Characterization of myotoxin a from the venom of prairie rattlesnake (Crotalus viridis viridis).

A previously unknown polypeptide myotoxin, designated myotoxin a, was isolated for the first time from prairie rattlesnake (Crotalus viridis viridis) venom. Electrophoretic homogeneity of myotoxin a was shown in beta-alanine disc gel polyacrylamide gel electrophoresis and in isoelectric focusing gel electrophoresis. Molecular weight and isoelectric point estimates of 4100 and 9.6 were obtained by gel filtration and isoelectric focusing gel electrophoresis, respectively. Amino acid composition showed a total of 39 amino acid residues, with 10 lysine residues and two disulfide bridges. When the two disulfide brides were reduced and alkylated, the myotoxic activity was abolished, indicating that the disulfide bridges of myotoxin a are essential for its biological activity. The loss of the biological activity is probably due to a marked change in secondary structure. The circular dichroic spectrum indicates that the chemically modified, inactive myotoxin exhibits typical random-coil conformation.