1
|
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: 11] [Impact Index Per Article: 11.0] [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.
Collapse
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.
| |
Collapse
|
2
|
MacDonell RJ, Patchkovskii S, Schuurman MS. A Comparison of Partial Atomic Charges for Electronically Excited States. J Chem Theory Comput 2022; 18:1061-1071. [PMID: 35015528 DOI: 10.1021/acs.jctc.1c01101] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Partial atomic charges are a useful and intuitive concept for understanding molecular properties and chemical reaction mechanisms, showing how changes in molecular geometry can affect the flow of electronic charge within a molecule. However, the use of partial atomic charges remains relatively uncommon in the characterization of excited-state electronic structure. Here, we show how well-established partial atomic charge methods perform for interatomic, intermolecular, and interbond electron transfer in electronically excited states. Our results demonstrate the utility of real-space partial atomic charges for interpreting the electronic structures that arise in excited-state processes. Furthermore, we show how this analysis can be used to demonstrate that analogous electronic structures arise near photochemically relevant conical intersection regions for several conjugated polyenes. On the basis of our analysis, we find that charges computed using the iterative Hirshfeld approach provide results which are consistent with chemical intuition and are transferable between homologous molecular systems.
Collapse
Affiliation(s)
- Ryan J MacDonell
- Department of Chemistry and Biomolecular Sciences, University of Ottawa, Ottawa, Ontario K1N 6N5, Canada
| | - Serguei Patchkovskii
- Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie, Max-Born-Straße 2A, 12489 Berlin, Germany
| | - Michael S Schuurman
- Department of Chemistry and Biomolecular Sciences, University of Ottawa, Ottawa, Ontario K1N 6N5, Canada.,National Research Council of Canada, 100 Sussex Drive, Ottawa, Ontario K1A 0R6, Canada
| |
Collapse
|
3
|
Sinha B, Goswami T, Paul S, Misra A. Spectral tuning of 11-cis retinal in conjugation with Au14 cluster and concomitant effect on isomerization: A theoretical outlook. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY 2021. [DOI: 10.1016/j.jpap.2021.100051] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
|
4
|
Mushtaq AU, Ådén J, Clifton LA, Wacklin-Knecht H, Campana M, Dingeldein APG, Persson C, Sparrman T, Gröbner G. Neutron reflectometry and NMR spectroscopy of full-length Bcl-2 protein reveal its membrane localization and conformation. Commun Biol 2021; 4:507. [PMID: 33907308 PMCID: PMC8079415 DOI: 10.1038/s42003-021-02032-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2020] [Accepted: 03/25/2021] [Indexed: 12/20/2022] Open
Abstract
B-cell lymphoma 2 (Bcl-2) proteins are the main regulators of mitochondrial apoptosis. Anti-apoptotic Bcl-2 proteins possess a hydrophobic tail-anchor enabling them to translocate to their target membrane and to shift into an active conformation where they inhibit pro-apoptotic Bcl-2 proteins to ensure cell survival. To address the unknown molecular basis of their cell-protecting functionality, we used intact human Bcl-2 protein natively residing at the mitochondrial outer membrane and applied neutron reflectometry and NMR spectroscopy. Here we show that the active full-length protein is entirely buried into its target membrane except for the regulatory flexible loop domain (FLD), which stretches into the aqueous exterior. The membrane location of Bcl-2 and its conformational state seems to be important for its cell-protecting activity, often infamously upregulated in cancers. Most likely, this situation enables the Bcl-2 protein to sequester pro-apoptotic Bcl-2 proteins at the membrane level while sensing cytosolic regulative signals via its FLD region.
Collapse
Affiliation(s)
| | - Jörgen Ådén
- Department of Chemistry, University of Umeå, Umeå, Sweden
| | - Luke A Clifton
- ISIS Pulsed Neutron and Muon Source, Science and Technology Facilities Council, Rutherford Appleton Laboratory, Harwell Science&Innovation Campus, Didcot, Oxfordshire, UK
| | - Hanna Wacklin-Knecht
- European Spallation Source ERIC, ESS, Lund, Sweden
- Department of Chemistry, Division of Physical Chemistry, Lund University, Lund, Sweden
| | - Mario Campana
- ISIS Pulsed Neutron and Muon Source, Science and Technology Facilities Council, Rutherford Appleton Laboratory, Harwell Science&Innovation Campus, Didcot, Oxfordshire, UK
| | | | - Cecilia Persson
- The Swedish NMR Center, University of Gothenburg, Gothenburg, Sweden
| | | | | |
Collapse
|
5
|
Insight into Functional Membrane Proteins by Solution NMR: The Human Bcl-2 Protein-A Promising Cancer Drug Target. Molecules 2021; 26:molecules26051467. [PMID: 33800399 PMCID: PMC7962812 DOI: 10.3390/molecules26051467] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2021] [Revised: 02/26/2021] [Accepted: 03/04/2021] [Indexed: 11/17/2022] Open
Abstract
Evasion from programmed cell death (apoptosis) is the main hallmark of cancer and a major cause of resistance to therapy. Many tumors simply ensure survival by over-expressing the cell-protecting (anti-apoptotic) Bcl-2 membrane protein involved in apoptotic regulation. However, the molecular mechanism by which Bcl-2 protein in its mitochondrial outer membrane location protects cells remains elusive due to the absence of structural insight; and current strategies to therapeutically interfere with these Bcl-2 sensitive cancers are limited. Here, we present an NMR-based approach to enable structural insight into Bcl-2 function; an approach also ideal as a fragment-based drug discovery platform for further identification and development of promising molecular Bcl-2 inhibitors. By using solution NMR spectroscopy on fully functional intact human Bcl-2 protein in a membrane-mimicking micellar environment, and constructs with specific functions remaining, we present a strategy for structure determination and specific drug screening of functional subunits of the Bcl-2 protein as targets. Using 19F NMR and a specific fragment library (Bionet) with fluorinated compounds we can successfully identify various binders and validate our strategy in the hunt for novel Bcl-2 selective cancer drug strategies to treat currently incurable Bcl-2 sensitive tumors.
Collapse
|
6
|
Structural biology of human GPCR drugs and endogenous ligands - insights from NMR spectroscopy. Methods 2020; 180:79-88. [PMID: 32911074 DOI: 10.1016/j.ymeth.2020.08.008] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2020] [Revised: 08/30/2020] [Accepted: 08/31/2020] [Indexed: 12/13/2022] Open
Abstract
G protein-coupled receptors (GPCRs) represent the largest class of "druggable" proteins in the human genome. For more than a decade, crystal structures and, more recently, cryoEM structures of GPCR complexes have provided unprecedented insight into GPCR drug binding and cell signaling. Nevertheless, structure determination of receptors in complexes with weakly binding molecules or complex polypeptides remains especially challenging, including for hormones, many of which have so far eluded researchers. Nuclear magnetic resonance (NMR) spectroscopy has emerged as a promising approach to determine structures of ligands bound to their receptors and to provide insights into the dynamics of GPCR-bound drugs. The capability to investigate compounds with weak binding affinities has also been leveraged in NMR applications to identify novel lead compounds in drug screening campaigns. We review recent structural biology studies of GPCR ligands by NMR, highlighting new methodologies enabling studies of GPCRs with native sequences and in native-like membrane environments that provide insights into important drugs and endogenous ligands.
Collapse
|
7
|
Jirasko V, Lakomek N, Penzel S, Fogeron M, Bartenschlager R, Meier BH, Böckmann A. Proton-Detected Solid-State NMR of the Cell-Free Synthesized α-Helical Transmembrane Protein NS4B from Hepatitis C Virus. Chembiochem 2020; 21:1453-1460. [PMID: 31850615 PMCID: PMC7318649 DOI: 10.1002/cbic.201900765] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2019] [Indexed: 01/01/2023]
Abstract
Proton-detected 100 kHz magic-angle-spinning (MAS) solid-state NMR is an emerging analysis method for proteins with only hundreds of microgram quantities, and thus allows structural investigation of eukaryotic membrane proteins. This is the case for the cell-free synthesized hepatitis C virus (HCV) nonstructural membrane protein 4B (NS4B). We demonstrate NS4B sample optimization using fast reconstitution schemes that enable lipid-environment screening directly by NMR. 2D spectra and relaxation properties guide the choice of the best sample preparation to record 2D 1 H-detected 1 H,15 N and 3D 1 H,13 C,15 N correlation experiments with linewidths and sensitivity suitable to initiate sequential assignments. Amino-acid-selectively labeled NS4B can be readily obtained using cell-free synthesis, opening the door to combinatorial labeling approaches which should enable structural studies.
