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Rosenberg EM, Jian X, Soubias O, Jackson RA, Gladu E, Andersen E, Esser L, Sodt AJ, Xia D, Byrd RA, Randazzo PA. Point mutations in Arf1 reveal cooperative effects of the N-terminal extension and myristate for GTPase-activating protein catalytic activity. PLoS One 2024; 19:e0295103. [PMID: 38574162 PMCID: PMC10994351 DOI: 10.1371/journal.pone.0295103] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2023] [Accepted: 03/05/2024] [Indexed: 04/06/2024] Open
Abstract
The ADP-ribosylation factors (Arfs) constitute a family of small GTPases within the Ras superfamily, with a distinguishing structural feature of a hypervariable N-terminal extension of the G domain modified with myristate. Arf proteins, including Arf1, have roles in membrane trafficking and cytoskeletal dynamics. While screening for Arf1:small molecule co-crystals, we serendipitously solved the crystal structure of the non-myristoylated engineered mutation [L8K]Arf1 in complex with a GDP analogue. Like wild-type (WT) non-myristoylated Arf1•GDP, we observed that [L8K]Arf1 exhibited an N-terminal helix that occludes the hydrophobic cavity that is occupied by the myristoyl group in the GDP-bound state of the native protein. However, the helices were offset from one another due to the L8K mutation, with a significant change in position of the hinge region connecting the N-terminus to the G domain. Hypothesizing that the observed effects on behavior of the N-terminus affects interaction with regulatory proteins, we mutated two hydrophobic residues to examine the role of the N-terminal extension for interaction with guanine nucleotide exchange factors (GEFs) and GTPase Activating Proteins (GAPs. Different than previous studies, all mutations were examined in the context of myristoylated Arf. Mutations had little or no effect on spontaneous or GEF-catalyzed guanine nucleotide exchange but did affect interaction with GAPs. [F13A]myrArf1 was less than 1/2500, 1/1500, and 1/200 efficient as substrate for the GAPs ASAP1, ARAP1 and AGAP1; however, [L8A/F13A]myrArf1 was similar to WT myrArf1. Using molecular dynamics simulations, the effect of the mutations on forming alpha helices adjacent to a membrane surface was examined, yet no differences were detected. The results indicate that lipid modifications of GTPases and consequent anchoring to a membrane influences protein function beyond simple membrane localization. Hypothetical mechanisms are discussed.
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Affiliation(s)
- Eric M. Rosenberg
- Laboratory of Cellular and Molecular Biology, Center for Cancer Research, National Cancer Institute, Bethesda, MD, United States of America
| | - Xiaoying Jian
- Laboratory of Cellular and Molecular Biology, Center for Cancer Research, National Cancer Institute, Bethesda, MD, United States of America
| | - Olivier Soubias
- Section of Macromolecular NMR, Center for Structural Biology Laboratory, Center for Cancer Research, National Cancer Institute, Frederick, MD, United States of America
| | - Rebekah A. Jackson
- Section of Macromolecular NMR, Center for Structural Biology Laboratory, Center for Cancer Research, National Cancer Institute, Frederick, MD, United States of America
| | - Erin Gladu
- Laboratory of Cellular and Molecular Biology, Center for Cancer Research, National Cancer Institute, Bethesda, MD, United States of America
| | - Emily Andersen
- Laboratory of Cellular and Molecular Biology, Center for Cancer Research, National Cancer Institute, Bethesda, MD, United States of America
| | - Lothar Esser
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland, United States of America
| | - Alexander J. Sodt
- Unit of Membrane Chemical Physics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, MD, United States of America
| | - Di Xia
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland, United States of America
| | - R. Andrew Byrd
- Section of Macromolecular NMR, Center for Structural Biology Laboratory, Center for Cancer Research, National Cancer Institute, Frederick, MD, United States of America
| | - Paul A. Randazzo
- Laboratory of Cellular and Molecular Biology, Center for Cancer Research, National Cancer Institute, Bethesda, MD, United States of America
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Zhang Y, Soubias O, Pant S, Heinrich F, Vogel A, Li J, Li Y, Clifton LA, Daum S, Bacia K, Huster D, Randazzo PA, Lösche M, Tajkhorshid E, Byrd RA. Myr-Arf1 conformational flexibility at the membrane surface sheds light on the interactions with ArfGAP ASAP1. Nat Commun 2023; 14:7570. [PMID: 37989735 PMCID: PMC10663523 DOI: 10.1038/s41467-023-43008-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2023] [Accepted: 10/30/2023] [Indexed: 11/23/2023] Open
Abstract
ADP-ribosylation factor 1 (Arf1) interacts with multiple cellular partners and membranes to regulate intracellular traffic, organelle structure and actin dynamics. Defining the dynamic conformational landscape of Arf1 in its active form, when bound to the membrane, is of high functional relevance and key to understanding how Arf1 can alter diverse cellular processes. Through concerted application of nuclear magnetic resonance (NMR), neutron reflectometry (NR) and molecular dynamics (MD) simulations, we show that, while Arf1 is anchored to the membrane through its N-terminal myristoylated amphipathic helix, the G domain explores a large conformational space, existing in a dynamic equilibrium between membrane-associated and membrane-distal conformations. These configurational dynamics expose different interfaces for interaction with effectors. Interaction with the Pleckstrin homology domain of ASAP1, an Arf-GTPase activating protein (ArfGAP), restricts motions of the G domain to lock it in what seems to be a conformation exposing functionally relevant regions.
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Affiliation(s)
- Yue Zhang
- Center for Structural Biology, Center for Cancer Research, National Cancer Institute, Frederick, MD, 21702-1201, USA
- Ring Therapeutics, Inc., Cambridge, MA, USA
| | - Olivier Soubias
- Center for Structural Biology, Center for Cancer Research, National Cancer Institute, Frederick, MD, 21702-1201, USA
| | - Shashank Pant
- Theoretical and Computational Biophysics Group, NIH Center for Macromolecular Modeling and Visualization, Beckman Institute for Advanced Science and Technology, Department of Biochemistry, and Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA
- Loxo Oncology at Lilly, Louisville, CO, USA
| | - Frank Heinrich
- Department of Physics, Carnegie Mellon University, Pittsburgh, PA, USA
- NIST Center for Neutron Research, Gaithersburg, MD, USA
| | - Alexander Vogel
- Institute of Medical Physics and Biophysics, University of Leipzig, 04107, Leipzig, Germany
| | - Jess Li
- Center for Structural Biology, Center for Cancer Research, National Cancer Institute, Frederick, MD, 21702-1201, USA
| | - Yifei Li
- Center for Structural Biology, Center for Cancer Research, National Cancer Institute, Frederick, MD, 21702-1201, USA
- Vonsun Pharmatech Co., Ltd., Suzhou, China
| | - Luke A Clifton
- ISIS Neutron and Muon Source, Rutherford Appleton Laboratory, Didcot, Oxfordshire, OX11 0QX, UK
| | - Sebastian Daum
- Institute for Chemistry, Department of Biophysical Chemistry, Martin Luther University Halle-Wittenberg, Kurt-Mothes-Str. 3A, 06120, Halle, Germany
| | - Kirsten Bacia
- Institute for Chemistry, Department of Biophysical Chemistry, Martin Luther University Halle-Wittenberg, Kurt-Mothes-Str. 3A, 06120, Halle, Germany
| | - Daniel Huster
- Institute of Medical Physics and Biophysics, University of Leipzig, 04107, Leipzig, Germany
| | - Paul A Randazzo
- Laboratory of Cellular and Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Mathias Lösche
- Department of Physics, Carnegie Mellon University, Pittsburgh, PA, USA
- NIST Center for Neutron Research, Gaithersburg, MD, USA
- Department of Biomedical Engineering, Carnegie Mellon University, Pittsburgh, PA, USA
| | - Emad Tajkhorshid
- Theoretical and Computational Biophysics Group, NIH Center for Macromolecular Modeling and Visualization, Beckman Institute for Advanced Science and Technology, Department of Biochemistry, and Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA
| | - R Andrew Byrd
- Center for Structural Biology, Center for Cancer Research, National Cancer Institute, Frederick, MD, 21702-1201, USA.
