MOLECULAR-BASIS FOR THE PHARMACOLOGICAL ACTIONS OF CLOSTRIDIUM-BOTULINUM TYPE-C2 TOXIN

  • 1 January 1984
    • journal article
    • research article
    • Vol. 230  (3) , 665-669
Abstract
The L chain of type C2 toxin produced by C. botulinum was isolated by high-performance liquid chromatography. The protein eluted as a single peak; as judged by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate, it had an apparent MW of 51,000 daltons. The L chain was an enzyme that possessed ADP-ribosylating activity. In experiments with synthetic substrates (homo-poly-L-amino acids; alanine, arginine, asparagine, aspartic acid, histidine, leucine, lysine, methionine, phenylalanine, proline, serine and tryptophan), only poly-L-arginine was ADP-ribosylated by the enzyme. In experiments with endogenous substrates (50,000 .times. g pellet and 50,000 .times. g supernatant from homogenates of mouse brain, liver and lung), the enzyme ADP-ribosylated proteins or polypeptides in both the particulate and soluble fractions. ADP-ribosylation of the soluble substrate was antagonized by adenine (Ki .apprx. 2.1 .times. 10-5 M) and by adenosine (Ki .apprx. 2.7 .times. 10-4 M); the reaction was reversed by a large molar excess of nicotinamide (0.1 M). ADP-ribosylation of soluble substrate was diminished when the substrate had been pretreated with 1,2-cyclohexanedione (0.1 M), a site reactive reagent that selectively modified arginine residues. Neither the L chain nor the H chain of the binary toxin possessed adenylate cyclase activity. Tissue fractions did possess endogenous adenylate cyclase activity, but the toxin did not stimulate this activity. The binary toxin produced by C. botulinum resembles other protein toxins.