Collapse
Affiliation(s)
- Vlastimil Jirasko
- ETH ZürichPhysical ChemistryVladimir-Prelog Weg 28093ZürichSwitzerland
| | | | - Susanne Penzel
- ETH ZürichPhysical ChemistryVladimir-Prelog Weg 28093ZürichSwitzerland
| | - Marie‐Laure Fogeron
- Institut de Biologie et Chimie des ProteinesMMSBLabex EcofectUMR 5086 CNRSUniversité de Lyon7 passage du Vercors69367LyonFrance
| | - Ralf Bartenschlager
- Department of Infectious DiseasesMolecular VirologyHeidelberg UniversityIm Neuenheimer Feld 34569120HeidelbergGermany
- Division of Virus-Associated Carcinogenesis (Germany)Cancer Research Center (DKFZ)Im Neuenheimer Feld 24269120HeidelbergGermany
| | - Beat H. Meier
- ETH ZürichPhysical ChemistryVladimir-Prelog Weg 28093ZürichSwitzerland
| | - Anja Böckmann
- Institut de Biologie et Chimie des ProteinesMMSBLabex EcofectUMR 5086 CNRSUniversité de Lyon7 passage du Vercors69367LyonFrance
| |
Collapse
|
8
|
MacDonell RJ, Corrales ME, Boguslavskiy AE, Bañares L, Stolow A, Schuurman MS. Substituent effects on nonadiabatic excited state dynamics: Inertial, steric, and electronic effects in methylated butadienes. J Chem Phys 2020; 152:084308. [DOI: 10.1063/1.5139446] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Affiliation(s)
- Ryan J. MacDonell
- Department of Chemistry and Biomolecular Sciences, University of Ottawa, Ottawa, Ontario K1N 6N5, Canada
| | - María E. Corrales
- Departamento de Química Física, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, 28040 Madrid, Spain
| | | | - Luis Bañares
- Departamento de Química Física, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, 28040 Madrid, Spain
| | - Albert Stolow
- Department of Chemistry and Biomolecular Sciences, University of Ottawa, Ottawa, Ontario K1N 6N5, Canada
- Department of Physics, University of Ottawa, Ottawa, Ontario K1N 6N5, Canada
- National Research Council of Canada, 100 Sussex Drive, Ottawa, Ontario K1A 0R6, Canada
| | - Michael S. Schuurman
- Department of Chemistry and Biomolecular Sciences, University of Ottawa, Ottawa, Ontario K1N 6N5, Canada
- National Research Council of Canada, 100 Sussex Drive, Ottawa, Ontario K1A 0R6, Canada
| |
Collapse
|
9
|
Berlin S, Isacoff EY. Synapses in the spotlight with synthetic optogenetics. EMBO Rep 2017; 18:677-692. [PMID: 28396573 DOI: 10.15252/embr.201744010] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2017] [Revised: 03/02/2017] [Accepted: 03/09/2017] [Indexed: 12/15/2022] Open
Abstract
Membrane receptors and ion channels respond to various stimuli and relay that information across the plasma membrane by triggering specific and timed processes. These include activation of second messengers, allowing ion permeation, and changing cellular excitability, to name a few. Gaining control over equivalent processes is essential to understand neuronal physiology and pathophysiology. Recently, new optical techniques have emerged proffering new remote means to control various functions of defined neuronal populations by light, dubbed optogenetics. Still, optogenetic tools do not typically address the activity of receptors and channels native to neurons (or of neuronal origin), nor gain access to their signaling mechanisms. A related method-synthetic optogenetics-bridges this gap by endowing light sensitivity to endogenous neuronal receptors and channels by the appending of synthetic, light-receptive molecules, or photoswitches. This provides the means to photoregulate neuronal receptors and channels and tap into their native signaling mechanisms in select regions of the neurons, such as the synapse. This review discusses the development of synthetic optogenetics as a means to study neuronal receptors and channels remotely, in their natural environment, with unprecedented spatial and temporal precision, and provides an overview of tool design, mode of action, potential clinical applications and insights and achievements gained.
Collapse
Affiliation(s)
- Shai Berlin
- The Ruth and Bruce Rappaport Faculty of Medicine, Technion- Israel Institute of Technology, Haifa, Israel
| | - Ehud Y Isacoff
- Helen Wills Neuroscience Institute, University of California, Berkeley, CA, USA.,Department of Molecular and Cell Biology, University of California, Berkeley, CA, USA.,Physical Bioscience Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| |
Collapse
|
10
|
Direct observation of the three regions in α-synuclein that determine its membrane-bound behaviour. Nat Commun 2014; 5:3827. [PMID: 24871041 PMCID: PMC4046108 DOI: 10.1038/ncomms4827] [Citation(s) in RCA: 319] [Impact Index Per Article: 31.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2014] [Accepted: 04/07/2014] [Indexed: 12/22/2022] Open
Abstract
α-synuclein (αS) is a protein involved in neurotransmitter release in presynaptic terminals, and whose aberrant aggregation is associated with Parkinson's disease. In dopaminergic neurons, αS exists in a tightly regulated equilibrium between water-soluble and membrane-associated forms. Here we use a combination of solid-state and solution NMR spectroscopy to characterize the conformations of αS bound to lipid membranes mimicking the composition and physical properties of synaptic vesicles. The study shows three αS regions possessing distinct structural and dynamical properties, including an N-terminal helical segment having a role of membrane anchor, an unstructured C-terminal region that is weakly associated with the membrane and a central region acting as a sensor of the lipid properties and determining the affinity of αS membrane binding. Taken together, our data define the nature of the interactions of αS with biological membranes and provide insights into their roles in the function of this protein and in the molecular processes leading to its aggregation.
Collapse
|
11
|
Álvarez R, Vaz B, Gronemeyer H, de Lera ÁR. Functions, therapeutic applications, and synthesis of retinoids and carotenoids. Chem Rev 2013; 114:1-125. [PMID: 24266866 DOI: 10.1021/cr400126u] [Citation(s) in RCA: 163] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- Rosana Álvarez
- Departamento de Química Orgánica, Centro de Investigación Biomédica (CINBIO), and Instituto de Investigación Biomédica de Vigo (IBIV), Universidade de Vigo , 36310 Vigo, Spain
| | | | | | | |
Collapse
|
12
|
Colherinhas G, Fonseca TL, Castro MA, Coutinho K, Canuto S. Isotropic magnetic shielding constants of retinal derivatives in aprotic and protic solvents. J Chem Phys 2013; 139:094502. [PMID: 24028122 DOI: 10.1063/1.4819694] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We investigate the nuclear isotropic shielding constants σ((13)C) and σ((17)O) of isomers of retinoic acid and retinal in gas-phase and in chloroform, acetonitrile, methanol, and water solutions via Monte Carlo simulation and quantum mechanics calculations using the GIAO-B3LYP∕6-311++G(2d,2p) approach. Electronic solute polarization effects due to protic and aprotic solvents are included iteratively and play an important role in the quantitative determination of oxygen shielding constants. Our MP2∕6-31G+(d) results show substantial increases of the dipole moment of both retinal derivatives in solution as compared with the gas-phase results (between 22% and 26% in chloroform and between 55% and 99% in water). For the oxygen atoms the influence of the solute polarization is mild for σ((17)O) of hydroxyl group, even in protic solvents, but it is particularly important for σ((17)O) of carbonyl group. For the latter, there is a sizable increase in the magnitude with increasing solvent polarity. For the carbon atoms, the solvent effects on the σ((13)C) values are in general small, being more appreciable in carbon atoms of the polyene chain than in the carbon atoms of the β-ionone ring and methyl groups. The results also show that isomeric changes on the backbones of the polyene chains have marked influence on the (13)C chemical shifts of carbon atoms near to the structural distortions, in good agreement with the experimental results measured in solution.
Collapse
Affiliation(s)
- G Colherinhas
- Instituto de Física, Universidade Federal de Goiás, CP 131, 74001-970 Goia^nia, GO, Brazil
| | | | | | | | | |
Collapse
|
13
|
G-protein-coupled receptor structure, ligand binding and activation as studied by solid-state NMR spectroscopy. Biochem J 2013; 450:443-57. [DOI: 10.1042/bj20121644] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
GPCRs (G-protein-coupled receptors) are versatile signalling molecules at the cell surface and make up the largest and most diverse family of membrane receptors in the human genome. They convert a large variety of extracellular stimuli into intracellular responses through the activation of heterotrimeric G-proteins, which make them key regulatory elements in a broad range of normal and pathological processes, and are therefore one of the most important targets for pharmaceutical drug discovery. Knowledge of a GPCR structure enables us to gain a mechanistic insight into its function and dynamics, and further aid rational drug design. Despite intensive research carried out over the last three decades, resolving the structural basis of GPCR function is still a major activity. The crystal structures obtained in the last 5 years provide the first opportunity to understand how protein structure dictates the unique functional properties of these complex signalling molecules. However, owing to the intrinsic hydrophobicity, flexibility and instability of membrane proteins, it is still a challenge to crystallize GPCRs, and, when this is possible, it is no longer in its native membrane environment and no longer without modification. Furthermore, the conformational change of the transmembrane α-helices associated with the structure activation increases the difficulty of capturing the activation state of a GPCR to a higher resolution by X-ray crystallography. On the other hand, solid-state NMR may offer a unique opportunity to study membrane protein structure, ligand binding and activation at atomic resolution in the native membrane environment, as well as described functionally significant dynamics. In the present review, we discuss some recent achievements of solid-state NMR for understanding GPCRs, the largest mammalian proteome at ~1% of the total expressed proteins. Structural information, details of determination, details of ligand conformations and the consequences of ligand binding to initiate activation can all be explored with solid-state NMR.
