1
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Krüger P, Both JH, Linne U, Chirot F, Weitzel KM. Photoelectron Circular Dichroism of Electrosprayed Gramicidin Anions. J Phys Chem Lett 2022; 13:6110-6116. [PMID: 35759344 DOI: 10.1021/acs.jpclett.2c01437] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Many sophisticated approaches for analyzing properties of chiral matter have been developed in recent years. But in general, the available chiroptical methods are limited to either solvated or small gaseous molecules. Studying the chirality of large biopolymers in the gas phase, including aspects of the secondary structure, becomes accessible by combining the electrospray ionization technique with chiroptical detection protocols. Here, laser-induced photodetachment from gramicidin anions, a peptide consisting of 15 amino acids has been investigated. The angular distribution of photoelectrons is demonstrated to be sensitive to the substitution of protons by cesium ions, which is accompanied by a conformational change. The photoelectron circular dichroism (PECD) is -0.5% for bare gramicidin, whereas gramicidin with several Cs+ ions attached exhibits a PECD of +0.5%. The results are complemented and supported by ion mobility studies. The presented approach offers the prospect of studying chirality and the secondary structure of various biopolymers.
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Affiliation(s)
- Peter Krüger
- Department of Chemistry, Philipps-Universität Marburg, Hans-Meerwein-Straße, 35043 Marburg, Germany
| | - Jon Henrik Both
- Department of Chemistry, Philipps-Universität Marburg, Hans-Meerwein-Straße, 35043 Marburg, Germany
| | - Uwe Linne
- Department of Chemistry, Philipps-Universität Marburg, Hans-Meerwein-Straße, 35043 Marburg, Germany
| | - Fabien Chirot
- Institut Lumière Matière, UMR5306 Université de Lyon, Université Lyon 1, CNRS, 5 rue de la Doua, 69100 Villeurbanne, France
| | - Karl-Michael Weitzel
- Department of Chemistry, Philipps-Universität Marburg, Hans-Meerwein-Straße, 35043 Marburg, Germany
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2
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Doktorova M, Heberle FA, Marquardt D, Rusinova R, Sanford RL, Peyear TA, Katsaras J, Feigenson GW, Weinstein H, Andersen OS. Gramicidin Increases Lipid Flip-Flop in Symmetric and Asymmetric Lipid Vesicles. Biophys J 2019; 116:860-873. [PMID: 30755300 PMCID: PMC6400823 DOI: 10.1016/j.bpj.2019.01.016] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2018] [Revised: 01/03/2019] [Accepted: 01/09/2019] [Indexed: 01/06/2023] Open
Abstract
Unlike most transmembrane proteins, phospholipids can migrate from one leaflet of the membrane to the other. Because this spontaneous lipid translocation (flip-flop) tends to be very slow, cells facilitate the process with enzymes that catalyze the transmembrane movement and thereby regulate the transbilayer lipid distribution. Nonenzymatic membrane-spanning proteins with unrelated primary functions have also been found to accelerate lipid flip-flop in a nonspecific manner and by various hypothesized mechanisms. Using deuterated phospholipids, we examined the acceleration of flip-flop by gramicidin channels, which have well-defined structures and known functions, features that make them ideal candidates for probing the protein-membrane interactions underlying lipid flip-flop. To study compositionally and isotopically asymmetric proteoliposomes containing gramicidin, we expanded a recently developed protocol for the preparation and characterization of lipid-only asymmetric vesicles. Channel incorporation, conformation, and function were examined with small angle x-ray scattering, circular dichroism, and a stopped-flow spectrofluorometric assay, respectively. As a measure of lipid scrambling, we used differential scanning calorimetry to monitor the effect of gramicidin on the melting transition temperatures of the two bilayer leaflets. The two calorimetric peaks of the individual leaflets merged into a single peak over time, suggestive of scrambling, and the effect of the channel on the transbilayer lipid distribution in both symmetric 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine and asymmetric 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine/1,2-dimyristoyl-sn-glycero-3-phosphocholine vesicles was quantified from proton NMR measurements. Our results show that gramicidin increases lipid flip-flop in a complex, concentration-dependent manner. To determine the molecular mechanism of the process, we used molecular dynamics simulations and further computational analysis of the trajectories to estimate the extent of membrane deformation. Together, the experimental and computational approaches were found to constitute an effective means for studying the effects of transmembrane proteins on lipid distribution in both symmetric and asymmetric model membranes.
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Affiliation(s)
- Milka Doktorova
- Tri-Institutional PhD Program in Computational Biology and Medicine, Weill Cornell Medical College, New York, New York.
| | - Frederick A Heberle
- Department of Integrative Biology and Pharmacology, University of Texas Health Science Center, Houston, Texas; The Bredesen Center for Interdisciplinary Research and Graduate Education, University of Tennessee, Knoxville, Tennessee
| | | | - Radda Rusinova
- Department of Physiology and Biophysics, Weill Cornell Medical College, New York, New York
| | - R Lea Sanford
- Department of Physiology and Biophysics, Weill Cornell Medical College, New York, New York
| | - Thasin A Peyear
- Department of Physiology and Biophysics, Weill Cornell Medical College, New York, New York
| | - John Katsaras
- Large Scale Structures Group, Oak Ridge National Laboratory, Oak Ridge, Tennessee, Oak Ridge National Laboratory, Oak Ridge, Tennessee; Shull Wollan Center, Oak Ridge National Laboratory, Oak Ridge, Tennessee
| | - Gerald W Feigenson
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York
| | - Harel Weinstein
- Department of Physiology and Biophysics, Weill Cornell Medical College, New York, New York; The HRH Prince Alwaleed Bin Talal Bin Abdulaziz Alsaud Institute for Computational Biomedicine, Weill Greenberg Center, New York, New York
| | - Olaf S Andersen
- Department of Physiology and Biophysics, Weill Cornell Medical College, New York, New York
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3
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Reddy DN, Singh S, Ho CMW, Patel J, Schlesinger P, Rodgers S, Doctor A, Marshall GR. Design, synthesis, and biological evaluation of stable β 6.3-Helices: Discovery of non-hemolytic antibacterial peptides. Eur J Med Chem 2018; 149:193-210. [PMID: 29501941 DOI: 10.1016/j.ejmech.2018.02.057] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2017] [Revised: 01/26/2018] [Accepted: 02/16/2018] [Indexed: 11/25/2022]
Abstract
Gramicidin A, a topical antibiotic made from alternating L and D amino acids, is characterized by its wide central pore; upon insertion into membranes, it forms channels that disrupts ion gradients. We present helical peptidomimetics with this characteristic wide central pore that have been designed to mimic gramicidin A channels. Mimetics were designed using molecular modeling focused on oligomers of heterochiral dipeptides of proline analogs, in particular azaproline (AzPro). Molecular Dynamics simulations in water confirmed the stability of the designed helices. A sixteen-residue Formyl-(AzPro-Pro)8-NHCH2CH2OH helix was synthesized as well as a full thirty-two residue Cbz-(AzPro-Pro)16-OtBu channels. No liposomal lysis activity was observed suggesting lack of channel formation, possibly due to inappropriate hydrogen-bonding interactions in the membrane. These peptidomimetics also did not hemolyze red blood cells, unlike gramicidin A.
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Affiliation(s)
- Damodara N Reddy
- Department of Biochemistry & Molecular Biophysics, Washington University School of Medicine, St. Louis, MO 63110, USA.
| | - Sukrit Singh
- Department of Biochemistry & Molecular Biophysics, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Chris M W Ho
- Department of Biochemistry & Molecular Biophysics, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Janki Patel
- Department of Biochemistry & Molecular Biophysics, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Paul Schlesinger
- Department of Cell Biology & Physiology, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Stephen Rodgers
- Department of Pediatrics, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Allan Doctor
- Department of Pediatrics, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Garland R Marshall
- Department of Biochemistry & Molecular Biophysics, Washington University School of Medicine, St. Louis, MO 63110, USA.
