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Hong JD, Palczewski K. A short story on how chromophore is hydrolyzed from rhodopsin for recycling. Bioessays 2023; 45:e2300068. [PMID: 37454357 PMCID: PMC10614701 DOI: 10.1002/bies.202300068] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2023] [Revised: 05/24/2023] [Accepted: 05/30/2023] [Indexed: 07/18/2023]
Abstract
The photocycle of visual opsins is essential to maintain the light sensitivity of the retina. The early physical observations of the rhodopsin photocycle by Böll and Kühne in the 1870s inspired over a century's worth of investigations on rhodopsin biochemistry. A single photon isomerizes the Schiff-base linked 11-cis-retinylidene chromophore of rhodopsin, converting it to the all-trans agonist to elicit phototransduction through photoactivated rhodopsin (Rho*). Schiff base hydrolysis of the agonist is a key step in the photocycle, not only diminishing ongoing phototransduction but also allowing for entry and binding of fresh 11-cis chromophore to regenerate the rhodopsin pigment and maintain light sensitivity. Many challenges have been encountered in measuring the rate of this hydrolysis, but recent advancements have facilitated studies of the hydrolysis within the native membrane environment of rhodopsin. These techniques can now be applied to study hydrolysis of agonist in other opsin proteins that mediate phototransduction or chromophore turnover. In this review, we discuss the progress that has been made in characterizing the rhodopsin photocycle and the journey to characterize the hydrolysis of its all-trans-retinylidene agonist.
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Affiliation(s)
- John D. Hong
- Gavin Herbert Eye Institute, Department of Ophthalmology, University of California Irvine, Irvine, CA 92697, USA
- Department of Chemistry, University of California Irvine, Irvine, CA 92697, USA
| | - Krzysztof Palczewski
- Gavin Herbert Eye Institute, Department of Ophthalmology, University of California Irvine, Irvine, CA 92697, USA
- Department of Chemistry, University of California Irvine, Irvine, CA 92697, USA
- Department of Physiology and Biophysics, University of California Irvine, Irvine, CA 92697, USA
- Department of Molecular Biology and Biochemistry, University of California Irvine, Irvine, CA 92697, USA
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2
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Wang F, Fernandez-Gonzalez P, Ramon E, Gomez-Gutierrez P, Morillo M, Garriga P. Effect of Trace Metal Ions on the Conformational Stability of the Visual Photoreceptor Rhodopsin. Int J Mol Sci 2023; 24:11231. [PMID: 37446409 DOI: 10.3390/ijms241311231] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2023] [Revised: 07/01/2023] [Accepted: 07/06/2023] [Indexed: 07/15/2023] Open
Abstract
Trace metals are essential elements that play key roles in a number of biochemical processes governing human visual physiology in health and disease. Several trace metals, such as zinc, have been shown to play important roles in the visual phototransduction process. In spite of this, there has been little research conducted on the direct effect of trace metal elements on the visual photoreceptor rhodopsin. In the current study, we have determined the effect of several metal ions, such as iron, copper, chromium, manganese, and nickel, on the conformational stability of rhodopsin. To this aim, we analyzed, by means of UV-visible and fluorescence spectroscopic methods, the effects of these trace elements on the thermal stability of dark rhodopsin, the stability of its active Metarhodopsin II conformation, and its chromophore regeneration. Our results show that copper prevented rhodopsin regeneration and slowed down the retinal release process after illumination. In turn, Fe3+, but not Fe2+, increased the thermal stability of the dark inactive conformation of rhodopsin, whereas copper ions markedly decreased it. These findings stress the important role of trace metals in retinal physiology at the photoreceptor level and may be useful for the development of novel therapeutic strategies to treat retinal disease.
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Affiliation(s)
- Feifei Wang
- Grup de Biotecnologia Molecular i Industrial, Centre de Biotecnologia Molecular, Departament d'Enginyeria Química, Universitat Politècnica de Catalunya-Barcelona Tech, Edifici Gaia, Rambla de Sant Nebridi 22, 08222 Terrassa, Catalonia, Spain
| | - Pol Fernandez-Gonzalez
- Grup de Biotecnologia Molecular i Industrial, Centre de Biotecnologia Molecular, Departament d'Enginyeria Química, Universitat Politècnica de Catalunya-Barcelona Tech, Edifici Gaia, Rambla de Sant Nebridi 22, 08222 Terrassa, Catalonia, Spain
| | - Eva Ramon
- Grup de Biotecnologia Molecular i Industrial, Centre de Biotecnologia Molecular, Departament d'Enginyeria Química, Universitat Politècnica de Catalunya-Barcelona Tech, Edifici Gaia, Rambla de Sant Nebridi 22, 08222 Terrassa, Catalonia, Spain
| | - Patricia Gomez-Gutierrez
- Departament d'Enginyeria Química, Universitat Politècnica de Catalunya-Barcelona Tech, Edifici ETSEIB, Av. Diagonal 647, 08028 Barcelona, Catalonia, Spain
| | - Margarita Morillo
- Grup de Biotecnologia Molecular i Industrial, Centre de Biotecnologia Molecular, Departament d'Enginyeria Química, Universitat Politècnica de Catalunya-Barcelona Tech, Edifici Gaia, Rambla de Sant Nebridi 22, 08222 Terrassa, Catalonia, Spain
| | - Pere Garriga
- Grup de Biotecnologia Molecular i Industrial, Centre de Biotecnologia Molecular, Departament d'Enginyeria Química, Universitat Politècnica de Catalunya-Barcelona Tech, Edifici Gaia, Rambla de Sant Nebridi 22, 08222 Terrassa, Catalonia, Spain
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3
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Hofmann KP, Lamb TD. Rhodopsin, light-sensor of vision. Prog Retin Eye Res 2023; 93:101116. [PMID: 36273969 DOI: 10.1016/j.preteyeres.2022.101116] [Citation(s) in RCA: 21] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2022] [Revised: 08/20/2022] [Accepted: 08/22/2022] [Indexed: 11/06/2022]
Abstract
The light sensor of vertebrate scotopic (low-light) vision, rhodopsin, is a G-protein-coupled receptor comprising a polypeptide chain with bound chromophore, 11-cis-retinal, that exhibits remarkable physicochemical properties. This photopigment is extremely stable in the dark, yet its chromophore isomerises upon photon absorption with 70% efficiency, enabling the activation of its G-protein, transducin, with high efficiency. Rhodopsin's photochemical and biochemical activities occur over very different time-scales: the energy of retinaldehyde's excited state is stored in <1 ps in retinal-protein interactions, but it takes milliseconds for the catalytically active state to form, and many tens of minutes for the resting state to be restored. In this review, we describe the properties of rhodopsin and its role in rod phototransduction. We first introduce rhodopsin's gross structural features, its evolution, and the basic mechanisms of its activation. We then discuss light absorption and spectral sensitivity, photoreceptor electrical responses that result from the activity of individual rhodopsin molecules, and recovery of rhodopsin and the visual system from intense bleaching exposures. We then provide a detailed examination of rhodopsin's molecular structure and function, first in its dark state, and then in the active Meta states that govern its interactions with transducin, rhodopsin kinase and arrestin. While it is clear that rhodopsin's molecular properties are exquisitely honed for phototransduction, from starlight to dawn/dusk intensity levels, our understanding of how its molecular interactions determine the properties of scotopic vision remains incomplete. We describe potential future directions of research, and outline several major problems that remain to be solved.
