51
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Bin Mohd Yusof MS, Lim YL, Loh ZH. Ultrafast vibrational wave packet dynamics of the aqueous tyrosyl radical anion induced by photodetachment. Phys Chem Chem Phys 2021; 23:18525-18534. [PMID: 34581329 DOI: 10.1039/d1cp02975d] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The ultrafast dynamics triggered by the photodetachment of the tyrosinate dianion in aqueous environment shed light on the elementary processes that accompany the interaction of ionizing radiation with biological matter. Photodetachment of the tryosinate dianion yields the tyrosyl radical anion, an important intermediate in biological redox reactions, although the study of its ultrafast dynamics is limited. Here, we utilize femtosecond optical pump-probe spectroscopy to investigate the ultrafast structural reorganization dynamics that follow the photodetachment of the tyrosinate dianion in aqueous solution. Photodetachment of the tyrosinate dianion leads to vibrational wave packet motion along seven vibrational modes that are coupled to the photodetachment process. The vibrational modes are assigned with the aid of density functional theory (DFT) calculations. Our results offer a glimpse of the elementary dynamics of ionized biomolecules and suggest the possibility of extending this approach to investigate the ionization-induced structural rearrangement of other aromatic amino acids and larger biomolecules.
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Affiliation(s)
- Muhammad Shafiq Bin Mohd Yusof
- Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371, Singapore.
| | - Yong Liang Lim
- Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371, Singapore.
| | - Zhi-Heng Loh
- Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371, Singapore.
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52
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Morozova OB, Stass DV, Yurkovskaya AV. Kinetic evidence for the transiently shifted acidity constant of histidine linked to paramagnetic tyrosine probed by intramolecular electron transfer in oxidized peptides. Phys Chem Chem Phys 2021; 23:16698-16706. [PMID: 34338250 DOI: 10.1039/d1cp02408f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The kinetics of electron transfer (ET) from tyrosine (Tyr) to short-lived histidine (His) radicals in peptides of different structures was monitored using time-resolved chemically induced dynamic nuclear polarization (CIDNP) to follow the reduction of the His radicals using NMR detection of the diamagnetic hyperpolarized reaction products. In aqueous solution over a wide pH range, His radicals were generated in situ in the photo-induced reaction with the photosensitizer, 3,3',4,4'-tetracarboxy benzophenone. Model simulations of the CIDNP kinetics provided pH-dependent rate constants of intra- and intermolecular ET, and the pH dependencies of the reaction under study were interpreted in terms of protonation states of the reactants and the product, His with either protonated or neutral imidazole. In some cases, an increase of pKa of imidazole in the presence of the short-lived radical center at a nearby Tyr residue was revealed. Interpretation of the obtained pH dependencies made is possible to quantify the degree of paramagnetic shift of the acidity constant of the imidazole of the His residue in the peptides with a Tyr residue in its paramagnetic state, and to correlate this degree with the intramolecular ET rate constant - a higher intramolecular ET rate constant corresponded to a greater acidity constant shift.
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Affiliation(s)
- Olga B Morozova
- International Tomography Center, Institutskaya 3a, 630090 Novosibirsk, Russia.
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53
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Li X, Sun W, Qin X, Xie Y, Liu N, Luo X, Wang Y, Chen X. An interesting possibility of forming special hole stepping stones with high-stacking aromatic rings in proteins: three-π five-electron and four-π seven-electron resonance bindings. RSC Adv 2021; 11:26672-26682. [PMID: 35479969 PMCID: PMC9037495 DOI: 10.1039/d1ra05341h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2021] [Accepted: 07/30/2021] [Indexed: 11/30/2022] Open
Abstract
Long-range hole transfer of proteins plays an important role in many biological processes of living organisms. Therefore, it is highly useful to examine the possible hole stepping stones, which can facilitate hole transfer in proteins. However, the structures of stepping stones are diverse because of the complexity of the protein structures. In the present work, we proposed a series of special stepping stones, which are instantaneously formed by three and four packing aromatic side chains of amino acids to capture a hole, corresponding to three-π five-electron (π:π∴π↔π∴π:π) and four-π seven-electron (π:π∴π:π↔π:π:π∴π) resonance bindings with appropriate binding energies. The aromatic amino acids include histidine (His), phenylalanine (Phe), tyrosine (Tyr) and tryptophan (Trp). The formations of these special stepping stones can effectively reduce the local ionization potential of the high π-stacking region to efficiently capture the migration hole. The quick formations and separations of them promote the efficient hole transfer in proteins. More interestingly, we revealed that a hole cannot delocalize over infinite aromatic rings along the high π-π packing structure at the same time and the micro-surroundings of proteins can modulate the formations of π:π∴π↔π∴π:π and π:π∴π:π↔π:π:π∴π bindings. These results may contribute a new avenue to better understand the potential hole transfer pathway in proteins.
