Add time:08/29/2019         Source:sciencedirect.com

Background: versutoxin (cas 114264-83-4) (δ-ACTX-Hv1) is the major component of the venom of the Australian Blue Mountains funnel web spider, Hadronyche versuta. δ-ACTX-Hv1 produces potentially fatal neurotoxic symptoms in primates by slowing the inactivation of voltage-gated sodium channels; δ-ACTX-Hv1 is therefore a useful tool for studying sodium channel function. We have determined the three-dimensional structure of δ-ACTX-Hv1 as the first step towards understanding the molecular basis of its interaction with these channels.Results: The solution structure of δ-ACTX-Hv1, determined using NMR spectroscopy, comprises a core β region containing a triple-stranded antiparallel β sheet, a thumb-like extension protruding from the β region and a C-terminal 310 helix that is appended to the β domain by virtue of a disulphide bond. The β region contains a cystine knot motif similar to that seen in other neurotoxic polypeptides. The structure shows homology with μ-agatoxin-I, a spider toxin that also modifies the inactivation kinetics of vertebrate voltage-gated sodium channels. More surprisingly, δ-ACTX-Hv1 shows both sequence and structural homology with gurmarin, a plant polypeptide. This similarity leads us to suggest that the sweet-taste suppression elicited by gurmarin may result from an interaction with one of the downstream ion channels involved in sweet-taste transduction.Conclusions: δ-ACTX-Hv1 shows no structural homology with either sea anemone or α-scorpion toxins, both of which also modify the inactivation kinetics of voltage-gated sodium channels by interacting with channel recognition site 3. However, we have shown that δ-ACTX-Hv1 contains charged residues that are topologically related to those implicated in the binding of sea anemone and α-scorpion toxins to mammalian voltage-gated sodium channels, suggesting similarities in their mode of interaction with these channels.

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