1
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Feng RR, Wang M, Zhang W, Gai F. Unnatural Amino Acids for Biological Spectroscopy and Microscopy. Chem Rev 2024; 124:6501-6542. [PMID: 38722769 DOI: 10.1021/acs.chemrev.3c00944] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/23/2024]
Abstract
Due to advances in methods for site-specific incorporation of unnatural amino acids (UAAs) into proteins, a large number of UAAs with tailored chemical and/or physical properties have been developed and used in a wide array of biological applications. In particular, UAAs with specific spectroscopic characteristics can be used as external reporters to produce additional signals, hence increasing the information content obtainable in protein spectroscopic and/or imaging measurements. In this Review, we summarize the progress in the past two decades in the development of such UAAs and their applications in biological spectroscopy and microscopy, with a focus on UAAs that can be used as site-specific vibrational, fluorescence, electron paramagnetic resonance (EPR), or nuclear magnetic resonance (NMR) probes. Wherever applicable, we also discuss future directions.
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Affiliation(s)
- Ran-Ran Feng
- Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China
| | - Manxi Wang
- Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China
| | - Wenkai Zhang
- Department of Physics and Applied Optics Beijing Area Major Laboratory, Beijing Normal University, Beijing 100875, China
| | - Feng Gai
- Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China
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2
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Abou-Hatab S, Matsika S. Excited state hydrogen or proton transfer pathways in microsolvated n-cyanoindole fluorescent probes. Phys Chem Chem Phys 2024; 26:4511-4523. [PMID: 38240574 DOI: 10.1039/d3cp04844f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2024]
Abstract
The sensitivity of the fluorescence properties of n-cyanoindole (n-CNI) fluorescent probes to the microenvironment makes them potential reporters of protein conformation and hydration. The fluorescence intensity of 5-CNI, 6-CNI, and 7-CNI is quenched when exposed to water solvent whereas substitution on position 4 of indoles dramatically increases it. A potential mechanism for this sensitivity to water may be similar to that found in indole. The fluorescence of indole is found to be quenched when interacting with water and ammonia solvent molecules via radiationless decay through an S1 (πσ*)/S0 conical intersection caused by excited state proton or hydrogen transfer to the solvent molecules. In this study we examine this fluorescence quenching mechanism along the N-H bond stretch of n-CNI probes using water cluster models and quantum mechanical calculations of the excited states. We find that n-CNI-(H2O)1-2 clusters form cyclic or non-cyclic structures via hydrogen bonds which lead to different photochemical reaction paths that can potentially quench the fluorescence by undergoing internal conversion from S1 to S0. However, the existence of a high energy barrier along the potential energy surface of the S1 state in most cases prevents this from occurring. We show that substitution on position 4 leads to the highest energy barrier that prevents the fluorophore from accessing these non-radiative channels, in agreement with its high intensity. We also find that the energy barrier in the S1 state of non-cyclic 5-CNI-(H2O)1-2 excited complexes decreases as the number of water molecules increases, which suggests great sensitivity of the fluorescence quenching on the aqueous environment.
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3
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Gardner ED, Johnson BP, Dimas DA, McClurg HE, Severance ZC, Burgett AW, Singh S. Unlocking New Prenylation Modes: Azaindoles as a New Substrate Class for Indole Prenyltransferases. ChemCatChem 2023; 15:e202300650. [PMID: 37954549 PMCID: PMC10634513 DOI: 10.1002/cctc.202300650] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2023] [Indexed: 11/14/2023]
Abstract
Aza-substitution, the replacement of aromatic CH groups with nitrogen atoms, is an established medicinal chemistry strategy for increasing solubility, but current methods of accessing functionalized azaindoles are limited. In this work, indole-alkylating aromatic prenyltransferases (PTs) were explored as a strategy to directly functionalize azaindole-substituted analogs of natural products. For this, a series of aza-l-tryptophans (Aza-Trp) featuring N-substitution of every aromatic CH position of the indole ring and their corresponding cyclic Aza-l-Trp-l-proline dipeptides (Aza-CyWP), were synthesized as substrate mimetics for the indole-alkylating PTs FgaPT2, CdpNPT, and FtmPT1. We then demonstrated most of these substrate analogs were accepted by a PT, and the regioselectivity of each prenylation was heavily influenced by the position of the N-substitution. Remarkably, FgaPT2 was found to produce cationic N-prenylpyridinium products, representing not only a new substrate class for indole PTs but also a previously unobserved prenylation mode. The discovery that nitrogenous indole bioisosteres can be accepted by PTs thus provides access to previously unavailable chemical space in the search for bioactive indolediketopiperazine analogs.
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Affiliation(s)
- Eric D. Gardner
- Department of Chemistry and Biochemistry, University of Oklahoma, Stephenson Life Sciences Research Center, Norman, Oklahoma 73019, United States
| | - Bryce P. Johnson
- Department of Chemistry and Biochemistry, University of Oklahoma, Stephenson Life Sciences Research Center, Norman, Oklahoma 73019, United States
| | - Dustin A. Dimas
- Department of Chemistry and Biochemistry, University of Oklahoma, Stephenson Life Sciences Research Center, Norman, Oklahoma 73019, United States
| | - Heather E. McClurg
- Department of Chemistry and Biochemistry, University of Oklahoma, Stephenson Life Sciences Research Center, Norman, Oklahoma 73019, United States
| | - Zachary C. Severance
- Department of Pharmaceutical Sciences, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73117, United States
| | - Anthony W. Burgett
- Department of Pharmaceutical Sciences, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73117, United States
| | - Shanteri Singh
- Department of Chemistry and Biochemistry, University of Oklahoma, Stephenson Life Sciences Research Center, Norman, Oklahoma 73019, United States
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4
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Sen P, Karn R, Kanake DW, Emerson I A, Khan JM, Ahmad A. Picloram binds to the h1 and h4 helices of HSA domain IIIA at drug binding site 2. Int J Biol Macromol 2023; 242:124836. [PMID: 37201887 DOI: 10.1016/j.ijbiomac.2023.124836] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2023] [Revised: 05/07/2023] [Accepted: 05/08/2023] [Indexed: 05/20/2023]
Abstract
Picloram (PC) is a systemic herbicide that controls herbaceous weeds and woody plants. HSA, the most abundant protein in human physiology, binds to all exogenic and endogenic ligands. PC is a stable molecule (t1/2~157-513 days) and a potential threat to human health via the food chain. HSA and PC binding study has been done to decipher the location and thermodynamics of binding. It has been studied with prediction tools like autodocking and MD simulation and then confirmed with fluorescence spectroscopy. HSA fluorescence was quenched by PC at pH 7.4 (N state), pH 3.5 (F state), and pH 7.4 with 4.5 M urea (I state) at temperatures 283 K, 297 K, and 303 K. The location of binding was found to be interdomain between II and III which overlaps with drug binding site 2. The binding was spontaneous, and entropy-driven that show a noticeable increase in binding with the increase in temperature. No secondary structure change at the native state has been observed due to binding. The binding results are important to understand the physiological assimilation of PC. In silico predictions and the results of spectroscopic studies unambiguously indicate the locus and nature of the binding.
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Affiliation(s)
- Priyankar Sen
- Centre for Bio-Separation Technology, Vellore Institute of Technology, Vellore 632014, Tamilnadu, India.
| | - Rohit Karn
- School of Biosciences and Technology, Vellore Institute of Technology, Vellore 632014, Tamilnadu, India
| | - Diksha Waghuji Kanake
- Centre for Bio-Separation Technology, Vellore Institute of Technology, Vellore 632014, Tamilnadu, India
| | - Arnold Emerson I
- School of Biosciences and Technology, Vellore Institute of Technology, Vellore 632014, Tamilnadu, India
| | - Javed Masood Khan
- Department of Food Science and Nutrition, College of Food and Agricultural Sciences, King Saud University, Riyadh 11451, Saudi Arabia.
| | - Anis Ahmad
- Department of Radiation Oncology, Miller School of Medicine/Sylvester Cancer Center, University of Miami, Miami, FL, USA.
