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Khan RH, Ahammad T, Sahu ID, Rotich NC, Daufel A, Lorigan GA. Determining the helical tilt angle and dynamic properties of the transmembrane domains of pinholin S 2168 using mechanical alignment EPR spectroscopy. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2023; 1865:184154. [PMID: 37023970 DOI: 10.1016/j.bbamem.2023.184154] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/19/2022] [Revised: 03/16/2023] [Accepted: 03/22/2023] [Indexed: 04/08/2023]
Abstract
The lytic cycle of bacteriophage φ21 for the infected E. coli is initiated by pinholin S21, which determines the timing of host cell lysis through the function of pinholin (S2168) and antipinholin (S2171). The activity of pinholin or antipinholin directly depends on the function of two transmembrane domains (TMDs) within the membrane. For active pinholin, TMD1 externalizes and lies on the surface while TMD2 remains incorporated inside the membrane forming the lining of the small pinhole. In this study, spin labeled pinholin TMDs were incorporated separately into mechanically aligned POPC (1-palmitoyl-2-oleoyl-glycero-3-phosphocholine) lipid bilayers and investigated with electron paramagnetic resonance (EPR) spectroscopy to determine the topology of both TMD1 and TMD2 with respect to the lipid bilayer; the TOAC (2,2,6,6-tetramethyl-N-oxyl-4-amino-4-carboxylic acid) spin label was used here because it attaches to the backbone of a peptide and is very rigid. TMD2 was found to be nearly colinear with the bilayer normal (n) with a helical tilt angle of 16 ± 4° while TMD1 lies on or near the surface with a helical tilt angle of 84 ± 4°. The order parameters (~0.6 for both TMDs) obtained from our alignment study were reasonable, which indicates the samples incorporated inside the membrane were well aligned with respect to the magnetic field (B0). The data obtained from this study supports previous findings on pinholin: TMD1 partially externalizes from the lipid bilayer and interacts with the membrane surface, whereas TMD2 remains buried in the lipid bilayer in the active conformation of pinholin S2168. In this study, the helical tilt angle of TMD1 was measured for the first time. For TMD2 our experimental data corroborates the findings of the previously reported helical tilt angle by the Ulrich group.
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Affiliation(s)
- Rasal H Khan
- Department of Chemistry and Biochemistry, Miami University, Oxford, OH 45056, USA
| | - Tanbir Ahammad
- Department of Chemistry and Biochemistry, Miami University, Oxford, OH 45056, USA
| | - Indra D Sahu
- Department of Chemistry and Biochemistry, Miami University, Oxford, OH 45056, USA; Natural Science Division, Campbellsville University, Campbellsville, KY 42718, USA
| | - Nancy C Rotich
- Department of Chemistry and Biochemistry, Miami University, Oxford, OH 45056, USA
| | - Andrew Daufel
- Department of Chemistry and Biochemistry, Miami University, Oxford, OH 45056, USA
| | - Gary A Lorigan
- Department of Chemistry and Biochemistry, Miami University, Oxford, OH 45056, USA.
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2
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Prakash G, Paul N, Oliver GA, Werz DB, Maiti D. C-H deuteration of organic compounds and potential drug candidates. Chem Soc Rev 2022; 51:3123-3163. [PMID: 35320331 DOI: 10.1039/d0cs01496f] [Citation(s) in RCA: 38] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
C-H deuteration has been intricately developed to satisfy the urgent need for site-selectively deuterated organic frameworks. Deuteration has been primarily used to study kinetic isotope effects of reactions but recently its significance in pharmaceutical chemistry has been discovered. Deuterium labelled compounds have stolen the limelight since the inception of the first FDA-approved deuterated drug, for the treatment of chorea-associated Huntington's disease, and their pharmacological importance was realised by chemists, although surprisingly very late. Various approaches were developed to carry out site-selective deuteration. However, the most common and efficient method is hydrogen isotope exchange (HIE). This review summarises deuteration methods of various organic motifs containing C(sp2)-H and C(sp3)-H bonds utilizing C-H bond functionalisation as a key step along with a variety of catalysts, and exemplifies their biological relevance.
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Affiliation(s)
- Gaurav Prakash
- Department of Chemistry, IIT Bombay, Powai, Mumbai-400076, India.
| | - Nilanjan Paul
- Department of Chemistry, IIT Bombay, Powai, Mumbai-400076, India.
| | - Gwyndaf A Oliver
- Technische Universität Braunschweig, Institute of Organic Chemistry, Hagenring 30, 38106 Braunschweig, Germany.
| | - Daniel B Werz
- Technische Universität Braunschweig, Institute of Organic Chemistry, Hagenring 30, 38106 Braunschweig, Germany.
| | - Debabrata Maiti
- Department of Chemistry, IIT Bombay, Powai, Mumbai-400076, India.
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3
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Park SH, Siddiqi H, Castro DV, De Angelis AA, Oom AL, Stoneham CA, Lewinski MK, Clark AE, Croker BA, Carlin AF, Guatelli J, Opella SJ. Interactions of SARS-CoV-2 envelope protein with amilorides correlate with antiviral activity. PLoS Pathog 2021; 17:e1009519. [PMID: 34003853 PMCID: PMC8184013 DOI: 10.1371/journal.ppat.1009519] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2021] [Revised: 06/07/2021] [Accepted: 04/29/2021] [Indexed: 11/24/2022] Open
Abstract
SARS-CoV-2 is the novel coronavirus that is the causative agent of COVID-19, a sometimes-lethal respiratory infection responsible for a world-wide pandemic. The envelope (E) protein, one of four structural proteins encoded in the viral genome, is a 75-residue integral membrane protein whose transmembrane domain exhibits ion channel activity and whose cytoplasmic domain participates in protein-protein interactions. These activities contribute to several aspects of the viral replication-cycle, including virion assembly, budding, release, and pathogenesis. Here, we describe the structure and dynamics of full-length SARS-CoV-2 E protein in hexadecylphosphocholine micelles by NMR spectroscopy. We also characterized its interactions with four putative ion channel inhibitors. The chemical shift index and dipolar wave plots establish that E protein consists of a long transmembrane helix (residues 8–43) and a short cytoplasmic helix (residues 53–60) connected by a complex linker that exhibits some internal mobility. The conformations of the N-terminal transmembrane domain and the C-terminal cytoplasmic domain are unaffected by truncation from the intact protein. The chemical shift perturbations of E protein spectra induced by the addition of the inhibitors demonstrate that the N-terminal region (residues 6–18) is the principal binding site. The binding affinity of the inhibitors to E protein in micelles correlates with their antiviral potency in Vero E6 cells: HMA ≈ EIPA > DMA >> Amiloride, suggesting that bulky hydrophobic groups in the 5’ position of the amiloride pyrazine ring play essential roles in binding to E protein and in antiviral activity. An N15A mutation increased the production of virus-like particles, induced significant chemical shift changes from residues in the inhibitor binding site, and abolished HMA binding, suggesting that Asn15 plays a key role in maintaining the protein conformation near the binding site. These studies provide the foundation for complete structure determination of E protein and for structure-based drug discovery targeting this protein. The novel coronavirus SARS-CoV-2, the causative agent of the world-wide pandemic of COVID-19, has become one of the greatest threats to human health. While rapid progress has been made in the development of vaccines, drug discovery has lagged, partly due to the lack of atomic-resolution structures of the free and drug-bound forms of the viral proteins. The SARS-CoV-2 envelope (E) protein, with its multiple activities that contribute to viral replication, is widely regarded as a potential target for COVID-19 treatment. As structural information is essential for drug discovery, we established an efficient sample preparation system for biochemical and structural studies of intact full-length SARS-CoV-2 E protein and characterized its structure and dynamics. We also characterized the interactions of amilorides with specific E protein residues and correlated this with their antiviral activity during viral replication. The binding affinity of the amilorides to E protein correlated with their antiviral potency, suggesting that E protein is indeed the likely target of their antiviral activity. We found that residue asparagine15 plays an important role in maintaining the conformation of the amiloride binding site, providing molecular guidance for the design of inhibitors targeting E protein.
