1
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Demchenko AP. Proton transfer reactions: from photochemistry to biochemistry and bioenergetics. BBA ADVANCES 2023. [DOI: 10.1016/j.bbadva.2023.100085] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/12/2023] Open
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2
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Sen T, Ma Y, Polyakov IV, Grigorenko BL, Nemukhin AV, Krylov AI. Interplay between Locally Excited and Charge Transfer States Governs the Photoswitching Mechanism in the Fluorescent Protein Dreiklang. J Phys Chem B 2021; 125:757-770. [PMID: 33411528 DOI: 10.1021/acs.jpcb.0c09221] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
We present the results of high-level electronic structure and dynamics simulations of the photoactive protein Dreiklang. With the goal of understanding the details of the Dreiklang photocycle, we carefully characterize the excited states of the ON- and OFF-forms of Dreiklang. The key finding of our study is the existence of a low-lying excited state of a charge-transfer character in the neutral ON form and that population of this state, which is nearly isoenergetic with the locally excited bright state, initiates a series of steps that ultimately lead to the formation of the hydrated dark chromophore (OFF state). These results allow us to refine the mechanistic picture of Dreiklang's photocycle and photoactivation.
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Affiliation(s)
- Tirthendu Sen
- Department of Chemistry, University of Southern California, Los Angeles, California 90089-0482, United States
| | - Yingying Ma
- Department of Chemistry, University of Southern California, Los Angeles, California 90089-0482, United States
| | - Igor V Polyakov
- Department of Chemistry, Lomonosov Moscow State University, Moscow, 119992, Russia.,Emanuel Institute of Biochemical Physics, Russian Academy of Sciences, Moscow, 119991, Russia
| | - Bella L Grigorenko
- Department of Chemistry, Lomonosov Moscow State University, Moscow, 119992, Russia.,Emanuel Institute of Biochemical Physics, Russian Academy of Sciences, Moscow, 119991, Russia
| | - Alexander V Nemukhin
- Department of Chemistry, Lomonosov Moscow State University, Moscow, 119992, Russia.,Emanuel Institute of Biochemical Physics, Russian Academy of Sciences, Moscow, 119991, Russia
| | - Anna I Krylov
- Department of Chemistry, University of Southern California, Los Angeles, California 90089-0482, United States
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3
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Mamontova AV, Shakhov AM, Grigoryev AP, Lukyanov KA, Bogdanov AM. Increasing the Fluorescence Brightness of Superphotostable EGFP Mutant by Introducing Mutations That Block Chromophore Protonation. RUSSIAN JOURNAL OF BIOORGANIC CHEMISTRY 2020. [DOI: 10.1134/s1068162020060187] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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4
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Kaur J, Yadav NS, Singh MK, Khan MJ, Sen S, Dixit A, Choudhury D. Role of Ser65, His148 and Thr203 in the Organic Solvent-dependent Spectral Shift in Green Fluorescent Protein. Photochem Photobiol 2018; 95:543-555. [PMID: 30240005 DOI: 10.1111/php.13018] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2018] [Accepted: 09/04/2018] [Indexed: 01/10/2023]
Abstract
The photophysics of green fluorescent protein (GFP) is remarkable because of its exceptional property of excited state proton transfer (ESPT) and the presence of a functional proton wire. Another interesting property of wild-type GFP is that its absorption and fluorescence excitation spectra are sensitive to the presence of polar organic solvents even at very low concentrations. Here, we use a combination of methodologies including site-specific mutagenesis, absorption spectroscopy, steady-state and time-resolved fluorescence measurements and all-atom molecular dynamics simulations in explicit solvent, to uncover the mechanism behind the unique spectral sensitivity of GFP toward organic solvents. Based on the evidences provided herein, we suggest that organic solvent-induced changes in the proton wire prevent ground state movement of a proton through the wire and thus bring about the spectral changes observed. The present study can not only help to understand the mechanism of proton transfer by further dissecting the intricate steps in GFP photophysics but also encourages to develop GFP-based organic solvent biosensors.
