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:
“Any translation which intends to perform a transmitting function cannot transmit anything but information—hence, something inessential. This is the hallmark of bad translations.”
—Walter Benjamin (1892–1940)
“The fact remains that the human being in early childhood learns to consider one or the other aspect of bodily function as evil, shameful, or unsafe. There is not a culture which does not use a combination of these devils to develop, by way of counterpoint, its own style of faith, pride, certainty, and initiative.”
—Erik H. Erikson (1904–1994)
“Science has fulfilled her function when she has ascertained and enunciated truth.”
—Thomas Henry Huxley (1825–95)