Circular dichroism of cattle rhodopsin and bathorhodopsin at liquid nitrogen temperatures
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Squid rhodopsin (lambda(max) 493 mmicro)-like vertebrate rhodopsins-contains a retinene chromophore linked to a protein, opsin. Light transforms rhodopsin to lumi- and metarhodopsin. However, whereas vertebrate metarhodopsin at physiological temperatures decomposes into retinene and opsin, squid metarhodopsin is stable. Light also converts squid metarhodopsin to rhodopsin. Rhodopsin is therefore regenerated from metarhodopsin in the light. Irradiation of rhodopsin or metarhodopsin produces a steady state by promoting the reactions, See PDF for Equation Squid rhodopsin contains neo-b (11-cis) retinene; metarhodopsin all-trans retinene. The interconversion of rhodopsin and metarhodopsin involves only the stereoisomerization of their chromophores. Squid metarhodopsin is a pH indicator, red (lambda(max) 500 mmicro) near neutrality, yellow (lambda(max) 380 mmicro) in alkaline solution. The two forms-acid and alkaline metarhodopsin-are interconverted according to the equation, Alkaline metarhodopsin + H(+) right harpoon over left harpoonacid metarhodopsin, with pK 7.7. In both forms, retinene is attached to opsin at the same site as in rhodopsin. However, metarhodopsin decomposes more readily than rhodopsin into retinene and opsin. The opsins apparently fit the shape of the neo-b chromophore. When light isomerizes the chromophore to the all-trans configuration, squid opsin accepts the all-trans chromophore, while vertebrate opsins do not and hence release all-trans retinene. Light triggers vision by affecting directly the shape of the retinene chromophore. This changes its relationship with opsin, so initiating a train of chemical reactions.
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ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTPhotochemical reactions of 13-demethyl visual pigment analogs at low temperaturesYoshinori Shichida, Allen Kropf, and Toru YoshizawaCite this: Biochemistry 1981, 20, 7, 1962–1968Publication Date (Print):March 31, 1981Publication History Published online1 May 2002Published inissue 31 March 1981https://pubs.acs.org/doi/10.1021/bi00510a035https://doi.org/10.1021/bi00510a035research-articleACS PublicationsRequest reuse permissionsArticle Views45Altmetric-Citations23LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose Get e-Alerts
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Author(s): Williams, Owen | Advisor(s): Kliger, David S | Abstract: This work examines the microsecond and millisecond photochemistry of human rhodopsin. There have been significant advances in the mechanistic and structural understanding of bovine rhodopsin over the last two decades that have not been applied to human rhodopsin. This study uses time-resolved absorbance spectroscopy to probe human rhodopsin in its native disk membrane. Human rhodopsin is first studied at pH 7.0 and 20°C from 1 µs - 128 µs to explore the lumirhodopsin I - lumirhodopsin II equilibrium. The remainder of this work examines human rhodopsin at pH 8.7 and 15°C from 5 µs - 120 ms to study the activation mechanism from lumirhodopsin I to metarhodopsin II. The intermediates seen in the bovine rhodopsin mechanism are present in human rhodopsin, but with differing kinetics. The processes observed in human rhodopsin are slower than in bovine rhodopsin, and the equilibria are shifted towards 380 nm product compared to bovine rhodopsin under similar conditions.
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This chapter contains sections titled: Introduction Rhodopsin and Mammalian Visual Phototransduction Signal Amplification by Light-activated Rhodopsin Inactivation of Light-activated Rhodopsin Properties of Rhodopsin Isolation of Rhodopsin Biochemical and Physicochemical Properties of Rhodopsin Post-translational Modifications in Rhodopsin Membrane Topology of Rhodopsin and Functional Domains Chromophore Binding Pocket and Photolysis of Rhodopsin Structure of Rhodopsin Crystal Structure of Rhodopsin Atomic Force Microscopy of Rhodopsin in the Disk Membrane Activation Mechanism of Rhodopsin Conclusions Acknowledgements References
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Abstract Originally published in: Handbook of Photosensory Receptors. Edited by Winslow R. Briggs and John L. Spudich. Copyright © 2005 Wiley‐VCH Verlag GmbH & Co. KGaA Weinheim. Print ISBN: 3‐527‐31019‐7 The sections in this article are Introduction Rhodopsin and Mammalian Visual Phototransduction Signal Amplification by Light‐activated Rhodopsin Inactivation of Light‐activated Rhodopsin Properties of Rhodopsin Isolation of Rhodopsin Biochemical and Physicochemical Properties of Rhodopsin Post‐translational Modifications in Rhodopsin Membrane Topology of Rhodopsin and Functional Domains Transmembrane Domain of Rhodopsin Intradiscal Domain of Rhodopsin Cytoplasmic Domain of Rhodopsin Chromophore Binding Pocket and Photolysis of Rhodopsin Structure of Rhodopsin Crystal Structure of Rhodopsin Atomic Force Microscopy of Rhodopsin in the Disk Membrane Activation Mechanism of Rhodopsin Conclusions Acknowledgements
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