Sandbox Reserved 1451: Difference between revisions

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== Function ==

Rhodopsin performs two functions. One function is to bind retinal. Rhodopsin is a protein that is essential for vision, especially in dim light. The photoreceptors in the retina that contain rhodopsin are rods. Rhodopsin is attached to 11-cis retinal which becomes excited by a photon of light and isomerizes to become all-trans conformation<ref name="Article4">PMID:29042326</ref>. This excitation activates rhodopsin and leads to depolarizing of neurons. The depolarizing of neurons is how the image is transmitted to the brain<ref name="Article2">“RHO Gene - Genetics Home Reference.” U.S. National Library of Medicine, National Institutes of Health, 11AD, ghr.nlm.nih.gov/gene/RHO#.</ref>. Another function is to function as a G protein-coupled receptor. When rhodopsin is activated by light the protein couples with the G protein transducin which is the first step in the signal cascade<ref name="Article4">PMID:29042326</ref>. Rhodopsin must undergo several conformational changes before being able to bind transducin<ref name="Article3">PMID:21352497</ref>. Rhodopsin is initially converted to metarhodopsin II which is the active form of rhodopsin. Once the protein is active then metarhodopsin binds the G-protein tranducin and the GDP is exchanged for GTP. The G protein subunits dissociate and causes a decrease in cytosolic cGMP. The decrease in cGMP also causes the closing of calcium channels. When calcium concentrations drop the photoreceptors become hyperpolarized and this ensures the action potential is sent onward toward the brain<ref name="Article5">PMID:12402507</ref>. Photoreceptors are unable to be immediately restimulated, rhodopsin kinase phosphorylates the protein on serine and threonine residues which leads to the binding of arrestin. Arrestin prevents rhodopsin from interacting with tranducin again, thus preventing restimulation of the protein. Arrestin is released from the protein via phospotase A which dephosphorylates rhodopsin<ref name="Article5">PMID:12402507</ref>.

Rhodopsin performs two functions. One function is to bind retinal. Rhodopsin is a protein that is essential for vision, especially in dim light. The photoreceptors in the retina that contain rhodopsin are rods. Rhodopsin is attached to 11-cis retinal which becomes excited by a photon of light and isomerizes to become all-trans conformation<ref name="Article4">PMID:29042326</ref>. This excitation activates rhodopsin and leads to depolarizing of neurons. The depolarizing of neurons is how the image is transmitted to the brain<ref name="Article2">“RHO Gene - Genetics Home Reference.” U.S. National Library of Medicine, National Institutes of Health, 11AD, ghr.nlm.nih.gov/gene/RHO#.</ref>. Another function of rhodopsin is to function as a G protein-coupled receptor. When rhodopsin is activated by light the protein couples with the G protein transducin which is the first step in the signal cascade<ref name="Article4">PMID:29042326</ref>. Rhodopsin must undergo several conformational changes before being able to bind transducin<ref name="Article3">PMID:21352497</ref>. Rhodopsin is initially converted to metarhodopsin II which is the active form of rhodopsin. Once the protein is active then metarhodopsin binds the G-protein tranducin and the GDP is exchanged for GTP. The G protein subunits dissociate and causes a decrease in cytosolic cGMP. The decrease in cGMP also causes the closing of calcium channels. When calcium concentrations drop the photoreceptors become hyperpolarized and this ensures the action potential is sent onward toward the brain<ref name="Article5">PMID:12402507</ref>. Photoreceptors are unable to be immediately restimulated, rhodopsin kinase phosphorylates the protein on serine and threonine residues which leads to the binding of arrestin. Arrestin prevents rhodopsin from interacting with tranducin again, thus preventing restimulation of the protein. Arrestin is released from the protein via phospotase A which dephosphorylates rhodopsin<ref name="Article5">PMID:12402507</ref>.

== Disease ==

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<scene name='77/778331/Rhodopsin_no_ligand/1'>Rhodopsin protein</scene> Fully functional rhodopsin has the typical GPCR structure of a seven transmembrane helical bundle with the N-terminus on the interior of the rods and the C-terminus in the cytoplasm. The N-terminus is located near the extracellular loops and ends of the transmembrane protein. There are hydrogen bonding between the transmembrane sections and the extracellular loops that are involved in the activation of rhodopsin when a photon is received. The N-terminus is thought to play a role in orientation of the extracellular loops<ref name="Article4">PMID:29042326</ref>. Transmembrane domain 1 and 2 play a role in stabilizing the protein and giving the protein functionality<ref name="Article3">PMID:21352497</ref>. Rhodopsin has two components: opsin (a membrane-bound polypeptide) and 11-cis-retinal (a chromophore that is bound to opsin via a protonated Schiff-base)<ref name="Article5">PMID:12402507</ref>.

