Structural Characterisation of Predicted Helical Regions in the Chironex fleckeri CfTX-1 Toxin.

Athena Andreosso,Norelle Daly,Michael Smout,Paramjit Bansal,David Wilson,Jamie Seymour

doi:10.3390/md16060201

Athena Andreosso, Norelle Daly + Show 4 more

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https://doi.org/10.3390/md16060201

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Abstract

The Australian jellyfish Chironex fleckeri, belongs to a family of cubozoan jellyfish known for their potent venoms. CfTX-1 and -2 are two highly abundant toxins in the venom, but there is no structural data available for these proteins. Structural information on toxins is integral to the understanding of the mechanism of these toxins and the development of an effective treatment. Two regions of CfTX-1 have been predicted to have helical structures that are involved with the mechanism of action. Here we have synthesized peptides corresponding to these regions and analyzed their structures using NMR spectroscopy. The peptide corresponding to the predicted N-terminal amphiphilic helix appears unstructured in aqueous solution. This lack of structure concurs with structural disorder predicted for this region of the protein using the Protein DisOrder prediction System PrDOS. Conversely, a peptide corresponding to a predicted transmembrane region is very hydrophobic, insoluble in aqueous solution and predicted to be structured by PrDOS. In the presence of SDS-micelles both peptides have well-defined helical structures showing that a membrane mimicking environment stabilizes the structures of both peptides and supports the prediction of the transmembrane region in CfTX-1. This is the first study to experimentally analyze the structure of regions of a C. fleckeri protein.

Highlights

The Australian box jellyfish, Chironex fleckeri, belongs to a family of cubozoan jellyfish that are known for their potent venoms [1,2,3]
This study provides the first experimental data regarding the structures of peptides derived from the putatively pore forming C. fleckeri toxin, CfTX-1
The region predicted to form an amphiphilic α-helix in CfTX-1 appears to be disordered in aqueous solution based on the chemical shift analysis of CfTX-122–47

Summary

Introduction

The Australian box jellyfish, Chironex fleckeri, belongs to a family of cubozoan jellyfish that are known for their potent venoms [1,2,3]. In the northern half of the Australian continent, C. fleckeri envenomations, ranging from mostly minor to occasionally life threatening, occur frequently, during October to June [4]. Envenomation symptoms include immediate severe pain, cutaneous inflammation, cardiovascular distress and dysfunction, loss of consciousness and potential cardiac arrest [5,6]. The venom of C. fleckeri is of particular clinical relevance as rapid cardiovascular collapse followed by death can occur within minutes [6,7]. The majority of the venom toxins are proteins with a variety of distinct functions. These protein toxins include CfTX-like proteins, a variety of enzymes such as proteases and oxido-reductases, CRISP-toxins, an alpha-macroglobulin and a protease inhibitor [8]

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