Journal
FEBS LETTERS
Volume 470, Issue 3, Pages 293-299Publisher
WILEY
DOI: 10.1016/S0014-5793(00)01339-9
Keywords
funnel-web spider toxin; delta-atracotoxin; sodium channel; scorpion toxin
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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 ex-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. (C) 2000 Federation of European Biochemical Societies.
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