1
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Antolini C, Jacoby DJ, Tiano SM, Otolski CJ, Doumy G, March AM, Walko DA, Goodwill JE, Hayes D. Ten-Fold Solvent Kinetic Isotope Effect for the Nonradiative Relaxation of the Aqueous Ferrate(VI) Ion. J Phys Chem A 2023. [PMID: 38029389 DOI: 10.1021/acs.jpca.3c06042] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2023]
Abstract
Hypervalent iron intermediates have been invoked in the catalytic cycles of many metalloproteins, and thus, it is crucial to understand how the coupling between such species and their environment can impact their chemical and physical properties in such contexts. In this work, we take advantage of the solvent kinetic isotope effect (SKIE) to gain insight into the nonradiative deactivation of electronic excited states of the aqueous ferrate(VI) ion. We observe an exceptionally large SKIE of 9.7 for the nanosecond-scale relaxation of the lowest energy triplet ligand field state to the ground state. Proton inventory studies demonstrate that a single solvent O-H bond is coupled to the ion during deactivation, likely due to the sparse vibrational structure of ferrate(VI). Such a mechanism is consistent with that reported for the deactivation of f-f excited states of aqueous trivalent lanthanides, which exhibit comparably large SKIE values. This phenomenon is ascribed entirely to dissipation of energy into a higher overtone of a solvent acceptor mode, as any impact on the apparent relaxation rate due to a change in solvent viscosity is negligible.
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Affiliation(s)
- Cali Antolini
- Department of Chemistry, University of Rhode Island, Kingston, Rhode Island 02881, United States
| | - Danielle J Jacoby
- Department of Chemistry, University of Rhode Island, Kingston, Rhode Island 02881, United States
| | - Sophia M Tiano
- Department of Chemistry, University of Rhode Island, Kingston, Rhode Island 02881, United States
| | - Christopher J Otolski
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439, United States
| | - Gilles Doumy
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439, United States
| | - Anne Marie March
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, Illinois 60439, United States
| | - Donald A Walko
- Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, United States
| | - Joseph E Goodwill
- Department of Civil and Environmental Engineering, University of Rhode Island, Kingston, Rhode Island 02881, United States
| | - Dugan Hayes
- Department of Chemistry, University of Rhode Island, Kingston, Rhode Island 02881, United States
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2
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Gates C, Ananyev G, Roy-Chowdhury S, Fromme P, Dismukes GC. Regulation of light energy conversion between linear and cyclic electron flow within photosystem II controlled by the plastoquinone/quinol redox poise. PHOTOSYNTHESIS RESEARCH 2023; 156:113-128. [PMID: 36436152 DOI: 10.1007/s11120-022-00985-w] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/31/2022] [Accepted: 11/09/2022] [Indexed: 06/16/2023]
Abstract
Ultrapurified Photosystem II complexes crystalize as uniform microcrystals (PSIIX) of unprecedented homogeneity that allow observation of details previously unachievable, including the longest sustained oscillations of flash-induced O2 yield over > 200 flashes and a novel period-4.7 water oxidation cycle. We provide new evidence for a molecular-based mechanism for PSII-cyclic electron flow that accounts for switching from linear to cyclic electron flow within PSII as the downstream PQ/PQH2 pool reduces in response to metabolic needs and environmental input. The model is supported by flash oximetry of PSIIX as the LEF/CEF switch occurs, Fourier analysis of O2 flash yields, and Joliot-Kok modeling. The LEF/CEF switch rebalances the ratio of reductant energy (PQH2) to proton gradient energy (H+o/H+i) created by PSII photochemistry. Central to this model is the requirement for a regulatory site (QC) with two redox states in equilibrium with the dissociable secondary electron carrier site QB. Both sites are controlled by electrons and protons. Our evidence fits historical LEF models wherein light-driven water oxidation delivers electrons (from QA-) and stromal protons through QB to generate plastoquinol, the terminal product of PSII-LEF in vivo. The new insight is the essential regulatory role of QC. This site senses both the proton gradient (H+o/H+i) and the PQ pool redox poise via e-/H+ equilibration with QB. This information directs switching to CEF upon population of the protonated semiquinone in the Qc site (Q-H+)C, while the WOC is in the reducible S2 or S3 states. Subsequent photochemical primary charge separation (P+QA-) forms no (QH2)B, but instead undergoes two-electron backward transition in which the QC protons are pumped into the lumen, while the electrons return to the WOC forming (S1/S2). PSII-CEF enables production of additional ATP needed to power cellular processes including the terminal carboxylation reaction and in some cases PSI-dependent CEF.
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Affiliation(s)
- Colin Gates
- Dept of Chemistry & Chemical Biology, Rutgers University, Piscataway, USA
- Waksman Institute of Microbiology, Rutgers University, Piscataway, USA
- Dept of Computational Biology & Molecular Biophysics, Rutgers University, Piscataway, NJ, USA
- Dept of Chemistry and Biochemistry, Loyola University Chicago, Chicago, IL, USA
| | - Gennady Ananyev
- Dept of Chemistry & Chemical Biology, Rutgers University, Piscataway, USA
- Waksman Institute of Microbiology, Rutgers University, Piscataway, USA
| | - Shatabdi Roy-Chowdhury
- Center for Applied Structural Discovery, Biodesign Institute, Arizona State University, Tempe, AZ, USA
| | - Petra Fromme
- Center for Applied Structural Discovery, Biodesign Institute, Arizona State University, Tempe, AZ, USA
| | - G Charles Dismukes
- Dept of Chemistry & Chemical Biology, Rutgers University, Piscataway, USA.
- Waksman Institute of Microbiology, Rutgers University, Piscataway, USA.
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3
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Tadokoro M, Itoh M, Nishimura R, Sekiguchi K, Hoshino N, Kamebuchi H, Miyazaki J, Kobayashi F, Mizuno M, Akutagawa T. Proton Conduction at High Temperature in High‐Symmetry Hydrogen‐Bonded Molecular Crystals of Ru
III
Complexes with Six Imidazole‐Imidazolate Ligands. Chemistry 2022; 28:e202201397. [PMID: 35760750 PMCID: PMC9545294 DOI: 10.1002/chem.202201397] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2022] [Indexed: 11/06/2022]
Affiliation(s)
- Makoto Tadokoro
- Department of Chemistry Faculty of Science Tokyo University of Science Kagurazaka 1–3 Shinjuku-ku Tokyo 162-8601 Japan
| | - Masaki Itoh
- Department of Chemistry Faculty of Science Tokyo University of Science Kagurazaka 1–3 Shinjuku-ku Tokyo 162-8601 Japan
| | - Ryota Nishimura
- Department of Chemistry Faculty of Science Tokyo University of Science Kagurazaka 1–3 Shinjuku-ku Tokyo 162-8601 Japan
| | - Kensuke Sekiguchi
- Department of Chemistry Faculty of Science Tokyo University of Science Kagurazaka 1–3 Shinjuku-ku Tokyo 162-8601 Japan
| | - Norihisa Hoshino
- Institute of Multidisciplinary Research for Advanced Materials (IMRAM) Tohoku University Katahira, 2–1-1, Aoba-ku Sendai 980-8577 Japan
| | - Hajime Kamebuchi
- Department of Chemistry College of Humanities and Sciences Nihon University Sakurajyosui 3–25-40 Setagaya-ku Tokyo 156-8550 Japan
| | - Jun Miyazaki
- Department of Natural Sciences School of Engineering Tokyo Denki University Senjuasahi-cho 5 Adachi-ku Tokyo 120-8551 Japan
| | - Fumiya Kobayashi
- Department of Chemistry Faculty of Science Tokyo University of Science Kagurazaka 1–3 Shinjuku-ku Tokyo 162-8601 Japan
| | - Motohiro Mizuno
- Graduate School of Natural Science and Technology Kanazawa University Kanazawa 920-1192 Japan
| | - Tomoyuki Akutagawa
- Institute of Multidisciplinary Research for Advanced Materials (IMRAM) Tohoku University Katahira, 2–1-1, Aoba-ku Sendai 980-8577 Japan
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4
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Kang X, Chen Z, Zhou Z, Zhou Y, Tang S, Zhang Y, Zhang T, Ding B, Zhong D. Direct Observation of Ultrafast Proton Rocking in the BLUF Domain. Angew Chem Int Ed Engl 2022. [DOI: 10.1002/ange.202114423] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Xiu‐Wen Kang
- Center for Ultrafast Science and Technology School of Chemistry and Chemical Engineering Shanghai Jiao Tong University Shanghai 200240 China
| | - Zijing Chen
- Center for Ultrafast Science and Technology School of Chemistry and Chemical Engineering Shanghai Jiao Tong University Shanghai 200240 China
| | - Zhongneng Zhou
- Center for Ultrafast Science and Technology School of Chemistry and Chemical Engineering Shanghai Jiao Tong University Shanghai 200240 China
| | - Yalin Zhou
- Center for Ultrafast Science and Technology School of Chemistry and Chemical Engineering Shanghai Jiao Tong University Shanghai 200240 China
| | - Siwei Tang
- Center for Ultrafast Science and Technology School of Chemistry and Chemical Engineering Shanghai Jiao Tong University Shanghai 200240 China
| | - Yifei Zhang
- Center for Ultrafast Science and Technology School of Chemistry and Chemical Engineering Shanghai Jiao Tong University Shanghai 200240 China
| | - Tianyi Zhang
- Center for Ultrafast Science and Technology School of Chemistry and Chemical Engineering Shanghai Jiao Tong University Shanghai 200240 China
| | - Bei Ding
- Center for Ultrafast Science and Technology School of Chemistry and Chemical Engineering Shanghai Jiao Tong University Shanghai 200240 China
| | - Dongping Zhong
- Center for Ultrafast Science and Technology School of Chemistry and Chemical Engineering Shanghai Jiao Tong University Shanghai 200240 China
- Department of Physics Department of Chemistry and Biochemistry and Programs of Biophysics Chemical Physics, and Biochemistry The Ohio State University Columbus OH 43210 USA
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5
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Ding B, Kang XW, Chen Z, Zhou Z, Zhou Y, Tang S, Zhang Y, Zhang T, Zhong D. Direct Observation of Ultrafast Proton Rocking in the BLUF Domain. Angew Chem Int Ed Engl 2021; 61:e202114423. [PMID: 34927328 DOI: 10.1002/anie.202114423] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2021] [Indexed: 11/10/2022]
Abstract
We present direct observation of ultrafast proton rocking in the central motif of a BLUF domain protein scaffold. The mutant design has taken considerations of modulating the proton-coupled electron transfer (PCET) driving forces by replacing Tyr in the original motif with Trp, as well as of removing the interference of a competing electron transfer pathway. Using femtosecond pump-probe spectroscopy and detailed kinetics analysis, we resolved an electron-transfer-coupled Grotthuss-type forward and reversed proton rocking along the FMN-Gln-Trp proton relay chain. The rates of forward and reversed proton transfer are determined to be very close, namely 51 ps vs 52 ps. The kinetic isotope effect (KIE) constants associated with the forward and reversed proton transfer are 3.9 and 5.3, respectively. The observation of ultrafast proton rocking is not only a crucial step towards revealing the nature of proton relay in BLUF domain, but also provides a new paradigm of proton transfer in proteins for theoretical investigations.