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Affiliation(s)
- Klaus Peter Hofmann
- Institut für Medizinische Physik und Biophysik (CC2), Charité, and, Zentrum für Biophysik und Bioinformatik, Humboldt-Unversität zu Berlin, Berlin, 10117, Germany.
| | - Trevor D Lamb
- Eccles Institute of Neuroscience, John Curtin School of Medical Research, The Australian National University, Canberra, ACT 2600, Australia.
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4
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Guérin DMA, Digilio A, Branda MM. Dimeric Rhodopsin R135L Mutant-Transducin-like Complex Sheds Light on Retinitis Pigmentosa Misfunctions. J Phys Chem B 2021; 125:12958-12971. [PMID: 34793169 DOI: 10.1021/acs.jpcb.1c06348] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Rhodopsin (RHO) is a light-sensitive pigment in the retina and the main prototypical protein of the G-protein-coupled receptor (GCPR) family. After receiving a light stimulus, RHO and its cofactor retinylidene undergo a series of structural changes that initiate an intricate transduction mechanism. Along with RHO, other partner proteins play key roles in the signaling pathway. These include transducin, a GTPase, kinases that phosphorylate RHO, and arrestin (Arr), which ultimately stops the signaling process and promotes RHO regeneration. A large number of RHO genetic mutations may lead to very severe retinal dysfunction and eventually to impaired dark adaptation disease called autosomal dominant retinitis pigmentosa (adRP). In this study, we used molecular dynamics (MD) simulations to evaluate the different behaviors of the dimeric form of wild-type RHO (WT dRHO) and its mutant at position 135 of arginine to leucine (dR135L), both in the free (noncomplexed) and in complex with the transducin-like protein (Gtl). Gtl is a heterotrimeric model composed of a mixture of human and bovine G proteins. Our calculations allow us to explain how the mutation causes structural changes in the RHO dimer and how this can affect the signal that transducin generates when it is bound to RHO. Moreover, the structural modifications induced by the R135L mutation can also account for other misfunctions observed in the up- and downstream signaling pathways. The mechanism of these dysfunctions, together with the transducin activity reduction, provides structure-based explanations of the impairment of some key processes that lead to adRP.
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Affiliation(s)
- Diego M A Guérin
- Department of Biochemistry and Molecular Biology, University of the Basque Country (EHU) and Instituto Biofisika (CSIC, UPV/EHU), Barrio Sarriena S/N, 48940 Leioa, Vizcaya, Spain
| | - Ayelen Digilio
- Department of Physics, National University of San Luis (UNSL), Av. Ejército de los Andes 950, 5700 San Luis, Argentina
| | - María Marta Branda
- Institute of Applied Physics (CONICET-UNSL), Av. Ejercito de los Andes 950, 5700 San Luis, Argentina
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Cross-linking of bovine rhodopsin with sulfosuccinimidyl 4-(N maleimidomethyl)cyclohexane-1-carboxylate affects its functionality. Biochem J 2020; 477:2295-2312. [PMID: 32497171 DOI: 10.1042/bcj20200376] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2020] [Revised: 06/01/2020] [Accepted: 06/03/2020] [Indexed: 02/08/2023]
Abstract
Rhodopsin is the photoreceptor protein involved in visual excitation in retinal rods. The functionality of bovine rhodopsin was determined following treatment with sulfosuccinimidyl 4-(N maleimidomethyl)cyclohexane-1-carboxylate (sulfo-SMCC), a bifunctional reagent capable of forming covalent cross-links between suitable placed lysines and cysteines. Denaturing polyacrylamide gel electrophoresis showed that rhodopsin incubated with sulfo-SMCC generated intermolecular dimers, trimers, and higher oligomers, although most of the sulfo-SMCC-treated protein remained as a monomer. Minor alterations on the absorption spectrum of light-activated sulfo-SMCC-treated rhodopsin were observed. However, only ∼2% stimulation of the guanine nucleotide binding activity of transducin was measured in the presence of sulfo-SMCC-cross-linked photolyzed rhodopsin. Moreover, rhodopsin kinase was not able of phosphorylating sulfo-SMCC-cross-linked rhodopsin after illumination. Rhodopsin was purified in the presence of either 0.1% or 1% n-dodecyl β-d-maltoside, to obtain dimeric and monomeric forms of the protein, respectively. Interestingly, no generation of the regular F1 and F2 thermolytic fragments was perceived with sulfo-SMCC-cross-linked rhodopsin either in the dimeric or monomeric state, implying the formation of intramolecular connections in the protein that might thwart the light-induced conformational changes required for interaction with transducin and rhodopsin kinase. Structural analysis of the rhodopsin three-dimensional structure suggested that the following lysine and cysteine pairs: Lys66/Lys67 and Cys316, Cys140 and Lys141, Cys140 and Lys248, Lys311 and Cys316, and/or Cys316 and Lys325 are potential candidates to generate intramolecular cross-links in the protein. Yet, the lack of fragmentation of sulfo-SMCC-treated Rho with thermolysin is consistent with the formation of cross-linking bridges between Lys66/Lys67 and Cys316, and/or Cys140 and Lys248.