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Affiliation(s)
- Jasvir Kaur
- School of Biotechnology, Jawaharlal Nehru University, New Delhi, India
| | - Neetu Singh Yadav
- School of Biotechnology, Jawaharlal Nehru University, New Delhi, India
| | | | - Mohd Jahir Khan
- School of Biotechnology, Jawaharlal Nehru University, New Delhi, India
| | - Sobhan Sen
- School of Physical Sciences, Jawaharlal Nehru University, New Delhi, India
| | - Aparna Dixit
- School of Biotechnology, Jawaharlal Nehru University, New Delhi, India
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5
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Excited State Structural Evolution of a GFP Single-Site Mutant Tracked by Tunable Femtosecond-Stimulated Raman Spectroscopy. Molecules 2018; 23:molecules23092226. [PMID: 30200474 PMCID: PMC6225354 DOI: 10.3390/molecules23092226] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2018] [Revised: 08/29/2018] [Accepted: 08/31/2018] [Indexed: 12/31/2022] Open
Abstract
Tracking vibrational motions during a photochemical or photophysical process has gained momentum, due to its sensitivity to the progression of reaction and change of environment. In this work, we implemented an advanced ultrafast vibrational technique, femtosecond-stimulated Raman spectroscopy (FSRS), to monitor the excited state structural evolution of an engineered green fluorescent protein (GFP) single-site mutant S205V. This mutation alters the original excited state proton transfer (ESPT) chain. By strategically tuning the Raman pump to different wavelengths (i.e., 801, 539, and 504 nm) to achieve pre-resonance with transient excited state electronic bands, the characteristic Raman modes of the excited protonated (A*) chromophore species and intermediate deprotonated (I*) species can be selectively monitored. The inhomogeneous distribution/population of A* species go through ESPT with a similar ~300 ps time constant, confirming that bridging a water molecule to protein residue T203 in the ESPT chain is the rate-limiting step. Some A* species undergo vibrational cooling through high-frequency motions on the ~190 ps time scale. At early times, a portion of the largely protonated A* species could also undergo vibrational cooling or return to the ground state with a ~80 ps time constant. On the photoproduct side, a ~1330 cm−1 delocalized motion is observed, with dispersive line shapes in both the Stokes and anti-Stokes FSRS with a pre-resonance Raman pump, which indicates strong vibronic coupling, as the mode could facilitate the I* species to reach a relatively stable state (e.g., the main fluorescent state) after conversion from A*. Our findings disentangle the contributions of various vibrational motions active during the ESPT reaction, and offer new structural dynamics insights into the fluorescence mechanisms of engineered GFPs and other analogous autofluorescent proteins.
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6
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Tang L, Wang Y, Zhu L, Kallio K, Remington SJ, Fang C. Photoinduced proton transfer inside an engineered green fluorescent protein: a stepwise-concerted-hybrid reaction. Phys Chem Chem Phys 2018; 20:12517-12526. [PMID: 29708241 DOI: 10.1039/c8cp01907j] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Photoactivated proton transfer (PT) wire is responsible for the glow of green fluorescent protein (GFP), which is crucial for bioimaging and biomedicine. In this work, a new GFP-S65T/S205V double mutant is developed from wild-type GFP in which the PT wire is significantly modified. We implement femtosecond transient absorption (fs-TA) and femtosecond stimulated Raman spectroscopy (FSRS) to delineate the PT process in action. The excited state proton transfer proceeds on the ∼110 ps timescale, which infers that the distance of one key link (water to T203) in the PT wire of GFP-S205V is shortened by the extra S65T mutation. The rise of an imidazolinone ring deformation mode at ∼871 cm-1 in FSRS further suggests that this PT reaction is in a concerted manner. A ∼4 ps component prior to large-scale proton dissociation through the PT wire is also retrieved, indicative of some small-scale proton motions and heavy-atom rearrangement in the vicinity of the chromophore. Our work provides deep insights into the novel hybrid PT mechanism in engineered GFP and demonstrates the power of tunable FSRS methodology in tracking ultrafast photoreactions with the desirable structural specificity in physiological environments.