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Soubias O, Sodt AJ, Teague WE, Hines KG, Gawrisch K. Physiological changes in bilayer thickness induced by cholesterol control GPCR rhodopsin function. Biophys J 2023; 122:973-983. [PMID: 36419350 PMCID: PMC10111215 DOI: 10.1016/j.bpj.2022.11.2937] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2022] [Revised: 11/15/2022] [Accepted: 11/21/2022] [Indexed: 11/24/2022] Open
Abstract
We monitored the effect on function of the G-protein-coupled receptor (GPCR) rhodopsin from small, stepwise changes in bilayer thickness induced by cholesterol. Over a range of phosphatidylcholine bilayers with hydrophobic thickness from ≈21 Å to 38 Å, the metarhodopsin-I (MI)/metarhodopsin-II (MII) equilibrium was monitored with UV-visible spectroscopy while ordering of hydrocarbon chains was probed by 2H-NMR. Addition of cholesterol shifted equilibrium toward MII for bilayers thinner than the average length of hydrophobic transmembrane helices (27 Å) and to MI for thicker bilayers, while small bilayer thickness changes within the range of the protein hydrophobic thickness drastically up- or downregulated MII formation. The cholesterol-induced shifts toward MII for thinner membranes correlated with the cholesterol-induced increase of bilayer hydrophobic thickness measured by NMR, consistent with continuum elastic modeling. The energetic penalty of adding cholesterol to thick bilayers caused rhodopsin oligomerization and a shift toward MI. In membranes of physiological thickness, changes in bilayer mechanical properties induced by cholesterol potentiated the interplay between bilayer and protein thickness resulting in large swings of the MI-MII equilibrium. In membrane containing cholesterol, elastic deformations near the protein are a dominant energetic contribution to the functional equilibrium of the model GPCR rhodopsin.
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Affiliation(s)
- Olivier Soubias
- Macromolecular NMR Section, Center for Structural Biology, Center for Cancer Research, NCI, NIH, Frederick, Maryland.
| | - Alexander J Sodt
- Unit on Membrane Chemical Physics, Eunice Kennedy Shriver NICHD, NIH, Bethesda, Maryland
| | - Walter E Teague
- Section of NMR, Laboratory of Membrane Biochemistry and Biophysics, NIAAA, NIH, Bethesda, Maryland
| | - Kirk G Hines
- Section of NMR, Laboratory of Membrane Biochemistry and Biophysics, NIAAA, NIH, Bethesda, Maryland
| | - Klaus Gawrisch
- Section of NMR, Laboratory of Membrane Biochemistry and Biophysics, NIAAA, NIH, Bethesda, Maryland
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Zimmerberg J, Soubias O, Pastor RW. Special issue for Klaus Gawrisch. Biophys J 2023; 122:E1-E8. [PMID: 36921597 PMCID: PMC10111273 DOI: 10.1016/j.bpj.2023.02.022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2023] [Revised: 02/15/2023] [Accepted: 02/15/2023] [Indexed: 03/17/2023] Open
Affiliation(s)
- Joshua Zimmerberg
- Section on Integrative Biophysics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA
| | - Olivier Soubias
- Macromolecular NMR Section, Center for Structural Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Frederick, MD, USA
| | - Richard W Pastor
- Laboratory of Computational Biology, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA.
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5
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Soubias O, Zhang Y, Jackson R, Li J, Byrd A. Structural insights into the complex between Arf1 and ASAP1 at the membrane surface by NMR. Biophys J 2023; 122:448a. [PMID: 36784301 DOI: 10.1016/j.bpj.2022.11.2416] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/12/2023] Open
Affiliation(s)
- Olivier Soubias
- Center for Structural Biology, Macromolecular NMR Section, National Cancer Institute, National Institutes of Health, Frederick, MD, USA
| | - Yue Zhang
- Center for Structural Biology, Macromolecular NMR Section, National Cancer Institute, National Institutes of Health, Frederick, MD, USA
| | - Rebekah Jackson
- Center for Structural Biology, Macromolecular NMR Section, National Cancer Institute, National Institutes of Health, Frederick, MD, USA
| | - Jess Li
- Center for Structural Biology, Macromolecular NMR Section, National Cancer Institute, National Institutes of Health, Frederick, MD, USA
| | - Andrew Byrd
- Center for Structural Biology, Macromolecular NMR Section, National Cancer Institute, National Institutes of Health, Frederick, MD, USA
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Rosenberg EM, Jian X, Soubias O, Yoon HY, Yadav MP, Hammoudeh S, Pallikkuth S, Akpan I, Chen PW, Maity TK, Jenkins LM, Yohe ME, Byrd RA, Randazzo PA. The small molecule inhibitor NAV-2729 has a complex target profile including multiple ADP-ribosylation factor regulatory proteins. J Biol Chem 2023; 299:102992. [PMID: 36758799 PMCID: PMC10023970 DOI: 10.1016/j.jbc.2023.102992] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2022] [Revised: 01/18/2023] [Accepted: 01/20/2023] [Indexed: 02/11/2023] Open
Abstract
The ADP-ribosylation factor (Arf) GTPases and their regulatory proteins are implicated in cancer progression. NAV-2729 was previously identified as a specific inhibitor of Arf6 that reduced progression of uveal melanoma in an orthotopic xenograft. Here, our goal was to assess the inhibitory effects of NAV-2729 on the proliferation of additional cell types. We found NAV-2729 inhibited proliferation of multiple cell lines, but Arf6 expression did not correlate with NAV-2729 sensitivity, and knockdown of Arf6 affected neither cell viability nor sensitivity to NAV-2729. Furthermore, binding to native Arf6 was not detected; however, we determined that NAV-2729 inhibited both Arf exchange factors and Arf GTPase-activating proteins. ASAP1, a GTPase-activating protein linked to cancer progression, was further investigated. We demonstrated that NAV-2729 bound to the PH domain of ASAP1 and changed ASAP1 cellular distribution. However, ASAP1 knockdown did not fully recapitulate the cytoskeletal effects of NAV-2729 nor affect cell proliferation. Finally, our screens identified 48 other possible targets of NAV-2729. These results illustrate the complexities of defining targets of small molecules and identify NAV-2729 as a model PH domain-binding inhibitor.
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Affiliation(s)
- Eric M Rosenberg
- Laboratory of Cellular and Molecular Biology, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland, USA
| | - Xiaoying Jian
- Laboratory of Cellular and Molecular Biology, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland, USA
| | - Olivier Soubias
- Center for Structural Biology Laboratory, Center for Cancer Research, National Cancer Institute, Frederick, Maryland, USA
| | - Hye-Young Yoon
- Laboratory of Cellular and Molecular Biology, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland, USA
| | - Mukesh P Yadav
- Laboratory of Cellular and Molecular Biology, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland, USA
| | - Sarah Hammoudeh
- Laboratory of Cellular and Molecular Biology, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland, USA
| | - Sandeep Pallikkuth
- Laboratory of Cellular and Molecular Biology, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland, USA
| | - Itoro Akpan
- Laboratory of Cellular and Molecular Biology, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland, USA
| | - Pei-Wen Chen
- Department of Biology, Williams College, Williamstown, Massachusetts, USA
| | - Tapan K Maity
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland, USA
| | - Lisa M Jenkins
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland, USA
| | - Marielle E Yohe
- Pediatric Oncology Branch, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland, USA; Laboratory of Cell and Developmental Signaling, Center for Cancer Research, Frederick, Maryland, USA
| | - R Andrew Byrd
- Center for Structural Biology Laboratory, Center for Cancer Research, National Cancer Institute, Frederick, Maryland, USA
| | - Paul A Randazzo
- Laboratory of Cellular and Molecular Biology, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland, USA.
