Myotoxin II from Bothrops asper (Terciopelo) Venom Is a Lysine-49 PhospholipaseA2

摘要

A basic, dimeric myotoxic protein, myotoxin II, purified from Bothrops aspervenom has a similar molecular weight and is immunologically cross-reactive with antibodies raised to previously isolate B. asper phospholipases A2, except that it shows only 0.1% of the phospholipase activity against L-a-phosphatidylcholine in the presence of Triton X-100. Its 121 amino acid sequence, determined by automated Edman Degradation, clearly identifies it as a Lys-49 phospholipase A2. Key amino acid differences between myotoxin II and phospholipase active proteins in the Ca2+ binding loop region include Lys for Asp-49, Asn for Tyr-38, and Leu for Gly-32. The latter substitution has not previously been seen in Lys-49 proteins.