Purification and amino acid sequence of the insecticidal neurotoxin Tx4(6-1) from the venom of the 'armed' spider Phoneutria nigriventer (Keys).

An insecticidal peptide referred to as Tx4(6-1) was purified from the venom of the spider Phoneutria nigriventer by a combination of gel filtration, reverse-phase fast liquid chromatography on Pep-RPC, reverse-phase high performance liquid chromatography (HPLC) on Vydac C18 and ion-exchange HPLC on cationic columns. Tx4(6-1) is highly toxic to house flies. At levels of 0.5 ng/house fly it caused excitatory symptoms immediately after intrathoracical injection. However, in mice injections of 0.03 mg of the toxin intracerebroventricularly resulted in no apparent symptoms of intoxication. These results demonstrate that Tx4(6-1) of P. nigriventer has no toxicity for mice, and suggest that it is a specific anti-insect toxin. The mol. wt (5244.6) and purity of the toxin were determined by desorption mass spectroscopy. The complete amino acid sequence of this toxin was established by direct automated Edman degradation and manual 4-N,N'-dimethylaminoazobenzene-4'isothiocyanate/phenyl-isothiocyanate microsequence analyses of peptides obtained from digests with various proteases. The protein contains 48 amino acids including 10 Cys and 6 Lys. The N-terminal and C-terminal residues were Cys. The Tx4(6-1) sequence differs from that of previously characterized neurotoxins found in the same and other venom spiders, but exhibited sequence similarities in the location of the Cys residues.