of the mean. Dotted lines in F and G are 95% confidence intervals. All experiments shown were performed in assay buffer containing 50 mM KCl. Bars: (B, horizontal) 5 µm; (B, vertical) 120 s.

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