Cloning and purification of α-neurotoxins from king cobra ( Ophiophagus hannah)

Abstract

Thirteen complete and three partial cDNA sequences were cloned from the constructed king cobra ( Ophiophagus hannah) venom gland cDNA library. Phylogenetic analysis of nucleotide sequences of king cobra with those from other snake venoms revealed that obtained cDNAs are highly homologous to snake venom α-neurotoxins. Alignment of deduced mature peptide sequences of the obtained clones with those of other reported α-neurotoxins from the king cobra venom indicates that our obtained 16 clones belong to long-chain neurotoxins (seven), short-chain neurotoxins (seven), weak toxin (one) and variant (one), respectively. Up to now, two out of 16 newly cloned king cobra α-neurotoxins have identical amino acid sequences with CM-11 and Oh-6A/6B, which have been characterized from the same venom. Furthermore, five long-chain α-neurotoxins and two short-chain α-neurotoxins were purified from crude venom and their N-terminal amino acid sequences were determined. The cDNAs encoding the putative precursors of the purified native peptide were also determined based on the N-terminal amino acid sequencing. The purified α-neurotoxins showed different lethal activities on mice.