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5
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Shao J, Kuiper BP, Thunnissen AMWH, Cool RH, Zhou L, Huang C, Dijkstra BW, Broos J. The Role of Tryptophan in π Interactions in Proteins: An Experimental Approach. J Am Chem Soc 2022; 144:13815-13822. [PMID: 35868012 PMCID: PMC9354243 DOI: 10.1021/jacs.2c04986] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
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In proteins, the amino acids Phe, Tyr, and especially
Trp are frequently
involved in π interactions such as π–π, cation−π,
and CH−π bonds. These interactions are often crucial
for protein structure and protein–ligand binding. A powerful
means to study these interactions is progressive fluorination of these
aromatic residues to modulate the electrostatic component of the interaction.
However, to date no protein expression platform is available to produce
milligram amounts of proteins labeled with such fluorinated amino
acids. Here, we present a Lactococcus lactis Trp
auxotroph-based expression system for efficient incorporation (≥95%)
of mono-, di-, tri-, and tetrafluorinated, as well as a methylated
Trp analog. As a model protein we have chosen LmrR, a dimeric multidrug
transcriptional repressor protein from L. lactis. LmrR binds aromatic drugs, like daunomycin and riboflavin, between
Trp96 and Trp96′ in the dimer interface. Progressive fluorination
of Trp96 decreased the affinity for the drugs 6- to 70-fold, clearly
establishing the importance of electrostatic π–π
interactions for drug binding. Presteady state kinetic data of the
LmrR–drug interaction support the enthalpic nature of the interaction,
while high resolution crystal structures of the labeled protein–drug
complexes provide for the first time a structural view of the progressive
fluorination approach. The L. lactis expression system
was also used to study the role of Trp68 in the binding of riboflavin
by the membrane-bound riboflavin transport protein RibU from L. lactis. Progressive fluorination of Trp68 revealed a
strong electrostatic component that contributed 15–20% to the
total riboflavin-RibU binding energy.
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Affiliation(s)
- Jinfeng Shao
- Groningen Biomolecular Science and Biotechnology Institute (GBB), University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands
| | - Bastiaan P Kuiper
- Groningen Biomolecular Science and Biotechnology Institute (GBB), University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands
| | - Andy-Mark W H Thunnissen
- Groningen Biomolecular Science and Biotechnology Institute (GBB), University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands
| | - Robbert H Cool
- Department of Chemical and Pharmaceutical Biology, University of Groningen, Antonius Deusinglaan 1, 9713 AV Groningen, The Netherlands
| | - Liang Zhou
- Groningen Biomolecular Science and Biotechnology Institute (GBB), University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands
| | - Chenxi Huang
- Groningen Biomolecular Science and Biotechnology Institute (GBB), University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands
| | - Bauke W Dijkstra
- Groningen Biomolecular Science and Biotechnology Institute (GBB), University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands
| | - Jaap Broos
- Groningen Biomolecular Science and Biotechnology Institute (GBB), University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands
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6
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Lu M, Toptygin D, Xiang Y, Shi Y, Schwieters CD, Lipinski EC, Ahn J, Byeon IJL, Gronenborn AM. The Magic of Linking Rings: Discovery of a Unique Photoinduced Fluorescent Protein Crosslink. J Am Chem Soc 2022; 144:10809-10816. [PMID: 35574633 PMCID: PMC9233106 DOI: 10.1021/jacs.2c02054] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
![]()
Fluorosubstituted tryptophans serve
as valuable probes for fluorescence
and nuclear magnetic resonance (NMR) studies of proteins. Here, we
describe an unusual photoreactivity introduced by replacing the single
tryptophan in cyclophilin A with 7-fluoro-tryptophan. UV exposure
at 282 nm defluorinates 7-fluoro-tryptophan and crosslinks it to a
nearby phenylalanine, generating a bright fluorophore. The crosslink-containing
fluorescent protein possesses a large quantum yield of ∼0.40
with a fluorescence lifetime of 2.38 ns. The chemical nature of the
crosslink and the three-dimensional protein structure were determined
by mass spectrometry and NMR spectroscopy. To the best of our knowledge,
this is the first report of a Phe–Trp crosslink in a protein.
Our finding may break new ground for developing novel fluorescence
probes and for devising new strategies to exploit aromatic crosslinks
in proteins.
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Affiliation(s)
- Manman Lu
- Department of Structural Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261, United States
- Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261, United States
| | - Dmitri Toptygin
- Department of Biology, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Yufei Xiang
- Department of Cell Biology, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, United States
| | - Yi Shi
- Department of Cell Biology, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, United States
| | - Charles D. Schwieters
- Computational Biomolecular Magnetic Resonance Core, Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892-0520, United States
| | - Emma C. Lipinski
- Department of Structural Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261, United States
| | - Jinwoo Ahn
- Department of Structural Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261, United States
- Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261, United States
| | - In-Ja L. Byeon
- Department of Structural Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261, United States
- Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261, United States
| | - Angela M. Gronenborn
- Department of Structural Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261, United States
- Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261, United States
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7
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Urvashi, Senthil Kumar JB, Das P, Tandon V. Development of Azaindole-Based Frameworks as Potential Antiviral Agents and Their Future Perspectives. J Med Chem 2022; 65:6454-6495. [PMID: 35477274 PMCID: PMC9063994 DOI: 10.1021/acs.jmedchem.2c00444] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2022] [Indexed: 11/29/2022]
Abstract
The azaindole (AI) framework continues to play a significant role in the design of new antiviral agents. Modulating the position and isosteric replacement of the nitrogen atom of AI analogs notably influences the intrinsic physicochemical properties of lead compounds. The intra- and intermolecular interactions of AI derivatives with host receptors or viral proteins can also be fine tuned by carefully placing the nitrogen atom in the heterocyclic core. This wide-ranging perspective article focuses on AIs that have considerable utility in drug discovery programs against RNA viruses. The inhibition of influenza A, human immunodeficiency, respiratory syncytial, neurotropic alpha, dengue, ebola, and hepatitis C viruses by AI analogs is extensively reviewed to assess their plausible future potential in antiviral drug discovery. The binding interaction of AIs with the target protein is examined to derive a structural basis for designing new antiviral agents.
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Affiliation(s)
- Urvashi
- Drug Discovery Laboratory, Special Centre for
Molecular Medicine, Jawaharlal Nehru University, New Delhi 110
067, India
- Department of Chemistry, University of
Delhi, New Delhi 110007, India
| | - J. B. Senthil Kumar
- Drug Discovery Laboratory, Special Centre for
Molecular Medicine, Jawaharlal Nehru University, New Delhi 110
067, India
| | - Parthasarathi Das
- Department of Chemistry, Indian Institute
of Technology (ISM), Dhanbad 826004, India
| | - Vibha Tandon
- Drug Discovery Laboratory, Special Centre for
Molecular Medicine, Jawaharlal Nehru University, New Delhi 110
067, India
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8
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Hartman MCT. Non-canonical Amino Acid Substrates of E. coli Aminoacyl-tRNA Synthetases. Chembiochem 2022; 23:e202100299. [PMID: 34416067 PMCID: PMC9651912 DOI: 10.1002/cbic.202100299] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2021] [Revised: 08/03/2021] [Indexed: 01/07/2023]
Abstract
In this comprehensive review, I focus on the twenty E. coli aminoacyl-tRNA synthetases and their ability to charge non-canonical amino acids (ncAAs) onto tRNAs. The promiscuity of these enzymes has been harnessed for diverse applications including understanding and engineering of protein function, creation of organisms with an expanded genetic code, and the synthesis of diverse peptide libraries for drug discovery. The review catalogues the structures of all known ncAA substrates for each of the 20 E. coli aminoacyl-tRNA synthetases, including ncAA substrates for engineered versions of these enzymes. Drawing from the structures in the list, I highlight trends and novel opportunities for further exploitation of these ncAAs in the engineering of protein function, synthetic biology, and in drug discovery.
