SITE-DIRECTED MUTAGENESIS OF CLOSTRIDIUM-PERFRINGENS BETA-TOXIN - EXPRESSION OF WILD-TYPE AND MUTANT TOXINS IN BACILLUS-SUBTILIS

Recombinant beta-toxin has been expressed and secreted from Bacillus s ubtilis. Biological activity was tested in vivo and in vitro. The leth al dose in mice was determined. Hemolysis of rabbit and sheep erythroc ytes was tested but no effect was observed. Seven mutant proteins were produced. Targets for mutagenesis were mostly selected on the basis o f the similarity between beta-toxin and alpha-toxin from Staphylococcu s aureus, a pore-forming toxin. Mutations of two amino acids affected the lethal dose in mice. Both residues have counterparts in the membra ne binding region of alpha-toxin. Alteration of the single cysteine re sidue did not affect protein function, contrary to previous suggestion s. (C) 1998 Federation of European Microbiological Societies. Publishe d by Elsevier Science B.V.