Sandbox 173: Difference between revisions

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Proteopedia Page Contributors and Editors (what is this?)Proteopedia Page Contributors and Editors (what is this?)

Andrea Gorrell, Cinting Lim

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 <applet load='3cap' size='300' color='black' frame='true' align='right' caption='Structure of Opsin†. The generated structure is from Chain A.'/>
 ===Topology Overview===
-The overall dimeric structure of opsin is similar to rhodopsin, with seven transmembrane helices linked by three extracellular loops and three cytoplasmic loops and a cytoplasmic Helix 8. The small differences between the topology of the two proteins include a short helical turn in the cytoplasmic loop 1 in opsin, 1.5-2.5 helical turns longer in Helix 5 for opsin in comparison to rhodopsin, and a large outward tilt of Helix 6 of opsin<ref>Article Opsin 2</ref>. Also, in constrast to rhodopsin, opsin has two openings of the retinal-binding pocket; one of the openings is between Helix 1 and Helix 7, and the other opening is between the extracellular ends of Helix 5 and 6. This opening is formed by the residues <scene name='Sandbox_173/Opsin_retinal_opening/1'>Isoleucine 205 and Phenylalanine 208 in Helix 5, and by the residues Phenylalanine 273 and Phenylalanine 276 in Helix 6</scene><ref>Article Opsin 2</ref>. The two openings suggest different sites of retinal entrance and exit in retinal channeling<ref>Article Opsin 2</ref>.
+The overall dimeric structure of opsin is similar to rhodopsin, with seven transmembrane helices linked by three extracellular loops and three cytoplasmic loops and a cytoplasmic Helix 8. The small differences between the topology of the two proteins include a short helical turn in the cytoplasmic loop 1 in opsin, 1.5-2.5 helical turns longer in Helix 5 for opsin in comparison to rhodopsin, and a large outward tilt of Helix 6 of opsin<ref name="ArticleOpsin2">PMID:18563085</ref>. Also, in constrast to rhodopsin, opsin has two openings of the retinal-binding pocket; one of the openings is between Helix 1 and Helix 7, and the other opening is between the extracellular ends of Helix 5 and 6. This opening is formed by the residues <scene name='Sandbox_173/Opsin_retinal_opening/1'>Isoleucine 205 and Phenylalanine 208 in Helix 5, and by the residues Phenylalanine 273 and Phenylalanine 276 in Helix 6</scene><ref name="ArticleOpsin2"/>. The two openings suggest different sites of retinal entrance and exit in retinal channeling<ref name="ArticleOpsin2"/>.
 ===Activity===
-The ability of opsin to activate transducin is modulated by both 11-''cis'' retinal and the all-''trans'' retinal; the 11-''cis'' retinal reduces its activity while the all-''trans'' retinal enhances it through non-covalent interactions <ref="ArticleOpsin1">PMID:9628807</ref>. This may give insight on the ability of all-''trans'' retinal, in combination with opsin, to alter the photoreceptor sensitivities<ref name="ArticleOpsin1"/>.
+The ability of opsin to activate transducin is modulated by both 11-''cis'' retinal and the all-''trans'' retinal; the 11-''cis'' retinal reduces its activity while the all-''trans'' retinal enhances it through non-covalent interactions <ref name="ArticleOpsin1">PMID:9628807</ref>. This may give insight on the ability of all-''trans'' retinal, in combination with opsin, to alter the photoreceptor sensitivities<ref name="ArticleOpsin1"/>.
 ===Colour Vision===