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7
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Papoutsis BM, Soubias O, Li J, Zhang Y, Byrd RA. Segmental labeling of ASAP1-PZA for structural studies by nuclear magnetic resonance and neutron reflectometry. Biophys J 2022. [DOI: 10.1016/j.bpj.2021.11.1617] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022] Open
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8
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Zhang Y, Soubias O, Pant S, Heinrich F, Vogel A, Li J, Huster D, Randazzo P, Losche M, Tajkhorshid E, Byrd RA. Myr-Arf1 conformational flexibility at the membrane surface: insights for its interactions with ASAP1. Biophys J 2022. [DOI: 10.1016/j.bpj.2021.11.465] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022] Open
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9
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Soubias O, Pant S, Zhang Y, Tajkhorshid E, Byrd RA. Probing the PIP2 dependence of the ASAP1 PH domain membrane binding by NMR and MD simulations. Biophys J 2022. [DOI: 10.1016/j.bpj.2021.11.2300] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022] Open
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10
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Soubias O. Squaring off with G protein-coupled receptors function in polymer nanoscale lipid bilayers. Biophys J 2021; 120:4299-4300. [PMID: 34537110 DOI: 10.1016/j.bpj.2021.09.013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2021] [Revised: 08/06/2021] [Accepted: 09/07/2021] [Indexed: 11/19/2022] Open
Affiliation(s)
- Olivier Soubias
- Center for Structural Biology, Center for Cancer Research, National Cancer Institute, Frederick, Maryland, USA.
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Soubias O, Pant S, Heinrich F, Zhang Y, Randazzo P, Loesche M, Tajkhorshid E, Byrd RA. Membrane Surface Recognition by the ASAP1 Ph Domain and Consequences for Interactions with the Small GTPASE ARF1. Biophys J 2021. [DOI: 10.1016/j.bpj.2020.11.887] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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Soubias O, Pant S, Heinrich F, Zhang Y, Roy NS, Li J, Jian X, Yohe ME, Randazzo PA, Lösche M, Tajkhorshid E, Byrd RA. Membrane surface recognition by the ASAP1 PH domain and consequences for interactions with the small GTPase Arf1. Sci Adv 2020; 6:6/40/eabd1882. [PMID: 32998886 PMCID: PMC7527224 DOI: 10.1126/sciadv.abd1882] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/05/2020] [Accepted: 08/04/2020] [Indexed: 05/05/2023]
Abstract
Adenosine diphosphate-ribosylation factor (Arf) guanosine triphosphatase-activating proteins (GAPs) are enzymes that need to bind to membranes to catalyze the hydrolysis of guanosine triphosphate (GTP) bound to the small GTP-binding protein Arf. Binding of the pleckstrin homology (PH) domain of the ArfGAP With SH3 domain, ankyrin repeat and PH domain 1 (ASAP1) to membranes containing phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2] is key for maximum GTP hydrolysis but not fully understood. By combining nuclear magnetic resonance, neutron reflectometry, and molecular dynamics simulation, we show that binding of multiple PI(4,5)P2 molecules to the ASAP1 PH domain (i) triggers a functionally relevant allosteric conformational switch and (ii) maintains the PH domain in a well-defined orientation, allowing critical contacts with an Arf1 mimic to occur. Our model provides a framework to understand how binding of the ASAP1 PH domain to PI(4,5)P2 at the membrane may play a role in the regulation of ASAP1.
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Affiliation(s)
- Olivier Soubias
- Structural Biophysics Laboratory, Center for Cancer Research, National Cancer Institute, Frederick, MD 21702-1201, USA
| | - Shashank Pant
- NIH Center for Macromolecular Modeling and Bioinformatics, Beckman Institute for Advanced Science and Technology, Department of Biochemistry, Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Frank Heinrich
- Department of Physics, Carnegie Mellon University, Pittsburgh, PA 15213, USA
- NIST Center for Neutron Research, Gaithersburg, MD 20878, USA
| | - Yue Zhang
- Structural Biophysics Laboratory, Center for Cancer Research, National Cancer Institute, Frederick, MD 21702-1201, USA
| | - Neeladri Sekhar Roy
- Laboratory of Cellular and Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Jess Li
- Structural Biophysics Laboratory, Center for Cancer Research, National Cancer Institute, Frederick, MD 21702-1201, USA
| | - Xiaoying Jian
- Laboratory of Cellular and Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Marielle E Yohe
- Pediatric Oncology Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Paul A Randazzo
- Laboratory of Cellular and Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Mathias Lösche
- Department of Physics, Carnegie Mellon University, Pittsburgh, PA 15213, USA.
- NIST Center for Neutron Research, Gaithersburg, MD 20878, USA
- Department of Biomedical Engineering, Carnegie Mellon University, Pittsburgh, PA 15213, USA
| | - Emad Tajkhorshid
- NIH Center for Macromolecular Modeling and Bioinformatics, Beckman Institute for Advanced Science and Technology, Department of Biochemistry, Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
| | - R Andrew Byrd
- Structural Biophysics Laboratory, Center for Cancer Research, National Cancer Institute, Frederick, MD 21702-1201, USA.
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14
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Zhang Y, Soubias O, Byrd A. High Quality Methyl-TROSY NMR Studies of the Interactions Between the Small GTPase ARF1 and Its ArfGAP ASAP1 at the Membrane Surface. Biophys J 2020. [DOI: 10.1016/j.bpj.2019.11.274] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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15
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Li J, Zhang Y, Soubias O, Khago D, Chao FA, Li Y, Shaw K, Byrd RA. Optimization of sortase A ligation for flexible engineering of complex protein systems. J Biol Chem 2020; 295:2664-2675. [PMID: 31974162 DOI: 10.1074/jbc.ra119.012039] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2019] [Revised: 01/22/2020] [Indexed: 01/06/2023] Open
Abstract
Engineering and bioconjugation of proteins is a critically valuable tool that can facilitate a wide range of biophysical and structural studies. The ability to orthogonally tag or label a domain within a multidomain protein may be complicated by undesirable side reactions to noninvolved domains. Furthermore, the advantages of segmental (or domain-specific) isotopic labeling for NMR, or deuteration for neutron scattering or diffraction, can be realized by an efficient ligation procedure. Common methods-expressed protein ligation, protein trans-splicing, and native chemical ligation-each have specific limitations. Here, we evaluated the use of different variants of Staphylococcus aureus sortase A for a range of ligation reactions and demonstrate that conditions can readily be optimized to yield high efficiency (i.e. completeness of ligation), ease of purification, and functionality in detergents. These properties may enable joining of single domains into multidomain proteins, lipidation to mimic posttranslational modifications, and formation of cyclic proteins to aid in the development of nanodisc membrane mimetics. We anticipate that the method for ligating separate domains into a single functional multidomain protein reported here may enable many applications in structural biology.
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Affiliation(s)
- Jess Li
- Structural Biophysics Laboratory, Center for Cancer Research, NCI, National Institutes of Health, Frederick, Maryland 21702-1201
| | - Yue Zhang
- Structural Biophysics Laboratory, Center for Cancer Research, NCI, National Institutes of Health, Frederick, Maryland 21702-1201
| | - Olivier Soubias
- Structural Biophysics Laboratory, Center for Cancer Research, NCI, National Institutes of Health, Frederick, Maryland 21702-1201
| | - Domarin Khago
- Structural Biophysics Laboratory, Center for Cancer Research, NCI, National Institutes of Health, Frederick, Maryland 21702-1201
| | - Fa-An Chao
- Structural Biophysics Laboratory, Center for Cancer Research, NCI, National Institutes of Health, Frederick, Maryland 21702-1201
| | - Yifei Li
- Structural Biophysics Laboratory, Center for Cancer Research, NCI, National Institutes of Health, Frederick, Maryland 21702-1201
| | - Katherine Shaw
- Structural Biophysics Laboratory, Center for Cancer Research, NCI, National Institutes of Health, Frederick, Maryland 21702-1201
| | - R Andrew Byrd
- Structural Biophysics Laboratory, Center for Cancer Research, NCI, National Institutes of Health, Frederick, Maryland 21702-1201.
