CNG and HCN channels: two peas, one pod.
Cyclic nucleotide-activated ion channels play a fundamental role in a variety of physiological processes. By opening in response to intracellular cyclic nucleotides, they translate changes in concentrations of signaling molecules to changes in membrane potential. These channels belong to two families: the cyclic nucleotide-gated (CNG) channels and the hyperpolarization-activated cyclic nucleotide-modulated (HCN) channels. The two families exhibit high sequence similarity and belong to the superfamily of voltage-gated potassium channels. Whereas HCN channels are activated by voltage and CNG channels are virtually voltage independent, both channels are activated by cyclic nucleotide binding. Furthermore, the channels are thought to have similar channel structures, leading to similar mechanisms of activation by cyclic nucleotides. However, although these channels are structurally and behaviorally similar, they have evolved to perform distinct physiological functions. This review describes the physiological roles and biophysical behavior of CNG and HCN channels. We focus on how similarities in structure and activation mechanisms result in common biophysical models, allowing CNG and HCN channels to be viewed as a single genre.
Craven
Kimberley B
KB
Department of Physiology and Biophysics, University of Washington, Seattle, WA 98195, USA. kcraven@u.washington.edu
Zagotta
William N
WN
D000595:Amino Acid Sequence; D000818:Animals; D055592:Biophysical Phenomena; D001703:Biophysics; D054815:Cyclic Nucleotide-Gated Cation Channels; D004594:Electrophysiology; D006801:Humans; D064428:Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels; D015640:Ion Channel Gating / Q000235:genetics / Q000502:physiology*; D007473:Ion Channels / Q000235:genetics / Q000502:physiology*; D008969:Molecular Sequence Data; D009712:Nucleotides, Cyclic / Q000502:physiology*; D015221:Potassium Channels
D054815:Cyclic Nucleotide-Gated Cation Channels; D064428:Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels; D007473:Ion Channels; D009712:Nucleotides, Cyclic; D015221:Potassium Channels