Abstract
In the present work, we evaluated the role of gramicidin conformation in its photosensitized oxidation in organic solvents when irradiated in the presence of riboflavin. Gramicidin conformation has been described as monomeric in trifluoroethanol and as an intertwined dimer in methanol. Gramicidin showed extensive photo-oxidation upon irradiation in the presence of riboflavin in both solvents, and tryptophan residues were identified to be involved. We synthesized a gramicidin derivative methylated at position 1 of the indole ring of tryptophan to assess its effect on gramicidin conformation and photo-oxidation. Methylated gramicidin showed very similar absorption and emission spectra to gramicidin, but different conformations were identified by circular dichroism spectra. Upon irradiation, N-methylated tryptophan residues in the gramicidin derivative were not easily photo-oxidized by riboflavin compared to gramicidin. Circular dichroism spectra for gramicidin in methanol changed significantly upon irradiation in the presence of riboflavin indicating a change in conformation, while in trifluoroethanol no such changes were observed. Time-resolved fluorescence and anisotropy studies showed that oxidized gramicidin in methanol had shorter fluorescence lifetimes and a shorter rotational correlation time compared to non-irradiated gramicidin. Additionally, SDS-PAGE analysis showed a marked change in the electrophoretic pattern, whereas the high-molecular-weight bands disappeared upon irradiation. We interpret all these results in terms of a riboflavin photosensitized shift in gramicidin conformation from intertwined to monomeric.
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References
B. A. Wallace, Gramicidin Channels and Pores, Annu. Rev. Biophys. Biophys. Chem., 1990, 19, 127–157.
R. E. Koeppe II and O. S. Anderson, Engineering the Gramicidin Channel, Annu. Rev. Biophys. Biomol. Struct., 1996, 25, 231–258.
G. V. Miloshevsky and P. C. Jordan, Permeation in Ion Channels: The Interplay of Structure and Theory, Trends Neurosci., 2004, 27, 308–314.
D. W. Urry, The Gramicidin A Transmembrane Channel: A Proposed pi(L,D) Helix, Proc. Natl. Acad. Sci. U. S. A., 1971, 68, 672–676.
W. R. Veatch, E. T. Fossel and E. R. Blout, The Conformation of Gramicidin A, Biochemistry, 1974, 13, 5249–5256.
G. N. Ramachnandran and R. Chandrasekaran, Conformation of Peptide Chains Containing Both L- and D-residues. I. Helical Structures With Alternating L- and D-residues With Special Reference to the LD-ribbon and the LD-helices, Indian J. Biochem. Biophys., 1972, 9, 1–11.
B. A. Wallace, Gramicidin A Adopts Distinctly Different Conformations in Membranes and in Organic Solvents, Biopolymers, 1983, 22, 397–402.
P. V. LoGrasso, F. Moll III and T. A. Cross, Solvent History Dependence of Gramicidin A Conformations in Hydrated Lipid Bilayers, Biophys. J., 1988, 54, 259–267.
W. R. Veatch and E. R. Blout, The Aggregation of Gramicidin A in Solution, Biochemistry, 1974, 13, 5257–5264.
J. A. Killian, K. U. Prasad, D. Hains and D. W. Urry, The Membrane as an Environment of Minimal Interconversion. A Circular Dichroism Study on the Solvent Dependence of the Conformational Behavior of Gramicidin in Diacylphosphatidylcholine Model Membranes, Biochemistry, 1988, 27, 4848–4855.
D. A. Kelkar and A. Chattopadhyay, Membrane Interfacial Localization of Aromatic Amino Acids and Membrane Protein Function, J. Biosci., 2006, 31, 297–302.
O. S. Andersen, D. V. Greathouse, L. L. Providence, M. D. Becker, R. E. Koeppe II, Importance of Tryptophan Dipoles for Protein Function: 5-Fluorination of Tryptophans in Gramicidin A Channels, J. Am. Chem. Soc., 1998, 120, 5142–5146.
A. Chattopadhyay, S. S. Rawat, D. V. Greathouse, D. A. Kelkar, R. E. Koeppe II, Role of Tryptophan Residues in Gramicidin Channel Organization and Function, Biophys. J., 2008, 95, 166–175.
S. S. Rawat, D. A. Kelkar and A. Chattopadhyay, Monitoring Gramicidin Conformations in Membranes: A Fluorescence Approach, Biophys. J., 2004, 87, 831–843.
A. M. Oconnell, R. E. Koeppe II and O. S. Andersen, Kinetics of Gramicidin Channel Formation in Lipid Bilayers - Transmembrane Monomer Association, Science, 1990, 250, 1256–1259.