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4
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Li J, Richards MR, Kitova EN, Klassen JS. Delivering Transmembrane Peptide Complexes to the Gas Phase Using Nanodiscs and Electrospray Ionization. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2017; 28:2054-2065. [PMID: 28681358 DOI: 10.1007/s13361-017-1735-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/18/2017] [Revised: 05/25/2017] [Accepted: 06/01/2017] [Indexed: 06/07/2023]
Abstract
The gas-phase conformations of dimers of the channel-forming membrane peptide gramicidin A (GA), produced from isobutanol or aqueous solutions of GA-containing nanodiscs (NDs), are investigated using electrospray ionization-ion mobility separation-mass spectrometry (ESI-IMS-MS) and molecular dynamics (MD) simulations. The IMS arrival times measured for (2GA + 2Na)2+ ions from isobutanol reveal three different conformations, with collision cross-sections (Ω) of 683 Å2 (conformation 1, C1), 708 Å2 (C2), and 737 Å2 (C3). The addition of NH4CH3CO2 produced (2GA + 2Na)2+ and (2GA + H + Na)2+ ions, with Ω similar to those of C1, C2, and C3, as well as (2GA + 2H)2+, (2GA + 2NH4)2+, and (2GA + H + NH4)2+ ions, which adopt a single conformation with a Ω similar to that of C2. These results suggest that the nature of the charging agents, imparted by the ESI process, can influence dimer conformation in the gas phase. Notably, the POPC NDs produced exclusively (2GA + 2NH4)2+ dimer ions; the DMPC NDs produced both (2GA + 2H)2+ and (2GA + 2NH4)2+ dimer ions. While the Ω of (2GA + 2H)2+ is similar to that of C2, the (2GA + 2NH4)2+ ions from NDs adopt a more compact structure, with a Ω of 656 Å2. It is proposed that this compact structure corresponds to the ion conducting single stranded head-to-head helical GA dimer. These findings highlight the potential of NDs, combined with ESI, for transferring transmembrane peptide complexes directly from lipid bilayers to the gas phase. Graphical Abstract ᅟ.
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Affiliation(s)
- Jun Li
- Alberta Glycomics Centre and Department of Chemistry, University of Alberta, Edmonton, T6G 2G2, Alberta, Canada
| | - Michele R Richards
- Alberta Glycomics Centre and Department of Chemistry, University of Alberta, Edmonton, T6G 2G2, Alberta, Canada
| | - Elena N Kitova
- Alberta Glycomics Centre and Department of Chemistry, University of Alberta, Edmonton, T6G 2G2, Alberta, Canada
| | - John S Klassen
- Alberta Glycomics Centre and Department of Chemistry, University of Alberta, Edmonton, T6G 2G2, Alberta, Canada.
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5
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Zhu S, Hegemann JD, Fage CD, Zimmermann M, Xie X, Linne U, Marahiel MA. Insights into the Unique Phosphorylation of the Lasso Peptide Paeninodin. J Biol Chem 2016; 291:13662-78. [PMID: 27151214 DOI: 10.1074/jbc.m116.722108] [Citation(s) in RCA: 88] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2016] [Indexed: 11/06/2022] Open
Abstract
Lasso peptides are a new class of ribosomally synthesized and post-translationally modified peptides and thus far are only isolated from proteo- and actinobacterial sources. Typically, lasso peptide biosynthetic gene clusters encode enzymes for biosynthesis and export but not for tailoring. Here, we describe the isolation of the novel lasso peptide paeninodin from the firmicute Paenibacillus dendritiformis C454 and reveal within its biosynthetic cluster a gene encoding a kinase, which we have characterized as a member of a new class of lasso peptide-tailoring kinases. By employing a wide variety of peptide substrates, it was shown that this novel type of kinase specifically phosphorylates the C-terminal serine residue while ignoring those located elsewhere. These experiments also reveal that no other recognition motif is needed for efficient enzymatic phosphorylation of the C-terminal serine. Furthermore, through comparison with homologous HPr kinases and subsequent mutational analysis, we confirmed the essential catalytic residues. Our study reveals how lasso peptides are chemically diversified and sets the foundation for rational engineering of these intriguing natural products.
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Affiliation(s)
- Shaozhou Zhu
- From the Department of Chemistry/Biochemistry, LOEWE Center for Synthetic Microbiology, Philipps-Universität Marburg, 35032 Marburg, Germany
| | - Julian D Hegemann
- From the Department of Chemistry/Biochemistry, LOEWE Center for Synthetic Microbiology, Philipps-Universität Marburg, 35032 Marburg, Germany
| | - Christopher D Fage
- From the Department of Chemistry/Biochemistry, LOEWE Center for Synthetic Microbiology, Philipps-Universität Marburg, 35032 Marburg, Germany
| | - Marcel Zimmermann
- From the Department of Chemistry/Biochemistry, LOEWE Center for Synthetic Microbiology, Philipps-Universität Marburg, 35032 Marburg, Germany
| | - Xiulan Xie
- From the Department of Chemistry/Biochemistry, LOEWE Center for Synthetic Microbiology, Philipps-Universität Marburg, 35032 Marburg, Germany
| | - Uwe Linne
- From the Department of Chemistry/Biochemistry, LOEWE Center for Synthetic Microbiology, Philipps-Universität Marburg, 35032 Marburg, Germany
| | - Mohamed A Marahiel
- From the Department of Chemistry/Biochemistry, LOEWE Center for Synthetic Microbiology, Philipps-Universität Marburg, 35032 Marburg, Germany
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6
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Sychev SV, Sukhanov SV, Telezhinskaya IN, Ovchinnikova TV. Effective lipid-detergent system for study of membrane active peptides in fluid liposomes. J Pept Sci 2016; 22:98-105. [PMID: 26751806 DOI: 10.1002/psc.2845] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2015] [Revised: 11/16/2015] [Accepted: 11/20/2015] [Indexed: 11/12/2022]
Abstract
The structure of peptide antibiotic gramicidin A (gA) was studied in phosphatidylcholin liposomes modified by nonionic detergent Triton X-100. First, the detergent : lipid ratio at which the saturation of lipid membrane by Triton X-100 occurs (Re (sat)), was determined by light scattering. Measurements of steady-state fluorescence anisotropy of 1,6-diphenyl-1,3,5-hexatriene at sublytic concentrations of detergent showed that after saturation of the membrane by Triton X-100 microviscosity of lipid bilayer is reduced by 20%. The equilibrium conformational state of gA in phosphatidylcholine liposomes at Re (sat) was studied by CD spectroscopy. It was found that the conformational state of this channel-forming peptide changed crucially when Triton X-100 induced transition to more fluid membranes. The gA single-channel measurements were made with Triton X-100 containing bilayers. Tentative assignment of the channel type and gA structures was made by correlation of CD data with conductance histograms. Lipid-detergent system with variable viscosity developed in this work can be used to study the structure and folding of other membrane-active peptides.
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Affiliation(s)
- Sergei V Sychev
- Shemyakin and Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Miklukho-Maklaya, str, Moscow, Russia
| | - Stanislav V Sukhanov
- Shemyakin and Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Miklukho-Maklaya, str, Moscow, Russia
| | - Irina N Telezhinskaya
- Shemyakin and Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Miklukho-Maklaya, str, Moscow, Russia
| | - Tatiana V Ovchinnikova
- Shemyakin and Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Miklukho-Maklaya, str, Moscow, Russia
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7
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Meikle TG, Conn CE, Separovic F, Drummond CJ. Exploring the structural relationship between encapsulated antimicrobial peptides and the bilayer membrane mimetic lipidic cubic phase: studies with gramicidin A′. RSC Adv 2016. [DOI: 10.1039/c6ra13658c] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Lipid based bicontinuous cubic mesophases provide a low-cost, robust membrane mimetic nanomaterial which allows for the incorporation of membrane peptides and proteins.
