Sandbox 173
From Proteopedia
Rhodopsin, a dimeric protein, is a highly characterized G protein-coupled receptor found in the neurons of the retina and in rod photoreceptor cells. It is part of the Class A (Family 1) of G protein-coupled receptors, a superfamily of membrane receptors with seven transmembrane helices[1]. G protein-coupled receptors mediate responses to visual, olfactory, hormonal, and neurotransmitter signals among others[2].
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| 1u19, resolution 2.20Å () | |||||||||
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| Ligands: | , , , , , , , , | ||||||||
| Non-Standard Residues: | |||||||||
| Related: | 1f88, 1hzx, 1l9h | ||||||||
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| Resources: | FirstGlance, OCA, PDBsum, RCSB | ||||||||
| Coordinates: | save as pdb, mmCIF, xml | ||||||||
Contents |
Structure
Characteristic G Protein-Coupled Receptor Architecture
Rhodopsin consists of seven mostly α-helical transmembrane domains (H1-H7) linked sequentially by extracellular and cytoplasmic loops (E1-E3 and C1-C3 respectively), with the extracellular amino-terminal tail and the cytoplasmic carboxyl-terminal tail[3]. Four of the helices are tilted and three of the helices are approximately perpendicular to the membrane plane[4]. There is notable interaction between the four extracellular domains, but only a few associations are observed with the cytoplasmic domains[5].
Also, there is the presence of a cationic amphipathic Helix 8, known as the fourth cytoplasmic loop, that is formed from the C-terminal tail anchoring to the membrane by two cysteines, which include palmitates in the structure. This helix runs approximately parallel to the cytoplasmic surface and is involved in Gtγ binding[6], as well as the modulation of rhodopsin-transducin interactions and rhodopsin-phospholipid interactions[7].
The structure of rhodopsin may provide stability to the important Schiff base linkage with the retinal by affecting its hydrolysis, limiting its interactions with solvent, and inhibiting its release when hydrolyzed, thus encouraging rebinding of the Schiff base linkage[8].
Function
Light-Induced Visual Signal Transduction
Light absorption and G protein activation
Opsin
References
- Okada T, Sugihara M, Bondar AN, Elstner M, Entel P, Buss V. The retinal conformation and its environment in rhodopsin in light of a new 2.2 A crystal structure. J Mol Biol. 2004 Sep 10;342(2):571-83. PMID:15327956 doi:10.1016/j.jmb.2004.07.044
| Please do NOT make changes to this Sandbox until after April 23, 2010. Sandboxes 151-200 are reserved until then for use by the Chemistry 307 class at UNBC taught by Prof. Andrea Gorrell. |