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Affiliation(s)
- Matthew C T Hartman
- Department of Chemistry and Massey Cancer Center, Virginia Commonwealth University, 1001 W Main St., Richmond, VA 23220, USA
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9
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Micikas RJ, Ahmed IA, Acharyya A, Smith AB, Gai F. Tuning the electronic transition energy of indole via substitution: application to identify tryptophan-based chromophores that absorb and emit visible light. Phys Chem Chem Phys 2021; 23:6433-6437. [PMID: 33710175 DOI: 10.1039/d0cp06710e] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Fluorescent amino acids (FAAs) offer significant advantages over fluorescent proteins in applications where the fluorophore size needs to be limited or minimized. A long-sought goal in biological spectroscopy/microcopy is to develop visible FAAs by modifying the indole ring of tryptophan. Herein, we examine the absorption spectra of a library of 4-substituted indoles and find that the frequency of the absorption maximum correlates linearly with the global electrophilicity index of the substituent. This finding permits us to identify two promising candidates, 4-formyltryptophan (4CHO-Trp) and 4-nitrotryptophan (4NO2-Trp), both of which can be excited by visible light. Further fluorescence measurements indicate that while 4CHO-indole (and 4CHO-Trp) emits cyan fluorescence with a reasonably large quantum yield (ca. 0.22 in ethanol), 4NO2-indole is essentially non-fluorescent, suggesting that 4CHO-Trp (4NO2-Trp) could be useful as a fluorescence reporter (quencher). In addition, we present a simple method for synthesizing 4CHO-Trp.
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Affiliation(s)
- Robert J Micikas
- Department of Chemistry, University of Pennsylvania, 231 South 34th Street, Philadelphia, Pennsylvania 19104, USA.
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10
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Fang H. A theoretical study on water-assisted excited state double proton transfer process in substituted 2,7-diazaindole-H2O complex. Theor Chem Acc 2020. [DOI: 10.1007/s00214-020-02655-3] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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11
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Boknevitz K, Italia JS, Li B, Chatterjee A, Liu SY. Synthesis and characterization of an unnatural boron and nitrogen-containing tryptophan analogue and its incorporation into proteins. Chem Sci 2019; 10:4994-4998. [PMID: 31183048 PMCID: PMC6524624 DOI: 10.1039/c8sc05167d] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2018] [Accepted: 04/15/2019] [Indexed: 12/12/2022] Open
Abstract
A boron and nitrogen containing unnatural analogue of tryptophan is synthesized and incorporated into proteins.
A boron and nitrogen containing unnatural analogue of tryptophan is synthesized through the functionalization of BN-indole. The spectroscopic properties of BN-tryptophan are reported with respect to the natural tryptophan, and the incorporation of BN-tryptophan into proteins expressed in E. coli using selective pressure incorporation is described. This work shows that a cellular system can recognize the unnatural, BN-containing tryptophan. More importantly, it presents the first example of an azaborine containing amino acid being incorporated into proteins.
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Affiliation(s)
- Katherine Boknevitz
- Department of Chemistry , Boston College , Chestnut Hill , MA 02467 , USA . ;
| | - James S Italia
- Department of Chemistry , Boston College , Chestnut Hill , MA 02467 , USA . ;
| | - Bo Li
- Department of Chemistry , Boston College , Chestnut Hill , MA 02467 , USA . ;
| | - Abhishek Chatterjee
- Department of Chemistry , Boston College , Chestnut Hill , MA 02467 , USA . ;
| | - Shih-Yuan Liu
- Department of Chemistry , Boston College , Chestnut Hill , MA 02467 , USA . ;
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12
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Zhang K, Ahmed IA, Kratochvil HT, DeGrado WF, Gai F, Jo H. Synthesis and application of the blue fluorescent amino acid l-4-cyanotryptophan to assess peptide-membrane interactions. Chem Commun (Camb) 2019; 55:5095-5098. [PMID: 30957824 PMCID: PMC6508085 DOI: 10.1039/c9cc01152h] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Recently, l-4-cyanotryptophan has been shown to be an efficient blue fluorescence emitter, with the potential to enable novel applications in biological spectroscopy and microscopy. However, lack of facile synthetic routes to this unnatural amino acid limits its wide use. Herein, we describe an expedient approach to synthesize Fmoc protected l-4-cyanotryptophan with high optical purity (>99%). Additionally, we test the utility of this blue fluorophore in imaging cell-membrane-bound peptides and in determining peptide-membrane binding constants.
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Affiliation(s)
- Kui Zhang
- Department of Pharmaceutical Chemistry, University of California, San Francisco, CA 94158, United States
| | - Ismail A. Ahmed
- Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Huong T. Kratochvil
- Department of Pharmaceutical Chemistry, University of California, San Francisco, CA 94158, United States
| | - William F. DeGrado
- Department of Pharmaceutical Chemistry, University of California, San Francisco, CA 94158, United States
| | - Feng Gai
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Hyunil Jo
- Department of Pharmaceutical Chemistry, University of California, San Francisco, CA 94158, United States
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13
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Hilaire MR, Mukherjee D, Troxler T, Gai F. Solvent Dependence of Cyanoindole Fluorescence Lifetime. Chem Phys Lett 2017; 685:133-138. [PMID: 29225366 DOI: 10.1016/j.cplett.2017.07.038] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Several cyanotryptophans have been shown to be useful biological fluorophores. However, how their fluorescence lifetimes vary with solvent has not been examined. In this regard, herein we measure the fluorescence decay kinetics as well as the absorption and emission spectra of six cyanoindoles in different solvents. In particular, we find, among other results, that only 4-cyanoindole affords a long fluorescence lifetime and hence high quantum yield in H2O. Therefore, our measurements provide not only a guide for choosing which cyanotryptophan to use in practice but also data for computational modeling of the substitution effect on the electronic transitions of indole.
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Affiliation(s)
- Mary Rose Hilaire
- Department of Chemistry, University of Pennsylvania, 231 South 34 Street, Philadelphia, PA 19104, USA
| | - Debopreeti Mukherjee
- Department of Chemistry, University of Pennsylvania, 231 South 34 Street, Philadelphia, PA 19104, USA
| | - Thomas Troxler
- Department of Chemistry, University of Pennsylvania, 231 South 34 Street, Philadelphia, PA 19104, USA.,Ultrafast Optical Processes Laboratory, University of Pennsylvania, 231 South 34 Street, Philadelphia, PA 19104, USA
| | - Feng Gai
- Department of Chemistry, University of Pennsylvania, 231 South 34 Street, Philadelphia, PA 19104, USA.,Ultrafast Optical Processes Laboratory, University of Pennsylvania, 231 South 34 Street, Philadelphia, PA 19104, USA
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14
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Abstract
Many fluorescent proteins are currently available for biological spectroscopy and imaging measurements, allowing a wide range of biochemical and biophysical processes and interactions to be studied at various length scales. However, in applications where a small fluorescence reporter is required or desirable, the choice of fluorophores is rather limited. As such, continued effort has been devoted to the development of amino acid-based fluorophores that do not require a specific environment and additional time to mature and have a large fluorescence quantum yield, long fluorescence lifetime, good photostability, and an emission spectrum in the visible region. Herein, we show that a tryptophan analog, 4-cyanotryptophan, which differs from tryptophan by only two atoms, is the smallest fluorescent amino acid that meets these requirements and has great potential to enable in vitro and in vivo spectroscopic and microscopic measurements of proteins.
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15
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Towards Biocontained Cell Factories: An Evolutionarily Adapted Escherichia coli Strain Produces a New-to-nature Bioactive Lantibiotic Containing Thienopyrrole-Alanine. Sci Rep 2016; 6:33447. [PMID: 27634138 PMCID: PMC5025777 DOI: 10.1038/srep33447] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2016] [Accepted: 08/25/2016] [Indexed: 11/08/2022] Open
Abstract
Genetic code engineering that enables reassignment of genetic codons to non-canonical amino acids (ncAAs) is a powerful strategy for enhancing ribosomally synthesized peptides and proteins with functions not commonly found in Nature. Here we report the expression of a ribosomally synthesized and post-translationally modified peptide (RiPP), the 32-mer lantibiotic lichenicidin with a canonical tryptophan (Trp) residue replaced by the ncAA L-β-(thieno[3,2-b]pyrrolyl)alanine ([3,2]Tpa) which does not sustain cell growth in the culture. We have demonstrated that cellular toxicity of [3,2]Tpa for the production of the new-to-nature bioactive congener of lichenicidin in the host Escherichia coli can be alleviated by using an evolutionarily adapted host strain MT21 which not only tolerates [3,2]Tpa but also uses it as a proteome-wide synthetic building block. This work underscores the feasibility of the biocontainment concept and establishes a general framework for design and large scale production of RiPPs with evolutionarily adapted host strains.