<scene name='77/778331/Rhodopsin_ligand/1'>11-cis retinal</scene> 11-cis retinal ~~is the ligand~~, a molecule that is derived from vitamin A, is necessary for rhodopsin function. The ligand performs an inverse agonist suppressing activity on the photon receptor and is associated with the protein via protonated Schiff-bases linked to a lysine reside on the seventh domain<ref name="Article3">PMID:21352497</ref>. A negative agonist means the ligand, when present in the binding pocket of the protein, inhibits the receptor activity<ref name="Article5">PMID:12402507</ref>. The isomerization of cis to trans causes the protein complex to relax which allows for binding of transducin and the signal cascade to progress<ref name="Article3">PMID:21352497</ref>.

<scene name='77/778331/Rhodopsin_ligand/1'>11-cis retinal</scene> 11-cis retinal, a molecule that is derived from vitamin A, is necessary for rhodopsin function. The ligand performs an inverse agonist suppressing activity on the photon receptor and is associated with the protein via protonated Schiff-bases linked to a lysine reside on the seventh domain<ref name="Article3">PMID:21352497</ref>. A negative agonist means the ligand, when present in the binding pocket of the protein, inhibits the receptor activity<ref name="Article5">PMID:12402507</ref>. The isomerization of cis to trans causes the protein complex to relax which allows for binding of transducin and the signal cascade to progress<ref name="Article3">PMID:21352497</ref>.

<scene name='77/778331/Rhodopsin_and_ligand/1'>Rhodopsin and Ligand</scene> This is rhodopsin with 11-cis retinal bound. After 11-cis retinal becomes activated and becomes all-trans, rhodopsin undergoes the conformational change to become metarhodopsin I and then metarhodopsin II which is the fully active form of rhodopsin. Metarhodopsin II then associates with the G protein transducin and the signal cascade can continue.