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Affiliation(s)
- Xin Li
- Chongqing Key Laboratory of Theoretical and Computational Chemistry, School of Chemistry and Chemical Engineering, Chongqing University Chongqing 401331 P.R. China
- National-Municipal Joint Engineering Laboratory for Chemical Process Intensification and Reaction, Chongqing University Chongqing 401331 P.R. China
| | - Weichao Sun
- Chongqing Key Laboratory of Theoretical and Computational Chemistry, School of Chemistry and Chemical Engineering, Chongqing University Chongqing 401331 P.R. China
- National-Municipal Joint Engineering Laboratory for Chemical Process Intensification and Reaction, Chongqing University Chongqing 401331 P.R. China
| | - Xin Qin
- Chongqing Key Laboratory of Theoretical and Computational Chemistry, School of Chemistry and Chemical Engineering, Chongqing University Chongqing 401331 P.R. China
- National-Municipal Joint Engineering Laboratory for Chemical Process Intensification and Reaction, Chongqing University Chongqing 401331 P.R. China
| | - Yuxin Xie
- Chongqing Key Laboratory of Theoretical and Computational Chemistry, School of Chemistry and Chemical Engineering, Chongqing University Chongqing 401331 P.R. China
- National-Municipal Joint Engineering Laboratory for Chemical Process Intensification and Reaction, Chongqing University Chongqing 401331 P.R. China
| | - Nian Liu
- Chongqing Key Laboratory of Theoretical and Computational Chemistry, School of Chemistry and Chemical Engineering, Chongqing University Chongqing 401331 P.R. China
- National-Municipal Joint Engineering Laboratory for Chemical Process Intensification and Reaction, Chongqing University Chongqing 401331 P.R. China
| | - Xin Luo
- Chongqing Key Laboratory of Theoretical and Computational Chemistry, School of Chemistry and Chemical Engineering, Chongqing University Chongqing 401331 P.R. China
- National-Municipal Joint Engineering Laboratory for Chemical Process Intensification and Reaction, Chongqing University Chongqing 401331 P.R. China
| | - Yuanying Wang
- Chongqing Key Laboratory of Theoretical and Computational Chemistry, School of Chemistry and Chemical Engineering, Chongqing University Chongqing 401331 P.R. China
- National-Municipal Joint Engineering Laboratory for Chemical Process Intensification and Reaction, Chongqing University Chongqing 401331 P.R. China
| | - Xiaohua Chen
- Chongqing Key Laboratory of Theoretical and Computational Chemistry, School of Chemistry and Chemical Engineering, Chongqing University Chongqing 401331 P.R. China
- National-Municipal Joint Engineering Laboratory for Chemical Process Intensification and Reaction, Chongqing University Chongqing 401331 P.R. China
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54
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Schell E, Nouairia G, Steiner E, Weber N, Lundin D, Loderer C. Structural determinants and distribution of phosphate specificity in ribonucleotide reductases. J Biol Chem 2021; 297:101008. [PMID: 34314684 PMCID: PMC8365446 DOI: 10.1016/j.jbc.2021.101008] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2021] [Revised: 07/21/2021] [Accepted: 07/23/2021] [Indexed: 11/24/2022] Open
Abstract
Ribonucleotide reductases (RNRs) catalyze the reduction of ribonucleotides to the corresponding deoxyribonucleotides, the building blocks of DNA. RNRs are specific for either ribonucleoside diphosphates or triphosphates as substrates. As far as is known, oxygen-dependent class I RNRs (NrdAB) all reduce ribonucleoside diphosphates, and oxygen-sensitive class III RNRs (NrdD) are all ribonucleoside triphosphate reducers, whereas the adenosylcobalamin-dependent class II (NrdJ) contains both ribonucleoside diphosphate and triphosphate reducers. However, it is unknown how this specificity is conveyed by the active site of the enzymes and how this feature developed in RNR evolution. By structural comparison of the active sites in different RNRs, we identified the apical loop of the phosphate-binding site as a potential structural determinant of substrate specificity. Grafting two residues from this loop from a diphosphate- to a triphosphate-specific RNR caused a change in preference from ribonucleoside triphosphate to diphosphate substrates in a class II model enzyme, confirming them as the structural determinants of phosphate specificity. The investigation of the phylogenetic distribution of this motif in class II RNRs yielded a likely monophyletic clade with the diphosphate-defining motif. This indicates a single evolutionary-split event early in NrdJ evolution in which diphosphate specificity developed from the earlier triphosphate specificity. For those interesting cases where organisms contain more than one nrdJ gene, we observed a preference for encoding enzymes with diverse phosphate specificities, suggesting that this varying phosphate specificity confers a selective advantage.
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Affiliation(s)
- Eugen Schell
- Institute for Microbiology, Technische Universität Dresden, Dresden, Saxony, Germany
| | - Ghada Nouairia
- Department of Biochemistry and Biophysics, Stockholm University, Stockholm, Sweden
| | - Elisabeth Steiner
- Institute for Microbiology, Technische Universität Dresden, Dresden, Saxony, Germany
| | - Niclas Weber
- Institute for Microbiology, Technische Universität Dresden, Dresden, Saxony, Germany
| | - Daniel Lundin
- Department of Biochemistry and Biophysics, Stockholm University, Stockholm, Sweden
| | - Christoph Loderer
- Institute for Microbiology, Technische Universität Dresden, Dresden, Saxony, Germany.