Collapse
|
14
|
PatchinG SG, Henderson PJF, Sharples DJ, Middleton DA. Probing the contacts of a low-affinity substrate with a membrane-embedded transport protein using1H-13C cross-polarisation magic-angle spinning solid-state NMR. Mol Membr Biol 2012; 30:129-37. [DOI: 10.3109/09687688.2012.743193] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
|
15
|
Mertz B, Struts AV, Feller SE, Brown MF. Molecular simulations and solid-state NMR investigate dynamical structure in rhodopsin activation. BIOCHIMICA ET BIOPHYSICA ACTA 2012; 1818:241-51. [PMID: 21851809 PMCID: PMC5270601 DOI: 10.1016/j.bbamem.2011.08.003] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/26/2011] [Revised: 08/01/2011] [Accepted: 08/01/2011] [Indexed: 10/17/2022]
Abstract
Rhodopsin has served as the primary model for studying G protein-coupled receptors (GPCRs)-the largest group in the human genome, and consequently a primary target for pharmaceutical development. Understanding the functions and activation mechanisms of GPCRs has proven to be extraordinarily difficult, as they are part of a complex signaling cascade and reside within the cell membrane. Although X-ray crystallography has recently solved several GPCR structures that may resemble the activated conformation, the dynamics and mechanism of rhodopsin activation continue to remain elusive. Notably solid-state ((2))H NMR spectroscopy provides key information pertinent to how local dynamics of the retinal ligand change during rhodopsin activation. When combined with molecular mechanics simulations of proteolipid membranes, a new paradigm for the rhodopsin activation process emerges. Experiment and simulation both suggest that retinal isomerization initiates the rhodopsin photocascade to yield not a single activated structure, but rather an ensemble of activated conformational states. This article is part of a Special Issue entitled: Membrane protein structure and function.
Collapse
Affiliation(s)
- Blake Mertz
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721, USA
| | - Andrey V. Struts
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721, USA
- Department of Medical Physics, St. Petersburg State Medical University, St. Petersburg 194100, Russia
| | - Scott E. Feller
- Department of Chemistry, Wabash College, Crawfordsville, IN 47933, USA
| | - Michael F. Brown
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721, USA
- Department of Physics, University of Arizona, Tucson, AZ 85721, USA
| |
Collapse
|
16
|
Pandey R, Gupta RK, Li PZ, Xu Q, Misra A, Pandey DS. Photoassisted “Gate-Lock” Fluorescence “Turn-on” in a New Schiff Base and Coordination Ability of E–Z Isomers. Org Lett 2012; 14:592-5. [DOI: 10.1021/ol2032043] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Rampal Pandey
- Department of Chemistry, Faculty of Science, Banaras Hindu University, Varanasi -221 005 (U.P.), India
| | - Rakesh Kumar Gupta
- Department of Chemistry, Faculty of Science, Banaras Hindu University, Varanasi -221 005 (U.P.), India
| | - Pei-Zhou Li
- National Institute of Advanced Industrial Science and Technology (AIST), 1-8-31 Midorigaoka, Ikeda, Osaka 563-8577, Japan
| | - Qiang Xu
- National Institute of Advanced Industrial Science and Technology (AIST), 1-8-31 Midorigaoka, Ikeda, Osaka 563-8577, Japan
| | - Arvind Misra
- Department of Chemistry, Faculty of Science, Banaras Hindu University, Varanasi -221 005 (U.P.), India
| | - Daya Shankar Pandey
- Department of Chemistry, Faculty of Science, Banaras Hindu University, Varanasi -221 005 (U.P.), India
| |
Collapse
|
17
|
Solution- and solid-state NMR studies of GPCRs and their ligands. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2011; 1808:1462-75. [DOI: 10.1016/j.bbamem.2010.10.003] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/05/2010] [Revised: 10/02/2010] [Accepted: 10/05/2010] [Indexed: 12/29/2022]
|
18
|
Chen YF, Wang IJ, Lin LLK, Chen MS. Examining rhodopsin retention in endoplasmic reticulum and intracellular localization in vitro and in vivo by using truncated rhodopsin fragments. J Cell Biochem 2011; 112:520-30. [PMID: 21268073 DOI: 10.1002/jcb.22942] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
More than 100 mutations of rhodopsin have been identified to be associated with retinitis pigmentosa (RP), and mostly autosomal-dominant RP (ADRP). The majority of rhodopsin-associated ADRP is caused by protein misfolding and ER retention. In this study, we aimed to evaluate rhodopsin folding, exiting the ER and intracellular localization through expression of the rhodopsin fragments in COS-1 cells as well as in the transgenic zebrafish. We cloned human rhodopsin cDNA, which was then divided into the N-terminal domain, the C-terminal domain, and the fragment between the N- and C-terminal domains, and examine their intracellular expression in vitro and in vivo. We introduced a point mutation, either F45L or G51V, into this fragment and observed the intracellular localization of these mutants in COS-1 cells and in the zebrafish. The results revealed all of the truncated rhodopsin fragments except for the C-terminal domain and the full-length rhodopsin which had some plasma membrane localization, formed aggregates nearby or within the ER in COS-1 cells; however, the N-terminally truncated rhodopsin fragment, the C-terminal domain, and the full-length rhodopsin could traffic to the ROS in the zebrafish. Besides, the F45L mutation and the G51Vmutation in the rhodopsin fragment between the N- and C-terminal domains produced different effects on the aggresome formation and the intracellular distribution of the mutants both in vivo and in vitro. This current study provides new information about the mutant rhodopsin as well as in treatment of the RP in humans in the future.
Collapse
Affiliation(s)
- Yuh-Fang Chen
- Department of Ophthalmology, Taipei County Hospital, Taipei County, Taiwan
| | | | | | | |
Collapse
|
19
|
Rajamani R, Lin YL, Gao J. The opsin shift and mechanism of spectral tuning in rhodopsin. J Comput Chem 2011; 32:854-65. [PMID: 20941732 PMCID: PMC3021771 DOI: 10.1002/jcc.21663] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2010] [Accepted: 08/07/2010] [Indexed: 01/12/2023]
Abstract
Molecular dynamics simulations and combined quantum mechanical and molecular mechanical calculations have been performed to investigate the mechanism of the opsin shift and spectral tuning in rhodopsin. A red shift of -980 cm(-1) was estimated in the transfer of the chromophore from methanol solution environment to the protonated Schiff base (PSB)-binding site of the opsin. The conformational change from a 6-s-cis-all-trans configuration in solution to the 6-s-cis-11-cis conformer contributes additional -200 cm(-1), and the remaining effects were attributed to dispersion interactions with the aromatic residues in the binding site. An opsin shift of 2100 cm(-1) was obtained, in reasonable accord with experiment (2730 cm(-1)). Dynamics simulations revealed that the 6-s-cis bond can occupy two main conformations for the β-ionone ring, resulting in a weighted average dihedral angle of about -50°, which may be compared with the experimental estimate of -28° from solid-state NMR and Raman data. We investigated a series of four single mutations, including E113D, A292S, T118A, and A269T, which are located near the PSB, along the polyene chain of retinal and close to the ionone ring. The computational results on absorption energy shift provided insights into the mechanism of spectral tuning, which involves all means of electronic structural effects, including the stabilization or destabilization of either the ground or the electronically excited state of the retinal PSB.
Collapse
Affiliation(s)
| | - Yen-lin Lin
- Department of Chemistry, Digital Technology Center, and Supercomputing Institute, University of Minnesota, Minneapolis, MN 55455
| | - Jiali Gao
- Department of Chemistry, Digital Technology Center, and Supercomputing Institute, University of Minnesota, Minneapolis, MN 55455
| |
Collapse
|
20
|
Roberts NW, Porter ML, Cronin TW. The molecular basis of mechanisms underlying polarization vision. Philos Trans R Soc Lond B Biol Sci 2011; 366:627-37. [PMID: 21282166 PMCID: PMC3049014 DOI: 10.1098/rstb.2010.0206] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The underlying mechanisms of polarization sensitivity (PS) have long remained elusive. For rhabdomeric photoreceptors, questions remain over the high levels of PS measured experimentally. In ciliary photoreceptors, and specifically cones, little direct evidence supports any type of mechanism. In order to promote a greater interest in these fundamental aspects of polarization vision, we examined a varied collection of studies linking membrane biochemistry, protein-protein interactions, molecular ordering and membrane phase behaviour. While initially these studies may seem unrelated to polarization vision, a common narrative emerges. A surprising amount of evidence exists demonstrating the importance of protein-protein interactions in both rhabdomeric and ciliary photoreceptors, indicating the possible long-range ordering of the opsin protein for increased PS. Moreover, we extend this direction by considering how such protein paracrystalline organization arises in all cell types from controlled membrane phase behaviour and propose a universal pathway for PS to occur in both rhabdomeric and cone photoreceptors.
