Function
CNG channels have important functions in signal transduction in retinal photoreceptors and olfactory receptor neurons. They are directly activated by cyclic nucleotides, and approximately 4 cyclic nucleotides are needed to activate each channel. CNG channels are nonselective and allow many alkali ions to flow into or out of a cell expressing CNG channels on its membrane. This flow of ions can result in either depolarization or hyperpolarization. CNG channels can be activated by cAMP or cGMP exclusively, or sometimes by a combination of both cNMPs, and some channels are more selective than others. Even though the activity of these channels show little voltage dependence, they are still considered voltage-dependent channels. Calcium, calmodulin, and phosphorylation modulate the opening of CNG channels.
The main role of CNG channels is sensory transduction in various tissues. Many studies have shown CNG channels in rod and cone photoreceptors, and they have also been found in the brain, the heart, the kidneys, and gonads.
CNG channel homologs in Caenorhabditis elegans, Drosophila melanogaster, and Limulus polyphemus have unknown functions. Studies have shown homologs in C. elegans might have functions in chemosensation.
Color blindness and retinal degeneration result when CNG channels have mutations. Mutations specifically in the subunits A and B result in complete and incomplete achromatopsia.
Read more about this topic: Cyclic Nucleotide-gated Ion Channel
Famous quotes containing the word function:
“For me being a poet is a job rather than an activity. I feel I have a function in society, neither more nor less meaningful than any other simple job. I feel it is part of my work to make poetry more accessible to people who have had their rights withdrawn from them.”
—Jeni Couzyn (b. 1942)
“The function of comedy is to dispel ... unconsciousness by turning the searchlight of the keenest moral and intellectual analysis right on to it.”
—George Bernard Shaw (1856–1950)
“Think of the tools in a tool-box: there is a hammer, pliers, a saw, a screwdriver, a rule, a glue-pot, nails and screws.—The function of words are as diverse as the functions of these objects.”
—Ludwig Wittgenstein (1889–1951)