Isolation and characterization of α-conotoxin LsIA with potent activity at nicotinic acetylcholine receptors

A new alpha-conotoxin LsIA was isolated from the crude venom of Conus limpusi using assay-guided RP-HPLC fractionation. Synthetic LsIA was a potent antagonist of alpha 3 beta 2, alpha 3 alpha 5 beta 2 and alpha 7 nAChRs, with half-maximal inhibitory concentrations of 10, 31 and 10 nM, respectively. The structure of LsIA determined by NMR spectroscopy comprised a characteristic disulfide bond-stabilized alpha-helical structure and disordered N-terminal region. Potency reductions of up to 9-fold were observed for N-terminally truncated analogues of LsIA at alpha 7 and alpha 3 beta 2 nAChRs, whereas C-terminal carboxylation enhanced potency 3-fold at alpha 3 beta 2 nAChRs but reduced potency 3-fold at alpha 7 nAChRs. This study gives further insight into alpha-conotoxin pharmacology and the molecular basis of nAChR selectivity, highlighting the influence of N-terminal residues and C-terminal amidation on conotoxin pharmacology. (C) 2013 Published by Elsevier Inc.