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Roy NS, Jian X, Soubias O, Zhai P, Hall JR, Dagher JN, Coussens NP, Jenkins LM, Luo R, Akpan IO, Hall MD, Byrd RA, Yohe ME, Randazzo PA. Interaction of the N terminus of ADP-ribosylation factor with the PH domain of the GTPase-activating protein ASAP1 requires phosphatidylinositol 4,5-bisphosphate. J Biol Chem 2019; 294:17354-17370. [PMID: 31591270 DOI: 10.1074/jbc.ra119.009269] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2019] [Revised: 10/02/2019] [Indexed: 12/15/2022] Open
Abstract
Arf GAP with Src homology 3 domain, ankyrin repeat, and pleckstrin homology (PH) domain 1 (ASAP1) is a multidomain GTPase-activating protein (GAP) for ADP-ribosylation factor (ARF)-type GTPases. ASAP1 affects integrin adhesions, the actin cytoskeleton, and invasion and metastasis of cancer cells. ASAP1's cellular function depends on its highly-regulated and robust ARF GAP activity, requiring both the PH and the ARF GAP domains of ASAP1, and is modulated by phosphatidylinositol 4,5-bisphosphate (PIP2). The mechanistic basis of PIP2-stimulated GAP activity is incompletely understood. Here, we investigated whether PIP2 controls binding of the N-terminal extension of ARF1 to ASAP1's PH domain and thereby regulates its GAP activity. Using [Δ17]ARF1, lacking the N terminus, we found that PIP2 has little effect on ASAP1's activity. A soluble PIP2 analog, dioctanoyl-PIP2 (diC8PIP2), stimulated GAP activity on an N terminus-containing variant, [L8K]ARF1, but only marginally affected activity on [Δ17]ARF1. A peptide comprising residues 2-17 of ARF1 ([2-17]ARF1) inhibited GAP activity, and PIP2-dependently bound to a protein containing the PH domain and a 17-amino acid-long interdomain linker immediately N-terminal to the first β-strand of the PH domain. Point mutations in either the linker or the C-terminal α-helix of the PH domain decreased [2-17]ARF1 binding and GAP activity. Mutations that reduced ARF1 N-terminal binding to the PH domain also reduced the effect of ASAP1 on cellular actin remodeling. Mutations in the ARF N terminus that reduced binding also reduced GAP activity. We conclude that PIP2 regulates binding of ASAP1's PH domain to the ARF1 N terminus, which may partially regulate GAP activity.
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Affiliation(s)
- Neeladri Sekhar Roy
- Laboratory of Cellular and Molecular Biology, Center for Cancer Research, NCI, National Institutes of Health, Bethesda, Maryland 20892
| | - Xiaoying Jian
- Laboratory of Cellular and Molecular Biology, Center for Cancer Research, NCI, National Institutes of Health, Bethesda, Maryland 20892
| | - Olivier Soubias
- Structural Biophysics Laboratory, Center for Cancer Research, NCI, National Institutes of Health, Frederick, Maryland 21702
| | - Peng Zhai
- Laboratory of Cellular and Molecular Biology, Center for Cancer Research, NCI, National Institutes of Health, Bethesda, Maryland 20892
| | - Jessica R Hall
- Chemical Genomics Center, National Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, Maryland 20892
| | - Jessica N Dagher
- Chemical Genomics Center, National Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, Maryland 20892
| | - Nathan P Coussens
- Chemical Genomics Center, National Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, Maryland 20892
| | - Lisa M Jenkins
- Laboratory of Cell Biology, Center for Cancer Research, NCI, National Institutes of Health, Bethesda, Maryland 20892
| | - Ruibai Luo
- Laboratory of Cellular and Molecular Biology, Center for Cancer Research, NCI, National Institutes of Health, Bethesda, Maryland 20892
| | - Itoro O Akpan
- Laboratory of Cellular and Molecular Biology, Center for Cancer Research, NCI, National Institutes of Health, Bethesda, Maryland 20892
| | - Matthew D Hall
- Chemical Genomics Center, National Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, Maryland 20892
| | - R Andrew Byrd
- Structural Biophysics Laboratory, Center for Cancer Research, NCI, National Institutes of Health, Frederick, Maryland 21702
| | - Marielle E Yohe
- Laboratory of Cellular and Molecular Biology, Center for Cancer Research, NCI, National Institutes of Health, Bethesda, Maryland 20892 .,Pediatric Oncology Branch, Center for Cancer Research, NCI, National Institutes of Health, Bethesda, Maryland 20892
| | - Paul A Randazzo
- Laboratory of Cellular and Molecular Biology, Center for Cancer Research, NCI, National Institutes of Health, Bethesda, Maryland 20892
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Li Y, Soubias O, Li J, Sun S, Randazzo PA, Byrd RA. Functional Expression and Characterization of Human Myristoylated-Arf1 in Nanodisc Membrane Mimetics. Biochemistry 2019; 58:1423-1431. [PMID: 30735034 DOI: 10.1021/acs.biochem.8b01323] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Lipidated small GTP-binding proteins of the Arf family interact with multiple cellular partners and with membranes to regulate intracellular traffic and organelle structure. Here, we focus on the ADP-ribosylation factor 1 (Arf1), which interacts with numerous proteins in the Arf pathway, such as the ArfGAP ASAP1 that is highly expressed and activated in several cancer cell lines and associated with enhanced migration, invasiveness, and poor prognosis. Understanding the molecular and mechanistic details of Arf1 regulation at the membrane via structural and biophysical studies requires large quantities of fully functional protein bound to lipid bilayers. Here, we report on the production of a functional human Arf1 membrane platform on nanodiscs for biophysical studies. Large scale bacterial production of highly pure, N-myristoylated human Arf1 has been achieved, including complex isotopic labeling for nuclear magnetic resonance (NMR) studies, and the myr-Arf1 can be readily assembled in small nanoscale lipid bilayers (nanodiscs, NDs). It is determined that myr-Arf1 requires a minimum binding surface in the NDs of ∼20 lipids. Fluorescence and NMR were used to establish nucleotide exchange and ArfGAP-stimulated GTP hydrolysis at the membrane, indicating that phophoinositide stimulation of the activity of the ArfGAP ASAP1 is ≥2000-fold. Differences in nonhydrolyzable GTP analogues are observed, and GMPPCP is found to be the most stable. Combined, these observations establish a functional environment for biophysical studies of Arf1 effectors and interactions at the membrane.
