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Estarellas C, Scaffidi S, Saladino G, Spyrakis F, Franzoni L, Galdeano C, Bidon-Chanal A, Gervasio FL, Luque FJ. Modulating Ligand Dissociation through Methyl Isomerism in Accessory Sites: Binding of Retinol to Cellular Carriers. J Phys Chem Lett 2019; 10:7333-7339. [PMID: 31714784 DOI: 10.1021/acs.jpclett.9b02861] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Due to the poor aqueous solubility of retinoids, evolution has tuned their binding to cellular proteins to address specialized physiological roles by modulating uptake, storage, and delivery to specific targets. With the aim to disentangle the structure-function relationships in these proteins and disclose clues for engineering selective carriers, the binding mechanism of the two most abundant retinol-binding isoforms was explored by using enhanced sampling molecular dynamics simulations and surface plasmon resonance. The distinctive dynamics of the entry portal site in the holo species was crucial to modulate retinol dissociation. Remarkably, this process is controlled to a large extent by the replacement of Ile by Leu in the two isoforms, thus suggesting that fine control of ligand release can be achieved through a rigorous selection of conservative mutations in accessory sites.
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Affiliation(s)
- Carolina Estarellas
- Department of Nutrition, Food Science and Gastronomy, Faculty of Pharmacy and Food Sciences, Institute of Biomedicine (IBUB) and Institute of Theoretical and Computational Chemistry (IQTCUB) , University of Barcelona , 08921 Santa Coloma de Gramenet , Spain
- Department of Chemistry , University College London , London WC1E 6BT , United Kingdom
| | - Salvatore Scaffidi
- Department of Pharmacy, Pharmaceutical Technology, and Physical Chemistry, Faculty of Pharmacy and Food Science, and Institute of Biomedicine (IBUB) , University of Barcelona , 08028 Barcelona , Spain
| | - Giorgio Saladino
- Department of Chemistry , University College London , London WC1E 6BT , United Kingdom
| | - Francesca Spyrakis
- Department of Drug Science and Technology , University of Turin , 10125 Turin , Italy
| | - Lorella Franzoni
- Department of Biomedical, Biotechnological and Translational Sciences , University of Parma , 43121 Parma , Italy
| | - Carles Galdeano
- Department of Pharmacy, Pharmaceutical Technology, and Physical Chemistry, Faculty of Pharmacy and Food Science, and Institute of Biomedicine (IBUB) , University of Barcelona , 08028 Barcelona , Spain
| | - Axel Bidon-Chanal
- Department of Nutrition, Food Science and Gastronomy, Faculty of Pharmacy and Food Sciences, Institute of Biomedicine (IBUB) and Institute of Theoretical and Computational Chemistry (IQTCUB) , University of Barcelona , 08921 Santa Coloma de Gramenet , Spain
| | | | - F Javier Luque
- Department of Nutrition, Food Science and Gastronomy, Faculty of Pharmacy and Food Sciences, Institute of Biomedicine (IBUB) and Institute of Theoretical and Computational Chemistry (IQTCUB) , University of Barcelona , 08921 Santa Coloma de Gramenet , Spain
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Structural insights on cholesterol endosynthesis: Binding of squalene and 2,3-oxidosqualene to supernatant protein factor. J Struct Biol 2015; 190:261-70. [DOI: 10.1016/j.jsb.2015.05.001] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2015] [Revised: 05/08/2015] [Accepted: 05/11/2015] [Indexed: 11/24/2022]
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Palczewski K. Chemistry and biology of the initial steps in vision: the Friedenwald lecture. Invest Ophthalmol Vis Sci 2014; 55:6651-72. [PMID: 25338686 DOI: 10.1167/iovs.14-15502] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Visual transduction is the process in the eye whereby absorption of light in the retina is translated into electrical signals that ultimately reach the brain. The first challenge presented by visual transduction is to understand its molecular basis. We know that maintenance of vision is a continuous process requiring the activation and subsequent restoration of a vitamin A-derived chromophore through a series of chemical reactions catalyzed by enzymes in the retina and retinal pigment epithelium (RPE). Diverse biochemical approaches that identified key proteins and reactions were essential to achieve a mechanistic understanding of these visual processes. The three-dimensional arrangements of these enzymes' polypeptide chains provide invaluable insights into their mechanisms of action. A wealth of information has already been obtained by solving high-resolution crystal structures of both rhodopsin and the retinoid isomerase from pigment RPE (RPE65). Rhodopsin, which is activated by photoisomerization of its 11-cis-retinylidene chromophore, is a prototypical member of a large family of membrane-bound proteins called G protein-coupled receptors (GPCRs). RPE65 is a retinoid isomerase critical for regeneration of the chromophore. Electron microscopy (EM) and atomic force microscopy have provided insights into how certain proteins are assembled to form much larger structures such as rod photoreceptor cell outer segment membranes. A second challenge of visual transduction is to use this knowledge to devise therapeutic approaches that can prevent or reverse conditions leading to blindness. Imaging modalities like optical coherence tomography (OCT) and scanning laser ophthalmoscopy (SLO) applied to appropriate animal models as well as human retinal imaging have been employed to characterize blinding diseases, monitor their progression, and evaluate the success of therapeutic agents. Lately two-photon (2-PO) imaging, together with biochemical assays, are revealing functional aspects of vision at a new molecular level. These multidisciplinary approaches combined with suitable animal models and inbred mutant species can be especially helpful in translating provocative cell and tissue culture findings into therapeutic options for further development in animals and eventually in humans. A host of different approaches and techniques is required for substantial progress in understanding fundamental properties of the visual system.