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Affiliation(s)
- Bei Ding
- Shanghai Jiao Tong University, School of Chemistry and Chemical Engineering, 800 Dongchuan Road, 200240, Shanghai, CHINA
| | - Xiu-Wen Kang
- Shanghai Jiao Tong University, School of Chemistry and Chemical Engineering, CHINA
| | - Zijing Chen
- Shanghai Jiao Tong University, School of Chemistry and Chemical Engineering, CHINA
| | - Zhongneng Zhou
- Shanghai Jiao Tong University, School of Chemistry and Chemical Engineering, CHINA
| | - Yalin Zhou
- Shanghai Jiao Tong University, School of Chemistry and Chemical Engineering, CHINA
| | - Siwei Tang
- Shanghai Jiao Tong University, School of Chemistry and Chemical Engineering, CHINA
| | - Yifei Zhang
- Shanghai Jiao Tong University, School of Chemistry and Chemical Engineering, CHINA
| | - Tianyi Zhang
- Shanghai Jiao Tong University, School of Chemistry and Chemical Engineering, CHINA
| | - Dongping Zhong
- The Ohio State University, Department of Chemical and Biomolecular Engineering, CHINA
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6
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Weitkamp RF, Neumann B, Stammler H, Hoge B. Non-coordinated and Hydrogen Bonded Phenolate Anions as One-Electron Reducing Agents. Chemistry 2021; 27:6465-6478. [PMID: 33368714 PMCID: PMC8247865 DOI: 10.1002/chem.202005123] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2020] [Revised: 12/22/2020] [Indexed: 11/29/2022]
Abstract
In this work, the syntheses of non-coordinated electron-rich phenolate anions via deprotonation of the corresponding alcohols with an extremely powerful perethyl tetraphosphazene base (Schwesinger base) are reported. The application of uncharged phosphazenes renders the selective preparation of anionic phenol-phenolate and phenolate hydrates possible, which allows for the investigation of hydrogen bonding in these species. Hydrogen bonding brings about decreased redox potentials relative to the corresponding non-coordinated phenolate anions. The latter show redox potentials of up to -0.72(1) V vs. SCE, which is comparable to that of zinc metal, thus qualifying their application as organic zinc mimics. We utilized phenolates as reducing agents for the generation of radical anions in addition to the corresponding phenoxyl radicals. A tetracyanoethylene radical anion salt was synthesized and fully characterized as a representative example. We also present the activation of sulfur hexafluoride (SF6 ) with phenolates in a SET reaction, in which the nature of the respective phenolate determines whether simple fluorides or pentafluorosulfanide ([SF5 ]- ) salts are formed.
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Affiliation(s)
- Robin F. Weitkamp
- Centrum für Molekulare MaterialienFakultät für ChemieUniversität BielefeldUniversitätsstraße 2533615BielefeldGermany
| | - Beate Neumann
- Centrum für Molekulare MaterialienFakultät für ChemieUniversität BielefeldUniversitätsstraße 2533615BielefeldGermany
| | - Hans‐Georg Stammler
- Centrum für Molekulare MaterialienFakultät für ChemieUniversität BielefeldUniversitätsstraße 2533615BielefeldGermany
| | - Berthold Hoge
- Centrum für Molekulare MaterialienFakultät für ChemieUniversität BielefeldUniversitätsstraße 2533615BielefeldGermany
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7
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Abstract
In neutral medium (pH 7.0) [RuIIIRuII(µ-CO3)4(OH)]4− undergoes one electron oxidation to form [RuIIIRuIII(µ-CO3)4(OH)2]4− at an E1/2 of 0.85 V vs. NHE followed by electro-catalytic water oxidation at a potential ≥1.5 V. When the same electrochemical measurements are performed in bicarbonate medium (pH 8.3), the complex first undergoes one electron oxidation at an Epa of 0.86 V to form [RuIIIRuIII(µ-CO3)4(OH)2]4−. This complex further undergoes two step one electron oxidations to form RuIVRuIII and RuIVRuIV species at potentials (Epa) 1.18 and 1.35 V, respectively. The RuIVRuIII and RuIVRuIV species in bicarbonate solutions are [RuIVRuIII(µ-CO3)4(OH)(CO3)]4− and [RuIVRuIV(µ-CO3)4(O)(CO3)]4− based on density functional theory (DFT) calculations. The formation of HCO4− in the course of the oxidation has been demonstrated by DFT. The catalyst acts as homogeneous water oxidation catalyst, and after long term chronoamperometry, the absorption spectra does not change significantly. Each step has been found to follow a proton coupled electron transfer process (PCET) as obtained from the pH dependent studies. The catalytic current is found to follow linear relation with the concentration of the catalyst and bicarbonate. Thus, bicarbonate is involved in the catalytic process that is also evident from the generation of higher oxidation peaks in cyclic voltammetry. The detailed mechanism has been derived by DFT. A catalyst with no organic ligands has the advantage of long-time stability.
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8
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Mardis KL, Niklas J, Omodayo H, Odella E, Moore TA, Moore AL, Poluektov OG. One Electron Multiple Proton Transfer in Model Organic Donor-Acceptor Systems: Implications for High Frequency EPR. APPLIED MAGNETIC RESONANCE 2020; 51:977-991. [PMID: 34764625 PMCID: PMC8579843 DOI: 10.1007/s00723-020-01252-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/26/2020] [Revised: 08/03/2020] [Indexed: 06/12/2023]
Abstract
EPR spectroscopy is an important spectroscopic method for identification and characterization of radical species involved in many biological reactions. The tyrosyl radical is one of the most studied amino acid radical intermediates in biology. Often in conjunction with histidine residues, it is involved in many fundamental biological electron and proton transfer processes, such as in the water oxidation in photosystem II. As biological processes are typically extremely complicated and hard to control, molecular bio-mimetic model complexes are often used to clarify the mechanisms of the biological reactions. Here we present theoretical calculations to investigate the sensitivity of magnetic resonance parameters to proton-coupled electron transfer events, as well as conformational substates of the molecular constructs which mimic the tyrosine-histidine (Tyr-His) pairs found in a large variety of proteins. Upon oxidation of the phenol, the Tyr analogue, these complexes can perform not only one-electron one-proton transfer (EPT), but also one-electron two-proton transfers (E2PT). It is shown that in aprotic environment the gX-components of the electronic g-tensor are extremely sensitive to the first proton transfer from the phenoxyl oxygen to the imidazole nitrogen (EPT product), leading to a significant increase of the gX-value of up to 0.003, but are not sensitive to the second proton transfer (E2PT product). In the latter case the change of the gX-value is much smaller (ca. 0.0001), which is too small to be distinguished even by high frequency EPR. The 14N hyperfine values are also too similar to allow differentiation between the different protonation states in EPT and E2PT. The magnetic resonance parameters were also calculated as a function of the rotation angles around single bonds. It was demonstrated that rotation of the phenoxyl group results in large positive changes (>0.001) in the gX-values. Analysis of the data reveals that the main source of these changes is related to the strength of the H-bond between phenoxyl oxygen and the proton(s) on N1 and N2 positions of the imidazole.
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Affiliation(s)
- Kristy L Mardis
- Department of Chemistry, Physics, and Engineering Studies, Chicago State University, Chicago, Illinois 60628, USA
| | - Jens Niklas
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont, Illinois 60439, USA
| | - Harriet Omodayo
- Department of Chemistry, Physics, and Engineering Studies, Chicago State University, Chicago, Illinois 60628, USA
| | - Emmanuel Odella
- School of Molecular Sciences, Arizona State University, Tempe, Arizona, 85287, USA
| | - Thomas A Moore
- School of Molecular Sciences, Arizona State University, Tempe, Arizona, 85287, USA
| | - Ana L Moore
- School of Molecular Sciences, Arizona State University, Tempe, Arizona, 85287, USA
| | - Oleg G Poluektov
- Chemical Sciences and Engineering Division, Argonne National Laboratory, Lemont, Illinois 60439, USA
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9
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Brugh AM, Forbes MDE. Anomalous chemically induced electron spin polarization in proton-coupled electron transfer reactions: insight into radical pair dynamics. Chem Sci 2020; 11:6268-6274. [PMID: 32953022 PMCID: PMC7480077 DOI: 10.1039/d0sc02691c] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2020] [Accepted: 05/27/2020] [Indexed: 11/21/2022] Open
Abstract
Time-resolved electron paramagnetic resonance (TREPR) spectroscopy has been used to study the proton coupled electron transfer (PCET) reaction between a ruthenium complex (Ru(bpz)(bpy)2) and several substituted hydroquinones (HQ). After excitation at 355 nm, the HQ moiety forms a strong hydrogen bond to the exposed N atoms in the bpz heterocycle. At some point afterwards, a PCET reaction takes place in which an electron from the O atom of the hydrogen bond transfers to the metal center, and the proton forming the hydrogen bond remains on the bpz ligand N atom. The result is a semiquinone radical (HQ˙), whose TREPR spectrum is strongly polarized by the triplet mechanism (TM) of chemically induced dynamic electron spin polarization (CIDEP). Closer examination of the CIDEP pattern reveals, in some cases, a small amount of radical pair mechanism (RPM) polarization. We hypothesize that when the HQ moiety has electron donating groups (EDGs) substituted on the ring, S-T- RPM polarization is observed in HQ˙. These anomalous intensities are accounted for by spectral simulation using polarization from S-T- mixing. The generation of S-T- RPM is attributed to slow radical separation after PCET due to stabilization of the positive charge on the ring by EDGs. Results from a temperature dependence support the hypothesis.