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55
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Watson RA, Offenbacher AR, Barry BA. Detection of Catalytically Linked Conformational Changes in Wild-Type Class Ia Ribonucleotide Reductase Using Reaction-Induced FTIR Spectroscopy. J Phys Chem B 2021; 125:8362-8372. [PMID: 34289692 DOI: 10.1021/acs.jpcb.1c03038] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The enzyme, ribonucleotide reductase (RNR), is essential for DNA synthesis in all cells. The class Ia Escherichia coli RNR consists of two dimeric subunits, α2 and β2, which form an active but unstable heterodimer of dimers, α2β2. The structure of the wild-type form of the enzyme has been challenging to study due to the instability of the catalytic complex. A long-range proton-coupled electron-transfer (PCET) pathway facilitates radical migration from the Y122 radical-diiron cofactor in the β subunit to an active site cysteine, C439, in the α subunit to initiate the RNR chemistry. The PCET reactions and active site chemistry are spectroscopically masked by a rate-limiting, conformational gate. Here, we present a reaction-induced Fourier transform infrared (RIFTIR) spectroscopic method to monitor the mechanism of the active, wild-type RNR α2β2 complex. This method is employed to obtain new information about conformational changes accompanying RNR catalysis, including the role of carboxylate interactions, deprotonation, and oxidation of active site cysteines, and a detailed description of reversible secondary structural changes. Labeling of tyrosine revealed a conformationally active tyrosine in the β subunit, assigned to Y356β, which is part of the intersubunit PCET pathway. New insights into the roles of the inhibitors, azidoUDP and dATP, and the sensitivity of RIFTIR spectroscopy to detect subtle conformational motions arising from protein allostery are also presented.
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Affiliation(s)
- Ryan Atlee Watson
- Department of Chemistry and Biochemistry and the Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, Georgia, United States
| | - Adam R Offenbacher
- Department of Chemistry and Biochemistry and the Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, Georgia, United States.,Department of Chemistry, East Carolina University, Greenville, North Carolina, United States
| | - Bridgette A Barry
- Department of Chemistry and Biochemistry and the Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, Georgia, United States
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56
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Abstract
Electron-nuclear double resonance (ENDOR) measures the hyperfine interaction of magnetic nuclei with paramagnetic centers and is hence a powerful tool for spectroscopic investigations extending from biophysics to material science. Progress in microwave technology and the recent availability of commercial electron paramagnetic resonance (EPR) spectrometers up to an electron Larmor frequency of 263 GHz now open the opportunity for a more quantitative spectral analysis. Using representative spectra of a prototype amino acid radical in a biologically relevant enzyme, the [Formula: see text] in Escherichia coli ribonucleotide reductase, we developed a statistical model for ENDOR data and conducted statistical inference on the spectra including uncertainty estimation and hypothesis testing. Our approach in conjunction with 1H/2H isotopic labeling of [Formula: see text] in the protein unambiguously established new unexpected spectral contributions. Density functional theory (DFT) calculations and ENDOR spectral simulations indicated that these features result from the beta-methylene hyperfine coupling and are caused by a distribution of molecular conformations, likely important for the biological function of this essential radical. The results demonstrate that model-based statistical analysis in combination with state-of-the-art spectroscopy accesses information hitherto beyond standard approaches.
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57
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Zhang S, Ruccolo S, Fryszkowska A, Klapars A, Marshall N, Strotman NA. Electrochemical Activation of Galactose Oxidase: Mechanistic Studies and Synthetic Applications. ACS Catal 2021. [DOI: 10.1021/acscatal.1c01037] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Affiliation(s)
- Shaoguang Zhang
- Process Research and Development, Merck & Co., Inc., Rahway, New Jersey 07065, United States
| | - Serge Ruccolo
- Process Research and Development, Merck & Co., Inc., Rahway, New Jersey 07065, United States
| | - Anna Fryszkowska
- Process Research and Development, Merck & Co., Inc., Rahway, New Jersey 07065, United States
| | - Artis Klapars
- Process Research and Development, Merck & Co., Inc., Rahway, New Jersey 07065, United States
| | - Nicholas Marshall
- Process Research and Development, Merck & Co., Inc., Rahway, New Jersey 07065, United States
| | - Neil A. Strotman
- Process Research and Development, Merck & Co., Inc., Rahway, New Jersey 07065, United States
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58
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Jiang V, Khare SD, Banta S. Computational structure prediction provides a plausible mechanism for electron transfer by the outer membrane protein Cyc2 from Acidithiobacillus ferrooxidans. Protein Sci 2021; 30:1640-1652. [PMID: 33969560 DOI: 10.1002/pro.4106] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2021] [Revised: 04/30/2021] [Accepted: 05/03/2021] [Indexed: 12/14/2022]
Abstract
Cyc2 is the key protein in the outer membrane of Acidithiobacillus ferrooxidans that mediates electron transfer between extracellular inorganic iron and the intracellular central metabolism. This cytochrome c is specific for iron and interacts with periplasmic proteins to complete a reversible electron transport chain. A structure of Cyc2 has not yet been characterized experimentally. Here we describe a structural model of Cyc2, and associated proteins, to highlight a plausible mechanism for the ferrous iron electron transfer chain. A comparative modeling protocol specific for trans membrane beta barrel (TMBB) proteins in acidophilic conditions (pH ~ 2) was applied to the primary sequence of Cyc2. The proposed structure has three main regimes: Extracellular loops exposed to low-pH conditions, a TMBB, and an N-terminal cytochrome-like region within the periplasmic space. The Cyc2 model was further refined by identifying likely iron and heme docking sites. This represents the first computational model of Cyc2 that accounts for the membrane microenvironment and the acidity in the extracellular matrix. This approach can be used to model other TMBBs which can be critical for chemolithotrophic microbial growth.
