Identification of Conomarphin Variants in the Conus eburneus Venom and the Effect of Sequence and PTM Variations on Conomarphin Conformations.

Corazon Ericka Mae M Itang,Eizadora T Yu,Ricky B Nellas,Yu-Ju Chen,Jokent T Gaza,Dan Jethro M Masacupan,Dessa Camille R Batoctoy

doi:10.3390/md18100503

Abstract

Marine cone snails belonging to the Conidae family make use of neuroactive peptides in their venom to capture prey. Here we report the proteome profile of the venom duct of Conus eburneus, a cone snail belonging to the Tesseliconus clade. Through tandem mass spectrometry and database searching against the C. eburneus transcriptome and the ConoServer database, we identified 24 unique conopeptide sequences in the venom duct. The majority of these peptides belong to the T and M gene superfamilies and are disulfide-bonded, with cysteine frameworks V, XIV, VI/VII, and III being the most abundant. All seven of the Cys-free peptides are conomarphin variants belonging to the M superfamily that eluted out as dominant peaks in the chromatogram. These conomarphins vary not only in amino acid residues in select positions along the backbone but also have one or more post-translational modifications (PTMs) such as proline hydroxylation, C-term amidation, and γ-carboxylation of glutamic acid. Using molecular dynamics simulations, the conomarphin variants were predicted to predominantly have hairpin-like or elongated structures in acidic pH. These two structures were found to have significant differences in electrostatic properties and the inclusion of PTMs seems to complement this disparity. The presence of polar PTMs (hydroxyproline and γ-carboxyglutamic acid) also appear to stabilize hydrogen bond networks in these conformations. Furthermore, these predicted structures are pH sensitive, becoming more spherical and compact at higher pH. The subtle conformational variations observed here might play an important role in the selection and binding of the peptides to their molecular targets.

Highlights

The venom of marine cone snails is a goldmine for neuroactive peptides known as conopeptides.Current estimates report that cone snail venom consists of hundreds to thousands of conopeptides that act on a wide range of pharmacological targets such as ion channels and G protein-coupled receptors [1,2,3]
A total of 711 unique mass components ranging from ~400 Da to ~10,000 Da were identified from the native venom extract of Conus eburneus
A unimodal distribution of these mass components was observed, wherein approximately 90.0% of the detected components have masses below 4000 Da. This highlights the short nature of conopeptides and is consistent with previous findings that reported a conopeptide length range from 10 to 45 amino acids (~1 to 5 kDa) [14,18]

Summary

Introduction

The venom of marine cone snails is a goldmine for neuroactive peptides known as conopeptides. Current estimates report that cone snail venom consists of hundreds to thousands of conopeptides that act on a wide range of pharmacological targets such as ion channels and G protein-coupled receptors [1,2,3]. For this reason, these conopeptides are being explored as lead compounds for drug discovery and development [3,4,5,6].

Methods

Results

Conclusion