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
beta-sheet and four
beta-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, omega-atracotoxin-Hv1a. These observations suggest that agelenin and omega-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 omega-agatoxin-IVA and omega-atracotoxin-Hv2a.