Collapse
Affiliation(s)
- Nicholas W Roberts
- School of Biological Sciences, University of Bristol, Woodland Road, Bristol BS8 1UG, UK.
| | | | | |
Collapse
|
21
|
Middleton DA. Solid-state NMR detection of 14N-13C dipolar couplings between amino acid side groups provides constraints on amyloid fibril architecture. MAGNETIC RESONANCE IN CHEMISTRY : MRC 2011; 49:65-69. [PMID: 21254226 DOI: 10.1002/mrc.2708] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/16/2010] [Revised: 10/19/2010] [Accepted: 11/05/2010] [Indexed: 05/30/2023]
Abstract
Solid-state nuclear magnetic resonance (SSNMR) is a powerful technique for the structural analysis of amyloid fibrils. With suitable isotope labelling patterns, SSNMR can provide constraints on the secondary structure, alignment and registration of β-strands within amyloid fibrils and identify the tertiary and quaternary contacts defining the packing of the β-sheet layers. Detection of (14)N-(13)C dipolar couplings may provide potentially useful additional structural constraints on β-sheet packing within amyloid fibrils but has not until now been exploited for this purpose. Here a frequency-selective, transfer of population in double resonance SSNMR experiment is used to detect a weak (14)N-(13)C dipolar coupling in amyloid-like fibrils of the peptide H(2)N-SNNFGAILSS-COOH, which was uniformly (13)C and (15)N labelled across the four C-terminal amino acids. The (14)N-(13)C interatomic distance between leucine and asparagine side groups is constrained between 2.4 and 3.8 Å, which allows current structural models of the β-spine arrangement within the fibrils to be refined. This procedure could be useful for the general structural analysis of other proteins in condensed phases and environments, such as biological membranes.
Collapse
Affiliation(s)
- David A Middleton
- School of Biological Sciences, University of Liverpool, Crown Street, Liverpool L69 7ZB, UK.
| |
Collapse
|
22
|
Goncalves JA, Ahuja S, Erfani S, Eilers M, Smith SO. Structure and function of G protein-coupled receptors using NMR spectroscopy. PROGRESS IN NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY 2010; 57:159-80. [PMID: 20633362 PMCID: PMC2907352 DOI: 10.1016/j.pnmrs.2010.04.004] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/11/2010] [Accepted: 04/08/2010] [Indexed: 05/15/2023]
Affiliation(s)
- Joseph A Goncalves
- Department of Biochemistry and Cell Biology, Center for Structural Biology, Stony Brook University, Stony Brook, NY 11794-5215, USA
| | | | | | | | | |
Collapse
|
23
|
Tikhonova IG, Costanzi S. Unraveling the structure and function of G protein-coupled receptors through NMR spectroscopy. Curr Pharm Des 2010; 15:4003-16. [PMID: 20028318 DOI: 10.2174/138161209789824803] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
G protein-coupled receptors (GPCRs) are a large superfamily of signaling proteins expressed on the plasma membrane. They are involved in a wide range of physiological processes and, therefore, are exploited as drug targets in a multitude of therapeutic areas. In this extent, knowledge of structural and functional properties of GPCRs may greatly facilitate rational design of modulator compounds. Solution and solid-state nuclear magnetic resonance (NMR) spectroscopy represents a powerful method to gather atomistic insights into protein structure and dynamics. In spite of the difficulties inherent the solution of the structure of membrane proteins through NMR, these methods have been successfully applied, sometimes in combination with molecular modeling, to the determination of the structure of GPCR fragments, the mapping of receptor-ligand interactions, and the study of the conformational changes associated with the activation of the receptors. In this review, we provide a summary of the NMR contributions to the study of the structure and function of GPCRs, also in light of the published crystal structures.
Collapse
Affiliation(s)
- Irina G Tikhonova
- Laboratory of Biological Modeling, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, DHHS, Bethesda, MD 20892, USA
| | | |
Collapse
|
24
|
Ahuja S, Eilers M, Hirshfeld A, Yan ECY, Ziliox M, Sakmar TP, Sheves M, Smith SO. 6-s-cis Conformation and polar binding pocket of the retinal chromophore in the photoactivated state of rhodopsin. J Am Chem Soc 2010; 131:15160-9. [PMID: 19795853 DOI: 10.1021/ja9034768] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The visual pigment rhodopsin is unique among the G protein-coupled receptors in having an 11-cis retinal chromophore covalently bound to the protein through a protonated Schiff base linkage. The chromophore locks the visual receptor in an inactive conformation through specific steric and electrostatic interactions. This efficient inverse agonist is rapidly converted to an agonist, the unprotonated Schiff base of all-trans retinal, upon light activation. Here, we use magic angle spinning NMR spectroscopy to obtain the (13)C chemical shifts (C5-C20) of the all-trans retinylidene chromophore and the (15)N chemical shift of the Schiff base nitrogen in the active metarhodopsin II intermediate. The retinal chemical shifts are sensitive to the conformation of the chromophore and its molecular interactions within the protein-binding site. Comparison of the retinal chemical shifts in metarhodopsin II with those of retinal model compounds reveals that the Schiff base environment is polar. In particular, the (13)C15 and (15)Nepsilon chemical shifts indicate that the C horizontal lineN bond is highly polarized in a manner that would facilitate Schiff base hydrolysis. We show that a strong perturbation of the retinal (13)C12 chemical shift observed in rhodopsin is reduced in wild-type metarhodopsin II and in the E181Q mutant of rhodopsin. On the basis of the T(1) relaxation time of the retinal (13)C18 methyl group and the conjugated retinal (13)C5 and (13)C8 chemical shifts, we have determined that the conformation of the retinal C6-C7 single bond connecting the beta-ionone ring and the retinylidene chain is 6-s-cis in both the inactive and the active states of rhodopsin. These results are discussed within the general framework of ligand-activated G protein-coupled receptors.
Collapse
Affiliation(s)
- Shivani Ahuja
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, New York 11794-5215, USA
| | | | | | | | | | | | | | | |
Collapse
|
25
|
Edwards R, Madine J, Fielding L, Middleton DA. Measurement of multiple torsional angles from one-dimensional solid-state NMR spectra: application to the conformational analysis of a ligand in its biological receptor site. Phys Chem Chem Phys 2010; 12:13999-4008. [DOI: 10.1039/c0cp00326c] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
26
|
Watanabe HC, Mori Y, Tada T, Yokoyama S, Yamato T. Molecular mechanism of long-range synergetic color tuning between multiple amino acid residues in conger rhodopsin. Biophysics (Nagoya-shi) 2010; 6:67-68. [PMID: 21297892 PMCID: PMC3032607 DOI: 10.2142/biophysics.6.67] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
Abstract
The synergetic effects of multiple rhodopsin mutations on color tuning need to be completely elucidated. Systematic genetic studies and spectroscopy have demonstrated an interesting example of synergetic color tuning between two amino acid residues in conger rhodopsin's ancestral pigment (p501): -a double mutation at one nearby and one distant residue led to a significant λ(max) blue shift of 13 nm, whereas neither of the single mutations at these two sites led to meaningful shifts.To analyze the molecular mechanisms of this synergetic color tuning, we performed homology modeling, molecular simulations, and electronic state calculations. For the double mutant, N195A/A292S, in silico mutation analysis demonstrated conspicuous structural changes in the retinal chromophore, whereas that of the single mutant, A292S, was almost unchanged. Using statistical ensembles of QM/MM optimized structures, the excitation energy of retinal chromophore was evaluated for the three visual pigments. As a result, the λ(max) shift of double mutant (DM) from p501 was -8 nm, while that of single mutant (SM) from p501 was +1 nm. Molecular dynamics simulation for DM demonstrated frequent isomerization between 6-s-cis and 6-s-trans conformers. Unexpectedly, however, the two conformers exhibited almost identical excitation energy, whereas principal component analysis (PCA) identified the retinal-counterion cooperative change of BLA (bond length alternation) and retinal-counterion interaction lead to the shift.
Collapse
Affiliation(s)
- Hiroshi C Watanabe
- Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8602, Japan
| | | | | | | | | |
Collapse
|
27
|
Middleton DA, Hughes E, Fedosova NU, Esmann M. Solid-state NMR studies of adenosine 5'-triphosphate freeze-trapped in the nucleotide site of Na,K-ATPase. Chembiochem 2009; 10:1789-92. [PMID: 19565594 DOI: 10.1002/cbic.200900167] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- David A Middleton
- School of Biological Sciences, University of Liverpool, Crown Street, Liverpool L69 7ZB, UK.
| | | | | | | |
Collapse
|
28
|
Brown MF, Salgado GFJ, Struts AV. Retinal dynamics during light activation of rhodopsin revealed by solid-state NMR spectroscopy. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2009; 1798:177-93. [PMID: 19716801 DOI: 10.1016/j.bbamem.2009.08.013] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/05/2009] [Revised: 07/25/2009] [Accepted: 08/12/2009] [Indexed: 11/28/2022]
Abstract
Rhodopsin is a canonical member of class A of the G protein-coupled receptors (GPCRs) that are implicated in many of the drug interventions in humans and are of great pharmaceutical interest. The molecular mechanism of rhodopsin activation remains unknown as atomistic structural information for the active metarhodopsin II state is currently lacking. Solid-state (2)H NMR constitutes a powerful approach to study atomic-level dynamics of membrane proteins. In the present application, we describe how information is obtained about interactions of the retinal cofactor with rhodopsin that change with light activation of the photoreceptor. The retinal methyl groups play an important role in rhodopsin function by directing conformational changes upon transition into the active state. Site-specific (2)H labels have been introduced into the methyl groups of retinal and solid-state (2)H NMR methods applied to obtain order parameters and correlation times that quantify the mobility of the cofactor in the inactive dark state, as well as the cryotrapped metarhodopsin I and metarhodopsin II states. Analysis of the angular-dependent (2)H NMR line shapes for selectively deuterated methyl groups of rhodopsin in aligned membranes enables determination of the average ligand conformation within the binding pocket. The relaxation data suggest that the beta-ionone ring is not expelled from its hydrophobic pocket in the transition from the pre-activated metarhodopsin I to the active metarhodopsin II state. Rather, the major structural changes of the retinal cofactor occur already at the metarhodopsin I state in the activation process. The metarhodopsin I to metarhodopsin II transition involves mainly conformational changes of the protein within the membrane lipid bilayer rather than the ligand. The dynamics of the retinylidene methyl groups upon isomerization are explained by an activation mechanism involving cooperative rearrangements of extracellular loop E2 together with transmembrane helices H5 and H6. These activating movements are triggered by steric clashes of the isomerized all-trans retinal with the beta4 strand of the E2 loop and the side chains of Glu(122) and Trp(265) within the binding pocket. The solid-state (2)H NMR data are discussed with regard to the pathway of the energy flow in the receptor activation mechanism.