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Affiliation(s)
- Longteng Tang
- Oregon State University, Department of Chemistry, 263 Linus Pauling Science Centre (lab), 153 Gilbert Hall (office), Corvallis, OR 97331, USA.
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7
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Wineman-Fisher V, Simkovich R, Huppert D, Trujillo K, Remington SJ, Miller Y. Mutagenic induction of an ultra-fast water-chain proton wire. Phys Chem Chem Phys 2018; 18:23089-95. [PMID: 27492977 DOI: 10.1039/c6cp05071a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Replacement of the hydroxyl group of a hydrophilic sidechain by an H atom in the proton wire of GFP induces formation of a water-chain proton wire. Surprisingly, this "non-native" water chain functions as a proton wire with response times within 10 ps of the wild type protein. This remarkable rate retention is understood as a natural consequence of the well-known Grotthuss mechanism of proton transfer in water.
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Affiliation(s)
- Vered Wineman-Fisher
- Department of Chemistry, Ben-Gurion University of the Negev, P.O. Box 653, Be'er Sheva 84105, Israel. and Ilse Katz Institute for Nanoscale Science and Technology, Ben-Gurion University of the Negev, Beér-Sheva 84105, Israel
| | - Ron Simkovich
- Raymond and Beverly Sackler Faculty of Exact Sciences, School of Chemistry, Tel Aviv University, Tel Aviv 69978, Israel
| | - Dan Huppert
- Raymond and Beverly Sackler Faculty of Exact Sciences, School of Chemistry, Tel Aviv University, Tel Aviv 69978, Israel
| | - Kristina Trujillo
- Department of Physics and Institute of Molecular Biology, University of Oregon, Eugene, USA
| | - S James Remington
- Department of Physics and Institute of Molecular Biology, University of Oregon, Eugene, USA
| | - Yifat Miller
- Department of Chemistry, Ben-Gurion University of the Negev, P.O. Box 653, Be'er Sheva 84105, Israel. and Ilse Katz Institute for Nanoscale Science and Technology, Ben-Gurion University of the Negev, Beér-Sheva 84105, Israel
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8
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Green O, Gajst O, Simkovitch R, Shabat D, Huppert D. Chloro benzoate cyanine picolinium photoacid excited-state proton transfer to water. J Photochem Photobiol A Chem 2017. [DOI: 10.1016/j.jphotochem.2017.08.056] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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9
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Tang L, Wang Y, Liu W, Zhao Y, Campbell RE, Fang C. Illuminating Photochemistry of an Excitation Ratiometric Fluorescent Protein Calcium Biosensor. J Phys Chem B 2017; 121:3016-3023. [PMID: 28326779 DOI: 10.1021/acs.jpcb.7b01269] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Fluorescent protein (FP)-based biosensors have become an important and promising tool to track metal ion movement inside living systems. Their working principles after light irradiation, however, remain elusive. To facilitate the rational design of biosensors, we dissect the fluorescence modulation mechanism of a newly developed excitation ratiometric green FP-based Ca2+ biosensor, GEX-GECO1, using femtosecond stimulated Raman spectroscopy (FSRS) in the electronic excited state. Upon 400 nm photoexcitation, characteristic vibrational marker bands at ∼1180 and 1300 cm-1 show concomitant decay and rise dynamics, probing the progression of an ultrafast excited state proton transfer (ESPT) reaction. The Ca2+-bound biosensor exhibits two distinct populations that undergo ESPT with ∼6 and 80 ps time constants, in contrast to one dominant population with a 25 ps time constant in the Ca2+-free biosensor. This result is supported by key structural constraints from molecular dynamics simulations with and without Ca2+. The blueshift of the ∼1265 cm-1 C-O stretch mode unravels the vibrational cooling dynamics of the protonated chromophore regardless of Ca2+ binding events. This unique line of inquiry reveals the essential structural dynamics basis of fluorescence modulation inside an excitation ratiometric protein biosensor, correlating the uncovered chromophore structural heterogeneity with different H-bonding configurations and intrinsic proton transfer rate in the photoexcited state.
