Abstract
We isolated two proteins, ET-1 and ET-2, from the sporangial extracts of Clostridium perfringens type A. Both proteins had some properties in common with the well-known C. perfringens enterotoxin. ET-1 and ET-2 behaved as single and distinct entities in anion exchange chromatography and disk gel electrophoresis. ET-2 was the more anionic protein since it eluted more slowly from the anion exchange column and migrated faster toward the anode in polyacrylamide disk gel electrophoresis (pH 8.5, native gels). Additionally, in this electrophoretic system ET-2 was not distinguishable from the enterotoxin. The amino acid compositions of ET-1 and ET-2 were similar but differed in a few amino acid residues. The values for both proteins were also similar to the published reports of others for the enterotoxin. Both ET-1 and ET-2 showed lines of identity in agar gel double immunodiffusion against anti-enterotoxin antiserum. Both ET-1 and ET-2 were toxic for rat hepatocytes in primary monolayer culture as determined by accelerated exodus of L-[14C]glucose from preloaded cells and by the rapid uptake of 45Ca2+ after exposure to the proteins. In this regard, ET-1 and ET-2 appeared to be identical in mechanism of action to what has been regarded in the literature as "the" C. perfringens enterotoxin. Interestingly, ET-2 was 3 to 10 times more toxic on a weight basis than ET-1 was.