Toxins from cone snails: properties, applications and biotechnological production

Abstract

Cone snails are marine predators that use venoms to immobilize their prey. The venoms of these mollusks contain a cocktail of peptides that mainly target different voltage- and ligand-gated ion channels. Typically, conopeptides consist of ten to 30 amino acids but conopeptides with more than 60 amino acids have also been described. Due to their extraordinary pharmacological properties, conopeptides gained increasing interest in recent years. There are several conopeptides used in clinical trials and one peptide has received approval for the treatment of pain. Accordingly, there is an increasing need for the production of these peptides. So far, most individual conopeptides are synthesized using solid phase peptide synthesis. Here, we describe that at least some of these peptides can be obtained using prokaryotic or eukaryotic expression systems. This opens the possibility for biotechnological production of also larger amounts of long chain conopeptides for the use of these peptides in research and medical applications.

Fig. 1

Conus purpurascens hunting a clown fish. The snail stings the fish with a harpoon like tooth, which is hollow and barbed and held at the tip of the proboscis. Upon venom injection (upper right) the fish is immobilized within less than a few seconds (lower left) and engulfed by the snail (lower right; originally from Terlau et al. 1996)

Fig. 2

Sequence and structure of K⁺ channel binding conotoxins. Despite a different cysteine backbone and different structures all the three peptides κ-PVIIA (pdb code: 1AV3); κM-RIIIK (*) and Conk-S1 (pdb code: 2CA7) interact with Shaker K⁺ channels by occluding the ion channel pore (Shon et al. ; Jacobsen et al. ; Ferber et al. ; Al-Sabi et al. ; Bayrhuber et al. ; Verdier et al. 2005). O 4-hydroxyproline; Z pyroglutamate; # denotes an amidated C-terminal amino acid. * Structural coordinates obtained from T. Carlomagno

Fig. 3

Ways to biotechnological production of disulfide-rich peptides. Solid phase peptide synthesis of disulfide-rich peptides requires subsequent folding of the peptide fragment in the presence of oxygen. Addition of low-molecular-weight thiols in oxidized and reduced form (oxido-shuffling reagents) to the folding solution can help to increase the yield of correctly folded peptide. Recombinant peptide production can result in insoluble protein (inclusion bodies) or soluble protein. From inclusion bodies folding in the presence of oxido-shuffling reagents can be successful