The control of cellular motility and the role of gelsolin.

Solation of actin gel by gelsolin is much less efficient in the presence of a high concentration of macromolecular solutes. The rigidity of the gel formed by 12 microM actin is lowered from 4 to 0.33 dynes/cm2 by 15 nM gelsolin, while in 6% (w/v) polyethylene glycol, rigidity is lowered only from 20 to 11 dynes/cm2 by 64 nM gelsolin. Owing to the large concentration of protein, transitions in the fluid- and gel-like properties of the cytoplasm are expected to be problematic when promoted by gelsolin alone.