Snake Venom. The Amino-Acid Sequence of the Subunits of two Reduced and S-Carboxymethylated Proteins (C8S2and C9S3) fromDendroaspis angusticepsVenom

Abstract

Two proteins (C8S2 and C9S3) were purified from D. angusticeps venom. Whereas protein C8S2 comprises 124 amino acid residues, protein C9S3 contains 125 and each includes 16 half-cystines. After reduction and S-carboxymethylation of the proteins, the subunits contained 62-63 residues including 8 half-cystine residues. The complete sequences of the subunits were elucidated. The sequences of the subunits of protein C8S2 and C9S3 are homologous to those of protein S2C4 from D. jamesoni kaimosae. In all the subunits 1 of the structurally invariant amino acids, Tyr25, was replaced by Ph or Asn and the Cys66 occurs in position 57. All the subunits apparently contain only 2 of the 5 functionally invariant residues of the neurotoxins, i.e., Lys27 and Trp29. Mixtures of proteins S2C4, C8S2, C9S3 and D. angusticeps-type proteins showed a marked synergistic toxic effect in mice.