The thermal denaturation of bovine cardiac G-actin.

The thermal denaturation of bovine cardiac G-actin has been studied by ultraviolet difference spectroscopy and circular dichroism between pH 7.5 and 10.5. As with proteins previously studied, thermal unfolding is incomplete compared with unfolding by urea or GuHCl. However, the same conformational change is observed over the pH range studied, and the available evidence indicates it is a two-state transition. Thermodynamic analysis of the data shows that deltaHo and deltaSo are strongly dependent on the temperature, that deltaCp is 1300 cal deg-1 mol-1, and that G-actin has a temperature of maximum stability near -5 degrees C.