ADP-RIBOSYLATION OF DROSOPHILA INDIRECT-FLIGHT-MUSCLE ACTIN AND ARTHRIN BY CLOSTRIDIUM-BOTULINUM C2 TOXIN AND CLOSTRIDIUM-PERFRINGENS IOTA TOXIN

Purified Drosophila indirect-flight-muscle actin and arthrin, an actin -ubiquitin conjugate, were ADP-ribosylated by Clostridium botulinum C2 toxin and Clostridium perfringens iota toxin. Phalloidin treatment in hibited the ADP-riboyslation of Drosophila actin and arthrin. Like act in, the ADP-ribose-arthrin linkage was sensitive towards hydroxylamine treatment, indicating arginine as the amino acid acceptor. Actin tran slated in vitro from the indirect-flight-muscle-specific gene Act88F w as ADP-ribosylated by C. botulinum C2 toxin and C. perfringens iota to xin. Actin from the R177Q mutant of Act88F translated in vivo was not ADP-ribosylated confirming Arg-177 as the ADP-ribose acceptor. Mutant L176M actin was modified by both toxins, indicating that amino acid 17 6 of actin does not define the substrate specificity of C. botulinum C 2 toxin. Whereas the gene products of various C-terminal mutants of Ac t88F translated in vitro (E334K, V339I, E364K, G368E, R372H) were subs trates for ADP-ribosylation by C. botulinum C2 toxin and by C. perfrin gens iota toxin, neither toxin modified the N-terminal O-12 deletion m utant.