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Affiliation(s)
- Thomas G. Meikle
- School of Chemistry
- Bio21 Institute
- University of Melbourne
- Australia
- CSIRO Manufacturing Flagship
| | - Charlotte E. Conn
- School of Science
- College of Science, Engineering and Health
- RMIT University
- Melbourne
- Australia
| | | | - Calum J. Drummond
- CSIRO Manufacturing Flagship
- Clayton
- Australia
- School of Science
- College of Science, Engineering and Health
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8
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Sychev SV, Ivanov VT. Large scale conformational transitions in β
-structural motif of gramicidin A: kinetic analysis based on CD and FT-IR data. J Pept Sci 2014; 20:657-67. [DOI: 10.1002/psc.2643] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2014] [Revised: 03/21/2014] [Accepted: 03/28/2014] [Indexed: 01/28/2023]
Affiliation(s)
- Sergei V. Sychev
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences; 16/10 Miklukho-Maklaya Str. Moscow 117997 Russia
| | - Vadim T. Ivanov
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences; 16/10 Miklukho-Maklaya Str. Moscow 117997 Russia
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9
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Sychev SV, Barsukov LI, Ivanov VT. Conformation of gramicidin A in Triton X-100 micelles from CD and FTIR data: a clean example of antiparallel double β5.6 helix formation. J Pept Sci 2013; 19:452-8. [DOI: 10.1002/psc.2519] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2013] [Revised: 04/09/2013] [Accepted: 04/19/2013] [Indexed: 11/11/2022]
Affiliation(s)
- Sergei V. Sychev
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry; Russian Academy of Sciences; 16/10 Miklukho-Maklaya str. Moscow 117997 Russia
| | - Leonid I. Barsukov
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry; Russian Academy of Sciences; 16/10 Miklukho-Maklaya str. Moscow 117997 Russia
| | - Vadim T. Ivanov
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry; Russian Academy of Sciences; 16/10 Miklukho-Maklaya str. Moscow 117997 Russia
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10
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Modeling the membrane environment for membrane proteins. Biophys J 2011; 100:2073-4; author reply 2075. [PMID: 21504744 DOI: 10.1016/j.bpj.2011.02.058] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2010] [Revised: 02/01/2011] [Accepted: 02/25/2011] [Indexed: 11/24/2022] Open
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11
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Vostrikov VV, Gu H, Ingólfsson HI, Hinton JF, Andersen OS, Roux B, Koeppe RE. Gramicidin A backbone and side chain dynamics evaluated by molecular dynamics simulations and nuclear magnetic resonance experiments. II: nuclear magnetic resonance experiments. J Phys Chem B 2011; 115:7427-32. [PMID: 21574558 PMCID: PMC3114435 DOI: 10.1021/jp200906y] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Motional properties are important for understanding protein function and are accessible to NMR relaxation measurements. The goal of this study is to investigate the internal dynamics occurring in gramicidin A (gA) channels in order to provide benchmark experimental data for comparison with the results of molecular dynamics simulations. We therefore synthesized several (15)N isotope-enriched gA samples, covering all backbone residues as well as the Trp indole side chains for NMR relaxation experiments. On the basis of the (15)N NMR spectra for labeled gA samples incorporated in sodium dodecylsulfate (SDS) micelles, we determined T(1), T(2), and heteronuclear NOE values for backbone and indole (15)NH groups. The results indicate that the SDS-incorporated gA channel is a constrained structure without an especially "floppy" region. The NMR observables, particularly those for backbone groups, are predicted well by the molecular dynamics simulations in the accompanying article (DOI 10.1021/jp200904d ).
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Affiliation(s)
- Vitaly V Vostrikov
- Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, Arkansas 72701, United States
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12
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Vibrational circular-dichroism spectroscopy of homologous cyclic peptides designed to fold into β helices of opposite chirality. Biointerphases 2011; 6:1-7. [DOI: 10.1116/1.3548075] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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13
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Kumar A, Ramakrishnan V, Ranbhor R, Patel K, Durani S. Homochiral Stereochemistry: The Missing Link of Structure to Energetics in Protein Folding. J Phys Chem B 2009; 113:16435-42. [DOI: 10.1021/jp906811k] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Anil Kumar
- Department of Chemistry and School of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Mumbai 400076, India
| | - Vibin Ramakrishnan
- Department of Chemistry and School of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Mumbai 400076, India
| | - Ranjit Ranbhor
- Department of Chemistry and School of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Mumbai 400076, India
| | - Kirti Patel
- Department of Chemistry and School of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Mumbai 400076, India
| | - Susheel Durani
- Department of Chemistry and School of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Mumbai 400076, India
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14
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Lundbaek JA, Collingwood SA, Ingólfsson HI, Kapoor R, Andersen OS. Lipid bilayer regulation of membrane protein function: gramicidin channels as molecular force probes. J R Soc Interface 2009; 7:373-95. [PMID: 19940001 DOI: 10.1098/rsif.2009.0443] [Citation(s) in RCA: 231] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Membrane protein function is regulated by the host lipid bilayer composition. This regulation may depend on specific chemical interactions between proteins and individual molecules in the bilayer, as well as on non-specific interactions between proteins and the bilayer behaving as a physical entity with collective physical properties (e.g. thickness, intrinsic monolayer curvature or elastic moduli). Studies in physico-chemical model systems have demonstrated that changes in bilayer physical properties can regulate membrane protein function by altering the energetic cost of the bilayer deformation associated with a protein conformational change. This type of regulation is well characterized, and its mechanistic elucidation is an interdisciplinary field bordering on physics, chemistry and biology. Changes in lipid composition that alter bilayer physical properties (including cholesterol, polyunsaturated fatty acids, other lipid metabolites and amphiphiles) regulate a wide range of membrane proteins in a seemingly non-specific manner. The commonality of the changes in protein function suggests an underlying physical mechanism, and recent studies show that at least some of the changes are caused by altered bilayer physical properties. This advance is because of the introduction of new tools for studying lipid bilayer regulation of protein function. The present review provides an introduction to the regulation of membrane protein function by the bilayer physical properties. We further describe the use of gramicidin channels as molecular force probes for studying this mechanism, with a unique ability to discriminate between consequences of changes in monolayer curvature and bilayer elastic moduli.
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Affiliation(s)
- Jens A Lundbaek
- Department of Physiology and Biophysics, Weill Cornell Medical College, New York, NY 10065, USA.
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15
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Becucci L, Santucci A, Guidelli R. Gramicidin Conducting Dimers in Lipid Bilayers Are Stabilized by Single-File Ionic Flux along Them. J Phys Chem B 2007; 111:9814-20. [PMID: 17672492 DOI: 10.1021/jp072051p] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Gramicidin D was incorporated in a biomimetic membrane consisting of a lipid bilayer tethered to a mercury electrode via a hydrophilic spacer, and its behavior was investigated in aqueous 0.1 M KCl by potential-step chronocoulometry and electrochemical impedance spectroscopy. The impedance spectra, recorded from 0.1 to 1 x 10(5) Hz over a potential range of 0.7 V, were fitted to a series of RC meshes, which were related to the different substructural elements of the biomimetic membrane. These impedance spectra were compared with those obtained by incorporating valinomycin, under otherwise identical conditions. The potential dependence of the stationary currents reported on bilayer lipid membranes by Bamberg and Läuger (Bamberg, E.; Läuger, P. J. Membrane Biol. 1973, 11, 177-194) as well as those extracted from potential-step chronocoulometric measurements was interpreted by relating the increase in gramicidin dimerization to a progressive increase in single-file K+ flux along the dimeric channels. An analogous approach was adopted in explaining the difference between the impedance spectra obtained with gramicidin D and those obtained with valinomycin. It is concluded that gramicidin has a low tendency to form dimers in the absence of ionic flux.