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Affiliation(s)
- Yifei Li
- Structural Biophysics Laboratory, Center for Cancer Research , National Cancer Institute , Frederick , Maryland 21702-1201 , United States
| | - Olivier Soubias
- Structural Biophysics Laboratory, Center for Cancer Research , National Cancer Institute , Frederick , Maryland 21702-1201 , United States
| | - Jess Li
- Structural Biophysics Laboratory, Center for Cancer Research , National Cancer Institute , Frederick , Maryland 21702-1201 , United States
| | - Shangjin Sun
- Structural Biophysics Laboratory, Center for Cancer Research , National Cancer Institute , Frederick , Maryland 21702-1201 , United States
| | - Paul A Randazzo
- Laboratory of Cellular and Molecular Biology, Center for Cancer Research , National Cancer Institute , Bethesda , Maryland 20892 , United States
| | - R Andrew Byrd
- Structural Biophysics Laboratory, Center for Cancer Research , National Cancer Institute , Frederick , Maryland 21702-1201 , United States
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Soubias O, Heinrich F, Zhang Y, Li Y, Li J, Silin VI, Randazzo P, Losche M, Byrd RA. Molecular Mechanisms of the Interaction between Arf1 and ASAP1 pH Domain at the Membrane Interface. Biophys J 2019. [DOI: 10.1016/j.bpj.2018.11.2005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
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Li Y, Soubias O, Li J, Randazzo PA, Byrd RA. Interaction Between Myristoylated Human Arf1 and ASAP1 at the Membrane Surface. Biophys J 2018. [DOI: 10.1016/j.bpj.2017.11.225] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022] Open
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Soubias O, Nickels JD, Yeliseev A, Hines KG, Teague WE, Northup J, Katsaras J, Gawrisch K. G Protein-GPCR Interaction Studied by SANS. Biophys J 2018. [DOI: 10.1016/j.bpj.2017.11.3810] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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Soubias O, Nickels JD, Teague WE, Hines KG, Weiss KL, Katsaras J, Gawrisch K. Rhodopsin Dimerization in Membrane Bilayers Revealed by Small Angle Neutron Scattering. Biophys J 2017. [DOI: 10.1016/j.bpj.2016.11.2596] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022] Open
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Sodt AJ, Soubias O, Gawrisch K, Pastor RW. Lipid-Lipid Coupling to Membrane Curvature by Simulation and NMR. Biophys J 2016. [DOI: 10.1016/j.bpj.2015.11.1340] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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Soubias O, Sodt AJ, Teague WE, Hines KG, Gawrisch K. Controlling GPCR Rhodopsin Function by Small, Physiologically Relevant Changes in Bilayer Hydrophobic Thickness. Biophys J 2016. [DOI: 10.1016/j.bpj.2015.11.1142] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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Soubias O, Teague WE, Hines KG, Gawrisch K. The role of membrane curvature elastic stress for function of rhodopsin-like G protein-coupled receptors. Biochimie 2015; 107 Pt A:28-32. [PMID: 25447139 DOI: 10.1016/j.biochi.2014.10.011] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2014] [Accepted: 10/16/2014] [Indexed: 10/24/2022]
Abstract
The human genome encodes about 800 different G protein-coupled receptors (GPCR). They are key molecules in signal transduction pathways that transmit signals of a variety of ligands such as hormones and neurotransmitters to the cell interior. Upon ligand binding, the receptors undergo structural transitions that either enhance or inhibit transmission of a specific signal to the cell interior. Here we discuss results which indicate that transmission of such signals can be strongly modulated by the composition of the lipid matrix into which GPCR are imbedded. Experimental results have been obtained on rhodopsin, a prototype GPCR whose structure and function is representative for the great majority of GPCR in humans. The data shed light on the importance of curvature elastic stress in the lipid domain for function of GPCR.
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Randazzo PA, Jian X, Chen PW, Zhai P, Soubias O, Northup JK. Quantitative Analysis of Guanine Nucleotide Exchange Factors (GEFs) as Enzymes. Cell Logist 2014; 3:e27609. [PMID: 25332840 PMCID: PMC4187004 DOI: 10.4161/cl.27609] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/17/2013] [Revised: 12/19/2013] [Accepted: 12/20/2013] [Indexed: 11/19/2022]
Abstract
The proteins that possess guanine nucleotide exchange factor (GEF) activity, which include about ~800 G protein coupled receptors (GPCRs),1 15 Arf GEFs,2 81 Rho GEFs,3 8 Ras GEFs,4 and others for other families of GTPases,5 catalyze the exchange of GTP for GDP on all regulatory guanine nucleotide binding proteins. Despite their importance as catalysts, relatively few exchange factors (we are aware of only eight for ras superfamily members) have been rigorously characterized kinetically.5-13 In some cases, kinetic analysis has been simplistic leading to erroneous conclusions about mechanism (as discussed in a recent review14). In this paper, we compare two approaches for determining the kinetic properties of exchange factors: (i) examining individual equilibria, and; (ii) analyzing the exchange factors as enzymes. Each approach, when thoughtfully used,14,15 provides important mechanistic information about the exchange factors. The analysis as enzymes is described in further detail. With the focus on the production of the biologically relevant guanine nucleotide binding protein complexed with GTP (G•GTP), we believe it is conceptually simpler to connect the kinetic properties to cellular effects. Further, the experiments are often more tractable than those used to analyze the equilibrium system and, therefore, more widely accessible to scientists interested in the function of exchange factors.
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Affiliation(s)
- Paul A Randazzo
- Laboratory of Cellular and Molecular Biology; National Cancer Institute; Bethesda, MD USA
| | - Xiaoying Jian
- Laboratory of Cellular and Molecular Biology; National Cancer Institute; Bethesda, MD USA
| | - Pei-Wen Chen
- Laboratory of Cellular and Molecular Biology; National Cancer Institute; Bethesda, MD USA
| | - Peng Zhai
- Laboratory of Cellular and Molecular Biology; National Cancer Institute; Bethesda, MD USA
| | - Olivier Soubias
- Laboratory of Membrane Biochemistry and Biophysics; National Institute on Alcohol Abuse and Alcoholism; Rockville, MD USA
| | - John K Northup
- Laboratory of Membrane Biochemistry and Biophysics; National Institute on Alcohol Abuse and Alcoholism; Rockville, MD USA
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Teague WE, Soubias O, Petrache H, Fuller N, Hines KG, Rand RP, Gawrisch K. Elastic properties of polyunsaturated phosphatidylethanolamines influence rhodopsin function. Faraday Discuss 2013; 161:383-459. [PMID: 23805751 PMCID: PMC3703878 DOI: 10.1039/c2fd20095c] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/18/2023]
Abstract
Membranes with a high content of polyunsaturated phosphatidylethanolamines (PE) facilitate formation of metarhodopsin-II (M(II)), the photointermediate of bovine rhodopsin that activates the G protein transducin. We determined whether M(II)-formation is quantitatively linked to the elastic properties of PEs. Curvature elasticity of monolayers of the polyunsaturated lipids 18 : 0-22 : 6(n - 3)PE, 18 : 0-22 : 5(n)- 6PE and the model lipid 18 : 1(n - 9)-18 : 1,(n- 9)PE were investigated in the inverse hexagonal phase. All three lipids form lipid monolayers with rather low spontaneous radii of curvature of 26-28 angstroms. In membranes, all three PEs generate high negative curvature elastic stress that shifts the equilibrium of MI(I)/M(II) photointermediates of rhodopsin towards M(II) formation.