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Affiliation(s)
- Alexander M Brugh
- Department of Chemistry , Center for Photochemical Sciences , Bowling Green State University , Bowling Green , OH 43403 , USA .
| | - Malcolm D E Forbes
- Department of Chemistry , Center for Photochemical Sciences , Bowling Green State University , Bowling Green , OH 43403 , USA .
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10
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Offenbacher AR, Barry BA. A Proton Wire Mediates Proton Coupled Electron Transfer from Hydroxyurea and Other Hydroxamic Acids to Tyrosyl Radical in Class Ia Ribonucleotide Reductase. J Phys Chem B 2020; 124:345-354. [PMID: 31904962 DOI: 10.1021/acs.jpcb.9b08587] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Proton-coupled electron transfer (PCET) is fundamental to many important biological reactions, including solar energy conversion and DNA synthesis. For example, class Ia ribonucleotide reductases (RNRs) contain a tyrosyl radical-diiron cofactor with one aspartate ligand, D84. The tyrosyl radical, Y122•, in the β2 subunit acts as a radical initiator and oxidizes an active site cysteine in the α2 subunit. A transient quaternary α2/β2 complex is induced by substrate and effector binding. The hydroxamic acid, hydroxyurea (HU), reduces Y122• in a PCET reaction involving an electron and proton. This reaction is associated with the loss of activity, a conformational change at Y122, and a change in hydrogen bonding to the Fe1 ligand, D84. Here, we use isotopic labeling, solvent isotope exchange, proton inventories, and reaction-induced Fourier transform infrared (RIFT-IR) spectroscopy to show that the PCET reactions of hydroxamic acids are associated with a characteristic spectrum, which is assignable to electrostatic changes at nonligating aspartate residues. Notably, RIFT-IR spectroscopy reveals this characteristic spectrum when the effects of HU, hydroxylamine, and N-methylhydroxylamine are compared. A large solvent isotope effect is observed for each of the hydroxamic acid reactions, and proton inventories predict that the reactions are associated with the transfer of multiple protons in the transition state. The reduction of Y122• with 4-methoxyphenol does not lead to these characteristic carboxylate shifts and is associated with only a small solvent isotope effect. In addition to studies of the effects of hydroxamic acids on β2 alone, the reactions involving the quaternary α2β2 complex were also investigated. HU treatment of the quaternary complex, α2/β2/ATP/CDP, leads to a similar carboxylate shift spectrum, as observed with β2 alone. The use of globally labeled 13C chimeras (13C α2, 13C β2) confirms the assignment. Because the spectrum is sensitive to 13C β2 labeling, but not 13C α2 labeling, the quaternary complex spectrum is assigned to electrostatic changes in β2 carboxylate groups. Examination of the β2 X-ray structure reveals a hydrogen-bonded network leading from the protein surface to Y122. This predicted network includes nonligating aspartates, glutamate ligands to the iron cluster, and predicted crystallographically resolved water molecules. The network is similar when class Ia RNR structures from Escherichia coli, human, and mouse are compared. We propose that the PCET reactions of hydroxamic acids are mediated by a hydrogen-bonded proton wire in the β2 subunit.
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Affiliation(s)
- Adam R Offenbacher
- Department of Chemistry and Biochemistry and the Petit Institute for Bioengineering and Bioscience , Georgia Institute of Technology , Atlanta , Georgia 30332 , United States.,Department of Chemistry , East Carolina University , Greenville , North Carolina 27858 , United States
| | - Bridgette A Barry
- Department of Chemistry and Biochemistry and the Petit Institute for Bioengineering and Bioscience , Georgia Institute of Technology , Atlanta , Georgia 30332 , United States
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11
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Specific metallo-protein interactions and antimicrobial activity in Histatin-5, an intrinsically disordered salivary peptide. Sci Rep 2019; 9:17303. [PMID: 31754129 PMCID: PMC6872563 DOI: 10.1038/s41598-019-52676-7] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2019] [Accepted: 10/10/2019] [Indexed: 02/06/2023] Open
Abstract
Histatin-5 (Hst-5) is an antimicrobial, salivary protein that is involved in the host defense system. Hst-5 has been proposed to bind functionally relevant zinc and copper but presents challenges in structural studies due to its disordered conformation in aqueous solution. Here, we used circular dichroism (CD) and UV resonance Raman (UVRR) spectroscopy to define metallo-Hst-5 interactions in aqueous solution. A zinc-containing Hst-5 sample exhibits shifted Raman bands, relative to bands observed in the absence of zinc. Based on comparison to model compounds and to a family of designed, zinc-binding beta hairpins, the alterations in the Hst-5 UVRR spectrum are attributed to zinc coordination by imidazole side chains. Zinc addition also shifted a tyrosine aromatic ring UVRR band through an electrostatic interaction. Copper addition did not have these effects. A sequence variant, H18A/H19A, was employed; this mutant has less potent antifungal activity, when compared to Hst-5. Zinc addition had only a small effect on the thermal stability of this mutant. Interestingly, both zinc and copper addition shifted histidine UVRR bands in a manner diagnostic for metal coordination. Results obtained with a K13E/R22G mutant were similar to those obtained with wildtype. These experiments show that H18 and H19 contribute to a zinc binding site. In the H18A/H19A mutant the specificity of the copper/zinc binding sites is lost. The experiments implicate specific zinc binding to be important in the antimicrobial activity of Hst-5.
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12
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Yang X, Bennett B, Holz RC. Insights into the catalytic mechanism of a bacterial hydrolytic dehalogenase that degrades the fungicide chlorothalonil. J Biol Chem 2019; 294:13411-13420. [PMID: 31331935 DOI: 10.1074/jbc.ra119.009094] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2019] [Revised: 07/17/2019] [Indexed: 11/06/2022] Open
Abstract
Chlorothalonil (2,4,5,6-tetrachloroisophtalonitrile; TPN) is one of the most commonly used fungicides in the United States. Given TPN's widespread use, general toxicity, and potential carcinogenicity, its biodegradation has garnered significant attention. Here, we developed a direct spectrophotometric assay for the Zn(II)-dependent, chlorothalonil-hydrolyzing dehalogenase from Pseudomonas sp. CTN-3 (Chd), enabling determination of its metal-binding properties; pH dependence of the kinetic parameters k cat, Km , and k cat/Km ; and solvent isotope effects. We found that a single Zn(II) ion binds a Chd monomer with a Kd of 0.17 μm, consistent with inductively coupled plasma MS data for the as-isolated Chd dimer. We observed that Chd was maximally active toward chlorothalonil in the pH range 7.0-9.0, and fits of these data yielded a pK ES1 of 5.4 ± 0.2, a pK ES2 of 9.9 ± 0.1 (k'cat = 24 ± 2 s-1), a pK E1 of 5.4 ± 0.3, and a pK E2 of 9.5 ± 0.1 (k'cat/k' m = 220 ± 10 s-1 mm-1). Proton inventory studies indicated that one proton is transferred in the rate-limiting step of the reaction at pD 7.0. Fits of UV-visible stopped-flow data suggested a three-step model and provided apparent rate constants for intermediate formation (i.e. a k'2 of 35.2 ± 0.1 s-1) and product release (i.e. a k'3 of 1.1 ± 0.2 s-1), indicating that product release is the slow step in catalysis. On the basis of these results, along with those previously reported, we propose a mechanism for Chd catalysis.
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Affiliation(s)
- Xinhang Yang
- Department of Chemistry, Marquette University, Milwaukee, Wisconsin 53201-1881
| | - Brian Bennett
- Department of Physics, Marquette University, Milwaukee, Wisconsin 53233
| | - Richard C Holz
- Department of Chemistry, Marquette University, Milwaukee, Wisconsin 53201-1881; Department of Chemistry, Colorado School of Mines, Golden, Colorado 80401.
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13
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Chen J, Chen J, Liu Y, Zheng Y, Zhu Q, Han G, Shen JR. Proton-Coupled Electron Transfer of Plastoquinone Redox Reactions in Photosystem II: A Pump-Probe Ultraviolet Resonance Raman Study. J Phys Chem Lett 2019; 10:3240-3247. [PMID: 31117681 DOI: 10.1021/acs.jpclett.9b00959] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Plastoquinones (PQs) act as electron and proton mediators in photosystem II (PSII) for solar-to-chemical energy conversion. It is known that the redox potential of PQ varies in a wide range spanning hundreds of millivolts; however, its structural origin is not known yet. Here, by developing a pump-probe ultraviolet resonance Raman technique, we measured the vibrational structures of PQs including QA and QB in cyanobacterial PSII directly. The conversion of QA to QA•- in the Mn-depleted PSII is verified by direct observation of the distinct QA•- vibrational bands. A frequency upshift of the ring C=O/C=C stretch band at 1565 cm-1 for QA•- was observed, which suggests a π-π interaction between the quinone ring and Trp253. In contrast, proton-coupled reduction of QA to QAH upon light-driven electron transfer is demonstrated in PSII without QB bound. The H-bond between QA and His214 is likely the proton origin of this proton-coupled electron transfer.
