Studies on epsilon-prototoxin of Clostridium perfringens type D. Physicochemical and chemical properties of epsilon-prototoxin.

epsilon-Prototoxin of clostridium perfringens type D consists of one polypeptide chain of 311 amino acids with the following composition: Asp52 Thr31 Ser25 Glu28 Pro12 Gly17 Ala14 Val28 Met5 Ile15 Leu18 Tyr17 Phe8 Lys31 His2 Arg5 Tyr2. It has no free cysteine but contains one blocked cysteine. The N-terminal as well as the C-terminal residue is lysine. The ultracentrifuge pattern gave one single boundary having S020,w = 2.15 S and Do20,w = 5.56-10(-7) cm2/s. Calculation of the molecular weight from D020,w and S020,w gave a value of 34 250. The molecular weight determined from sedimentation equilibrium using ultraviolet optics gave a value of 33 000 +/- 1000. On the other hand molecular weights calculated from a calibrated Sephadex G-100 column in borate buffer was 25 000 and that in sodium phosphate, ionic strength 0.2, was 27 500. This discrepancy between values obtained in the ultracentrifuge and by gel filtration is attributed to adsorption of epsilon-prototoxin by Sephadex.