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Affiliation(s)
- Sang Ho Park
- Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, California, United States of America
| | - Haley Siddiqi
- Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, California, United States of America
| | - Daniela V. Castro
- Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, California, United States of America
| | - Anna A. De Angelis
- Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, California, United States of America
| | - Aaron L. Oom
- Department of Medicine, University of California San Diego, La Jolla, California, United States of America
| | - Charlotte A. Stoneham
- Division of Infectious Diseases and Global Public Health, Department of Medicine, University of California San Diego School of Medicine, La Jolla, California, United States of America
| | - Mary K. Lewinski
- Division of Infectious Diseases and Global Public Health, Department of Medicine, University of California San Diego School of Medicine, La Jolla, California, United States of America
| | - Alex E. Clark
- Division of Infectious Diseases and Global Public Health, Department of Medicine, University of California San Diego School of Medicine, La Jolla, California, United States of America
- Department of Cellular and Molecular Medicine, University of California San Diego, La Jolla, California, United States of America
| | - Ben A. Croker
- Department of Pediatrics, University of California San Diego, La Jolla, California, United States of America
| | - Aaron F. Carlin
- Division of Infectious Diseases and Global Public Health, Department of Medicine, University of California San Diego School of Medicine, La Jolla, California, United States of America
| | - John Guatelli
- Division of Infectious Diseases and Global Public Health, Department of Medicine, University of California San Diego School of Medicine, La Jolla, California, United States of America
| | - Stanley J. Opella
- Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, California, United States of America
- * E-mail:
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4
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Kim M, Sisco NJ, Hilton JK, Montano CM, Castro MA, Cherry BR, Levitus M, Van Horn WD. Evidence that the TRPV1 S1-S4 membrane domain contributes to thermosensing. Nat Commun 2020; 11:4169. [PMID: 32820172 PMCID: PMC7441067 DOI: 10.1038/s41467-020-18026-2] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2020] [Accepted: 07/30/2020] [Indexed: 01/14/2023] Open
Abstract
Sensing and responding to temperature is crucial in biology. The TRPV1 ion channel is a well-studied heat-sensing receptor that is also activated by vanilloid compounds, including capsaicin. Despite significant interest, the molecular underpinnings of thermosensing have remained elusive. The TRPV1 S1-S4 membrane domain couples chemical ligand binding to the pore domain during channel gating. Here we show that the S1-S4 domain also significantly contributes to thermosensing and couples to heat-activated gating. Evaluation of the isolated human TRPV1 S1-S4 domain by solution NMR, far-UV CD, and intrinsic fluorescence shows that this domain undergoes a non-denaturing temperature-dependent transition with a high thermosensitivity. Further NMR characterization of the temperature-dependent conformational changes suggests the contribution of the S1-S4 domain to thermosensing shares features with known coupling mechanisms between this domain with ligand and pH activation. Taken together, this study shows that the TRPV1 S1-S4 domain contributes to TRPV1 temperature-dependent activation.
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Affiliation(s)
- Minjoo Kim
- School of Molecular Sciences, Arizona State University, 551 E. University Drive, Tempe, AZ, 85287, USA
- The Biodesign Institute Virginia G. Piper Center for Personalized Diagnostics, Arizona State University, Tempe, AZ, 85287, USA
| | - Nicholas J Sisco
- School of Molecular Sciences, Arizona State University, 551 E. University Drive, Tempe, AZ, 85287, USA
- The Biodesign Institute Virginia G. Piper Center for Personalized Diagnostics, Arizona State University, Tempe, AZ, 85287, USA
| | - Jacob K Hilton
- School of Molecular Sciences, Arizona State University, 551 E. University Drive, Tempe, AZ, 85287, USA
- The Biodesign Institute Virginia G. Piper Center for Personalized Diagnostics, Arizona State University, Tempe, AZ, 85287, USA
| | - Camila M Montano
- The Biodesign Institute Virginia G. Piper Center for Personalized Diagnostics, Arizona State University, Tempe, AZ, 85287, USA
| | - Manuel A Castro
- School of Molecular Sciences, Arizona State University, 551 E. University Drive, Tempe, AZ, 85287, USA
| | - Brian R Cherry
- The Magnetic Resonance Research Center, Arizona State University, Tempe, AZ, 85287, USA
| | - Marcia Levitus
- School of Molecular Sciences, Arizona State University, 551 E. University Drive, Tempe, AZ, 85287, USA
- The Biodesign Institute Center for Single Molecule Biophysics, Arizona State University, Tempe, AZ, 85287, USA
| | - Wade D Van Horn
- School of Molecular Sciences, Arizona State University, 551 E. University Drive, Tempe, AZ, 85287, USA.
- The Biodesign Institute Virginia G. Piper Center for Personalized Diagnostics, Arizona State University, Tempe, AZ, 85287, USA.
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5
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Jeong D, Han S, Lim YB, Kim SH. Investigation of the Hydration State of Self-Assembled Peptide Nanostructures with Advanced Electron Paramagnetic Resonance Spectroscopy. ACS OMEGA 2019; 4:114-120. [PMID: 31459317 PMCID: PMC6648812 DOI: 10.1021/acsomega.8b02450] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/20/2018] [Accepted: 12/07/2018] [Indexed: 06/10/2023]
Abstract
Probing the intermolecular interactions and local environments of self-assembled peptide nanostructures (SPNs) is crucial for a better understanding of the underlying molecular details of self-assembling phenomena. In particular, investigation of the hydration state is important to understand the nanoscale structural and functional characteristics of SPNs. In this report, we examined the local hydration environments of SPNs in detail to understand the driving force of the discrete geometric structural self-assembling phenomena for peptide nanostructures. Advanced electron paramagnetic resonance spectroscopy was used to probe the hydrogen bond formation and geometry as well as the hydrophobicity of the local environments at various spin-labeled sites in SPNs. The experimental results supplement the sparse experimental data regarding local structures of SPNs, such as the hydrogen bonding and the hydrophobicity of the local environment, providing important information on the formation of SPNs, which have immense potential for bioactive materials.
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Affiliation(s)
- Donghyuk Jeong
- Western
Seoul Center, Korea Basic Science Institute
(KBSI), Seoul 03759, Republic of Korea
| | - Sanghun Han
- Department
of Materials Science & Engineering, Yonsei University, Seoul 03722, Republic of Korea
| | - Yong-beom Lim
- Department
of Materials Science & Engineering, Yonsei University, Seoul 03722, Republic of Korea
| | - Sun Hee Kim
- Western
Seoul Center, Korea Basic Science Institute
(KBSI), Seoul 03759, Republic of Korea
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6
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Johnson SR, Rikli HG, Schmidt JO, Evans MS. A reexamination of poneratoxin from the venom of the bullet ant Paraponera clavata. Peptides 2017; 98:51-62. [PMID: 27266841 DOI: 10.1016/j.peptides.2016.05.012] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/02/2016] [Revised: 05/29/2016] [Accepted: 05/31/2016] [Indexed: 12/19/2022]
Abstract
In 1991, Piek et al. [45] described a voltage-gated sodium channel (VGSC) modifier from "bullet ant" (Paraponera clavata) venom they called poneratoxin (PoTx). Using UV chromatography and Edman degradation they showed two "identical peptides" of 25 residues. We reinvestigated PoTx using ultra performance liquid chromatography-tandem mass spectrometry (UPLC-TMS). De novo sequencing showed the two peptides were actually structurally different peptides: the originally described PoTx and a glycyl pro-peptide (glycyl-PoTx) that lacks C-terminus amidation. We examined P. clavata venom from different geographical locations and discovered two additional PoTx analogs: an A23E substitution analog and a D22N; A23V substitutions analog. We tested PoTx and these three natural analogs on the mammalian sensory voltage-gated sodium channel, Nav1.7, using whole cell voltage-clamp. PoTx and each analog induced slowly activating currents in response to small depolarizing steps and sustained currents due to blockade of channel inactivation, similar to that described previously in skeletal muscle [19]. Glycyl-PoTx had the same potency and efficacy as PoTx. A23E PoTx, with a decrease in both C-terminal net positive charge and hydrophobicity, had an eight-fold reduction in potency compared to PoTx. In contrast, the D22N; A23V PoTx, with an increase in both C-terminal net positive charge and hydrophobicity, had a nearly five-fold increase in potency compared to PoTx. We found that changes in PoTx C-terminus caused a significant change in PoTx potency.
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Affiliation(s)
- Stephen R Johnson
- Department of Biology, University of Illinois Springfield, Springfield, IL, United States; Department of Chemistry, University of Illinois Springfield, Springfield, IL, United States; Carbon Dynamics Institute, LLC, Sherman, IL, United States.
| | - Hillary G Rikli
- Department of Biology, University of Illinois Springfield, Springfield, IL, United States; Department of Chemistry, University of Illinois Springfield, Springfield, IL, United States
| | | | - M Steven Evans
- Department of Neurology, University of Louisville, Louisville, KY, United States
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7
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Li Y, Lee MY, Loh YR, Kang C. Secondary structure and membrane topology of dengue virus NS4A protein in micelles. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2017; 1860:442-450. [PMID: 29055659 DOI: 10.1016/j.bbamem.2017.10.016] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/09/2017] [Revised: 09/28/2017] [Accepted: 10/14/2017] [Indexed: 11/18/2022]
Abstract
Dengue virus (DENV) non-structural (NS) 4A is a membrane protein essential for viral replication. The N-terminal region of NS4A contains several helices interacting with the cell membrane and the C-terminal region consists of three potential transmembrane regions. The secondary structure of the intact NS4A is not known as the previous structural studies were carried out on its fragments. In this study, we purified the full-length NS4A of DENV serotype 4 into dodecylphosphocholine (DPC) micelles. Solution NMR studies reveal that NS4A contains six helices in DPC micelles. The N-terminal three helices are amphipathic and interact with the membrane. The C-terminal three helices are embedded in micelles. Our results suggest that NS4A contains three transmembrane helices. Our studies provide for the first time structural information of the intact NS4A of DENV and will be useful for further understanding its role in viral replication.