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Affiliation(s)
- Jun Chen
- Science and Technology on Surface Physics and Chemistry Laboratory , Jiangyou 621908 , China
- State Key Laboratory of Catalysis , Dalian Institute of Chemical Physics, Chinese Academy of Sciences , Dalian 116023 , China
| | - Jinfan Chen
- Science and Technology on Surface Physics and Chemistry Laboratory , Jiangyou 621908 , China
| | - Ying Liu
- Institute of Materials , China Academy of Engineering Physics , Mianyang 621907 , China
| | - Yang Zheng
- State Key Laboratory of Catalysis , Dalian Institute of Chemical Physics, Chinese Academy of Sciences , Dalian 116023 , China
| | - Qingjun Zhu
- Photosynthesis Research Center, Key Laboratory of Photobiology , Institute of Botany, Chinese Academy of Sciences , No. 20, Nanxincun , Xiangshan, Beijing , 100093 , China
| | - Guangye Han
- Photosynthesis Research Center, Key Laboratory of Photobiology , Institute of Botany, Chinese Academy of Sciences , No. 20, Nanxincun , Xiangshan, Beijing , 100093 , China
| | - Jian-Ren Shen
- Photosynthesis Research Center, Key Laboratory of Photobiology , Institute of Botany, Chinese Academy of Sciences , No. 20, Nanxincun , Xiangshan, Beijing , 100093 , China
- Research Institute of Interdisciplinary Science, Graduate School of Natural Science and Technology , Okayama University , Tsushima Naka 3-1-1 , Okayama 700-8530 , Japan
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14
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Sirohiwal A, Neese F, Pantazis DA. Microsolvation of the Redox-Active Tyrosine-D in Photosystem II: Correlation of Energetics with EPR Spectroscopy and Oxidation-Induced Proton Transfer. J Am Chem Soc 2019; 141:3217-3231. [PMID: 30666866 PMCID: PMC6728127 DOI: 10.1021/jacs.8b13123] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Photosystem II (PSII) of oxygenic photosynthesis captures sunlight to drive the catalytic oxidation of water and the reduction of plastoquinone. Among the several redox-active cofactors that participate in intricate electron transfer pathways there are two tyrosine residues, YZ and YD. They are situated in symmetry-related electron transfer branches but have different environments and play distinct roles. YZ is the immediate oxidant of the oxygen-evolving Mn4CaO5 cluster, whereas YD serves regulatory and protective functions. The protonation states and hydrogen-bond network in the environment of YD remain debated, while the role of microsolvation in stabilizing different redox states of YD and facilitating oxidation or mediating deprotonation, as well the fate of the phenolic proton, is unclear. Here we present detailed structural models of YD and its environment using large-scale quantum mechanical models and all-atom molecular dynamics of a complete PSII monomer. The energetics of water distribution within a hydrophobic cavity adjacent to YD are shown to correlate directly with electron paramagnetic resonance (EPR) parameters such as the tyrosyl g-tensor, allowing us to map the correspondence between specific structural models and available experimental observations. EPR spectra obtained under different conditions are explained with respect to the mode of interaction of the proximal water with the tyrosyl radical and the position of the phenolic proton within the cavity. Our results revise previous models of the energetics and build a detailed view of the role of confined water in the oxidation and deprotonation of YD. Finally, the model of microsolvation developed in the present work rationalizes in a straightforward way the biphasic oxidation kinetics of YD, offering new structural insights regarding the function of the radical in biological photosynthesis.
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Affiliation(s)
- Abhishek Sirohiwal
- Max-Planck-Institut für Kohlenforschung , Kaiser-Wilhelm-Platz 1 , 45470 Mülheim an der Ruhr , Germany
- Fakultät für Chemie und Biochemie , Ruhr-Universität Bochum , 44780 Bochum , Germany
| | - Frank Neese
- Max-Planck-Institut für Kohlenforschung , Kaiser-Wilhelm-Platz 1 , 45470 Mülheim an der Ruhr , Germany
| | - Dimitrios A Pantazis
- Max-Planck-Institut für Kohlenforschung , Kaiser-Wilhelm-Platz 1 , 45470 Mülheim an der Ruhr , Germany
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15
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N,N,O Pincer Ligand with a Deprotonatable Site That Promotes Redox‐Leveling, High Mn Oxidation States, and a Mn
2
O
2
Dimer Competent for Catalytic Oxygen Evolution. Eur J Inorg Chem 2019. [DOI: 10.1002/ejic.201801343] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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16
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Kang H, Tolbert TJ, Schöneich C. Photoinduced Tyrosine Side Chain Fragmentation in IgG4-Fc: Mechanisms and Solvent Isotope Effects. Mol Pharm 2018; 16:258-272. [DOI: 10.1021/acs.molpharmaceut.8b00979] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Affiliation(s)
- Huan Kang
- Department of Pharmaceutical Chemistry, University of Kansas, 2095 Constant Avenue, Lawrence, Kansas 66047, United States
| | - Thomas J. Tolbert
- Department of Pharmaceutical Chemistry, University of Kansas, 2095 Constant Avenue, Lawrence, Kansas 66047, United States
| | - Christian Schöneich
- Department of Pharmaceutical Chemistry, University of Kansas, 2095 Constant Avenue, Lawrence, Kansas 66047, United States
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17
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Chararalambidis G, Das S, Trapali A, Quaranta A, Orio M, Halime Z, Fertey P, Guillot R, Coutsolelos A, Leibl W, Aukauloo A, Sircoglou M. Water Molecules Gating a Photoinduced One-Electron Two-Protons Transfer in a Tyrosine/Histidine (Tyr/His) Model of Photosystem II. Angew Chem Int Ed Engl 2018. [DOI: 10.1002/ange.201804498] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Georgios Chararalambidis
- Laboratory of Bioinorganic Chemistry; Chemistry Department; University of Crete; PO Box 2208 71003 Heraklion Crete Greece
| | - Shyamal Das
- Institut des Sciences du vivant Frédéric Joliot/Institut de Biologie Intégrative de la Cellule, UMR 9198; CEA; CNRS; Université Paris Sud; Université Paris-Saclay; 91191 Gif-sur-Yvette France
| | - Adelais Trapali
- Laboratory of Bioinorganic Chemistry; Chemistry Department; University of Crete; PO Box 2208 71003 Heraklion Crete Greece
| | - Annamaria Quaranta
- Institut des Sciences du vivant Frédéric Joliot/Institut de Biologie Intégrative de la Cellule, UMR 9198; CEA; CNRS; Université Paris Sud; Université Paris-Saclay; 91191 Gif-sur-Yvette France
| | - Maylis Orio
- Aix Marseille Univ; iSm2; CNRS; Cent Marseille; 13397 Marseille France
| | - Zakaria Halime
- Institut de Chimie Moléculaire et des Matériaux d'Orsay, UMR 8182 CNRS; Université Paris Sud; Université Paris-Saclay; 91405 Orsay France
| | - Pierre Fertey
- Synchrotron SOLEIL; BP 48, L'Orme des Merisiers, Saint Aubin 91192 Gif-sur-Yvette Cedex France
| | - Régis Guillot
- Institut de Chimie Moléculaire et des Matériaux d'Orsay, UMR 8182 CNRS; Université Paris Sud; Université Paris-Saclay; 91405 Orsay France
| | - Athanassios Coutsolelos
- Laboratory of Bioinorganic Chemistry; Chemistry Department; University of Crete; PO Box 2208 71003 Heraklion Crete Greece
| | - Winfried Leibl
- Institut des Sciences du vivant Frédéric Joliot/Institut de Biologie Intégrative de la Cellule, UMR 9198; CEA; CNRS; Université Paris Sud; Université Paris-Saclay; 91191 Gif-sur-Yvette France
| | - Ally Aukauloo
- Institut de Chimie Moléculaire et des Matériaux d'Orsay, UMR 8182 CNRS; Université Paris Sud; Université Paris-Saclay; 91405 Orsay France
- Institut des Sciences du vivant Frédéric Joliot/Institut de Biologie Intégrative de la Cellule, UMR 9198; CEA; CNRS; Université Paris Sud; Université Paris-Saclay; 91191 Gif-sur-Yvette France
| | - Marie Sircoglou
- Institut de Chimie Moléculaire et des Matériaux d'Orsay, UMR 8182 CNRS; Université Paris Sud; Université Paris-Saclay; 91405 Orsay France
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18
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Chararalambidis G, Das S, Trapali A, Quaranta A, Orio M, Halime Z, Fertey P, Guillot R, Coutsolelos A, Leibl W, Aukauloo A, Sircoglou M. Water Molecules Gating a Photoinduced One-Electron Two-Protons Transfer in a Tyrosine/Histidine (Tyr/His) Model of Photosystem II. Angew Chem Int Ed Engl 2018; 57:9013-9017. [DOI: 10.1002/anie.201804498] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2018] [Indexed: 11/10/2022]
Affiliation(s)
- Georgios Chararalambidis
- Laboratory of Bioinorganic Chemistry; Chemistry Department; University of Crete; PO Box 2208 71003 Heraklion Crete Greece
| | - Shyamal Das
- Institut des Sciences du vivant Frédéric Joliot/Institut de Biologie Intégrative de la Cellule, UMR 9198; CEA; CNRS; Université Paris Sud; Université Paris-Saclay; 91191 Gif-sur-Yvette France
| | - Adelais Trapali
- Laboratory of Bioinorganic Chemistry; Chemistry Department; University of Crete; PO Box 2208 71003 Heraklion Crete Greece
| | - Annamaria Quaranta
- Institut des Sciences du vivant Frédéric Joliot/Institut de Biologie Intégrative de la Cellule, UMR 9198; CEA; CNRS; Université Paris Sud; Université Paris-Saclay; 91191 Gif-sur-Yvette France
| | - Maylis Orio
- Aix Marseille Univ; iSm2; CNRS; Cent Marseille; 13397 Marseille France
| | - Zakaria Halime
- Institut de Chimie Moléculaire et des Matériaux d'Orsay, UMR 8182 CNRS; Université Paris Sud; Université Paris-Saclay; 91405 Orsay France
| | - Pierre Fertey
- Synchrotron SOLEIL; BP 48, L'Orme des Merisiers, Saint Aubin 91192 Gif-sur-Yvette Cedex France
| | - Régis Guillot
- Institut de Chimie Moléculaire et des Matériaux d'Orsay, UMR 8182 CNRS; Université Paris Sud; Université Paris-Saclay; 91405 Orsay France
| | - Athanassios Coutsolelos
- Laboratory of Bioinorganic Chemistry; Chemistry Department; University of Crete; PO Box 2208 71003 Heraklion Crete Greece
| | - Winfried Leibl
- Institut des Sciences du vivant Frédéric Joliot/Institut de Biologie Intégrative de la Cellule, UMR 9198; CEA; CNRS; Université Paris Sud; Université Paris-Saclay; 91191 Gif-sur-Yvette France
| | - Ally Aukauloo
- Institut de Chimie Moléculaire et des Matériaux d'Orsay, UMR 8182 CNRS; Université Paris Sud; Université Paris-Saclay; 91405 Orsay France
- Institut des Sciences du vivant Frédéric Joliot/Institut de Biologie Intégrative de la Cellule, UMR 9198; CEA; CNRS; Université Paris Sud; Université Paris-Saclay; 91191 Gif-sur-Yvette France
| | - Marie Sircoglou
- Institut de Chimie Moléculaire et des Matériaux d'Orsay, UMR 8182 CNRS; Université Paris Sud; Université Paris-Saclay; 91405 Orsay France
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19
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Ahmadova N, Ho FM, Styring S, Mamedov F. Tyrozine D oxidation and redox equilibrium in photosystem II. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2017; 1858:407-417. [DOI: 10.1016/j.bbabio.2017.02.011] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/26/2016] [Revised: 02/17/2017] [Accepted: 02/20/2017] [Indexed: 10/20/2022]
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20
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Guo Z, Barry BA. Calcium, Ammonia, Redox-Active Tyrosine YZ, and Proton-Coupled Electron Transfer in the Photosynthetic Oxygen-Evolving Complex. J Phys Chem B 2017; 121:3987-3996. [DOI: 10.1021/acs.jpcb.7b01802] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Zhanjun Guo
- School of Chemistry and Biochemistry and Petit Institute for Bioengineering and Biosciences, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
| | - Bridgette A. Barry
- School of Chemistry and Biochemistry and Petit Institute for Bioengineering and Biosciences, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