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Affiliation(s)
- Longteng Tang
- Department of Chemistry, Oregon State University , Corvallis, Oregon 97331, United States
| | - Yanli Wang
- Department of Chemistry, Oregon State University , Corvallis, Oregon 97331, United States
| | - Weimin Liu
- Department of Chemistry, Oregon State University , Corvallis, Oregon 97331, United States
| | - Yongxin Zhao
- Department of Chemistry, University of Alberta , Edmonton, Alberta T6G 2G2, Canada
| | - Robert E Campbell
- Department of Chemistry, University of Alberta , Edmonton, Alberta T6G 2G2, Canada
| | - Chong Fang
- Department of Chemistry, Oregon State University , Corvallis, Oregon 97331, United States
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10
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Abstract
Inside proteins, protons move on proton wires (PWs). Starting from the highest resolution X-ray structure available, we conduct a 306 ns molecular dynamics simulation of the (A-state) wild-type (wt) green fluorescent protein (GFP) to study how its PWs change with time. We find that the PW from the chromophore via Ser205 to Glu222, observed in all X-ray structures, undergoes rapid water molecule insertion between Ser205 and Glu222. Sometimes, an alternate Ser205-bypassing PW exists. Side chain rotations of Thr203 and Ser205 play an important role in shaping the PW network in the chromophore region. Thr203, with its bulkier side chain, exhibits slower transitions between its three rotameric states. Ser205 experiences more frequent rotations, slowing down when the Thr203 methyl group is close by. The combined states of both residues affect the PW probabilities. A random walk search for PWs from the chromophore reveals several exit points to the bulk, one being a direct water wire (WW) from the chromophore to the bulk. A longer WW connects the "bottom" of the GFP barrel with a "water pool" (WP1) situated below Glu222. These two WWs were not observed in X-ray structures of wt-GFP, but their analogues have been reported in related fluorescent proteins. Surprisingly, the high-resolution X-ray structure utilized herein shows that Glu222 is protonated at low temperatures. At higher temperatures, we suggest ion pairing between anionic Glu222 and a proton hosted in WP1. Upon photoexcitation, these two recombine, while a second proton dissociates from the chromophore and either exits the protein using the short WW or migrates along the GFP-barrel axis on the long WW. This mechanism reconciles the conflicting experimental and theoretical data on proton motion within GFP.
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Affiliation(s)
- Ai Shinobu
- The Fritz Haber Research Center, Institute of Chemistry, The Hebrew University of Jerusalem , Jerusalem 91904, Israel
| | - Noam Agmon
- The Fritz Haber Research Center, Institute of Chemistry, The Hebrew University of Jerusalem , Jerusalem 91904, Israel
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11
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Acharya A, Bogdanov AM, Grigorenko BL, Bravaya KB, Nemukhin AV, Lukyanov KA, Krylov AI. Photoinduced Chemistry in Fluorescent Proteins: Curse or Blessing? Chem Rev 2016; 117:758-795. [PMID: 27754659 DOI: 10.1021/acs.chemrev.6b00238] [Citation(s) in RCA: 178] [Impact Index Per Article: 22.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Photoinduced reactions play an important role in the photocycle of fluorescent proteins from the green fluorescent protein (GFP) family. Among such processes are photoisomerization, photooxidation/photoreduction, breaking and making of covalent bonds, and excited-state proton transfer (ESPT). Many of these transformations are initiated by electron transfer (ET). The quantum yields of these processes vary significantly, from nearly 1 for ESPT to 10-4-10-6 for ET. Importantly, even when quantum yields are relatively small, at the conditions of repeated illumination the overall effect is significant. Depending on the task at hand, fluorescent protein photochemistry is regarded either as an asset facilitating new applications or as a nuisance leading to the loss of optical output. The phenomena arising due to phototransformations include (i) large Stokes shifts, (ii) photoconversions, photoactivation, and photoswitching, (iii) phototoxicity, (iv) blinking, (v) permanent bleaching, and (vi) formation of long-lived intermediates. The focus of this review is on the most recent experimental and theoretical work on photoinduced transformations in fluorescent proteins. We also provide an overview of the photophysics of fluorescent proteins, highlighting the interplay between photochemistry and other channels (fluorescence, radiationless relaxation, and intersystem crossing). The similarities and differences with photochemical processes in other biological systems and in dyes are also discussed.
