Botulinum ADP‐ribosyltransferase activity as affected by detergents and phospholipids

Abstract
GTP‐binding proteins with Mr values of 22 000 and 25 000 in bovine brain cytosol were ADP‐ribosylated by an exoenzyme (termed C3) purified from Clostridium botulinum type C. The rate of C3‐catalyzed ADP‐ribosylation of the partially purified substrates was extremely low by itself, but was increased enormously when a protein factor(s) obtained from the cytosol was simultaneously added. The rate of the C3‐catalyzed reaction was also stimulated by the addition of certain types of detergents or phospholipids even in the absence of the protein factors. The ADP‐ribosylation appeared to be enhanced to an extent more than the additive effect of either the protein factors or the detergents (and phospholipids). Thus, ADP‐ribosylation catalyzed by botulinum C3 enzyme was affected not only by cytoplasmic protein factors but also by detergents or phospholipids in manners different from each other.