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Affiliation(s)
- Walter E. Teague
- Laboratory of Membrane Biochemistry and Biophysics, NIAAA, NIH, Bethesda, MD 20892, USA. Fax: +1-301-594-0035; Tel: +1-301-594-3750
| | - Olivier Soubias
- Laboratory of Membrane Biochemistry and Biophysics, NIAAA, NIH, Bethesda, MD 20892, USA. Fax: +1-301-594-0035; Tel: +1-301-594-3750
| | - Horia Petrache
- Department of Physics, Indiana Univ.- Perdue Univ., Indianapolis, IN 46202, USA. Fax: +1-317-274-2392; Tel: +1-317-278-6521
| | - Nola Fuller
- Dept. Biol. Sci., Brock Univ., St. Catharines, Ont. L2S 3A1, Canada. Phone:+1-905-688-5550 ext.3388
| | - Kirk G. Hines
- Laboratory of Membrane Biochemistry and Biophysics, NIAAA, NIH, Bethesda, MD 20892, USA. Fax: +1-301-594-0035; Tel: +1-301-594-3750
| | - R. Peter Rand
- Dept. Biol. Sci., Brock Univ., St. Catharines, Ont. L2S 3A1, Canada. Phone:+1-905-688-5550 ext.3388
| | - Klaus Gawrisch
- Laboratory of Membrane Biochemistry and Biophysics, NIAAA, NIH, Bethesda, MD 20892, USA. Fax: +1-301-594-0035; Tel: +1-301-594-3750
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Gawrisch K, Yeliseev AA, Kimura T, Soubias O. Detergents for Extraction, Purification, and Reconstitution of G Protein-Coupled Membrane Receptors. Biophys J 2013. [DOI: 10.1016/j.bpj.2012.11.084] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022] Open
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Soubias O, Teague WE, Dwulit-Smith JR, Hines KG, Gawrisch K. Membrane Curvature Elastic Stress Strongly Modulates Metarhodopsin II Formation. Biophys J 2013. [DOI: 10.1016/j.bpj.2012.11.2020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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Soubias O, Teague WE, Hines KG, Gawrisch K. Cholesterol Enhances or Reduces Metarhodopsin II Formation Depending on Bilayer Thickness. Biophys J 2012. [DOI: 10.1016/j.bpj.2011.11.2379] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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Teague WE, Soubias O, Fuller NL, Rand RP, Gawrisch K. Curvature Elastic Properties of Phosphatidylethanolamines with Mono-and Polyunsaturated Hydrocarbon Chains - An NMR and X-Ray Diffraction Study. Biophys J 2012. [DOI: 10.1016/j.bpj.2011.11.2257] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2022] Open
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Soubias O, Gawrisch K. The role of the lipid matrix for structure and function of the GPCR rhodopsin. Biochim Biophys Acta 2011; 1818:234-40. [PMID: 21924236 DOI: 10.1016/j.bbamem.2011.08.034] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2011] [Revised: 08/30/2011] [Accepted: 08/30/2011] [Indexed: 01/20/2023]
Abstract
Photoactivation of rhodopsin in lipid bilayers results within milliseconds in a metarhodopsin I (MI)-metarhodopsin II (MII) equilibrium that is very sensitive to the lipid composition. It has been well established that lipid bilayers that are under negative curvature elastic stress from incorporation of lipids like phosphatidylethanolamines (PE) favor formation of MII, the rhodopsin photointermediate that is capable of activating G protein. Furthermore, formation of the MII state is favored by negatively charged lipids like phosphatidylserine and by lipids with longer hydrocarbon chains that yield bilayers with larger membrane hydrophobic thickness. Cholesterol and rhodopsin-rhodopsin interactions from crowding of rhodopsin molecules in lipid bilayers shift the MI-MII equilibrium towards MI. A variety of mechanisms seems to be responsible for the large, lipid-induced shifts between MI and MII: adjustment of the thickness of lipid bilayers to rhodopsin and adjustment of rhodopsin helicity to the thickness of bilayers, curvature elastic deformations in the lipid matrix surrounding the protein, direct interactions of PE headgroups and polyunsaturated hydrocarbon chains with rhodopsin, and direct or lipid-mediated interactions between rhodopsin molecules. This article is part of a Special Issue entitled: Membrane protein structure and function.
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Affiliation(s)
- Olivier Soubias
- Laboratory of Membrane Biochemistry and Biophysics, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, MD 20892, USA
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Soubias O, Teague WE, Hines KG, Gawrisch K. Rhodopsin - Rhodopsin Oligomerization in Model Lipid Bilayers - Functional Implications. Biophys J 2011. [DOI: 10.1016/j.bpj.2010.12.3073] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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Soubias O, Teague WE, Gawrisch K. Lipid Lateral Diffusion and Hydrocarbon Chain Order. Biophys J 2011. [DOI: 10.1016/j.bpj.2010.12.2008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
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Soubias O, Teague WE, Hines KG, Mitchell DC, Gawrisch K. Contribution of membrane elastic energy to rhodopsin function. Biophys J 2010; 99:817-24. [PMID: 20682259 DOI: 10.1016/j.bpj.2010.04.068] [Citation(s) in RCA: 95] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2009] [Revised: 04/16/2010] [Accepted: 04/23/2010] [Indexed: 11/16/2022] Open
Abstract
We considered the issue of whether shifts in the metarhodopsin I (MI)-metarhodopsin II (MII) equilibrium from lipid composition are fully explicable by differences in bilayer curvature elastic stress. A series of six lipids with known spontaneous radii of monolayer curvature and bending elastic moduli were added at increasing concentrations to the matrix lipid 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and the MI-MII equilibrium measured by flash photolysis followed by recording UV-vis spectra. The average area-per-lipid molecule and the membrane hydrophobic thickness were derived from measurements of the (2)H NMR order parameter profile of the palmitic acid chain in POPC. For the series of ethanolamines with different levels of headgroup methylation, shifts in the MI-MII equilibrium correlated with changes in membrane elastic properties as expressed by the product of spontaneous radius of monolayer curvature, bending elastic modulus, and lateral area per molecule. However, for the entire series of lipids, elastic energy explained the shifts only partially. Additional contributions correlated with the capability of the ethanolamine headgroups to engage in hydrogen bonding with the protein, independent of the state of ethanolamine methylation, with introduction of polyunsaturated sn-2 hydrocarbon chains, and with replacement of the palmitic acid sn-1 chains by oleic acid. The experiments point to the importance of interactions of rhodopsin with particular lipid species in the first layer of lipids surrounding the protein as well as to membrane elastic stress in the lipid-protein domain.
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Affiliation(s)
- Olivier Soubias
- Laboratory of Membrane Biochemistry and Biophysics, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, Maryland, USA
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Soubias O, Niu SL, Mitchell DC, Gawrisch K. Curvature and Specific Lipid-Protein Interactions Modulate Activity of Rhodopsin. Biophys J 2009. [DOI: 10.1016/j.bpj.2008.12.2837] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022] Open
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Gawrisch K, Soubias O, Mihailescu M. Insights from biophysical studies on the role of polyunsaturated fatty acids for function of G-protein coupled membrane receptors. Prostaglandins Leukot Essent Fatty Acids 2008; 79:131-4. [PMID: 19004627 PMCID: PMC3987897 DOI: 10.1016/j.plefa.2008.09.002] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The composition of the lipid matrix is critical for function of membrane proteins. Perhaps one of the best studied examples is the function of the G-protein-coupled membrane receptor (GPCR) rhodopsin which is located in membranes with high content of phospholipids with polyunsaturated docosahexaenoic acid chains (DHA, 22:6n-3). Technological advances enabled a more detailed study of structure and dynamics of DHA chains and their interaction with rhodopsin. It was established that polyunsaturated DHA differs from saturated and monounsaturated hydrocarbon chains by far more rapid structural conversions. Furthermore, DHA chains tend to have higher density near the lipid/water interface while density of saturated chains is higher in the bilayer center. The interface of rhodopsin has a small number of sites for tighter interaction with DHA. Polyunsaturated phosphatidylethanolamines accumulate preferentially near the protein. Surprisingly, the high conformational freedom of most DHA chains is not measurably reduced upon interaction with rhodopsin. While some observations point at an involvement of continuum elastic properties of membranes in modulation of rhodopsin function, there is growing evidence for a role of weakly specific DHA-rhodopsin interactions.
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Affiliation(s)
- Klaus Gawrisch
- Section of NMR, Laboratory of Membrane Biochemistry and Biophysics, NIAAA, NIH, Bethesda, MD 20892, USA.
