Antimycobacterial Activity: A New Pharmacological Target for Conotoxins Found in the First Reported Conotoxin from Conasprella ximenes

Abstract

Mycobacterium tuberculosis is the etiological agent of tuberculosis, an airborne infectious disease that is a leading cause of human morbidity and mortality worldwide. We report here the first conotoxin that is able to inhibit the growth of M. tuberculosis at a concentration similar to that of two other drugs that are currently used in clinics. Furthermore, it is also the first conopeptide that has been isolated from the venom of Conasprella ximenes. The venom gland transcriptome of C. ximenes was sequenced to construct a database with 24,284 non-redundant transcripts. The conopeptide was purified from the venom using reverse phase high performance liquid chromatography (RP-HPLC) and was analyzed using electrospray ionization-mass spectrometry (ESI-MS/MS). No automatic identification above the identity threshold with 1% of the false discovery rate was obtained; however, a 10-amino-acid sequence tag, manually extracted from the MS/MS spectra, allowed for the identification of a conotoxin in the transcriptome database. Electron transfer higher energy collision dissociation (EThcD) fragmentation of the native conotoxin confirmed the N-terminal sequence (1–14), while LC-MS/MS analysis of the tryptic digest of the reduced and S-alkylated conotoxin confirmed the C-terminal region (15–36). The expected and experimental molecular masses corresponded, within sub-ppm mass error. The 37-mer peptide (MW 4109.69 Da), containing eight cysteine residues, was named I1_xm11a, according to the current nomenclature for this type of molecule.

The Diversified O-Superfamily in Californiconus californicus Presents a Conotoxin with Antimycobacterial Activity

“…While most use of conotoxins has been focused on pain management [16]; other cysteine-rich proteins/peptides isolated from the snake, scorpion, and spider venoms have shown strong antimicrobial potency against bacterial, fungal and yeast infections and are a promising source for therapeutic agents [17]. Before the discovery of I1_xm11a, a native peptide with anti-TB activity [8], an effective antimicrobial activity from conopeptides was shown for Lo6/7a conotoxin from C. longurion [18], as well as with the engineering of ω-conotoxin MVIIA into cyclic analogs [19].…”

“…Conotoxin research in C. californicus has exhibited various promising peptides that could be scaled up in biomedical research, like a transcription of pro-inflammatory cytokines, anti-parasitic effect and apoptosis activation in lung cancer [5,6,7]. In general, anti-bacterial activity in conotoxins has not been fully related to their potential, until recently with the first report associating conotoxins capable of inhibiting the growth of a reference strain of Mtb [8]. Notably, M. tuberculosis exhibits a complex membrane that has allowed it to evolve and remain as a major health problem affecting a third of the population worldwide.…”

A Potential Golden Age to Come—Current Tools, Recent Use Cases, and Future Avenues for De Novo Sequencing in Proteomics

“…were able to discover multiple isoforms of crotapotin in the venom of the South American rattlesnake ( Crotalus durissus terrificus ) using de novo sequencing . Further recent studies have applied the technique other organisms, including snails, ants, scorpions, and spiders . Mainly PEAKS and manual de novo sequencing were used to evaluate the MS data in these studies.…”

“…Conotoxins are oligopeptides found in cone snails and have been the subject of multiple studies. The work of Figueroa‐Montiel et al . surveys the utilization of conotoxins with antimycobacterial activity as a potential Mycobacterium tuberculosis treatment.…”

Chemical Synthesis and NMR Solution Structure of Conotoxin GXIA from Conus geographus

“…The spacing of these Cys residues (C–C–CC–CC–C–C) gives it an ‘XI’ framework, while GXIA is a member of the I superfamily and part of the I 3 subfamily, based on its signal peptide sequence [ 17 ]. To date, the biological activity for only a few members of the I superfamily have been reported, including; κ-BtX ( C. betulinus ) an up-modulator of BK channels, ViTx ( C. virgo ) an inhibitor of K V 1.1 and 1.3 channels, ι-RXIA ( C. radiates ) an agonist for Na V 1.2, 1.6 and 1.7 channels, and Xm11a ( Conasprella ximenes ) an antimycobacterial peptide [ 18 , 19 , 20 , 21 ]. Based on a search of the Conoserver database and relevant literature, the only member of the I-superfamily with a reported structure found is ι-RXIA, where the majority of loops and termini differ in length, and the sequence identity to GXIA is minimal, apart from the cysteines [ 14 , 22 ].…”