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Affiliation(s)
- Lucia Becucci
- Department of Chemistry, Florence University, via della Lastruccia 3, 50019 Sesto Fiorentino (Firenze), Italy
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16
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Andersen OS, Bruno MJ, Sun H, Koeppe RE. Single-molecule methods for monitoring changes in bilayer elastic properties. Methods Mol Biol 2007; 400:543-570. [PMID: 17951759 DOI: 10.1007/978-1-59745-519-0_37] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Membrane-spanning proteins perturb the organization and dynamics of the adjacent bilayer lipids. For example, when the hydrophobic length (l) of a bilayer-spanning protein differs from the average thickness (d0) of the host bilayer, the bilayer thickness will vary locally in the vicinity of the protein in order to "match" the length of the protein's hydrophobic exterior to the thickness of the bilayer hydrophobic core. Such bilayer deformations incur an energetic cost, the bilayer deformation energy (DeltaG0def), which will vary as a function of the protein shape, the protein-bilayer hydrophobic mismatch (d0 - l), the lipid bilayer elastic properties, and the lipid intrinsic curvature (c0). Thus, if the membrane protein conformational changes underlying protein function involve the protein/bilayer interface, the ensuing changes in DeltaG0def (DeltaDeltaG0def) will contribute to the overall free-energy change of the conformational changes (DeltaG0tot)-meaning that the host lipid bilayer will modulate protein function. For a given protein, (DeltaDeltaG0def) varies as a function of the bilayer geometric properties (thickness and intrinsic curvature) and the elastic (bending and compression) moduli, which vary as a function of changes in lipid composition or with the adsorption of amphiphiles at the bilayer/solution interface. To understand how changes in bilayer properties modulate the function of bilayer-spanning proteins, single-molecule methods have been developed to probe changes in bilayer elastic properties using gramicidins as molecular force transducers. Different approaches to measuring the deformation energy are described: (1) measurements of changes in channel lifetimes and appearance rates as the lipid bilayer thickness or channel length are varied, (2) measurements of the equilibrium distribution among channels of different lengths, formed by homo- and heterodimers between gramicidin subunits of different lengths, and (3) measurements of the ratio of the appearance rates of heterodimer channels relative to parent homodimer channels formed by gramicidin subunits of different lengths.
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Affiliation(s)
- Olaf S Andersen
- Department of Physiology and Biophysics, Weill Medical College of Cornell University, New York, NY, USA
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17
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Abstract
Gramicidin channels are mini-proteins composed of two tryptophan-rich subunits. The conducting channels are formed by the transbilayer dimerization of nonconducting subunits, which are tied to the bilayer/solution interface through hydrogen bonds between the indole NH groups and the phospholipid backbone and water. The channel structure is known at atomic resolution and the channel's permeability characteristics are particularly well defined: gramicidin channels are selective for monovalent cations, with no measurable permeability to anions or polyvalent cations; ions and water move through a pore whose wall is formed by the peptide backbone; and the single-channel conductance and cation selectivity vary when the amino acid sequence is varied, even though the permeating ions make no contact with the amino acid side chains. Given the amount of experimental information that is available--for both the wild-type channels and for channels formed by amino acid-substituted gramicidin analogues--gramicidin channels provide important insights into the microphysics of ion permeation through bilayer-spanning channels. For the same reason, gramicidin channels constitute the system of choice for evaluating computational strategies for obtaining mechanistic insights into ion permeation through the complex channels formed by integral membrane proteins.
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Affiliation(s)
- Olaf S Andersen
- Weill Medical College of Cornell University, New York, NY 10021, USA.
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18
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Abstract
The biological ion channel gramicidin A (gA) was modified by synthetic means to obtain the tail-to-tail linked asymmetric gA-derived dimer compound 3. Single-channel current measurements for 3 in planar lipid bilayers exhibit an Eisenman I ion selectivity for alkali cations. The structural asymmetry does not lead to an observable functional asymmetry. The structure of 3 in solution without and with Cs cations was investigated by 1H-NMR spectroscopy. In CDCl3/CD3OH (1 : 1, v/v), 3 forms a mixture of double-stranded beta-helices. Upon addition of excess CsCl, the double-stranded species are converted completely into one new conformer: the right-handed single-stranded beta-helix. A combination of DQF-COSY and TOCSY was used for the assignment of the 1H-NMR spectrum of the Cs-3 complex in CDCl3/CD3OH (1 : 1, v/v). A total of 69 backbone, 27 long-range, and 64 side-chain distance restraints were obtained from NOESY together with 25 phi and 14 chi1 torsion angles obtained from coupling constants. These data were used as input for structure calculation with dyana built in sybyl 6.8. A final set of 11 structures with an average rmsd for the backbone of 0.45 A was obtained (PDB: 1TKQ). The structure of the Cs-3 complex in solution is equivalent to the bioactive channel conformation in the membrane environment.
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Affiliation(s)
- Xiulan Xie
- Fachbereich Chemie, Philipps-Universität Marburg, Germany
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19
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Lin TH, Huang HB, Wei HA, Shiao SH, Chen YC. The effect of temperature and lipid on the conformational transition of gramicidin A in lipid vesicles. Biopolymers 2005; 78:179-86. [PMID: 15765548 DOI: 10.1002/bip.20269] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The present study investigated the effect of temperature and lipid/peptide molar ratio on the conformational changes of the membrane peptide gramicidin A from a double-stranded helix to a single-stranded helical dimmer in 1,2-dimyristoyl-glycerol-3-phosphochloine (DMPC) vesicles. Tryptophan fluorescence spectroscopy results suggested that the conformational transition fitted a three-state (two-step) "folding" model. Rate constants, k(1) and k(2), were determined for each of the two steps. Since k(1) and k(2) increased with an increase in temperature, we hypothesized that the process corresponded to the breakage and formation of the backbone hydrogen bonds. The k(1) was from 10 to 45 folds faster than k(2), except for lipid/peptide molar ratios above 89.21, where k(2) increased rapidly. At molar ratios below 89.21, k(2) was insensitive to changes in lipid concentration. To account for this phenomenon, we proposed that while the driving interaction at high molar ratios is between the indole rings of the tryptophan residues and the lipid head groups, at low molar ratios there may be an intermolecular interaction between the tryptophan residues that causes gramicidin A to form an organized aggregated network. This aggregated network, caused by the tryptophan-tryptophan interaction, may be the main effect responsible for the slow down of the conformation change.
