1
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Kılıç M, Ensing B. Redox Properties of Flavin in BLUF and LOV Photoreceptor Proteins from Hybrid QM/MM Molecular Dynamics Simulation. J Phys Chem B 2024; 128:3069-3080. [PMID: 38518376 DOI: 10.1021/acs.jpcb.3c06245] [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: 03/24/2024]
Abstract
Flavins play an important role in many oxidation and reduction processes in biological systems. For example, flavin adenine dinucleotide (FAD) and flavin mononucleotide (FMN) are common cofactors found in enzymatic proteins that use the special redox properties of these flavin molecules for their catalytic or photoactive functions. The redox potential of the flavin is strongly affected by its (protein) environment; however, the underlying molecular interactions of this effect are still unknown. Using hybrid quantum mechanics/molecular mechanics (QM/MM) simulation techniques, we have studied the redox properties of flavin in the gas phase, aqueous solution, and two different protein environments, in particular, a BLUF and a LOV photoreceptor domain. By mapping the changes in electrostatic potential and solvent structure, we gain insight into how specific polarization of the flavin by its environment tunes the reduction potential. We find also that accurate calculation of the reduction potentials of these systems by using the hybrid QM/MM approach is hampered by a too limited sampling of the counterion configurations and by artifacts at the QM/MM boundary. We make suggestions for how these issues can be overcome.
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Affiliation(s)
- Murat Kılıç
- Van't Hoff Institute for Molecular Sciences, University of Amsterdam, Park 904, Amsterdam 1098 XH, The Netherlands
| | - Bernd Ensing
- Van't Hoff Institute for Molecular Sciences, University of Amsterdam, Park 904, Amsterdam 1098 XH, The Netherlands
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2
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Noji T, Tamura H, Ishikita H, Saito K. Difference in the Charge-Separation Energetics between Distinct Conformers in the PixD Photoreceptor. J Phys Chem B 2023; 127:10351-10359. [PMID: 38014591 DOI: 10.1021/acs.jpcb.3c06483] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2023]
Abstract
Blue light using flavin (BLUF) domain proteins are photoreceptors in various organisms. The PixD BLUF domain can adopt two conformations, W91out and W91in, with Trp91 either proximal or distal to flavin (FMN). Using a quantum mechanical/molecular mechanical/polarizable continuum model approach, the energetics of charge-separated and biradical states in the two conformations were investigated. In the W91out conformation, the charge-separated state (FMN•-) is more stable than the photoexcited state (FMN*), whereas it is less stable due to an electrostatic repulsive interaction with the Ser28 side chain in the W91in conformation. This leads to a lower activation energy for the charge separation in the W91out conformation, resulting in a faster charge separation compared to that in the W91in conformation. In the W91out conformation, the radical state (FMNH•) is more stable than FMN•- and forms from FMN•-, leading to reorientation of the Gln50 side chain adjacent to FMN and formation of a hydrogen bond between Gln50 and FMN. Subsequently, a signaling state forms through charge recombination. In contrast, in the W91in conformation, FMN•- cannot proceed further, returning to the dark-adapted state, as FMNH• is less stable. Thus, formation of the signaling state exclusively occurs in the W91out conformation.
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Affiliation(s)
- Tomoyasu Noji
- Research Center for Advanced Science and Technology, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8904, Japan
- Department of Applied Chemistry, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8654, Japan
| | - Hiroyuki Tamura
- Research Center for Advanced Science and Technology, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8904, Japan
- Department of Applied Chemistry, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8654, Japan
| | - Hiroshi Ishikita
- Research Center for Advanced Science and Technology, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8904, Japan
- Department of Applied Chemistry, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8654, Japan
| | - Keisuke Saito
- Research Center for Advanced Science and Technology, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8904, Japan
- Department of Applied Chemistry, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8654, Japan
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3
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Raics K, Pirisi K, Zhuang B, Fekete Z, Kis-Bicskei N, Pecsi I, Ujfalusi KP, Telek E, Li Y, Collado JT, Tonge PJ, Meech SR, Vos MH, Bodis E, Lukacs A. Photocycle alteration and increased enzymatic activity in genetically modified photoactivated adenylate cyclase OaPAC. J Biol Chem 2023; 299:105056. [PMID: 37468104 PMCID: PMC10448171 DOI: 10.1016/j.jbc.2023.105056] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2023] [Revised: 06/30/2023] [Accepted: 07/11/2023] [Indexed: 07/21/2023] Open
Abstract
Photoactivated adenylate cyclases (PACs) are light activated enzymes that combine blue light sensing capacity with the ability to convert ATP to cAMP and pyrophosphate (PPi) in a light-dependent manner. In most of the known PACs blue light regulation is provided by a blue light sensing domain using flavin which undergoes a structural reorganization after blue-light absorption. This minor structural change then is translated toward the C-terminal of the protein, inducing a larger conformational change that results in the ATP conversion to cAMP. As cAMP is a key second messenger in numerous signal transduction pathways regulating various cellular functions, PACs are of great interest in optogenetic studies. The optimal optogenetic device must be "silent" in the dark and highly responsive upon light illumination. PAC from Oscillatoria acuminata is a very good candidate as its basal activity is very small in the dark and the conversion rates increase 20-fold upon light illumination. We studied the effect of replacing D67 to N, in the blue light using flavin domain. This mutation was found to accelerate the primary electron transfer process in the photosensing domain of the protein, as has been predicted. Furthermore, it resulted in a longer lived signaling state, which was formed with a lower quantum yield. Our studies show that the overall effects of the D67N mutation lead to a slightly higher conversion of ATP to cAMP, which points in the direction that by fine tuning the kinetic properties more responsive PACs and optogenetic devices can be generated.
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Affiliation(s)
- Katalin Raics
- Department of Biophysics, Medical School, University of Pecs, Pecs, Hungary
| | - Katalin Pirisi
- Department of Biophysics, Medical School, University of Pecs, Pecs, Hungary
| | - Bo Zhuang
- Laboratoire d'Optique et Biosciences, Ecole Polytechnique, Palaiseau, France
| | - Zsuzsanna Fekete
- Department of Biophysics, Medical School, University of Pecs, Pecs, Hungary
| | | | - Ildiko Pecsi
- Department of Biophysics, Medical School, University of Pecs, Pecs, Hungary
| | | | - Elek Telek
- Department of Biophysics, Medical School, University of Pecs, Pecs, Hungary
| | - Yin Li
- Department of Physics, School of Physics and Materials Science, Nanchang University, Nanchang City, China
| | | | - Peter J Tonge
- Department of Chemistry, Stony Brook University, New York, USA
| | | | - Marten H Vos
- Laboratoire d'Optique et Biosciences, Ecole Polytechnique, Palaiseau, France
| | - Emoke Bodis
- Department of Biophysics, Medical School, University of Pecs, Pecs, Hungary.
| | - Andras Lukacs
- Department of Biophysics, Medical School, University of Pecs, Pecs, Hungary.
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4
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Nakasone Y, Terazima M. Time-resolved diffusion reveals photoreactions of BLUF proteins with similar functional domains. Photochem Photobiol Sci 2022; 21:493-507. [PMID: 35391638 DOI: 10.1007/s43630-022-00214-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2022] [Accepted: 03/21/2022] [Indexed: 11/30/2022]
Abstract
BLUF (blue light sensor using flavin) proteins are the blue light receptors that consist of flavin-binding BLUF domains and functional domains. Upon blue light excitation, the hydrogen bond network around the flavin chromophore changes, and the absorption spectrum in the visible region shifts to red. Light signal received in the BLUF domain is intramolecularly or intermolecularly transmitted to the functional region. In this review, the reactions of three BLUF proteins with similar EAL functional groups within the protein (BlrP1, and YcgF), or with a separated target protein (PapB) are described using time-resolved diffusion technique. The diffusion coefficients (D) of the BLUF domains did not significantly change upon photoexcitation, whereas those of the full-length proteins BlrP1 and YcgF and the PapB-PapA system significantly decreased. The changes in D should be due to diffusion-sensitive conformational changes (DSCC) that alter the friction of diffusion. The time constants of the major D changes of BlrP1 and PapB-PapA were similar (~ 20 ms), although the magnitude of the friction change depended on the proteins. Similarities and differences among the reactions of these proteins were clarified from the viewpoint of DSCC.
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Affiliation(s)
- Yusuke Nakasone
- Department of Chemistry, Graduate School of Science, Kyoto University, Kyoto, 606-8502, Japan
| | - Masahide Terazima
- Department of Chemistry, Graduate School of Science, Kyoto University, Kyoto, 606-8502, Japan.
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5
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Abstract
Light activated proteins are at the heart of photobiology and optogenetics, so there is wide interest in understanding the mechanisms coupling optical excitation to protein function. In addition, such light activated proteins provide unique insights into the real-time dynamics of protein function. Using pump-probe spectroscopy, the function of a photoactive protein can be initiated by a sub-100 fs pulse of light, allowing subsequent protein dynamics to be probed from femtoseconds to milliseconds and beyond. Among the most interesting photoactive proteins are the blue light using flavin (BLUF) domain proteins, which regulate the response to light of a wide range of bacterial and some euglenoid processes. The photosensing mechanism of BLUF domains has long been a subject of debate. In contrast to other photoactive proteins, the electronic and nuclear structure of the chromophore (flavin) is the same in dark- and light-adapted states. Thus, the driving force for photoactivity is unclear.To address this question requires real-time observation of both chromophore excited state processes and their effect on the structure and dynamics of the surrounding protein matrix. In this Account we describe how time-resolved infrared (IR) experiments, coupled with chemical biology, provide important new insights into the signaling mechanism of BLUF domains. IR measurements are sensitive to changes in both chromophore electronic structure and protein hydrogen bonding interactions. These contributions are resolved by isotope labeling of the chromophore and protein separately. Further, a degree of control over BLUF photochemistry is achieved through mutagenesis, while unnatural amino acid substitution allows us to both fine-tune the photochemistry and time resolve protein dynamics with spatial resolution.Ultrafast studies of BLUF domains reveal non-single-exponential relaxation of the flavin excited state. That relaxation leads within one nanosecond to the original flavin ground state bound in a modified hydrogen-bonding network, as seen in transient and steady-state IR spectroscopy. The change in H-bond configuration arises from formation of an unusual enol (imine) form of a critical glutamine residue. The dynamics observed, complemented by quantum mechanical calculations, suggest a unique sequential electron then double proton transfer reaction as the driving force, followed by rapid reorganization in the binding site and charge recombination. Importantly, studies of several BLUF domains reveal an unexpected diversity in their dynamics, although the underlying structure appears highly conserved. It is suggested that this diversity reflects structural dynamics in the ground state at standard temperature, leading to a distribution of structures and photochemical outcomes. Time resolved IR measurements were extended to the millisecond regime for one BLUF domain, revealing signaling state formation on the microsecond time scale. The mechanism involves reorganization of a β-sheet connected to the chromophore binding pocket via a tryptophan residue. The potential of site-specific labeling amino acids with IR labels as a tool for probing protein structural dynamics was demonstrated.In summary, time-resolved IR studies of BLUF domains (along with related studies at visible wavelengths and quantum and molecular dynamics calculations) have resolved the photoactivation mechanism and real-time dynamics of signaling state formation. These measurements provide new insights into protein structural dynamics and will be important in optimizing the potential of BLUF domains in optobiology.