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21
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Hwang H, McCaslin TG, Hazel A, Pagba CV, Nevin CM, Pavlova A, Barry BA, Gumbart JC. Redox-Driven Conformational Dynamics in a Photosystem-II-Inspired β-Hairpin Maquette Determined through Spectroscopy and Simulation. J Phys Chem B 2017; 121:3536-3545. [DOI: 10.1021/acs.jpcb.6b09481] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Affiliation(s)
- Hyea Hwang
- School
of Materials Science and Engineering, ‡School of Chemistry and Biochemistry, §Petit Institute for
Bioengineering and Biosciences, and ∥School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
| | - Tyler G. McCaslin
- School
of Materials Science and Engineering, ‡School of Chemistry and Biochemistry, §Petit Institute for
Bioengineering and Biosciences, and ∥School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
| | - Anthony Hazel
- School
of Materials Science and Engineering, ‡School of Chemistry and Biochemistry, §Petit Institute for
Bioengineering and Biosciences, and ∥School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
| | - Cynthia V. Pagba
- School
of Materials Science and Engineering, ‡School of Chemistry and Biochemistry, §Petit Institute for
Bioengineering and Biosciences, and ∥School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
| | - Christina M. Nevin
- School
of Materials Science and Engineering, ‡School of Chemistry and Biochemistry, §Petit Institute for
Bioengineering and Biosciences, and ∥School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
| | - Anna Pavlova
- School
of Materials Science and Engineering, ‡School of Chemistry and Biochemistry, §Petit Institute for
Bioengineering and Biosciences, and ∥School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
| | - Bridgette A. Barry
- School
of Materials Science and Engineering, ‡School of Chemistry and Biochemistry, §Petit Institute for
Bioengineering and Biosciences, and ∥School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
| | - James C. Gumbart
- School
of Materials Science and Engineering, ‡School of Chemistry and Biochemistry, §Petit Institute for
Bioengineering and Biosciences, and ∥School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
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22
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Ma Z, Williamson HR, Davidson VL. A Suicide Mutation Affecting Proton Transfers to High-Valent Hemes Causes Inactivation of MauG during Catalysis. Biochemistry 2016; 55:5738-5745. [PMID: 27622473 DOI: 10.1021/acs.biochem.6b00816] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
In the absence of its substrate, the autoreduction of the high-valent bis-FeIV state of the hemes of MauG to the diferric state proceeds via a Compound I-like and then a Compound II-like intermediate. This process is coupled to oxidative damage to specific methionine residues and inactivation of MauG. The autoreduction of a P107V MauG variant, which is more prone to oxidative damage, proceeds directly from the bis-FeIV to the Compound II-like state with no detectable Compound I intermediate. Comparison of the crystal structures of native and P107V MauG reveals that this mutation alters the positions of amino acid residues in the heme site as well as the water network that delivers protons from the solvent to the hemes during their reduction. Kinetic, spectroscopic, and solvent kinetic isotope effect studies demonstrate that these changes in the heme site affect the protonation state of the ferryl heme and the relative efficiencies of two alternative pathways for the transfer of protons from solvent to the hemes. These changes enhance the rate of autoreduction of P107V MauG such that it competes with the catalytic reaction with substrate and causes the enzyme to inactivate itself during the steady-state reaction with H2O2 and its substrate. Thus, while this mutation has negligible effects on the initial steady-state kinetic parameters of MauG, it is a fatal mutation as it causes inactivation during catalysis.
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Affiliation(s)
- Zhongxin Ma
- Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida , Orlando, Florida 32827, United States
| | - Heather R Williamson
- Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida , Orlando, Florida 32827, United States
| | - Victor L Davidson
- Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida , Orlando, Florida 32827, United States
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23
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Manbeck GF, Fujita E, Concepcion JJ. Proton-Coupled Electron Transfer in a Strongly Coupled Photosystem II-Inspired Chromophore–Imidazole–Phenol Complex: Stepwise Oxidation and Concerted Reduction. J Am Chem Soc 2016; 138:11536-49. [DOI: 10.1021/jacs.6b03506] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Gerald F. Manbeck
- Chemistry Division, Brookhaven National Laboratory, Upton, New York 11973-5000, United States
| | - Etsuko Fujita
- Chemistry Division, Brookhaven National Laboratory, Upton, New York 11973-5000, United States
| | - Javier J. Concepcion
- Chemistry Division, Brookhaven National Laboratory, Upton, New York 11973-5000, United States
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24
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Mechanism of protein oxidative damage that is coupled to long-range electron transfer to high-valent haems. Biochem J 2016; 473:1769-75. [PMID: 27076451 DOI: 10.1042/bcj20160047] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2016] [Accepted: 04/12/2016] [Indexed: 11/17/2022]
Abstract
In the absence of its substrate, the auto-reduction of the high-valent bis-Fe(IV) state of the dihaem enzyme MauG is coupled to oxidative damage of a methionine residue. Transient kinetic and solvent isotope effect studies reveal that this process occurs via two sequential long-range electron transfer (ET) reactions from methionine to the haems. The first ET is coupled to proton transfer (PT) to the haems from solvent via an ordered water network. The second ET is coupled to PT at the methionine site and occurs during the oxidation of the methionine to a sulfoxide. This process proceeds via Compound I- and Compound II-like haem intermediates. It is proposed that the methionine radical is stabilized by a two-centre three-electron (2c3e) bond. This provides insight into how oxidative damage to proteins may occur without direct contact with a reactive oxygen species, and how that damage can be propagated through the protein.
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25
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Pagba CV, McCaslin TG, Chi SH, Perry JW, Barry BA. Proton-Coupled Electron Transfer and a Tyrosine-Histidine Pair in a Photosystem II-Inspired β-Hairpin Maquette: Kinetics on the Picosecond Time Scale. J Phys Chem B 2016; 120:1259-72. [PMID: 26886811 DOI: 10.1021/acs.jpcb.6b00560] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Photosystem II (PSII) and ribonucleotide reductase employ oxidation and reduction of the tyrosine aromatic ring in radical transport pathways. Tyrosine-based reactions involve either proton-coupled electron transfer (PCET) or electron transfer (ET) alone, depending on the pH and the pKa of tyrosine's phenolic oxygen. In PSII, a subset of the PCET reactions are mediated by a tyrosine-histidine redox-driven proton relay, YD-His189. Peptide A is a PSII-inspired β-hairpin, which contains a single tyrosine (Y5) and histidine (H14). Previous electrochemical characterization indicated that Peptide A conducts a net PCET reaction between Y5 and H14, which have a cross-strand π-π interaction. The kinetic impact of H14 has not yet been explored. Here, we address this question through time-resolved absorption spectroscopy and 280-nm photolysis, which generates a neutral tyrosyl radical. The formation and decay of the neutral tyrosyl radical at 410 nm were monitored in Peptide A and its variant, Peptide C, in which H14 is replaced by cyclohexylalanine (Cha14). Significantly, both electron transfer (ET, pL 11, L = lyonium) and PCET (pL 9) were accelerated in Peptide A and C, compared to model tyrosinate or tyrosine at the same pL. Increased electronic coupling, mediated by the peptide backbone, can account for this rate acceleration. Deuterium exchange gave no significant solvent isotope effect in the peptides. At pL 9, but not at pL 11, the reaction rate decreased when H14 was mutated to Cha14. This decrease in rate is attributed to an increase in reorganization energy in the Cha14 mutant. The Y5-H14 mechanism in Peptide A is reminiscent of proton- and electron-transfer events involving YD-H189 in PSII. These results document a mechanism by which proton donors and acceptors can regulate the rate of PCET reactions.
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Affiliation(s)
- Cynthia V Pagba
- School of Chemistry and Biochemistry, the Petit Institute for Bioengineering and Bioscience, and the ‡Center for Organic Photonics and Electronics, Georgia Institute of Technology , Atlanta, Georgia 30332, United States
| | - Tyler G McCaslin
- School of Chemistry and Biochemistry, the Petit Institute for Bioengineering and Bioscience, and the ‡Center for Organic Photonics and Electronics, Georgia Institute of Technology , Atlanta, Georgia 30332, United States
| | - San-Hui Chi
- School of Chemistry and Biochemistry, the Petit Institute for Bioengineering and Bioscience, and the ‡Center for Organic Photonics and Electronics, Georgia Institute of Technology , Atlanta, Georgia 30332, United States
| | - Joseph W Perry
- School of Chemistry and Biochemistry, the Petit Institute for Bioengineering and Bioscience, and the ‡Center for Organic Photonics and Electronics, Georgia Institute of Technology , Atlanta, Georgia 30332, United States
| | - Bridgette A Barry
- School of Chemistry and Biochemistry, the Petit Institute for Bioengineering and Bioscience, and the ‡Center for Organic Photonics and Electronics, Georgia Institute of Technology , Atlanta, Georgia 30332, United States
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26
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Pagba CV, McCaslin TG, Veglia G, Porcelli F, Yohannan J, Guo Z, McDaniel M, Barry BA. A tyrosine-tryptophan dyad and radical-based charge transfer in a ribonucleotide reductase-inspired maquette. Nat Commun 2015; 6:10010. [PMID: 26627888 PMCID: PMC4686667 DOI: 10.1038/ncomms10010] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2015] [Accepted: 10/23/2015] [Indexed: 01/29/2023] Open
Abstract
In class 1a ribonucleotide reductase (RNR), a substrate-based radical is generated in the α2 subunit by long-distance electron transfer involving an essential tyrosyl radical (Y122O·) in the β2 subunit. The conserved W48 β2 is ∼10 Å from Y122OH; mutations at W48 inactivate RNR. Here, we design a beta hairpin peptide, which contains such an interacting tyrosine–tryptophan dyad. The NMR structure of the peptide establishes that there is no direct hydrogen bond between the phenol and the indole rings. However, electronic coupling between the tyrosine and tryptophan occurs in the peptide. In addition, downshifted ultraviolet resonance Raman (UVRR) frequencies are observed for the radical state, reproducing spectral downshifts observed for β2. The frequency downshifts of the ring and CO bands are consistent with charge transfer from YO· to W or another residue. Such a charge transfer mechanism implies a role for the β2 Y-W dyad in electron transfer. Tyrosine-tryptophan dyads are known to mediate electron transfer reactions in a range of different proteins. Here, the authors study a beta hairpin peptide, probing the tyrosine-tryptophan interaction and showing no hydrogen bonding but rather charge transfer between the tyrosyl radical and tryptophan'.
