Purification and characterization of ADP-ribosyltransferases (exoenzyme C3) of Clostridium botulinum type C and D strains

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Abstract
By cation-exchange column chromatography followed by gel filtration or hydroxylapatite column chromatography, ADP-ribosyltransferases (exoenzyme C3) were isolated from culture supernatants of Clostridium botulinum type C strains Stockholm (CST) and 6813 (C6813) and from type D strains South African (DSA) and 1873 (D1873), and their molecular properties were compared. The purified C3 enzymes were homogeneous in polyacrylamide gel electrophoresis. The C3 enzymes existed as single-chain polypeptides with molecular masses of 25.0 to 25.5 kDa and transferred ADP-riboses to the same substrates in rat brain membrane extract. The C3 enzymes could be roughly classified into two groups with respect to amino acid composition, amino-terminal sequence, and antigenicity. One group contains the C3 enzymes of strains C6813 and DSA, and the other contains those of strains CST and D1873. The specific activity of the C3 enzyme of strain C6813 was about 15 times higher than that of the C3 enzyme of strain CST. These results indicate that the classification of the C3 molecules differs from that of the neurotoxin molecules.