Collapse
Affiliation(s)
- Michael F Brown
- Department of Chemistry, University of Arizona, Tucson, AZ 85721, USA; Department of Physics, University of Arizona, Tucson, AZ 85721, USA.
| | | | | |
Collapse
|
29
|
Feldman TB, Kholmurodov KT, Ostrovsky MA, Khrenova MG, Nemukhin AV. Studies on the conformational state of the chromophore group (11-cis-retinal) in rhodopsin by computer molecular simulation methods. Biophysics (Nagoya-shi) 2009. [DOI: 10.1134/s0006350909040113] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
|
30
|
Brown MF, Martínez-Mayorga K, Nakanishi K, Salgado GFJ, Struts AV. Retinal conformation and dynamics in activation of rhodopsin illuminated by solid-state H NMR spectroscopy. Photochem Photobiol 2009; 85:442-53. [PMID: 19267870 DOI: 10.1111/j.1751-1097.2008.00510.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Solid-state NMR spectroscopy gives a powerful avenue for investigating G protein-coupled receptors and other integral membrane proteins in a native-like environment. This article reviews the use of solid-state (2)H NMR to study the retinal cofactor of rhodopsin in the dark state as well as the meta I and meta II photointermediates. Site-specific (2)H NMR labels have been introduced into three regions (methyl groups) of retinal that are crucially important for the photochemical function of rhodopsin. Despite its phenomenal stability (2)H NMR spectroscopy indicates retinal undergoes rapid fluctuations within the protein binding cavity. The spectral lineshapes reveal the methyl groups spin rapidly about their three-fold (C(3)) axes with an order parameter for the off-axial motion of SC(3) approximately 0.9. For the dark state, the (2)H NMR structure of 11-cis-retinal manifests torsional twisting of both the polyene chain and the beta-ionone ring due to steric interactions of the ligand and the protein. Retinal is accommodated within the rhodopsin binding pocket with a negative pretwist about the C11=C12 double bond. Conformational distortion explains its rapid photochemistry and reveals the trajectory of the 11-cis to trans isomerization. In addition, (2)H NMR has been applied to study the retinylidene dynamics in the dark and light-activated states. Upon isomerization there are drastic changes in the mobility of all three methyl groups. The relaxation data support an activation mechanism whereby the beta-ionone ring of retinal stays in nearly the same environment, without a large displacement of the ligand. Interactions of the beta-ionone ring and the retinylidene Schiff base with the protein transmit the force of the retinal isomerization. Solid-state (2)H NMR thus provides information about the flow of energy that triggers changes in hydrogen-bonding networks and helix movements in the activation mechanism of the photoreceptor.
Collapse
Affiliation(s)
- Michael F Brown
- Department of Chemistry, University of Arizona, Tucson, AZ, USA.
| | | | | | | | | |
Collapse
|
31
|
Altun A, Yokoyama S, Morokuma K. Spectral tuning in visual pigments: an ONIOM(QM:MM) study on bovine rhodopsin and its mutants. J Phys Chem B 2008; 112:6814-27. [PMID: 18473437 DOI: 10.1021/jp709730b] [Citation(s) in RCA: 92] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We have investigated geometries and excitation energies of bovine rhodopsin and some of its mutants by hybrid quantum mechanical/molecular mechanical (QM/MM) calculations in ONIOM scheme, employing B3LYP and BLYP density functionals as well as DFTB method for the QM part and AMBER force field for the MM part. QM/MM geometries of the protonated Schiff-base 11- cis-retinal with B3LYP and DFTB are very similar to each other. TD-B3LYP/MM excitation energy calculations reproduce the experimental absorption maximum of 500 nm in the presence of native rhodopsin environment and predict spectral shifts due to mutations within 10 nm, whereas TD-BLYP/MM excitation energies have red-shift error of at least 50 nm. In the wild-type rhodopsin, Glu113 shifts the first excitation energy to blue and accounts for most of the shift found. Other amino acids individually contribute to the first excitation energy but their net effect is small. The electronic polarization effect is essential for reproducing experimental bond length alternation along the polyene chain in protonated Schiff-base retinal, which correlates with the computed first excitation energy. It also corrects the excitation energies and spectral shifts in mutants, more effectively for deprotonated Schiff-base retinal than for the protonated form. The protonation state and conformation of mutated residues affect electronic spectrum significantly. The present QM/MM calculations estimate not only the experimental excitation energies but also the source of spectral shifts in mutants.
Collapse
Affiliation(s)
- Ahmet Altun
- Cherry L. Emerson Center for Scientific Computation and Department of Chemistry, Emory University, Atlanta, Georgia 30322, USA
| | | | | |
Collapse
|
32
|
Altun A, Yokoyama S, Morokuma K. Quantum mechanical/molecular mechanical studies on spectral tuning mechanisms of visual pigments and other photoactive proteins. Photochem Photobiol 2008; 84:845-54. [PMID: 18331400 DOI: 10.1111/j.1751-1097.2008.00308.x] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The protein environments surrounding the retinal tune electronic absorption maximum from 350 to 630 nm. Hybrid quantum mechanical/molecular mechanical (QM/MM) methods can be used in calculating excitation energies of retinal in its native protein environments and in studying the molecular basis of spectral tuning. We hereby review recent QM/MM results on the phototransduction of bovine rhodopsin, bacteriorhodopsin, sensory rhodopsin II, nonretinal photoactive yellow protein and their mutants.
Collapse
Affiliation(s)
- Ahmet Altun
- Cherry L. Emerson Center for Scientific Computation and Department of Chemistry, Emory University, Atlanta, GA, USA
| | | | | |
Collapse
|
33
|
Brown MF, Heyn MP, Job C, Kim S, Moltke S, Nakanishi K, Nevzorov AA, Struts AV, Salgado GFJ, Wallat I. Solid-state 2H NMR spectroscopy of retinal proteins in aligned membranes. BIOCHIMICA ET BIOPHYSICA ACTA 2007; 1768:2979-3000. [PMID: 18021739 PMCID: PMC5233718 DOI: 10.1016/j.bbamem.2007.10.014] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/08/2007] [Revised: 10/10/2007] [Accepted: 10/10/2007] [Indexed: 11/21/2022]
Abstract
Solid-state 2H NMR spectroscopy gives a powerful avenue to investigating the structures of ligands and cofactors bound to integral membrane proteins. For bacteriorhodopsin (bR) and rhodopsin, retinal was site-specifically labeled by deuteration of the methyl groups followed by regeneration of the apoprotein. 2H NMR studies of aligned membrane samples were conducted under conditions where rotational and translational diffusion of the protein were absent on the NMR time scale. The theoretical lineshape treatment involved a static axial distribution of rotating C-C2H3 groups about the local membrane frame, together with the static axial distribution of the local normal relative to the average normal. Simulation of solid-state 2H NMR lineshapes gave both the methyl group orientations and the alignment disorder (mosaic spread) of the membrane stack. The methyl bond orientations provided the angular restraints for structural analysis. In the case of bR the retinal chromophore is nearly planar in the dark- and all-trans light-adapted states, as well upon isomerization to 13-cis in the M state. The C13-methyl group at the "business end" of the chromophore changes its orientation to the membrane upon photon absorption, moving towards W182 and thus driving the proton pump in energy conservation. Moreover, rhodopsin was studied as a prototype for G protein-coupled receptors (GPCRs) implicated in many biological responses in humans. In contrast to bR, the retinal chromophore of rhodopsin has an 11-cis conformation and is highly twisted in the dark state. Three sites of interaction affect the torsional deformation of retinal, viz. the protonated Schiff base with its carboxylate counterion; the C9-methyl group of the polyene; and the beta-ionone ring within its hydrophobic pocket. For rhodopsin, the strain energy and dynamics of retinal as established by 2H NMR are implicated in substituent control of activation. Retinal is locked in a conformation that is twisted in the direction of the photoisomerization, which explains the dark stability of rhodopsin and allows for ultra-fast isomerization upon absorption of a photon. Torsional strain is relaxed in the meta I state that precedes subsequent receptor activation. Comparison of the two retinal proteins using solid-state 2H NMR is thus illuminating in terms of their different biological functions.