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Affiliation(s)
- Andras Lukacs
- Department of Biophysics, Medical School, University of Pécs, Szigeti str 12, 7624 Pécs, Hungary
| | - Peter J. Tonge
- Department of Chemistry, Stony Brook University, 100 Nicolls Road, Stony Brook, New York 11794-3400, United States
| | - Stephen R. Meech
- School of Chemistry, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, U.K
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Fujisawa T, Masuda S, Takeuchi S, Tahara T. Femtosecond Time-Resolved Absorption Study of Signaling State of a BLUF Protein PixD from the Cyanobacterium Synechocystis: Hydrogen-Bond Rearrangement Completes during Forward Proton-Coupled Electron Transfer. J Phys Chem B 2021; 125:12154-12165. [PMID: 34726926 DOI: 10.1021/acs.jpcb.1c05957] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Femtosecond time-resolved absorption measurements were carried out for the dark and signaling states of a BLUF (Blue Light Using FAD) protein, PixD, from the cyanobacterium Synechocystis. When the dark state was excited, FAD semiquinone radical (FADH•) was produced from the S1 state, and FADH• led to the signaling state. On the other hand, photoexcitation of the signaling state generated FADH• and FAD anion radical (FAD•-), and they decayed back to the original signaling state. In both cases, FADH• was formed and decayed with a proton-coupled electron transfer (PCET) via the hydrogen-bond network that involves FAD, Gln50, and Tyr8, and hence the kinetics of FADH• directly reflects the hydrogen-bond structure in the FAD-binding sites. It was found that the formation rate of FADH• was significantly different between the dark and signaling states, whereas the decay rate was the same. This indicates that the hydrogen-bond network of FAD-Gln50-Tyr8 in the dark and signaling states is initially different but it becomes indistinguishable after FADH• is formed, implying that the FAD-Gln50-Tyr8 hydrogen-bond network is rearranged during the PCET to generate FADH•. The present results best agree with the model in which the Gln tautomerizes without rotation in the signaling-state formation.
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Affiliation(s)
- Tomotsumi Fujisawa
- Molecular Spectroscopy Laboratory, RIKEN, 2-1 Hirosawa, Wako 351-0198, Japan
| | - Shinji Masuda
- Department of Life Science and Technology, Tokyo Institute of Technology, Yokohama 226-8501, Japan
| | - Satoshi Takeuchi
- Molecular Spectroscopy Laboratory, RIKEN, 2-1 Hirosawa, Wako 351-0198, Japan.,Ultrafast Spectroscopy Research Team, RIKEN Center for Advanced Photonics (RAP), RIKEN, 2-1 Hirosawa, Wako 351-0198, Japan
| | - Tahei Tahara
- Molecular Spectroscopy Laboratory, RIKEN, 2-1 Hirosawa, Wako 351-0198, Japan.,Ultrafast Spectroscopy Research Team, RIKEN Center for Advanced Photonics (RAP), RIKEN, 2-1 Hirosawa, Wako 351-0198, Japan
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7
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Hashem S, Macaluso V, Nottoli M, Lipparini F, Cupellini L, Mennucci B. From crystallographic data to the solution structure of photoreceptors: the case of the AppA BLUF domain. Chem Sci 2021; 12:13331-13342. [PMID: 34777752 PMCID: PMC8528011 DOI: 10.1039/d1sc03000k] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2021] [Accepted: 09/01/2021] [Indexed: 12/28/2022] Open
Abstract
Photoreceptor proteins bind a chromophore, which, upon light absorption, modifies its geometry or its interactions with the protein, finally inducing the structural change needed to switch the protein from an inactive to an active or signaling state. In the Blue Light-Using Flavin (BLUF) family of photoreceptors, the chromophore is a flavin and the changes have been connected with a rearrangement of the hydrogen bond network around it on the basis of spectroscopic changes measured for the dark-to-light conversion. However, the exact conformational change triggered by the photoexcitation is still elusive mainly because a clear consensus on the identity not only of the light activated state but also of the dark one has not been achieved. Here, we present an integrated investigation that combines microsecond MD simulations starting from the two conflicting crystal structures available for the AppA BLUF domain with calculations of NMR, IR and UV-Vis spectra using a polarizable QM/MM approach. Thanks to such a combined analysis of the three different spectroscopic responses, a robust characterization of the structure of the dark state in solution is given together with the uncovering of important flaws of the most popular molecular mechanisms present in the literature for the dark-to-light activation.
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Affiliation(s)
- Shaima Hashem
- Dipartimento di Chimica e Chimica Industriale, Università di Pisa Via G. Moruzzi 13 56124 Pisa Italy
| | - Veronica Macaluso
- Dipartimento di Chimica e Chimica Industriale, Università di Pisa Via G. Moruzzi 13 56124 Pisa Italy
| | - Michele Nottoli
- Dipartimento di Chimica e Chimica Industriale, Università di Pisa Via G. Moruzzi 13 56124 Pisa Italy
| | - Filippo Lipparini
- Dipartimento di Chimica e Chimica Industriale, Università di Pisa Via G. Moruzzi 13 56124 Pisa Italy
| | - Lorenzo Cupellini
- Dipartimento di Chimica e Chimica Industriale, Università di Pisa Via G. Moruzzi 13 56124 Pisa Italy
| | - Benedetta Mennucci
- Dipartimento di Chimica e Chimica Industriale, Università di Pisa Via G. Moruzzi 13 56124 Pisa Italy
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8
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Green D, Roy P, Hall CR, Iuliano JN, Jones GA, Lukacs A, Tonge PJ, Meech SR. Excited State Resonance Raman of Flavin Mononucleotide: Comparison of Theory and Experiment. J Phys Chem A 2021; 125:6171-6179. [PMID: 34240863 DOI: 10.1021/acs.jpca.1c04063] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Blue light absorbing flavoproteins play important roles in a variety of photobiological processes. Consequently, there have been numerous investigations of their excited state structure and dynamics, in particular by time-resolved vibrational spectroscopy. The isoalloxazine chromophore of the flavoprotein cofactors has been studied in detail by time-resolved Raman, lending it a benchmark status for mode assignments in excited electronic states of large molecules. However, detailed comparisons of calculated and measured spectra have proven challenging, as there are many more modes calculated than are observed, and the role of resonance enhancement is difficult to characterize in excited electronic states. Here we employ a recently developed approach due to Elles and co-workers ( J. Phys. Chem. A 2018, 122, 8308-8319) for the calculation of resonance-enhanced Raman spectra of excited states and apply it to the lowest singlet and triplet excited states of the isoalloxazine chromophore. There is generally good agreement between calculated and observed enhancements, which allows assignment of vibrational bands of the flavoprotein cofactors to be refined. However, some prominently enhanced bands are found to be absent from the calculations, suggesting the need for further development of the theory.
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Affiliation(s)
- Dale Green
- School of Chemistry, University of East Anglia, Norwich NR4 7TJ, U.K
| | - Palas Roy
- School of Chemistry, University of East Anglia, Norwich NR4 7TJ, U.K
| | | | - James N Iuliano
- Department of Chemistry, Stony Brook University, Stony Brook, New York 11794-3400, United States
| | - Garth A Jones
- School of Chemistry, University of East Anglia, Norwich NR4 7TJ, U.K
| | - Andras Lukacs
- Department of Biophysics, Medical School, University of Pecs, Szigeti ut 12, 7624 Pecs, Hungary
| | - Peter J Tonge
- Department of Chemistry, Stony Brook University, Stony Brook, New York 11794-3400, United States
| | - Stephen R Meech
- School of Chemistry, University of East Anglia, Norwich NR4 7TJ, U.K
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9
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Formation of an unusual glutamine tautomer in a blue light using flavin photocycle characterizes the light-adapted state. Proc Natl Acad Sci U S A 2020; 117:26626-26632. [PMID: 33037153 DOI: 10.1073/pnas.2016719117] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
Blue light using flavin (BLUF) photoreceptor proteins are critical for many light-activated biological processes and are promising candidates for optogenetics because of their modular nature and long-range signaling capabilities. Although the photocycle of the Slr1694 BLUF domain has been characterized experimentally, the identity of the light-adapted state following photoexcitation of the bound flavin remains elusive. Herein hybrid quantum mechanical/molecular mechanical (QM/MM) molecular dynamics simulations of this photocycle provide a nonequilibrium dynamical picture of a possible mechanism for the formation of the light-adapted state. Photoexcitation of the flavin induces a forward proton-coupled electron transfer (PCET) process that leads to the formation of an imidic acid tautomer of Gln50. The calculations herein show that the subsequent rotation of Gln50 allows a reverse PCET process that retains this tautomeric form. In the resulting purported light-adapted state, the glutamine tautomer forms a hydrogen bond with the flavin carbonyl group. Additional ensemble-averaged QM/MM calculations of the dark-adapted and purported light-adapted states demonstrate that the light-adapted state with the imidic acid glutamine tautomer reproduces the experimentally observed spectroscopic signatures. Specifically, the calculations reproduce the red shifts in the flavin electronic absorption and carbonyl stretch infrared spectra in the light-adapted state. Further hydrogen-bonding analyses suggest the formation of hydrogen-bonding interactions between the flavin and Arg65 in the light-adapted state, providing a plausible explanation for the experimental observation of faster photoinduced PCET in this state. These characteristics of the light-adapted state may also be essential for the long-range signaling capabilities of this photoreceptor protein.
