Acetylcholine Promotes Binding of α‐Conotoxin MII at α₃β₂ Nicotinic Acetylcholine Receptors

Abstract

α-Conotoxin MII (α-CTxMII) is a 16 amino acid peptide with the sequence GCCSNPVCHLEHSNLC containing disulfide bonds between Cys2-Cys8 and Cys3-Cys16. This peptide, isolated from the venom of the marine cone snail Conus magus, is a potent and selective antagonist of neuronal nicotinic acetylcholine receptors (nAChRs). To evaluate the impact of channel-ligand interactions on ligand binding affinity, homology models of the heteropentameric α3β2-nAChR were constructed. The models were created in MODELLER using crystal structures of the Torpedo marmorata-nAChR (Tm-nAChR, PDB ID: 2BG9) and the Aplysia californica-acetylcholine binding protein (Ac-AChBP, PDB ID: 2BR8) as templates for the α3 and β2 subunit isoforms derived from rat neuronal nAChR primary amino acid sequences. Molecular docking calculations were performed with AutoDock to evaluate interactions of the heteropentameric nAChR homology models with the ligands acetylcholine (ACh) and α-CTxMII. The nAChR homology models described here bind ACh with commensurate binding energies to previously reported systems, and identify critical interactions that facilitate both ACh and α-CTxMII ligand binding. The docking calculations revealed an increased binding affinity of the α3β2-nAChR for α-CTxMII with ACh bound to the receptor, which was confirmed through two-electrode voltage clamp experiments on oocytes from Xenopus laevis. These findings provide insights into the inhibition and mechanism of electrostatically driven antagonist properties of the α-CTxMIIs on nAChRs.

Marine natural products

“…A recent report describes the use of a Lys 4 solubilising C-terminus tag to enable the synthesis and Na V subtype selectivity of three previously reported C. consors g-conotoxins, g-CnVIB, g-CnVIC and g-CnVID. 826 Further studies have reported on the structure and activity of dicarba analogues of a-RgIA, 827 the inuence of disulde connectivity on structure and bioactivity of a-TxIA, 828 the inuence of acetylcholine to affect the binding of a-MII at nAChRs, 829 the neuronal target selectivity of the Conus textile T-superfamily peptide TxVC, 830 and the Ca 2+ -activated K + (BK) channel selectivity of the unusual M superfamily conotoxin Vt3.1. 831 11 Tunicates (ascidians)…”

GAMPMS: Genetic algorithm managed peptide mutant screening

“…It is known to potently and selectively block ‐nAChR isoforms . Due to the importance of nAChRs in the progression of neurodegenerative diseases, libraries of mutants were screened for binding affinity toward the pentameric homology model of the isoform of rat neuronal nAChR . This system is reasonably well understood and was selected so that we could focus on evaluating the efficacy of GAMPMS.…”

Molecular design and docking analysis of the inhibitory activities of some α_substituted acetamido-N-benzylacetamide as anticonvulsant agents

“…The highest binding affinity (the lowest docking energy) score was chosen to explore the binding mode of the docked compound in the GABAAT enzyme using PyRx program. For the analysis of the docking calculations, 9 conformers were considered for each ligand-target complex, and the resulting docking clusters were calculated with a 2.0 Å root mean squared deviation (RMSD) tolerance on the heavy atoms [16]. The 3D molecular interaction models of the complex (involving hydrogen bonding and hydrophobic interactions) were displayed using the pymol visualization software.…”