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Affiliation(s)
- Cynthia V Pagba
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332, USA.,Parker H. Petit Institute of Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, Georgia 30332, USA
| | - Tyler G McCaslin
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332, USA.,Parker H. Petit Institute of Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, Georgia 30332, USA
| | - Gianluigi Veglia
- Department of Biochemistry, Biophysics and Molecular Biology, University of Minnesota, Minneapolis, Minnesota 55455, USA.,Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455, USA
| | - Fernando Porcelli
- Department of Biochemistry, Biophysics and Molecular Biology, University of Minnesota, Minneapolis, Minnesota 55455, USA.,Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455, USA.,Department for Innovation in Biological, Agro-food and Forest Systems, University of Tuscia, Viterbo 01100, Italy
| | - Jiby Yohannan
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332, USA.,Parker H. Petit Institute of Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, Georgia 30332, USA
| | - Zhanjun Guo
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332, USA.,Parker H. Petit Institute of Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, Georgia 30332, USA
| | - Miranda McDaniel
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332, USA.,Parker H. Petit Institute of Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, Georgia 30332, USA
| | - Bridgette A Barry
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332, USA.,Parker H. Petit Institute of Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, Georgia 30332, USA
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27
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Roles of multiple-proton transfer pathways and proton-coupled electron transfer in the reactivity of the bis-FeIV state of MauG. Proc Natl Acad Sci U S A 2015; 112:10896-901. [PMID: 26283395 DOI: 10.1073/pnas.1510986112] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The high-valent state of the diheme enzyme MauG exhibits charge-resonance (CR) stabilization in which the major species is a bis-Fe(IV) state with one heme present as Fe(IV)=O and the other as Fe(IV) with axial heme ligands provided by His and Tyr side chains. In the absence of its substrate, the high-valent state is relatively stable and returns to the diferric state over several minutes. It is shown that this process occurs in two phases. The first phase is redistribution of the resonance species that support the CR. The second phase is the loss of CR and reduction to the diferric state. Thermodynamic analysis revealed that the rates of the two phases exhibited different temperature dependencies and activation energies of 8.9 and 19.6 kcal/mol. The two phases exhibited kinetic solvent isotope effects of 2.5 and 2.3. Proton inventory plots of each reaction phase exhibited extreme curvature that could not be fit to models for one- or multiple-proton transfers in the transition state. Each did fit well to a model for two alternative pathways for proton transfer, each involving multiple protons. In each case the experimentally determined fractionation factors were consistent with one of the pathways involving tunneling. The percent of the reaction that involved the tunneling pathway differed for the two reaction phases. Using the crystal structure of MauG it was possible to propose proton-transfer pathways consistent with the experimental data using water molecules and amino acid side chains in the distal pocket of the high-spin heme.
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Zhang Q, Liu Z, Zhai J. Photocurrent generation in a light-harvesting system with multifunctional artificial nanochannels. Chem Commun (Camb) 2015; 51:12286-9. [DOI: 10.1039/c5cc04271b] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Inspired by the biological light-driven proton pump, a light-harvesting system based on multifunctional artificial nanochannels is developed for photocurrent generation.
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Affiliation(s)
- Qianqian Zhang
- Key Laboratory of Bio-Inspired Smart Interfacial Science and Technology of Ministry of Education
- Beijing Key Laboratory of Bio-inspired Energy Materials and Devices
- School of Chemistry and Environment
- Beihang University
- Beijing 100191
| | - Zhaoyue Liu
- Key Laboratory of Bio-Inspired Smart Interfacial Science and Technology of Ministry of Education
- Beijing Key Laboratory of Bio-inspired Energy Materials and Devices
- School of Chemistry and Environment
- Beihang University
- Beijing 100191
| | - Jin Zhai
- Key Laboratory of Bio-Inspired Smart Interfacial Science and Technology of Ministry of Education
- Beijing Key Laboratory of Bio-inspired Energy Materials and Devices
- School of Chemistry and Environment
- Beihang University
- Beijing 100191
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29
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Pagba CV, Chi SH, Perry J, Barry BA. Proton-Coupled Electron Transfer in Tyrosine and a β-Hairpin Maquette: Reaction Dynamics on the Picosecond Time Scale. J Phys Chem B 2014; 119:2726-36. [DOI: 10.1021/jp510171z] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Cynthia V. Pagba
- School of Chemistry and Biochemistry, Petit Institute for Bioengineering
and Bioscience, and ‡Center of Organic Photonics and Electronics, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
| | - San-Hui Chi
- School of Chemistry and Biochemistry, Petit Institute for Bioengineering
and Bioscience, and ‡Center of Organic Photonics and Electronics, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
| | - Joseph Perry
- School of Chemistry and Biochemistry, Petit Institute for Bioengineering
and Bioscience, and ‡Center of Organic Photonics and Electronics, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
| | - Bridgette A. Barry
- School of Chemistry and Biochemistry, Petit Institute for Bioengineering
and Bioscience, and ‡Center of Organic Photonics and Electronics, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
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Barry BA. Reaction dynamics and proton coupled electron transfer: studies of tyrosine-based charge transfer in natural and biomimetic systems. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2014; 1847:46-54. [PMID: 25260243 DOI: 10.1016/j.bbabio.2014.09.003] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/09/2014] [Revised: 08/27/2014] [Accepted: 09/10/2014] [Indexed: 11/25/2022]
Abstract
In bioenergetic reactions, electrons are transferred long distances via a hopping mechanism. In photosynthesis and DNA synthesis, the aromatic amino acid residue, tyrosine, functions as an intermediate that is transiently oxidized and reduced during long distance electron transfer. At physiological pH values, oxidation of tyrosine is associated with a deprotonation of the phenolic oxygen, giving rise to a proton coupled electron transfer (PCET) reaction. Tyrosine-based PCET reactions are important in photosystem II, which carries out the light-induced oxidation of water, and in ribonucleotide reductase, which reduces ribonucleotides to form deoxynucleotides. Photosystem II contains two redox-active tyrosines, YD (Y160 in the D2 polypeptide) and YZ (Y161 in the D1 polypeptide). YD forms a light-induced stable radical, while YZ functions as an essential charge relay, oxidizing the catalytic Mn₄CaO₅ cluster on each of four photo-oxidation reactions. In Escherichia coli class 1a RNR, the β2 subunit contains the radical initiator, Y122O•, which is reversibly reduced and oxidized in long range electron transfer with the α2 subunit. In the isolated E. coli β2 subunit, Y122O• is a stable radical, but Y122O• is activated for rapid PCET in an α2β2 substrate/effector complex. Recent results concerning the structure and function of YD, YZ, and Y122 are reviewed here. Comparison is made to recent results derived from bioengineered proteins and biomimetic compounds, in which tyrosine-based charge transfer mechanisms have been investigated. This article is part of a Special Issue entitled: Vibrational spectroscopies and bioenergetic systems.
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Affiliation(s)
- Bridgette A Barry
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA 30332, USA; Petit Institute for Bioengineering and Biosciences, Georgia Institute of Technology, Atlanta, GA 30332, USA.
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Sjöholm J, Mamedov F, Styring S. Spectroscopic Evidence for a Redox-Controlled Proton Gate at Tyrosine D in Photosystem II. Biochemistry 2014; 53:5721-3. [DOI: 10.1021/bi5009672] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Johannes Sjöholm
- Molecular Biomimetics, Department
of Chemistry-Ångström Laboratory, Uppsala University, P.O. Box 523, SE-751 20 Uppsala, Sweden
| | - Fikret Mamedov
- Molecular Biomimetics, Department
of Chemistry-Ångström Laboratory, Uppsala University, P.O. Box 523, SE-751 20 Uppsala, Sweden
| | - Stenbjörn Styring
- Molecular Biomimetics, Department
of Chemistry-Ångström Laboratory, Uppsala University, P.O. Box 523, SE-751 20 Uppsala, Sweden
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32
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33
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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: 345] [Impact Index Per Article: 34.5] [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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34
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Offenbacher AR, Watson RA, Pagba CV, Barry BA. Redox-dependent structural coupling between the α2 and β2 subunits in E. coli ribonucleotide reductase. J Phys Chem B 2014; 118:2993-3004. [PMID: 24606240 DOI: 10.1021/jp501121d] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Ribonucleotide reductase (RNR) catalyzes the production of deoxyribonucleotides in all cells. In E. coli class Ia RNR, a transient α2β2 complex forms when a ribonucleotide substrate, such as CDP, binds to the α2 subunit. A tyrosyl radical (Y122O•)-diferric cofactor in β2 initiates substrate reduction in α2 via a long-distance, proton-coupled electron transfer (PCET) process. Here, we use reaction-induced FT-IR spectroscopy to describe the α2β2 structural landscapes, which are associated with dATP and hydroxyurea (HU) inhibition. Spectra were acquired after mixing E. coli α2 and β2 with a substrate, CDP, and the allosteric effector, ATP. Isotopic chimeras, (13)Cα2β2 and α2(13)Cβ2, were used to define subunit-specific structural changes. Mixing of α2 and β2 under turnover conditions yielded amide I (C═O) and II (CN/NH) bands, derived from each subunit. The addition of the inhibitor, dATP, resulted in a decreased contribution from amide I bands, attributable to β strands and disordered structures. Significantly, HU-mediated reduction of Y122O• was associated with structural changes in α2, as well as β2. To define the spectral contributions of Y122O•/Y122OH in the quaternary complex, (2)H4 labeling of β2 tyrosines and HU editing were performed. The bands of Y122O•, Y122OH, and D84, a unidentate ligand to the diferric cluster, previously identified in isolated β2, were observed in the α2β2 complex. These spectra also provide evidence for a conformational rearrangement at an additional β2 tyrosine(s), Yx, in the α2β2/CDP/ATP complex. This study illustrates the utility of reaction-induced FT-IR spectroscopy in the study of complex enzymes.