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Affiliation(s)
- Yan Li
- Experimental Therapeutics Centre, Agency for Science, Technology and Research (A*STAR), 31 Biopolis Way, Nanos, Singapore 138669, Singapore
| | - Michelle Yueqi Lee
- Experimental Therapeutics Centre, Agency for Science, Technology and Research (A*STAR), 31 Biopolis Way, Nanos, Singapore 138669, Singapore
| | - Ying Ru Loh
- Experimental Therapeutics Centre, Agency for Science, Technology and Research (A*STAR), 31 Biopolis Way, Nanos, Singapore 138669, Singapore
| | - CongBao Kang
- Experimental Therapeutics Centre, Agency for Science, Technology and Research (A*STAR), 31 Biopolis Way, Nanos, Singapore 138669, Singapore.
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8
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Dicke A, Gopinath T, Wang Y, Veglia G. Probing Residue-Specific Water-Protein Interactions in Oriented Lipid Membranes via Solid-State NMR Spectroscopy. J Phys Chem B 2016; 120:10959-10968. [PMID: 27704861 DOI: 10.1021/acs.jpcb.6b08282] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Water plays a central role in membrane protein folding and function. It not only catalyzes lipid membrane self-assembly but also affects the structural integrity and conformational dynamics of membrane proteins. Magic angle spinning (MAS) solid-state NMR (ssNMR) is the technique of choice for measuring water accessibility of membrane proteins, providing a measure for membrane protein topology and insertion within lipid bilayers. However, the sensitivity and resolution of membrane protein samples for MAS experiments are often dictated by hydration levels, which affect the structural dynamics of membrane proteins. Oriented-sample ssNMR (OS-ssNMR) is a complementary technique to determine both structure and topology of membrane proteins in liquid crystalline bilayers. Recent advancements in OS-ssNMR involve the use of oriented bicellar phases that have improved both sensitivity and resolution. Importantly, for bicelle formation and orientation, lipid bilayers must be well organized and hydrated, resulting in the protein's topology being similar to that found in native membranes. Under these conditions, the NMR resonances become relatively narrow, enabling a better separation of 1H-15N dipolar couplings and anisotropic 15N chemical shifts with separated local field (SLF) experiments. Here, we report a residue-specific water accessibility experiment for a small membrane protein, sarcolipin (SLN), embedded in oriented lipid bicelles as probed by new water-edited SLF (WE-SLF) experiments. We show that SLN's residues belonging to the juxtamembrane region are more exposed to the water-lipid interface than the corresponding membrane-embedded residues. The information that can be obtained from the WE-SLF experiments can be interpreted using a simple theoretical model based on spin-diffusion theory and offers a complete characterization of membrane proteins in realistic membrane bilayer systems.
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Affiliation(s)
- Alysha Dicke
- Department of Biochemistry, Molecular Biology, and Biophysics and ‡Department of Chemistry, University of Minnesota , Minneapolis, Minnesota 55455, United States
| | - T Gopinath
- Department of Biochemistry, Molecular Biology, and Biophysics and ‡Department of Chemistry, University of Minnesota , Minneapolis, Minnesota 55455, United States
| | - Yingjie Wang
- Department of Biochemistry, Molecular Biology, and Biophysics and ‡Department of Chemistry, University of Minnesota , Minneapolis, Minnesota 55455, United States
| | - Gianluigi Veglia
- Department of Biochemistry, Molecular Biology, and Biophysics and ‡Department of Chemistry, University of Minnesota , Minneapolis, Minnesota 55455, United States
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9
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Bugge K, Lindorff-Larsen K, Kragelund BB. Understanding single-pass transmembrane receptor signaling from a structural viewpoint-what are we missing? FEBS J 2016; 283:4424-4451. [PMID: 27350538 DOI: 10.1111/febs.13793] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2016] [Revised: 06/10/2016] [Accepted: 06/27/2016] [Indexed: 11/30/2022]
Abstract
Single-pass transmembrane receptors are involved in essential processes of both physiological and pathological nature and represent more than 1300 proteins in the human genome. Despite the high biological relevance of these receptors, the mechanisms of the signal transductions they facilitate are incompletely understood. One major obstacle is the lack of structures of the transmembrane domains that connect the extracellular ligand-binding domains to the intracellular signaling platforms. Over a period of almost 20 years since the first structure was reported, only 21 of these receptors have become represented by a transmembrane domain structure. This scarceness stands in strong contrast to the significance of these transmembrane α-helices for receptor functionality. In this review, we explore the properties and qualities of the current set of structures, as well as the methodological difficulties associated with their characterization and the challenges left to be overcome. Without an increased and focused effort to bring this class of proteins on par with the remaining membrane protein field, a serious lag in their biological understanding looms. Design of pharmaceutical agents, prediction of mutational affects in relation to disease, and deciphering of functional mechanisms require high-resolution structural information, especially when dealing with a domain carrying so much functionality in so few residues.
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Affiliation(s)
- Katrine Bugge
- Department of Biology, Structural Biology and NMR Laboratory, University of Copenhagen, Denmark
| | - Kresten Lindorff-Larsen
- Department of Biology, Structural Biology and NMR Laboratory, University of Copenhagen, Denmark
| | - Birthe B Kragelund
- Department of Biology, Structural Biology and NMR Laboratory, University of Copenhagen, Denmark
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10
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Bugge K, Papaleo E, Haxholm GW, Hopper JTS, Robinson CV, Olsen JG, Lindorff-Larsen K, Kragelund BB. A combined computational and structural model of the full-length human prolactin receptor. Nat Commun 2016; 7:11578. [PMID: 27174498 PMCID: PMC4869255 DOI: 10.1038/ncomms11578] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2015] [Accepted: 04/11/2016] [Indexed: 12/13/2022] Open
Abstract
The prolactin receptor is an archetype member of the class I cytokine receptor family, comprising receptors with fundamental functions in biology as well as key drug targets. Structurally, each of these receptors represent an intriguing diversity, providing an exceptionally challenging target for structural biology. Here, we access the molecular architecture of the monomeric human prolactin receptor by combining experimental and computational efforts. We solve the NMR structure of its transmembrane domain in micelles and collect structural data on overlapping fragments of the receptor with small-angle X-ray scattering, native mass spectrometry and NMR spectroscopy. Along with previously published data, these are integrated by molecular modelling to generate a full receptor structure. The result provides the first full view of a class I cytokine receptor, exemplifying the architecture of more than 40 different receptor chains, and reveals that the extracellular domain is merely the tip of a molecular iceberg.