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16
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Shao J, Marcondes MFM, Oliveira V, Broos J. Development of Chemically Defined Media to Express Trp-Analog-Labeled Proteins in a Lactococcus lactis Trp Auxotroph. J Mol Microbiol Biotechnol 2016; 26:269-76. [PMID: 27172771 DOI: 10.1159/000445687] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2016] [Accepted: 03/20/2016] [Indexed: 11/19/2022] Open
Abstract
Chemically defined media for growth of Lactococcus lactis strains contain about 50 components, making them laborious and expensive growth media. However, they are crucial for metabolism studies as well as for expression of heterologous proteins labeled with unnatural amino acids. In particular, the L. lactis Trp auxotroph PA1002, overexpressing the tryptophanyl tRNA synthetase enzyme of L. lactis, is very suitable for the biosynthetic incorporation of Trp analogs in proteins because of its most relaxed substrate specificity reported towards Trp analogs. Here we present two much simpler defined media for L. lactis, which consist of only 24 or 31 components, respectively, and with which the L. lactis Trp auxotroph shows similar growth characteristics as with a 50-component chemically defined medium. Importantly, the expression levels of two recombinant proteins used for evaluation were up to 2-3 times higher in these new media than in the 50-component medium, without affecting the Trp analog incorporation efficiency. Taken together, the simplest chemically defined media reported so far for L. lactis are presented. Since L. lactis also shows auxotrophy for Arg, His, Ile, Leu Val, and Met, our simplified media may also be useful for the biosynthetic incorporation of analogs of these five amino acids.
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Affiliation(s)
- Jinfeng Shao
- Laboratory of Biophysical Chemistry and Groningen Biomolecular Sciences and Biotechnology Institute (GBB), University of Groningen, Groningen, The Netherlands
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17
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Xu J, Chen B, Callis P, Muiño PL, Rozeboom H, Broos J, Toptygin D, Brand L, Knutson JR. Picosecond fluorescence dynamics of tryptophan and 5-fluorotryptophan in monellin: slow water-protein relaxation unmasked. J Phys Chem B 2015; 119:4230-9. [PMID: 25710196 PMCID: PMC7477844 DOI: 10.1021/acs.jpcb.5b01651] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Time dependent fluorescence Stokes (emission wavelength) shifts (TDFSS) from tryptophan (Trp) following sub-picosecond excitation are increasingly used to investigate protein dynamics, most recently enabling active research interest into water dynamics near the surface of proteins. Unlike many fluorescence probes, both the efficiency and the wavelength of Trp fluorescence in proteins are highly sensitive to microenvironment, and Stokes shifts can be dominated by the well-known heterogeneous nature of protein structure, leading to what we call pseudo-TDFSS: shifts that arise from differential decay rates of subpopulations. Here we emphasize a novel, general method that obviates pseudo-TDFSS by replacing Trp by 5-fluorotryptophan (5Ftrp), a fluorescent analogue with higher ionization potential and greatly suppressed electron-transfer quenching. 5FTrp slows and suppresses pseudo-TDFSS, thereby providing a clearer view of genuine relaxation caused by solvent and protein response. This procedure is applied to the sweet-tasting protein monellin which has uniquely been the subject of ultrafast studies in two different laboratories (Peon, J.; et al. Proc. Natl. Acad. Sci. U.S.A. 2002, 99, 10964; Xu, J.; et al. J. Am. Chem. Soc. 2006, 128, 1214) that led to disparate interpretations of a 20 ps transient. They differed because of the pseudo-TDFSS present. The current study exploiting special properties of 5FTrp strongly supports the conclusion that both lifetime heterogeneity-based TDFSS and environment relaxation-based TDFSS are present in monellin and 5FTrp-monellin. The original experiments on monellin were most likely dominated by pseudo-TDFSS, whereas, in the present investigation of 5FTrp-monellin, the TDFSS is dominated by relaxation and any residual pseudo-TDFSS is overwhelmed and/or slowed to irrelevance.
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Affiliation(s)
- Jianhua Xu
- Optical Spectroscopy Section, Laboratory of Molecular Biophysics, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892, United States
| | - Binbin Chen
- Optical Spectroscopy Section, Laboratory of Molecular Biophysics, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892, United States
| | - Patrik Callis
- Department of Chemistry & Biochemistry, Montana State University, Bozeman, Montana 59717, United States
| | - Pedro L. Muiño
- Department of Chemistry, Saint Francis University, Loretto, Pennsylvania 15940, United States
| | - Henriëtte Rozeboom
- Department of Biophysical Chemistry, Groningen Biomolecular Science and Biotechnology Institute, University of Groningen, Groningen, The Netherlands
| | - Jaap Broos
- Department of Biophysical Chemistry, Groningen Biomolecular Science and Biotechnology Institute, University of Groningen, Groningen, The Netherlands
| | - Dmitri Toptygin
- Department of Biology, Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218, United States
| | - Ludwig Brand
- Department of Biology, Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218, United States
| | - Jay R. Knutson
- Optical Spectroscopy Section, Laboratory of Molecular Biophysics, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892, United States
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Biosynthetic incorporation of the azulene moiety in proteins with high efficiency. Amino Acids 2014; 47:213-6. [PMID: 25399056 DOI: 10.1007/s00726-014-1870-4] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2014] [Accepted: 11/04/2014] [Indexed: 10/24/2022]
Abstract
Biosynthetic incorporation of β-(1-azulenyl)-L-alanine, an isostere of tryptophan, is reported using a tryptophan auxotroph expression host. The azulene moiety introduced this way in proteins features many attractive spectroscopic properties, particularly suitable for in vivo studies.
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19
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Shen JY, Chao WC, Liu C, Pan HA, Yang HC, Chen CL, Lan YK, Lin LJ, Wang JS, Lu JF, Chun-Wei Chou S, Tang KC, Chou PT. Probing water micro-solvation in proteins by water catalysed proton-transfer tautomerism. Nat Commun 2014; 4:2611. [PMID: 24177573 DOI: 10.1038/ncomms3611] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2013] [Accepted: 09/13/2013] [Indexed: 11/09/2022] Open
Abstract
Scientists have made tremendous efforts to gain understanding of the water molecules in proteins via indirect measurements such as molecular dynamic simulation and/or probing the polarity of the local environment. Here we present a tryptophan analogue that exhibits remarkable water catalysed proton-transfer properties. The resulting multiple emissions provide unique fingerprints that can be exploited for direct sensing of a site-specific water environment in a protein without disrupting its native structure. Replacing tryptophan with the newly developed tryptophan analogue we sense different water environments surrounding the five tryptophans in human thromboxane A₂ synthase. This development may lead to future research to probe how water molecules affect the folding, structures and activities of proteins.
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Affiliation(s)
- Jiun-Yi Shen
- 1] Department of Chemistry, Center for Emerging Material and Advanced Devices, National Taiwan University, Taipei 10617, Taiwan [2]
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20
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Abstract
Biosynthetic incorporation of Trp analogs in a protein can help in its characterization using fluorescence spectroscopy and other methodologies like NMR and phosphorescence. Here a protocol is presented resulting in the efficient incorporation of Trp analogs in a recombinant protein, using an Escherichia coli Trp auxotroph. An overview of recent developments in the Trp analog incorporation field is also presented.
