Synthesis, Structural and Pharmacological Characterizations of CIC, a Novel α-Conotoxin with an Extended N-Terminal Tail

Abstract

Cone snails are venomous marine predators that rely on fast-acting venom to subdue their prey and defend against aggressors. The conotoxins produced in the venom gland are small disulfide-rich peptides with high affinity and selectivity for their pharmacological targets. A dominant group comprises α-conotoxins, targeting nicotinic acetylcholine receptors. Here, we report on the synthesis, structure determination and biological activity of a novel α-conotoxin, CIC, found in the predatory venom of the piscivorous species Conus catus and its truncated mutant Δ-CIC. CIC is a 4/7 α-conotoxin with an unusual extended N-terminal tail. High-resolution NMR spectroscopy shows a major influence of the N-terminal tail on the apparent rigidity of the three-dimensional structure of CIC compared to the more flexible Δ-CIC. Surprisingly, this effect on the structure does not alter the biological activity, since both peptides selectively inhibit α3β2 and α6/α3β2β3 nAChRs with almost identical sub- to low micromolar inhibition constants. Our results suggest that the N-terminal part of α-conotoxins can accommodate chemical modifications without affecting their pharmacology.

Understanding the Role of Self-Assembly and Interaction with Biological Membranes of Short Cationic Lipopeptides in the Effective Design of New Antibiotics

“…The freeze-dried peptide powder not only consists of the peptide but also includes non-peptidic components such as water, traces of other solvents, counterions and salts. In turn, the net peptide content is related to the actual weight percent of the peptide in the sample and falls in the range of 60–90 % in most cases, depending on the purity, sequence and method of synthesis and purification [ 49 , 50 , 51 , 52 ]. With a very low initial concentration of the peptide used in ITC experiments, the difference in the net peptide content can have a great impact on the stoichiometry.…”

Marine natural products

“…657 Both the α4/7-conotoxin CIC (venom of C. catus ) and an N -terminus truncated mutant selectively inhibit α3β2 and α6/α3β2β3 nAChR, suggesting the N -terminal tail can accommodate structural changes without any effect on observed receptor activity. 658 α4/7-Conotoxin LvIF, a 16-residue synthesised peptide based upon genomic DNA clone data derived from C. lividis also exhibits potent inhibition of rα3β2 and rα6/α3β2β3 nAChR's. 659 The 17-residue peptide α4/7-conotoxin Lv1d ( C. lividis ) demonstrates in vivo analgesic effects.…”

Marine Origin Ligands of Nicotinic Receptors: Low Molecular Compounds, Peptides and Proteins for Fundamental Research and Practical Applications

“…Surprisingly, the natural toxin showed very low affinity for both subtypes of the muscle receptor (IC 50 11–13 μM), unlike some of its synthetic analogues with mutation at 9, 10 and 11 positions ( Table 2 ). Another “classic” muscle nAChR-acting α-conotoxin, CIA, was identified in the transcriptome of the C. catus venom duct, and then synthesized together with α4/7-conotoxins CIB [ 139 ] and CIC [ 143 ]. In addition to the nanomolar affinity towards the muscle receptor subtype, CIA unexpectedly showed a micromolar affinity for α3β2 nAChR, while the main target for CIB was the α3β2 nAChR receptor [ 139 ] ( Table 2 ).…”

“…In addition to the nanomolar affinity towards the muscle receptor subtype, CIA unexpectedly showed a micromolar affinity for α3β2 nAChR, while the main target for CIB was the α3β2 nAChR receptor [ 139 ] ( Table 2 ). The structural feature of the α4/7-conotoxin CIC was the presence of an elongated N-terminus, but it did not affect the main activity of this peptide towards α3β2 and α6/α3β2β3 nAChRs [ 143 ].…”