HEAT DENATURATION OF RABBIT SKELETAL G-ACTIN IN THE PRESENCE OF ATP

Heat treatments at pH 7‐5 induced the polymerisation of G‐actin without the addition of KCl or MgCl2. This heat‐induced polymerisation of G‐actin was accompanied by the splitting of ATP. The polymerised actin at 45°C could be depolymerised by dialysis against a solution containing ATP. Electron microscopic observation of actin showed that irregular filaments were formed after heat treatment at 45°C for 3h, and at 55°C small filamentous pieces were formed. The abilities of heavy meromyosin ATPase (EC 3.6.1.32) activation and ATP splitting of G‐actin were drastically impaired by heating to temperatures above 50°C. Studies of the temperature dependence of fluorescence and viscosity data also revealed that heat denaturation of G‐actin in the presence of ATP occurred steeply between 45°C and 55°C. Copyright © 1990 John Wiley & Sons, Ltd