Toxin Name μ-cyrtautoxin-As1a
Source Species Apomastus  schlingeri (Trap-door spider)
Toxin Group Cyrtautoxin
Description Insecticidal toxin that is lethal to larva of the tobacco hornworm Manduca sexta within 24 hours of injection but is much less potent against the beet armyworm Spodoptera exigua. μ-CUTX-As1a blocks insect voltage-gated sodium channels. Channel block is voltage-independent insofar as it occurs without significant alteration in the voltage-dependence of channel activation or steady-state inactivation. Thus, μ-CUTX-As1a appears to be a pore blocker that plugs the outer vestibule of insect voltage-gated sodium channels. μ-CUTX-As1a is also a weak blocker of insect voltage-gated calcium channels.

Structurally, μ-CUTX-As1a is an atypical knottin peptide; three of the disulfide bridges form a classical inhibitor cystine knot motif while the fourth disulfide (Cys26-Cys31) acts as a molecular staple that restricts the flexibility of an unusually large β hairpin loop.

Discovered 1992
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This toxin last updated on May 01, 2015

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