User:Lisa1235858/Versutoxin

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Delta atracotoxin Hv1 (δ-ACTX-Hv1a, Versutoxin, or Versutotoxin) is a neurotoxic component found in the venom of the Australian funnel web spider (Atrax robustus).

Delta atracotoxin Hv1 can result in fatality in primates by downregulating the inactivation of voltage gated sodium ion channels found in motor neurons.

The structure of versutoxin contains a central beta region with a inhibitor cystine knot (ICK), commonly found in other neurotoxic polypeptides, but not found in sea anemone or alpha-scorpion toxins despite their similar effects in terms of sodium channel modulation.

Nomenclature
In 1997, Jamie I. Fletcher and his research associates introduced new nomenclature for classifying Australian funnel web spider toxins. They suggested replacing the trivial name 'versutoxin' with delta-atracotoxin-Hv1 instead. The delta represents the main biological activity of the neurotoxin; inhibiting sodium channels.

History
Although over 40 different species of funnel web spiders are known, the male Atrax robustus is known to have the most human fatalities, prior to the introduction of antivenom in 1981.

Structure
Delta atracotoxin Hv1 is a tightly folded polypeptide that contains a chain of 42 animo acid residues and has the chemical formula C206H318N58O60S9. The animo acid sequence of delta atracotoxin Hv1 is: C A K K R N W C G K T E D C C C P M K C V Y A W Y N E Q G S C Q S T I S A L W K K C

Three Dimensional Structure
The tertiary structure of δ-ACTX-Hv1 contains a core β region that is made up of the residues Cys1–Cys8, Cys14–Val21, and Ser30–Ser33, with Tyr22–Gly29 protruding outwards. The β region has a three-stranded antiparallel β sheet comprising Asn6–Trp7 (β1), Met18–Val21 (β2), and Ser30–Ser33 (β3). The C-terminal end of the short β1 is held in place by a bifurcated hydrogen bond between the Cys8 amide proton and the carbonyl oxygens of the two residues preceding β strand 3 (Gln28 and Gly29). The β region also contains type II β turns at Lys3–Asn6 and Cys15–Met18 with a rare cis peptide bond at Cys16–Met 17. The nonpolar C-terminal 310 helix formed by Ile35–Lys41, bordering Lys40 and Lys41 and connecting to β region with a disulphide bond next to a β turn. The β region contains hydrophobic cysteine sidechains bordered by a lysine sidechain.Three of the four disulphide bonds form the ICK.