ADP-ribosylation of actin causes increase in the rate of ATP exchange and inhibition of ATP hydrolysis.

ADP-ribosylation of skeletal muscle actin by Clostridium perfringens iota toxin increased the rate of exchange of actin-bound [gamma-32P]ATP by unlabelled ATP about twofold. Increased exchange rates were observed with ATP and ATP[gamma S], much less with ADP but not with AMP or NAD. ADP-ribosylation of skeletal muscle actin reduced "basal" and Mg2+ (1 mM)-induced ATP hydrolysis by about 80%. Similar inhibition of ATP hydrolysis was observed with liver actin ADP-ribosylated by Clostridium botulinum C2 toxin. The data indicate that ADP-ribosylation of actin at Arg-177 largely affects the ATP-binding and ATPase activity.