Covalently attached peptide dendrimers can enhance binding affinity and functional activity. Homogenous di- and tetravalent dendrimers incorporating the á7-nicotinic receptor blocker á-conotoxin ImI (á-ImI) with polyethylene glycol spacers were designed and synthesized via a copper-catalyzed azide-alkyne cycloaddition of azide-modified á-ImI to an alkyne-modified polylysine dendron. NMR and CD structural analysis confirmed that each á-ImI moiety in the dendrimers had the same 3D structure as native á-ImI. The binding of the á-ImI dendrimers to binding protein Ac-AChBP was measured by surface plasmon resonance and revealed enhanced affinity. Quantitative electrophysiology showed that á-ImI dendrimers had ?100-fold enhanced potency at há7 nAChRs (IC50 = 4 nM) compared to native á-ImI (IC50 = 440 nM). In contrast, no significant potency enhancement was observed at heteromeric há3â2 and há9á10 nAChRs. These findings indicate that multimeric ligands can significantly enhance conotoxin potency and selectivity at homomeric nicotinic ion channels.
Binding Sites Cell Line