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Affiliation(s)
- Adam R Offenbacher
- School of Chemistry and Biochemistry and the Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology , Atlanta, Georgia 30332, United States
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35
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Megiatto Jr JD, Méndez-Hernández DD, Tejeda-Ferrari ME, Teillout AL, Llansola-Portolés MJ, Kodis G, Poluektov OG, Rajh T, Mujica V, Groy TL, Gust D, Moore TA, Moore AL. A bioinspired redox relay that mimics radical interactions of the Tyr–His pairs of photosystem II. Nat Chem 2014; 6:423-8. [DOI: 10.1038/nchem.1862] [Citation(s) in RCA: 119] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2013] [Accepted: 12/20/2013] [Indexed: 11/09/2022]
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36
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Bao H, Dilbeck PL, Burnap RL. Proton transport facilitating water-oxidation: the role of second sphere ligands surrounding the catalytic metal cluster. PHOTOSYNTHESIS RESEARCH 2013; 116:215-229. [PMID: 23975203 DOI: 10.1007/s11120-013-9907-1] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/29/2013] [Accepted: 08/03/2013] [Indexed: 06/02/2023]
Abstract
The ability of PSII to extract electrons from water, with molecular oxygen as a by-product, is a remarkable biochemical and evolutionary innovation. From an evolutionary perspective, the invention of PSII approximately 2.7 Ga led to the accelerated accumulation of biomass in the biosphere and the accumulation of oxygen in the atmosphere, a combination that allowed for the evolution of a much more complex and extensive biosphere than would otherwise have been possible. From the biochemical and enzymatic perspective, PSII is remarkable because of the thermodynamic and kinetic obstacles that needed to have been overcome to oxidize water as the ultimate photosynthetic electron donor. This article focuses on how proton release is an integral part of how these kinetic and thermodynamic obstacles have been overcome: the sequential removal of protons from the active site of H2O-oxidation facilitates the multistep oxidation of the substrate water at the Mn4CaOx, the catalytic heart of the H2O-oxidation reaction. As noted previously, the facilitated deprotonation of the Mn4CaOx cluster exerts a redox-leveling function preventing the accumulation of excess positive charge on the cluster, which might otherwise hinder the already energetically difficult oxidation of water. Using recent results, including the characteristics of site-directed mutants, the role of the second sphere of amino acid ligands and the associated network of water molecules surrounding the Mn4CaOx is discussed in relation to proton transport in other systems. In addition to the redox-leveling function, a trapping function is assigned to the proton release step occurring immediately prior to the dioxygen chemistry. This trapping appears to involve a yet-to-be clarified gating mechanism that facilitates to coordinated release of a proton from the neighborhood of the active site thereby insuring that the backward charge-recombination reaction does not out-compete the forward reaction of dioxygen chemistry during this final step of H2O-oxidation.
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Affiliation(s)
- Han Bao
- Department of Microbiology and Molecular Genetics, Oklahoma State University, 307 Life Sciences East, Stillwater, OK, 74078, USA
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37
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Offenbacher AR, Burns LA, Sherrill CD, Barry BA. Redox-linked conformational control of proton-coupled electron transfer: Y122 in the ribonucleotide reductase β2 subunit. J Phys Chem B 2013; 117:8457-68. [PMID: 23822111 DOI: 10.1021/jp404757r] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Tyrosyl radicals play essential roles in biological proton-coupled electron transfer (PCET) reactions. Ribonucleotide reductase (RNR) catalyzes the reduction of ribonucleotides and is vital in DNA replication in all organisms. Class Ia RNRs consist of α2 and β2 homodimeric subunits. In class Ia RNR, such as the E. coli enzyme, an essential tyrosyl radical (Y122O(•))-diferric cofactor is located in β2. Although Y122O(•) is extremely stable in free β2, Y122O(•) is highly reactive in the quaternary substrate-α2β2 complex and serves as a radical initiator in catalytic PCET between β2 and α2. In this report, we investigate the structural interactions that control the reactivity of Y122O(•) in a model system, isolated E. coli β2. Y122O(•) was reduced with hydroxyurea (HU), a radical scavenger that quenches the radical in a clinically relevant reaction. In the difference FT-IR spectrum, associated with this PCET reaction, amide I (CO) and amide II (CN/NH) bands were observed. Specific (13)C-labeling of the tyrosine C1 carbon assigned a component of these bands to the Y122-T123 amide bond. Comparison to density functional calculations on a model dipeptide, tyrosine-threonine, and structural modeling demonstrated that PCET is associated with a Y122 rotation and a 7.2 Å translation of the Y122 phenolic oxygen. To test for the functional consequences of this structural change, a proton inventory defined the origin of the large solvent isotope effect (SIE = 16.7 ± 1.0 at 25 °C) on this reaction. These data suggest that the one-electron, HU-mediated reduction of Y122O(•) is associated with two, rate-limiting (full or partial) proton transfer reactions. One is attributable to HU oxidation (SIE = 11.9, net H atom transfer), and the other is attributable to coupled, hydrogen-bonding changes in the Y122O(•)-diferric cofactor (SIE = 1.4). These results illustrate the importance of redox-linked changes to backbone and ring dihedral angles in high potential PCET and provide evidence for rate-limiting, redox-linked hydrogen-bonding interactions between Y122O(•) and the iron cluster.
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Affiliation(s)
- Adam R Offenbacher
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332, United States
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38
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Dong L, Wang Y, Lv Y, Chen Z, Mei F, Xiong H, Yin G. Lewis-Acid-Promoted Stoichiometric and Catalytic Oxidations by Manganese Complexes Having Cross-Bridged Cyclam Ligand: A Comprehensive Study. Inorg Chem 2013; 52:5418-27. [DOI: 10.1021/ic400361s] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Lei Dong
- School of Chemistry and Chemical Engineering, Hubei
Key Laboratory of Material Chemistry and Service Failure, Huazhong University of Science and Technology, Wuhan
430074, P.R. China
| | - Yujuan Wang
- School of Chemistry and Chemical Engineering, Hubei
Key Laboratory of Material Chemistry and Service Failure, Huazhong University of Science and Technology, Wuhan
430074, P.R. China
| | - Yanzong Lv
- School of Chemistry and Chemical Engineering, Hubei
Key Laboratory of Material Chemistry and Service Failure, Huazhong University of Science and Technology, Wuhan
430074, P.R. China
| | - Zhuqi Chen
- School of Chemistry and Chemical Engineering, Hubei
Key Laboratory of Material Chemistry and Service Failure, Huazhong University of Science and Technology, Wuhan
430074, P.R. China
| | - Fuming Mei
- School of Chemistry and Chemical Engineering, Hubei
Key Laboratory of Material Chemistry and Service Failure, Huazhong University of Science and Technology, Wuhan
430074, P.R. China
| | - Hui Xiong
- School of Chemistry and Chemical Engineering, Hubei
Key Laboratory of Material Chemistry and Service Failure, Huazhong University of Science and Technology, Wuhan
430074, P.R. China
| | - Guochuan Yin
- School of Chemistry and Chemical Engineering, Hubei
Key Laboratory of Material Chemistry and Service Failure, Huazhong University of Science and Technology, Wuhan
430074, P.R. China
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39
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Keough JM, Zuniga AN, Jenson DL, Barry BA. Redox control and hydrogen bonding networks: proton-coupled electron transfer reactions and tyrosine Z in the photosynthetic oxygen-evolving complex. J Phys Chem B 2013; 117:1296-307. [PMID: 23346921 DOI: 10.1021/jp3118314] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
In photosynthetic oxygen evolution, redox active tyrosine Z (YZ) plays an essential role in proton-coupled electron transfer (PCET) reactions. Four sequential photooxidation reactions are necessary to produce oxygen at a Mn(4)CaO(5) cluster. The sequentially oxidized states of this oxygen-evolving cluster (OEC) are called the S(n) states, where n refers to the number of oxidizing equivalents stored. The neutral radical, YZ•, is generated and then acts as an electron transfer intermediate during each S state transition. In the X-ray structure, YZ, Tyr161 of the D1 subunit, is involved in an extensive hydrogen bonding network, which includes calcium-bound water. In electron paramagnetic resonance experiments, we measured the YZ• recombination rate, in the presence of an intact Mn(4)CaO(5) cluster. We compared the S(0) and S(2) states, which differ in Mn oxidation state, and found a significant difference in the YZ• decay rate (t(1/2) = 3.3 ± 0.3 s in S(0); t(1/2) = 2.1 ± 0.3 s in S(2)) and in the solvent isotope effect (SIE) on the reaction (1.3 ± 0.3 in S(0); 2.1 ± 0.3 in S(2)). Although the YZ site is known to be solvent accessible, the recombination rate and SIE were pH independent in both S states. To define the origin of these effects, we measured the YZ• recombination rate in the presence of ammonia, which inhibits oxygen evolution and disrupts the hydrogen bond network. We report that ammonia dramatically slowed the YZ• recombination rate in the S(2) state but had a smaller effect in the S(0) state. In contrast, ammonia had no significant effect on YD•, the stable tyrosyl radical. Therefore, the alterations in YZ• decay, observed with S state advancement, are attributed to alterations in OEC hydrogen bonding and consequent differences in the YZ midpoint potential/pK(a). These changes may be caused by activation of metal-bound water molecules, which hydrogen bond to YZ. These observations document the importance of redox control in proton-coupled electron transfer reactions.