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Affiliation(s)
- Jaap Broos
- Laboratory of Biophysical Chemistry and Groningen Biomolecular Science and Biotechnology Institute, University of Groningen, Groningen, The Netherlands
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21
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22
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Petrović DM, Hesp BH, Broos J. Emitting State of 5-Hydroxyindole, 5-Hydroxytryptophan, and 5-Hydroxytryptophan Incorporated in Proteins. J Phys Chem B 2013; 117:10792-7. [DOI: 10.1021/jp406676j] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Affiliation(s)
- Dejan M. Petrović
- Laboratory
of Biophysical Chemistry, Groningen Biomolecular Sciences and Biotechnology
Institute, University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands
| | - Ben H. Hesp
- Zernike
Institute for Advanced Materials, University of Groningen, Nijenborgh
4, 9747 AG Groningen, The Netherlands
| | - Jaap Broos
- Laboratory
of Biophysical Chemistry, Groningen Biomolecular Sciences and Biotechnology
Institute, University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands
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23
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An expression system for the efficient incorporation of an expanded set of tryptophan analogues. Amino Acids 2013; 44:1329-36. [DOI: 10.1007/s00726-013-1467-3] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2013] [Accepted: 01/28/2013] [Indexed: 10/27/2022]
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24
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Monitoring lysin motif–ligand interactions via tryptophan analog fluorescence spectroscopy. Anal Biochem 2012; 428:111-8. [DOI: 10.1016/j.ab.2012.06.009] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2012] [Revised: 05/13/2012] [Accepted: 06/08/2012] [Indexed: 12/14/2022]
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25
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Goldberg JM, Speight LC, Fegley MW, Petersson EJ. Minimalist probes for studying protein dynamics: thioamide quenching of selectively excitable fluorescent amino acids. J Am Chem Soc 2012; 134:6088-91. [PMID: 22471784 PMCID: PMC3360930 DOI: 10.1021/ja3005094] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Fluorescent probe pairs that can be selectively excited in the presence of Trp and Tyr are of great utility in studying conformational changes in proteins. However, the size of these probe pairs can restrict their incorporation to small portions of a protein sequence where their effects on secondary and tertiary structure can be tolerated. Our findings show that a thioamide bond-a single atom substitution of the peptide backbone-can quench fluorophores that are red-shifted from intrinsic protein fluorescence, such as acridone. Using steady-state and fluorescence lifetime measurements, we further demonstrate that this quenching occurs through a dynamic electron-transfer mechanism. In a proof-of-principle experiment, we apply this technique to monitor unfolding in a model peptide system, the villin headpiece HP35 fragment. Thioamide analogues of the natural amino acids can be placed in a variety of locations in a protein sequence, allowing one to make a large number of measurements to model protein folding.
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Affiliation(s)
- Jacob M. Goldberg
- Department of Chemistry, University of Pennsylvania, 231 South 34 Street, Philadelphia, Pennsylvania 19104-6323, United States
| | - Lee C. Speight
- Department of Chemistry, University of Pennsylvania, 231 South 34 Street, Philadelphia, Pennsylvania 19104-6323, United States
| | | | - E. James Petersson
- Department of Chemistry, University of Pennsylvania, 231 South 34 Street, Philadelphia, Pennsylvania 19104-6323, United States
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26
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Hermenegildo BF, Pereira G, Abreu AS, Castanheira EM, Ferreira PM, Queiroz MJR. Phenanthrenyl-indole as a fluorescent probe for peptides and lipid membranes. J Photochem Photobiol A Chem 2011. [DOI: 10.1016/j.jphotochem.2011.04.022] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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27
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James NG, Ross JA, Stefl M, Jameson DM. Applications of phasor plots to in vitro protein studies. Anal Biochem 2010; 410:70-6. [PMID: 21078289 DOI: 10.1016/j.ab.2010.11.011] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2010] [Revised: 11/05/2010] [Accepted: 11/07/2010] [Indexed: 10/18/2022]
Abstract
In a recent article, we described the application of phasor analysis to fluorescence intensity decay data on in vitro samples. As detailed in that article, this method provides researchers with a simple graphical method for viewing lifetime data that can be used to quantify individual components of a mixture as well as to identify excited state reactions. In the current article, we extend the use of in vitro phasor analysis to intrinsic protein fluorescence. We show how alterations in the excited state properties of tryptophan residues are easily visualized using the phasor method. Specifically, we demonstrate that protein-ligand and protein-protein interactions can result in unique shifts in the location of phasor points, indicative of protein conformational changes. Application of the method to a rapid kinetic experiment is also shown. Finally, we show that the unfolding of lysozyme with either urea or guanidine hydrochloride results in different phasor trajectories, indicative of unique denaturation pathways.
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Affiliation(s)
- Nicholas G James
- Department of Cell and Molecular Biology, John A. Burns School of Medicine, University of Hawaii, Honolulu, HI 96813, USA
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28
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Neerathilingam M, Markley JL. Auto-induction medium containing glyphosate for high-level incorporation of unusual aromatic amino acids into proteins. Biotechniques 2010; 49:659-61. [PMID: 20854268 PMCID: PMC3023234 DOI: 10.2144/000113491] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
We describe the use of an auto-induction medium containing N-(phosphono-methyl)glycine (glyphosate) as a means for high-level introduction of nonstandard aromatic amino acids into a protein. We illustrate this approach by preparing maltose binding protein (MBP) wherein all eight tryptophan residues have been replaced with 6-fluorotryptophan at an incorporation level of 99.3%. Such a high level of incorporation is important for spectroscopic investigations, in particular 19F NMR, because each species' differing amino acid sequence potentially yields a different peak pattern that complicates spectral analysis.
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29
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Taskent-Sezgin H, Marek P, Thomas R, Goldberg D, Chung J, Carrico I, Raleigh DP. Modulation of p-cyanophenylalanine fluorescence by amino acid side chains and rational design of fluorescence probes of alpha-helix formation. Biochemistry 2010; 49:6290-5. [PMID: 20565125 DOI: 10.1021/bi100932p] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
p-Cyanophenylalanine is an extremely useful fluorescence probe of protein structure that can be recombinantly and chemically incorporated into proteins. The probe has been used to study protein folding, protein-membrane interactions, protein-peptide interactions, and amyloid formation; however, the factors that control its fluorescence are not fully understood. Hydrogen bonding to the cyano group is known to play a major role in modulating the fluorescence quantum yield, but the role of potential side-chain quenchers has not yet been elucidated. A systematic study of the effects of different side chains on p-cyanophenylalanine fluorescence is reported. Tyr is found to have the largest effect followed by deprotonated His, Met, Cys, protonated His, Asn, Arg, and protonated Lys. Deprotonated amino groups are much more effective fluorescence quenchers than protonated amino groups. Free neutral imidazole and hydroxide ion are also effective quenchers of p-cyanophenylalanine fluorescence with Stern-Volmer constants of 39.8 and 22.1 M(-1), respectively. The quenching of p-cyanophenylalanine fluorescence by specific side chains is exploited in developing specific, high-sensitivity, fluorescence probes of helix formation. The approach is demonstrated with Ala-based peptides that contain a p-cyanophenylalanine-His or a p-cyanophenylalanine-Tyr pair located at positions i and i + 4. The p-cyanophenylalanine-His pair is most useful when the His side chain is deprotonated and is, thus, complementary to the Trp-His pair which is most sensitive when the His side chain is protonated.
