Novel Conopeptides of Largely Unexplored Indo Pacific Conus sp.

Abstract

Cone snails are predatory creatures using venom as a weapon for prey capture and defense. Since this venom is neurotoxic, the venom gland is considered as an enormous collection of pharmacologically interesting compounds having a broad spectrum of targets. As such, cone snail peptides represent an interesting treasure for drug development. Here, we report five novel peptides isolated from the venom of Conus longurionis, Conus asiaticus and Conus australis. Lo6/7a and Lo6/7b were retrieved from C. longurionis and have a cysteine framework VI/VII. Lo6/7b has an exceptional amino acid sequence because no similar conopeptide has been described to date (similarity percentage <50%). A third peptide, Asi3a from C. asiaticus, has a typical framework III Cys arrangement, classifying the peptide in the M-superfamily. Asi14a, another peptide of C. asiaticus, belongs to framework XIV peptides and has a unique amino acid sequence. Finally, AusB is a novel conopeptide from C. australis. The peptide has only one disulfide bond, but is structurally very different as compared to other disulfide-poor peptides. The peptides were screened on nAChRs, NaV and KV channels depending on their cysteine framework and proposed classification. No targets could be attributed to the peptides, pointing to novel functionalities. Moreover, in the quest of identifying novel pharmacological targets, the peptides were tested for antagonistic activity against a broad panel of Gram-negative and Gram-positive bacteria, as well as two yeast strains.

Marine natural products

“…New examples of conotoxins puried from venom of Conus species molluscs were reported: PiVIIA, 689 a 25-mer producing signicant increases in Ca 2+ currents (C. princeps); Im10A, 690 an 11-mer bearing four cysteine residues (C. imperialis); Lo6/7a and Lo6/7b, 691 24-and 27-mers, respectively, which are examples of framework VI/VII conotoxins from C. longurionis; Asi3a a framework III 15-mer and Asi14a a framework XIV 17-mer, both 691 from C. asiaticus; and AusB, an unsual 18-mer example bearing only one disulde bond, isolated from C. australis. 691 Screening of a library of synthetic conotoxin variants has identied a peptide that upon further structure-activity relationship tuning, led to analogues that were potent and selective agonists of the k-opioid receptor. 692 Large quantities of the nAChR antagonist, a-conotoxin LvIA, have been prepared via an E. coli recombinant expression system.…”

Discovery Methodology of Novel Conotoxins from Conus Species

“…The purified conotoxins are subjected to de novo sequencing through Edman degradation [ 58 , 59 , 60 , 61 , 62 , 63 , 64 , 65 , 66 , 67 , 68 , 69 , 70 , 71 , 72 , 73 , 74 , 75 , 76 , 77 , 78 , 79 , 80 , 81 , 82 , 83 , 84 , 85 , 86 , 87 ] or MS sequencing [ 81 , 88 , 89 , 90 ] after sequential disulfide bond reduction, hydrosulphonyl alkylation, and enzymolysis, which make sequencing process much easier. PTMs are assigned with the aid of MS techniques [ 59 , 65 , 66 , 69 , 70 , 71 , 75 , 76 , 77 , 78 , 80 , 83 , 89 , 90 , 91 , 92 ]. The targeted conotoxins are then chemically synthesized through SPPS, following the subsequent oxidative...…”

In the picture: disulfide-poor conopeptides, a class of pharmacologically interesting compounds

“…As such, the peptide was electrophysiologically screened against a panel of Na V s, K V s and nAChRs as expressed heterologously in Xenopus laevis oocytes. In addition, a broad screening was performed against a collection of microorganisms (29 gram-negative bacteria, ten gram-positive bacteria and two yeast strains) [84]. Unfortunately, the real target of this peptide remains to be revealed.…”