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Affiliation(s)
- Virginia Jiang
- Department of Chemical Engineering, Columbia University in the City of New York, New York, New York, USA
| | - Sagar D Khare
- Department of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, Piscataway, New Jersey, USA
| | - Scott Banta
- Department of Chemical Engineering, Columbia University in the City of New York, New York, New York, USA
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59
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Reinhardt CR, Sayfutyarova ER, Zhong J, Hammes-Schiffer S. Glutamate Mediates Proton-Coupled Electron Transfer Between Tyrosines 730 and 731 in Escherichia coli Ribonucleotide Reductase. J Am Chem Soc 2021; 143:6054-6059. [DOI: 10.1021/jacs.1c02152] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Clorice R. Reinhardt
- Department of Molecular Biophysics & Biochemistry, Yale University, 266 Whitney Avenue, New Haven, Connecticut 06520, United States
| | - Elvira R. Sayfutyarova
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06520, United States
| | - Jiayun Zhong
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06520, United States
| | - Sharon Hammes-Schiffer
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06520, United States
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60
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Lin ZP, Al Zouabi NN, Xu ML, Bowen NE, Wu TL, Lavi ES, Huang PH, Zhu YL, Kim B, Ratner ES. In silico screening identifies a novel small molecule inhibitor that counteracts PARP inhibitor resistance in ovarian cancer. Sci Rep 2021; 11:8042. [PMID: 33850183 PMCID: PMC8044145 DOI: 10.1038/s41598-021-87325-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2020] [Accepted: 03/22/2021] [Indexed: 12/20/2022] Open
Abstract
Poly ADP-ribose polymerase (PARP) inhibitors are promising targeted therapy for epithelial ovarian cancer (EOC) with BRCA mutations or defective homologous recombination (HR) repair. However, reversion of BRCA mutation and restoration of HR repair in EOC lead to PARP inhibitor resistance and reduced clinical efficacy of PARP inhibitors. We have previously shown that triapine, a small molecule inhibitor of ribonucleotide reductase (RNR), impaired HR repair and sensitized HR repair-proficient EOC to PARP inhibitors. In this study, we performed in silico screening of small molecule libraries to identify novel compounds that bind to the triapine-binding pocket on the R2 subunit of RNR and inhibit RNR in EOC cells. Following experimental validation of selected top-ranking in silico hits for inhibition of dNTP and DNA synthesis, we identified, DB4, a putative RNR pocket-binding inhibitor markedly abrogated HR repair and sensitized BRCA-wild-type EOC cells to the PARP inhibitor olaparib. Furthermore, we demonstrated that the combination of DB4 and olaparib deterred the progression of BRCA-wild type EOC xenografts and significantly prolonged the survival time of tumor-bearing mice. Herein we report the discovery of a putative small molecule inhibitor of RNR and HR repair for combination with PARP inhibitors to treat PARP inhibitor-resistant and HR repair-proficient EOC.
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Affiliation(s)
- Z Ping Lin
- Department of Obstetrics, Gynecology, and Reproductive Sciences, Yale University School of Medicine, New Haven, CT, 06510, USA.
| | - Nour N Al Zouabi
- Department of Obstetrics, Gynecology, and Reproductive Sciences, Yale University School of Medicine, New Haven, CT, 06510, USA
| | - Mark L Xu
- Department of Obstetrics, Gynecology, and Reproductive Sciences, Yale University School of Medicine, New Haven, CT, 06510, USA
| | - Nicole E Bowen
- Department of Pediatrics, Emory University School of Medicine, Atlanta, GA, 30322, USA
| | - Terence L Wu
- Yale West Campus Analytical Core, Yale University, West Haven, CT, 06516, USA
| | - Ethan S Lavi
- Department of Obstetrics, Gynecology, and Reproductive Sciences, Yale University School of Medicine, New Haven, CT, 06510, USA
| | - Pamela H Huang
- Department of Pediatrics, Yale University School of Medicine, New Haven, CT, 06510, USA
| | - Yong-Lian Zhu
- Department of Obstetrics, Gynecology, and Reproductive Sciences, Yale University School of Medicine, New Haven, CT, 06510, USA
| | - Baek Kim
- Department of Pediatrics, Emory University School of Medicine, Atlanta, GA, 30322, USA
- Center for Drug Discovery, Children's Healthcare of Atlanta, Atlanta, GA, 30322, USA
| | - Elena S Ratner
- Department of Obstetrics, Gynecology, and Reproductive Sciences, Yale University School of Medicine, New Haven, CT, 06510, USA.
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61
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Tyburski R, Liu T, Glover SD, Hammarström L. Proton-Coupled Electron Transfer Guidelines, Fair and Square. J Am Chem Soc 2021; 143:560-576. [PMID: 33405896 PMCID: PMC7880575 DOI: 10.1021/jacs.0c09106] [Citation(s) in RCA: 196] [Impact Index Per Article: 65.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2020] [Indexed: 12/23/2022]
Abstract
Proton-coupled electron transfer (PCET) reactions are fundamental to energy transformation reactions in natural and artificial systems and are increasingly recognized in areas such as catalysis and synthetic chemistry. The interdependence of proton and electron transfer brings a mechanistic richness of reactivity, including various sequential and concerted mechanisms. Delineating between different PCET mechanisms and understanding why a particular mechanism dominates are crucial for the design and optimization of reactions that use PCET. This Perspective provides practical guidelines for how to discern between sequential and concerted mechanisms based on interpretations of thermodynamic data with temperature-, pressure-, and isotope-dependent kinetics. We present new PCET-zone diagrams that show how a mechanism can switch or even be eliminated by varying the thermodynamic (ΔGPT° and ΔGET°) and coupling strengths for a PCET system. We discuss the appropriateness of asynchronous concerted PCET to rationalize observations in organic reactions, and the distinction between hydrogen atom transfer and other concerted PCET reactions. Contemporary issues and future prospects in PCET research are discussed.
