Figure 4. XMAP215 targets one tubulin to the microtubule end by lattice diffusion.
(A) Kymograph depicting the diffusion of XMAP215-GFP alone on a GMPCPP microtubule (white arrows). (B) Kymograph depicting the XMAP215:tubulin complex diffusing on the microtubule (yellow arrows). Note the similarity to (A). (C) Plot of mean-squared displacement versus time for XMAP215-GFP against the time interval over which it was measured. A linear curve fit to the data yields a diffusion coefficient, D, of 0.3 ± 0.01 μm2·s-1. Error bars are the SEM of the squared displacement values (n = 1383). (D) Histogram of durations of XMAP215-GFP microtubule interactions. An exponential curve fit, corrected for photobleaching, yields a mean lifetime of the interactions, 〈t〉, of 2.45 ± 0.21 s.