Figure 1.

Actin-driven motility of lipid vesicles coated with ActA. (a) Fluorescence images of an actin-propelled vesicle at three time points. A fraction of the lipids (0.5%) was labeled with Oregon green. Actin was labeled (2%) with rhodamine (red). (Left) Fluorescence images of actin comet tails. (Center) Lipid fluorescence. (Right) Overlay of Left and Center. Parts of the lipid structures containing both lipids and actin appear yellow in the images. The yellow region on the vesicle clearly shows the actin “cup” enclosing one hemisphere of the vesicle. The bottom left shows the lipid aggregate from which the vesicle emerged. Time is indicated in seconds in the bottom right corners. (b) Phase-contrast image of a moving vesicle with a phase-dense comet tail. (c) Fluorescence image of the same vesicle as shown in b with fluorescently labeled ActA molecules (blue). ActA is colocalized with the actin cup on the vesicle surface. (d) Schematic diagram of a lipid bilayer vesicle (green) coated with ActA (blue) and surrounded by a mesh of actin filaments (red) in contact with the membrane. (Scale bars, 4 μm.)