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Affiliation(s)
- Krzysztof Palczewski
- Department of Pharmacology, Cleveland Center for Membrane and Structural Biology, School of Medicine, Case Western Reserve University, Cleveland, Ohio, United States
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Bolze CS, Helbling RE, Owen RL, Pearson AR, Pompidor G, Dworkowski F, Fuchs MR, Furrer J, Golczak M, Palczewski K, Cascella M, Stocker A. Human cellular retinaldehyde-binding protein has secondary thermal 9-cis-retinal isomerase activity. J Am Chem Soc 2013; 136:137-46. [PMID: 24328211 DOI: 10.1021/ja411366w] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Cellular retinaldehyde-binding protein (CRALBP) chaperones 11-cis-retinal to convert opsin receptor molecules into photosensitive retinoid pigments of the eye. We report a thermal secondary isomerase activity of CRALBP when bound to 9-cis-retinal. UV/vis and (1)H NMR spectroscopy were used to characterize the product as 9,13-dicis-retinal. The X-ray structure of the CRALBP mutant R234W:9-cis-retinal complex at 1.9 Å resolution revealed a niche in the binding pocket for 9-cis-aldehyde different from that reported for 11-cis-retinal. Combined computational, kinetic, and structural data lead us to propose an isomerization mechanism catalyzed by a network of buried waters. Our findings highlight a specific role of water molecules in both CRALBP-assisted specificity toward 9-cis-retinal and its thermal isomerase activity yielding 9,13-dicis-retinal. Kinetic data from two point mutants of CRALBP support an essential role of Glu202 as the initial proton donor in this isomerization reaction.
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Affiliation(s)
- Christin S Bolze
- Department of Chemistry and Biochemistry, and ‡Graduate School for Cellular and Biomedical Sciences, University of Bern , Freiestrasse 3, 3012 Bern, Switzerland
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Cascella M, Bärfuss S, Stocker A. Cis-retinoids and the chemistry of vision. Arch Biochem Biophys 2013; 539:187-95. [PMID: 23791723 DOI: 10.1016/j.abb.2013.06.003] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2013] [Revised: 06/04/2013] [Accepted: 06/10/2013] [Indexed: 11/17/2022]
Abstract
We discuss here principal biochemical transformations of retinoid molecules in the visual cycle. We focus our analysis on the accumulating evidence of alternate pathways and functional redundancies in the cycle. The efficiency of the visual cycle depends, on one hand, on fast regeneration of the photo-bleached chromophores. On the other hand, it is crucial that the cyclic process should be highly selective to avoid accumulation of byproducts. The state-of-the-art knowledge indicates that single enzymatically active components of the cycle are not strictly selective and may require chaperones to enhance their rates. It appears that protein-protein interactions significantly improve the biological stability of the visual cycle. In particular, synthesis of thermodynamically less stable 11-cis-retinoid conformers is favored by physical interactions of the isomerases present in the retina with cellular retinaldehyde binding protein.
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Affiliation(s)
- Michele Cascella
- Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, 3012 Bern, Switzerland.
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