Structural and Functional Elucidation of Peptide Ts11 Shows Evidence of a Novel Subfamily of Scorpion Venom Toxins.

Caroline Cremonez,Mohitosh Maiti,Piet Herdewijn,Adriano Pimenta,Eveline Lescrinier,Juliana Cassoli,Maria De Lima,Etienne Waelkens,Steve Peigneur,Alexandre Dutra,Eliane Arantes,Jan Tytgat

doi:10.3390/toxins8100288

Abstract

To date, several families of peptide toxins specifically interacting with ion channels in scorpion venom have been described. One of these families comprise peptide toxins (called KTxs), known to modulate potassium channels. Thus far, 202 KTxs have been reported, belonging to several subfamilies of KTxs (called α, β, γ, κ, δ, and λ-KTxs). Here we report on a previously described orphan toxin from Tityus serrulatus venom, named Ts11. We carried out an in-depth structure-function analysis combining 3D structure elucidation of Ts11 and electrophysiological characterization of the toxin. The Ts11 structure is highlighted by an Inhibitor Cystine Knot (ICK) type scaffold, completely devoid of the classical secondary structure elements (α-helix and/or β-strand). This has, to the best of our knowledge, never been described before for scorpion toxins and therefore represents a novel, 6th type of structural fold for these scorpion peptides. On the basis of their preferred interaction with voltage-gated K channels, as compared to all the other targets tested, it can be postulated that Ts11 is the first member of a new subfamily, designated as ε-KTx.

Highlights

Scorpion venom is a rich source of potassium channel blocking toxins (KTxs), which have been used in the structural and functional characterization of various voltage-gated potassium (Kv) channels [1].Toxins 2016, 8, 288; doi:10.3390/toxins8100288 www.mdpi.com/journal/toxinsKv channels have received much attention because they are widespread in almost all tissue, and due to the high diversity of Kv channels expressed in mammalian cells
Ts11 was isolated using a combination of cation exchange chromatography of T. serrulatus venom [7], followed by reversed-phase fast protein liquid chromatography (RP-FPLC) of fraction
Ts12 was isolated through reversed-phase high-performance liquid chromatography (RP-HPLC) of T. serrulatus venom on a C18 column (Supplemental Materials Figure S1A)

Summary

Introduction

Kv channels have received much attention because they are widespread in almost all tissue, and due to the high diversity of Kv channels expressed in mammalian cells. Most of them contain a common core topology comprised of one or two short α-helices connected to a triple-stranded antiparallel β-sheet stabilized by three or four disulfide bonds [3]. For both classes of toxins—those acting on potassium channels (KTxs) and those acting on sodium channels (NaTxs)—the range of different folds is merely the variability of CSα/β and CSα/α topology [1]

Results

Discussion

Conclusion