Examination of actin polymerization and viscosity induced by cations and ionic strength when cross-linked by alpha-actinin.

Increasing potassium chloride concentration from 0 to 100 mM and magnesium chloride from 0 to 2 mM show a parallel rate increase in polymerizing actin, whereas increasing calcium chloride concentration from 0 to 0.2 mM decreases the rate of polymerizing actin. The presence of alpha-actinin has little influence on the polymerization kinetics of actin under these conditions. Viscometric measurements indicate that the presence of various mono- and divalent cations, ionic strength, and alpha-actinin in combination are responsible for changes in the mechanical properties of solutions containing actin. The actin filament dynamic behavior is drastically reduced under these conditions as confirmed by quasi-elastic light scattering.