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Affiliation(s)
- Ta-Hsien Lin
- Department of Medical Research & Education, Veterans General Hospital-Taipei, and Institute of Biochemistry, National Yang-Ming University, Shih-Pai, Taipei 11217, Taiwan, ROC
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20
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Jagannadham MV, Nagaraj R. Conformation of gramicidin a in water: Inference from analysis of hydrogen/deuterium exchange behavior by matrix assisted laser desorption ionization mass spectrometry. Biopolymers 2005; 80:708-13. [PMID: 15887265 DOI: 10.1002/bip.20293] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Gramicidin A (the major component of gramicidin D) is a highly hydrophobic peptide with very little solubility in water. Hence, the conformation of this peptide has been extensively investigated in organic solvents and model membranes, but not in water. The peptide adopts a beta6.3-helical conformation in the monomeric and dimeric forms. We have investigated the conformation of gramicidin A in water by monitoring hydrogen-deuterium exchange by matrix-assisted laser desorption ionization-time-of-flight mass spectrometry. Our results indicate that gramicidin A is monomeric and exists in a highly folded conformation. The metal ion bound forms are clearly discernible in the monomers. The presence of the dimeric form is not observed. It is unlikely this is due to the operating conditions or the method used, as both hetero- and homodimers in gramicidin D are detected when methanol is used as a solvent. The present study also establishes that the linear gramicidins retain a history of solvent environment when ions are generated by matrix-assisted laser desorption ionization and analyzed by time-of-flight.
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Affiliation(s)
- M V Jagannadham
- Centre for Cellular and Molecular Biology,Uppal Road,Hyderabad 500 007, India.
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21
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Koert PDU. Synthetic ion channels: Functional analysis and structural studies. Phys Chem Chem Phys 2005; 7:1501-6. [DOI: 10.1039/b418561g] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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22
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Römer DU, Fenude-Schoch E, Lorenzi GP, Rüegger H. On Intrahelical Hydrogen Bonding and Stability of β-Helices: The behavior of someD,L-alternating oligoleucines with anN-methylated residue. Helv Chim Acta 2004. [DOI: 10.1002/hlca.19930760129] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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23
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Bañó MC, Salom D, Abad C. Size-exclusion high-performance liquid chromatography in the study of the autoassociating antibiotic gramicidin A in micellar milieu. JOURNAL OF BIOCHEMICAL AND BIOPHYSICAL METHODS 2003; 56:297-309. [PMID: 12834985 DOI: 10.1016/s0165-022x(03)00067-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Gramicidin A (gA) is a polypeptide antibiotic which forms dimeric channels specific for monovalent cations in biological membranes. It is a polymorphic molecule that adopts several different conformations, double-stranded (ds) helical dimers (pore conformation) and single-stranded beta-helical dimers (channel conformation). This study investigated the conformational adaptability of gramicidin A when incorporated into micelles as membrane-mimetic model system. Taking advantage of our reported, versatile, size-exclusion high-performance liquid chromatography (SE-HPLC) strategy that allows the separation of double-stranded dimers and monomers, we have quantitatively characterized the conformational transition undergone by the peptide in the micellar milieu. The importance of both hydrophobic/hydrophilic moieties of the amphipaths in the stabilization of concrete conformational species is demonstrated using detergents with different hydrocarbon chain length and/or polar head. SE-HPLC is a valuable, rapid, accurate technique for the structural characterization of hydrophobic autoassociating peptides that work in lipid environments such as biological membranes.
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Affiliation(s)
- Maria Carmen Bañó
- Departament de Bioquímica i Biologia Molecular, Universitat de València, C/ Doctor Moliner 50, E-46100 Burjassot, Valencia, Spain
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24
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Shobini J, Mishra AK, Chandra N. Conformation of gramicidin-A in CTAB micellar media. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY. B, BIOLOGY 2003; 70:117-24. [PMID: 12849702 DOI: 10.1016/s1011-1344(03)00055-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Gramicidin A (gA) is a linear pentadecapeptide, which exhibits various conformations depending on the environment. The conformational behavior of gA in spherical and rod-shaped cationic micelles formed by cetyltrimethylammonium bromide (CTAB) surfactant has been studied using circular dichroism (CD) and fluorescence spectroscopy, and a probable structure of gramicidin A in CTAB media has been proposed. A CD study shows that gramicidin A assumes beta(6.3) helical structure in cationic spherical as well as rod-shaped CTAB micellar media. Modeling studies show the flexibility of the side chain conformation particularly in tryptophan-9. Study of intrinsic fluorescence of tryptophans in gramicidin A indicates three distinct environments for the four-tryptophan residues in CTAB media.
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Affiliation(s)
- J Shobini
- Department of Chemistry, Indian Institute of Technology--Madras, Chennai 600 036, India
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25
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Zhao C, Polavarapu PL. Vibrational circular dichroism of gramicidin D in vesicles and micelles. Biopolymers 2002; 62:336-40. [PMID: 11857272 DOI: 10.1002/bip.10004] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The vibrational circular dichroism (VCD) and absorption spectra of gramicidin D in three model membranes (dioctadecyldimethylammonium chloride vesicles, dimyristoyl-phosphatidylcholine vesicles, and sodium dodecyl sulfate micelles) are presented. The absorption and VCD spectra suggest that the stable gramicidin D conformation in the model membranes is different from those in organic solvents. The presence of cations does not change the membrane-bound conformation of gramicidin D.
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Affiliation(s)
- C Zhao
- Department of Chemistry, Vanderbilt University, Nashville, Tennessee 37235, USA
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26
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Mondal S, Ghosh S. Gramicidin A and its complexes with Cs+ and Tl+ ions in organic solvents. A study by steady state and time resolved emission spectroscopy. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY. B, BIOLOGY 2001; 60:12-24. [PMID: 11386676 DOI: 10.1016/s1011-1344(00)00138-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
Gramicidin A (gr A), a linear pentadecapeptide containing four trp residues has been studied using steady state and time resolved fluorescence (at 298 K) and phosphorescence (at 77 K) in methanol (CH3OH), ethanol (C2H5OH), dimethyl sulfoxide (DMSO), 1,4-dioxane, 2-methyl tetrahydrofuran (2-MeTHF), ethanol/benzene (C2H5OH/C6H6) mixed solvent. Similar studies have also been carried out in CH3OH containing monovalent cations K+, Cs+, Tl+ and divalent cation Ca2+. Lambda(max) of fluorescence is found to be a good signature of the different forms having double helical structure [dh (1) to dh (4)] (J. Struct. Biol. 121 (1998) 123-141). Steady state and time resolved quenching studies of gr A by KI in CH3OH and DMSO and life time of the emitting singlet states of gr A support that gr A exists as a mixture of different forms of double helical (dh) structure [dh (1) to dh (4)] in CH3OH and as a random coil structure in DMSO. This study further indicates that emitting trp residue in DMSO is better shielded than that in CH3OH. Phosphorescence spectra of gr A at 77 K in CH3OH glass suggests that gr A retains a particular conformation dh (3) in this matrix. The phosphorescence spectra of gr A [conformation dh (4)] in 2-MeTHF at 77 K is further red shifted indicating that among all the dh forms, dh (4) has the emitting trp residue in most hydrophobic environment. The hydrophobicity of the emitting tryptophan environment is thus found to be in the order: dh (1)<dh (3)<dh (4). Since 2-MeTHF forms a clear glass at low temperature, it is thus possible to study the side chain arrangement of gr A dh (4) as a function of temperature. The phosphorescence spectra in different alcohol glassy matrix are in conformity with the observation of different side chain arrangement of gr A as one changes the polarity of alcohol. Steady state and time resolved quenching studies of gr A using Cs+ ion in CH3OH at 298 K clearly demonstrate the two binding sites for the metal ions and provide the value of equilibrium constant of the 'non-emitting' complex of gr A with Cs+ ion in the ground state. The observation of distinct red shift of the (0,0) band of the phosphorescence spectra of the complexes of gr A with K+, Cs+ and Tl+ ions at 77 K compared to that in CH3OH glass confirms the metal ion induced change of conformation in dh (3). The result also suggests that the emitting trp residues in the complexes are in somewhat more hydrophobic environment compared with that in the free gr A in CH3OH glass. The triplet state life time of these complexes indicate that the heavy metal ions Cs+ and Tl+ are within a Van der Waal's distance of emitting trp residue in gr A in CH3OH glass at 77 K so that they are capable of inducing increased spin-orbit coupling due to a heavy atom effect.
