Cloning and cDNA sequence analysis of Lys(49) and Asp(49) basic phospholipase A(2) myotoxin isoforms from Bothrops asper

Snake venom myotoxic phospholipases A(2) contribute to much of the tissue d amage observed during envenomation by Bothrops asper, the major cause of sn ake bites in Central America. Several myotoxic PLA(2)s have been identified , but their mechanism of myotoxicity is still unclear. To aid in the molecu lar characterization of these venom toxins, the complete open reading frame s encoding two Lys(49) and one Asp(49) basic PLA(2) myotoxins From the Cent ral American snake B, asper (terciopelo) were obtained by cDNA cloning from venom gland poly-adenylated RNA. The amino acid sequence deduced from the myotoxins II and III open reading frames corresponded in each case to one o f the reported amino acid sequence isoforms. The sequence of a new myotoxin IV-like sequence (MT-IVa) contains conservative Val --> Leu(18) and Ala -- > Val(23) substitutions when compared with the reported N-terminus of the n ative myotoxin IV, suggesting minor isoform variations among specimens of a single species. Sequence alignment studies indicated significant (>75% seq uence identity) identities with other crotalid venom Lys(49) PLA(2)s, parti cularly bothropstoxin I/Ia isoforms of B. jararacussu and myotoxin II of B. asper. (C) 2001 Elsevier Science Ltd. All rights reserved.