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Membrane Curvature Revisited-the Archetype of Rhodopsin Studied by Time-Resolved Electronic Spectroscopy. Biophys J 2020; 120:440-452. [PMID: 33217383 DOI: 10.1016/j.bpj.2020.11.007] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2020] [Revised: 11/01/2020] [Accepted: 11/10/2020] [Indexed: 12/13/2022] Open
Abstract
G-protein-coupled receptors (GPCRs) comprise the largest and most pharmacologically targeted membrane protein family. Here, we used the visual receptor rhodopsin as an archetype for understanding membrane lipid influences on conformational changes involved in GPCR activation. Visual rhodopsin was recombined with lipids varying in their degree of acyl chain unsaturation and polar headgroup size using 1-palmitoyl-2-oleoyl-sn-glycero- and 1,2-dioleoyl-sn-glycerophospholipids with phosphocholine (PC) or phosphoethanolamine (PE) substituents. The receptor activation profile after light excitation was measured using time-resolved ultraviolet-visible spectroscopy. We discovered that more saturated POPC lipids back shifted the equilibrium to the inactive state, whereas the small-headgroup, highly unsaturated DOPE lipids favored the active state. Increasing unsaturation and decreasing headgroup size have similar effects that combine to yield control of rhodopsin activation, and necessitate factors beyond proteolipid solvation energy and bilayer surface electrostatics. Hence, we consider a balance of curvature free energy with hydrophobic matching and demonstrate how our data support a flexible surface model (FSM) for the coupling between proteins and lipids. The FSM is based on the Helfrich formulation of membrane bending energy as we previously first applied to lipid-protein interactions. Membrane elasticity and curvature strain are induced by lateral pressure imbalances between the constituent lipids and drive key physiological processes at the membrane level. Spontaneous negative monolayer curvature toward water is mediated by unsaturated, small-headgroup lipids and couples directly to GPCR activation upon light absorption by rhodopsin. For the first time to our knowledge, we demonstrate this modulation in both the equilibrium and pre-equilibrium evolving states using a time-resolved approach.
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Getter T, Gulati S, Zimmerman R, Chen Y, Vinberg F, Palczewski K. Stereospecific modulation of dimeric rhodopsin. FASEB J 2019; 33:9526-9539. [PMID: 31121099 PMCID: PMC6662988 DOI: 10.1096/fj.201900443rr] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2019] [Accepted: 04/23/2019] [Indexed: 11/11/2022]
Abstract
The classic concept that GPCRs function as monomers has been challenged by the emerging evidence of GPCR dimerization and oligomerization. Rhodopsin (Rh) is the only GPCR whose native oligomeric arrangement was revealed by atomic force microscopy demonstrating that Rh exists as a dimer. However, the role of Rh dimerization in retinal physiology is currently unknown. In this study, we identified econazole and sulconazole, two small molecules that disrupt Rh dimer contacts, by implementing a cell-based high-throughput screening assay. Racemic mixtures of identified lead compounds were separated and tested for their stereospecific binding to Rh using UV-visible spectroscopy and intrinsic fluorescence of tryptophan (Trp) 265 after illumination. By following the changes in UV-visible spectra and Trp265 fluorescence in vitro, we found that binding of R-econazole modulates the formation of Meta III and quenches the intrinsic fluorescence of Trp265. In addition, electrophysiological ex vivo recording revealed that R-econazole slows photoresponse kinetics, whereas S-econazole decreased the sensitivity of rods without effecting the kinetics. Thus, this study contributes new methodology to identify compounds that disrupt the dimerization of GPCRs in general and validates the first active compounds that disrupt the Rh dimer specifically.-Getter, T., Gulati, S., Zimmerman, R., Chen, Y., Vinberg, F., Palczewski, K. Stereospecific modulation of dimeric rhodopsin.
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Affiliation(s)
- Tamar Getter
- Department of Ophthalmology, Gavin Herbert Eye Institute, University of California–Irvine, California, USA
- Department of Pharmacology, Case Western Reserve University, Cleveland, Ohio, USA
| | - Sahil Gulati
- Department of Ophthalmology, Gavin Herbert Eye Institute, University of California–Irvine, California, USA
- Department of Pharmacology, Case Western Reserve University, Cleveland, Ohio, USA
- Department of Physiology and Biophysics, University of California–Irvine, Irvine, California, USA
| | - Remy Zimmerman
- Department of Ophthalmology, Gavin Herbert Eye Institute, University of California–Irvine, California, USA
| | - Yuanyuan Chen
- Department of Ophthalmology, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
- McGowan Institute of Regenerative Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Frans Vinberg
- Department of Ophthalmology and Visual Sciences, University of Utah, Salt Lake City, Utah, USA
| | - Krzysztof Palczewski
- Department of Ophthalmology, Gavin Herbert Eye Institute, University of California–Irvine, California, USA
- Department of Pharmacology, Case Western Reserve University, Cleveland, Ohio, USA
- Department of Physiology and Biophysics, University of California–Irvine, Irvine, California, USA
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Ehrenberg D, Varma N, Deupi X, Koyanagi M, Terakita A, Schertler GFX, Heberle J, Lesca E. The Two-Photon Reversible Reaction of the Bistable Jumping Spider Rhodopsin-1. Biophys J 2019; 116:1248-1258. [PMID: 30902364 PMCID: PMC6451042 DOI: 10.1016/j.bpj.2019.02.025] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2018] [Revised: 01/16/2019] [Accepted: 02/19/2019] [Indexed: 12/22/2022] Open
Abstract
Bistable opsins are photopigments expressed in both invertebrates and vertebrates. These light-sensitive G-protein-coupled receptors undergo a reversible reaction upon illumination. A first photon initiates the cis to trans isomerization of the retinal chromophore—attached to the protein through a protonated Schiff base—and a series of transition states that eventually results in the formation of the thermally stable and active Meta state. Excitation by a second photon reverts this process to recover the original ground state. On the other hand, monostable opsins (e.g., bovine rhodopsin) lose their chromophore during the decay of the Meta II state (i.e., they bleach). Spectroscopic studies on the molecular details of the two-photon cycle in bistable opsins are limited. Here, we describe the successful expression and purification of recombinant rhodopsin-1 from the jumping spider Hasarius adansoni (JSR1). In its natural configuration, spectroscopic characterization of JSR1 is hampered by the similar absorption spectra in the visible spectrum of the inactive and active states. We solved this issue by separating their absorption spectra by replacing the endogenous 11-cis retinal chromophore with the blue-shifted 9-cis JSiR1. With this system, we used time-resolved ultraviolet-visible spectroscopy after pulsed laser excitation to obtain kinetic details of the rise and decay of the photocycle intermediates. We also used resonance Raman spectroscopy to elucidate structural changes of the retinal chromophore upon illumination. Our data clearly indicate that the protonated Schiff base is stable throughout the entire photoreaction. We additionally show that the accompanying conformational changes in the protein are different from those of monostable rhodopsin, as recorded by light-induced FTIR difference spectroscopy. Thus, we envisage JSR1 as becoming a model system for future studies on the reaction mechanisms of bistable opsins, e.g., by time-resolved x-ray crystallography.
