Neurotoxic Peptides in the Multicomponent Venom of the Spider Cupiennius Salei Part I. Primary Structure of Neurotoxic Peptides in Relation to their Biological Function

Abstract

Beside other components, spider venom contains neurotoxically acting peptides which predominantly target a variety of different ion channels within the spider's prey. From the multicomponent venom of Cupiennius salei 13 toxic peptides (CSTX-1 – CSTX-13) were purified by a combination of gel filtration, cation-exchange chromatography, and reverse-phase HPLC. The amino acid sequence of two important neurotoxic peptides, CSTX-1 (74 residues, 8352.6 Da) and CSTX-9 (68 residues, 7530.9 Da), as well as CSTX-2a (61 residues, 6865.7 Da), a truncated form of CSTX-1, were determined by Edman degradation. Sequence comparison of CSTX-1 with CSTX-9 revealed an identity of 53% as well as identical positions of all eight cysteine residues. CSTX-1 and CSTX-9 share the same disulphide bridge pattern linking Cys₁–Cys₄, Cys₂–Cys₅, Cys₃–Cys₈ and Cys₆–Cys_7. This disulphide bridge pattern is also found in other spider toxins such as agatoxins and curtatoxins. CSTX-1 and CSTX-9 belong to the family of the ion channel toxins containing the inhibitor cystine knot structural motif with the consensus sequence: CX_3-7CX_3-10CX_0-7CX_1-8CX_4-20C. CSTX-2a and CSTX-9, lacking the lysine-rich C-terminal tail of CSTX-1, exhibit a much lower toxicity for Drosophila melanogaster than CSTX-1, providing good evidence for the direct involvement of this lysine-rich C-terminal tail in the toxicity of CSTX-1.