Agelenin (toxicologically named as U1-agatoxin-Aop1a[1] and abbreviated as U1-AGTX-Aop1a) is a neurotoxic peptide isolated from the venom of the spider Allagelena opulenta which consists of 35 amino acids.
[2] Agelenin consists of a polypeptide chain of 35 amino acid residues.
[2] It has a short anti-parallel β-sheet connected by three disulfide bonds and four β-turns that form the compact core structure.
The three amino acid residues that are thought to be essential for the inhibiting activity of agelenin are Phe9, Ser28 and Arg33.
[3] In preparations of neuromuscular junctions of lobsters agelenin causes a non-reversible paralysis due to the suppression of excitatory postsynaptic potentials, presumably by inhibition of the presynaptic calcium influx.