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10
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Karadi K, Kapetanaki SM, Raics K, Pecsi I, Kapronczai R, Fekete Z, Iuliano JN, Collado JT, Gil AA, Orban J, Nyitrai M, Greetham GM, Vos MH, Tonge PJ, Meech SR, Lukacs A. Functional dynamics of a single tryptophan residue in a BLUF protein revealed by fluorescence spectroscopy. Sci Rep 2020; 10:2061. [PMID: 32029866 PMCID: PMC7005313 DOI: 10.1038/s41598-020-59073-5] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2019] [Accepted: 01/23/2020] [Indexed: 11/17/2022] Open
Abstract
Blue Light Using Flavin (BLUF) domains are increasingly being adopted for use in optogenetic constructs. Despite this, much remains to be resolved on the mechanism of their activation. The advent of unnatural amino acid mutagenesis opens up a new toolbox for the study of protein structural dynamics. The tryptophan analogue, 7-aza-Trp (7AW) was incorporated in the BLUF domain of the Activation of Photopigment and pucA (AppA) photoreceptor in order to investigate the functional dynamics of the crucial W104 residue during photoactivation of the protein. The 7-aza modification to Trp makes selective excitation possible using 310 nm excitation and 380 nm emission, separating the signals of interest from other Trp and Tyr residues. We used Förster energy transfer (FRET) between 7AW and the flavin to estimate the distance between Trp and flavin in both the light- and dark-adapted states in solution. Nanosecond fluorescence anisotropy decay and picosecond fluorescence lifetime measurements for the flavin revealed a rather dynamic picture for the tryptophan residue. In the dark-adapted state, the major population of W104 is pointing away from the flavin and can move freely, in contrast to previous results reported in the literature. Upon blue-light excitation, the dominant tryptophan population is reorganized, moves closer to the flavin occupying a rigidly bound state participating in the hydrogen-bond network around the flavin molecule.
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Affiliation(s)
- Kristof Karadi
- Department of Biophysics, Medical School, University of Pécs, 7624, Pécs, Hungary.,Szentagothai Research Center, University of Pécs, 7624, Pécs, Hungary
| | - Sofia M Kapetanaki
- Department of Biophysics, Medical School, University of Pécs, 7624, Pécs, Hungary.,Szentagothai Research Center, University of Pécs, 7624, Pécs, Hungary
| | - Katalin Raics
- Department of Biophysics, Medical School, University of Pécs, 7624, Pécs, Hungary
| | - Ildiko Pecsi
- Department of Biophysics, Medical School, University of Pécs, 7624, Pécs, Hungary
| | - Robert Kapronczai
- Department of Biophysics, Medical School, University of Pécs, 7624, Pécs, Hungary
| | - Zsuzsanna Fekete
- Department of Biophysics, Medical School, University of Pécs, 7624, Pécs, Hungary
| | - James N Iuliano
- Department of Chemistry, Stony Brook University, Stony Brook, NY, 11794-3400, USA
| | | | - Agnieszka A Gil
- Department of Chemistry, Stony Brook University, Stony Brook, NY, 11794-3400, USA
| | - Jozsef Orban
- Department of Biophysics, Medical School, University of Pécs, 7624, Pécs, Hungary
| | - Miklos Nyitrai
- Department of Biophysics, Medical School, University of Pécs, 7624, Pécs, Hungary.,Szentagothai Research Center, University of Pécs, 7624, Pécs, Hungary
| | - Greg M Greetham
- Central Laser Facility, Harwell Science and Innovation Campus, Didcot, Oxfordshire, UK
| | - Marten H Vos
- LOB, CNRS, INSERM, Ecole Polytechnique, Institut Polytechnique de Paris, 91128, Palaiseau, Cedex, France
| | - Peter J Tonge
- Department of Chemistry, Stony Brook University, Stony Brook, NY, 11794-3400, USA
| | - Stephen R Meech
- School of Chemistry, University of East Anglia, Norwich, NR4 7TJ, UK
| | - Andras Lukacs
- Department of Biophysics, Medical School, University of Pécs, 7624, Pécs, Hungary. .,Szentagothai Research Center, University of Pécs, 7624, Pécs, Hungary.
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11
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Yee EF, Dzikovski B, Crane BR. Tuning Radical Relay Residues by Proton Management Rescues Protein Electron Hopping. J Am Chem Soc 2019; 141:17571-17587. [PMID: 31603693 DOI: 10.1021/jacs.9b05715] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Transient tyrosine and tryptophan radicals play key roles in the electron transfer (ET) reactions of photosystem (PS) II, ribonucleotide reductase (RNR), photolyase, and many other proteins. However, Tyr and Trp are not functionally interchangeable, and the factors controlling their reactivity are often unclear. Cytochrome c peroxidase (CcP) employs a Trp191•+ radical to oxidize reduced cytochrome c (Cc). Although a Tyr191 replacement also forms a stable radical, it does not support rapid ET from Cc. Here we probe the redox properties of CcP Y191 by non-natural amino acid substitution, altering the ET driving force and manipulating the protic environment of Y191. Higher potential fluorotyrosine residues increase ET rates marginally, but only addition of a hydrogen bond donor to Tyr191• (via Leu232His or Glu) substantially alters activity by increasing the ET rate by nearly 30-fold. ESR and ESEEM spectroscopies, crystallography, and pH-dependent ET kinetics provide strong evidence for hydrogen bond formation to Y191• by His232/Glu232. Rate measurements and rapid freeze quench ESR spectroscopy further reveal differences in radical propagation and Cc oxidation that support an increased Y191• formal potential of ∼200 mV in the presence of E232. Hence, Y191 inactivity results from a potential drop owing to Y191•+ deprotonation. Incorporation of a well-positioned base to accept and donate back a hydrogen bond upshifts the Tyr• potential into a range where it can effectively oxidize Cc. These findings have implications for the YZ/YD radicals of PS II, hole-hopping in RNR and cryptochrome, and engineering proteins for long-range ET reactions.
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Affiliation(s)
- Estella F Yee
- Department of Chemistry and Chemical Biology , Cornell University , Ithaca , New York 14853 , United States
| | - Boris Dzikovski
- Department of Chemistry and Chemical Biology , Cornell University , Ithaca , New York 14853 , United States.,National Biomedical Center for Advanced ESR Technologies (ACERT) , Cornell University , Ithaca , New York 14850 , United States
| | - Brian R Crane
- Department of Chemistry and Chemical Biology , Cornell University , Ithaca , New York 14853 , United States
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12
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Hall CR, Tolentino Collado J, Iuliano JN, Gil AA, Adamczyk K, Lukacs A, Greetham GM, Sazanovich I, Tonge PJ, Meech SR. Site-Specific Protein Dynamics Probed by Ultrafast Infrared Spectroscopy of a Noncanonical Amino Acid. J Phys Chem B 2019; 123:9592-9597. [DOI: 10.1021/acs.jpcb.9b09425] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
| | | | - James N. Iuliano
- Department of Chemistry, Stony Brook University, Stony Brook, New York 11794-3400, United States
| | - Agnieszka A. Gil
- Department of Chemistry, Stony Brook University, Stony Brook, New York 11794-3400, United States
| | - Katrin Adamczyk
- School of Chemistry, University of East Anglia, Norwich NR4 7TJ, U.K
| | - Andras Lukacs
- Department of Biophysics, Medical School, University of Pecs, Szigeti ut 12, 7624 Pecs, Hungary
| | - Gregory M. Greetham
- Central Laser Facility, Research Complex at Harwell, Harwell Science and Innovation Campus, Didcot, Oxon OX11 0QX, U.K
| | - Igor Sazanovich
- Central Laser Facility, Research Complex at Harwell, Harwell Science and Innovation Campus, Didcot, Oxon OX11 0QX, U.K
| | - Peter J. Tonge
- Department of Chemistry, Stony Brook University, Stony Brook, New York 11794-3400, United States
| | - Stephen R. Meech
- School of Chemistry, University of East Anglia, Norwich NR4 7TJ, U.K
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13
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Kabir MP, Orozco-Gonzalez Y, Gozem S. Electronic spectra of flavin in different redox and protonation states: a computational perspective on the effect of the electrostatic environment. Phys Chem Chem Phys 2019; 21:16526-16537. [DOI: 10.1039/c9cp02230a] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
This study discusses how UV/vis absorption spectra of flavin in different redox and protonation states are shifted by the nearby electrostatic microenvironment.
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Affiliation(s)
| | | | - Samer Gozem
- Department of Chemistry
- Georgia State University
- Atlanta
- USA
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14
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Sayfutyarova ER, Goings JJ, Hammes-Schiffer S. Electron-Coupled Double Proton Transfer in the Slr1694 BLUF Photoreceptor: A Multireference Electronic Structure Study. J Phys Chem B 2018; 123:439-447. [DOI: 10.1021/acs.jpcb.8b10973] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Affiliation(s)
- Elvira R. Sayfutyarova
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06520, United States
| | - Joshua J. Goings
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06520, United States
| | - Sharon Hammes-Schiffer
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06520, United States
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15
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Xu Y, Bao P, Song K, Shi Q. Theoretical study of proton coupled electron transfer reaction in the light state of the AppA BLUF photoreceptor. J Comput Chem 2018; 40:1005-1014. [PMID: 30341953 DOI: 10.1002/jcc.25561] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2018] [Revised: 07/01/2018] [Accepted: 07/24/2018] [Indexed: 11/10/2022]
Abstract
The BLUF (blue light sensor using flavin adenine dinucleotide) domain is widely studied as a prototype for proton coupled electron transfer (PCET) reactions in biological systems. In this work, the photo-induced concerted PCET reaction from the light state of the AppA BLUF domain is investigated. To model the simultaneous transfer of two protons in the reaction, two-dimensional potential energy surfaces for the double proton transfer are first calculated for the locally excited and charge transfer states, which are then used to obtain the vibrational wave function overlaps and the vibrational energy levels. Contributions to the PCET rate constant from each pair of vibronic states are then analyzed using the theory based on the Fermi's golden rule. We show that, the recently proposed light state structure of the BLUF domain with a tautomerized Gln63 residue is consistent with the concerted transfer of one electron and two protons. It is also found that, thermal fluctuations of the protein structure, especially the proton donor-acceptor distances, play an important role in determining the PCET reaction rate. © 2018 Wiley Periodicals, Inc.
