Snake venom toxins--II. The primary structures of cytotoxin homologues S3C2 and S4C8 from Aspidelaps scutatus (shield or shield-nose snake) venom.

1. Cytotoxin homologues S3C2 and S4C8 from Aspidelaps scutatus were purified by gel filtration and ion exchange chromatography. 2. They consist of 63 amino acids including eight half-cystines. The toxicities of S3C2 and S4C8 were determined and LD50 values of 6.6 and 9.4 micrograms/g mouse were, respectively, found. 3. The complete primary structures of toxins S3C2 and S4C8 have been determined. The two toxins resemble the cytotoxin type toxins and in the cytotoxin homologues the ten structurally invariant amino acids of the neurotoxins and the cytotoxins are conserved.