The effect on actin ATPase of phalloidin and tetramethylrhodamine phalloidin

Abstract
Actin polymerization has been studied in the absence of excess nucleotide. Using G‐actin ATP monomers, it was shown that mechanical shearing stimulates ATP hydrolysis. The procedures used enabled the detection of differential effects of phalloidin and tetramethylrhodamine‐phalloidin, on the Pi‐release step of the actin ATPase. It is concluded that tetramethylrhodamine, in contrast to phalloidin, accelerates Pi‐release from actin filaments.