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Affiliation(s)
- Yang Xu
- Beijing National Laboratory for Molecular Sciences, State Key Laboratory for Structural Chemistry of Unstable and Stable Species, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Peng Bao
- Beijing National Laboratory for Molecular Sciences, State Key Laboratory for Structural Chemistry of Unstable and Stable Species, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Kai Song
- Beijing National Laboratory for Molecular Sciences, State Key Laboratory for Structural Chemistry of Unstable and Stable Species, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Qiang Shi
- Beijing National Laboratory for Molecular Sciences, State Key Laboratory for Structural Chemistry of Unstable and Stable Species, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing, China.,University of Chinese Academy of Sciences, Beijing, China
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16
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Goings JJ, Reinhardt CR, Hammes-Schiffer S. Propensity for Proton Relay and Electrostatic Impact of Protein Reorganization in Slr1694 BLUF Photoreceptor. J Am Chem Soc 2018; 140:15241-15251. [DOI: 10.1021/jacs.8b07456] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Affiliation(s)
- Joshua J. Goings
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06520, United States
| | - Clorice R. Reinhardt
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06520, United States
| | - Sharon Hammes-Schiffer
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06520, United States
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17
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Grigorenko BL, Khrenova MG, Nemukhin AV. Amide-imide tautomerization in the glutamine side chain in enzymatic and photochemical reactions in proteins. Phys Chem Chem Phys 2018; 20:23827-23836. [PMID: 30202846 DOI: 10.1039/c8cp04817g] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Amide-imide tautomerization presents a pervasive class of chemical transformations in organic chemistry of natural compounds. In this Perspective, we describe two distinctively different protein systems, in which the amide-imide tautomerization in the glutamine side chain takes place in enzymatic or photochemical reactions. First, hydrolysis of guanosine triphosphate (GTP) catalyzed by the Ras-GAP protein complex suggests the occurrence of the imide tautomer of glutamine in reaction intermediates. Second, photoexcitation of flavin-binding protein domains (BLUFs) initiates a chain of reactions in the chromophore-binding pocket, including amide-imide tautomerization of glutamine. Mechanisms of these reactions at the atomic level have been revealed in quantum mechanics/molecular mechanics (QM/MM) simulations. To reinforce conclusions on the critical role of amide-imide tautomerization of glutamine in these reactions we describe results of new quantum chemistry and QM/MM calculations for relevant molecular model systems. We reexamine results of the recent IR spectroscopy studies of BLUF domains, which provide experimental evidences of Gln tautomerization in proteins. We also propose to validate the glutamine-assisted mechanism of enzymatic GTP hydrolysis by using IR spectroscopy in a proper range of wavenumbers.
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Affiliation(s)
- Bella L Grigorenko
- Department of Chemistry, Lomonosov Moscow State University, Leninskie Gory 1/3, 119991 Moscow, Russian Federation.
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18
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Iwata T, Nagai T, Ito S, Osoegawa S, Iseki M, Watanabe M, Unno M, Kitagawa S, Kandori H. Hydrogen Bonding Environments in the Photocycle Process around the Flavin Chromophore of the AppA-BLUF domain. J Am Chem Soc 2018; 140:11982-11991. [DOI: 10.1021/jacs.8b05123] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Tatsuya Iwata
- Department of Life Science and Applied Chemistry, Nagoya Institute of Technology, Showa-ku, Nagoya 466-8555, Japan
- Department of Pharmaceutical Sciences, Toho University, Funabashi, Chiba 274-8510, Japan
| | - Takashi Nagai
- Department of Life Science and Applied Chemistry, Nagoya Institute of Technology, Showa-ku, Nagoya 466-8555, Japan
| | - Shota Ito
- Department of Life Science and Applied Chemistry, Nagoya Institute of Technology, Showa-ku, Nagoya 466-8555, Japan
| | - Shinsuke Osoegawa
- Department of Chemistry and Applied Chemistry, Graduate School of Science and Engineering, Saga University, Saga 840-8502, Japan
| | - Mineo Iseki
- Department of Pharmaceutical Sciences, Toho University, Funabashi, Chiba 274-8510, Japan
| | - Masakatsu Watanabe
- The Graduate School for the Creation of New Photonics Industries, Nishi-ku, Hamamatsu 431-1202, Japan
| | - Masashi Unno
- Department of Chemistry and Applied Chemistry, Graduate School of Science and Engineering, Saga University, Saga 840-8502, Japan
| | - Shinya Kitagawa
- Department of Life Science and Applied Chemistry, Nagoya Institute of Technology, Showa-ku, Nagoya 466-8555, Japan
| | - Hideki Kandori
- Department of Life Science and Applied Chemistry, Nagoya Institute of Technology, Showa-ku, Nagoya 466-8555, Japan
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19
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Fujisawa T, Masuda S. Light-induced chromophore and protein responses and mechanical signal transduction of BLUF proteins. Biophys Rev 2017; 10:327-337. [PMID: 29235080 PMCID: PMC5899715 DOI: 10.1007/s12551-017-0355-6] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2017] [Accepted: 11/15/2017] [Indexed: 11/26/2022] Open
Abstract
Photoreceptor proteins have been used to study how protein conformational changes are induced by alterations in their environments and how their signals are transmitted to downstream factors to dictate physiological responses. These proteins are attractive models because their signal transduction aspects and structural changes can be precisely regulated in vivo and in vitro based on light intensity. Among the known photoreceptors, members of the blue light–using flavin (BLUF) protein family have been well characterized with regard to how they control various light-dependent physiological responses in several microorganisms. Herein, we summarize our current understanding of their photoactivation and signal-transduction mechanisms. For signal transduction, we review recent studies concerning how the BLUF protein, PixD, transmits a light-induced signal to its downstream factor, PixE, to modulate phototaxis of the cyanobacterium Synechocystis sp. PCC6803.
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Affiliation(s)
- Tomotsumi Fujisawa
- Department of Chemistry, Graduate School of Science and Engineering, Saga University, Saga, 840-8502 Japan
| | - Shinji Masuda
- Center for Biological Resources & Informatics, Tokyo Institute of Technology, Yokohama, 226-8501 Japan
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20
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Gil AA, Laptenok SP, Iuliano JN, Lukacs A, Verma A, Hall CR, Yoon GE, Brust R, Greetham GM, Towrie M, French JB, Meech SR, Tonge PJ. Photoactivation of the BLUF Protein PixD Probed by the Site-Specific Incorporation of Fluorotyrosine Residues. J Am Chem Soc 2017; 139:14638-14648. [PMID: 28876066 DOI: 10.1021/jacs.7b07849] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The flavin chromophore in blue-light-using FAD (BLUF) photoreceptors is surrounded by a hydrogen bond network that senses and responds to changes in the electronic structure of the flavin on the ultrafast time scale. The hydrogen bond network includes a strictly conserved Tyr residue, and previously we explored the role of this residue, Y21, in the photoactivation mechanism of the BLUF protein AppABLUF by the introduction of fluorotyrosine (F-Tyr) analogues that modulated the pKa and reduction potential of Y21 by 3.5 pH units and 200 mV, respectively. Although little impact on the forward (dark- to light-adapted form) photoreaction was observed, the change in Y21 pKa led to a 4000-fold increase in the rate of dark-state recovery. In the present work we have extended these studies to the BLUF protein PixD, where, in contrast to AppABLUF, modulation in the Tyr (Y8) pKa has a profound impact on the forward photoreaction. In particular, a decrease in Y8 pKa by 2 or more pH units prevents formation of a stable light state, consistent with a photoactivation mechanism that involves proton transfer or proton-coupled electron transfer from Y8 to the electronically excited FAD. Conversely, the effect of pKa on the rate of dark recovery is markedly reduced in PixD. These observations highlight very significant differences between the photocycles of PixD and AppABLUF, despite their sharing highly conserved FAD binding architectures.
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Affiliation(s)
| | - Sergey P Laptenok
- School of Chemistry, University of East Anglia , Norwich Research Park, Norwich NR4 7TJ, U.K
| | | | - Andras Lukacs
- Department of Biophysics, Medical School, University of Pecs , Pecs H-7622, Hungary
| | - Anil Verma
- Central Laser Facility, Harwell Science and Innovation Campus , Didcot, Oxon OX11 0QX, U.K
| | - Christopher R Hall
- School of Chemistry, University of East Anglia , Norwich Research Park, Norwich NR4 7TJ, U.K
| | | | | | - Gregory M Greetham
- Central Laser Facility, Harwell Science and Innovation Campus , Didcot, Oxon OX11 0QX, U.K
| | - Michael Towrie
- Central Laser Facility, Harwell Science and Innovation Campus , Didcot, Oxon OX11 0QX, U.K
| | | | - Stephen R Meech
- School of Chemistry, University of East Anglia , Norwich Research Park, Norwich NR4 7TJ, U.K
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21
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Molecular mechanism of photoactivation of a light-regulated adenylate cyclase. Proc Natl Acad Sci U S A 2017; 114:8562-8567. [PMID: 28739908 DOI: 10.1073/pnas.1704391114] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The photoactivated adenylate cyclase (PAC) from the photosynthetic cyanobacterium Oscillatoria acuminata (OaPAC) detects light through a flavin chromophore within the N-terminal BLUF domain. BLUF domains have been found in a number of different light-activated proteins, but with different relative orientations. The two BLUF domains of OaPAC are found in close contact with each other, forming a coiled coil at their interface. Crystallization does not impede the activity switching of the enzyme, but flash cooling the crystals to cryogenic temperatures prevents the signature spectral changes that occur on photoactivation/deactivation. High-resolution crystallographic analysis of OaPAC in the fully activated state has been achieved by cryocooling the crystals immediately after light exposure. Comparison of the isomorphous light- and dark-state structures shows that the active site undergoes minimal changes, yet enzyme activity may increase up to 50-fold, depending on conditions. The OaPAC models will assist the development of simple, direct means to raise the cyclic AMP levels of living cells by light, and other tools for optogenetics.