Collapse
Affiliation(s)
- Michael F Brown
- Department of Chemistry, University of Arizona, Tucson, Arizona 85721, USA.
| | | | | | | | | | | | | | | | | | | |
Collapse
|
34
|
Tanaka K, Struts AV, Krane S, Fujioka N, Salgado GFJ, Martínez-Mayorga K, Brown MF, Nakanishi K. Synthesis of CD3-Labeled 11-cis-Retinals and Application to Solid-State Deuterium NMR Spectroscopy of Rhodopsin. BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 2007. [DOI: 10.1246/bcsj.80.2177] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
|
35
|
Wylie BJ, Sperling LJ, Rienstra CM. Isotropic chemical shifts in magic-angle spinning NMR spectra of proteins. Phys Chem Chem Phys 2007; 10:405-13. [PMID: 18174982 DOI: 10.1039/b710736f] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Here we examine the effect of magic-angle spinning (MAS) rate upon lineshape and observed peak position for backbone carbonyl (C') peaks in NMR spectra of uniformly-(13)C,15N-labeled (U-(13)C,15N) solid proteins. 2D N-C' spectra of U-(13)C,15N microcrystalline protein GB1 were acquired at six MAS rates, and the site-resolved C' lineshapes were analyzed by numerical simulations and comparison to spectra from a sparsely labeled sample (derived from 1,3-(13)C-glycerol). Spectra of the U-(13)C,15N sample demonstrate large variations in the signal-to-noise ratio and peak positions, which are absent in spectra of the sparsely labeled sample, in which most 13C' sites do not possess a directly bonded 13CA. These effects therefore are a consequence of rotational resonance, which is a well-known phenomenon. Yet the magnitude of this effect pertaining to chemical shift assignment has not previously been examined. To quantify these effects in high-resolution protein spectra, we performed exact numerical two- and four-spin simulations of the C' lineshapes, which reproduced the experimentally observed features. Observed peak positions differ from the isotropic shift by up to 1.0 ppm, even for MAS rates relatively far (a few ppm) from rotational resonance. Although under these circumstances the correct isotropic chemical shift values may be determined through simulation, systematic errors are minimized when the MAS rate is equivalent to approximately 85 ppm for 13C. This moderate MAS condition simplifies spectral assignment and enables data sets from different labeling patterns and spinning rates to be used most efficiently for structure determination.
Collapse
Affiliation(s)
- Benjamin J Wylie
- Department of Chemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, IL 61801, USA
| | | | | |
Collapse
|
36
|
Reuther G, Tan KT, Vogel A, Nowak C, Arnold K, Kuhlmann J, Waldmann H, Huster D. The lipidated membrane anchor of full length N-Ras protein shows an extensive dynamics as revealed by solid-state NMR spectroscopy. J Am Chem Soc 2007; 128:13840-6. [PMID: 17044712 DOI: 10.1021/ja063635s] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Many proteins involved in signal transduction are equipped with covalently attached lipid chains providing a hydrophobic anchor targeting these molecules to membranes. Despite the considerable biological significance of this membrane binding mechanism for 5-10% of all cellular proteins, to date very little is known about structural and dynamical features of lipidated membrane binding domains. Here we report the first comprehensive study of the molecular dynamics of the C-terminus of membrane-associated full-length lipidated Ras protein determined by solid-state NMR. Fully functional lipid-modified N-Ras protein was obtained by chemical-biological synthesis ligating the expressed water soluble N-terminus with a chemically synthesized (2)H or (13)C labeled lipidated heptapeptide. Dynamical parameters for the lipid chain modification at Cys 181 were determined from static (2)H NMR order parameter and relaxation measurements. Order parameters describing the amplitude of motion in the protein backbone and the side chain were determined from site-specific measurements of (1)H-(13)C dipolar couplings for all seven amino acids in the membrane anchor of Ras. Finally, the correlation times of motion were determined from temperature dependent relaxation time measurements and analyzed using a modified Lipari Szabo approach. Overall, the C-terminus of Ras shows a versatile dynamics with segmental fluctuations and axially symmetric overall motions on the membrane surface. In particular, the lipid chain modifications are highly flexible in the membrane.
Collapse
Affiliation(s)
- Guido Reuther
- Institute of Biotechnology, Junior Research Group Structural Biology of Membrane Proteins, Martin Luther University Halle-Wittenberg, Kurt-Mothes-Str. 3, D-06120 Halle, Germany
| | | | | | | | | | | | | | | |
Collapse
|
37
|
Vosegaard T, Kamihira-Ishijima M, Watts A, Nielsen NC. Helix conformations in 7TM membrane proteins determined using oriented-sample solid-state NMR with multiple residue-specific 15N labeling. Biophys J 2007; 94:241-50. [PMID: 17827220 PMCID: PMC2134869 DOI: 10.1529/biophysj.107.116004] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Oriented solid-state NMR in combination with multiple-residue-specific (15)N labeling and extensive numerical spectral analysis is proposed to determine helix conformations of large membrane proteins in native membranes. The method is demonstrated on uniaxially oriented samples of (15)N-methionine, -valine, and -glycine-labeled bacteriorhopsin in native purple membranes. Experimental two-dimensional (1)H-(15)N dipole-dipole coupling versus (15)N chemical shift spectra for all samples are analyzed numerically to establish combined constraints on the orientation of the seven transmembrane helices relative to the membrane bilayer normal. Since the method does not depend on specific resonance assignments and proves robust toward nonidealities in the sample alignment, it may be generally feasible for the study of conformational arrangement and function-induced conformation changes of large integral membrane proteins.
Collapse
Affiliation(s)
- Thomas Vosegaard
- Center for Insoluble Protein Structures (inSPIN), Interdisciplinary Nanoscience Center (iNANO) and Department of Chemistry, University of Aarhus, Aarhus, Denmark.
| | | | | | | |
Collapse
|
38
|
Lau PW, Grossfield A, Feller SE, Pitman MC, Brown MF. Dynamic structure of retinylidene ligand of rhodopsin probed by molecular simulations. J Mol Biol 2007; 372:906-917. [PMID: 17719606 PMCID: PMC5233727 DOI: 10.1016/j.jmb.2007.06.047] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2007] [Revised: 06/13/2007] [Accepted: 06/18/2007] [Indexed: 11/22/2022]
Abstract
Rhodopsin is currently the only available atomic-resolution template for understanding biological functions of the G protein-coupled receptor (GPCR) family. The structural basis for the phenomenal dark state stability of 11-cis-retinal bound to rhodopsin and its ultrafast photoreaction are active topics of research. In particular, the beta-ionone ring of the retinylidene inverse agonist is crucial for the activation mechanism. We analyzed a total of 23 independent, 100 ns all-atom molecular dynamics simulations of rhodopsin embedded in a lipid bilayer in the microcanonical (N,V,E) ensemble. Analysis of intramolecular fluctuations predicts hydrogen-out-of-plane (HOOP) wagging modes of retinal consistent with those found in Raman vibrational spectroscopy. We show that sampling and ergodicity of the ensemble of simulations are crucial for determining the distribution of conformers of retinal bound to rhodopsin. The polyene chain is rigidly locked into a single, twisted conformation, consistent with the function of retinal as an inverse agonist in the dark state. Most surprisingly, the beta-ionone ring is mobile within its binding pocket; interactions are non-specific and the cavity is sufficiently large to enable structural heterogeneity. We find that retinal occupies two distinct conformations in the dark state, contrary to most previous assumptions. The beta-ionone ring can rotate relative to the polyene chain, thereby populating both positively and negatively twisted 6-s-cis enantiomers. This result, while unexpected, strongly agrees with experimental solid-state (2)H NMR spectra. Correlation analysis identifies the residues most critical to controlling mobility of retinal; we find that Trp265 moves away from the ionone ring prior to any conformational transition. Our findings reinforce how molecular dynamics simulations can challenge conventional assumptions for interpreting experimental data, especially where existing models neglect conformational fluctuations.
Collapse
Affiliation(s)
- Pick-Wei Lau
- Department of Biochemistry & Molecular Biophysics, University of Arizona, Tucson, Arizona 85721, USA
| | - Alan Grossfield
- IBM TJ Watson Research Center, Yorktown Heights, New York 10598, USA
| | - Scott E. Feller
- Department of Chemistry, Wabash College, Crawfordsville, Indiana 47933, USA
| | - Michael C. Pitman
- IBM TJ Watson Research Center, Yorktown Heights, New York 10598, USA
| | - Michael F. Brown
- Department of Biochemistry & Molecular Biophysics, University of Arizona, Tucson, Arizona 85721, USA
- Department of Chemistry, University of Arizona, Tucson, Arizona 85721, USA
- Department of Physics, University of Arizona, Tucson, Arizona 85721, USA
- Corresponding author. Present address: Pick-Wei Lau, Department of Molecular Biology, The Scripps Research Institute, La Jolla, California 92037, USA.
| |
Collapse
|
39
|
Fu W, Shen J, Luo X, Zhu W, Cheng J, Yu K, Briggs JM, Jin G, Chen K, Jiang H. Dopamine D1 receptor agonist and D2 receptor antagonist effects of the natural product (-)-stepholidine: molecular modeling and dynamics simulations. Biophys J 2007; 93:1431-41. [PMID: 17468175 PMCID: PMC1948031 DOI: 10.1529/biophysj.106.088500] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
(-)-Stepholidine (SPD), an active ingredient of the Chinese herb Stephania, is the first compound found to have dual function as a dopamine receptor D1 agonist and D2 antagonist. Insights into dynamical behaviors of D1 and D2 receptors and their interaction modes with SPD are crucial in understanding the structural and functional characteristics of dopamine receptors. In this study a computational approach, integrating protein structure prediction, automated molecular docking, and molecular dynamics simulations were employed to investigate the dual action mechanism of SPD on the D1 and D2 receptors, with the eventual aim to develop new drugs for treating diseases affecting the central nervous system such as schizophrenia. The dynamics simulations revealed the surface features of the electrostatic potentials and the conformational "open-closed" process of the binding entrances of two dopamine receptors. Potential binding conformations of D1 and D2 receptors were obtained, and the D1-SPD and D2-SPD complexes were generated, which are in good agreement with most of experimental data. The D1-SPD structure shows that the K-167_EL-2-E-302_EL-3 (EL-2: extracellular loop 2; EL-3: extracellular loop 3) salt bridge plays an important role for both the conformational change of the extracellular domain and the binding of SPD. Based on our modeling and simulations, we proposed a mechanism of the dual action of SPD and a subsequent signal transduction model. Further mutagenesis and biophysical experiments are needed to test and improve our proposed dual action mechanism of SPD and signal transduction model.