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Affiliation(s)
- David Ehrenberg
- Experimental Molecular Biophysics, Department of Physics, Freie Universität Berlin, Berlin, Germany
| | - Niranjan Varma
- Division of Biology and Chemistry-Laboratory for Biomolecular Research, Paul Scherrer Institute, Villigen, Switzerland; Department of Biology, ETH Zürich, Zürich, Switzerland
| | - Xavier Deupi
- Division of Neutrons and Muons-Laboratory for Scientific Computing and Modelling, Paul Scherrer Institute, Villigen, Switzerland
| | - Mitsumasa Koyanagi
- Department of Biology and Geosciences, Graduate School of Science, Osaka City University, Osaka, Japan
| | - Akihisa Terakita
- Department of Biology and Geosciences, Graduate School of Science, Osaka City University, Osaka, Japan
| | - Gebhard F X Schertler
- Division of Biology and Chemistry-Laboratory for Biomolecular Research, Paul Scherrer Institute, Villigen, Switzerland; Department of Biology, ETH Zürich, Zürich, Switzerland.
| | - Joachim Heberle
- Experimental Molecular Biophysics, Department of Physics, Freie Universität Berlin, Berlin, Germany.
| | - Elena Lesca
- Division of Biology and Chemistry-Laboratory for Biomolecular Research, Paul Scherrer Institute, Villigen, Switzerland; Department of Biology, ETH Zürich, Zürich, Switzerland.
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Abstract
Conformational equilibria of G-protein-coupled receptors (GPCRs) are intimately involved in intracellular signaling. Here conformational substates of the GPCR rhodopsin are investigated in micelles of dodecyl maltoside (DDM) and in phospholipid nanodiscs by monitoring the spatial positions of transmembrane helices 6 and 7 at the cytoplasmic surface using site-directed spin labeling and double electron-electron resonance spectroscopy. The photoactivated receptor in DDM is dominated by one conformation with weak pH dependence. In nanodiscs, however, an ensemble of pH-dependent conformational substates is observed, even at pH 6.0 where the MIIbH+ form defined by proton uptake and optical spectroscopic methods is reported to be the sole species present in native disk membranes. In nanodiscs, the ensemble of substates in the photoactivated receptor spontaneously decays to that characteristic of the inactive state with a lifetime of ∼16 min at 20 °C. Importantly, transducin binding to the activated receptor selects a subset of the ensemble in which multiple substates are apparently retained. The results indicate that in a native-like lipid environment rhodopsin activation is not analogous to a simple binary switch between two defined conformations, but the activated receptor is in equilibrium between multiple conformers that in principle could recognize different binding partners.
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Funatogawa C, Szundi I, Kliger DS. A Comparison between the Photoactivation Kinetics of Human and Bovine Rhodopsins. Biochemistry 2016; 55:7005-7013. [DOI: 10.1021/acs.biochem.6b00953] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Chie Funatogawa
- Department of Chemistry and
Biochemistry, University of California, Santa Cruz, Santa Cruz, California 95064, United States
| | - Istvan Szundi
- Department of Chemistry and
Biochemistry, University of California, Santa Cruz, Santa Cruz, California 95064, United States
| | - David S. Kliger
- Department of Chemistry and
Biochemistry, University of California, Santa Cruz, Santa Cruz, California 95064, United States
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Nosrati M, Berbasova T, Vasileiou C, Borhan B, Geiger JH. A Photoisomerizing Rhodopsin Mimic Observed at Atomic Resolution. J Am Chem Soc 2016; 138:8802-8. [PMID: 27310917 DOI: 10.1021/jacs.6b03681] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The members of the rhodopsin family of proteins are involved in many essential light-dependent processes in biology. Specific photoisomerization of the protein-bound retinylidene PSB at a specified wavelength range of light is at the heart of all of these systems. Nonetheless, it has been difficult to reproduce in an engineered system. We have developed rhodopsin mimics, using intracellular lipid binding protein family members as scaffolds, to study fundamental aspects of protein/chromophore interactions. Herein we describe a system that specifically isomerizes the retinylidene protonated Schiff base both thermally and photochemically. This isomerization has been characterized at atomic resolution by quantitatively interconverting the isomers in the crystal both thermally and photochemically. This event is accompanied by a large pKa change of the imine similar to the pKa changes observed in bacteriorhodopsin and visual opsins during isomerization.
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Affiliation(s)
- Meisam Nosrati
- Department of Chemistry, Michigan State University , East Lansing, Michigan 48824, United States
| | - Tetyana Berbasova
- Department of Chemistry, Michigan State University , East Lansing, Michigan 48824, United States
| | - Chrysoula Vasileiou
- Department of Chemistry, Michigan State University , East Lansing, Michigan 48824, United States
| | - Babak Borhan
- Department of Chemistry, Michigan State University , East Lansing, Michigan 48824, United States
| | - James H Geiger
- Department of Chemistry, Michigan State University , East Lansing, Michigan 48824, United States
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12
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Imamoto Y, Kojima K, Oka T, Maeda R, Shichida Y. Helical rearrangement of photoactivated rhodopsin in monomeric and dimeric forms probed by high-angle X-ray scattering. Photochem Photobiol Sci 2016; 14:1965-73. [PMID: 26293780 DOI: 10.1039/c5pp00175g] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Light-induced helical rearrangement of vertebrate visual rhodopsin was directly monitored by high-angle X-ray scattering (HAXS), ranging from Q (= 4π sin θ/λ) = 0.03 Å(-1) to Q = 1.5 Å(-1). HAXS of nanodiscs containing a single rhodopsin molecule was performed before and after photoactivation of rhodopsin. The intensity difference curve obtained by HAXS agreed with that calculated from the crystal structure of dark state rhodopsin and metarhodopsin II, indicating that the conformational change of monomeric rhodopsin in the membrane is consistent with that occurring in the crystal. On the other hand, the HAXS intensity difference curve of nanodiscs containing two rhodopsin molecules was significantly reduced, similar to that calculated from the crystal structure of the deprotonated intermediate, without a large conformational change. These results suggest that rhodopsin is dimerized in the membrane and that the interaction between rhodopsin molecules modulates structural changes.