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Affiliation(s)
- Robin Tyburski
- Ångström
Laboratory, Department of Chemistry, Uppsala
University, Box 523, SE75120 Uppsala, Sweden
| | - Tianfei Liu
- Department
of Chemistry, University of North Carolina
at Chapel Hill, Chapel
Hill, North Carolina 27599-3290, United States
| | - Starla D. Glover
- Ångström
Laboratory, Department of Chemistry, Uppsala
University, Box 523, SE75120 Uppsala, Sweden
| | - Leif Hammarström
- Ångström
Laboratory, Department of Chemistry, Uppsala
University, Box 523, SE75120 Uppsala, Sweden
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62
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Tang WK, Mu X, Li M, Martens J, Berden G, Oomens J, Chu IK, Siu CK. Formation of n → π + interaction facilitating dissociative electron transfer in isolated tyrosine-containing molecular peptide radical cations. Phys Chem Chem Phys 2021; 22:21393-21402. [PMID: 32940309 DOI: 10.1039/d0cp00533a] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Long-range electron transfer in proteins can be rationalized as a sequential short-distance electron-hopping processes via amino acid residues having low ionization energy as relay stations. Tyrosine residues can serve as such redox-active intermediates through one-electron oxidation to form a π-radical cation at its phenol side chain. An electron transfer from a vicinal functional group to this π-electron hole completes an elementary step of charge migration. However, transient oxidized/reduced intermediates formed at those relay stations during electron transfer processes have not been observed. In this study, formation of analog reactive intermediates via electron donor-acceptor coupling is observed by using IRMPD action spectroscopy. An elementary charge migration at the molecular level in model tyrosine-containing peptide radical cations [M]˙+ in the gas phase is revealed with its unusual Cα-Cβ bond cleavage at the side chain of the N-terminal residue. This reaction is induced by the radical character of the N-terminal amino group (-NH2˙+) resulting from an n → π+ interaction between the nonbonding electron pair of NH2 (n) and the π-electron hole at the Tyr side chain (π+). The formation of -NH2˙+ is supported by the IRMPD spectrum showing a characteristic NH2 scissor vibration coupled with Tyr side-chain stretches at 1577 cm-1. This n → π+ interaction facilitates a dissociative electron transfer with NH2 as the relay station. The occurrence of this side-chain cleavage may be an indicator of the formation of reactive conformers featuring the n → π+ interaction.
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Affiliation(s)
- Wai Kit Tang
- Department of Chemistry, City University of Hong Kong, Tat Chee Avenue, Kowloon Tong, Hong Kong SAR, China.
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63
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Berg N, Bergwinkl S, Nuernberger P, Horinek D, Gschwind RM. Extended Hydrogen Bond Networks for Effective Proton-Coupled Electron Transfer (PCET) Reactions: The Unexpected Role of Thiophenol and Its Acidic Channel in Photocatalytic Hydroamidations. J Am Chem Soc 2021; 143:724-735. [DOI: 10.1021/jacs.0c08673] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Affiliation(s)
- Nele Berg
- Institute of Organic Chemistry, University of Regensburg, D-93053 Regensburg, Germany
| | - Sebastian Bergwinkl
- Institute of Physical and Theoretical Chemistry, University of Regensburg, D-93053 Regensburg, Germany
| | - Patrick Nuernberger
- Institute of Physical and Theoretical Chemistry, University of Regensburg, D-93053 Regensburg, Germany
| | - Dominik Horinek
- Institute of Physical and Theoretical Chemistry, University of Regensburg, D-93053 Regensburg, Germany
| | - Ruth M. Gschwind
- Institute of Organic Chemistry, University of Regensburg, D-93053 Regensburg, Germany
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64
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Computing Proton-Coupled Redox Potentials of Fluorotyrosines in a Protein Environment. J Phys Chem B 2020; 125:128-136. [PMID: 33378205 DOI: 10.1021/acs.jpcb.0c09974] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The oxidation of tyrosine to form the neutral tyrosine radical via proton-coupled electron transfer is essential for a wide range of biological processes. The precise measurement of the proton-coupled redox potentials of tyrosine (Y) in complex protein environments is challenging mainly because of the highly oxidizing and reactive nature of the radical state. Herein, a computational strategy is presented for predicting proton-coupled redox potentials in a protein environment. In this strategy, both the reduced Y-OH and oxidized Y-O• forms of tyrosine are sampled with molecular dynamics using a molecular mechanical force field. For a large number of conformations, a quantum mechanical/molecular mechanical (QM/MM) electrostatic embedding scheme is used to compute the free-energy differences between the reduced and oxidized forms, including the zero-point energy and entropic contributions as well as the impact of the protein electrostatic environment. This strategy is applied to a series of fluorinated tyrosine derivatives embedded in a de novo α-helical protein denoted as α3Y. The force fields for both the reduced and oxidized forms of these noncanonical fluorinated tyrosine residues are parameterized for general use. The calculated relative proton-coupled redox potentials agree with experimentally measured values with a mean unsigned error of 24 mV. Analysis of the simulations illustrates that hydrogen-bonding interactions between tyrosine and water increase the redox potentials by ∼100-250 mV, with significant variations because of the fluctuating protein environment. This QM/MM approach enables the calculation of proton-coupled redox potentials of tyrosine and other residues such as tryptophan in a variety of protein systems.