R. R. Ketchem, W. Hu and T. A. Cross, High-Resolution Conformation of Gramicidin A in a Lipid Bilayer by Solid-state NMR, Science, 1993, 261, 1457–1460.
S. Mukherjee and A. Chattopadhyay, Motionally Restricted Tryptophan Environments at the Peptide-lipid Interface of Gramicidin Channels, Biochemistry, 1994, 33, 5089–5097.
P. Daumas, F. Heitz, L. Ranjalahy-Rasoloarijao and R. Lazaro, Gramicidin A Analogs: Influence of the Substitution of the Tryptophans by Naphthylalanines, Biochimie, 1989, 71, 77–81.
C. Barth and G. Stark, Radiation Inactivation of Ion Channels Formed by Gramicidin A. Protection by Lipid Double Bonds and by Alpha-Tocopherol, Biochim. Biophys. Acta, 1991, 1066, 54–58.
A. A. Sobko, M. A. Vigasina, T. I. Rokitskaya, E. A. Kotova, S. D. Zakharov, W. A. Cramer and Y. N. Antonenko, Chemical and Photochemical Modification of Colicin E1 and Gramicidin A in Bilayer Lipid Membranes, J. Membr. Biol., 2004, 199, 51–62.
M. Sträble and G. Stark, Photodynamic Inactivation of an Ion Channel: Gramicidin A, Photochem. Photobiol., 1992, 55, 461–463.
T. I. Rokitskaya, Y. N. Antonenko and E. A. Kotova, The Interaction Of Phthalocyanine With Planar Lipid Bilayers. Photodynamic Inactivation Of Gramicidin Channels, FEBS Lett., 1993, 329, 332–335.
L. Kunz, U. Zeidler, K. Haegele, M. Przybylski and G. Stark, Photodynamic and Radiolytic Inactivation of Ion Channels Formed by Gramicidin A: Oxidation and Fragmentation, Biochemistry, 1995, 34, 11895–11903.
T. I. Rokitskaya, M. Block, Y. N. Antonenko, E. A. Kotova and P. Pohl, Photosensitizer Binding to Lipid Bilayers as a Precondition for the Photoinactivation of Membrane Channels, Biophys. J., 2000, 78, 2572–2580.
E. A. Dutseva, Y. N. Antonenko, E. A. Kotova, J. R. Pfeifer and U. Koert, Sensitized Photoinactivation Of Minigramicidin Channels In Bilayer Lipid Membranes, Biochim. Biophys. Acta, 2007, 1768, 1230–1237.
D. I. Pattinson, A. S. Rahmanto and M. J. Davies, Photo-oxidation of Proteins, Photochem. Photobiol. Sci., 2012, 11, 38–53.
I. Ferrer and E. Silva, Study of a Photo-induced Lysozyme-Riboflavin Bond, Radiat. Environ. Biophys., 1985, 24, 63–70.
E. Silva and A. M. Edwards, Flavins: Photochemistry and Photobiology, Royal Society of Chemistry, Cambridge, UK, 2006.
Y. Zhang, H. Görner, Flavin-sensitized Photo-oxidation of Lyzozyme and Serum Albumin, Photochem. Photobiol., 2009, 85, 943–948.
E. G. Perez, B. K. Cassels, C. Eibl and D. Gundisch, Synthesis and Evaluation of N1-alkylindole-3-ylalkylammonium Compounds as Nicotinic Acetylcholine Receptor Ligands, Bioorg. Med. Chem., 2012, 20, 3719–3727.
J. R. Lakowicz, Principles of Fluorescence Spectroscopy, Springer, New York, 4th edn, 2006.
M.-P. Pileni, P. Walrant and R. Santus, Electronic Properties of N-Formylkynurenine and Related Compounds, J. Phys. Chem., 1976, 80, 1804–1809.
D. W. Urry, J. D. Glickson, D. F. Mayers and J. Haider, Spectroscopic Studies on the Conformation of Gramicidin A. Evidence for a New Helical Conformation, Biochemistry, 1972, 11, 487–493.
Y. Chen and B. A. Wallace, Binding of Alkaline Cations to the Double-Helical Form of Gramicidin, Biophys. J., 1996, 71, 163–170.
Y. Chen and B. A. Wallace, Solvent Effects on the Conformation and Far UV CD Spectra of Gramicidin, Biopolymers, 1997, 42, 771–781.
