Isolation and pharmacological characterisation of delta-atracotoxin-Hv1b, a vertebrate-selective sodium channel toxin.
delta-Atracotoxins (delta-ACTXs) are peptide toxins isolated from the venom of Australian funnel-web spiders that slow sodium current inactivation in a similar manner to scorpion alpha-toxins. We have isolated and determined the amino acid sequence of a novel delta-ACTX, designated delta-ACTX-Hv1b, from the venom of the funnel-web spider Hadronyche versuta. This 42 residue toxin shows 67% sequence identity with delta-ACTX-Hv1a previously isolated from the same spider. Under whole-cell voltage-clamp conditions, the toxin had no effect on tetrodotoxin (TTX)-resistant sodium currents in rat dorsal root ganglion neurones but exerted a concentration-dependent reduction in peak TTX-sensitive sodium current amplitude accompanied by a slowing of sodium current inactivation similar to other delta-ACTXs. However, delta-ACTX-Hv1b is approximately 15-30-fold less potent than other delta-ACTXs and is remarkable for its complete lack of insecticidal activity. Thus, the sequence differences between delta-ACTX-Hv1a and -Hv1b provide key insights into the residues that are critical for targeting of these toxins to vertebrate and invertebrate sodium channels.
Szeto
T H
TH
Department of Biochemistry, University of Connecticut Health Center, Farmington, CT 06032, USA.
Birinyi-Strachan
L C
LC
Smith
R
R
Connor
M
M
Christie
M J
MJ
King
G F
GF
Nicholson
G M
GM
D000595:Amino Acid Sequence; D000818:Animals; D002851:Chromatography, High Pressure Liquid; D004305:Dose-Response Relationship, Drug; D004553:Electric Conductivity; D005260:Female; D005727:Ganglia, Spinal / Q000166:cytology / Q000187:drug effects; D006135:Gryllidae / Q000187:drug effects; D007306:Insecticides / Q000737:chemistry; D015640:Ion Channel Gating / Q000187:drug effects; D008297:Male; D008969:Molecular Sequence Data; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D016415:Sequence Alignment; D020539:Sequence Analysis, Protein; D012964:Sodium / Q000378:metabolism; D026941:Sodium Channel Blockers; D015222:Sodium Channels / Q000378:metabolism; D013045:Species Specificity; D013111:Spider Venoms / Q000737:chemistry* / Q000302:isolation & purification* / Q000494:pharmacology*; D013112:Spiders / Q000737:chemistry*; D013379:Substrate Specificity; D013779:Tetrodotoxin / Q000494:pharmacology; D014118:Toxins, Biological / Q000737:chemistry / Q000302:isolation & purification* / Q000494:pharmacology*
D007306:Insecticides; D026941:Sodium Channel Blockers; D015222:Sodium Channels; D013111:Spider Venoms; D014118:Toxins, Biological; C406870:delta-atracotoxin-HV1; D013779:Tetrodotoxin; D012964:Sodium