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. Author manuscript; available in PMC: 2012 Jan 25.
Published in final edited form as: Curr Biol. 2011 Jan 13;21(2):154–160. doi: 10.1016/j.cub.2010.12.038

Figure 3. The kinesin-5 tail domain increases processivity and association time with microtubules.

Figure 3

(A) Schematic of the single molecule motility assay. Single molecule TIRF microscopy was used to observe the motion of individual kinesin-5 molecules moving along surface-immobilized microtubules. (B–G) Kymographs showing the motion of (B–D) Kin5-GFP and (E–G) Kin5-Δtail-GFP along microtubules in PEM70 (2 mM ATP) and increasing concentrations of KCl. Motor protein concentration had to be increased to obtain sufficient numbers of binding events as ionic strength increased. [Kin5-GFP]: 60 pM in PEM70 (B), 120 pM in PEM70+40 mM KCl (C), and 240 pM in PEM70+80 mM KCl (D). [Kin5-Δtail-GFP]: 150 pM in PEM70 (E), 600 pM in PEM70+40 mM KCl (F), 1500 pM in PEM70+80 mM KCl (G). (H–J) Mean squared displacement (MSD) analysis of motility on single microtubules for Kin5-GFP in PEM70+40 mM KCl (H) and for Kin5-GFP (I) and Kin5-Δtail-GFP (J) in PEM70. Solid lines are fits to MSD = v2t2 + 2Dt+ offset. (K–M) Histograms of association times for Kin5-GFP in PEM70+40 mM KCl (K) and for Kin5-GFP (L) and Kin5-Δtail-GFP (M) in PEM70. Average association times, determined from fits to single exponentials (solid curves) are indicated. Scale bars: 3µm, error bars = sem.