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Affiliation(s)
- James M Keough
- School of Chemistry and Biochemistry and the Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, Georgia 30332, USA
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40
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Weinberg DR, Gagliardi CJ, Hull JF, Murphy CF, Kent CA, Westlake BC, Paul A, Ess DH, McCafferty DG, Meyer TJ. Proton-Coupled Electron Transfer. Chem Rev 2012; 112:4016-93. [DOI: 10.1021/cr200177j] [Citation(s) in RCA: 1125] [Impact Index Per Article: 93.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- David R. Weinberg
- Department
of Chemistry, University
of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290,
United States
- Department of Physical and Environmental
Sciences, Colorado Mesa University, 1100 North Avenue, Grand Junction,
Colorado 81501-3122, United States
| | - Christopher J. Gagliardi
- Department
of Chemistry, University
of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290,
United States
| | - Jonathan F. Hull
- Department
of Chemistry, University
of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290,
United States
| | - Christine Fecenko Murphy
- Department
of Chemistry, B219
Levine Science Research Center, Box 90354, Duke University, Durham,
North Carolina 27708-0354, United States
| | - Caleb A. Kent
- Department
of Chemistry, University
of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290,
United States
| | - Brittany C. Westlake
- The American Chemical Society,
1155 Sixteenth Street NW, Washington, District of Columbia 20036,
United States
| | - Amit Paul
- Department
of Chemistry, University
of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290,
United States
| | - Daniel H. Ess
- Department
of Chemistry, University
of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290,
United States
| | - Dewey Granville McCafferty
- Department
of Chemistry, B219
Levine Science Research Center, Box 90354, Duke University, Durham,
North Carolina 27708-0354, United States
| | - Thomas J. Meyer
- Department
of Chemistry, University
of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290,
United States
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41
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Proton–coupled electron transfer versus hydrogen atom transfer: A density functional reactivity theory characterization. COMPUT THEOR CHEM 2012. [DOI: 10.1016/j.comptc.2012.02.020] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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42
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Reductive activation of the heme iron–nitrosyl intermediate in the reaction mechanism of cytochrome c nitrite reductase: a theoretical study. J Biol Inorg Chem 2012; 17:741-60. [DOI: 10.1007/s00775-012-0893-0] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2011] [Accepted: 03/05/2012] [Indexed: 01/08/2023]
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43
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Barry BA, Chen J, Keough J, Jenson D, Offenbacher A, Pagba C. Proton Coupled Electron Transfer and Redox Active Tyrosines: Structure and Function of the Tyrosyl Radicals in Ribonucleotide Reductase and Photosystem II. J Phys Chem Lett 2012; 3:543-554. [PMID: 22662289 PMCID: PMC3362996 DOI: 10.1021/jz2014117] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Proton coupled electron transfer (PCET) reactions are important in many biological processes. Tyrosine oxidation/reduction can play a critical role in facilitating these reactions. Two examples are photosystem II (PSII) and ribonucleotide reductase (RNR). RNR is essential in DNA synthesis in all organisms. In E. coli RNR, a tyrosyl radical, Y122(•), is required as a radical initiator. Photosystem II (PSII) generates molecular oxygen from water. In PSII, an essential tyrosyl radical, YZ(•), oxidizes the oxygen evolving center. However, the mechanisms, by which the extraordinary oxidizing power of the tyrosyl radical is controlled, are not well understood. This is due to the difficulty in acquiring high-resolution structural information about the radical state. Spectroscopic approaches, such as EPR and UV resonance Raman (UVRR), can give new information. Here, we discuss EPR studies of PCET and the PSII YZ radical. We also present UVRR results, which support the conclusion that Y122 undergoes an alteration in ring and backbone dihedral angle when it is oxidized. This conformational change results in a loss of hydrogen bonding to the phenolic oxygen. Our analysis suggests that access of water is an important factor in determining tyrosyl radical lifetime and function. TOC graphic.
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Okamura M, Yoshida M, Kuga R, Sakai K, Kondo M, Masaoka S. A mononuclear ruthenium complex showing multiple proton-coupled electron transfer toward multi-electron transfer reactions. Dalton Trans 2012; 41:13081-9. [DOI: 10.1039/c2dt30773a] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
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45
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Pizano AA, Yang JL, Nocera DG. Photochemical Tyrosine Oxidation with a Hydrogen-Bonded Proton Acceptor by Bidirectional Proton-Coupled Electron Transfer. Chem Sci 2012; 3:2457-2461. [PMID: 23495362 DOI: 10.1039/c2sc20113e] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Amino acid radical generation and transport are fundamentally important to numerous essential biological processes to which small molecule models lend valuable mechanistic insights. Pyridyl-amino acid-methyl esters are appended to a rhenium(I) tricarbonyl 1,10-phenanthroline core to yield rhenium-amino acid complexes with tyrosine ([Re]-Y-OH) and phenylalanine ([Re]-F). The emission from the [Re] center is more significantly quenched for [Re]-Y-OH upon addition of base. Time-resolved studies establish that excited-state quenching occurs by a combination of static and dynamic mechanisms. The degree of quenching depends on the strength of the base, consistent with a proton-coupled electron transfer (PCET) quenching mechanism. Comparative studies of [Re]-Y-OH and [Re]-F enable a detailed mechanistic analysis of a bidirectional PCET process.
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Affiliation(s)
- Arturo A Pizano
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA, 02139-4307; Tel: 61d53 5537
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46
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Bonin J, Robert M. Photoinduced Proton-Coupled Electron Transfers in Biorelevant Phenolic Systems. Photochem Photobiol 2011; 87:1190-203. [DOI: 10.1111/j.1751-1097.2011.00996.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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47
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Keough JM, Jenson DL, Zuniga AN, Barry BA. Proton coupled electron transfer and redox-active tyrosine Z in the photosynthetic oxygen-evolving complex. J Am Chem Soc 2011; 133:11084-7. [PMID: 21714528 PMCID: PMC3246746 DOI: 10.1021/ja2041139] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Proton coupled electron transfer (PCET) reactions play an essential role in many enzymatic processes. In PCET, redox-active tyrosines may be involved as intermediates when the oxidized phenolic side chain deprotonates. Photosystem II (PSII) is an excellent framework for studying PCET reactions, because it contains two redox-active tyrosines, YD and YZ, with different roles in catalysis. One of the redox-active tyrosines, YZ, is essential for oxygen evolution and is rapidly reduced by the manganese-catalytic site. In this report, we investigate the mechanism of YZ PCET in oxygen-evolving PSII. To isolate YZ(•) reactions, but retain the manganese-calcium cluster, low temperatures were used to block the oxidation of the metal cluster, high microwave powers were used to saturate the YD(•) EPR signal, and YZ(•) decay kinetics were measured with EPR spectroscopy. Analysis of the pH and solvent isotope dependence was performed. The rate of YZ(•) decay exhibited a significant solvent isotope effect, and the rate of recombination and the solvent isotope effect were pH independent from pH 5.0 to 7.5. These results are consistent with a rate-limiting, coupled proton electron transfer (CPET) reaction and are contrasted to results obtained for YD(•) decay kinetics at low pH. This effect may be mediated by an extensive hydrogen-bond network around YZ. These experiments imply that PCET reactions distinguish the two PSII redox-active tyrosines.
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Affiliation(s)
- James M. Keough
- School of Chemistry and Biochemistry and the Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, Georgia 30332
| | - David L. Jenson
- School of Chemistry and Biochemistry and the Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, Georgia 30332
| | - Ashley N. Zuniga
- School of Chemistry and Biochemistry and the Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, Georgia 30332
| | - Bridgette A. Barry
- School of Chemistry and Biochemistry and the Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, Georgia 30332
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Leferink NGH, Pudney CR, Brenner S, Heyes DJ, Eady RR, Samar Hasnain S, Hay S, Rigby SEJ, Scrutton NS. Gating mechanisms for biological electron transfer: integrating structure with biophysics reveals the nature of redox control in cytochrome P450 reductase and copper-dependent nitrite reductase. FEBS Lett 2011; 586:578-84. [PMID: 21762695 DOI: 10.1016/j.febslet.2011.07.003] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2011] [Revised: 07/01/2011] [Accepted: 07/04/2011] [Indexed: 11/16/2022]
Abstract
Biological electron transfer is a fundamentally important reaction. Despite the apparent simplicity of these reactions (in that no bonds are made or broken), their experimental interrogation is often complicated because of adiabatic control exerted through associated chemical and conformational change. We have studied the nature of this control in several enzyme systems, cytochrome P450 reductase, methionine synthase reductase and copper-dependent nitrite reductase. Specifically, we review the evidence for conformational control in cytochrome P450 reductase and methionine synthase reductase and chemical control i.e. proton coupled electron transfer in nitrite reductase. This evidence has accrued through the use and integration of structural, spectroscopic and advanced kinetic methods. This integrated approach is shown to be powerful in dissecting control mechanisms for biological electron transfer and will likely find widespread application in the study of related biological redox systems.
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Affiliation(s)
- Nicole G H Leferink
- Manchester Interdisciplinary Biocentre, Faculty of Life Sciences, University of Manchester, 131 Princess Street, Manchester M1 7DN, United Kingdom
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Barry BA. Proton coupled electron transfer and redox active tyrosines in Photosystem II. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY. B, BIOLOGY 2011; 104:60-71. [PMID: 21419640 PMCID: PMC3164834 DOI: 10.1016/j.jphotobiol.2011.01.026] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/09/2010] [Revised: 01/25/2011] [Accepted: 01/31/2011] [Indexed: 11/30/2022]
Abstract
In this article, progress in understanding proton coupled electron transfer (PCET) in Photosystem II is reviewed. Changes in acidity/basicity may accompany oxidation/reduction reactions in biological catalysis. Alterations in the proton transfer pathway can then be used to alter the rates of the electron transfer reactions. Studies of the bioenergetic complexes have played a central role in advancing our understanding of PCET. Because oxidation of the tyrosine results in deprotonation of the phenolic oxygen, redox active tyrosines are involved in PCET reactions in several enzymes. This review focuses on PCET involving the redox active tyrosines in Photosystem II. Photosystem II catalyzes the light-driven oxidation of water and reduction of plastoquinone. Photosystem II provides a paradigm for the study of redox active tyrosines, because this photosynthetic reaction center contains two tyrosines with different roles in catalysis. The tyrosines, YZ and YD, exhibit differences in kinetics and midpoint potentials, and these differences may be due to noncovalent interactions with the protein environment. Here, studies of YD and YZ and relevant model compounds are described.
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Affiliation(s)
- Bridgette A Barry
- School of Chemistry and Biochemistry and The Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, GA 30332, USA.
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Liu S, Ess DH, Schauer CK. Density Functional Reactivity Theory Characterizes Charge Separation Propensity in Proton-Coupled Electron Transfer Reactions. J Phys Chem A 2011; 115:4738-42. [DOI: 10.1021/jp112319d] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Shubin Liu
- Research Computing Center, University of North Carolina, Chapel Hill, North Carolina 27599-3420, United States
| | - Daniel H. Ess
- Department of Chemistry and Biochemistry, Brigham Young University, Provo, Utah 84602, United States
- Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599-3290, United States
| | - Cynthia K. Schauer
- Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599-3290, United States
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