Preparation of Sea Anemone Peptide Toxin Ap-TxI and Its Insecticidal Activity

[Objectives]This study was conducted to synthesize sea anemone peptide toxin Ap-TxI and investigate its insecticidal activity. [Methods] The sea anemone linear peptide toxin Ap-TxI was synthesized by the solid-phase peptide synthesis(SPPS), and six cysteines were oxidized to form three disulfide bonds by a three-step directional oxidation method. Then, purification by high performance liquid chromatography(HPLC) and mass spectrometry identification were performed. Finally, the insect cytotoxicity and insecticidal activity of Ap-TxI were studied by the MTT method and insect injection method. [Results] The oxidized peptide Ap-TxI with three disulfide bonds in natural configuration was successfully synthesized by the SPPS method, and its purity was >90% by HPLC analysis. The results of the MTT method showed that Ap-TxI was active on the growth of insect cells sf9, with a half effective dose of 0.2 nM;and the results of the mealworm injection test showed that the polypeptide Ap-TxI had high insecticidal activity with a median lethal dose of 11.7 nM. [Conclusions] The sea anemone peptide toxin Ap-TxI with high insecticidal effect was obtained, laying a foundation for the development of new, efficient and safe biological insecticides.

General mechanism of spider toxin family I acting on sodium channel Nav1.7

Various peptide toxins in animal venom inhibit voltage-gated sodium ion channel Nav1.7, including Nav-targeting spider toxin(NaSpTx) Family I. Toxins in NaSpTx Family I share a similar structure, i.e., Nterminal, loops 1–4, and C-terminal. Here, we used Mu-theraphotoxin-Ca2a(Ca2a), a peptide isolated from Cyriopagopus albostriatus, as a template to investigate the general properties of toxins in NaSpTx Family I. The toxins interacted with the cell membrane prior to binding to Nav1.7 via similar hydrophobic residues. Residues in loop 1, loop 4,and the C-terminal primarily interacted with the S3–S4 linker of domain II, especially basic amino acids binding to E818. We also identified the critical role of loop 2 in Ca2a regarding its affinity to Nav1.7.Our results provide further evidence that NaSpTx Family I toxins share similar structures and mechanisms of binding to Nav1.7.

Discovery, structure,and chemical synthesis of disulfide-rich peptide toxins and their analogs

Recently, medicinal peptide molecules are of great interest to many international pharmaceutical companies, mainly because of their relatively lower research costs, shorter research cycles, and the greater likelihood of being drugs, when compared with traditional small molecules. Due to the great variety in molecule structures and the diverse biological functions, disulfide-rich peptide toxins have become a shining molecular library for the development of polypeptide drugs. In view of the increasing amount of related publications, here we summarize the discovery, structural elucidation and chemical synthesis of disulfide-rich peptide toxins and their analogs.