Collapse
Affiliation(s)
- Wei Fu
- Drug Discovery and Design Centre, State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, PR China
| | | | | | | | | | | | | | | | | | | |
Collapse
|
40
|
Struts AV, Salgado GFJ, Tanaka K, Krane S, Nakanishi K, Brown MF. Structural analysis and dynamics of retinal chromophore in dark and meta I states of rhodopsin from 2H NMR of aligned membranes. J Mol Biol 2007; 372:50-66. [PMID: 17640664 PMCID: PMC5233725 DOI: 10.1016/j.jmb.2007.03.046] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2006] [Revised: 03/02/2007] [Accepted: 03/19/2007] [Indexed: 11/29/2022]
Abstract
Rhodopsin is a prototype for G protein-coupled receptors (GPCRs) that are implicated in many biological responses in humans. A site-directed (2)H NMR approach was used for structural analysis of retinal within its binding cavity in the dark and pre-activated meta I states. Retinal was labeled with (2)H at the C5, C9, or C13 methyl groups by total synthesis, and was used to regenerate the opsin apoprotein. Solid-state (2)H NMR spectra were acquired for aligned membranes in the low-temperature lipid gel phase versus the tilt angle to the magnetic field. Data reduction assumed a static uniaxial distribution, and gave the retinylidene methyl bond orientations plus the alignment disorder (mosaic spread). The dark-state (2)H NMR structure of 11-cis-retinal shows torsional twisting of the polyene chain and the beta-ionone ring. The ligand undergoes restricted motion, as evinced by order parameters of approximately 0.9 for the spinning C-C(2)H(3) groups, with off-axial fluctuations of approximately 15 degrees . Retinal is accommodated within the rhodopsin binding pocket with a negative pre-twist about the C11=C12 double bond that explains its rapid photochemistry and the trajectory of 11-cis to trans isomerization. In the cryo-trapped meta I state, the (2)H NMR structure shows a reduction of the polyene strain, while torsional twisting of the beta-ionone ring is maintained. Distortion of the retinal conformation is interpreted through substituent control of receptor activation. Steric hindrance between trans retinal and Trp265 can trigger formation of the subsequent activated meta II state. Our results are pertinent to quantum and molecular mechanics simulations of ligands bound to GPCRs, and illustrate how (2)H NMR can be applied to study their biological mechanisms of action.
Collapse
Affiliation(s)
- Andrey V. Struts
- Department of Chemistry, University of Arizona, Tucson, Arizona 85721, USA
| | - Gilmar F. J. Salgado
- Department of Biochemistry & Molecular Biophysics, University of Arizona, Tucson, Arizona 85721, USA
| | - Katsunori Tanaka
- Department of Chemistry, Columbia University, New York, New York 10027, USA
| | - Sonja Krane
- Department of Chemistry, Columbia University, New York, New York 10027, USA
| | - Koji Nakanishi
- Department of Chemistry, Columbia University, New York, New York 10027, USA
| | - Michael F. Brown
- Department of Chemistry, University of Arizona, Tucson, Arizona 85721, USA
- Department of Biochemistry & Molecular Biophysics, University of Arizona, Tucson, Arizona 85721, USA
- Department of Physics, University of Arizona, Tucson, Arizona 85721, USA
- Corresponding author:
| |
Collapse
|
41
|
Ader C, Spoerner M, Kalbitzer HR, Brunner E. Solid-state 31P NMR spectroscopy of precipitated guanine nucleotide-binding protein Ras in complexes with its effector molecules Raf kinase and RalGDS. J Phys Chem B 2007; 111:2752-7. [PMID: 17315921 DOI: 10.1021/jp067792p] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Liquid-state 31P NMR spectroscopy is a well-established method for the study of guanine nucleotide-binding proteins (GNB proteins) such as the proto-oncogene Ras. Solid-state 31P NMR spectroscopy could meanwhile also be used to study microcrystalline samples of Ras as well as its partial loss-of-function mutants Ras(T35S) and Ras(T35A). However, solid-state NMR studies of the latter mutants in complex with effector molecules such as RalGDS or Raf kinase were so far prevented, since it has been impossible to crystallize these complexes yet. The aim of the present contribution is to make such complexes accessible to solid-state 31P NMR spectroscopy by the application of precipitation methods. The complex formed by Ras(T35S) and Raf kinase is preserved during precipitation. In contrast, the weakly bound complex of Ras(T35S) with RalGDS is dissociated or at least perturbed by the precipitation procedure. Solid-state 31P NMR experiments on precipitates of these complexes deliver spectra of high resolution and signal-to-noise ratio which allows the application of two-dimensional techniques. Precipitates prepared using polyethylene glycol 6000 (PEG) as precipitant were found to exhibit spectra of maximum resolution and signal-to-noise ratio. Interestingly, the 31P signal due to the alpha-phosphate of GppNHp bound to Ras(T35S) in crystalline samples or aged precipitates has a significantly different isotropic chemical shift than in the liquid state or in freshly prepared precipitates. This directly indicates that the crystal structure differs from the equilibrium solution structure at least in the neighborhood of the alpha-phosphate group.
Collapse
Affiliation(s)
- Christian Ader
- Institute of Biophysics and Physical Biochemistry, University of Regensburg, D-93040 Regensburg, Germany
| | | | | | | |
Collapse
|
42
|
Zhao X, Nagai Y, Reeves PJ, Kiley P, Khorana HG, Zhang S. Designer short peptide surfactants stabilize G protein-coupled receptor bovine rhodopsin. Proc Natl Acad Sci U S A 2006; 103:17707-12. [PMID: 17098868 PMCID: PMC1693811 DOI: 10.1073/pnas.0607167103] [Citation(s) in RCA: 149] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2006] [Indexed: 11/18/2022] Open
Abstract
Membrane proteins play vital roles in every aspect of cellular activities. To study diverse membrane proteins, it is crucial to select the right surfactants to stabilize them for analysis. Despite much effort, little progress has been made in elucidating their structure and function, largely because of a lack of suitable surfactants. Here we report the stabilization of a G protein-coupled receptor bovine rhodopsin in solution, using a new class of designer short and simple peptide surfactants. These surfactants consist of seven amino acids with a hydrophilic head, aspartic acid or lysine, and a hydrophobic tail with six consecutive alanines. These peptide surfactants not only enhance the stability of bovine rhodopsin in the presence of lipids and the common surfactants n-dodecyl-beta-D-maltoside and octyl-D-glucoside, but they also significantly stabilize rhodopsin under thermal denaturation conditions, even after lipids are removed. These peptide surfactants are simple, versatile, effective, and affordable. They represent a designer molecular nanomaterial for use in studies of diverse elusive membrane proteins.
Collapse
Affiliation(s)
- Xiaojun Zhao
- *Center for Biomedical Engineering, NE47-379
- Institute for Nanobiomedical Technology and Membrane Biology, Sichuan University, Chengdu, Sichuan 610065, China
- State Key Laboratory of Biotherapy of Human Diseases, Cancer Center, West China Hospital, West China Medical School, Sichuan University, Chengdu, Sichuan 610041, China; and
| | - Yusuke Nagai
- *Center for Biomedical Engineering, NE47-379
- Menicon Co., Ltd., 5-1-10 Takamoridai, Kasugai, Aichi 487-0032, Japan
| | - Philip J. Reeves
- Departments of Biology and Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139-4307
| | | | - H. Gobind Khorana
- Departments of Biology and Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139-4307
| | - Shuguang Zhang
- *Center for Biomedical Engineering, NE47-379
- Center for Bits and Atoms, and
| |
Collapse
|
43
|
Yeagle PL, Albert AD. G-protein coupled receptor structure. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2006; 1768:808-24. [PMID: 17097603 DOI: 10.1016/j.bbamem.2006.10.002] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2006] [Revised: 10/02/2006] [Accepted: 10/05/2006] [Indexed: 11/18/2022]
Abstract
Because of their central role in regulation of cellular function, structure/function relationships for G-protein coupled receptors (GPCR) are of vital importance, yet only recently have sufficient data been obtained to begin mapping those relationships. GPCRs regulate a wide range of cellular processes, including the senses of taste, smell, and vision, and control a myriad of intracellular signaling systems in response to external stimuli. Many diseases are linked to GPCRs. A critical need exists for structural information to inform studies on mechanism of receptor action and regulation. X-ray crystal structures of only one GPCR, in an inactive state, have been obtained to date. However considerable structural information for a variety of GPCRs has been obtained using non-crystallographic approaches. This review begins with a review of the very earliest GPCR structural information, mostly derived from rhodopsin. Because of the difficulty in crystallizing GPCRs for X-ray crystallography, the extensive published work utilizing alternative approaches to GPCR structure is reviewed, including determination of three-dimensional structure from sparse constraints. The available X-ray crystallographic analyses on bovine rhodopsin are reviewed as the only available high-resolution structures for any GPCR. Structural information available on ligand binding to several receptors is included. The limited information on excited states of receptors is also reviewed. It is concluded that while considerable basic structural information has been obtained, more data are needed to describe the molecular mechanism of activation of a GPCR.
