Solution structure of agelenin, an insecticidal peptide isolated from the spider Agelena opulenta, and its structural similarities to insect-specific calcium channel inhibitors

Agelenin, isolated from the Agelenidae spider Agelena opulenta, is a peptide composed of 35 amino acids. We determined the three-dimensional structure of agelenin using two-dimensional NMR spectroscopy. The structure is composed of a short antiparallel β-sheet and four β-turns, which are stabilized by three disulfide bonds. Agelenin has characteristic residues, Phe9, Ser28 and Arg33, which are arranged similarly to the pharmacophore of the insect channel inhibitor, ω-atracotoxin-Hv1a. These observations suggest that agelenin and ω-atracotoxin-Hv1a bind to insect calcium channels in a similar manner. We also suggest that another mode of action may operate in the channel inhibition by ω-agatoxin-IVA and ω-atracotoxin-Hv2a.