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Affiliation(s)
- S Mondal
- Department of Chemistry, Presidency College, Calcutta, India
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27
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Greathouse DV, Koeppe RE, Providence LL, Shobana S, Andersen OS. Design and characterization of gramicidin channels. Methods Enzymol 2001; 294:525-50. [PMID: 9916247 DOI: 10.1016/s0076-6879(99)94031-4] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
This article summarizes methods for the chemical synthesis and biophysical characterization of gramicidins with varying sequences and labels. The family of gramicidin channels has developed into a powerful model system for understanding fundamental properties, interactions, and dynamics of proteins and lipids generally, and ion channels specifically, in biological membranes.
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Affiliation(s)
- D V Greathouse
- Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville 72701, USA
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28
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Abstract
This review compares and contrasts the structures of several different types of ion channels with known three-dimensional structures, including gramicidin and the family of peptaibol channels, as well as the Streptomyces lividans potassium channel, to reveal common features in their structures that relate to their functional roles in ion binding and transport across membranes. Specifically, the locations of aromatic amino acids, the dimensions of the molecules, the multimeric nature of the channels and the roles of hydrogen bonds in stabilising such structures, the means by which the channels open and close, and the chemical nature of the groups which make up the channel lumen are discussed. The emphasis is on the commonality of features found in model channels, which may ultimately be found in other biological channel structures.
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Affiliation(s)
- B A Wallace
- Department of Crystallography, Birkbeck College, University of London, London WC1E 7HX, UK.
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29
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Bouchard M, Benjamin DR, Tito P, Robinson CV, Dobson CM. Solvent effects on the conformation of the transmembrane peptide gramicidin A: insights from electrospray ionization mass spectrometry. Biophys J 2000; 78:1010-7. [PMID: 10653814 PMCID: PMC1300704 DOI: 10.1016/s0006-3495(00)76659-8] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The binding of sodium ions to the transmembrane channel peptide gramicidin A has permitted the use of electrospray ionization mass spectrometry to study its conformation in different solvent environments. The mass spectra of the peptide in the various solvents suggest that different conformations of gramicidin A differ in their ability to bind metal ions. The data are consistent with monomeric behavior of gramicidin A in trifluoroethanol and dimethyl sulfoxide solutions, but reveal the presence of noncovalent intermolecular interactions in ethanol solution through the observation of heterodimers formed between the naturally occurring variants of the peptide. The addition of 50% v/v of water to the ethanolic solution causes changes in the circular dichroism spectrum of the peptide, suggestive of a shift in the equilibrium mixture of conformers present toward monomeric species, a result supported by its mass spectrum. The structure of gramicidin A in trifluoroethanol has also been investigated by hydrogen exchange measurements monitored by mass spectrometry. The observation of significant protection against exchange suggests that the monomeric peptide is highly structured in trifluoroethanol. The results indicate that mass spectrometry has the potential to probe the conformational behavior of neutral hydrophobic peptides in environments that mimic their functional states.
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Affiliation(s)
- M Bouchard
- Oxford Centre for Molecular Sciences, New Chemistry Laboratory, University of Oxford, Oxford OX1 3QT, United Kingdom
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30
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Zhao C, Polavarapu PL. Vibrational Circular Dichroism Is an Incisive Structural Probe: Ion-Induced Structural Changes in Gramicidin D. J Am Chem Soc 1999. [DOI: 10.1021/ja992778u] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Chunxia Zhao
- Department of Chemistry Vanderbilt University Nashville, Tennessee 37235
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31
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Jude AR, Greathouse DV, Leister MC, Koeppe RE. Steric interactions of valines 1, 5, and 7 in [valine 5, D-alanine 8] gramicidin A channels. Biophys J 1999; 77:1927-35. [PMID: 10512813 PMCID: PMC1300474 DOI: 10.1016/s0006-3495(99)77034-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
When the central valine residues 6, 7, and 8 of gramicidin A (gA) are shifted by one position, the resulting [Val(5), D-Ala(8)]gA forms right-handed channels with a single-channel conductance and average duration somewhat less than gA channels. The reduction in channel duration has been attributed to steric conflict between the side chains of Val(1) and Val(5) in opposing monomers (Koeppe, R. E. II, D. V. Greathouse, A. Jude, G. Saberwal, L. L. Providence, and O. S. Andersen. 1994. J. Biol. Chem. 269:12567-12576). To investigate the orientations and motions of valines in [Val(5), D-Ala(8)]gA, we have incorporated (2)H labels at Val 1, 5, or 7 and recorded (2)H-NMR spectra of oriented and nonoriented samples in hydrated dimyristoylphosphatidylcholine. Spectra of nonoriented samples at 4 degrees C reveal powder patterns that indicate rapid side chain "hopping" for Val(5), and an intermediate rate of hopping for Val(1) and Val(7) that is somewhat slower than in gA. Oriented samples of deuterated Val(1) and Val(7) show large changes in the methyl and C(beta)-(2)H quadrupolar splittings (Deltanu(q)) when Ala(5) in native gA is changed to Val(5). Three or more peaks for the Val(1) methyls with Deltanu(q) values that vary with the echo delay, together with an intermediate spectrum for nonoriented samples at 4 degrees C, suggest unusual side chain dynamics for Val(1) in [Val(5), D-Ala(8)]gA. These results are consistent with a steric conflict that has been introduced between the two opposing monomers. In contrast, the acylation of gA has little influence on the side chain dynamics of Val(1), regardless of the identity of residue 5.
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Affiliation(s)
- A R Jude
- Department of Chemistry & Biochemistry, University of Arkansas, Fayetteville, Arkansas 72701 USA
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32
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Separovic F, Barker S, Delahunty M, Smith R. NMR structure of C-terminally tagged gramicidin channels. BIOCHIMICA ET BIOPHYSICA ACTA 1999; 1416:48-56. [PMID: 9889316 DOI: 10.1016/s0005-2736(98)00207-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
A biotin group was covalently attached to the C terminus of gramicidin A (gA) through a linker arm comprising a glycine residue with either one (gAXB) or two caproyl groups (gAXXB). High-resolution two-dimensional NMR spectroscopy was used to determine the structure of these modified gA analogues and [Lys16]gramicidin A (gA-Lys) in sodium dodecyl-d25 sulphate micelles. Gated gA ion channels based on linking a receptor group to these gA analogues have been used recently as a component in a sensing device. The conformations of the gA backbones and amino acid side chains of lysinated gA and biotinylated gA in detergent micelles were found to be almost identical to that of native gA, i.e. that of an N-terminal to N-terminal (head to head) dimer formed by two right-handed, single-stranded beta 6.3 helices. The biotin tail of the gAXB and gAXXB and the lysine extremity of gA-Lys appeared to lie outside the micelle. Thus it appears that the covalent attachment of functional groups to the C terminus of gA does not disrupt the peptide's helical configuration. Further, single channel measurements of all three gA analogues showed that functioning ion channels were preserved within a membrane environment.
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Affiliation(s)
- F Separovic
- School of Chemistry, University of Melbourne, Parkville, VIC 3052, Australia.