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Affiliation(s)
- Atanu Acharya
- Department of Chemistry, University of Southern California , Los Angeles, California 90089-0482, United States
| | - Alexey M Bogdanov
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry , Moscow, Russia.,Nizhny Novgorod State Medical Academy , Nizhny Novgorod, Russia
| | - Bella L Grigorenko
- Department of Chemistry, Lomonosov Moscow State University , Moscow, Russia.,Emanuel Institute of Biochemical Physics, Russian Academy of Sciences , Moscow, Russia
| | - Ksenia B Bravaya
- Department of Chemistry, Boston University , Boston, Massachusetts United States
| | - Alexander V Nemukhin
- Department of Chemistry, Lomonosov Moscow State University , Moscow, Russia.,Emanuel Institute of Biochemical Physics, Russian Academy of Sciences , Moscow, Russia
| | - Konstantin A Lukyanov
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry , Moscow, Russia.,Nizhny Novgorod State Medical Academy , Nizhny Novgorod, Russia
| | - Anna I Krylov
- Department of Chemistry, University of Southern California , Los Angeles, California 90089-0482, United States
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12
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Armengol P, Gelabert R, Moreno M, Lluch JM. Theoretical Computer-Aided Mutagenic Study on the Triple Green Fluorescent Protein Mutant S65T/H148D/Y145F. Chemphyschem 2015; 16:2134-9. [PMID: 25916771 DOI: 10.1002/cphc.201500158] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2015] [Revised: 03/27/2015] [Indexed: 11/07/2022]
Abstract
Green fluorescent protein (GFP) mutant S65T/H148D has been proposed to host a photocycle that involves an excited-state proton transfer between the chromophore (Cro) and the Asp148 residue and takes place in less than 50 fs without a measurable kinetic isotope effect. It has been suggested that the interaction between the unsuspected Tyr145 residue and the chromophore is needed for the ultrafast sub-50 fs rise in fluorescence. To verify this, we have performed a computer-aided mutagenic study to introduce the additional mutation Y145F, which eliminates this interaction. By means of QM/MM molecular dynamics simulations and time-dependent density functional theory studies, we have assessed the importance of the Cro-Tyr145 interaction and the solvation of Asp148 and shown that in the triple mutant S65T/H148D/Y145F a significant loss in the ultrafast rise of the Stokes-shifted fluorescence should be expected.
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Affiliation(s)
- Pau Armengol
- Department de Química, Universitat Autònoma de Barcelona, 08193 Bellaterra, Barcelona (Spain)
| | - Ricard Gelabert
- Department de Química, Universitat Autònoma de Barcelona, 08193 Bellaterra, Barcelona (Spain).
| | - Miquel Moreno
- Department de Química, Universitat Autònoma de Barcelona, 08193 Bellaterra, Barcelona (Spain)
| | - José M Lluch
- Department de Química, Universitat Autònoma de Barcelona, 08193 Bellaterra, Barcelona (Spain).,Institut de Bioquímica i de Biomedicina, Universitat Autònoma de Barcelona, 08193 Bellaterra, Barcelona (Spain)
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13
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Laptenok SP, Lukacs A, Gil A, Brust R, Sazanovich IV, Greetham GM, Tonge PJ, Meech SR. Complete Proton Transfer Cycle in GFP and Its T203V and S205V Mutants. Angew Chem Int Ed Engl 2015. [DOI: 10.1002/ange.201503672] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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14
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Laptenok SP, Lukacs A, Gil A, Brust R, Sazanovich IV, Greetham GM, Tonge PJ, Meech SR. Complete Proton Transfer Cycle in GFP and Its T203V and S205V Mutants. Angew Chem Int Ed Engl 2015; 54:9303-7. [PMID: 26087935 PMCID: PMC4576823 DOI: 10.1002/anie.201503672] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2015] [Indexed: 11/17/2022]
Abstract
Proton transfer is critical in many important biochemical reactions. The unique three-step excited-state proton transfer in avGFP allows observations of protein proton transport in real-time. In this work we exploit femtosecond to microsecond transient IR spectroscopy to record, in D2O, the complete proton transfer photocycle of avGFP, and two mutants (T203V and S205V) which modify the structure of the proton wire. Striking differences and similarities are observed among the three mutants yielding novel information on proton transfer mechanism, rates, isotope effects, H-bond strength and proton wire stability. These data provide a detailed picture of the dynamics of long-range proton transfer in a protein against which calculations may be compared.