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65
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Chen CC, Min J, Zhang L, Yang Y, Yu X, Guo RT. Advanced Understanding of the Electron Transfer Pathway of Cytochrome P450s. Chembiochem 2020; 22:1317-1328. [PMID: 33232569 DOI: 10.1002/cbic.202000705] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2020] [Revised: 11/24/2020] [Indexed: 11/08/2022]
Abstract
Cytochrome P450s are heme-thiolate enzymes that participate in carbon source assimilation, natural compound biosynthesis and xenobiotic metabolism in all kingdoms of life. P450s can catalyze various reactions by using a wide range of organic compounds, thus exhibiting great potential in biotechnological applications. The catalytic reactions of P450s are driven by electron equivalents that are sourced from pyridine nucleotides and delivered by cognate or matching redox partners (RPs). The electron transfer (ET) route from RPs to P450s involves one or more redox center-containing domains. As the rate of ET is one of the main determinants of P450 efficacy, an in-depth understanding of the P450 ET pathway should increase our knowledge of these important enzymes and benefit their further applications. Here, the various P450 RP systems along with current understanding of their ET routes will be reviewed. Notably, state-of-the-art structural studies of the two main types of self-sufficient P450 will also be summarized.
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Affiliation(s)
- Chun-Chi Chen
- State Key Laboratory of Biocatalysis and Enzyme Engineering Hubei Collaborative Innovation Center for Green Transformation of Bio-Resources Hubei Key Laboratory of Industrial Biotechnology School of Life Sciences, Hubei University, Wuhan, Hubei, 430062, P. R. China
| | - Jian Min
- State Key Laboratory of Biocatalysis and Enzyme Engineering Hubei Collaborative Innovation Center for Green Transformation of Bio-Resources Hubei Key Laboratory of Industrial Biotechnology School of Life Sciences, Hubei University, Wuhan, Hubei, 430062, P. R. China
| | - Lilan Zhang
- State Key Laboratory of Biocatalysis and Enzyme Engineering Hubei Collaborative Innovation Center for Green Transformation of Bio-Resources Hubei Key Laboratory of Industrial Biotechnology School of Life Sciences, Hubei University, Wuhan, Hubei, 430062, P. R. China
| | - Yu Yang
- State Key Laboratory of Biocatalysis and Enzyme Engineering Hubei Collaborative Innovation Center for Green Transformation of Bio-Resources Hubei Key Laboratory of Industrial Biotechnology School of Life Sciences, Hubei University, Wuhan, Hubei, 430062, P. R. China
| | - Xuejing Yu
- State Key Laboratory of Biocatalysis and Enzyme Engineering Hubei Collaborative Innovation Center for Green Transformation of Bio-Resources Hubei Key Laboratory of Industrial Biotechnology School of Life Sciences, Hubei University, Wuhan, Hubei, 430062, P. R. China
| | - Rey-Ting Guo
- State Key Laboratory of Biocatalysis and Enzyme Engineering Hubei Collaborative Innovation Center for Green Transformation of Bio-Resources Hubei Key Laboratory of Industrial Biotechnology School of Life Sciences, Hubei University, Wuhan, Hubei, 430062, P. R. China
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66
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Cui C, Greene BL, Kang G, Drennan CL, Stubbe J, Nocera DG. Gated Proton Release during Radical Transfer at the Subunit Interface of Ribonucleotide Reductase. J Am Chem Soc 2020; 143:176-183. [PMID: 33353307 DOI: 10.1021/jacs.0c07879] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The class Ia ribonucleotide reductase of Escherichia coli requires strict regulation of long-range radical transfer between two subunits, α and β, through a series of redox-active amino acids (Y122•[β] ↔ W48?[β] ↔ Y356[β] ↔ Y731[α] ↔ Y730[α] ↔ C439[α]). Nowhere is this more precarious than at the subunit interface. Here, we show that the oxidation of Y356 is regulated by proton release involving a specific residue, E52[β], which is part of a water channel at the subunit interface for rapid proton transfer to the bulk solvent. An E52Q variant is incapable of Y356 oxidation via the native radical transfer pathway or non-native photochemical oxidation, following photosensitization by covalent attachment of a photo-oxidant at position 355[β]. Substitution of Y356 for various FnY analogues in an E52Q-photoβ2, where the side chain remains deprotonated, recovered photochemical enzymatic turnover. Transient absorption and emission data support the conclusion that Y356 oxidation requires E52 for proton management, suggesting its essential role in gating radical transport across the protein-protein interface.