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Doyle DA, Wallace BA. Shifting the equilibrium mixture of gramicidin double helices toward a single conformation with multivalent cationic salts. Biophys J 1998; 75:635-40. [PMID: 9675165 PMCID: PMC1299738 DOI: 10.1016/s0006-3495(98)77553-8] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
The conformation of the polypeptide antibiotic gramicidin is greatly influenced by its environment. In methanol, it exists as an equilibrium mixture of four interwound double-helical conformers that differ in their handedness, chain orientation, and alignment. Upon the addition of multivalent cationic salts, there is a shift in the equilibrium to a single conformer, which was monitored in this study by circular dichroism spectroscopy. With increasing concentrations of multivalent cations, both the magnitude of the entire spectrum and the ratio of the 229-nm to the 210-nm peak were increased. The spectral change is not related to the charge on the cation, but appears to be related to the cationic radius, with the maximum change in ellipticity occurring for cations with a radius of approximately 1 A. The effect requires the presence of an anion whose radius is greater than that of a fluoride ion, but is otherwise not a function of anion type. It is postulated that multivalent cations interact with a binding site in one of the conformers, known as species 1 (a left-handed, parallel, no stagger double helix), stabilizing a modified form of this type of structure.
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Affiliation(s)
- D A Doyle
- Department of Crystallography, Birkbeck College, University of London, London WC1E 7HX, England
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35
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Wallace BA. Recent Advances in the High Resolution Structures of Bacterial Channels: Gramicidin A. J Struct Biol 1998; 121:123-41. [PMID: 9618340 DOI: 10.1006/jsbi.1997.3948] [Citation(s) in RCA: 123] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Gramicidin is a polypeptide antibiotic which forms dimeric channels specific for the transport of monovalent cations across membranes. It adopts several different conformations, most notably double helical (pore) and helical dimer (channels) forms, which have very different structural and functional characteristics. This review focuses on recent high resolution structure determinations of both the pore and channel forms of the molecule by X-ray crystallographic and/or NMR spectroscopic techniques. It discusses the structural consequences of binding ions and the location of ion binding sites and how the structures are related to the conductance properties of the molecule. This relatively simple molecule is probably the best characterized ion channel (both structurally and functionally) and has, to date, been the principal proving-ground for many of our ideas about the molecular nature of ion conduction in membranes. Copyright 1998 Academic Press.
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Affiliation(s)
- BA Wallace
- Department of Crystallography, Birkbeck College, University of London, London, WC1E 7HX, United Kingdom
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36
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Abstract
Solvent effects on the far-uv CD spectra of the polypeptide gramicidin have been studied systematically in a series of alcohols of increasing chain length, ranging from methanol to dodecanol. The effects observed are of two types: primary, involving a change in the equilibrium mixture of conformers present, and secondary, involving a shift in the spectral peak positions as a function of solvent polarizability. To quantitate the primary effect, the ratio of the individual conformers present was estimated by deconvolution of the spectra into their component species. For short chain length alcohols, both parallel and antiparallel double helices are found in considerable abundance. As the solvent chain length is increased and its polarity is decreased, the left-handed antiparallel double helical species is favored. For all alcohols with chain lengths of four or more carbon atoms, the ratio of the conformers present remains relatively constant. To quantitatively examine the secondary effect, the magnitudes of the spectral shifts on the dominant conformer (species 3) have been correlated with the dielectric constants and refractive indices of the solvents, thereby indicating what underlying physical properties are responsible for these shifts. This work thus demonstrates that for gramicidin, a flexible polypeptide, the solvent effects on the CD spectra can be resolved into two types: changes due to the mixture of conformers present and shifts in the spectral characteristics. Both effects need to be considered when interpreting CD spectra in terms of secondary structure for this and other polypeptides in nonaqueous solutions.
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Affiliation(s)
- Y Chen
- Department of Crystallography, Birkbeck College, University of London, UK
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37
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Xu F, Wang A, Vaughn JB, Cross TA. A Catalytic Role for Protic Solvents in Conformational Interconversion. J Am Chem Soc 1996. [DOI: 10.1021/ja9600892] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Feng Xu
- Center for Interdisciplinary Magnetic Resonance at the National High Magnetic Field Laboratory Institute of Molecular Biophysics Department of Chemistry, Florida State University Tallahassee, Florida 32306
| | - Anping Wang
- Center for Interdisciplinary Magnetic Resonance at the National High Magnetic Field Laboratory Institute of Molecular Biophysics Department of Chemistry, Florida State University Tallahassee, Florida 32306
| | - J. B. Vaughn
- Center for Interdisciplinary Magnetic Resonance at the National High Magnetic Field Laboratory Institute of Molecular Biophysics Department of Chemistry, Florida State University Tallahassee, Florida 32306
| | - T. A. Cross
- Center for Interdisciplinary Magnetic Resonance at the National High Magnetic Field Laboratory Institute of Molecular Biophysics Department of Chemistry, Florida State University Tallahassee, Florida 32306
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38
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Ranganathan S, Kundu D, Tamilarasu N, Nagaraj R, Dhople VM, Jaganadham MV. The gramicidin pore: Selective tryptophan replacement with aspartic acid. Tetrahedron Lett 1996. [DOI: 10.1016/0040-4039(96)01050-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Sychev SV, Sukhanov SV, Barsukov LI, Ivanov VT. Structural polymorphism of gramicidin A channels: ion conductivity and spectral studies. J Pept Sci 1996; 2:141-56. [PMID: 9231323 DOI: 10.1002/psc.59] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/1995] [Accepted: 12/15/1995] [Indexed: 02/04/2023]
Abstract
The relation between the various spatial structures of the gramicidin A channels and their ionic conductance has been studied. For this aim, various conformations of the peptide were pre-formed in liposomal bilayer and after subsequent fusion of liposomes with planar lipid bilayer the measured channel conductance was correlated with gramicidin structures established in liposomes. To form the single-stranded pi 6.3 pi 6.3 helix the peptide and lipid were co-dissolved in TFE prior to liposome preparation. THF and other solvents were used to form parallel and antiparallel double helices. Conformation of gramicidin in liposomes made by various phosphatidylcholines was monitored by CD spectroscopy, and computer analysis of the spectra obtained was performed. After fusion of gramicidin containing liposomes with planar bilayer membranes from asolectin, the histograms of single-channel conductance were obtained. The histograms had one or three distinct peaks depending on the liposome preparation. Assignment of the structure of the channel to conductance levels was made by correlation of CD data with conductance histograms. The channel-forming analogue, des(Trp-Leu)2-gramicidin A, has been studied by the same protocol. The channel conductances of gramicidin A and the shortened analogue increase in the following order: antiparallel < parallel < pi 6.3 pi 6.3. Single-channels formed by double helices have higher dispersity of conductance than the pi 6.3 pi 6.3 helical channel. Lifetimes of the double helical and the pi 6.3 pi 6.3 helical channels are very close to each other. The data obtained were compared with theoretically predicted properties of double helices [1].
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Affiliation(s)
- S V Sychev
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow
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Jaikaran DC, Zhang Z, Woolley GA. C-terminal amino groups facilitate membrane incorporation of gramicidin derivatives. BIOCHIMICA ET BIOPHYSICA ACTA 1995; 1234:133-8. [PMID: 7533540 DOI: 10.1016/0005-2736(94)00307-b] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Gramicidin derivatives with (positively-charged) C-terminal amino groups are found to incorporate readily and refold quickly when added to dioleoylphosphatidylcholine lipid vesicles from concentrated methanol solutions. Neutral and negatively-charged derivatives do not.