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Affiliation(s)
- Yasushi Imamoto
- Department of Biophysics, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan.
| | - Keiichi Kojima
- Department of Biophysics, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan.
| | - Toshihiko Oka
- Department of Physics, Faculty of Science, Shizuoka University, Shizuoka 422-8529, Japan and Nanomaterials Research Division, Research Institute of Electronics, Shizuoka University, Shizuoka 432-8011, Japan
| | - Ryo Maeda
- Department of Biophysics, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan.
| | - Yoshinori Shichida
- Department of Biophysics, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan.
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Chatterjee D, Eckert CE, Slavov C, Saxena K, Fürtig B, Sanders CR, Gurevich VV, Wachtveitl J, Schwalbe H. Influence of Arrestin on the Photodecay of Bovine Rhodopsin. Angew Chem Int Ed Engl 2015; 54:13555-60. [PMID: 26383645 PMCID: PMC4685475 DOI: 10.1002/anie.201505798] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2015] [Revised: 08/11/2015] [Indexed: 11/07/2022]
Abstract
Continued activation of the photocycle of the dim-light receptor rhodopsin leads to the accumulation of all-trans-retinal in the rod outer segments (ROS). This accumulation can damage the photoreceptor cell. For retinal homeostasis, deactivation processes are initiated in which the release of retinal is delayed. One of these processes involves the binding of arrestin to rhodopsin. Here, the interaction of pre-activated truncated bovine visual arrestin (Arr(Tr)) with rhodopsin in 1,2-diheptanoyl-sn-glycero-3-phosphocholine (DHPC) micelles is investigated by solution NMR techniques and flash photolysis spectroscopy. Our results show that formation of the rhodopsin-arrestin complex markedly influences partitioning in the decay kinetics of rhodopsin, which involves the simultaneous formation of a meta II and a meta III state from the meta I state. Binding of Arr(Tr) leads to an increase in the population of the meta III state and consequently to an approximately twofold slower release of all-trans-retinal from rhodopsin.
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Affiliation(s)
- Deep Chatterjee
- Institute of Organic Chemistry and Chemical Biology, Center of Biomolecular Magnetic Resonance (BMRZ), Goethe University Frankfurt/Main, Max-von-Laue-Strasse 7, 60438 Frankfurt am Main (Germany)
| | - Carl Elias Eckert
- Institute of Physical and Theoretical Chemistry, Goethe University Frankfurt/Main, Max-von-Laue-Strasse 7, 60438 Frankfurt am Main (Germany)
| | - Chavdar Slavov
- Institute of Physical and Theoretical Chemistry, Goethe University Frankfurt/Main, Max-von-Laue-Strasse 7, 60438 Frankfurt am Main (Germany)
| | - Krishna Saxena
- Institute of Organic Chemistry and Chemical Biology, Center of Biomolecular Magnetic Resonance (BMRZ), Goethe University Frankfurt/Main, Max-von-Laue-Strasse 7, 60438 Frankfurt am Main (Germany)
| | - Boris Fürtig
- Institute of Organic Chemistry and Chemical Biology, Center of Biomolecular Magnetic Resonance (BMRZ), Goethe University Frankfurt/Main, Max-von-Laue-Strasse 7, 60438 Frankfurt am Main (Germany)
| | - Charles R Sanders
- Department of Biochemistry, Center for Structural Biology, Institute of Chemical Biology, Vanderbilt University School of Medicine, Nashville, TN 37232 (USA)
| | - Vsevolod V Gurevich
- Department of Pharmacology, Vanderbilt University School of Medicine, Nashville, TN 37232 (USA)
| | - Josef Wachtveitl
- Institute of Physical and Theoretical Chemistry, Goethe University Frankfurt/Main, Max-von-Laue-Strasse 7, 60438 Frankfurt am Main (Germany).
| | - Harald Schwalbe
- Institute of Organic Chemistry and Chemical Biology, Center of Biomolecular Magnetic Resonance (BMRZ), Goethe University Frankfurt/Main, Max-von-Laue-Strasse 7, 60438 Frankfurt am Main (Germany).
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14
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Chatterjee D, Eckert CE, Slavov C, Saxena K, Fürtig B, Sanders CR, Gurevich VV, Wachtveitl J, Schwalbe H. Influence of Arrestin on the Photodecay of Bovine Rhodopsin. Angew Chem Int Ed Engl 2015. [DOI: 10.1002/ange.201505798] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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15
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Kubli-Garfias C, Vázquez-Ramírez R, Cabrera-Vivas BM, Gómez-Reyes B, Ramírez JC. Atomic and molecular analysis highlights the biophysics of unprotonated and protonated retinal in UV and scotopic vision. Photochem Photobiol Sci 2015; 14:1660-72. [DOI: 10.1039/c5pp00091b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Unprotonated (UR) and protonated (PR) retinal have marked atomic and molecular differences in cis and trans configurations. In conclusion, UR and PR uphold UV and light vision through their different biophysical properties.
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Affiliation(s)
- Carlos Kubli-Garfias
- Instituto de Investigaciones Biomédicas
- Universidad Nacional Autónoma de México
- México
- Mexico
| | | | | | | | - Juan Carlos Ramírez
- Facultad de Ciencias Químicas
- Benemérita Universidad Autónoma de Puebla
- Puebla 72530
- Mexico
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16
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Sia PI, Luiten AN, Stace TM, Wood JPM, Casson RJ. Quantum biology of the retina. Clin Exp Ophthalmol 2014; 42:582-9. [DOI: 10.1111/ceo.12373] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2014] [Accepted: 06/10/2014] [Indexed: 11/28/2022]
Affiliation(s)
- Paul Ikgan Sia
- South Australian Institute of Ophthalmology; Hanson Institute; University of Adelaide; Adelaide South Australia Australia
| | - André N Luiten
- Institute for Photonics and Advanced Sensing (IPAS); School of Chemistry and Physics; University of Adelaide; Adelaide South Australia Australia
| | - Thomas M Stace
- School of Mathematics and Physics; University of Queensland; Brisbane Queensland Australia
| | - John PM Wood
- South Australian Institute of Ophthalmology; Hanson Institute; University of Adelaide; Adelaide South Australia Australia
| | - Robert J Casson
- South Australian Institute of Ophthalmology; Hanson Institute; University of Adelaide; Adelaide South Australia Australia
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17
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Stehle J, Silvers R, Werner K, Chatterjee D, Gande S, Scholz F, Dutta A, Wachtveitl J, Klein-Seetharaman J, Schwalbe H. Characterization of the simultaneous decay kinetics of metarhodopsin states II and III in rhodopsin by solution-state NMR spectroscopy. Angew Chem Int Ed Engl 2014; 53:2078-84. [PMID: 24505031 DOI: 10.1002/anie.201309581] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2013] [Indexed: 11/09/2022]
Abstract
The mammalian visual dim-light photoreceptor rhodopsin is considered a prototype G protein-coupled receptor. Here, we characterize the kinetics of its light-activation process. Milligram quantities of α,ε-(15)N-labeled tryptophan rhodopsin were produced in stably transfected HEK293 cells. Assignment of the chemical shifts of the indole signals was achieved by generating the single-point-tryptophan to phenylalanine mutants, and the kinetics of each of the five tryptophan residues were recorded. We find kinetic partitioning in rhodopsin decay, including three half-lives, that reveal two parallel processes subsequent to rhodopsin activation that are related to the photocycle. The meta II and meta III states emerge in parallel with a relative ratio of about 3:1. Transient formation of the meta III state was confirmed by flash photolysis experiments. From analysis of the site-resolved kinetic data we propose the involvement of the E2 -loop in the formation of the meta III state.
