Introduction of α-bungarotoxin binding site into extracellular domains of HCN4 channels

摘要: Hyperpolarization-activated cyclic-nucleotide gated (HCN) channels are the molecular determinants of the If/Ih current that controls pacemaking activity in cardiac and neuronal cells. Unique among the voltage-gated ion channel superfamily, HCN channels are modulated by the direct binding of cAMP to their cytoplasmic cyclic nucleotide binding domain (CNBD). We have recently shown that aD and aE helices of the CNBD, which fold only in the cAMP-bound conformation, lock the CNBD in a high affinity state by interacting and stabilizing the upstream aC helix via both hydrophilic and hydrophobic interactions. Previously to the discovery of the aD and aE helices, we and others have shown that in the cAMP-unbound conformation, the C-helix of CNBD is also the target of Trip8b, the brain-specific auxiliary subunit of HCN channels that decreases the affinity for cAMP. By inspecting the structures, we have observed …