Single-Molecule Resolution of Multivalent Ligand Binding in Pacemaker Channels

Abstract

Periodicity of electrical oscillations in brain and heart is controlled by pacemaker channels whose activity is also modulated by cAMP binding. Efforts to investigate the binding mechanisms in ligand activated membrane receptors have been hampered by the inability to directly measure single ligand association at physiological concentrations and therefore rely on either ensemble approaches or downstream ligand-induced conformational change. Here, we overcome these challenges using single-molecule fluorescence microscopy in nanophotonic waveguides to directly resolve the early binding dynamics of individual ligands to multimeric cyclic nucleotide-gated ion channels.