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GRK1
Rhodopsin kinase (, ''rod opsin kinase'', ''G-protein-coupled receptor kinase 1'', ''GPCR kinase 1'', ''GRK1'', ''opsin kinase'', ''opsin kinase (phosphorylating)'', ''rhodopsin kinase (phosphorylating)'', ''RK'', ''STK14'') is a serine/threonine-specific protein kinase involved in phototransduction. This enzyme catalyses the following chemical reaction: : ATP + rhodopsin \rightleftharpoons ADP + phospho-rhodopsin Mutations in rhodopsin kinase are associated with a form of night blindness called Oguchi disease. Function and mechanism of action Rhodopsin kinase is a member of the family of G protein-coupled receptor kinases, and is officially named G protein-coupled receptor kinase 1, or GRK1. Rhodopsin kinase is found primarily in mammalian retinal rod cells, where it phosphorylates light-activated rhodopsin, a member of the family of G protein-coupled receptors that recognizes light. Phosphorylated, light-activated rhodopsin binds to the protein arrestin to terminate the lig ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
G-protein Coupled Receptor Kinases
G protein-coupled receptor kinases (GPCRKs, GRKs) are a protein family, family of protein kinases within the protein kinase#Protein kinase groups, AGC (protein kinase A, protein kinase G, protein kinase C) group of kinases. Like all AGC kinases, GRKs use ATP to add phosphate to Serine and Threonine residues in specific locations of target proteins. In particular, GRKs phosphorylation, phosphorylate intracellular domains of G protein-coupled receptors (GPCRs). GRKs function in tandem with arrestin proteins to regulate the sensitivity of GPCRs for stimulating downstream heterotrimeric G protein and G protein-coupled receptor#G-protein-independent signaling, G protein-independent signaling pathways. Types of GRKs GRK activity and regulation GRKs reside normally in an inactive state, but their kinase activity is stimulated by binding to a ligand-activated GPCR (rather than by regulatory phosphorylation as is common in other AGC kinases). Because there are only seven GRKs (only ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
G Protein-coupled Receptor Kinases
G protein-coupled receptor kinases (GPCRKs, GRKs) are a family of protein kinases within the AGC (protein kinase A, protein kinase G, protein kinase C) group of kinases. Like all AGC kinases, GRKs use ATP to add phosphate to Serine and Threonine residues in specific locations of target proteins. In particular, GRKs phosphorylate intracellular domains of G protein-coupled receptors (GPCRs). GRKs function in tandem with arrestin proteins to regulate the sensitivity of GPCRs for stimulating downstream heterotrimeric G protein and G protein-independent signaling pathways. Types of GRKs GRK activity and regulation GRKs reside normally in an inactive state, but their kinase activity is stimulated by binding to a ligand-activated GPCR (rather than by regulatory phosphorylation as is common in other AGC kinases). Because there are only seven GRKs (only 4 of which are widely expressed throughout the body) but over 800 human GPCRs, GRKs appear to have limited phosphorylation site ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Recoverin
Recoverin is a 23 kilodalton (kDa) neuronal calcium-binding protein that is primarily detected in the photoreceptor cells of the eye. It plays a key role in the inhibition of rhodopsin kinase, a molecule which regulates the phosphorylation of rhodopsin. A reduction in this inhibition helps regulate sensory adaptation in the retina, since the light-dependent channel closure in photoreceptors causes calcium levels to decrease, which relieves the inhibition of rhodopsin kinase by calcium-bound recoverin, leading to a more rapid inactivation of metarhodopsin II (activated form of rhodopsin). Structure Recoverin structure consists of four EF-hand motifs arranged in a compact array, which contrasts with the dumbbell shape of other calcium-binding proteins like calmodulin and troponin C Troponin C is a protein which is part of the troponin complex. It contains four calcium-binding EF hands, although different isoforms may have fewer than four functional calcium-binding subdomai ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oguchi Disease
