Functional duality and structural uniqueness of the depressant insect-selective neurotoxins

摘要: Depressant insect-selective neurotoxins derived from scorpion venoms (a) induce in blowfly larvae a short, transient phase of contraction similar to that induced by excitatory followed prolonged flaccid paralysis and (b) displace toxins their binding sites on insect neuronal membranes. The present study was undertaken order examine the basis these similarities comparing primary structures neuromuscular effects depressant toxins. A new toxin (LqhIT2) purified venom Israeli yellow scorpion. this prepupal housefly preparation mimic intact animal; i.e., brief period repetitive bursts junction potentials is suppression amplitude finally block transmission. Loose patch clamp recordings indicate activity has presynaptic origin motor nerve closely resembles effect AaIT. final synaptic attributed membrane depolarization, which results an increase spontaneous transmitter release; not toxin. amino acid sequences three were determined automatic Edman degradation. comprise well-defined family polypeptides with high degree sequence conservation. This group differs considerably structure toxin, it shares identical or related sites, two groups affect sodium conductance mammals. opposing pharmacological are discussed light above data.