Sandbox 173: Difference between revisions
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There is positive enthalpy associated with the formation of Metarhodopsin II. This formation of the active state, also linked with the increase in entropy, is suggested to release the constraints in the helices and expose the cytoplasmic binding sites<ref name="Article9"/>. An important part of this process includes the 9-methyl group of retinal, which is suggested to provide a scaffold for proton transfers essential for the formation of the active state<ref name="Article9"/>. | There is positive enthalpy associated with the formation of Metarhodopsin II. This formation of the active state, also linked with the increase in entropy, is suggested to release the constraints in the helices and expose the cytoplasmic binding sites<ref name="Article9"/>. An important part of this process includes the 9-methyl group of retinal, which is suggested to provide a scaffold for proton transfers essential for the formation of the active state<ref name="Article9"/>. | ||
====Signalling Cascade and Polarization of the Cell Membrane==== | ====Signalling Cascade and Polarization of the Cell Membrane==== | ||
[[image:RhodopsinTransducinComplex.jpg|thumb|right|Rhodopsin interaction with transducin.]] | [[image:RhodopsinTransducinComplex.jpg|thumb|right|Rhodopsin interaction with transducin.]] | ||
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====Phosphorylation and Deactivation of Rhodopsin==== | ====Phosphorylation and Deactivation of Rhodopsin==== | ||
<applet load='1u19' size='300' color='black' frame='true' align='right' caption='Phosphorylation of Rhodospin. The generated structure is from Chain A.'/> | |||
[http://en.wikipedia.org/wiki/Rhodopsin_kinase Rhodopsin kinase] phosphorylates rhodopsin and [http://en.wikipedia.org/wiki/Arrestin arrestin] binds to the phosphorylated domain of rhodopsin, preventing further signal transduction from Metarhodopsin II of activated rhodopsin and transducin<ref name="Article3"/>. It phosphorylates both Metarhodopsin II and cone opsins. The majority of the phosphorylation sites are in the cytoplasmic C-terminal region of rhodopsin with seven hydroxy-amino acids. The most favoured amino acids are <scene name='Sandbox_173/Phosphorylated_sites/1'>Serine 338, Serine 343, Serine 334, Threonine 335 and Threonine 336</scene><ref name="Article7">PMID:9667002</ref>, and these residues form an arrangement in rhodopsin that do not appear to be exposed to the solvent. Interactions with the C-terminal tail and a portion of the Cytoplasmic loop 3 appear to be broken for the phosphorylation of the hydroxyl groups<ref name="Article9"/>. For the next cycle of activation of rhodopsin, rhodopsin has to be dephosphorylated, and have the all-''trans'' retinal replaced with the 11-''cis'' retinal<ref name="Article19"/>. | [http://en.wikipedia.org/wiki/Rhodopsin_kinase Rhodopsin kinase] phosphorylates rhodopsin and [http://en.wikipedia.org/wiki/Arrestin arrestin] binds to the phosphorylated domain of rhodopsin, preventing further signal transduction from Metarhodopsin II of activated rhodopsin and transducin<ref name="Article3"/>. It phosphorylates both Metarhodopsin II and cone opsins. The majority of the phosphorylation sites are in the cytoplasmic C-terminal region of rhodopsin with seven hydroxy-amino acids. The most favoured amino acids are <scene name='Sandbox_173/Phosphorylated_sites/1'>Serine 338, Serine 343, Serine 334, Threonine 335 and Threonine 336</scene><ref name="Article7">PMID:9667002</ref>, and these residues form an arrangement in rhodopsin that do not appear to be exposed to the solvent. Interactions with the C-terminal tail and a portion of the Cytoplasmic loop 3 appear to be broken for the phosphorylation of the hydroxyl groups<ref name="Article9"/>. For the next cycle of activation of rhodopsin, rhodopsin has to be dephosphorylated, and have the all-''trans'' retinal replaced with the 11-''cis'' retinal<ref name="Article19"/>. | ||