Oguchi disease is an autosomal recessive form of congenital stationary night blindness associated with fundus discoloration and abnormally slow dark adaptation. Presentation Genetics Several mutations have been implicated as a cause of Oguchi disease. These include mutations in the arrestin gene or the rhodopsin kinase gene. The condition is more frequent in individuals of Japanese ethnicity. Diagnosis Oguchi disease present with nonprogressive night blindness since young childhood or birth with normal day vision, but they frequently claim improvement of light sensitivities when they remain for some time in a darkened environment. On examination patients have normal visual fields but the fundi have a diffuse or patchy, silver-gray or golden-yellow metallic sheen and the retinal vessels stand out in relief against the background. A prolonged dark adaptation of three hours or more, leads to disappearance of this unusual discoloration and the appearance of a normal reddish ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
G Protein-coupled Receptor Kinase 7
G-protein-coupled receptor kinase 7 (, ''GRK7'', ''cone opsin kinase'', ''iodopsin kinase'') is a serine/threonine-specific protein kinase involved in phototransduction Visual phototransduction is the sensory transduction process of the visual system by which light is detected by photoreceptor cells ( rods and cones) in the vertebrate retina. A photon is absorbed by a retinal chromophore (each bound to an opsin), .... This enzyme catalyses the phosphorylation of cone (color) photopsins in retinal cones during high acuity color vision primarily in the fovea. More on GRK7 GRK7 is a member of the family of G protein-coupled receptor kinases, and is officially named G protein-coupled receptor kinase 7. GRK7 is found primarily in mammalian retinal cone cells, where it phosphorylates light-activated photopsins, members of the family of G protein-coupled receptors that recognize light of various wavelengths (red, green, blue). Phosphorylated, light-activated photopsin binds to t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Farnesylation
Prenylation (also known as isoprenylation or lipidation) is the addition of hydrophobic molecules to a protein or a biomolecule. It is usually assumed that prenyl groups (3-methylbut-2-en-1-yl) facilitate attachment to cell membranes, similar to lipid anchors like the GPI anchor, though direct evidence of this has not been observed. Prenyl groups (also called isoprenyl groups, having one hydrogen atom more than isoprene) have been shown to be important for protein–protein binding through specialized prenyl-binding domains. Protein prenylation Protein prenylation involves the transfer of either a farnesyl or a geranylgeranyl moiety to C-terminal cysteine(s) of the target protein. There are three enzymes that carry out prenylation in the cell, farnesyl transferase, Caax protease and geranylgeranyl transferase I. Farnesylation is a type of prenylation, a post-translational modification of proteins by which an isoprenyl group is added to a cysteine residue. It is an important ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Serine/threonine-specific Protein Kinase
A serine/threonine protein kinase () is a kinase enzyme, in particular a protein kinase, that phosphorylation, phosphorylates the hydroxyl, OH group of the amino acid, amino-acid residues serine or threonine, which have similar side chains. At least 350 of the 500+ human protein kinases are serine/threonine kinases (STK). In enzymology, the term ''serine/threonine protein kinase'' describes a class of enzymes in the family of transferases, that transfer phosphates to the oxygen atom of a serine or threonine side chain in proteins. This process is called phosphorylation. Protein phosphorylation in particular plays a significant role in a wide range of cellular processes and is a very important post-translational modification. The chemical reaction performed by these enzymes can be written as :ATP + a protein \rightleftharpoons ADP + a phosphoprotein Thus, the two substrate (biochemistry), substrates of this enzyme are adenosine triphosphate, ATP and a protein, whereas its ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Visual Phototransduction
Visual phototransduction is the sensory transduction process of the visual system by which light is detected by photoreceptor cells ( rods and cones) in the vertebrate retina. A photon is absorbed by a retinal chromophore (each bound to an opsin), which initiates a signal cascade through several intermediate cells, then through the retinal ganglion cells (RGCs) comprising the optic nerve. Overview Light enters the eye, passes through the optical media, then the inner neural layers of the retina before finally reaching the photoreceptor cells in the outer layer of the retina. The light may be absorbed by a chromophore bound to an opsin, which photoisomerizes the chromophore, initiating both the visual cycle, which "resets" the chromophore, and the phototransduction cascade, which transmits the visual signal to the brain. The cascade begins with graded polarisation (an analog signal) of the excited photoreceptor cell, as its membrane potential increases from a resting po ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rhodopsin