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Affiliation(s)
- Sergey P Laptenok
- School of Chemistry, University of East Anglia, Norwich, NR4 7TJ (UK)
| | - Andras Lukacs
- School of Chemistry, University of East Anglia, Norwich, NR4 7TJ (UK).,Department of Biophysics, Medical School, Szigeti str. 12, 7624 Pécs (Hungary)
| | - Agnieszka Gil
- Department of Chemistry, Stony Brook University, Stony Brook, NY 11794-3400 (USA)
| | - Richard Brust
- Department of Chemistry, Stony Brook University, Stony Brook, NY 11794-3400 (USA).,The Scripps Research Institute, 130 Scripps Way, Jupiter, FL 33458 (USA)
| | - Igor V Sazanovich
- Central Laser Facility, Research Complex at Harwell, Harwell Science and Innovation Campus, Didcot, Oxon OX11 0QX (UK)
| | - Gregory M Greetham
- Central Laser Facility, Research Complex at Harwell, Harwell Science and Innovation Campus, Didcot, Oxon OX11 0QX (UK)
| | - 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).
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15
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Shinobu A, Agmon N. The Hole in the Barrel: Water Exchange at the GFP Chromophore. J Phys Chem B 2015; 119:3464-78. [DOI: 10.1021/jp5127255] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Ai Shinobu
- The Fritz
Haber Research
Center, Institute of Chemistry, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
| | - Noam Agmon
- The Fritz
Haber Research
Center, Institute of Chemistry, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
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16
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Simkovitch R, Gepshtein R, Huppert D. Fast photoinduced reactions in the condensed phase are nonexponential. J Phys Chem A 2015; 119:1797-812. [PMID: 25594744 DOI: 10.1021/jp508856k] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Time-resolved measurements of photoinduced reactions reveal that many ultrafast reactions in the femto- to picosecond time scale are nonexponential. In this article we provide several examples of reactions that exhibit a nonexponential rate. We explain the wide range of the nonexponential reaction by the lack of time separation between τ(s), the characteristic fast equilibration time of the population in the reactant potential well, and the longer time τ(e), the characteristic time to cross the energy barrier between the reactant and the product.
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Affiliation(s)
- Ron Simkovitch
- Raymond and Beverly Sackler Faculty of Exact Sciences, School of Chemistry, Tel Aviv University , Tel Aviv 69978, Israel
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17
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Velez-Vega C, McKay DJJ, Aravamuthan V, Pearlstein R, Duca JS. Time-averaged distributions of solute and solvent motions: exploring proton wires of GFP and PfM2DH. J Chem Inf Model 2014; 54:3344-61. [PMID: 25405925 DOI: 10.1021/ci500571h] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Proton translocation pathways of selected variants of the green fluorescent protein (GFP) and Pseudomonas fluorescens mannitol 2-dehydrogenase (PfM2DH) were investigated via an explicit solvent molecular dynamics-based analysis protocol that allows for direct quantitative relationship between a crystal structure and its time-averaged solute-solvent structure obtained from simulation. Our study of GFP is in good agreement with previous research suggesting that the proton released from the chromophore upon photoexcitation can diffuse through an extended internal hydrogen bonding network that allows for the proton to exit to bulk or be recaptured by the anionic chromophore. Conversely for PfM2DH, we identified the most probable ionization states of key residues along the proton escape channel from the catalytic site to bulk solvent, wherein the solute and high-density solvent crystal structures of binary and ternary complexes were properly reproduced. Furthermore, we proposed a plausible mechanism for this proton translocation process that is consistent with the state-dependent structural shifts observed in our analysis. The time-averaged structures generated from our analyses facilitate validation of MD simulation results and provide a comprehensive profile of the dynamic all-occupancy solvation network within and around a flexible solute, from which detailed hydrogen-bonding networks can be inferred. In this way, potential drawbacks arising from the elucidation of these networks by examination of static crystal structures or via alternate rigid-protein solvation analysis procedures can be overcome. Complementary studies aimed at the effective use of our methodology for alternate implementations (e.g., ligand design) are currently underway.