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Affiliation(s)
- Katrine Bugge
- Structural Biology and NMR Laboratory, Department of Biology, University of Copenhagen, Ole Maaløes Vej 5, DK-2200 Copenhagen N, Denmark
| | - Elena Papaleo
- Structural Biology and NMR Laboratory, Department of Biology, University of Copenhagen, Ole Maaløes Vej 5, DK-2200 Copenhagen N, Denmark
| | - Gitte W. Haxholm
- Structural Biology and NMR Laboratory, Department of Biology, University of Copenhagen, Ole Maaløes Vej 5, DK-2200 Copenhagen N, Denmark
| | - Jonathan T. S. Hopper
- Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QZ, UK
| | - Carol V. Robinson
- Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QZ, UK
| | - Johan G. Olsen
- Structural Biology and NMR Laboratory, Department of Biology, University of Copenhagen, Ole Maaløes Vej 5, DK-2200 Copenhagen N, Denmark
| | - Kresten Lindorff-Larsen
- Structural Biology and NMR Laboratory, Department of Biology, University of Copenhagen, Ole Maaløes Vej 5, DK-2200 Copenhagen N, Denmark
| | - Birthe B. Kragelund
- Structural Biology and NMR Laboratory, Department of Biology, University of Copenhagen, Ole Maaløes Vej 5, DK-2200 Copenhagen N, Denmark
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11
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Li Y, Li Q, Wong YL, Liew LSY, Kang C. Membrane topology of NS2B of dengue virus revealed by NMR spectroscopy. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2015; 1848:2244-52. [DOI: 10.1016/j.bbamem.2015.06.010] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/17/2015] [Revised: 05/20/2015] [Accepted: 06/09/2015] [Indexed: 12/27/2022]
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12
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Li Q, Wong YL, Yueqi Lee M, Li Y, Kang C. Solution structure of the transmembrane domain of the mouse erythropoietin receptor in detergent micelles. Sci Rep 2015; 5:13586. [PMID: 26316120 PMCID: PMC4551963 DOI: 10.1038/srep13586] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2015] [Accepted: 07/31/2015] [Indexed: 12/19/2022] Open
Abstract
Erythropoiesis is regulated by the erythropoietin receptor (EpoR) binding to its ligand. The transmembrane domain (TMD) and the juxtamembrane (JM) regions of the EpoR are important for signal transduction across the cell membrane. We report a solution NMR study of the mouse erythropoietin receptor (mEpoR) comprising the TMD and the JM regions reconstituted in dodecylphosphocholine (DPC) micelles. The TMD and the C-terminal JM region of the mEpoR are mainly α-helical, adopting a similar structure to those of the human EpoR. Residues from S216 to T219 in mEpoR form a short helix. Relaxation study demonstrates that the TMD of the mEpoR is rigid whilst the N-terminal region preceding the TMD is flexible. Fluorescence spectroscopy and sequence analysis indicate that the C-terminal JM region is exposed to the solvent. Helix wheel result shows that there is hydrophilic patch in the TMD of the mEpoR formed by residues S231, S238 and T242, and these residues might be important for the receptor dimerization.
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Affiliation(s)
- Qingxin Li
- Institute of Chemical &Engineering Sciences, Agency for Science, Technology and Research (A*STAR), Singapore, Singapore
| | - Ying Lei Wong
- Experimental Therapeutics Centre, Agency for Science, Technology and Research (A*STAR), Singapore, 138669 Singapore
| | - Michelle Yueqi Lee
- Experimental Therapeutics Centre, Agency for Science, Technology and Research (A*STAR), Singapore, 138669 Singapore
| | - Yan Li
- Experimental Therapeutics Centre, Agency for Science, Technology and Research (A*STAR), Singapore, 138669 Singapore
| | - CongBao Kang
- Experimental Therapeutics Centre, Agency for Science, Technology and Research (A*STAR), Singapore, 138669 Singapore
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13
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Li Q, Wong YL, Huang Q, Kang C. Structural insight into the transmembrane domain and the juxtamembrane region of the erythropoietin receptor in micelles. Biophys J 2015; 107:2325-36. [PMID: 25418301 DOI: 10.1016/j.bpj.2014.10.013] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2014] [Revised: 10/13/2014] [Accepted: 10/15/2014] [Indexed: 01/06/2023] Open
Abstract
Erythropoietin receptor (EpoR) dimerization is an important step in erythrocyte formation. Its transmembrane domain (TMD) and juxtamembrane (JM) region are essential for signal transduction across the membrane. A construct compassing residues S212-P259 and containing the TMD and JM region of the human EpoR was purified and reconstituted in detergent micelles. The solution structure of the construct was determined in dodecylphosphocholine (DPC) micelles by solution NMR spectroscopy. Structural and dynamic studies demonstrated that the TMD and JM region are an ?-helix in DPC micelles, whereas residues S212-D224 at the N-terminus of the construct are not structured. The JM region is a helix that contains a hydrophobic patch formed by conserved hydrophobic residues (L253, I257, and W258). Nuclear Overhauser effect analysis, fluorescence spectroscopy, and paramagnetic relaxation enhancement experiments suggested that the JM region is exposed to the solvent. The structures of the TMD and JM region of the mouse EpoR were similar to those of the human EpoR.
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Affiliation(s)
- Qingxin Li
- Institute of Chemical & Engineering Sciences, Technology and Research (A(?)STAR), Singapore
| | - Ying Lei Wong
- Experimental Therapeutics Centre, Agency for Science, Technology and Research (A(?)STAR), Singapore
| | - Qiwei Huang
- Experimental Therapeutics Centre, Agency for Science, Technology and Research (A(?)STAR), Singapore
| | - CongBao Kang
- Experimental Therapeutics Centre, Agency for Science, Technology and Research (A(?)STAR), Singapore.
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14
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Rösner HI, Kragelund BB. Structure and dynamic properties of membrane proteins using NMR. Compr Physiol 2013; 2:1491-539. [PMID: 23798308 DOI: 10.1002/cphy.c110036] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Integral membrane proteins are one of the most challenging groups of macromolecules despite their apparent conformational simplicity. They manage and drive transport, circulate information, and participate in cellular movements via interactions with other proteins and through intricate conformational changes. Their structural and functional decoding is challenging and has imposed demanding experimental development. Solution nuclear magnetic resonance (NMR) spectroscopy is one of the techniques providing the capacity to make a significant difference in the deciphering of the membrane protein structure-function paradigm. The method has evolved dramatically during the last decade resulting in a plethora of new experiments leading to a significant increase in the scientific repertoire for studying membrane proteins. Besides solving the three-dimensional structures using state-of-the-art approaches, a large variety of developments of well-established techniques are available providing insight into membrane protein flexibility, dynamics, and interactions. Inspired by the speed of development in the application of new strategies, by invention of methods to measure solvent accessibility and describe low-populated states, this review seeks to introduce the vast possibilities solution NMR can offer to the study of membrane protein structure-function analyses with special focus on applicability.
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Affiliation(s)
- Heike I Rösner
- Structural Biology and NMR Laboratory, Department of Biology, University of Copenhagen, Copenhagen, Denmark
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15
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Thakur A, Chandra K, Dubey A, D'Silva P, Atreya HS. Rapid Characterization of Hydrogen Exchange in Proteins. Angew Chem Int Ed Engl 2013; 52:2440-3. [DOI: 10.1002/anie.201206828] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2012] [Revised: 11/03/2012] [Indexed: 11/06/2022]
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16
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Thakur A, Chandra K, Dubey A, D'Silva P, Atreya HS. Rapid Characterization of Hydrogen Exchange in Proteins. Angew Chem Int Ed Engl 2013. [DOI: 10.1002/ange.201206828] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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17
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Verardi R, Traaseth NJ, Masterson LR, Vostrikov VV, Veglia G. Isotope labeling for solution and solid-state NMR spectroscopy of membrane proteins. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2012; 992:35-62. [PMID: 23076578 PMCID: PMC3555569 DOI: 10.1007/978-94-007-4954-2_3] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
In this chapter, we summarize the isotopic labeling strategies used to obtain high-quality solution and solid-state NMR spectra of biological samples, with emphasis on integral membrane proteins (IMPs). While solution NMR is used to study IMPs under fast tumbling conditions, such as in the presence of detergent micelles or isotropic bicelles, solid-state NMR is used to study the structure and orientation of IMPs in lipid vesicles and bilayers. In spite of the tremendous progress in biomolecular NMR spectroscopy, the homogeneity and overall quality of the sample is still a substantial obstacle to overcome. Isotopic labeling is a major avenue to simplify overlapped spectra by either diluting the NMR active nuclei or allowing the resonances to be separated in multiple dimensions. In the following we will discuss isotopic labeling approaches that have been successfully used in the study of IMPs by solution and solid-state NMR spectroscopy.
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Affiliation(s)
- Raffaello Verardi
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455
| | | | | | | | - Gianluigi Veglia
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455
- Department of Chemistry, University of Minnesota, Minneapolis, MN 55455
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18
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De Simone A, Dhulesia A, Soldi G, Vendruscolo M, Hsu STD, Chiti F, Dobson CM. Experimental free energy surfaces reveal the mechanisms of maintenance of protein solubility. Proc Natl Acad Sci U S A 2011; 108:21057-62. [PMID: 22160682 PMCID: PMC3248487 DOI: 10.1073/pnas.1112197108] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The identification of the factors that enable normally folded proteins to remain in their soluble and functional states is crucial for a comprehensive understanding of any biological system. We have determined a series of energy landscapes of the acylphosphatase from Drosophila melanogaster under a variety of conditions by combining NMR measurements with restrained molecular dynamics simulations. We thus analyzed the differences in the structures, dynamics, and energy surfaces of the protein in its soluble state or in situations where it aggregates through conformational states that have native-like structure, folding stability, and enzymatic activity. The study identifies the nature of the energy barriers that under normal physiological conditions prevent the protein ensemble from populating dangerous aggregation-prone states. We found that such states, although similar to the native conformation, have altered surface charge distribution, alternative topologies of the β-sheet region, and modified solvent exposure of hydrophobic surfaces and aggregation-prone regions of the sequence. The identified barriers allow the protein to undergo functional dynamics while remaining soluble and without a significant risk of misfolding and aggregation into nonfunctional and potentially toxic species.
