ADP-RIBOSYLATION OF ACTIN ISOFORMS BY CLOSTRIDIUM-BOTULINUM-C2 TOXIN AND CLOSTRIDIUM-PERFRINGENS-IOTA TOXIN

The substrate specificities of the actin‐ADP‐ribosylating toxins, Clostridium botulinum C2 toxin and Clostridium perfringens iota toxin were studied by using five different preparations of actin isoforms: α‐skeletal muscle actin, α‐cardiac muscle actin, gizzard γ‐smooth muscle actin, spleen β‐ and γ‐cytoplasmic actin, and aortic smooth muscle actin containing α‐ and γ‐smooth muscle actin isoforms. C. perfringens iota toxin ADP‐ribosylated all actin isoforms tested, whereas C. botulinum C2 toxin did not modify α‐skeletal muscle actin or α‐cardiac muscle actin. Spleen β/γ‐cytoplasmic actin and gizzard γ‐smooth muscle actin were substrates of C. botulinum C2 toxin. In the aortic smooth muscle actin preparation, γ‐smooth muscle actin but not α‐smooth muscle actin was ADP‐ribosylated by C. botulinum C2 toxin. The data indicate that, in contrast to C. perfringens iota toxin, C. botulinum C2 toxin ADP‐ribosylates only β/γ‐cytoplasmic and γ‐smooth muscle actin and suggest that the N‐terminal region of actin isoforms define the substrate specificity for ADP‐ribosylation by C. botulinum C2 toxin. Copyright © 1990, Wiley Blackwell. All rights reserved