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Affiliation(s)
- Jochen Stehle
- Institute for Organic Chemistry and Chemical Biology, Center of Biomolecular Magnetic Resonance, Johann Wolfgang Goethe-University Frankfurt, Max-von-Laue-Strasse 7, 60438 Frankfurt am Main (Germany)
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18
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Stehle J, Silvers R, Werner K, Chatterjee D, Gande S, Scholz F, Dutta A, Wachtveitl J, Klein-Seetharaman J, Schwalbe H. Characterization of the Simultaneous Decay Kinetics of Metarhodopsin States II and III in Rhodopsin by Solution-State NMR Spectroscopy. Angew Chem Int Ed Engl 2014. [DOI: 10.1002/ange.201309581] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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19
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Ernst OP, Lodowski DT, Elstner M, Hegemann P, Brown L, Kandori H. Microbial and animal rhodopsins: structures, functions, and molecular mechanisms. Chem Rev 2014; 114:126-63. [PMID: 24364740 PMCID: PMC3979449 DOI: 10.1021/cr4003769] [Citation(s) in RCA: 785] [Impact Index Per Article: 78.5] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2013] [Indexed: 12/31/2022]
Affiliation(s)
- Oliver P. Ernst
- Departments
of Biochemistry and Molecular Genetics, University of Toronto, 1 King’s College Circle, Medical Sciences Building, Toronto, Ontario M5S 1A8, Canada
| | - David T. Lodowski
- Center
for Proteomics and Bioinformatics, Case
Western Reserve University School of Medicine, 10900 Euclid Avenue, Cleveland, Ohio 44106, United States
| | - Marcus Elstner
- Institute
for Physical Chemistry, Karlsruhe Institute
of Technology, Kaiserstrasse
12, 76131 Karlsruhe, Germany
| | - Peter Hegemann
- Institute
of Biology, Experimental Biophysics, Humboldt-Universität
zu Berlin, Invalidenstrasse
42, 10115 Berlin, Germany
| | - Leonid
S. Brown
- Department
of Physics and Biophysics Interdepartmental Group, University of Guelph, 50 Stone Road East, Guelph, Ontario N1G 2W1, Canada
| | - Hideki Kandori
- Department
of Frontier Materials, Nagoya Institute
of Technology, Showa-ku, Nagoya 466-8555, Japan
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20
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Sato K, Yamashita T, Imamoto Y, Shichida Y. Comparative Studies on the Late Bleaching Processes of Four Kinds of Cone Visual Pigments and Rod Visual Pigment. Biochemistry 2012; 51:4300-8. [DOI: 10.1021/bi3000885] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Keita Sato
- Department of Biophysics,
Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
| | - Takahiro Yamashita
- Department of Biophysics,
Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
| | - Yasushi Imamoto
- Department of Biophysics,
Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
| | - Yoshinori Shichida
- Department of Biophysics,
Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
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21
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Lomonosova E, Kolesnikov AV, Kefalov VJ, Kisselev OG. Signaling states of rhodopsin in rod disk membranes lacking transducin βγ-complex. Invest Ophthalmol Vis Sci 2012; 53:1225-33. [PMID: 22266510 DOI: 10.1167/iovs.11-9350] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE To characterize the possible role of transducin Gtβγ-complex in modulating the signaling properties of photoactivated rhodopsin and its lifetime in rod disc membranes and intact rods. METHODS Rhodopsin photolysis was studied using UV-visible spectroscopy and rapid scanning spectroscopy in the presence of hydroxylamine in highly purified wild-type and Gtγ-deficient mouse rod disc membranes. Complex formation between photoactivated rhodopsin and transducin was measured by extra-metarhodopsin (meta) II assay. Recovery of dark current and flash sensitivity in individual intact wild-type and Gtγ-deficient mouse rods was measured by single-cell suction recordings. RESULTS Photoconversion of rhodopsin to meta I/meta II equilibrium proceeds normally after elimination of the Gtβγ-complex. The meta I/meta II ratio, the rate of meta II decay, the reactivity of meta II toward hydroxylamine, and the rate of meta III formation in Gtγ-deficient rod disc membranes were identical with those observed in wild-type samples. Under low-intensity illumination, the amount of extra-meta II in Gtγ-deficient discs was significantly reduced. The initial rate of dark current recovery after 12% rhodopsin bleach was three times faster in Gtγ-deficient rods, whereas the rate of the late current recovery was largely unchanged. Mutant rods also exhibited faster postbleach recovery of flash sensitivity. CONCLUSIONS Photoactivation and thermal decay of rhodopsin proceed similarly in wild-type and Gtγ-deficient mouse rods, but the complex formation between photoactivated rhodopsin and transducin is severely compromised in the absence of Gtβγ. The resultant lower transduction activation contributes to faster photoresponse recovery after a moderate pigment bleach in Gtγ-deficient rods.
