FIGURE 2:

Tracking intracellular movement of HaloTag-myosin Vb. (A) QD fluorescence in a cell expressing HaloTag–myosin Vb labeled with HaloTag ligand–QDs. The Laplacian of Gaussian-filtered images. The solid line represents the plasma membrane. (B) Changes in the position of a labeled HaloTag–myosin Vb in the boxed region of A (arrowheads). (C) Trajectory of the particle shown in B. Color represents time as shown below the image. (D, E) MSD curve derived from the whole trajectory (D) and instantaneous diffusion coefficient (E) of the particle shown in B. Red solid and dashed lines in D are the best-fit curves with Eq. 2 and the linear component, respectively. The parameters are D = 0.028 μm²/s and v = 0.32 μm/s. The blue solid line in the inset of D is the best-fit curve obtained using Eq. 4 with a value of 1.8 for exponent α, indicating that the movement was mainly dominated by directional movement. (F) Mean MSD curves of HaloTag ligand–QDs in cells expressing HaloTag–myosin Vb (black) or no HaloTag proteins (gray). The red solid and dashed lines are the best-fit curves obtained using Eq. 2 and the linear component, respectively. The parameters are D = 0.007 μm²/s and v = 0.037 μm/s. The black solid line is the best-fit curve obtained using Eq. 3 with D = 0.003 μm²/s. Data are presented as mean ± SEM.