Retinal Photoreceptor Rhodopsin: A G-Protein Receptor Essay examples

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G-protein-coupled receptors (GPCRs) are membrane proteins that provide a molecular link between extracellular signals and intracellular processes. The retinal photoreceptor Rhodopsin (Rho) is one of the prime examples of the G-protein-coupled receptor superfamily which is a visual pigment which absorbs photons and initiates G-protein signal transduction processes that result in electrical signals processed by the brain. Rod cells, containing rhodopsin in their outer segments, mediate vision by responding to dim levels of light. Cone opsins are proteins related to rhodopsin and are present in cone cells. These proteins also use 11-cis-retinal as a chromophore, but their absorption maxima are located at wavelengths different from that of …show more content…
G-protein-coupled receptors (GPCRs) are membrane proteins that provide a molecular link between extracellular signals and intracellular processes. The retinal photoreceptor Rhodopsin (Rho) is one of the prime examples of the G-protein-coupled receptor superfamily which is a visual pigment which absorbs photons and initiates G-protein signal transduction processes that result in electrical signals processed by the brain. Rod cells, containing rhodopsin in their outer segments, mediate vision by responding to dim levels of light. Cone opsins are proteins related to rhodopsin and are present in cone cells. These proteins also use 11-cis-retinal as a chromophore, but their absorption maxima are located at wavelengths different from that of rhodopsin thus forming the basis for color vision. Comparison of the amino acid sequences for the human blue, green, and red cone opsins with that of rhodopsin show 41%, 38%, and 37% amino acid similarity, respectively.
Cryo-electron microscopy (cryo-EM) of two-dimensional rhodopsin crystals provided the first views of the seven transmembrane helices forming the core of the protein's structure. NMR spectroscopy has also been applied to illustrate the structure and function of the chromophore and the peptide fragments.
The rhodopsin molecule is a monomer, ocassionally functioning also as dimers and/or oligomers, made up of 348 amino acids, having a molecular weight of 38,893 Da. The N terminus of the protein is located on the extracellular side
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