Effect of α-actinin on actin structure viscosity studies

Abstract

The effect of ATP on ability of α-actinin to increase viscosity of F-actin was measured in three different solutions: 100 mM KCl; 100 mM KCl/1 mM Mg 2+; and Mg 2+ alone at concentrations of 1–6 mM. When ATP and Mg 2+ are added at equimolar ratios or at added [ATP] to added [Mg 2+] greater than equimolar, α-actinin has no effect on F-actin viscosity in the absence of KCl. ATP decreases viscosity of α-actinin/F-actin mixtures by 20% even in the presence of KCl, evidently because ATP affects the α-actinin-F-actin interaction. Molar ratios of 1 α-actinin to 49 actins increase specific viscosity of F-actin approx. 2-fold at 37°C in the presence of 1 mM ATP, so ATP does not prevent the α-actinin-F-actin interaction.