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Affiliation(s)
- Alfonso De Simone
- Division of Molecular Biosciences, Imperial College London, London SW7 2AZ, United Kingdom
| | - Anne Dhulesia
- Department of Chemistry, University of Cambridge, Cambridge CB2 1EW, United Kingdom
| | - Gemma Soldi
- Department of Biological Sciences, University of Florence, 50134 Florence, Italy
| | - Michele Vendruscolo
- Department of Chemistry, University of Cambridge, Cambridge CB2 1EW, United Kingdom
| | - Shang-Te Danny Hsu
- Institute of Bioinformatics and Structural Biology National Tsing Hua University, Hsinchu 30013, Taiwan
- Institute of Biological Chemistry, Academia Sinica, Taipei 115, Taiwan; and
| | - Fabrizio Chiti
- Department of Biological Sciences, University of Florence, 50134 Florence, Italy
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19
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Shi L, Traaseth NJ, Verardi R, Gustavsson M, Gao J, Veglia G. Paramagnetic-based NMR restraints lift residual dipolar coupling degeneracy in multidomain detergent-solubilized membrane proteins. J Am Chem Soc 2011; 133:2232-41. [PMID: 21287984 DOI: 10.1021/ja109080t] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Residual dipolar couplings (RDCs) are widely used as orientation-dependent NMR restraints to improve the resolution of the NMR conformational ensemble of biomacromolecules and define the relative orientation of multidomain proteins and protein complexes. However, the interpretation of RDCs is complicated by the intrinsic degeneracy of analytical solutions and protein dynamics that lead to ill-defined orientations of the structural domains (ghost orientations). Here, we illustrate how restraints from paramagnetic relaxation enhancement (PRE) experiments lift the orientational ambiguity of multidomain membrane proteins solubilized in detergent micelles. We tested this approach on monomeric phospholamban (PLN), a 52-residue membrane protein, which is composed of two helical domains connected by a flexible loop. We show that the combination of classical solution NMR restraints (NOEs and dihedral angles) with RDC and PRE constraints resolves topological ambiguities, improving the convergence of the PLN structural ensemble and giving the depth of insertion of the protein within the micelle. The combination of RDCs with PREs will be necessary for improving the accuracy and precision of membrane protein conformational ensembles, where three-dimensional structures are dictated by interactions with the membrane-mimicking environment rather than compact tertiary folds common in globular proteins.
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Affiliation(s)
- Lei Shi
- Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455, United States
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20
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Dasari M, Espargaro A, Sabate R, Lopez del Amo JM, Fink U, Grelle G, Bieschke J, Ventura S, Reif B. Bacterial Inclusion Bodies of Alzheimer's Disease β-Amyloid Peptides Can Be Employed To Study Native-Like Aggregation Intermediate States. Chembiochem 2011; 12:407-23. [DOI: 10.1002/cbic.201000602] [Citation(s) in RCA: 86] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2010] [Indexed: 01/22/2023]
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21
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Cook GA, Zhang H, Park SH, Wang Y, Opella SJ. Comparative NMR studies demonstrate profound differences between two viroporins: p7 of HCV and Vpu of HIV-1. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2010; 1808:554-60. [PMID: 20727848 DOI: 10.1016/j.bbamem.2010.08.005] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/02/2010] [Revised: 08/03/2010] [Accepted: 08/05/2010] [Indexed: 10/19/2022]
Abstract
The p7 protein from hepatitis C virus and the Vpu protein from HIV-1 are members of the viroporin family of small viral membrane proteins. It is essential to determine their structures in order to obtain an understanding of their molecular mechanisms and to develop new classes of anti-viral drugs. Because they are membrane proteins, it is challenging to study them in their native phospholipid bilayer environments by most experimental methods. Here we describe applications of NMR spectroscopy to both p7 and Vpu. Isotopically labeled p7 and Vpu samples were prepared by heterologous expression in bacteria, initial isolation as fusion proteins, and final purification by chromatography. The purified proteins were studied in the model membrane environments of micelles by solution NMR spectroscopy and in aligned phospholipid bilayers by solid-state NMR spectroscopy. The resulting structural findings enable comparisons to be made between the two proteins, demonstrating that they have quite different architectures. Most notably, Vpu has one trans-membrane helix and p7 has two trans-membrane helices; in addition, there are significant differences in the structures and dynamics of their internal loop and terminal regions.
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Affiliation(s)
- Gabriel A Cook
- Department of Chemistry and Biochemistry, University of California, San Diego, Lajolla, CA 92093, USA
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22
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Secondary structure, dynamics, and architecture of the p7 membrane protein from hepatitis C virus by NMR spectroscopy. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2010; 1808:1448-53. [PMID: 20727850 DOI: 10.1016/j.bbamem.2010.08.010] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/14/2010] [Revised: 08/06/2010] [Accepted: 08/10/2010] [Indexed: 11/24/2022]
Abstract
P7 is a small membrane protein that is essential for the infectivity of hepatitis C virus. Solution-state NMR experiments on p7 in DHPC micelles, including hydrogen/deuterium exchange, paramagnetic relaxation enhancement and bicelle 'q-titration,' demonstrate that the protein has a range of dynamic properties and distinct structural segments. These data along with residual dipolar couplings yield a secondary structure model of p7. We were able to confirm previous proposals that the protein has two transmembrane segments with a short interhelical loop containing the two basic residues K33 and R35. The 63-amino acid protein has a remarkably complex structure made up of seven identifiable sections, four of which are helical segments with different tilt angles and dynamics. A solid-state NMR two-dimensional separated local field spectrum of p7 aligned in phospholipid bilayers provided the tilt angles of two of these segments. A preliminary structural model of p7 derived from these NMR data is presented.
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23
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Kim HJ, Howell SC, Van Horn WD, Jeon YH, Sanders CR. Recent Advances in the Application of Solution NMR Spectroscopy to Multi-Span Integral Membrane Proteins. PROGRESS IN NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY 2009; 55:335-360. [PMID: 20161395 PMCID: PMC2782866 DOI: 10.1016/j.pnmrs.2009.07.002] [Citation(s) in RCA: 94] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Affiliation(s)
- Hak Jun Kim
- Korea Polar Research Institute, Korea Ocean Research and Development Institute, Incheon, 406-840, Korea
| | - Stanley C. Howell
- Department of Biochemistry, Center for Structural Biology, Vanderbilt University School of Medicine, Nashville, TN, 37232-8725, USA
| | - Wade D. Van Horn
- Department of Biochemistry, Center for Structural Biology, Vanderbilt University School of Medicine, Nashville, TN, 37232-8725, USA
| | - Young Ho Jeon
- Center for Magnetic Resonance, Korea Basic Research Institute, Daejon, 305-333, Korea
| | - Charles R. Sanders
- Department of Biochemistry, Center for Structural Biology, Vanderbilt University School of Medicine, Nashville, TN, 37232-8725, USA
- Corresponding Author: ; phone: 615-936-3756; fax: 615-936-2211
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24
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Cook GA, Opella SJ. NMR studies of p7 protein from hepatitis C virus. EUROPEAN BIOPHYSICS JOURNAL: EBJ 2009; 39:1097-104. [PMID: 19727701 PMCID: PMC2878448 DOI: 10.1007/s00249-009-0533-y] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/11/2009] [Revised: 07/22/2009] [Accepted: 08/04/2009] [Indexed: 01/10/2023]
Abstract
The p7 protein of hepatitis C virus (HCV) plays an important role in the viral lifecycle. Like other members of the viroporin family of small membrane proteins, the amino acid sequence of p7 is largely conserved over the entire range of genotypes, and it forms ion channels that can be blocked by a number of established channel-blocking compounds. Its characteristics as a membrane protein make it difficult to study by most structural techniques, since it requires the presence of lipids to fold and function properly. Purified p7 can be incorporated into phospholipid bilayers and micelles. Initial solid-state nuclear magnetic resonance (NMR) studies of p7 in 14-O-PC/6-O-PC bicelles indicate that the protein contains helical segments that are tilted approximately 10° and 25° relative to the bilayer normal. A truncated construct corresponding to the second transmembrane domain of p7 is shown to have properties similar to those of the full-length protein, and was used to determine that the helix segment tilted at 10° is in the C-terminal portion of the protein. The addition of the channel blocker amantadine to the full-length protein resulted in selective chemical shift changes, demonstrating that NMR has a potential role in the development of drugs targeted to p7.