Collapse
Affiliation(s)
- Philip L Yeagle
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, CT 06269, USA.
| | | |
Collapse
|
44
|
Iuga A, Spoerner M, Ader C, Brunner E, Kalbitzer HR. Rapid assignment of solution 31P NMR spectra of large proteins by solid-state spectroscopy. Biochem Biophys Res Commun 2006; 346:301-5. [PMID: 16759643 DOI: 10.1016/j.bbrc.2006.05.116] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2006] [Accepted: 05/19/2006] [Indexed: 11/22/2022]
Abstract
The application of the (31)P NMR spectroscopy to large proteins or protein complexes in solution is hampered by a relatively low intrinsic sensitivity coupled with large line widths. Therefore, the assignment of the phosphorus signals by two-dimensional NMR methods in solution is often extremely time consuming. In contrast, the quality of solid-state NMR spectra is not dependent on the molecular mass and the solubility of the protein. For the complex of Ras with the GTP-analogue GppCH(2)p we show solid-state (31)P NMR methods to be more sensitive by almost one order of magnitude than liquid-state NMR. Thus, solid-state NMR seems to be the method of choice for obtaining the resonance assignment of the phosphorus signals of protein complexes in solution. Experiments on Ras.GDP complexes show that the microcrystalline sample can be substituted by a precipitate of the sample and that unexpectedly the two structural states observed earlier in solution are present in crystals as well.
Collapse
Affiliation(s)
- Adriana Iuga
- Universität Regensburg, Institut für Biophysik und physikalische Biochemie, D-93040 Regensburg, Germany
| | | | | | | | | |
Collapse
|
45
|
Roberts NW. The optics of vertebrate photoreceptors: anisotropy and form birefringence. Vision Res 2006; 46:3259-66. [PMID: 16707145 DOI: 10.1016/j.visres.2006.03.019] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2005] [Revised: 03/17/2006] [Accepted: 03/17/2006] [Indexed: 10/24/2022]
Abstract
The optics of vertebrate photoreceptors have been investigated with specific reference to the effect of form birefringence. The complex dielectric tensor of the lamellar-like outer segment structure has been derived, allowing the transverse spectral absorbance to be calculated for different incident polarizations. These results were used to calculate the changes in the cellular dichroic ratio as a function of both the volume occupied by the bilayers and the real and complex parts of the intrinsic birefringence of the bilayers. Physiologically realistic values of these parameters show the cellular dichroic ratio to be greater than the bilayer dichroic ratio by a factor of approximately 1.3. Furthermore, the calculations of spectral absorbance indicate that form birefringence may affect measurements of optical density in transversely orientated outer segments.
Collapse
Affiliation(s)
- N W Roberts
- School of Physics and Astronomy, University of Manchester, Manchester M13 9PL, UK.
| |
Collapse
|
46
|
Gascón JA, Sproviero EM, Batista VS. Computational studies of the primary phototransduction event in visual rhodopsin. Acc Chem Res 2006; 39:184-93. [PMID: 16548507 DOI: 10.1021/ar050027t] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
This Account addresses recent advances in the elucidation of the detailed molecular rearrangements due to the primary photochemical event in rhodopsin, a prototypical G-protein-coupled receptor (GPCR) responsible for the signal transmission cascade in the vertebrate vision process. The reviewed studies provide fundamental insight on long-standing problems regarding the assembly and function of the individual residues and bound water molecules that form the rhodopsin active site, a center that catalyzes the 11-cis/all-trans isomerization of the retinyl chromophore in the primary step of the phototransduction mechanism. Emphasis is placed on the authors' recent computational studies, based on state-of-the-art quantum mechanics/molecular mechanics (QM/MM) hybrid methods, addressing the structural refinement of the retinyl chromophore binding site in high-resolution X-ray structures of bovine visual rhodopsin, the energy storage mechanism, and the molecular origin of spectroscopic changes due to the primary photochemical event.
Collapse
Affiliation(s)
- José A Gascón
- Department of Chemistry, Yale University, P. O. Box 208107, New Haven, CT 06520-8107, USA
| | | | | |
Collapse
|
47
|
Kholmurodov KT, Feldman TB, Ostrovsky MA. Visual pigment rhodopsin : a computer simulation of the molecular dynamics of 11-cis-retinal chromophore and amino-acid residues in the chromophore centre. MENDELEEV COMMUNICATIONS 2006. [DOI: 10.1070/mc2006v016n01abeh002255] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
|
48
|
Vogel A, Katzka CP, Waldmann H, Arnold K, Brown MF, Huster D. Lipid Modifications of a Ras Peptide Exhibit Altered Packing and Mobility versus Host Membrane as Detected by 2H Solid-State NMR. J Am Chem Soc 2005; 127:12263-72. [PMID: 16131204 DOI: 10.1021/ja051856c] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The human N-ras protein binds to cellular membranes by insertion of two covalently bound posttranslational lipid modifications, which is crucial for its function in signal transduction and cell proliferation. Mutations in ras may lead to unregulated cell growth and eventually cancer, making it an important therapeutic target. Here we have investigated the molecular details of the membrane binding mechanism. A heptapeptide derived from the C-terminus of the human N-ras protein was synthesized including two hexadecyl modifications. Solid-state 2H NMR was used to determine the packing and molecular dynamics of the ras lipid chains as well as the phospholipid matrix. Separately labeling the chains of the peptide and the phospholipids with 2H enabled us to obtain atomically resolved parameters relevant to their structural dynamics. While the presence of ras only marginally affected the packing of DMPC membranes, dramatically lower order parameters (S(CD)) were observed for the ras acyl chains indicating modified packing properties. Essentially identical projected lengths of the 16:0 ras chains and the 14:0 DMPC chains were found, implying that the polypeptide backbone is located at the lipid-water interface. Dynamical properties of both the ras and phospholipid chains were determined from spin-lattice 2H relaxation (R1Z) measurements. Plots of R1Z rates versus the corresponding squared segmental order parameters revealed striking differences. We propose the ras peptide is confined to microdomains containing DMPC chains which are in exchange with the bulk bilayer on the 2H NMR time scale (approximately 10(-5) s). Compared to the host DMPC matrix, the ras lipid modifications are extremely flexible and undergo relatively large amplitude motions. It is hypothesized that this flexibility is a requirement for the optimal anchoring of lipid-modified proteins to cellular membranes.
Collapse
Affiliation(s)
- Alexander Vogel
- Biotechnological-Biomedical Center of the University of Leipzig, D-04107 Leipzig, Germany
| | | | | | | | | | | |
Collapse
|
49
|
Seidel K, Etzkorn M, Heise H, Becker S, Baldus M. High-Resolution Solid-State NMR Studies on Uniformly [13C,15N]-Labeled Ubiquitin. Chembiochem 2005; 6:1638-47. [PMID: 16094694 DOI: 10.1002/cbic.200500085] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Understanding of the effects of intermolecular interactions, molecular dynamics, and sample preparation on high-resolution magic-angle spinning NMR data is currently limited. Using the example of a uniformly [13C,15N]-labeled sample of ubiquitin, we discuss solid-state NMR methods tailored to the construction of 3D molecular structure and study the influence of solid-phase protein preparation on solid-state NMR spectra. A comparative analysis of 13C', 13Calpha, and 13Cbeta resonance frequencies suggests that 13C chemical-shift variations are most likely to occur in protein regions that exhibit an enhanced degree of molecular mobility. Our results can be refined by additional solid-state NMR techniques and serve as a reference for ongoing efforts to characterize the structure and dynamics of (membrane) proteins, protein complexes, and other biomolecules by high-resolution solid-state NMR.
Collapse
Affiliation(s)
- Karsten Seidel
- Department of NMR-Based Structural Biology, Max Planck Institute for Biophysical Chemistry, 37077 Göttingen, Germany
| | | | | | | | | |
Collapse
|
50
|
Watts A. Solid-state NMR in drug design and discovery for membrane-embedded targets. Nat Rev Drug Discov 2005; 4:555-68. [PMID: 16052240 DOI: 10.1038/nrd1773] [Citation(s) in RCA: 97] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Observing drugs and ligands at their site of action in membrane proteins is now possible through the use of a development in biomolecular NMR spectroscopy known as solid-state NMR. Even large, functionally active complexes are being examined using this method, with structural details being resolved at super-high subnanometre resolution. This is supplemented by detailed dynamic and electronic information about the surrounding ligand environment, and gives surprising new insights into the way in which ligands bind, which can aid drug design.
Collapse
Affiliation(s)
- Anthony Watts
- Biomembrane Structure Unit, Biochemistry Department, University of Oxford, Oxford OX1 3QU, UK.
| |
Collapse
|