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Affiliation(s)
- Humeyra Taskent-Sezgin
- Department of Chemistry, State University of New York at Stony Brook, Stony Brook, New York 11794-3400, USA
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30
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Sinkeldam RW, Greco NJ, Tor Y. Fluorescent analogs of biomolecular building blocks: design, properties, and applications. Chem Rev 2010; 110:2579-619. [PMID: 20205430 PMCID: PMC2868948 DOI: 10.1021/cr900301e] [Citation(s) in RCA: 658] [Impact Index Per Article: 47.0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Affiliation(s)
- Renatus W. Sinkeldam
- Department of Chemistry and Biochemistry, University of California, San Diego 9500 Gilman Drive, La Jolla, California 92093-0358
| | | | - Yitzhak Tor
- Department of Chemistry and Biochemistry, University of California, San Diego 9500 Gilman Drive, La Jolla, California 92093-0358
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31
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Merkel L, Hoesl MG, Albrecht M, Schmidt A, Budisa N. Blue Fluorescent Amino Acids as In Vivo Building Blocks for Proteins. Chembiochem 2010; 11:305-14. [DOI: 10.1002/cbic.200900651] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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32
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33
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James NG, Byrne SL, Mason AB. Incorporation of 5-hydroxytryptophan into transferrin and its receptor allows assignment of the pH induced changes in intrinsic fluorescence when iron is released. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2008; 1794:532-40. [PMID: 19103311 DOI: 10.1016/j.bbapap.2008.11.017] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/02/2008] [Revised: 11/11/2008] [Accepted: 11/19/2008] [Indexed: 10/21/2022]
Abstract
Human serum transferrin (hTF) is a bilobal glycoprotein that transports iron to cells. At neutral pH, diferric hTF binds with nM affinity to the transferrin receptor (TFR) on the cell surface. The complex is taken into the cell where, at the acidic pH of the endosome ( approximately pH 5.6), iron is released. Since iron coordination strongly quenches the intrinsic tryptophan fluorescence of hTF, the increase in the fluorescent signal reports the rate constant(s) of iron release. At pH 5.6, the TFR considerably enhances iron release from the C-lobe (with little effect on iron release from the N-lobe). The recombinant soluble TFR is a dimer with 11 tryptophan residues per monomer. In the hTF/TFR complex these residues could contribute to and compromise the readout ascribed to iron release from hTF. We report that compared to Fe(C) hTF alone, the increase in the fluorescent signal from the preformed complex of Fe(C) hTF and the TFR at pH 5.6 is significantly quenched (75%). To dissect the contributions of hTF and the TFR to the change in fluorescence, 5-hydroxytryptophan was incorporated into each using our mammalian expression system. Selective excitation of the samples at 280 or 315 nm shows that the TFR contributes little or nothing to the increase in fluorescence when ferric iron is released from Fe(C) hTF. Quantum yield determinations of TFR, Fe(C) hTF and the Fe(C) hTF/TFR complex strongly support our interpretation of the kinetic data.
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Affiliation(s)
- Nicholas G James
- Department of Biochemistry, University of Vermont College of Medicine, 89 Beaumont Avenue, Burlington, VT 05405-0068, USA
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34
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Vincent B, Mouledous L, Bes B, Mazarguil H, Meunier JC, Milon A, Demange P. Description of the low-affinity interaction between nociceptin and the second extracellular loop of its receptor by fluorescence and NMR spectroscopies. J Pept Sci 2008; 14:1183-94. [PMID: 18683278 DOI: 10.1002/psc.1057] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2008] [Accepted: 05/26/2008] [Indexed: 12/16/2023]
Abstract
The second extracellular loop (ECL2) of the Noc receptor has been proposed to be involved in ligand binding and selectivity. The interaction of Noc with a constrained cyclic synthetic peptide, mimicking the ECL2, has been studied using fluorescence and NMR spectroscopies. Selective binding was shown with a dissociation constant of approximately 10 microM (observed with the constrained cyclic loop and not with the open chain), and residues involved in ligand binding and selectivity have been identified. This bimolecular complex is stabilized by (i) ionic interactions between the two Noc basic motives and the ECL2 acidic residues; (ii) hydrophobic contacts involving Noc FGGF N-terminal sequence and an ECL2 tryptophane residue. Our data confirm that Noc receptor's ECL2 contributes actively to ligand binding and selectivity by providing the peptidic ligand with a low affinity-binding site.
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Affiliation(s)
- Bruno Vincent
- Université de Toulouse, Institute of Pharmacology and Structural Biology, IPBS, UPS, 31077, Toulouse, France
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35
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Abstract
Our long-term goal is the in vivo expression of intrinsically colored proteins without the need for further posttranslational modification or chemical functionalization by externally added reagents. Biocompatible (Aza)Indoles (Inds)/(Aza)Tryptophans (Trp) as optical probes represent almost ideal isosteric substitutes for natural Trp in cellular proteins. To overcome the limits of the traditionally used (7-Aza)Ind/(7-Aza)Trp, we substituted the single Trp residue in human annexin A5 (anxA5) by (4-Aza)Trp and (5-Aza)Trp in Trp-auxotrophic Escherichia coli cells. Both cells and proteins with these fluorophores possess intrinsic blue fluorescence detectable on routine UV irradiations. We identified (4-Aza)Ind as a superior optical probe due to its pronounced Stokes shift of approximately 130 nm, its significantly higher quantum yield (QY) in aqueous buffers and its enhanced quenching resistance. Intracellular metabolic transformation of (4-Aza)Ind into (4-Aza)Trp coupled with high yield incorporation into proteins is the most straightforward method for the conversion of naturally colorless proteins and cells into their blue counterparts from amino acid precursors.
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36
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El Khattabi M, van Roosmalen ML, Jager D, Metselaar H, Permentier H, Leenhouts K, Broos J. Lactococcus lactis as expression host for the biosynthetic incorporation of tryptophan analogues into recombinant proteins. Biochem J 2008; 409:193-8. [PMID: 17910535 DOI: 10.1042/bj20070909] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Incorporation of Trp (tryptophan) analogues into a protein may facilitate its structural analysis by spectroscopic techniques. Development of a biological system for the biosynthetic incorpor-ation of such analogues into proteins is of considerable importance. The Gram-negative Escherichia coli is the only prokaryotic expression host regularly used for the incorporation of Trp analogues into recombinant proteins. Here, we present the use of the versatile Gram-positive expression host Lactococcus lactis for the incorporation of Trp analogues. The availability of a tightly regulated expression system for this organism, the potential to secrete modified proteins into the growth medium and the construction of the trp-synthetase deletion strain PA1002 of L. lactis rendered this organism potentially an efficient tool for the incorporation of Trp analogues into recombinant proteins. The Trp analogues 7-azatryptophan, 5-fluorotryptophan and 5-hydroxytryptophan were incorporated with efficiencies of >97, >97 and 89% respectively. Interestingly, 5-methylTrp (5-methyltryptophan) could be incorporated with 92% efficiency. Successful biosynthetical incorporation of 5-methylTrp into recombinant proteins has not been reported previously.
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Affiliation(s)
- Mohamed El Khattabi
- Biomade Technology Foundation, Nijenborgh 4, 9747 AG Groningen, The Netherlands
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37
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Botchway SW, Parker AW, Bisby RH, Crisostomo AG. Real-time cellular uptake of serotonin using fluorescence lifetime imaging with two-photon excitation. Microsc Res Tech 2008; 71:267-73. [DOI: 10.1002/jemt.20548] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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38
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Abstract
The elementary steps in complex biochemical reaction schemes (isomerization, dissociation, and association reactions) ultimately determine how fast any system can react in responding to incoming signals and in adapting to new conditions. Many of these steps have associated rate constants that result in subsecond responses to incoming signals or externally applied changes. This chapter is concerned with the techniques that have been developed to study such rapidly reacting systems in vitro and to determine the values of the rate constants for the individual steps. We focus principally on two classes of techniques: (1) flow techniques, in which two solutions are mixed within a few milliseconds and the ensuing reaction monitored over milliseconds to seconds, and (2) relaxation techniques, in which a small perturbation to an existing equilibrium is applied within a few microseconds and the response of the system is followed over microseconds to hundreds of milliseconds. These reactions are most conveniently monitored by recording the change in some optical signal, such as absorbance or fluorescence. We discuss the instrumentation that is (commercially) available to study fast reactions and describe a number of optical probes (chromophores) that can be used to monitor the changes. We discuss the experimental design appropriate for the different experimental techniques and reaction mechanisms, as well as the fundamental theoretical concepts behind the analysis of the data obtained.