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22
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Park SY, Tame JRH. Seeing the light with BLUF proteins. Biophys Rev 2017; 9:169-176. [PMID: 28510088 DOI: 10.1007/s12551-017-0258-6] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2017] [Accepted: 03/05/2017] [Indexed: 10/19/2022] Open
Abstract
First described about 15 years ago, BLUF (Blue Light Using Flavin) domains are light-triggered switches that control enzyme activity or gene expression in response to blue light, remaining activated for seconds or even minutes after stimulation. The conserved, ferredoxin-like fold holds a flavin chromophore that captures the light and somehow triggers downstream events. BLUF proteins are found in both prokaryotes and eukaryotes and have a variety of architectures and oligomeric forms, but the BLUF domain itself seems to have a well-preserved structure and mechanism that have been the focus of intense study for a number of years. Crystallographic and NMR structures of BLUF domains have been solved, but the conflicting models have led to considerable debate about the atomic details of photo-activation. Advanced spectroscopic and computational methods have been used to analyse the early events after photon absorption, but these too have led to widely differing conclusions. New structural models are improving our understanding of the details of the mechanism and may lead to novel tailor-made tools for optogenetics.
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Affiliation(s)
- Sam-Yong Park
- Drug Design Laboratory, Graduate School of Medical Life Science, Yokohama City University, 1-7-29 Suehiro, Tsurumi, Yokohama, 230-0045, Japan
| | - Jeremy R H Tame
- Drug Design Laboratory, Graduate School of Medical Life Science, Yokohama City University, 1-7-29 Suehiro, Tsurumi, Yokohama, 230-0045, Japan.
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23
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Role of active site conformational changes in photocycle activation of the AppA BLUF photoreceptor. Proc Natl Acad Sci U S A 2017; 114:1480-1485. [PMID: 28137837 DOI: 10.1073/pnas.1621393114] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Blue light using flavin adenine dinucleotide (BLUF) proteins are essential for the light regulation of a variety of physiologically important processes and serve as a prototype for photoinduced proton-coupled electron transfer (PCET). Free-energy simulations elucidate the active site conformations in the AppA (activation of photopigment and puc expression) BLUF domain before and following photoexcitation. The free-energy profile for interconversion between conformations with either Trp104 or Met106 closer to the flavin, denoted Trpin/Metout and Trpout/Metin, reveals that both conformations are sampled on the ground state, with the former thermodynamically favorable by ∼3 kcal/mol. These results are consistent with the experimental observation of both conformations. To analyze the proton relay from Tyr21 to the flavin via Gln63, the free-energy profiles for Gln63 rotation were calculated on the ground state, the locally excited state of the flavin, and the charge-transfer state associated with electron transfer from Tyr21 to the flavin. For the Trpin/Metout conformation, the hydrogen-bonding pattern conducive to the proton relay is not thermodynamically favorable on the ground state but becomes more favorable, corresponding to approximately half of the configurations sampled, on the locally excited state. The calculated energy gaps between the locally excited and charge-transfer states suggest that electron transfer from Tyr21 to the flavin is more facile for configurations conducive to proton transfer. When the active site conformation is not conducive to PCET from Tyr21, Trp104 can directly compete with Tyr21 for electron transfer to the flavin through a nonproductive pathway, impeding the signaling efficiency.
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24
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Udvarhelyi A, Olivucci M, Domratcheva T. Role of the Molecular Environment in Flavoprotein Color and Redox Tuning: QM Cluster versus QM/MM Modeling. J Chem Theory Comput 2016; 11:3878-94. [PMID: 26574469 DOI: 10.1021/acs.jctc.5b00197] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We investigate the origin of the excitation energy shifts induced by the apoprotein in the active site of the bacterial photoreceptor BLUF (Blue Light sensor Using Flavin adenine dinucleotide). In order to compute the vertical excitation energies of three low-lying electronic states, including two π-π* states of flavin (S1 and S2) and a π-π* tyrosine-flavin electron-transfer state (ET), with respect to the energy of the closed-shell ground state (S0), we prepared alternative quantum mechanical (QM) cluster and quantum mechanics/molecular mechanics (QM/MM) models. We found that the excitation energies computed with both types of models correlate with the magnitude of the charge transfer character of the excitation. Accordingly, we conclude that the small charge transfer character of the light absorbing S0-S1 transition and the substantial charge transfer character of the nonabsorbing but redox active S0-ET transition explain the small color changes but substantial redox tuning in BLUF and also in other flavoproteins. Further analysis showed that redox tuning is governed by the electrostatic interaction in the QM/MM model and transfer of charge between the active site and its environment in the QM cluster. Moreover, the wave function polarization of the QM subsystem by the MM subsystem influences the magnitude of the charge transfer, resulting in the QM/MM and QM excitation energies that are not entirely consistent.
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Affiliation(s)
- Anikó Udvarhelyi
- Department of Biomolecular Mechanisms, Max Planck Institute for Medical Research , Jahnstrasse 29, 69120 Heidelberg, Germany
| | - Massimo Olivucci
- Dipartimento di Biotecnologie, Chimica e Farmacia, via A. Moro 2, Universitá di Siena , I-53100 Siena, Italy.,Chemistry Department, Overman Hall, Bowling Green State University , Bowling Green, Ohio 67200, United States.,Institut de Physique et de Chimie des Materiaux de Strasbourg, Université de Strasbourg , Batiment 69, 23 Rue du Loess, 67200 Strasbourg, France
| | - Tatiana Domratcheva
- Department of Biomolecular Mechanisms, Max Planck Institute for Medical Research , Jahnstrasse 29, 69120 Heidelberg, Germany
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25
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Domratcheva T, Hartmann E, Schlichting I, Kottke T. Evidence for Tautomerisation of Glutamine in BLUF Blue Light Receptors by Vibrational Spectroscopy and Computational Chemistry. Sci Rep 2016; 6:22669. [PMID: 26947391 PMCID: PMC4780082 DOI: 10.1038/srep22669] [Citation(s) in RCA: 56] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2015] [Accepted: 02/16/2016] [Indexed: 02/02/2023] Open
Abstract
BLUF (blue light sensor using flavin) domains regulate the activity of various enzymatic effector domains in bacteria and euglenids. BLUF features a unique photoactivation through restructuring of the hydrogen-bonding network as opposed to a redox reaction or an isomerization of the chromophore. A conserved glutamine residue close to the flavin chromophore plays a central role in the light response, but the underlying modification is still unclear. We labelled this glutamine with (15)N in two representative BLUF domains and performed time-resolved infrared double difference spectroscopy. The assignment of the signals was conducted by extensive quantum chemical calculations on large models with 187 atoms reproducing the UV-vis and infrared signatures of BLUF photoactivation. In the dark state, the comparatively low frequency of 1,667 cm(-1) is assigned to the glutamine C=O accepting a hydrogen bond from tyrosine. In the light state, the signature of a tautomerised glutamine was extracted with the C=N stretch at ~1,691 cm(-1) exhibiting the characteristic strong downshift by (15)N labelling. Moreover, an indirect isotope effect on the flavin C4=O stretch was found. We conclude that photoactivation of the BLUF receptor does not only involve a rearrangement of hydrogen bonds but includes a change in covalent bonds of the protein.
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Affiliation(s)
- Tatiana Domratcheva
- Department of Biomolecular Mechanisms, Max Planck Institute for Medical Research, Jahnstraße 29, 69120, Heidelberg, Germany
| | - Elisabeth Hartmann
- Department of Biomolecular Mechanisms, Max Planck Institute for Medical Research, Jahnstraße 29, 69120, Heidelberg, Germany
| | - Ilme Schlichting
- Department of Biomolecular Mechanisms, Max Planck Institute for Medical Research, Jahnstraße 29, 69120, Heidelberg, Germany
| | - Tilman Kottke
- Physical and Biophysical Chemistry, Department of Chemistry, Bielefeld University, Universitäts straße 25, 33615 Bielefeld, Germany
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26
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Gil A, Haigney A, Laptenok SP, Brust R, Lukacs A, Iuliano J, Jeng J, Melief E, Zhao RK, Yoon E, Clark I, Towrie M, Greetham GM, Ng A, Truglio J, French J, Meech SR, Tonge PJ. Mechanism of the AppABLUF Photocycle Probed by Site-Specific Incorporation of Fluorotyrosine Residues: Effect of the Y21 pKa on the Forward and Reverse Ground-State Reactions. J Am Chem Soc 2016; 138:926-935. [PMID: 26708408 PMCID: PMC4830125 DOI: 10.1021/jacs.5b11115] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The transcriptional antirepressor AppA is a blue light using flavin (BLUF) photoreceptor that releases the transcriptional repressor PpsR upon photoexcitation. Light activation of AppA involves changes in a hydrogen-bonding network that surrounds the flavin chromophore on the nanosecond time scale, while the dark state of AppA is then recovered in a light-independent reaction with a dramatically longer half-life of 15 min. Residue Y21, a component of the hydrogen-bonding network, is known to be essential for photoactivity. Here, we directly explore the effect of the Y21 pKa on dark state recovery by replacing Y21 with fluorotyrosine analogues that increase the acidity of Y21 by 3.5 pH units. Ultrafast transient infrared measurements confirm that the structure of AppA is unperturbed by fluorotyrosine substitution, and that there is a small (3-fold) change in the photokinetics of the forward reaction over the fluorotyrosine series. However, reduction of 3.5 pH units in the pKa of Y21 increases the rate of dark state recovery by 4000-fold with a Brønsted coefficient of ∼ 1, indicating that the Y21 proton is completely transferred in the transition state leading from light to dark adapted AppA. A large solvent isotope effect of ∼ 6-8 is also observed on the rate of dark state recovery. These data establish that the acidity of Y21 is a crucial factor for stabilizing the light activated form of the protein, and have been used to propose a model for dark state recovery that will ultimately prove useful for tuning the properties of BLUF photosensors for optogenetic applications.
