Amino acid sequences of a heterodimeric neurotoxin from the venom of the false horned viper (Pseudocerastes fieldi)

Abstract The main toxic component of the venom of the false horned viper, Pseudocerastes fieldi , is a heterodimeric neurotoxin composed of a basic subunit, Cb II, and one of two acidic subunits, either Cb Iα or Cb Iβ. The nontoxic acidic subunit increases the toxicity of the basic subunit. Both subunits have phospholipase A 2 (PLA 2 ) amino acid sequences. Cb Iα and Cb Iβ themselves are inactive towards phosphatidylcholine and when complexed with Cb II promote a delay in the onset of phospholipase activity of Cb II. Cb Iα and Cb Iβ do hydrolyze the synthetic substrate, 3-octanoyloxy-4-nitrobenzoic acid, but at 2 . This suggests that these amino acid changes in the conserved regions are important for the structure and function of the heterodimeric proteins.