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Affiliation(s)
- Camilo Velez-Vega
- Computer-Aided Drug Discovery, Global Discovery Chemistry, Novartis Institutes for BioMedical Research , 100 Technology Square, Cambridge, Massachusetts 02139, United States
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18
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Armengol P, Gelabert R, Moreno M, Lluch JM. New insights into the structure–spectrum relationship in S65T/H148D and E222Q/H148D green fluorescent protein mutants: a theoretical assessment. Org Biomol Chem 2014; 12:9845-52. [DOI: 10.1039/c4ob01462f] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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19
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Simkovitch R, Shomer S, Gepshtein R, Huppert D. How Fast Can a Proton-Transfer Reaction Be beyond the Solvent-Control Limit? J Phys Chem B 2014; 119:2253-62. [DOI: 10.1021/jp506011e] [Citation(s) in RCA: 83] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Affiliation(s)
- Ron Simkovitch
- Raymond
and Beverly Sackler
Faculty of Exact Sciences, School of Chemistry, Tel Aviv University, Tel Aviv 69978, Israel
| | - Shay Shomer
- Raymond
and Beverly Sackler
Faculty of Exact Sciences, School of Chemistry, Tel Aviv University, Tel Aviv 69978, Israel
| | - Rinat Gepshtein
- Raymond
and Beverly Sackler
Faculty of Exact Sciences, School of Chemistry, Tel Aviv University, Tel Aviv 69978, Israel
| | - Dan Huppert
- Raymond
and Beverly Sackler
Faculty of Exact Sciences, School of Chemistry, Tel Aviv University, Tel Aviv 69978, Israel
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20
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Wineman-Fisher V, Simkovitch R, Shomer S, Gepshtein R, Huppert D, Saif M, Kallio K, Remington SJ, Miller Y. Insight into the structure and the mechanism of the slow proton transfer in the GFP double mutant T203V/S205A. Phys Chem Chem Phys 2014; 16:11196-208. [PMID: 24776960 DOI: 10.1039/c4cp00311j] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Mutations near the fluorescing chromophore of the green fluorescent protein (GFP) have direct effects on the absorption and emission spectra. Some mutants have significant band shifts and most of the mutants exhibit a loss of fluorescence intensity. In this study we continue our investigation of the factors controlling the excited state proton transfer (PT) process of GFP, in particular to study the effects of modifications to the key side chain Ser205 in wt-GFP, proposed to participate in the proton wire. To this aim we combined mutagenesis, X-ray crystallography, steady-state spectroscopy, time-resolved emission spectroscopy and all-atom explicit molecular dynamics (MD) simulations to study the double mutant T203V/S205A. Our results show that while in the previously described GFP double mutant T203V/S205V the PT process does not occur, in the T203V/S205A mutant the PT process does occur, but with a 350 times slower rate than in wild-type GFP (wt-GFP). Furthermore, the kinetic isotope effect in the GFP double mutant T203V/S205A is twice smaller than in the wt-GFP and in the GFP single mutant S205V, which forms a novel PT pathway. On the other hand, the crystal structure of GFP T203V/S205A does not reveal a viable proton transfer pathway. To explain PT in GFP T203V/S205A, we argue on the basis of the MD simulations for an alternative, novel proton-wire pathway which involves the phenol group of the chromophore and water molecules infrequently entering from the bulk. This alternative pathway may explain the dramatically slow PT in the GFP double mutant T203V/S205A compared to wt-GFP.
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Affiliation(s)
- Vered Wineman-Fisher
- Department of Chemistry, Ben-Gurion University of the Negev, P.O. Box 653, Be'er Sheva 84105, Israel.
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