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Affiliation(s)
- Agnieszka Gil
- Department of Chemistry, Stony Brook University, Stony Brook, New York 11794-3400, USA
| | - Allison Haigney
- Department of Chemistry, Stony Brook University, Stony Brook, New York 11794-3400, USA
| | - Sergey P. Laptenok
- School of Chemistry, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK
| | - Richard Brust
- Department of Chemistry, Stony Brook University, Stony Brook, New York 11794-3400, USA
| | - Andras Lukacs
- School of Chemistry, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK
| | - James Iuliano
- Department of Chemistry, Stony Brook University, Stony Brook, New York 11794-3400, USA
| | - Jessica Jeng
- Department of Chemistry, Stony Brook University, Stony Brook, New York 11794-3400, USA
| | - Eduard Melief
- Department of Chemistry, Stony Brook University, Stony Brook, New York 11794-3400, USA
| | - Rui-Kun Zhao
- School of Chemistry, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK
| | - EunBin Yoon
- Department of Chemistry, Stony Brook University, Stony Brook, New York 11794-3400, USA
| | - Ian Clark
- Central Laser Facility, Harwell Science and Innovation Campus, Didcot, Oxon OX11 0QX, UK
| | - Michael Towrie
- Central Laser Facility, Harwell Science and Innovation Campus, Didcot, Oxon OX11 0QX, UK
| | - Gregory M. Greetham
- Central Laser Facility, Harwell Science and Innovation Campus, Didcot, Oxon OX11 0QX, UK
| | - Annabelle Ng
- William A. Shine Great Neck South High School, 341 Lakeville Rd, Great Neck, NY 11020, USA
| | - James Truglio
- William A. Shine Great Neck South High School, 341 Lakeville Rd, Great Neck, NY 11020, USA
| | - Jarrod French
- Department of Chemistry, Stony Brook University, Stony Brook, New York 11794-3400, USA
- Biochemistry & Cell Biology, Stony Brook University, Stony Brook, New York 11794-3400, USA
| | - Stephen R. Meech
- School of Chemistry, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK
| | - Peter J. Tonge
- Department of Chemistry, Stony Brook University, Stony Brook, New York 11794-3400, USA
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27
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Mehlhorn J, Lindtner T, Richter F, Glass K, Steinocher H, Beck S, Hegemann P, Kennis JTM, Mathes T. Light-Induced Rearrangement of the β5 Strand in the BLUF Photoreceptor SyPixD (Slr1694). J Phys Chem Lett 2015; 6:4749-4753. [PMID: 26631358 DOI: 10.1021/acs.jpclett.5b02245] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The structural changes that facilitate signal transduction in blue light sensors using FAD (BLUF) photoreceptors and confer the stability of the rearranged hydrogen bond network between flavin and protein in the signaling state are still poorly understood. Here, we investigate a semiconserved Trp residue in SyPixD (Slr1694) by isotope-edited vibrational spectroscopy and site-directed mutagenesis. In the signaling state, a β-sheet structure involving the backbone of W91 is formed without apparent change of environment of the W91 indole side chain. Mutation of W91, however, significantly influences the stability of the light-adapted state, suggesting that backbone rigidity rather than discrete side-chain conformations govern the stability of the light-adapted state. On the basis of computational and crystallographic models, we interpret these changes as a +1 register shift of the β2/β5 interaction with an unaffected indole side-chain conformation, rather than a +2 register shift accompanied by an indole side-chain flip that was previously proposed on the basis of X-ray structures.
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Affiliation(s)
- Jennifer Mehlhorn
- Department of Biology, Experimental Biophysics, Humboldt-Universität zu Berlin , Invalidenstraße 42, 10115 Berlin, Germany
| | - Tom Lindtner
- Department of Biology, Experimental Biophysics, Humboldt-Universität zu Berlin , Invalidenstraße 42, 10115 Berlin, Germany
| | - Florian Richter
- Department of Biology, Experimental Biophysics, Humboldt-Universität zu Berlin , Invalidenstraße 42, 10115 Berlin, Germany
| | - Kathrin Glass
- Department of Biology, Experimental Biophysics, Humboldt-Universität zu Berlin , Invalidenstraße 42, 10115 Berlin, Germany
| | - Helena Steinocher
- Department of Biology, Experimental Biophysics, Humboldt-Universität zu Berlin , Invalidenstraße 42, 10115 Berlin, Germany
| | - Sebastian Beck
- Department of Chemistry, Humboldt-Universität zu Berlin , Brook-Taylor-Str. 2, 12489 Berlin, Germany
| | - Peter Hegemann
- Department of Biology, Experimental Biophysics, Humboldt-Universität zu Berlin , Invalidenstraße 42, 10115 Berlin, Germany
| | - John T M Kennis
- Department of Physics and Astronomy, Biophysics Section, Faculty of Sciences, Vrije Universiteit , De Boelelaan 1081, 1081 HV, Amsterdam, The Netherlands
| | - Tilo Mathes
- Department of Biology, Experimental Biophysics, Humboldt-Universität zu Berlin , Invalidenstraße 42, 10115 Berlin, Germany
- Department of Physics and Astronomy, Biophysics Section, Faculty of Sciences, Vrije Universiteit , De Boelelaan 1081, 1081 HV, Amsterdam, The Netherlands
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28
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Mathes T, Götze JP. A proposal for a dipole-generated BLUF domain mechanism. Front Mol Biosci 2015; 2:62. [PMID: 26579529 PMCID: PMC4630285 DOI: 10.3389/fmolb.2015.00062] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2015] [Accepted: 10/12/2015] [Indexed: 11/25/2022] Open
Abstract
The resting and signaling structures of the blue-light sensing using flavin (BLUF) photoreceptor domains are still controversially debated due to differences in the molecular models obtained by crystal and NMR structures. Photocycles for the given preferred structural framework have been established, but a unifying picture combining experiment and theory remains elusive. We summarize present work on the AppA BLUF domain from both experiment and theory. We focus on IR and UV/vis spectra, and to what extent theory was able to reproduce experimental data and predict the structural changes upon formation of the signaling state. We find that the experimental observables can be theoretically reproduced employing any structural model, as long as the orientation of the signaling essential Gln63 and its tautomer state are a choice of the modeler. We also observe that few approaches are comparative, e.g., by considering all structures in the same context. Based on recent experimental findings and a few basic calculations, we suggest the possibility for a BLUF activation mechanism that only relies on electron transfer and its effect on the local electrostatics, not requiring an associated proton transfer. In this regard, we investigate the impact of dispersion correction on the interaction energies arising from weakly bound amino acids.
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Affiliation(s)
- Tilo Mathes
- Biophysics Group, Department of Physics and Astronomy, Faculty of Sciences, Vrije Universiteit Amsterdam, Netherlands ; Institut für Biologie/Experimentelle Biophysik, Humboldt Universität zu Berlin Berlin, Germany
| | - Jan P Götze
- School of Chemistry, University of St Andrews St Andrews, UK
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29
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Lindner R, Heintz U, Winkler A. Applications of hydrogen deuterium exchange (HDX) for the characterization of conformational dynamics in light-activated photoreceptors. Front Mol Biosci 2015; 2:33. [PMID: 26157802 PMCID: PMC4477167 DOI: 10.3389/fmolb.2015.00033] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2015] [Accepted: 05/26/2015] [Indexed: 11/13/2022] Open
Abstract
Rational design of optogenetic tools is inherently linked to the understanding of photoreceptor function. Structural analysis of elements involved in signal integration in individual sensor domains provides an initial idea of their mode of operation, but understanding how local structural rearrangements eventually affect signal transmission to output domains requires inclusion of the effector regions in the characterization. However, the dynamic nature of these assemblies renders their structural analysis challenging and therefore a combination of high- and low-resolution techniques is required to appreciate functional aspects of photoreceptors. This review focuses on the potential of hydrogen-deuterium exchange coupled to mass spectrometry (HDX-MS) for complementing the structural characterization of photoreceptors. In this respect, the ability of HDX-MS to provide information on conformational dynamics and the possibility to address multiple functionally relevant states in solution render this methodology ideally suitable. We highlight recent examples demonstrating the potential of HDX-MS and discuss how these results can help to improve existing optogenetic systems or guide the design of novel optogenetic tools.