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Abstract
The ability of photoactivated rhodopsin to achieve the enzymatically active metarhodopsin II conformation is exquisitely sensitive to bilayer hydrophobic thickness. The sensitivity of rhodopsin to the lipid matrix has been explained by the hydrophobic matching theory, which predicts that lipid bilayers adjust elastically to the hydrophobic length of transmembrane helices. Here, we examined if bilayer thickness adjusts to the length of the protein or if the protein alters its conformation to adapt to the bilayer. Purified bovine rhodopsin was reconstituted into a series of mono-unsaturated phosphatidylcholines with 14-20 carbons per hydrocarbon chain. Changes of hydrocarbon chain length were measured by (2)H NMR, and protein helical content was quantified by synchrotron radiation circular dichroism and conventional circular dichroism. Experiments were conducted on dark-adapted rhodopsin, the photo-intermediates metarhodopsin I/II/III, and opsin. Changes of bilayer thickness upon rhodopsin incorporation and photoactivation were mostly absent. In contrast, the helical content of rhodopsin increased with membrane hydrophobic thickness. Helical content did not change measurably upon photoactivation. The increases of bilayer thickness and helicity of rhodopsin are accompanied by higher metarhodopsin II/metarhodopsin I ratios, faster rates of metarhodopsin II formation, an increase of tryptophan fluorescence, and higher temperatures of rhodopsin denaturation. The data suggest a surprising adaptability of this G protein-coupled membrane receptor to properties of the lipid matrix.
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Affiliation(s)
- Olivier Soubias
- Laboratory of Membrane Biochemistry and Biophysics, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, Maryland 20892, USA
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Grossfield A, Pitman MC, Feller SE, Soubias O, Gawrisch K. Internal hydration increases during activation of the G-protein-coupled receptor rhodopsin. J Mol Biol 2008; 381:478-86. [PMID: 18585736 DOI: 10.1016/j.jmb.2008.05.036] [Citation(s) in RCA: 112] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2007] [Revised: 05/14/2008] [Accepted: 05/16/2008] [Indexed: 11/27/2022]
Abstract
Rhodopsin, the membrane protein responsible for dim-light vision, until recently was the only G-protein-coupled receptor (GPCR) with a known crystal structure. As a result, there is enormous interest in studying its structure, dynamics, and function. Here we report the results of three all-atom molecular dynamics simulations, each at least 1.5 micros, which predict that substantial changes in internal hydration play a functional role in rhodopsin activation. We confirm with (1)H magic angle spinning NMR that the increased hydration is specific to the metarhodopsin-I intermediate. The internal water molecules interact with several conserved residues, suggesting that changes in internal hydration may be important during the activation of other GPCRs. The results serve to illustrate the synergism of long-time-scale molecular dynamics simulations and NMR in enhancing our understanding of GPCR function.
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Affiliation(s)
- Alan Grossfield
- IBM TJ Watson Research Center, 1101 Kitchawan Road, PO Box 218, Yorktown Heights, NY 10598, USA
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Abstract
This review summarizes results of our recent solid-state NMR investigations on polyunsaturated 18:0-22:6n3-PC/PE/PS and 18:0-22:5n6-PC bilayers. Data on structure and dynamics of the polyunsaturated docosahexaenoyl (DHAn3, 22:6n3) and docosapentaenoyl chains (DPAn6, 22:5n6), investigated at physiological conditions, are reported. Lipid-protein interaction was studied on reconstituted bilayers containing the G-protein coupled membrane receptor (GPCR) rhodopsin as well as on rod outer segment (ROS) disk membranes prepared from bovine retinas. Results reveal surprisingly rapid conformational transitions of polyunsaturated chains and existence of weakly specific interactions of DHAn3 with spatially distinct sites on rhodopsin.
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Affiliation(s)
- Klaus Gawrisch
- Section of NMR, Laboratory of Membrane Biochemistry and Biophysics, NIAAA, NIH, Bethesda, MD 20892, United States.
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Affiliation(s)
- Olivier Soubias
- Laboratory of Membrane Biochemistry and Biophysics, NIAAA, National Institutes of Health, Bethesda, Maryland 20892, USA
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Abstract
31P-and 2H-nuclear magnetic resonance are widely used to study order and dynamics, but also orientation of lipid bilayers at solid interfaces. Herein, the various techniques of orienting lipid bilayers at interfaces, the requirements for acquisition of nuclear magnetic resonance spectra, and the basic principles for spectra interpretation are described. Preparation of two types of oriented bilayers is presented: multilamellar bilayers oriented at flat solid interfaces and unilamellar tubular bilayers inside porous substrates. The latter bilayers are accessible from a bulk water phase, which permits adjustment of pH, as well as delivery of proteins and ligands to the bilayer surface.
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Affiliation(s)
- Olivier Soubias
- Laboratory of Membrane Biochemistry and Biophysics, NIAA, National Institutes of Health, Bethesda, MD, USA
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Soubias O, Polozov IV, Teague WE, Yeliseev AA, Gawrisch K. Functional Reconstitution of Rhodopsin into Tubular Lipid Bilayers Supported by Nanoporous Media. Biochemistry 2006; 45:15583-90. [PMID: 17176079 DOI: 10.1021/bi061416d] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We report on a novel reconstitution method for G-protein-coupled receptors (GPCRs) that yields detergent-free, single, tubular membranes in porous anodic aluminum oxide (AAO) filters at concentrations sufficient for structural studies by solid-state NMR. The tubular membranes line the inner surface of pores that traverse the filters, permitting easy removal of detergents during sample preparation as well as delivery of ligands for functional studies. Reconstitution of bovine rhodopsin into AAO filters did not interfere with rhodopsin function. Photoactivation of rhodopsin in AAO pores, monitored by UV-vis spectrophotometry, was indistinguishable from rhodopsin in unsupported unilamellar liposomes. The rhodopsin in AAO pores is G-protein binding competent as shown by a [35S]GTPgammaS binding assay. The lipid-rhodopsin interaction was investigated by 2H NMR on sn-1- or sn-2-chain perdeuterated 1-stearoyl-2-docosahexaenoyl-sn-glycero-3-phospholine as a matrix lipid. Rhodopsin incorporation increased mosaic spread of bilayer orientations and contributed to spectral density of motions with correlation times in the range of nano- to microseconds, detected as a significant reduction in spin-spin relaxation times. The change in lipid chain order parameters due to interaction with rhodopsin was insignificant.
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Affiliation(s)
- Olivier Soubias
- Laboratory of Membrane Biochemistry and Biophysics, NIAAA, National Institutes of Health, Bethesda, Maryland 20892, USA
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Abstract
The interaction of bovine rhodopsin with poly- and monounsaturated lipids was studied by (1)H MAS NMR with magnetization transfer from rhodopsin to lipid. Experiments were conducted on bovine rod outer segment (ROS) disks and on recombinant membranes containing lipids with polyunsaturated, docosahexaenoyl (DHA) chains. Poly- and monounsaturated lipids interact specifically with different sites on the rhodopsin surface. Rates of magnetization transfer from protein to DHA are lipid headgroup-dependent and increased in the sequence PC < PS < PE. Boundary lipids are in fast exchange with the lipid matrix on a time scale of milliseconds or shorter. All rhodopsin photointermediates transferred magnetization preferentially to DHA-containing lipids, but highest rates were observed for Meta-III rhodopsin. The experiments show clearly that the surface of rhodopsin has sites for specific interaction with lipids. Current theories of lipid-protein interaction do not account for such surface heterogeneity.