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Affiliation(s)
- Elena Lomonosova
- Department of Ophthalmology, Saint Louis University School of Medicine, Saint Louis, MO, USA
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22
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Quaroni L, Zlateva T, Normand E. Detection of Weak Absorption Changes from Molecular Events in Time-Resolved FT-IR Spectromicroscopy Measurements of Single Functional Cells. Anal Chem 2011; 83:7371-80. [DOI: 10.1021/ac201318z] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
- Luca Quaroni
- Swiss Light Source, Paul Scherrer Institut, 5232, Villigen-PSI, Switzerland
| | - Theodora Zlateva
- Department of Biochemistry and Cancer Research Center, University of Saskatchewan, Saskatoon, SK, S7N 5E5, Canada
| | - Elise Normand
- Canadian Light Source Inc., University of Saskatchewan, Saskatoon, SK, S7N 0X4, Canada
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23
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Piechnick R, Heck M, Sommer ME. Alkylated hydroxylamine derivatives eliminate peripheral retinylidene Schiff bases but cannot enter the retinal binding pocket of light-activated rhodopsin. Biochemistry 2011; 50:7168-76. [PMID: 21766795 DOI: 10.1021/bi200675y] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Besides Lys-296 in the binding pocket of opsin, all-trans-retinal forms adducts with peripheral lysine residues and phospholipids, thereby mimicking the spectral and chemical properties of metarhodopsin species. These pseudophotoproducts composed of nonspecific retinylidene Schiff bases have long plagued the investigation of rhodopsin deactivation and identification of decay products. We discovered that, while hydroxylamine can enter the retinal binding pocket of light-activated rhodopsin, the modified hydroxylamine compounds o-methylhydroxylamine (mHA), o-ethylhydroxylamine (eHA), o-tert-butylhydroxylamine (t-bHA), and o-(carboxymethyl)hydroxylamine (cmHA) are excluded. However, the alkylated hydroxylamines react quickly and efficiently with exposed retinylidene Schiff bases to form their respective retinal oximes. We further investigated how t-bHA affects light-activated rhodopsin and its interaction with binding partners. We found that both metarhodopsin II (Meta II) and Meta III are resistant to t-bHA, and neither arrestin nor transducin binding is affected by t-bHA. This discovery suggests that the hypothetical solvent channel that opens in light-activated rhodopsin is extremely stringent with regard to size and/or polarity. We believe that alkylated hydroxylamines will prove to be extremely useful reagents for the investigation of rhodopsin activation and decay mechanisms. Furthermore, the use of alkylated hydroxylamines should not be limited to in vitro studies and could help elucidate visual signal transduction mechanisms in the living cells of the retina.
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Affiliation(s)
- Ronny Piechnick
- Institut für Medizinische Physik und Biophysik (CC2), Charité-Universitätsmedizin Berlin, Charitéplatz 1, D-10117 Berlin, Germany
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24
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Tarttelin EE, Fransen MP, Edwards PC, Hankins MW, Schertler GFX, Vogel R, Lucas RJ, Bellingham J. Adaptation of pineal expressed teleost exo-rod opsin to non-image forming photoreception through enhanced Meta II decay. Cell Mol Life Sci 2011; 68:3713-23. [PMID: 21416149 PMCID: PMC3203999 DOI: 10.1007/s00018-011-0665-y] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2010] [Revised: 02/01/2011] [Accepted: 03/01/2011] [Indexed: 12/03/2022]
Abstract
Photoreception by vertebrates enables both image-forming vision and non-image-forming responses such as circadian photoentrainment. Over the recent years, distinct non-rod non-cone photopigments have been found to support circadian photoreception in diverse species. By allowing specialization to this sensory task a selective advantage is implied, but the nature of that specialization remains elusive. We have used the presence of distinct rod opsin genes specialized to either image-forming (retinal rod opsin) or non-image-forming (pineal exo-rod opsin) photoreception in ray-finned fish (Actinopterygii) to gain a unique insight into this problem. A comparison of biochemical features for these paralogous opsins in two model teleosts, Fugu pufferfish (Takifugu rubripes) and zebrafish (Danio rerio), reveals striking differences. While spectral sensitivity is largely unaltered by specialization to the pineal environment, in other aspects exo-rod opsins exhibit a behavior that is quite distinct from the cardinal features of the rod opsin family. While they display a similar thermal stability, they show a greater than tenfold reduction in the lifetime of the signaling active Meta II photoproduct. We show that these features reflect structural changes in retinal association domains of helices 3 and 5 but, interestingly, not at either of the two residues known to define these characteristics in cone opsins. Our findings suggest that the requirements of non-image-forming photoreception have lead exo-rod opsin to adopt a characteristic that seemingly favors efficient bleach recovery but not at the expense of absolute sensitivity.
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Affiliation(s)
- Emma E Tarttelin
- Faculty of Life Sciences, The University of Manchester, Manchester, UK
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25
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Deupi X, Kobilka BK. Energy landscapes as a tool to integrate GPCR structure, dynamics, and function. Physiology (Bethesda) 2011; 25:293-303. [PMID: 20940434 DOI: 10.1152/physiol.00002.2010] [Citation(s) in RCA: 194] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
G protein-coupled receptors (GPCRs) are versatile signaling molecules that mediate the majority of physiological responses to hormones and neurotransmitters. Recent high-resolution structural insights into GPCR structure and dynamics are beginning to shed light on the molecular basis of this versatility. We use energy landscapes to conceptualize the link between structure and function.
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Affiliation(s)
- Xavier Deupi
- Unitat de Bioestadística, Facultat de Medicina, Universitat Autònoma de Barcelona, Catalunya, Spain.
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26
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Krebs MP, Holden DC, Joshi P, Clark CL, Lee AH, Kaushal S. Molecular mechanisms of rhodopsin retinitis pigmentosa and the efficacy of pharmacological rescue. J Mol Biol 2009; 395:1063-78. [PMID: 19913029 DOI: 10.1016/j.jmb.2009.11.015] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2009] [Revised: 11/05/2009] [Accepted: 11/05/2009] [Indexed: 11/24/2022]
Abstract
Variants of rhodopsin, a complex of 11-cis retinal and opsin, cause retinitis pigmentosa (RP), a degenerative disease of the retina. Trafficking defects due to rhodopsin misfolding have been proposed as the most likely basis of the disease, but other potentially overlapping mechanisms may also apply. Pharmacological therapies for RP must target the major disease mechanism and contend with overlap, if it occurs. To this end, we have explored the molecular basis of rhodopsin RP in the context of pharmacological rescue with 11-cis retinal. Stable inducible cell lines were constructed to express wild-type opsin; the pathogenic variants T4R, T17M, P23A, P23H, P23L, and C110Y; or the nonpathogenic variants F220L and A299S. Pharmacological rescue was measured as the fold increase in rhodopsin or opsin levels upon addition of 11-cis retinal during opsin expression. Only Pro23 and T17M variants were rescued significantly. C110Y opsin was produced at low levels and did not yield rhodopsin, whereas the T4R, F220L, and A299S proteins reached near-wild-type levels and changed little with 11-cis retinal. All of the mutant rhodopsins exhibited misfolding, which increased over a broad range in the order F220L, A299S, T4R, T17M, P23A, P23H, P23L, as determined by decreased thermal stability in the dark and increased hydroxylamine sensitivity. Pharmacological rescue increased as misfolding decreased, but was limited for the least misfolded variants. Significantly, pathogenic variants also showed abnormal photobleaching behavior, including an increased ratio of metarhodopsin-I-like species to metarhodopsin-II-like species and aberrant photoproduct accumulation with prolonged illumination. These results, combined with an analysis of published biochemical and clinical studies, suggest that many rhodopsin variants cause disease by affecting both biosynthesis and photoactivity. We conclude that pharmacological rescue is promising as a broadly effective therapy for rhodopsin RP, particularly if implemented in a way that minimizes the photoactivity of the mutant proteins.