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Affiliation(s)
- Robert Lindner
- Department of Biomolecular Mechanisms, Max Planck Institute for Medical Research Heidelberg, Germany
| | - Udo Heintz
- Department of Biomolecular Mechanisms, Max Planck Institute for Medical Research Heidelberg, Germany
| | - Andreas Winkler
- Institute of Biochemistry, Graz University of Technology Graz, Austria
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30
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Fudim R, Mehlhorn J, Berthold T, Weber S, Schleicher E, Kennis JTM, Mathes T. Photoinduced formation of flavin radicals in BLUF domains lacking the central glutamine. FEBS J 2015; 282:3161-74. [DOI: 10.1111/febs.13297] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2014] [Revised: 04/08/2015] [Accepted: 04/13/2015] [Indexed: 11/29/2022]
Affiliation(s)
- Roman Fudim
- Institut für Biologie/Experimentelle Biophysik; Humboldt Universität zu Berlin; Berlin Germany
| | - Jennifer Mehlhorn
- Institut für Biologie/Experimentelle Biophysik; Humboldt Universität zu Berlin; Berlin Germany
| | - Thomas Berthold
- Institut für Physikalische Chemie; Albert-Ludwigs-Universität Freiburg; Freiburg Germany
| | - Stefan Weber
- Institut für Physikalische Chemie; Albert-Ludwigs-Universität Freiburg; Freiburg Germany
- Freiburg Institute for Advanced Studies (FRIAS); Albert-Ludwigs-Universität Freiburg; Germany
| | - Erik Schleicher
- Institut für Physikalische Chemie; Albert-Ludwigs-Universität Freiburg; Freiburg Germany
- Inorganic Chemistry Laboratory; University of Oxford; UK
| | - John T. M. Kennis
- Biophysics Section; Department of Physics and Astronomy; Faculty of Sciences; VU University; Amsterdam The Netherlands
| | - Tilo Mathes
- Institut für Biologie/Experimentelle Biophysik; Humboldt Universität zu Berlin; Berlin Germany
- Biophysics Section; Department of Physics and Astronomy; Faculty of Sciences; VU University; Amsterdam The Netherlands
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31
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Laptenok SP, Lukacs A, Brust R, Haigney A, Gil A, Towrie M, Greetham GM, Tonge PJ, Meech SR. Electron transfer quenching in light adapted and mutant forms of the AppA BLUF domain. Faraday Discuss 2015; 177:293-311. [DOI: 10.1039/c4fd00189c] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The Blue Light Using Flavin (BLUF) domain proteins are an important family of photoreceptors controlling a range of responses in a wide variety of organisms. The details of the primary photochemical mechanism, by which light absorption in the isoalloxazine ring of the flavin is converted into a structure change to form the signalling state of the protein, is unresolved. In this work we apply ultrafast time resolved infra-red (TRIR) spectroscopy to investigate the primary photophysics of the BLUF domain of the protein AppA (AppABLUF) a light activated antirepressor. Here a number of mutations at Y21 and W104 in AppABLUF are investigated. The Y21 mutants are known to be photoinactive, while W104 mutants show the characteristic spectral red-shift associated with BLUF domain activity. Using TRIR we observed separately the decay of the excited state and the recovery of the ground state. In both cases the kinetics are found to be non-single exponential for all the proteins studied, suggesting a range of ground state structures. In the Y21 mutants an intermediate state was also observed, assigned to formation of the radical of the isoalloxazine (flavin) ring. The electron donor is the W104 residue. In contrast, no radical intermediates were detected in the studies of the photoactive dark adapted proteins, dAppABLUF and the dW104 mutants, suggesting a structure change in the Y21 mutants which favours W104 to isoalloxazine electron transfer. In contrast, in the light adapted form of the proteins (lAppABLUF, lW104) a radical intermediate was detected and the kinetics were greatly accelerated. In this case the electron donor was Y21 and major structural changes are associated with the enhanced quenching. In AppABLUF and the seven mutants studied radical intermediates are readily observed by TRIR spectroscopy, but there is no correlation with photoactivity. This suggests that if a charge separated state has a role in the BLUF photocycle it is only as a very short lived intermediate.
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Affiliation(s)
| | - Andras Lukacs
- School of Chemistry
- University of East Anglia
- Norwich NR4 7TJ
- UK
- Department of Biophysics
| | - Richard Brust
- Department of Chemistry
- Stony Brook University
- Stony Brook
- USA
| | | | - Agnieszka Gil
- Department of Chemistry
- Stony Brook University
- Stony Brook
- USA
| | - Michael Towrie
- Central Laser Facility
- Research Complex at Harwell
- Harwell Science and Innovation Campus
- Didcot
- UK
| | - Gregory M. Greetham
- Central Laser Facility
- Research Complex at Harwell
- Harwell Science and Innovation Campus
- Didcot
- UK
| | - Peter J. Tonge
- Department of Chemistry
- Stony Brook University
- Stony Brook
- USA
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32
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Conrad KS, Manahan CC, Crane BR. Photochemistry of flavoprotein light sensors. Nat Chem Biol 2014; 10:801-9. [PMID: 25229449 DOI: 10.1038/nchembio.1633] [Citation(s) in RCA: 167] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2014] [Accepted: 08/18/2014] [Indexed: 12/22/2022]
Abstract
Three major classes of flavin photosensors, light oxygen voltage (LOV) domains, blue light sensor using FAD (BLUF) proteins and cryptochromes (CRYs), regulate diverse biological activities in response to blue light. Recent studies of structure, spectroscopy and chemical mechanism have provided unprecedented insight into how each family operates at the molecular level. In general, the photoexcitation of the flavin cofactor leads to changes in redox and protonation states that ultimately remodel protein conformation and molecular interactions. For LOV domains, issues remain regarding early photochemical events, but common themes in conformational propagation have emerged across a diverse family of proteins. For BLUF proteins, photoinduced electron transfer reactions critical to light conversion are defined, but the subsequent rearrangement of hydrogen bonding networks key for signaling remains highly controversial. For CRYs, the relevant photocycles are actively debated, but mechanistic and functional studies are converging. Despite these challenges, our current understanding has enabled the engineering of flavoprotein photosensors for control of signaling processes within cells.
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Affiliation(s)
- Karen S Conrad
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York, USA
| | - Craig C Manahan
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York, USA
| | - Brian R Crane
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York, USA
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33
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Fujisawa T, Takeuchi S, Masuda S, Tahara T. Signaling-State Formation Mechanism of a BLUF Protein PapB from the Purple Bacterium Rhodopseudomonas palustris Studied by Femtosecond Time-Resolved Absorption Spectroscopy. J Phys Chem B 2014; 118:14761-73. [PMID: 25406769 DOI: 10.1021/jp5076252] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We studied the signaling-state formation of a BLUF (blue light using FAD) protein, PapB, from the purple bacterium Rhodopseudomonas palustris, using femtosecond time-resolved absorption spectroscopy. Upon photoexcitation of the dark state, FADH(•) (neutral flavin semiquinone FADH radical) was observed as the intermediate before the formation of the signaling state. The kinetic analysis based on singular value decomposition showed that FADH(•) mediates the signaling-state formation, showing that PapB is the second example of FADH(•)-mediated formation of the signaling state after Slr1694 (M. Gauden et al. Proc. Natl. Acad. Sci. U.S.A. 2006, 103, 10895-10900). The mechanism of the signaling-state formation is discussed on the basis of the comparison between femtosecond time-resolved absorption spectra of the dark state and those obtained by exciting the signaling state. FADH(•) was observed also with excitation of the signaling state, and surprisingly, the kinetics of FADH(•) was indistinguishable from the case of exciting the dark state. This result suggests that the hydrogen bond environment in the signaling state is realized before the formation of FADH(•) in the photocycle of PapB.
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Affiliation(s)
- Tomotsumi Fujisawa
- Molecular Spectroscopy Laboratory, RIKEN , 2-1 Hirosawa, Wako 351-0198, Japan
| | - Satoshi Takeuchi
- Molecular Spectroscopy Laboratory, RIKEN , 2-1 Hirosawa, Wako 351-0198, Japan.,Ultrafast Spectroscopy Research Team, RIKEN Center for Advanced Photonics (RAP), RIKEN , 2-1 Hirosawa, Wako 351-0198, Japan
| | - Shinji Masuda
- Center for Biological Resources and Informatics, and Earth-Life Science Institute, Tokyo Institute of Technology , Yokohama 226-8501, Japan
| | - Tahei Tahara
- Molecular Spectroscopy Laboratory, RIKEN , 2-1 Hirosawa, Wako 351-0198, Japan.,Ultrafast Spectroscopy Research Team, RIKEN Center for Advanced Photonics (RAP), RIKEN , 2-1 Hirosawa, Wako 351-0198, Japan
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34
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Collette F, Renger T, Schmidt am Busch M. Revealing the functional states in the active site of BLUF photoreceptors from electrochromic shift calculations. J Phys Chem B 2014; 118:11109-19. [PMID: 25153778 PMCID: PMC4174740 DOI: 10.1021/jp506400y] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2014] [Revised: 08/22/2014] [Indexed: 11/28/2022]
Abstract
Photoexcitation with blue light of the flavin chromophore in BLUF photoreceptors induces a switch into a metastable signaling state that is characterized by a red-shifted absorption maximum. The red shift is due to a rearrangement in the hydrogen bond pattern around Gln63 located in the immediate proximity of the isoalloxazine ring system of the chromophore. There is a long-lasting controversy between two structural models, named Q63A and Q63J in the literature, on the local conformation of the residues Gln63 and Tyr21 in the dark state of the photoreceptor. As regards the mechanistic details of the light-activation mechanism, rotation of Gln63 is opposed by tautomerism in the Q63A and Q63J models, respectively. We provide a structure-based simulation of electrochromic shifts of the flavin chromophore in the wild type and in various site-directed mutants. The excellent overall agreement between experimental and computed data allows us to evaluate the two structural models. Compelling evidence is obtained that the Q63A model is incorrect, whereas the Q63J is fully consistent with the present computations. Finally, we confirm independently that a keto-enol tautomerization of the glutamine at position 63, which was proposed as molecular mechanism for the transition between the dark and the light-adapted state, explains the measured 10 to 15 nm red shift in flavin absorption between these two states of the protein. We believe that the accurateness of our results provides evidence that the BLUF photoreceptors absorption is fine-tuned through electrostatic interactions between the chromophore and the protein matrix, and finally that the simplicity of our theoretical model is advantageous as regards easy reproducibility and further extensions.
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Affiliation(s)
- Florimond Collette
- Institut für Theoretische
Physik, Johannes Kepler Universität
Linz, Altenberger Strasse
69, 4040 Linz, Austria
| | - Thomas Renger
- Institut für Theoretische
Physik, Johannes Kepler Universität
Linz, Altenberger Strasse
69, 4040 Linz, Austria
| | - Marcel Schmidt am Busch
- Institut für Theoretische
Physik, Johannes Kepler Universität
Linz, Altenberger Strasse
69, 4040 Linz, Austria
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35
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Abstract
Most biological photoreceptors are protein/cofactor complexes that induce a physiological reaction upon absorption of a photon. Therefore, these proteins represent signal converters that translate light into biological information. Researchers use this property to stimulate and study various biochemical processes conveniently and non-invasively by the application of light, an approach known as optogenetics. Here, we summarize the recent experimental progress on the family of blue light receptors using FAD (BLUF) receptors. Several BLUF photoreceptors modulate second messenger levels and thus represent highly interesting tools for optogenetic application. In order to activate a coupled effector protein, the flavin-binding pocket of the BLUF domain undergoes a subtle rearrangement of the hydrogen network upon blue light absorption. The hydrogen bond switch is facilitated by the ultrafast light-induced proton-coupled electron transfer (PCET) between a tyrosine and the flavin in less than a nanosecond and remains stable on a long enough timescale for biochemical reactions to take place. The cyclic nature of the photoinduced reaction makes BLUF domains powerful model systems to study protein/cofactor interaction, protein-modulated PCET and novel mechanisms of biological signalling. The ultrafast nature of the photoconversion as well as the subtle structural rearrangement requires sophisticated spectroscopic and molecular biological methods to study and understand this highly intriguing signalling process.