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Affiliation(s)
- John F Eccleston
- Division of Physical Biochemistry, MRC National Institute for Medical Research, The Ridgeway, Mill Hill, London NW7 1AA, United Kingdom
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39
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Kelkar DA, Chattopadhyay A. The gramicidin ion channel: A model membrane protein. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2007; 1768:2011-25. [PMID: 17572379 DOI: 10.1016/j.bbamem.2007.05.011] [Citation(s) in RCA: 260] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/2006] [Revised: 05/09/2007] [Accepted: 05/10/2007] [Indexed: 02/07/2023]
Abstract
The linear peptide gramicidin forms prototypical ion channels specific for monovalent cations and has been extensively used to study the organization, dynamics and function of membrane-spanning channels. In recent times, the availability of crystal structures of complex ion channels has challenged the role of gramicidin as a model membrane protein and ion channel. This review focuses on the suitability of gramicidin as a model membrane protein in general, and the information gained from gramicidin to understand lipid-protein interactions in particular. Special emphasis is given to the role and orientation of tryptophan residues in channel structure and function and recent spectroscopic approaches that have highlighted the organization and dynamics of the channel in membrane and membrane-mimetic media.
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Affiliation(s)
- Devaki A Kelkar
- Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500 007, India
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40
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Brennan JD, Capretta A, Yong K, Gerritsma D, Flora KK, Jones A. Sensitization of Lanthanides by Nonnatural Amino Acids¶. Photochem Photobiol 2007. [DOI: 10.1562/0031-8655(2002)0750117solbna2.0.co2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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41
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Damian M, Martin A, Mesnier D, Pin JP, Banères JL. Asymmetric conformational changes in a GPCR dimer controlled by G-proteins. EMBO J 2006; 25:5693-702. [PMID: 17139258 PMCID: PMC1698895 DOI: 10.1038/sj.emboj.7601449] [Citation(s) in RCA: 120] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2006] [Accepted: 10/04/2006] [Indexed: 11/09/2022] Open
Abstract
G-protein-coupled receptors (GPCRs) are key players in cell communication. Although long considered as monomeric, it now appears that these heptahelical proteins can form homo- or heterodimers. Here, we analyzed the conformational changes in each subunit of a receptor dimer resulting from agonist binding to either one or both subunits by measuring the fluorescent properties of a leukotriene B(4) receptor dimer with a single 5-hydroxytryptophan-labeled protomer. We show that a receptor dimer with only a single agonist-occupied subunit can trigger G-protein activation. We also show that the two subunits of the receptor dimer in the G-protein-coupled state differ in their conformation, even when both are liganded by the agonist. No such asymmetric conformational changes are observed in the absence of G-protein, indicating that the interaction of the G-protein with the receptor dimer brings specific constraints that prevent a symmetric functioning of this dimer. These data open new options for the differential signaling properties of GPCR dimers.
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Affiliation(s)
- Marjorie Damian
- UMR 5074 CNRS, Laboratoire de Chimie Biomoléculaire et Interactions Biologiques, Faculté de Pharmacie, Montpellier Cedex, France
- Université Montpellier I, Montpellier Cedex, France
| | - Aimée Martin
- UMR 5074 CNRS, Laboratoire de Chimie Biomoléculaire et Interactions Biologiques, Faculté de Pharmacie, Montpellier Cedex, France
- Université Montpellier I, Montpellier Cedex, France
| | - Danielle Mesnier
- UMR 5074 CNRS, Laboratoire de Chimie Biomoléculaire et Interactions Biologiques, Faculté de Pharmacie, Montpellier Cedex, France
- Université Montpellier I, Montpellier Cedex, France
| | - Jean-Philippe Pin
- CNRS UMR 5203, Montpellier, France
- INSERM U 661, Montpellier, France
- Université Montpellier I, Montpellier, France
- Université Montpellier II, Montpellier, France
- Département de Pharmacologie Moléculaire, Institut de Génomique Fonctionnelle, Montpellier Cedex, France
| | - Jean-Louis Banères
- UMR 5074 CNRS, Laboratoire de Chimie Biomoléculaire et Interactions Biologiques, Faculté de Pharmacie, Montpellier Cedex, France
- Université Montpellier I, Montpellier Cedex, France
- UMR 5074, CNRS, Université Montpellier I, Faculté de Pharmacie, 15 Av. Ch. Flahault, BP 14491, 34093 Montpellier Cedex 5, France. Tel.: +33 467 548 667; Fax: +33 467 548 625; E-mail:
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42
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Pan CP, Callis PR, Barkley MD. Dependence of Tryptophan Emission Wavelength on Conformation in Cyclic Hexapeptides. J Phys Chem B 2006; 110:7009-16. [PMID: 16571015 DOI: 10.1021/jp056164p] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The wavelength of maximum emission of tryptophan depends on the local electrostatic environment of the indole chromophore. The time-resolved emission spectra of seven rigid cyclic hexapeptides containing a single tryptophan residue were measured. The emission maxima of the three decay-associated spectra for the seven peptides ranged from 341 to 359 nm, suggesting that different tryptophan rotamers have different emission maxima even in the case of solvent-exposed tryptophans. This conclusion is supported by quantum mechanical/molecular dynamics simulations of the six canonical side chain rotamers of tryptophan in solvated hexapeptides. The calculated range of emission maxima for the tryptophan rotamers of the seven peptides is 344-365 nm. The precision of the wavelength calculations and the peptide, water, and charged side chain contributions to the spectral shifts are examined. The results indicate that the emission maxima of decay-associated spectra can aid in the assignment of fluorescence lifetimes to tryptophan rotamers.
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Affiliation(s)
- Chia-Pin Pan
- Department of Chemistry, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, Ohio 44106, USA
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43
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Botchway S, Barba I, Jordan R, Harmston R, Haggie P, Williams SP, Fulton A, Parker A, Brindle K. A novel method for observing proteins in vivo using a small fluorescent label and multiphoton imaging. Biochem J 2006; 390:787-90. [PMID: 15946123 PMCID: PMC1199672 DOI: 10.1042/bj20050648] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
A novel method for the fluorescence detection of proteins in cells is described in the present study. Proteins are labelled by the selective biosynthetic incorporation of 5-hydroxytryptophan and the label is detected via selective two-photon excitation of the hydroxyindole and detection of its fluorescence emission at 340 nm. The method is demonstrated in this paper with images of a labelled protein in yeast cells.
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Affiliation(s)
- Stanley W. Botchway
- *Central Laser Facility, Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire OX11 0QX, U.K
| | - Ignasi Barba
- †Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1GA, U.K
| | - Randolf Jordan
- †Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1GA, U.K
| | - Rebecca Harmston
- †Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1GA, U.K
| | - Peter M. Haggie
- †Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1GA, U.K
| | - Simon-Peter Williams
- †Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1GA, U.K
| | - Alexandra M. Fulton
- †Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1GA, U.K
| | - Anthony W. Parker
- *Central Laser Facility, Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire OX11 0QX, U.K
| | - Kevin M. Brindle
- †Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1GA, U.K
- To whom correspondence should be addressed (email )
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44
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Bisby RH, Botchway SW, Dad S, Parker AW. Single- and multi-photon excited fluorescence from serotonin complexed with beta-cyclodextrin. Photochem Photobiol Sci 2006; 5:122-5. [PMID: 16395437 PMCID: PMC1934424 DOI: 10.1039/b508602g] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2005] [Accepted: 10/04/2005] [Indexed: 11/21/2022]
Abstract
The fluorescence of serotonin on binding with beta-cyclodextrin has been studied using both steady state and time-resolved methods. Steady state fluorescence intensity of serotonin at 340 nm showed approximately 30% increase in intensity on binding with K(A) approximately 60 dm(3) mol(-1) and the fluorescence lifetimes showed a corresponding increase. In contrast, the characteristic green fluorescence ('hyperluminescence') of serotonin observed upon multiphoton near-infrared excitation with sub-picosecond pulses was resolved into two lifetime components assigned to free and bound serotonin. The results are of interest in relation to selective imaging and detection of serotonin using the unusual hyperluminescence emission and in respect to recent determinations of serotonin by capillary electrophoresis in the presence of cyclodextrin. The results also suggest that hyperluminescence occurs from multiphoton excitation of a single isolated serotonin molecule.
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Affiliation(s)
- Roger H Bisby
- Biosciences Research Institute, University of Salford, Salford, UK.
