Light-gated ion channel

Light-gated ion channel

Light-gated ion channels are a group of transmembrane proteins that form ion channels; pores which open or close in response to light. Most light-gated ion channels have been synthesized in the laboratory for study, though one naturally occurring example, Channelrhodopsin, is currently known. [ [http://pubs.acs.org/cgi-bin/abstract.cgi/bichaw/2006/45/i51/abs/bi0618058.html|"Engineering Light-Gated Ion Channels"] — "Biochemistry", 45 (51), 15129 -15141, 2006] There are, however, many known photoreceptor proteins, which act in a similar manner to light-gated ion channels but are generally G protein coupled receptors and not actually gated ion channels.

Synthetic Purpose

Other types of gated ion channels, ligand-gated and voltage-gated, have been synthesized with a light-gated component in an attempt to better understand their nature and properties. By the addition of a light-gated section, the kinetics and mechanisms of operation can be studied in depth. For example, the addition of a light-gated component allows for the introduction of many highly similar ligands to be introduced to the binding site of a ligand-gated ion channel to assist in the determination of the mechanism.
In 1980, the first ion channel to be adapted for study with a light-gated mechanism was the nicotinic acetylcholine receptor. [ [http://www.jgp.org/cgi/content/abstract/75/2/207|"A covalently bound photoisomerizable agonist. Comparison with reversibly bound agonists at electrophorus electroplaques"] — The Journal of General Physiology, Vol 75, 207-232] This receptor was well-known at the time, and so was aptly suited to adaptation, and allowed for a study of the kinetics as not allowed before.

Mechanism

Light-gated ion channels function in a similar manner to other gated ion channels. When exposed to a certain stimulus, a conformational change occurs in the transmembrane proteins, which constitute the pore. This conformational change then opens or closes the ion channel, allowing for the flow of ions according to their electrochemical gradient. In the specific case of light-gated ion channels, the transmembrane proteins are usually coupled with a molecule that acts as a photoswitch. Retinal is a good example of a molecular photoswitch and is found in the naturally occurring Channelrhodopsins. The photoswitch absorbs a specific photon and changes its conformation, which, in turn, changes the conformation of the transmembrane proteins opening or closing the pore through which ions flow.

Examples

Examples of light-gated ion channels occur in both natural and synthetic environments. These include:

Naturally Occurring

*Channelrhodopsins were the first discovered family of light-gated ion channels.
**Channelrhodopsin-1
**Channelrhodopsin-2

Synthetically Adapted

*nicotinic acetylcholine receptor was the first ion channel to be synthetically adapted with a light-gated mechanism.
*Many other fully synthetic, light-gated channels have produced as well. [ [http://dx.doi.org/10.1016/S0040-4020(01)86704-1|"Photosensitive artificial membranes based on azobenzene and spirobenzopyran derivatives"] — TetrahedronVolume 50, Issue 14, 4 April 1994, Pages 4039-4070] [ [http://pubs.acs.org/cgi-bin/abstract.cgi/langd5/2004/20/i17/abs/la048942v.html|"Lipid-Mediated Light Activation of a Mechanosensitive Channel of Large Conductance"] — "Langmuir", 20 (17), 6985 -6987, 2004]

ee also

Channelrhodopsin
Ion channels
Voltage-gated ion channel
Ligand-gated ion channel
Photoreceptor protein
Optogenetics

References


Wikimedia Foundation. 2010.

Игры ⚽ Поможем написать курсовую

Look at other dictionaries:

  • Cyclic nucleotide-gated ion channel — Cyclic nucleotide gated (CNG) ion channels are ion channels that function in response to the binding of cyclic nucleotides. CNG channels are nonselective cation channels that are found in the membranes of various types of cells. Signal… …   Wikipedia

  • Ion channel — Not to be confused with: Ion Television or Ion implantation. Schematic diagram of an ion channel. 1 channel domains (typically four per channel), 2 outer vestibule, 3 selectivity filter, 4 diameter of selectivity filter, 5 phosphorylation site, 6 …   Wikipedia

  • Voltage-dependent calcium channel — Voltage dependent calcium channels (VDCC) are a group of voltage gated ion channels found in excitable cells (e.g., muscle, glial cells, neurons, etc.) with a permeability to the ion Ca2+.[1][2] These channels are slightly permeable to sodium… …   Wikipedia

  • Channelrhodopsin — Channelrhodopsins are a subfamily of opsin proteins that function as light gated ion channels.[1] They serve as sensory photoreceptors in unicellular green algae, controlling phototaxis, i.e. movement in response to light. Expressed in cells of… …   Wikipedia

  • Rhodopsin — Rhodopsin, also known as visual purple, is a pigment of the retina that is responsible for both the formation of the photoreceptor cells and the first events in the perception of light. Rhodopsins belong to the G protein coupled receptor family… …   Wikipedia

  • Action potential — In physiology, an action potential is a short lasting event in which the electrical membrane potential of a cell rapidly rises and falls, following a consistent trajectory. Action potentials occur in several types of animal cells, called… …   Wikipedia

  • Membrane transport protein — A membrane transport protein (or simply transporter) is a membrane protein[1] involved in the movement of ions, small molecules, or macromolecules, such as another protein across a biological membrane. Transport proteins are integral membrane… …   Wikipedia

  • Chloride potassium symporter — The chloride potassium symporter is a membrane transport protein that is present in the S3 segment of the renal proximal tubule[1]. It functions in renal chloride reabsorption to transport chloride across the basolateral membrane.[1] They can… …   Wikipedia

  • Chloride hydroxyl exchanger — A chloride hydroxyl exchanger is a purported membrane transport protein, responsible for the exchange of chloride and hydroxyl in the renal proximal tubule, functioning in renal chloride reabsorption. However, little is known about the protein… …   Wikipedia

  • Cell surface receptor — The seven transmembrane α helix structure of a G protein coupled receptor Cell surface receptors (membrane receptors, transmembrane receptors) are specialized integral membrane proteins that take part in communication between the cell and the… …   Wikipedia

Share the article and excerpts

Direct link
… Do a right-click on the link above
and select “Copy Link”