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Affiliation(s)
- Gabriel A Cook
- Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, CA 92093, USA
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25
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Strandberg E, Tremouilhac P, Wadhwani P, Ulrich AS. Synergistic transmembrane insertion of the heterodimeric PGLa/magainin 2 complex studied by solid-state NMR. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2009; 1788:1667-79. [DOI: 10.1016/j.bbamem.2008.12.018] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/21/2008] [Revised: 11/21/2008] [Accepted: 12/11/2008] [Indexed: 11/16/2022]
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26
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Langosch D, Arkin IT. Interaction and conformational dynamics of membrane-spanning protein helices. Protein Sci 2009; 18:1343-58. [PMID: 19530249 PMCID: PMC2775205 DOI: 10.1002/pro.154] [Citation(s) in RCA: 94] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2009] [Revised: 04/19/2009] [Accepted: 04/20/2009] [Indexed: 12/23/2022]
Abstract
Within 1 or 2 decades, the reputation of membrane-spanning alpha-helices has changed dramatically. Once mostly regarded as dull membrane anchors, transmembrane domains are now recognized as major instigators of protein-protein interaction. These interactions may be of exquisite specificity in mediating assembly of stable membrane protein complexes from cognate subunits. Further, they can be reversible and regulatable by external factors to allow for dynamic changes of protein conformation in biological function. Finally, these helices are increasingly regarded as dynamic domains. These domains can move relative to each other in different functional protein conformations. In addition, small-scale backbone fluctuations may affect their function and their impact on surrounding lipid shells. Elucidating the ways by which these intricate structural features are encoded by the amino acid sequences will be a fascinating subject of research for years to come.
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Affiliation(s)
- Dieter Langosch
- Lehrstuhl Chemie der Biopolymere, Technische Universität München, Weihenstephaner Berg 3, 85354 Freising, Germany.
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27
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Poschner BC, Quint S, Hofmann MW, Langosch D. Sequence-specific conformational dynamics of model transmembrane domains determines their membrane fusogenic function. J Mol Biol 2009; 386:733-41. [PMID: 19154744 DOI: 10.1016/j.jmb.2008.12.077] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2008] [Accepted: 12/29/2008] [Indexed: 10/21/2022]
Abstract
The transmembrane domains of fusion proteins are known to be functionally important and display an overabundance of helix-destabilizing Ile and Val residues. In an effort to systematically study the relationship of fusogenicity and helix stability, we previously designed LV peptides, a low-complexity model system whose hydrophobic core consists of Leu and Val residues at different ratios. The ability of LV peptides to fuse membranes increases with the content of helix-destabilizing residues. Here, we monitored the kinetics of amide deuterium/hydrogen exchange of LV-peptide helices to probe their conformational dynamics. The kinetics indeed increases strongly with the content of helix-destabilizing residues and is likely to reflect local fluctuations of the helix backbones as all peptides exhibit uncorrelated exchange and contain subpopulations of amide deuterium atoms that exchange with different velocities. Interestingly, helices whose amide deuterium atoms are shifted from slower to faster subpopulations are more fusogenic. Novel peptide variants in which Val residues are concentrated at peripheral or central domains of the hydrophobic core were designed to map functionally relevant helix subdomains. Their structural and functional analysis suggests that dynamic domains close to the helix termini are more relevant for fusogenicity than central domains but cooperate with the latter to achieve strong fusogenicity.
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Affiliation(s)
- Bernhard C Poschner
- Lehrstuhl für Chemie der Biopolymere, Technische Universität München, Weihenstephaner Berg 3, 85354 Freising, Germany
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28
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Porcelli F, Verardi R, Shi L, Henzler-Wildman KA, Ramamoorthy A, Veglia G. NMR structure of the cathelicidin-derived human antimicrobial peptide LL-37 in dodecylphosphocholine micelles. Biochemistry 2008; 47:5565-72. [PMID: 18439024 PMCID: PMC5873590 DOI: 10.1021/bi702036s] [Citation(s) in RCA: 147] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
LL-37 is the only cathelicidin-derived polypeptide found in humans. Its eclectic function makes this peptide one of the most intriguing chemical defense agents, with crucial roles in moderating inflammation, promoting wound healing, and boosting the human immune system. LL-37 kills both prokaryotic and eukaryotic cells through physical interaction with cell membranes. In order to study its active conformation in membranes, we have reconstituted LL-37 into dodecylphosphocholine (DPC) micelles and determined its three-dimensional structure. We found that, under our experimental conditions, this peptide adopts a helix-break-helix conformation. Both the N- and C-termini are unstructured and solvent exposed. The N-terminal helical domain is more dynamic, while the C-terminal helix is more solvent protected and structured (high density of NOEs, slow H/D exchange). When it interacts with DPC, LL-37 is adsorbed on the surface of the micelle with the hydrophilic face exposed to the water phase and the hydrophobic face buried in the micelle hydrocarbon region. The break between the helices is positioned at K12 and is probably stabilized by a hydrophobic cluster formed by I13, F17, and I20 in addition to a salt bridge between K12 and E16. These results support the proposed nonpore carpet-like mechanism of action, in agreement with the solid-state NMR studies, and pave the way for understanding the function of the mature LL-37 at the atomic level.
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Affiliation(s)
| | | | | | | | - Ayyalusamy Ramamoorthy
- To whom correspondence should be addressed. G.V.: tel, (612) 625-0758; fax, (612) 625-2163, . A.R.: tel, (734) 647-6572;
| | - Gianluigi Veglia
- To whom correspondence should be addressed. G.V.: tel, (612) 625-0758; fax, (612) 625-2163, . A.R.: tel, (734) 647-6572;
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29
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Sequence-specific conformational flexibility of SNARE transmembrane helices probed by hydrogen/deuterium exchange. Biophys J 2008; 95:1326-35. [PMID: 18456822 DOI: 10.1529/biophysj.108.132928] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
SNARE proteins mediate fusion of intracellular eukaryotic membranes and their alpha-helical transmembrane domains are known to contribute to lipid bilayer mixing. Synthetic transmembrane domain peptides were previously shown to mimic the function of SNARE proteins in that they trigger liposome fusion in a sequence-specific fashion. Here, we performed a detailed investigation of the conformational dynamics of the transmembrane helices of the presynaptic SNAREs synaptobrevin II and syntaxin 1a. To this end, we recorded deuterium/hydrogen-exchange kinetics in isotropic solution as well as in the membrane-embedded state. In solution, the exchange kinetics of each peptide can be described by three different classes of amide deuteriums that exchange with different rate constants. These are likely to originate from exchange at different domains of the helices. Interestingly, the rate constants of each class vary with the TMD sequence. Thus, the exchange rate is position-specific and sequence-specific. Further, the rate constants correlate with the previously determined membrane fusogenicities. In membranes, exchange is retarded and a significant proportion of amide hydrogens are protected from exchange. We conclude that the conformational dynamics of SNARE TMD helices is mechanistically linked to their ability to drive lipid mixing.
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30
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Gradinaru R, Schowen R, Ghisla S. Solvent isotope effects in reactions of human medium-chain acyl-CoA dehydrogenase active site mutants. Biochemistry 2007; 46:2497-509. [PMID: 17286388 DOI: 10.1021/bi0614582] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Glu376, the base involved in substrate alphaH+ abstraction at the active center of medium-chain acyl-CoA dehydrogenase (MCAD), has been mutated to Gln and Gly. The mutants are active; however, their rates of dehydrogenation are lowered by approximately 5 orders of magnitude. Binding of the substrate octanoyl-CoA to Glu376Gln-MCAD involves (at least) two steps. The ensuing dehydrogenation reaction that corresponds to reduction of the flavin cofactor also occurs in two phases. These are interpreted to consist of a first, reversible step, followed by a slower, practically irreversible one. For Glu376Gln-MCAD, the log of the rates of dehydrogenation increases linearly with pH (slope = 1) in the pH range of 6-10, suggesting HO- as a reactant. The rates of the same reactions in D2O have the same pD profile and reflect a solvent kinetic isotope effect (SKIE) of approximately 8.5. Glu376Gln+Glu99Gly-MCAD (studied to assess the role of Glu99 also present at the bottom of the active center cavity) has activities and activity profiles similar to those of Glu376Gln-MCAD. This excludes Glu99 as the active center base for Glu376Gln-MCAD catalysis. Proton inventories for the two phases of the dehydrogenation reaction were investigated at 4 and 25 degrees C. The inventories at 25 degrees C reflect a SKIE of approximately 4.5; the profiles are "bowl-shaped", in which a transition-state contribution predominates. The profiles for the 4 degrees C reaction are very unusual. That for the first phase can be analyzed on a two-step model with one step (80% rate-limiting) having a conformational reorganization with an isotope effect of 90-100, from small isotope effects at many protein sites, and the other step (20% rate-limiting) having an inverse isotope effect of ca. 2, characteristic of the reaction of hydroxide ion as a base. For the second phase, only a contribution from many protein sites with a KIE of approximately 4.5 is observed. The results are compatible with a very rigid active site framework that must undergo rearrangements for dehydrogenation to take place, and specifically to allow access of HO-, the reactant that must neutralize the H+ abstracted from the alphaC-H substrate. The large isotope effects are attributed to the changes in state of several H-bonds that occur during the process.
