Toxin Name ω-agatoxin-Aa2a (N-terminal fragment)
Source Species Agelenopsis  aperta (Western grass spider)
Toxin Group Agatoxin
Description The sequence shown is a 28-residue N-terminal fragment. MALDI analysis combined with cloning of the toxin precursor has been used to determine that the 11-kDa mature toxin comprises 92 residues (Adams, 2004), but the complete sequence has not yet been published or submitted to any databases. The toxin is present at low concentration in A. aperta venom (15 μM).

ω-AGTX-Aa2a is insecticidal and inhibits neuromuscular transmission in both vertebrates and insects by blocking voltage-gated calcium (Cav) channels on presynaptic terminals. As for the unrelated toxin ω-AGTX-Aa1a from the venom of the same spider, ω-AGTX-Aa2a reduces quantum content at fly neuromuscular junctions and blocks calcium action potentials in insect central neurons. Each toxin alone only blocks a portion of the synaptic potential but together they abolish virtually all neurotransmitter release in an additive fashion. This suggests that the two toxins target different classes of Cav channels. ω-AGTX-Aa1a most likely blocks Cav1 channels based on its ability to block dihydropyridine-sensitive L-type barium currents in rat dorsal root ganglion (DRG) neurons and its inability to inhibit the binding of the Cav2.2 blocker ω-conotoxin GVIA to chick synaptosomal membranes. In contrast, nanomolar concentrations of ω-AGTX-Aa2a strongly inhibit ω-conotoxin GVIA binding, and hence the toxin most likely targets primarily Cav2.2 channels.
Discovered 1989
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This toxin last updated on Aug 20, 2010

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