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. It is an antagonist of the presynaptic P-type calcium channel in insects.
Agelenin is an insecticidal toxin of the venom of the species Allagelena opulenta.[1] It was first discovered in 1990.[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]
The structure of agelenin is similar to the structure of ICK toxins like ω-Aga-IVA and ω-ACTXHv1a in that they all consist of three disulfide bonds with the same bonding pattern. An important difference between agelenin and ω-Aga-IVA and ω-ACTXHv1a is that ω-Aga-IVA and ω-ACTXHv1a have functional C-terminal tails.[3]
Agelenin belongs to toxin group of agatoxins.[1] The amino acid structure of agelenin is Gly-Gly-Cys-Leu-Pro-His-Asn-Arg-Phe-Cys-Asn-Ala-Leu-Ser-Gly-Pro-Arg-Cys-Cys-Ser-Gly-Leu-Lys-Cys-Lys-Glu-Leu-Ser-Ile-Trp-Asp-Ser-Arg-Cys-Leu (GGCLPHNRFCNALSGPRCCSGLKCKELSIWDSRCL).[3]
Agelenin is directed against P-subtype calcium channels in insects.[4]
Agelenin is not toxic in mammals, but has a PD50 of 291 pmol/g in crickets where it causes rapid, reversible paralysis. 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.[2]