A cyclic nucleotide-gated (CNG) ion channel is any ion channel that opens in the presence of cyclic nucleotides.
The channels are gated by a chemical ligand (the cyclic nucleotide), but they are more similar in structure to the family of voltage-gated ion channels
than to the ligand gated
ones. In fact, the cyclic nucleotide-gated channels often have positively- or negatively-charged areas that may respond to changes in membrane potential
. The purpose and function of these charged areas are not yet fully understood.
Cyclic nucleotide-gated channels are particularly important in several systems:
"Cyclic nucleotide gated channel alpha" subunits include
Other examples include the following "hyperpolarization
-activated cyclic nucleotide-gated potassium channels
" (HCN channels