ADP-RIBOSYLATION OF ACTIN BY CLOSTRIDIUM-PERFRINGENS IOTA-TOXIN AND TURKEY ERYTHROCYTE ADP-RIBOSYLTRANSFERASE-A - EFFECTS ON PROFILIN-REGULATED NUCLEOTIDE EXCHANGE AND ATPASE ACTIVITY

Effects of ADP-ribosylation of skeletal muscle alpha-actin by Clostrid ium perfringens iota toxin and by turkey erythrocyte ADP-ribosyltransf erase A on profilin-regulated nucleotide exchange and ATPase activity were compared. ADP-ribosylation of actin at Arg177 by Clostridium perf ringens iota toxin increased the nucleotide dissociation rate from 2.2 x10(-3) s(-1) to 4.5x10(-3) s(-1) without affecting the profilin-induc ed stimulation of nucleotide exchange. In contrast, ADP-ribosylation o f actin at Arg95/Arg372 induced by turkey erythrocyte transferase decr eased the nucleotide dissociation rate to 1.5x10(-3) s(-1) and inhibit ed the profilin-induced stimulation of nucleotide exchange. Whereas to xin-induced ADP-ribosylation at Arg177 blocked actin ATPase, basal G-a ctin ATPase was not altered by ADP-ribosylation at Arg95/Arg372 but in hibited profilin effects on actin ATPase.