Rhodopsin, also known as visual purple, is a protein encoded by the ''RHO'' gene and a G-protein-coupled receptor (GPCR). It is a light-sensitive receptor protein that triggers visual phototransduction in rod cells. Rhodopsin mediates dim light vision and thus is extremely sensitive to light. When rhodopsin is exposed to light, it immediately photobleaches. In humans, it is fully regenerated in about 30 minutes, after which the rods are more sensitive. Defects in the rhodopsin gene cause eye diseases such as retinitis pigmentosa and congenital stationary night blindness. History Rhodopsin was discovered by Franz Christian Boll in 1876. The name rhodopsin derives from Ancient Greek () for "rose", due to its pinkish color, and () for "sight". It was coined in 1878 by the German physiologist Wilhelm Friedrich Kühne (1837–1900). When George Wald discovered that rhodopsin is a holoprotein, consisting of retinal and an apoprotein, he called it opsin, which tod ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Photoreceptor Cell
A photoreceptor cell is a specialized type of neuroepithelial cell found in the retina that is capable of visual phototransduction. The great biological importance of photoreceptors is that they convert light (visible electromagnetic radiation) into signals that can stimulate biological processes. To be more specific, photoreceptor proteins in the cell absorb photons, triggering a change in the cell's membrane potential. There are currently three known types of photoreceptor cells in mammalian eyes: rod cell, rods, cone cell, cones, and intrinsically photosensitive retinal ganglion cells. The two classic photoreceptor cells are rods and cones, each contributing information used by the visual system to form an image of the environment, Visual perception, sight. Rods primarily mediate scotopic vision (dim conditions) whereas cones primarily mediate photopic vision (bright conditions), but the processes in each that supports phototransduction is similar. The intrinsically photosen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Visual Phototransduction
Visual phototransduction is the sensory transduction process of the visual system by which light is detected by photoreceptor cells ( rods and cones) in the vertebrate retina. A photon is absorbed by a retinal chromophore (each bound to an opsin), which initiates a signal cascade through several intermediate cells, then through the retinal ganglion cells (RGCs) comprising the optic nerve. Overview Light enters the eye, passes through the optical media, then the inner neural layers of the retina before finally reaching the photoreceptor cells in the outer layer of the retina. The light may be absorbed by a chromophore bound to an opsin, which photoisomerizes the chromophore, initiating both the visual cycle, which "resets" the chromophore, and the phototransduction cascade, which transmits the visual signal to the brain. The cascade begins with graded polarisation (an analog signal) of the excited photoreceptor cell, as its membrane potential increases from a resting po ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Retinopathy
Retinopathy is any damage to the retina of the eyes, which may cause vision impairment. Retinopathy often refers to retinal vascular disease, or damage to the retina caused by abnormal blood flow. Age-related macular degeneration is technically included under the umbrella term retinopathy but is often discussed as a separate entity. Retinopathy, or retinal vascular disease, can be broadly categorized into proliferative and non-proliferative types. Frequently, retinopathy is an ocular manifestation of systemic disease as seen in diabetes or hypertension. Diabetes is the most common cause of retinopathy in the U.S. as of 2008. Diabetic retinopathy is the leading cause of blindness in working-aged people. It accounts for about 5% of blindness worldwide and is designated a priority eye disease by the World Health Organization. Signs and symptoms Many people often do not have symptoms until very late in their disease course. Patients often become symptomatic when there is irreversibl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