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Affiliation(s)
- John T M Kennis
- Biophysics Group, Department of Physics and Astronomy, Faculty of Sciences , Vrije Universiteit , De Boelelaan 1081, 1081 HV Amsterdam , The Netherlands
| | - Tilo Mathes
- Biophysics Group, Department of Physics and Astronomy, Faculty of Sciences , Vrije Universiteit , De Boelelaan 1081, 1081 HV Amsterdam , The Netherlands
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36
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Migliore A, Polizzi NF, Therien M, Beratan DN. Biochemistry and theory of proton-coupled electron transfer. Chem Rev 2014; 114:3381-465. [PMID: 24684625 PMCID: PMC4317057 DOI: 10.1021/cr4006654] [Citation(s) in RCA: 340] [Impact Index Per Article: 34.0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2013] [Indexed: 02/01/2023]
Affiliation(s)
- Agostino Migliore
- Department
of Chemistry, Department of Biochemistry, and Department of Physics, Duke University, Durham, North Carolina 27708, United States
| | - Nicholas F. Polizzi
- Department
of Chemistry, Department of Biochemistry, and Department of Physics, Duke University, Durham, North Carolina 27708, United States
| | - Michael
J. Therien
- Department
of Chemistry, Department of Biochemistry, and Department of Physics, Duke University, Durham, North Carolina 27708, United States
| | - David N. Beratan
- Department
of Chemistry, Department of Biochemistry, and Department of Physics, Duke University, Durham, North Carolina 27708, United States
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37
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Lukacs A, Brust R, Haigney A, Laptenok SP, Addison K, Gil A, Towrie M, Greetham GM, Tonge PJ, Meech SR. BLUF domain function does not require a metastable radical intermediate state. J Am Chem Soc 2014; 136:4605-15. [PMID: 24579721 PMCID: PMC4004230 DOI: 10.1021/ja4121082] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
BLUF (blue light using flavin) domain proteins are an important family of blue light-sensing proteins which control a wide variety of functions in cells. The primary light-activated step in the BLUF domain is not yet established. A number of experimental and theoretical studies points to a role for photoinduced electron transfer (PET) between a highly conserved tyrosine and the flavin chromophore to form a radical intermediate state. Here we investigate the role of PET in three different BLUF proteins, using ultrafast broadband transient infrared spectroscopy. We characterize and identify infrared active marker modes for excited and ground state species and use them to record photochemical dynamics in the proteins. We also generate mutants which unambiguously show PET and, through isotope labeling of the protein and the chromophore, are able to assign modes characteristic of both flavin and protein radical states. We find that these radical intermediates are not observed in two of the three BLUF domains studied, casting doubt on the importance of the formation of a population of radical intermediates in the BLUF photocycle. Further, unnatural amino acid mutagenesis is used to replace the conserved tyrosine with fluorotyrosines, thus modifying the driving force for the proposed electron transfer reaction; the rate changes observed are also not consistent with a PET mechanism. Thus, while intermediates of PET reactions can be observed in BLUF proteins they are not correlated with photoactivity, suggesting that radical intermediates are not central to their operation. Alternative nonradical pathways including a keto-enol tautomerization induced by electronic excitation of the flavin ring are considered.
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Affiliation(s)
- Andras Lukacs
- Department of Chemistry, Stony Brook University , Stony Brook, New York 11794-3400, United States
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38
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Domratcheva T, Udvarhelyi A, Shahi ARM. Computational spectroscopy, dynamics, and photochemistry of photosensory flavoproteins. Methods Mol Biol 2014; 1146:191-228. [PMID: 24764094 DOI: 10.1007/978-1-4939-0452-5_10] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Extensive interest in photosensory proteins stimulated computational studies of flavins and flavoproteins in the past decade. This review is dedicated to the three central topics of these studies: calculations of flavin UV-visible and IR spectra, simulated dynamics of photoreceptor proteins, and flavin photochemistry. Accordingly, this chapter is divided into three parts; each part describes corresponding computational protocols, summarizes computational results, and discusses the emerging mechanistic picture.
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Affiliation(s)
- Tatiana Domratcheva
- Department of Biomolecular Mechanisms, Max Planck Institute for Medical Research, Jahnstraße 29, 69120, Heidelberg, Germany,
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39
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Winkler A, Udvarhelyi A, Hartmann E, Reinstein J, Menzel A, Shoeman RL, Schlichting I. Characterization of elements involved in allosteric light regulation of phosphodiesterase activity by comparison of different functional BlrP1 states. J Mol Biol 2013; 426:853-68. [PMID: 24291457 PMCID: PMC3989770 DOI: 10.1016/j.jmb.2013.11.018] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2013] [Revised: 11/18/2013] [Accepted: 11/20/2013] [Indexed: 12/31/2022]
Abstract
Bacteria have evolved dedicated signaling mechanisms that enable the integration of a range of environmental stimuli and the accordant modulation of metabolic pathways. One central signaling molecule in bacteria is the second messenger cyclic dimeric GMP (c-di-GMP). Complex regulatory mechanisms for modulating c-di-GMP concentrations have evolved, in line with its importance for maintaining bacterial fitness under changing environmental conditions. One interesting example in this context is the blue-light-regulated phosphodiesterase 1 (BlrP1) of Klebsiella pneumoniae. This covalently linked system of a sensor of blue light using FAD (BLUF) and an EAL phosphodiesterase domain orchestrates the light-dependent down-regulation of c-di-GMP levels. To reveal details of light-induced structural changes involved in EAL activity regulation, we extended previous crystallographic studies with hydrogen–deuterium exchange experiments and small-angle X-ray scattering analysis of different functional BlrP1 states. The combination of hydrogen–deuterium exchange and small-angle X-ray scattering allows the integration of local and global structural changes and provides an improved understanding of light signaling via an allosteric communication pathway between the BLUF and EAL domains. This model is supported by results from a mutational analysis of the EAL dimerization region and the analysis of metal-coordination effects of the EAL active site on the dark-state recovery kinetics of the BLUF domain. In combination with structural information from other EAL domains, the observed bidirectional communication points to a general mechanism of EAL activity regulation and suggests that a similar allosteric coupling is maintained in catalytically inactive EAL domains that retain a regulatory function. C-di-GMP is a central bacterial signaling molecule integrating environmental stimuli. BlrP1 enables the light-regulated degradation of c-di-GMP. Light-induced structural changes involve subtle quaternary structure rearrangements. Light signal integration involves allosteric signaling between BLUF and EAL. Analysis of different functional states reveals details of this communication pathway.
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Affiliation(s)
- Andreas Winkler
- Department of Biomolecular Mechanisms, Max Planck Institute for Medical Research, Jahnstrasse 29, 69120 Heidelberg, Germany.
| | - Anikó Udvarhelyi
- Department of Biomolecular Mechanisms, Max Planck Institute for Medical Research, Jahnstrasse 29, 69120 Heidelberg, Germany.
| | - Elisabeth Hartmann
- Department of Biomolecular Mechanisms, Max Planck Institute for Medical Research, Jahnstrasse 29, 69120 Heidelberg, Germany.
| | - Jochen Reinstein
- Department of Biomolecular Mechanisms, Max Planck Institute for Medical Research, Jahnstrasse 29, 69120 Heidelberg, Germany.
| | | | - Robert L Shoeman
- Department of Biomolecular Mechanisms, Max Planck Institute for Medical Research, Jahnstrasse 29, 69120 Heidelberg, Germany.
| | - Ilme Schlichting
- Department of Biomolecular Mechanisms, Max Planck Institute for Medical Research, Jahnstrasse 29, 69120 Heidelberg, Germany.
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40
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Mehlhorn J, Steinocher H, Beck S, Kennis JTM, Hegemann P, Mathes T. A set of engineered Escherichia coli expression strains for selective isotope and reactivity labeling of amino acid side chains and flavin cofactors. PLoS One 2013; 8:e79006. [PMID: 24223875 PMCID: PMC3815312 DOI: 10.1371/journal.pone.0079006] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2013] [Accepted: 09/21/2013] [Indexed: 11/18/2022] Open
Abstract
Biological reactions are facilitated by delicate molecular interactions between proteins, cofactors and substrates. To study and understand their dynamic interactions researchers have to take great care not to influence or distort the object of study. As a non-invasive alternative to a site-directed mutagenesis approach, selective isotope labeling in combination with vibrational spectroscopy may be employed to directly identify structural transitions in wild type proteins. Here we present a set of customized Escherichia coli expression strains, suitable for replacing both the flavin cofactor and/or selective amino acids with isotope enriched or chemically modified substrates. For flavin labeling we report optimized auxotrophic strains with significantly enhanced flavin uptake properties. Labeled protein biosynthesis using these strains was achieved in optimized cultivation procedures using high cell density fermentation. Finally, we demonstrate how this approach is used for a clear assignment of vibrational spectroscopic difference signals of apoprotein and cofactor of a flavin containing photoreceptor of the BLUF (Blue Light receptors Using FAD) family.
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Affiliation(s)
- Jennifer Mehlhorn
- Institut für Biologie/Experimentelle Biophysik, Humboldt-Universität zu Berlin, Berlin, Germany
| | - Helena Steinocher
- Institut für Biologie/Experimentelle Biophysik, Humboldt-Universität zu Berlin, Berlin, Germany
| | - Sebastian Beck
- Institut für Chemie, Humboldt-Universität zu Berlin, Berlin, Germany
| | - John T. M. Kennis
- Biophysics Group, Department of Physics and Astronomy, Faculty of Sciences, Vrije Universiteit, Amsterdam, The Netherlands
| | - Peter Hegemann
- Institut für Biologie/Experimentelle Biophysik, Humboldt-Universität zu Berlin, Berlin, Germany
| | - Tilo Mathes
- Institut für Biologie/Experimentelle Biophysik, Humboldt-Universität zu Berlin, Berlin, Germany
- Biophysics Group, Department of Physics and Astronomy, Faculty of Sciences, Vrije Universiteit, Amsterdam, The Netherlands
- * E-mail:
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