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Affiliation(s)
- Chang Cui
- Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, Massachusetts 02138, United States
| | - Brandon L Greene
- Department of Chemistry and Biochemistry, University of California Santa Barbara, Santa Barbara, California 93106, United States
| | - Gyunghoon Kang
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 20139, United States.,Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, Massachusetts 20139, United States
| | - Catherine L Drennan
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 20139, United States.,Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, Massachusetts 20139, United States.,Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 20139, United States.,Fellow, Bio-inspired Solar Energy Program, Canadian Institute for Advanced Research, Toronto, Ontario M5G 1M1, Canada
| | - JoAnne Stubbe
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 20139, United States.,Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 20139, United States
| | - Daniel G Nocera
- Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, Massachusetts 02138, United States
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67
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Gualandi A, Nenov A, Marchini M, Rodeghiero G, Conti I, Paltanin E, Balletti M, Ceroni P, Garavelli M, Cozzi PG. Tailored Coumarin Dyes for Photoredox Catalysis: Calculation, Synthesis, and Electronic Properties. ChemCatChem 2020. [DOI: 10.1002/cctc.202001690] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Affiliation(s)
- Andrea Gualandi
- Dipartimento di Chimica “G. Ciamician” Alma Mater Studiorum – Università di Bologna Via Selmi 2 40126 Bologna Italy
| | - Artur Nenov
- Dipartimento di Chimica Industriale “T. Montanari” Alma Mater Studiorum – Università di Bologna Viale Risorgimento 4 40136 Bologna Italy
| | - Marianna Marchini
- Dipartimento di Chimica “G. Ciamician” Alma Mater Studiorum – Università di Bologna Via Selmi 2 40126 Bologna Italy
| | - Giacomo Rodeghiero
- Dipartimento di Chimica “G. Ciamician” Alma Mater Studiorum – Università di Bologna Via Selmi 2 40126 Bologna Italy
- Cyanagen Srl Via Stradelli Guelfi 40/C 40138 Bologna Italy
| | - Irene Conti
- Dipartimento di Chimica Industriale “T. Montanari” Alma Mater Studiorum – Università di Bologna Viale Risorgimento 4 40136 Bologna Italy
| | - Ettore Paltanin
- Dipartimento di Chimica Industriale “T. Montanari” Alma Mater Studiorum – Università di Bologna Viale Risorgimento 4 40136 Bologna Italy
| | - Matteo Balletti
- Dipartimento di Chimica “G. Ciamician” Alma Mater Studiorum – Università di Bologna Via Selmi 2 40126 Bologna Italy
| | - Paola Ceroni
- Dipartimento di Chimica “G. Ciamician” Alma Mater Studiorum – Università di Bologna Via Selmi 2 40126 Bologna Italy
| | - Marco Garavelli
- Dipartimento di Chimica Industriale “T. Montanari” Alma Mater Studiorum – Università di Bologna Viale Risorgimento 4 40136 Bologna Italy
| | - Pier Giorgio Cozzi
- Dipartimento di Chimica “G. Ciamician” Alma Mater Studiorum – Università di Bologna Via Selmi 2 40126 Bologna Italy
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68
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Yang JY, Kerr TA, Wang XS, Barlow JM. Reducing CO2 to HCO2– at Mild Potentials: Lessons from Formate Dehydrogenase. J Am Chem Soc 2020; 142:19438-19445. [DOI: 10.1021/jacs.0c07965] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Affiliation(s)
- Jenny Y. Yang
- Department of Chemistry, University of California, Irvine, California 92697, United States
| | - Tyler A. Kerr
- Department of Chemistry, University of California, Irvine, California 92697, United States
| | - Xinran S. Wang
- Department of Chemistry, University of California, Irvine, California 92697, United States
| | - Jeffrey M. Barlow
- Department of Chemistry, University of California, Irvine, California 92697, United States
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69
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Reinhardt CR, Li P, Kang G, Stubbe J, Drennan CL, Hammes-Schiffer S. Conformational Motions and Water Networks at the α/β Interface in E. coli Ribonucleotide Reductase. J Am Chem Soc 2020; 142:13768-13778. [PMID: 32631052 DOI: 10.1021/jacs.0c04325] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Ribonucleotide reductases (RNRs) catalyze the conversion of all four ribonucleotides to deoxyribonucleotides and are essential for DNA synthesis in all organisms. The active form of E. coli Ia RNR is composed of two homodimers that form the active α2β2 complex. Catalysis is initiated by long-range radical translocation over a ∼32 Å proton-coupled electron transfer (PCET) pathway involving Y356β and Y731α at the interface. Resolving the PCET pathway at the α/β interface has been a long-standing challenge due to the lack of structural data. Herein, molecular dynamics simulations based on a recently solved cryogenic-electron microscopy structure of an active α2β2 complex are performed to examine the structure and fluctuations of interfacial water, as well as the hydrogen-bonding interactions and conformational motions of interfacial residues along the PCET pathway. Our free energy simulations reveal that Y731 is able to sample both a flipped-out conformation, where it points toward the interface to facilitate interfacial PCET with Y356, and a stacked conformation with Y730 to enable collinear PCET with this residue. Y356 and Y731 exhibit hydrogen-bonding interactions with interfacial water molecules and, in some conformations, share a bridging water molecule, suggesting that the primary proton acceptor for PCET from Y356 and from Y731 is interfacial water. The conformational flexibility of Y731 and the hydrogen-bonding interactions of both Y731 and Y356 with interfacial water and hydrogen-bonded water chains appear critical for effective radical translocation along the PCET pathway. These simulations are consistent with biochemical and spectroscopic data and provide previously unattainable atomic-level insights into the fundamental mechanism of RNR.
