Isolation of delta-missulenatoxin-Mb1a, the major vertebrate-active spider delta-toxin from the venom of Missulena bradleyi (Actinopodidae).
The present study describes the isolation and pharmacological characterisation of the neurotoxin delta-missulenatoxin-Mb1a (delta-MSTX-Mb1a) from the venom of the male Australian eastern mouse spider, Missulena bradleyi. This toxin was isolated using reverse-phase high-performance liquid chromatography and was subsequently shown to cause an increase in resting tension, muscle fasciculation and a decrease in indirect twitch tension in a chick biventer cervicis nerve-muscle bioassay. Interestingly, these effects were neutralised by antivenom raised against the venom of the Sydney funnel-web spider Atrax robustus. Subsequent whole-cell patch-clamp electrophysiology on rat dorsal root ganglion neurones revealed that delta-MSTX-Mb1a caused a reduction in peak tetrodotoxin (TTX)-sensitive sodium current, a slowing of sodium current inactivation and a hyperpolarising shift in the voltage at half-maximal activation. In addition, delta-MSTX-Mb1a failed to affect TTX-resistant sodium currents. Subsequent Edman degradation revealed a 42-residue peptide with unusual N- and C-terminal cysteines and a cysteine triplet (Cys(14-16)). This toxin was highly homologous to a family of delta-atracotoxins (delta-ACTX) from Australian funnel-web spiders including conservation of all eight cysteine residues. In addition to actions on sodium channel gating and kinetics to delta-ACTX, delta-MSTX-Mb1a caused significant insect toxicity at doses up to 2000 pmol/g. Delta-MSTX-Mb1a therefore provides evidence of a highly conserved spider delta-toxin from a phylogenetically distinct spider family that has not undergone significant modification.
Gunning
Simon J
SJ
Department of Health Sciences, University of Technology, Sydney, NSW 2007, Australia.
Chong
Youmie
Y
Khalife
Ali A
AA
Hains
Peter G
PG
Broady
Kevin W
KW
Nicholson
Graham M
GM
D000595:Amino Acid Sequence; D000818:Animals; D002645:Chickens; D004594:Electrophysiology; D066298:In Vitro Techniques; D008297:Male; D008969:Molecular Sequence Data; D018482:Muscle, Skeletal / Q000187:drug effects / Q000294:innervation; D009498:Neurotoxins / Q000302:isolation & purification* / Q000494:pharmacology; D010525:Peripheral Nerves / Q000187:drug effects; D016415:Sequence Alignment; D020539:Sequence Analysis, Protein; D015222:Sodium Channels / Q000187:drug effects; D013111:Spider Venoms / Q000737:chemistry*; D013112:Spiders
D009498:Neurotoxins; D015222:Sodium Channels; D013111:Spider Venoms; C406870:delta-atracotoxin-HV1