J. M. Beechem and L. Brand, Time-Resolved Fluorescence of Proteins, Annu. Rev. Biochem., 1985, 54, 43–71.
S. Weinstein, B. A. Wallace, J. S. Morrow and W. R. Veatch, Conformation of the Gramicidin A Transmembrane Channel: A 13C Nuclear Magnetic Resonance Study of 13C-enriched Gramicidin in Phosphatidylcholine Vesicles, J. Mol. Biol., 1980, 143, 1–19.
J. A. Killian and D. W. Urry, Conformation of Gramicidin in Relation to its Ability to Form Bilayers With Lysophosphatidylcholine, Biochemistry, 1988, 27, 7295–7301.
O. S. Andersen, L. L. Providence, R. E. Koeppe II, Gramicidin Channels Are Right-Handed Beta-Helical Dimers, Biophys. J., 1990, 57, A100–A100.
O. S. Andersen, G. Saberwal, D. V. Greathouse, R. E. Koeppe II, Gramicidin Channels - A Solvable Membrane “Protein” Folding Problem, Indian J. Biochem. Biophys., 1996, 33, 331–342.
O. S. Andersen, C. Nielsen, A. M. Maer, J. A. Lundbaek, M. Goulian, R. E. Koeppe II, Gramicidin channels: Molecular force transducers in lipid bilayers, Biol. Skrif, 1998, 49, 75–82.
D. A. Kelkar and A. Chattopadhyay, Monitoring Ion Channel Conformations in Membranes Utilizing a Novel Dual Fluorescence Quenching Approach, Biochem. Biophys. Res. Commun., 2006, 343, 483–488.
A. V. Krylov, Y. N. Antonenko, A. A. Yaroslavov, T. I. Rokitskaya, E. A. Kotova, R. E. Koeppe II, D. V. Greathouse and O. S. Andersen, Polylysine Decelerates Channel Kinetics of Negatively Charged Gramicidin as Shown by Sensitized Photoinactivation, Biophys. J., 1998, 74, A387–A387.
M. A. Sánchez, A. M. Mainar, J. I. Pardo, M. C. López and J. S. Urieta, Solubility of Nonpolar Gases in 2,2,2-Trifluoroethanol and 1,1,1,3,3,3-Hexafluoropropan-2-ol at Several Temperatures and 101.33 kPa Partial Pressure of Gas, Can. J. Chem., 2001, 79, 1460–1465.
R. Battino, T. R. Rettich and T. Tominaga, The Solubility of Oxygen and Ozone in Liquids, J. Phys. Chem. Ref. Data, 1983, 12, 163–178.
R. W. Redmond and J. N. Gamlin, A Compilation of Singlet Oxygen Yields from Biologically Relevant Molecules, Photochem. Photobiol., 1999, 70, 391–475.
E. Lemp, C. Valencia and A. L. Zanocco, Solvent Effects on Reactions of Singlet Molecular Oxygen With Antimalarial Drugs, J. Photochem. Photobiol., A, 2004, 168, 91–96.
N. J. Turro, Modern molecular photochemistry, University Science Books, USA, 1991.
S. Haldar, A. Chaudhuri, H. Gu, R. E. Koeppe II, M. Kombrabail, G. Krishnamoorthy and A. Chattopadhyay, Membrane Organization and Dynamics of ‘Inner Pair’ and ‘Outer Pair’ Tryptophan Residues in Gramicidin Channels, J. Phys. Chem. B, 2012, 116, 11056–11064.
A. Chaudhuri, S. Haldar, H. Sun, R. E. Koeppe II and A. Chattopadhyay, Importance of Indole N-H Hydrogen Bonding In The Organization and Dynamics of Gramicidin Channels, Biochim. Biophys. Acta, 2014, 1838, 419–428.
H. Sun, D. V. Greathouse, O. S. Andersen, R. E. Koeppe II, The Preference of Tryptophan for Membrane Interfaces: Insights From N-Methylation Of Tryptophans In Gramicidin Channels, J. Biol. Chem., 2008, 283, 22233–22243.
M. Montalti, A. Credi, L. Prodi and M. T. Gandolfi, Handbook of photochemistry, USA, 2006.
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Electronic supplementary information (ESI) available: 1H NMR, 13C NMR, absorption and emission spectra for 1-methyl Trp, MS analysis of Gr and MetGr, Gr photo-oxidation in TFE, and SDS-PAGE of MetGr. See DOI: 10.1039/c4pp00414k
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Fuentealba, D., López, J.J., Palominos, M. et al. Gramicidin conformational changes during riboflavin photosensitized oxidation in solution and the effect of N-methylation of tryptophan residues. Photochem Photobiol Sci 14, 748–756 (2015). https://doi.org/10.1039/c4pp00414k
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DOI: https://doi.org/10.1039/c4pp00414k