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 == Function ==
-Rhodopsin performs two functions. One function is to bind retinal.  Rhodopsin is a protein that is essential for vision, especially in dim light. The photoreceptors in the retina that contain rhodopsin are rods. Rhodopsin is attached to 11-cis retinal which becomes excited by a photon of light and isomerizes to become all-trans conformation<ref name="Article4">PMID:29042326</ref>. This excitation activates rhodopsin and leads to depolarizing of neurons. The depolarizing of neurons is how the image is transmitted to the brain<ref name="Article2">“RHO Gene - Genetics Home Reference.” U.S. National Library of Medicine, National Institutes of Health, 11AD, ghr.nlm.nih.gov/gene/RHO#.</ref>. Another function is to function as a G protein-coupled receptor. When rhodopsin is activated by light the protein couples with the G protein transducin which is the first step in the signal cascade<ref name="Article4">PMID:29042326</ref>. Rhodopsin must undergo several conformational changes before being able to bind transducin<ref name="Article3">PMID:21352497</ref>. Rhodopsin is initially converted to metarhodopsin II which is the active form of rhodopsin. Once the protein is active then metarhodopsin binds the G-protein tranducin and the GDP is exchanged for GTP. The G protein subunits dissociate and causes a decrease in cytosolic cGMP. The decrease in cGMP also causes the closing of calcium channels. When calcium concentrations drop the photoreceptors become hyperpolarized and this ensures the action potential is sent onward toward the brain<ref name="Article5">PMID:12402507</ref>. Photoreceptors are unable to be immediately restimulated, rhodopsin kinase phosphorylates the protein on serine and threonine residues which leads to the binding of arrestin. Arrestin prevents rhodopsin from interacting with tranducin again, thus preventing restimulation of the protein. Arrestin is released from the protein via phospotase A which dephosphorylates rhodopsin<ref name="Article5">PMID:12402507</ref>.
+Rhodopsin performs two functions. One function is to bind retinal.  Rhodopsin is a protein that is essential for vision, especially in dim light. The photoreceptors in the retina that contain rhodopsin are rods. Rhodopsin is attached to 11-cis retinal which becomes excited by a photon of light and isomerizes to become all-trans conformation<ref name="Article4">PMID:29042326</ref>. This excitation activates rhodopsin and leads to depolarizing of neurons. The depolarizing of neurons is how the image is transmitted to the brain<ref name="Article2">“RHO Gene - Genetics Home Reference.” U.S. National Library of Medicine, National Institutes of Health, 11AD, ghr.nlm.nih.gov/gene/RHO#.</ref>. Another function of rhodopsin is to function as a G protein-coupled receptor. When rhodopsin is activated by light the protein couples with the G protein transducin which is the first step in the signal cascade<ref name="Article4">PMID:29042326</ref>. Rhodopsin must undergo several conformational changes before being able to bind transducin<ref name="Article3">PMID:21352497</ref>. Rhodopsin is initially converted to metarhodopsin II which is the active form of rhodopsin. Once the protein is active then metarhodopsin binds the G-protein tranducin and the GDP is exchanged for GTP. The G protein subunits dissociate and causes a decrease in cytosolic cGMP. The decrease in cGMP also causes the closing of calcium channels. When calcium concentrations drop the photoreceptors become hyperpolarized and this ensures the action potential is sent onward toward the brain<ref name="Article5">PMID:12402507</ref>. Photoreceptors are unable to be immediately restimulated, rhodopsin kinase phosphorylates the protein on serine and threonine residues which leads to the binding of arrestin. Arrestin prevents rhodopsin from interacting with tranducin again, thus preventing restimulation of the protein. Arrestin is released from the protein via phospotase A which dephosphorylates rhodopsin<ref name="Article5">PMID:12402507</ref>.
 == Disease ==
@@ Line 39: / Line 39: @@
 <scene name='77/778331/Rhodopsin_no_ligand/1'>Rhodopsin protein</scene> Fully functional rhodopsin has the typical GPCR structure of a seven transmembrane helical bundle with the N-terminus on the interior of the rods and the C-terminus in the cytoplasm. The N-terminus is located near the extracellular loops and ends of the transmembrane protein. There are hydrogen bonding between the transmembrane sections and the extracellular loops that are involved in the activation of rhodopsin when a photon is received. The N-terminus is thought to play a role in orientation of the extracellular loops<ref name="Article4">PMID:29042326</ref>. Transmembrane domain 1 and 2 play a role in stabilizing the protein and giving the protein functionality<ref name="Article3">PMID:21352497</ref>. Rhodopsin has two components: opsin (a membrane-bound polypeptide) and 11-cis-retinal (a chromophore that is bound to opsin via a protonated Schiff-base)<ref name="Article5">PMID:12402507</ref>.
-<scene name='77/778331/Rhodopsin_ligand/1'>11-cis retinal</scene> 11-cis retinal is the ligand, a molecule that is derived from vitamin A, is necessary for rhodopsin function. The ligand performs an inverse agonist suppressing activity on the photon receptor and is associated with the protein via protonated Schiff-bases linked to a lysine reside on the seventh domain<ref name="Article3">PMID:21352497</ref>. A negative agonist means the ligand, when present in the binding pocket of the protein, inhibits the receptor activity<ref name="Article5">PMID:12402507</ref>. The isomerization of cis to trans causes the protein complex to relax which allows for binding of transducin and the signal cascade to progress<ref name="Article3">PMID:21352497</ref>.
+<scene name='77/778331/Rhodopsin_ligand/1'>11-cis retinal</scene> 11-cis retinal, a molecule that is derived from vitamin A, is necessary for rhodopsin function. The ligand performs an inverse agonist suppressing activity on the photon receptor and is associated with the protein via protonated Schiff-bases linked to a lysine reside on the seventh domain<ref name="Article3">PMID:21352497</ref>. A negative agonist means the ligand, when present in the binding pocket of the protein, inhibits the receptor activity<ref name="Article5">PMID:12402507</ref>. The isomerization of cis to trans causes the protein complex to relax which allows for binding of transducin and the signal cascade to progress<ref name="Article3">PMID:21352497</ref>.
 <scene name='77/778331/Rhodopsin_and_ligand/1'>Rhodopsin and Ligand</scene> This is rhodopsin with 11-cis retinal bound. After 11-cis retinal becomes activated and becomes all-trans, rhodopsin undergoes the conformational change to become metarhodopsin I and then metarhodopsin II which is the fully active form of rhodopsin. Metarhodopsin II then associates with the G protein transducin and the signal cascade can continue.