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Affiliation(s)
- Olivier Soubias
- Laboratory of Membrane Biochemistry and Biophysics, NIAAA, National Institutes of Health, Bethesda, Maryland 20892, USA
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Soubias O, Jolibois F, Réat V, Milon A. Understanding sterol-membrane interactions, part II: complete 1H and 13C assignments by solid-state NMR spectroscopy and determination of the hydrogen-bonding partners of cholesterol in a lipid bilayer. Chemistry 2006; 10:6005-14. [PMID: 15497136 DOI: 10.1002/chem.200400246] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The complete assignment of cholesterol 1H and 13C NMR resonances in a lipid bilayer environment (Lalpha-dimyristoylphosphatidylcholine/cholesterol 2:1) has been obtained by a combination of 1D and 2D MAS NMR experiments: 13C spectral editing, ge-HSQC, dipolar HETCOR and J-based HETCOR. Specific chemical shift variations have been observed for the C1-C6 atoms of cholesterol measured in CCl4 solution and in the membrane. Based on previous work (F. Jolibois, O. Soubias, V. Reat, A. Milon, Chem. Eur. J. 2004, 10, preceding paper in this issue: DOI: 10.1002/chem.200400245) these variations were attributed to local changes around the cholesterol hydroxy group, such as the three major rotameric states of the C3-O3 bond and different hydrogen bonding partners (water molecules, carboxy and phosphodiester groups of phosphatidylcholine). Comparison of the experimental and theoretical chemical shifts obtained from quantum-chemistry calculations of various transient molecular complexes has allowed the distributions of hydrogen bonding partners and hydroxy rotameric states to be determined. This is the first time that the probability of hydrogen bonding occurring between cholesterol's hydroxy group and phosphatidylcholine's phosphodiester has been determined experimentally.
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Affiliation(s)
- Olivier Soubias
- Institut de Pharmacologie et de Biologie Structurale, CNRS and University P. Sabatier, 205 rte de Narbonne, Toulouse, France
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Abstract
Human peripheral-type cannabinoid receptor (CB2) was expressed in Escherichia coli as a fusion with the maltose-binding protein, thioredoxin, and a deca-histidine tag. Functional activity and structural integrity of the receptor in bacterial protoplast membranes was confirmed by extensive binding studies with a variety of natural and synthetic cannabinoid ligands. E. coli membranes expressing CB2 also activated cognate G-proteins in an in vitro coupled assay. Detergent-solubilized receptor was purified to 80%-90% homogeneity by affinity chromatography followed by ion-exchange chromatography. By high-resolution NMR on the receptor in DPC micelles, it was determined that purified CB2 forms 1:1 complexes with the ligands CP-55,940 and anandamide. The receptor was successfully reconstituted into phosphatidylcholine bilayers and the membranes were deposited into a porous substrate as tubular lipid bilayers for structural studies by NMR and scattering techniques.
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Affiliation(s)
- Alexei A Yeliseev
- Laboratory of Membrane Biochemistry and Biophysics, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, MD 20892, USA.
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Abstract
We studied the interaction of mono- and polyunsaturated phosphatidylcholines with rhodopsin by 1H NMR saturation transfer difference spectroscopy with magic angle spinning (STD-MAS NMR). The results indicate a strong preference for interaction of rhodopsin with the polyunsaturated docosahexaenoic acid.
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Affiliation(s)
- Olivier Soubias
- Laboratory of Membrane Biochemistry and Biophysics, NIAAA, National Institutes of Health, Bethesda, Maryland 20892, USA
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Ravault S, Soubias O, Saurel O, Thomas A, Brasseur R, Milon A. Fusogenic Alzheimer's peptide fragment Abeta (29-42) in interaction with lipid bilayers: secondary structure, dynamics, and specific interaction with phosphatidyl ethanolamine polar heads as revealed by solid-state NMR. Protein Sci 2005; 14:1181-9. [PMID: 15840826 PMCID: PMC2253267 DOI: 10.1110/ps.041291405] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
The interaction of the native Alzheimer's peptide C-terminal fragment Abeta (29-42), and two mutants (G33A and G37A) with neutral lipid bilayers made of POPC and POPE in a 9:1 molar ratio was investigated by solid-state NMR. This fragment and the lipid composition were selected because they represent the minimum requirement for the fusogenic activity of the Alzheimer's peptide. The chemical shifts of alanine methyl isotropic carbon were determined by MAS NMR, and they clearly demonstrated that the major form of the peptide equilibrated in membrane is not in a helical conformation. (2)H NMR, performed with acyl chain deuterated POPC, demonstrated that there is no perturbation of the acyl chain's dynamics and of the lipid phase transition temperature. (2)H NMR, performed with alanine methyl-deuterated peptide demonstrated that the peptide itself has a limited mobility below and above the lipid phase transition temperature (molecular order parameter equal to 0.94). MAS (31)P NMR revealed a specific interaction with POPE polar head as seen by the enhancement of POPE phosphorus nuclei T(2) relaxation. All these results are in favor of a beta-sheet oligomeric association of the peptide at the bilayer interface, preferentially recruiting phosphatidyl ethanolamine polar heads.
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Soubias O, Jolibois F, Massou S, Milon A, Réat V. Determination of the orientation and dynamics of ergosterol in model membranes using uniform 13C labeling and dynamically averaged 13C chemical shift anisotropies as experimental restraints. Biophys J 2005; 89:1120-31. [PMID: 15923221 PMCID: PMC1366597 DOI: 10.1529/biophysj.105.059857] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
A new strategy was established to determine the average orientation and dynamics of ergosterol in dimyristoylphosphatidylcholine model membranes. It is based on the analysis of chemical shift anisotropies (CSAs) averaged by the molecular dynamics. Static (13)C CSA tensors were computed by quantum chemistry, using the gauge-including atomic-orbital approach within Hartree-Fock theory. Uniformly (13)C-labeled ergosterol was purified from Pichia pastoris cells grown on labeled methanol. After reconstitution into dimyristoylphosphatidylcholine lipids, the complete (1)H and (13)C assignment of ergosterol's resonances was performed using a combination of magic-angle spinning two-dimensional experiments. Dynamically averaged CSAs were determined by standard side-band intensity analysis for isolated (13)C resonances (C(3) and ethylenic carbons) and by off-magic-angle spinning experiments for other carbons. A set of 18 constraints was thus obtained, from which the sterol's molecular order parameter and average orientation could be precisely defined. The validity of using computed CSAs in this strategy was verified on cholesterol model systems. This new method allowed us to quantify ergosterol's dynamics at three molar ratios: 16 mol % (Ld phase), 30 mol % (Lo phase), and 23 mol % (mixed phases). Contrary to cholesterol, ergosterol's molecular diffusion axis makes an important angle (14 degrees) with the inertial axis of the rigid four-ring system.
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Affiliation(s)
- O Soubias
- Institut de Pharmacologie et de Biologie Structurale, UMR 5089, Toulouse, France.
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Jolibois F, Soubias O, Réat V, Milon A. Understanding Sterol-Membrane Interactions Part I: Hartree-Fock versus DFT Calculations of13C and1H NMR Isotropic Chemical Shifts of Sterols in Solution and Analysis of Hydrogen-Bonding Effects. Chemistry 2004; 10:5996-6004. [PMID: 15497135 DOI: 10.1002/chem.200400245] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
1H and 13C NMR chemical shifts are exquisitely sensitive probes of the local environment of the corresponding nuclei. Ultimately, direct determination of the chemical shifts of sterols in their membrane environment has the potential to reveal their molecular interactions and dynamics, in particular concerning the hydrogen-bonding partners of their OH groups. However, this strategy requires an accurate and efficient means to quantify the influence of the various interactions on chemical shielding. Herein the validity of Hartree-Fock and DFT calculations of the 13C and 1H NMR chemical shifts of cholesterol and ergosterol are compared with one another and with experimental chemical shifts measured in solution at 500 MHz. A computational strategy (definition of basis set, simpler molecular models for the sterols themselves and their molecular complexes) is proposed and compared with experimental data in solution. It is shown in particular that the effects of hydrogen bonding with various functional groups (water as a hydrogen-bond donor and acceptor, acetone) on NMR chemical shifts in CDCl3 solution can be accurately reproduced with this computational approach.
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Affiliation(s)
- Franck Jolibois
- Laboratoire de Physique Quantique, UMR 5626, IRSAMC, University P. Sabatier, 118 rte de Narbonne, Toulouse, France
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