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Affiliation(s)
- Mark P Krebs
- Department of Ophthalmology and the Charlie Mack Overstreet Laboratories for Retinal Diseases, College of Medicine, University of Florida, Gainesville, FL 32610, USA
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27
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Hoersch D, Otto H, Wallat I, Heyn MP. Monitoring the Conformational Changes of Photoactivated Rhodopsin from Μicroseconds to Seconds by Transient Fluorescence Spectroscopy. Biochemistry 2008; 47:11518-27. [DOI: 10.1021/bi801397e] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Daniel Hoersch
- Biophysics Group, Department of Physics, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
| | - Harald Otto
- Biophysics Group, Department of Physics, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
| | - Ingrid Wallat
- Biophysics Group, Department of Physics, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
| | - Maarten P. Heyn
- Biophysics Group, Department of Physics, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
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28
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Imamoto Y, Shichida Y. Thermal Recovery of Iodopsin from Photobleaching Intermediates. Photochem Photobiol 2008; 84:941-8. [DOI: 10.1111/j.1751-1097.2008.00332.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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29
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30
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Crystal structure of the ligand-free G-protein-coupled receptor opsin. Nature 2008; 454:183-7. [PMID: 18563085 DOI: 10.1038/nature07063] [Citation(s) in RCA: 719] [Impact Index Per Article: 44.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2008] [Accepted: 05/09/2008] [Indexed: 01/02/2023]
Abstract
In the G-protein-coupled receptor (GPCR) rhodopsin, the inactivating ligand 11-cis-retinal is bound in the seven-transmembrane helix (TM) bundle and is cis/trans isomerized by light to form active metarhodopsin II. With metarhodopsin II decay, all-trans-retinal is released, and opsin is reloaded with new 11-cis-retinal. Here we present the crystal structure of ligand-free native opsin from bovine retinal rod cells at 2.9 ångström (A) resolution. Compared to rhodopsin, opsin shows prominent structural changes in the conserved E(D)RY and NPxxY(x)(5,6)F regions and in TM5-TM7. At the cytoplasmic side, TM6 is tilted outwards by 6-7 A, whereas the helix structure of TM5 is more elongated and close to TM6. These structural changes, some of which were attributed to an active GPCR state, reorganize the empty retinal-binding pocket to disclose two openings that may serve the entry and exit of retinal. The opsin structure sheds new light on ligand binding to GPCRs and on GPCR activation.
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31
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Slepak VZ, Hurley JB. Mechanism of light-induced translocation of arrestin and transducin in photoreceptors: interaction-restricted diffusion. IUBMB Life 2008; 60:2-9. [PMID: 18379987 DOI: 10.1002/iub.7] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Many signaling proteins change their location within cells in response to external stimuli. In photoreceptors, this phenomenon is remarkably robust. The G protein of rod photoreceptors and rod transducin concentrates in the outer segments (OS) of these neurons in darkness. Within approximately 30 minutes after illumination, rod transducin redistributes throughout all of the outer and inner compartments of the cell. Visual arrestin concurrently relocalises from the inner compartments to become sequestered primarily within the OS. In the past several years, the question of whether these proteins are actively moved by molecular motors or whether they are redistributed by simple diffusion has been extensively debated. This review focuses on the most essential works in the area and concludes that the basic principle driving this protein movement is diffusion. The directionality and light dependence of this movement is achieved by the interactions of arrestin and transducin with their spatially restricted binding partners.
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Affiliation(s)
- Vladlen Z Slepak
- Department of Molecular and Cellular Pharmacology and Neuroscience Program, University of Miami Miller School of Medicine, Miami, FL, USA.
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32
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Standfuss J, Zaitseva E, Mahalingam M, Vogel R. Structural impact of the E113Q counterion mutation on the activation and deactivation pathways of the G protein-coupled receptor rhodopsin. J Mol Biol 2008; 380:145-57. [PMID: 18511075 PMCID: PMC2726285 DOI: 10.1016/j.jmb.2008.04.055] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2007] [Revised: 03/12/2008] [Accepted: 04/21/2008] [Indexed: 11/16/2022]
Abstract
Disruption of an interhelical salt bridge between the retinal protonated Schiff base linked to H7 and Glu113 on H3 is one of the decisive steps during activation of rhodopsin. Using previously established stabilization strategies, we engineered a stabilized E113Q counterion mutant that converted rhodopsin to a UV-absorbing photoreceptor with deprotonated Schiff base and allowed reconstitution into native-like lipid membranes. Fourier-transform infrared difference spectroscopy reveals a deprotonated Schiff base in the photoproducts of the mutant up to the active state Meta II, the absence of the classical pH-dependent Meta I/Meta II conformational equilibrium in favor of Meta II, and an anticipation of active state features under conditions that stabilize inactive photoproduct states in wildtype rhodopsin. Glu181 on extracellular loop 2, is found to be unable to maintain a counterion function to the Schiff base on the activation pathway of rhodopsin in the absence of the primary counterion, Glu113. The Schiff base becomes protonated in the transition to Meta III. This protonation is, however, not associated with a deactivation of the receptor, in contrast to wildtype rhodopsin. Glu181 is suggested to be the counterion in the Meta III state of the mutant and appears to be capable of stabilizing a protonated Schiff base in Meta III, but not of constraining the receptor in an inactive conformation.
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Affiliation(s)
- Jörg Standfuss
- Structural Studies Division, MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 0QH, UK
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