HCN1 also known as BCNG1 belongs to the potassium channel HCN family. HCN1 is a hyperpolarization-activated cation channel that contributes to the native pacemaker currents in heart and neurons. HCN1 protein can homodimerize or heterodimerize with other pore-forming subunits to form a potassium channel. This channel may act as a receptor for sour tastes. It hyperpolarization-activated ion channel exhibiting weak selectivity for potassium over sodium ions. HCN1 contributes to the native pacemaker currents in heart (If) and in neurons (Ih). It is activated by cAMP, and at 10-100 times higher concentrations, also by cGMP. HCN1 may mediate responses to sour stimuli.