Journal Article

The amino acid sequence of bothropstoxin-II, an Asp-49 myotoxin from Bothrops jararacussu (Jararacucu) venom with low phospholipase A sub(2) activity

Landucci, E T, Oliveira, B, Novello, J C, Giglio, J R, Marangoni, S, Pereira, M F, Cintra, ACO

1998

Overview

The complete amino acid sequence of bothropstoxin-II (BthTX-II), a myotoxin isolated from Bothrops jararacussu snake venom, is reported. The results show that BthTX-II is an Asp-49 phospholipase A sub(2) (PLA sub(2))-like protein composed of a single polypeptide chain of 120 amino acid residues (M sub(r) = 13,976), containing one methionine and 14 half-cystines. Despite a high degree of homology with other PLA sub(2)'s and the presence of the strategic residues known to compose the Ca super(2+)-binding loop, namely Tyr-28, Gly-30, Gly-32, and especially Asp-49, besides His-48, Tyr-52, and Asp-99, all of them directly or indirectly involved in catalysis, BthTX-II revealed a very low PLA sub(2) activity when assayed on egg yolk phosphatidylcholine. We attribute this low catalytic activity to the existence of extra mutations, e.g., Trp-5 for Phe-5, which points to the need of considering other strategic positions, since only Lys-49 PLA sub(2)'s have been considered to be devoid of this enzymatic activity.