Anomalous aggregation of Clostridium perfringens enterotoxin under dissociating conditions

Polyacrylamide gel electrophoresis of highly purified Clostridium perfringens enterotoxin revealed electrophoretic microheterogeneity of the enterotoxin, apparently because of slight charge differences in the peptides. Detergent gel electrophoresis showed that purified enterotoxin formed high molecular weight aggregates in the presence of both sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide. No conditions capable of inhibiting this phenomenon were found. Although a molecular weight of 35 000 daltons has been reported in the literature, the experimentally determined molecular weight values in the presence of detergents corresponded to multiples of a theoretical subunit molecular weight of 17 500 daltons. Binding studies performed by equilibrium dialysis and ultracentrifugation methods revealed that the enterotoxin bound very small amounts of SDS per gram of protein. The evidence presented indicates possible detergent induced structural alterations of the protein.