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Affiliation(s)
- Robert Gradinaru
- Department of Biology, University of Konstanz, D-78457 Konstanz, Germany
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31
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Buffy JJ, Buck-Koehntop BA, Porcelli F, Traaseth NJ, Thomas DD, Veglia G. Defining the intramembrane binding mechanism of sarcolipin to calcium ATPase using solution NMR spectroscopy. J Mol Biol 2006; 358:420-9. [PMID: 16519897 DOI: 10.1016/j.jmb.2006.02.005] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2005] [Revised: 01/28/2006] [Accepted: 02/01/2006] [Indexed: 10/25/2022]
Abstract
Sarcolipin (SLN) is an integral membrane protein that is expressed in both skeletal and cardiac muscle, where it inhibits SERCA (calcium ATPase) by lowering its apparent Ca2+ affinity in a manner similar to that of its homologue phospholamban (PLN). We use solution NMR to map the structural changes occurring within SLN upon interaction with the regulatory target, SERCA, co-reconstituting the two proteins in dodecylphosphocholine (DPC) detergent micelles, a system that preserves the native structure of SLN and the activity of SERCA, with the goal of comparing these interactions with those of the previously studied PLN-SERCA complex. Our analysis of the structural dynamics of SLN in DPC micelles shows this polypeptide to be partitioned into four subdomains: a short unstructured N terminus (residues 1-6), a short dynamic helix (residues 7-14), a more rigid helix (residues 15-26), and an unstructured C terminus (residues 27-31). Upon addition of SERCA, the different domains behave according to their dynamics, molding onto the surface of the enzyme. Remarkably, each domain of SLN behaves in a manner similar to that of the corresponding domains in PLN, supporting the hypothesis that both SLN and PLN bind SERCA in the same groove and with similar mechanisms.
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Affiliation(s)
- Jarrod J Buffy
- Department of Chemistry, University of Minnesota, Minneapolis, MN 55455, USA
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32
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Buck-Koehntop BA, Mascioni A, Buffy JJ, Veglia G. Structure, dynamics, and membrane topology of stannin: a mediator of neuronal cell apoptosis induced by trimethyltin chloride. J Mol Biol 2005; 354:652-65. [PMID: 16246365 DOI: 10.1016/j.jmb.2005.09.038] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2005] [Revised: 09/12/2005] [Accepted: 09/13/2005] [Indexed: 10/25/2022]
Abstract
Organotin compounds or alkyltins are ubiquitous environmental toxins that have been implicated in cellular death. Unlike other xenobiotic compounds, such as organomercurials and organoleads, alkyltins activate apoptotic cascades at low concentrations. Trimethyltin (TMT) chloride is amongst the most toxic organotin compounds, and is known to selectively inflict injury to specific regions of the brain. Stannin (SNN), an 88-residue mitochondrial membrane protein, has been identified as the specific marker for neuronal cell apoptosis induced by TMT intoxication. This high specificity of TMT makes SNN an ideal model system for understanding the mechanism of organotin neurotoxicity at a molecular level. Here, we report the three-dimensional structure and dynamics of SNN in detergent micelles, and its topological orientation in lipid bilayers as determined by solution and solid-state NMR spectroscopy. We found that SNN is a monotopic membrane protein composed of three domains: a single transmembrane helix (residues 10-33) that transverses the lipid bilayer at approximately a 20 degrees angle with respect to the membrane normal; a 28 residue unstructured linker, which includes a conserved CXC metal-binding motif and a putative 14-3-3zeta binding domain; and a distorted cytoplasmic helix (residues 61-79) that is partially absorbed into the plane of the lipid bilayer with a tilt angle of approximately 80 degrees from the membrane normal. The structure and architecture of SNN within the lipid environment provides insight about how this protein transmits toxic insults caused by TMT across the membrane.
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Affiliation(s)
- Bethany A Buck-Koehntop
- Department of Chemistry, University of Minnesota, 207 Pleasant St. SE, Minneapolis, MN 55455-0431, USA
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33
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Howell SC, Mesleh MF, Opella SJ. NMR Structure Determination of a Membrane Protein with Two Transmembrane Helices in Micelles: MerF of the Bacterial Mercury Detoxification System,. Biochemistry 2005; 44:5196-206. [PMID: 15794657 DOI: 10.1021/bi048095v] [Citation(s) in RCA: 92] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The three-dimensional backbone structure of a membrane protein with two transmembrane helices in micelles was determined using solution NMR methods that rely on the measurement of backbone (1)H-(15)N residual dipolar couplings (RDCs) from samples of two different constructs that align differently in stressed polyacrylamide gels. Dipolar wave fitting to the (1)H-(15)N RDCs determines the helical boundaries based on periodicity and was utilized in the generation of supplemental dihedral restraints for the helical segments. The (1)H-(15)N RDCs and supplemental dihedral restraints enable the determination of the structure of the helix-loop-helix core domain of the mercury transport membrane protein MerF with a backbone RMSD of 0.58 A. Moreover, the fold of this polypeptide demonstrates that the two vicinal pairs of cysteine residues, shown to be involved in the transport of Hg(II) across the membrane, are exposed to the cytoplasm. This finding differs from earlier structural and mechanistic models that were based primarily on the somewhat atypical hydropathy plot for MerF and related transport proteins.
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Affiliation(s)
- Stanley C Howell
- Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California 92093-0307, USA
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34
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Metcalfe EE, Traaseth NJ, Veglia G. Serine 16 Phosphorylation Induces an Order-to-Disorder Transition in Monomeric Phospholamban†. Biochemistry 2005; 44:4386-96. [PMID: 15766268 DOI: 10.1021/bi047571e] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Phospholamban (PLB) is a 52 amino acid membrane-endogenous regulator of the sarco(endo)plasmic calcium adenosinetriphosphatase (SERCA) in cardiac muscle. PLB's phosphorylation and dephosphorylation at S16 modulate its regulatory effect on SERCA by an undetermined mechanism. In this paper, we use multidimensional (1)H/(15)N solution NMR methods to establish the structural and dynamics basis for PLB's control of SERCA upon S16 phosphorylation. For our studies, we use a monomeric, fully active mutant of PLB, where C36, C41, and C46 have been mutated to A36, F41, and A46, respectively. Our data show that phosphorylation disrupts the "L-shaped" structure of monomeric PLB, causing significant unwinding of both the cytoplasmic helix (domain Ia) and the short loop (residues 17-21) connecting this domain to the transmembrane helix (domains Ib and II). Concomitant with this conformational transition, we also find pronounced changes in both the pico- to nanosecond and the micro- to millisecond time scale dynamics. The (1)H/(15)N heteronuclear NOE values for residues 1-25 are significantly lower than those of unphosphorylated PLB, with slightly lower NOE values in the transmembrane domain, reflecting less restricted motion throughout the whole protein. These data are supported by the faster spin-lattice relaxation rates (R(1)) present in both the cytoplasmic and loop regions and by the enhanced spin-spin transverse relaxation rates (R(2)) observed in the transmembrane domain. These results demonstrate that while S16 phosphorylation induces a localized structural transition, changes in PLB's backbone dynamics are propagated throughout the protein backbone. We propose that the regulatory mechanism of PLB phosphorylation involves an order-to-disorder transition, resulting in a decrease in the PLB inhibition of SERCA.
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Affiliation(s)
- Emily E Metcalfe
- Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455, USA
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35
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Busenlehner LS, Armstrong RN. Insights into enzyme structure and dynamics elucidated by amide H/D exchange mass spectrometry. Arch Biochem Biophys 2005; 433:34-46. [PMID: 15581564 DOI: 10.1016/j.abb.2004.09.002] [Citation(s) in RCA: 156] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2004] [Revised: 09/02/2004] [Indexed: 11/25/2022]
Abstract
Conformational changes and protein dynamics play an important role in the catalytic efficiency of enzymes. Amide H/D exchange mass spectrometry (H/D exchange MS) is emerging as an efficient technique to study the local and global changes in protein structure and dynamics due to ligand binding, protein activation-inactivation by modification, and protein-protein interactions. By monitoring the selective exchange of hydrogen for deuterium along a peptide backbone, this sensitive technique probes protein motions and structural elements that may be relevant to allostery and function. In this report, several applications of H/D exchange MS are presented which demonstrate the unique capability of amide hydrogen/deuterium exchange mass spectrometry for examining dynamic and structural changes associated with enzyme catalysis.