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45
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Venanzi M, Valeri A, Palleschi A, Stella L, Moroder L, Formaggio F, Toniolo C, Pispisa B. Structural properties and photophysical behavior of conformationally constrained hexapeptides functionalized with a new fluorescent analog of tryptophan and a nitroxide radical quencher. Biopolymers 2005; 75:128-39. [PMID: 15356867 DOI: 10.1002/bip.20110] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The influence of the conformational properties on the photophysics of two de novo designed hexapeptides was studied by spectroscopic measurements (ir, NMR, steady-state, and time resolved fluorescence) and molecular mechanics calculations. The peptide sequences comprise two nonproteinogenic residues: a beta-(1-azulenyl)-L-alanine (Aal) residue, obtained by formally functionalizing the Ala side chain with the azulene chromophore, and a Calpha-tetrasubstituted alpha-amino acid (TOAC), incorporating a nitroxide group in a cycloalkyl moiety. Aal represents a new fluorescent, quasi-isosteric Trp analog and TOAC a stable radical species, frequently used as a paramagnetic probe in biochemical studies. The peptide chains differ in the sequence position of the two probes and are heavily based on Aib (alpha-aminoisobutyric acid) residues to generate conformationally restricted helical structures, as confirmed by both spectroscopic and computational results. The conformationally controlled, excited state interactions, determining the photophysical relaxation of the Aal*/TOAC pair, are also discussed.
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Affiliation(s)
- Mariano Venanzi
- Department of Chemical Sciences and Technologies, University of Tor Vergata, 00133 Rome, Italy.
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46
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Carić D, Tomisić V, Kveder M, Galić N, Pifat G, Magnus V, Soskić M. Absorption and fluorescence spectra of ring-substituted indole-3-acetic acids. Biophys Chem 2005; 111:247-57. [PMID: 15501568 DOI: 10.1016/j.bpc.2004.06.006] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2004] [Revised: 06/02/2004] [Accepted: 06/03/2004] [Indexed: 11/16/2022]
Abstract
The absorption and fluorescence spectra of indole-3-acetic acid (1), a plant growth regulator (auxin) and experimental cancer therapeutic, 29 ring-substituted derivatives and the 7-aza analogue (1H-pyrrolo[2,3b]pyridine-3-acetic acid) are compared. Two to four absorbance maxima in the 260-310-nm range are interpreted as overlapping vibronic lines of the 1La<--1A and 1Lb<--1A transitions. Two further maxima in the 200-230-nm region are assigned to the 1Ba<--1A and 1Bb<--1A transitions. 4- and 7-Fluoroindole-3-acetic acid exhibit blue shifts with respect to 1, most other derivatives show red shifts. All indole-3-acetic acids studied, with the exception of chloro-, bromo- and 4- or 7-fluoro-derivatives, fluoresce at 345-370 nm when excited at 275-280 nm. 7-Azaindole-3-acetic acid emits at 411 nm. The fluorescence quantum yield of 6-fluoroindole-3-acetic acid significantly exceeds that of 1 (0.3); the other derivatives have lower quantum yields. The plant-growth promoting activity of the ring-substituted indole-3-acetic acids studied correlates with the position of the 1Bb<--1A transition band.
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Affiliation(s)
- Dejana Carić
- Faculty of Agronomy, Svetosimunska cesta 25, 10000 Zagreb, Croatia
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47
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Liu T, Callis PR, Hesp BH, de Groot M, Buma WJ, Broos J. Ionization potentials of fluoroindoles and the origin of nonexponential tryptophan fluorescence decay in proteins. J Am Chem Soc 2005; 127:4104-13. [PMID: 15771548 DOI: 10.1021/ja043154d] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
This work reports an explanation for the unusual monoexponential fluorescence decay of 5-fluorotryptophan (5FTrp) in single-Trp mutant proteins [Broos, J.; Maddalena, F.; Hesp, B. H. J. Am. Chem. Soc. 2004, 126, 22-23] and substantially clarifies the origin of the ubiquitous nonexponential fluorescence decay of tryptophan in proteins. Our results strongly suggest that the extent of nonexponential fluorescence decay is governed primarily by the efficiency of electron transfer (ET) quenching by a nearby amide group in the peptide bond. Fluoro substitution increases the ionization potential (IP) of indole, thereby suppressing the ET rate, leading to a longer average lifetime and therefore a more homogeneous decay. We report experimental IPs for a number of substituted indoles including 5-fluoroindole, 5-fluoro-3-methylindole, and 6-fluoroindole, along with accurate ab initio calculations of the IPs for these and 20 related molecules. The results predict the IP of 5-fluorotryptophan to be 0.19 eV higher than that of tryptophan. 5-Fluoro substitution does not measurably alter the excitation-induced change in permanent dipole moment nor does it change the fluorescent state from 1La to 1Lb. In combination with electronic structure information this argues that the increased IP and the decreased excitation energy of the 1La state, together 0.3 eV, are solely responsible for the strong reduction of electron transfer quenching. 6-Fluoro substitution is predicted to increase the IP by a mere 0.09 eV. In agreement with our conclusions, the fluorescence decay curves of 6-fluorotryptophan-containing proteins are well fit using only two decay times compared to three required for Trp.
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Affiliation(s)
- Tiqing Liu
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, Montana 59717, USA
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48
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Budisa N, Pal PP. Designing novel spectral classes of proteins with a tryptophan-expanded genetic code. Biol Chem 2005; 385:893-904. [PMID: 15551863 DOI: 10.1515/bc.2004.117] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Fluorescence methods are now well-established and powerful tools to study biological macromolecules. The canonical amino acid tryptophan (Trp), encoded by a single UGG triplet, is the main reporter of intrinsic fluorescence properties of most natural proteins and peptides and is thus an attractive target for tailoring their spectral properties. Recent advances in research have provided substantial evidence that the natural protein translational machinery can be genetically reprogrammed to introduce a large number of non-coded (i.e. noncanonical) Trp analogues and surrogates into various proteins. Especially attractive targets for such an engineering approach are fluorescent proteins in which the chromophore is formed post-translationally from an amino acid sequence, like the green fluorescent protein from Aequorea victoria. With the currently available translationally active fluoro-, hydroxy-, amino-, halogen-, and chalcogen-containing Trp analogues and surrogates, the traditional methods for protein engineering and design can be supplemented or even fully replaced by these novel approaches. Future research will provide a further increase in the number of Trp-like amino acids that are available for redesign (by engineering of the genetic code) of native Trp residues and enable novel strategies to generate proteins with tailored spectral properties.
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Affiliation(s)
- Nediljko Budisa
- Max-Planck-Institut für Biochemie, Am Klopferspitz 18A, D-82152 Martinsried, Germany.
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49
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Budisa N. Prolegomena zum experimentellen Engineering des genetischen Codes durch Erweiterung seines Aminosäurerepertoires. Angew Chem Int Ed Engl 2004. [DOI: 10.1002/ange.200300646] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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50
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Budisa N. Prolegomena to Future Experimental Efforts on Genetic Code Engineering by Expanding Its Amino Acid Repertoire. Angew Chem Int Ed Engl 2004; 43:6426-63. [PMID: 15578784 DOI: 10.1002/anie.200300646] [Citation(s) in RCA: 208] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Protein synthesis and its relation to the genetic code was for a long time a central issue in biology. Rapid experimental progress throughout the past decade, crowned with the recently elucidated ribosomal structures, provided an almost complete description of this process. In addition important experiments provided solid evidence that the natural protein translation machinery can be reprogrammed to encode genetically a vast number of non-coded (i.e. noncanonical) amino acids. Indeed, in the set of 20 canonical amino acids as prescribed by the universal genetic code, many desirable functionalities, such as halogeno, keto, cyano, azido, nitroso, nitro, and silyl groups, as well as C=C or C[triple bond]C bonds, are absent. The ability to encode genetically such chemical diversity will enable us to reprogram living cells, such as bacteria, to express tailor-made proteins exhibiting functional diversity. Accordingly, genetic code engineering has developed into an exciting emerging research field at the interface of biology, chemistry, and physics.
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Affiliation(s)
- Nediljko Budisa
- Max-Planck-Institut für Biochemie, Junior Research Group "Moleculare Biotechnologie", Am Klopferspitz 18a, 82152 Martinsried bei München, Germany.
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