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Affiliation(s)
- D C Jaikaran
- Department of Chemistry, University of Toronto, Canada
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Abdul-Manan N, Hinton JF. Conformation states of gramicidin A along the pathway to the formation of channels in model membranes determined by 2D NMR and circular dichroism spectroscopy. Biochemistry 1994; 33:6773-83. [PMID: 7515684 DOI: 10.1021/bi00188a005] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Gramicidin A incorporated into SDS (sodium dodecyl sulfate) micelles exists as a right-handed, N-to-N-terminal beta 6.3 helical dimer [Lomize, A. L., Orechov, V. Yu., & Arseniev, A.S. (1992) Bioorg. Khim. 18, 182-189]. In the incorporation procedure to achieve the ion channel state of gramicidin A in SDS micelles, trifluoroethanol (TFE) is used to solubilize the hydrophobic peptide before addition to the aqueous/micelle solution. The conformational transition of gramicidin A to form ion channels in SDS micelles, i.e., in TFE and 10% TFE/water, has been investigated using 2D NMR and CD spectroscopy. In neat TFE, gramicidin A was found to be monomeric and may possibly exist in an equilibrium of rapidly interconverting conformers of at least three different forms believed to be left- and/or right-handed alpha and beta 4.4 helices. It was found that the interconversion between these conformers was slowed down in 55% TFE as evident by the observation of at least three different sets of d alpha N COSY peaks although CD gave a net spectrum similar to that in neat TFE. In 10% TFE gramicidin A spontaneously forms a precipitate. The precipitated species were isolated and solubilized in dioxane where gramicidin conformers undergo very slow interconversion and could be characterized by NMR. At least seven different gramicidin A conformations were found in 10% TFE. Four of thes are the same types of double helices as previously found in ethanol (i.e., a symmetric left-handed parallel beta 5.6 double helix, an unsymmetric left-handed parallel beta 5.6 double helix, a symmetric left-handed antiparallel beta 5.6 double helix, a symmetric right-handed parallel beta 5.6 double helix); the fifth is possibly a symmetric right-handed antiparallel beta 5.6 double helix. There is also evidence for the presence of at least one form of monomeric species. Previous observation on the solvent history dependence in the ease of channel incorporation may be explained by the presence of several different folding pathways to channel formation. To test this proposal, the conformation of gramicidin A in 10% DMSO and 10% methanol was studied. In the former environment, the major form was a random coil with a minor population of double-stranded helices, while in the latter, NMR spectra indicate the presence of the same double-helical conformers as found in neat methanol.
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Affiliation(s)
- N Abdul-Manan
- Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville 72701
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Crisma M, Formaggio F, Pantano M, Valle G, Bonora GM, Toniolo C, Schoemaker HE, Kamphuis J. Linear oligopeptides. Part 316. Conformational characterization of syndiotactic homo-peptides from Cα,α-disubstituted glycines. ACTA ACUST UNITED AC 1994. [DOI: 10.1039/p29940001735] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Cross T, Opella S. Solid-state NMR structural studies of peptides and proteins in membranes. Curr Opin Struct Biol 1994. [DOI: 10.1016/s0959-440x(94)90220-8] [Citation(s) in RCA: 91] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Hing AW, Schaefer J. Two-dimensional rotational-echo double resonance of Val1-[1-13C]Gly2-[15N]Ala3-gramicidin A in multilamellar dimyristoylphosphatidylcholine dispersions. Biochemistry 1993; 32:7593-604. [PMID: 7687877 DOI: 10.1021/bi00080a035] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The dipolar coupling between the Gly2 13C-1 carbon and Ala3 15N-amide nitrogen was used to investigate the conformation and dynamics of the Gly2-Ala3 13C-15N peptide bond in Val1-[1-13C]Gly2-[15N]Ala3-gramicidin A incorporated into multilamellar dispersions of dimyristoylphosphatidylcholine. Measurement of the 13C-15N dipolar coupling constant D of the labeled gramicidin in a powder and the effective dipolar coupling constant De in a multilamellar dispersion was accomplished by two-dimensional rotational-echo double-resonance (2D REDOR) NMR, a magic-angle spinning experiment designed to measure weak dipolar coupling constants. The magnitudes of D and De were measured by the mirror-symmetric form of 2D REDOR, and the signs of D and De were determined relative to the sign of the isotropic indirect spin-spin coupling constant J by the mirror-asymmetric form of 2D REDOR. From knowledge of the magnitudes of D and De, four possible values were calculated for the angle between the Gly2-Ala3 13C-15N peptide bond and the gramicidin helical axis. Additional knowledge of the signs of D and De permitted the set of possible values for the peptide bond angle to be reduced to a single angle and its supplement (64 degrees, 116 degrees). This information about the Gly2-Ala3 13C-15N peptide bond angle eliminates the double-stranded, helical dimers and the left-handed, single-stranded, beta 6.3 helical dimer but supports the right-handed, single-stranded, beta 6.3 helical dimer as the structural model for gramicidin in multilamellar dispersions.
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Affiliation(s)
- A W Hing
- Department of Chemistry, Washington University, St. Louis, Missouri 63130
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Affiliation(s)
- J A Killian
- Department of Biochemistry of Membranes, University of Utrecht, Netherlands
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Wallace BA. Crystallographic studies of a transmembrane ion channel, gramicidin A. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 1992; 57:59-69. [PMID: 1375761 DOI: 10.1016/0079-6107(92)90004-p] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Affiliation(s)
- B A Wallace
- Department of Crystallography, Birkbeck College, University of London, U.K
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Koeppe RE, Providence LL, Greathouse DV, Heitz F, Trudelle Y, Purdie N, Andersen OS. On the helix sense of gramicidin A single channels. Proteins 1992; 12:49-62. [PMID: 1372741 DOI: 10.1002/prot.340120107] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
In order to resolve whether gramicidin A channels are formed by right- or left-handed beta-helices, we synthesized an optically reversed (or mirror image) analogue of gramicidin A, called gramicidin A-, to test whether it forms channels that have the same handedness as channels formed by gramicidin M- (F. Heitz et al., Biophys. J. 40:87-89, 1982). In gramicidin M- the four tryptophan residues have been replaced with phenylalanine, and the circular dichroism (CD) spectrum therefore reflects almost exclusively contributions from the polypeptide backbone. The CD spectrum of gramicidin M- in dimyristoylphosphatidylcholine vesicles is consistent with a left-handed helical backbone folding motif (F. Heitz et al., Biophys. Chem. 24:149-160, 1986), and the CD spectra of gramicidins A and A- are essentially mirror images of each other. Based on hybrid channel experiments, gramicidin A- and M- channels are structurally equivalent, while gramicidin A and A- channels are nonequivalent, being of opposite helix sense. Gramicidin A- channels are therefore left-handed, and natural gramicidin A channels in phospholipid bilayers are right-handed beta 6.3-helical dimers.
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Affiliation(s)
- R E Koeppe
- Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville 72701
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Golovanov AP, Barsukov IL, Arseniev AS, Bystrov VF, Sukhanov SV, Barsukov LI. The divalent cation-binding sites of gramicidin A transmembrane ion-channel. Biopolymers 1991; 31:425-34. [PMID: 1713797 DOI: 10.1002/bip.360310408] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The conductance of the gramicidin A single channels in glycerolmonooleate membranes is strongly reduced in the presence of Mn2+ cations. The nmr experiments were performed for N-terminal to N-terminal gramicidin A dimer formed by two right-handed single-stranded helixes incorporated into the sodium dodecyl sulfate micelles in the presence of Mn2+ ions. Dependence of the nonselective spin-lattice relaxation rates of the gramicidin A protons on Mn2+ concentration was analyzed to determine coordinates of the divalent cation binding sites. It is inferred that Mn2+ ions are bound at the channel mouths at distances of 6.4, 8.6, and 8.8 A (+/- 2 A) from the oxygen atoms of exposed carbonyl groups of D-Leu 12, 14, and 10, respectively. The bounded Mn2+ retains its hydrate shell, the size of which (approximately 6 A) exceeds the inner pore diameter (approximately 4 A). That makes the gramicidin A channel impermeable for divalent cations.
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Affiliation(s)
- A P Golovanov
- Shemyakin Institute of Bioorganic Chemistry, USSR Academy of Sciences, Moscow
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