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Affiliation(s)
- Laura S Busenlehner
- Department of Biochemistry, Center in Molecular Toxicology, Vanderbilt University School of Medicine, Nashville, TN 37232-0416, USA.
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36
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De Angelis AA, Jones DH, Grant CV, Park SH, Mesleh MF, Opella SJ. NMR experiments on aligned samples of membrane proteins. Methods Enzymol 2005; 394:350-82. [PMID: 15808228 DOI: 10.1016/s0076-6879(05)94014-7] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
NMR methods can be used to determine the structures of membrane proteins. Lipids can be chosen so that protein-containing micelles, bicelles, or bilayers are available as samples. All three types of samples can be aligned weakly or strongly, depending on their rotational correlation time. Solution NMR methods can be used with weakly aligned micelle and small bicelle samples. Solid-state NMR methods can be used with mechanically aligned bilayer and magnetically aligned bicelle samples.
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Affiliation(s)
- A A De Angelis
- Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla 92093, USA
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37
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Affiliation(s)
- Stanley J Opella
- Department of Chemistry and Biochemistry, University of California-San Diego, La Jolla, CA 92093, USA
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38
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Metcalfe EE, Zamoon J, Thomas DD, Veglia G. (1)H/(15)N heteronuclear NMR spectroscopy shows four dynamic domains for phospholamban reconstituted in dodecylphosphocholine micelles. Biophys J 2004; 87:1205-14. [PMID: 15298923 PMCID: PMC1304459 DOI: 10.1529/biophysj.103.038844] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2003] [Accepted: 05/06/2004] [Indexed: 11/18/2022] Open
Abstract
We report the backbone dynamics of monomeric phospholamban in dodecylphosphocholine micelles using (1)H/(15)N heteronuclear NMR spectroscopy. Phospholamban is a 52-amino acid membrane protein that regulates Ca-ATPase in cardiac muscle. Phospholamban comprises three structural domains: a transmembrane domain from residues 22 to 52, a connecting loop from 17 to 21, and a cytoplasmic domain from 1 to 16 that is organized in an "L"-shaped structure where the transmembrane and the cytoplasmic domain form an angle of approximately 80 degrees (Zamoon et al., 2003; Mascioni et al., 2002). T(1), T(2), and (1)H/(15)N nuclear Overhauser effect values measured for the amide backbone resonances were interpreted using the model-free approach of Lipari and Szabo. The results point to the existence of four dynamic domains, revealing the overall plasticity of the cytoplasmic helix, the flexible loop, and part of the transmembrane domain (residues 22-30). In addition, using Carr-Purcell-Meiboom-Gill-based experiments, we have characterized phospholamban dynamics in the micros-ms timescale. We found that the majority of the residues in the cytoplasmic domain, the flexible loop, and the first ten residues of the transmembrane domain undergo dynamics in the micros-ms range, whereas minimal dynamics were detected for the transmembrane domain. Hydrogen/deuterium exchange factors measured at different temperatures support the existence of slow motion in both the loop and the cytoplasmic helix. We propose that these dynamic properties are critical factors in the biomolecular recognition of phospholamban by Ca-ATPase and other interacting proteins such as protein kinase A and protein phosphatase 1.
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Affiliation(s)
- Emily E Metcalfe
- Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455, USA
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39
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Zamoon J, Mascioni A, Thomas DD, Veglia G. NMR solution structure and topological orientation of monomeric phospholamban in dodecylphosphocholine micelles. Biophys J 2004; 85:2589-98. [PMID: 14507721 PMCID: PMC1303482 DOI: 10.1016/s0006-3495(03)74681-5] [Citation(s) in RCA: 133] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Phospholamban is an integral membrane protein that regulates the contractility of cardiac muscle by maintaining cardiomyocyte calcium homeostasis. Abnormalities in association of protein kinase A with PLB have recently been linked to human heart failure, where a single mutation is responsible for dilated cardiomyopathy. To date, a high-resolution structure of phospholamban in a lipid environment has been elusive. Here, we describe the first structure of recombinant, monomeric, biologically active phospholamban in lipid-mimicking dodecylphosphocholine micelles as determined by multidimensional NMR experiments. The overall structure of phospholamban is "L-shaped" with the hydrophobic domain approximately perpendicular to the cytoplasmic portion. This is in agreement with our previously published solid-state NMR data. In addition, there are two striking discrepancies between our structure and those reported previously for synthetic phospholamban in organic solvents: a), in our structure, the orientation of the cytoplasmic helix is consistent with the amphipathic nature of these residues; and b), within the hydrophobic helix, residues are positioned on two discrete faces of the helix as consistent with their functional roles ascribed by mutagenesis. This topology renders the two phosphorylation sites, Ser-16 and Thr-17, more accessible to kinases.
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Affiliation(s)
- Jamillah Zamoon
- Department of Biochemistry, Molecular Biology, and Biophysics, and Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455, USA
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40
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Szolajska E, Poznanski J, Ferber ML, Michalik J, Gout E, Fender P, Bailly I, Dublet B, Chroboczek J. Poneratoxin, a neurotoxin from ant venom. ACTA ACUST UNITED AC 2004; 271:2127-36. [PMID: 15153103 DOI: 10.1111/j.1432-1033.2004.04128.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Poneratoxin is a small neuropeptide found in the venom of the ant Paraponera clavata. It is stored in the venom reservoir as an inactive 25-residue peptide. Here we describe both chemically synthesized poneratoxin and poneratoxin obtained by expression in insect cells. When expressed in insect cells, poneratoxin was observed attached to cell membranes. Both synthetic and recombinant ponerotoxins were soluble below pH 4.5. The structure of synthetic poneratoxin was characterized by circular dichroism and solved by nuclear magnetic resonance. In an environment imitating a lipid bilayer, at pH within the range of insect hemolymph, synthetic poneratoxin has a V shape, with two alpha-helices connected by a beta-turn. Insect larvae were paralyzed by injection of either of the purified toxins, with the recombinant one acting faster. The recombinant toxin-producing baculovirus reduced the average survival time of the insect host by 25 h compared with unmodified virus. Mass spectrometry analysis showed that the recombinant toxin has an N-terminal 21-residue extension, possibly improving its stability and/or stabilizing the membrane-bound state. The potential use of poneratoxin for the construction of biological insecticide is discussed.
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Affiliation(s)
- Ewa Szolajska
- Institute of Biochemistry and Biophysics (IBB), Polish Academy of Sciences, Warsaw, Poland
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41
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Hansen RK, Broadhurst RW, Skelton PC, Arkin IT. Hydrogen/deuterium exchange of hydrophobic peptides in model membranes by electrospray ionization mass spectrometry. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2002; 13:1376-1387. [PMID: 12484457 DOI: 10.1016/s1044-0305(02)00702-x] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
We demonstrate here that the hydrogen/deuterium solvent exchange (HDX) properties of the transmembrane fragment of the M2 protein of Influenza A (M2-TM) incorporated into lipid vesicles or detergent micelles can be studied with straightforward electrospray (ESI) and nanospray mass spectrometry (MS) configurations provided that key factors, including sample preparation techniques, are optimized. Small unilamellar vesicle preparations were obtained by solubilizing dimyristoyl phosphatidylcholine (DMPC) and the M2-TM peptide in aqueous solution with n-octyl-beta-D-glycopyranoside, followed by dialysis to remove the detergent. Electron microscopy experiments revealed that subsequent concentration by centrifugation introduced large multilamellar aggregates that were not compatible with ESI-MS. By contrast, a lyophilization-based concentration procedure, followed by thawing above the liquid crystal transition temperature of the lipid component, maintained the liposome size profile and yielded excellent ion fluxes in both ESI-MS and nano-ESI-MS. Using these methods the global HDX profile of M2-TM in aqueous DMPC vesicles was compared with that in methanol, demonstrating that several amide sites were protected from exchange by the lipid membrane. We also show that hydrophobic peptides can be detected by ESI-MS in the presence of a large molar excess of the detergent Triton X-100. The rate of HDX of M2-TM in Triton X-100 micelles was faster than that in DMPC vesicles but slower than when the peptide had been denatured in methanol. These results indicate that the accessibility of backbone amide sites to the solvent can be profoundly affected by membrane protein structure and dynamics, as well as the properties of model bilayer systems.
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Affiliation(s)
- Raino K Hansen
- Cambridge Centre for Molecular Recognition, Department of Biochemistry, University of Cambridge, Cambridge, United Kingdom
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