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Affiliation(s)
- Clorice R Reinhardt
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven Connecticut 06520, United States
| | - Pengfei Li
- Department of Chemistry, Yale University, New Haven Connecticut 06520, United States
| | - Gyunghoon Kang
- Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge Massachusetts 02139, United States.,Department of Chemistry, Massachusetts Institute of Technology, Cambridge Massachusetts 02139, United States
| | - JoAnne Stubbe
- Department of Biology, Massachusetts Institute of Technology, Cambridge Massachusetts 02139, United States.,Department of Chemistry, Massachusetts Institute of Technology, Cambridge Massachusetts 02139, United States
| | - Catherine L Drennan
- Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge Massachusetts 02139, United States.,Department of Biology, Massachusetts Institute of Technology, Cambridge Massachusetts 02139, United States.,Department of Chemistry, Massachusetts Institute of Technology, Cambridge Massachusetts 02139, United States.,Fellow, Bio-inspired Solar Energy Program, Canadian Institute for Advanced Research (CIFAR), Toronto, ON M5G 1M1, Canada
| | - Sharon Hammes-Schiffer
- Department of Chemistry, Yale University, New Haven Connecticut 06520, United States.,Fellow, Bio-inspired Solar Energy Program, Canadian Institute for Advanced Research (CIFAR), Toronto, ON M5G 1M1, Canada
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70
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Koronkiewicz B, Swierk J, Regan K, Mayer JM. Shallow Distance Dependence for Proton-Coupled Tyrosine Oxidation in Oligoproline Peptides. J Am Chem Soc 2020; 142:12106-12118. [PMID: 32510937 PMCID: PMC7545454 DOI: 10.1021/jacs.0c01429] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
We have explored the kinetic effect of increasing electron transfer (ET) distance in a biomimetic, proton-coupled electron-transfer (PCET) system. Biological ET often occurs simultaneously with proton transfer (PT) in order to avoid the high-energy, charged intermediates resulting from the stepwise transfer of protons and electrons. These concerted proton-electron-transfer (CPET) reactions are implicated in numerous biological ET pathways. In many cases, PT is coupled to long-range ET. While many studies have shown that the rate of ET is sensitive to the distance between the electron donor and acceptor, extensions to biological CPET reactions are sparse. The possibility of a unique ET distance dependence for CPET reactions deserves further exploration, as this could have implications for how we understand biological ET. We therefore explored the ET distance dependence for the CPET oxidation of tyrosine in a model system. We prepared a series of metallopeptides with a tyrosine separated from a Ru(bpy)32+ complex by an oligoproline bridge of increasing length. Rate constants for intramolecular tyrosine oxidation were measured using the flash-quench transient absorption technique in aqueous solutions. The rate constants for tyrosine oxidation decreased by 125-fold with three added proline residues between tyrosine and the oxidant. By comparison, related intramolecular ET rate constants in very similar constructs were reported to decrease by 4-5 orders of magnitude over the same number of prolines. The observed shallow distance dependence for tyrosine oxidation is proposed to originate in part from the requirement for stronger oxidants, leading to a smaller hole-transfer effective tunneling barrier height. The shallow distance dependence observed here and extensions to distance-dependent CPET reactions have potential implications for long-range charge transfers.
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Affiliation(s)
- Brian Koronkiewicz
- Department of Chemistry, Yale University, New Haven, Connecticut 06520-8107, United States
| | - John Swierk
- Department of Chemistry, Yale University, New Haven, Connecticut 06520-8107, United States
| | - Kevin Regan
- Department of Chemistry, Yale University, New Haven, Connecticut 06520-8107, United States
| | - James M Mayer
- Department of Chemistry, Yale University, New Haven, Connecticut 06520-8107, United States
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71
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Ferousi C, Majer SH, DiMucci IM, Lancaster KM. Biological and Bioinspired Inorganic N-N Bond-Forming Reactions. Chem Rev 2020; 120:5252-5307. [PMID: 32108471 PMCID: PMC7339862 DOI: 10.1021/acs.chemrev.9b00629] [Citation(s) in RCA: 46] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The metallobiochemistry underlying the formation of the inorganic N-N-bond-containing molecules nitrous oxide (N2O), dinitrogen (N2), and hydrazine (N2H4) is essential to the lifestyles of diverse organisms. Similar reactions hold promise as means to use N-based fuels as alternative carbon-free energy sources. This review discusses research efforts to understand the mechanisms underlying biological N-N bond formation in primary metabolism and how the associated reactions are tied to energy transduction and organismal survival. These efforts comprise studies of both natural and engineered metalloenzymes as well as synthetic model complexes.
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Affiliation(s)
- Christina Ferousi
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853, United States
| | - Sean H Majer
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853, United States
| | - Ida M DiMucci
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853, United States
| | - Kyle M Lancaster
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853, United States
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72
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Ravichandran K, Olshansky L, Nocera DG, Stubbe J. Subunit Interaction Dynamics of Class Ia Ribonucleotide Reductases: In Search of a Robust Assay. Biochemistry 2020; 59:1442-1453. [PMID: 32186371 PMCID: PMC7160020 DOI: 10.1021/acs.biochem.0c00001] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Ribonucleotide reductases (RNRs) catalyze the conversion of nucleotides (NDP) to deoxynucleotides (dNDP), in part, by controlling the ratios and quantities of dNTPs available for DNA replication and repair. The active form of Escherichia coli class Ia RNR is an asymmetric α2β2 complex in which α2 contains the active site and β2 contains the stable diferric-tyrosyl radical cofactor responsible for initiating the reduction chemistry. Each dNDP is accompanied by disulfide bond formation. We now report that, under in vitro conditions, β2 can initiate turnover in α2 catalytically under both "one" turnover (no external reductant, though producing two dCDPs) and multiple turnover (with an external reductant) assay conditions. In the absence of reductant, rapid chemical quench analysis of a reaction of α2, substrate, and effector with variable amounts of β2 (1-, 10-, and 100-fold less than α2) yields 3 dCDP/α2 at all ratios of α2:β2 with a rate constant of 8-9 s-1, associated with a rate-limiting conformational change. Stopped-flow fluorescence spectroscopy with a fluorophore-labeled β reveals that the rate constants for subunit association (163 ± 7 μM-1 s-1) and dissociation (75 ± 10 s-1) are fast relative to turnover, consistent with catalytic β2. When assaying in the presence of an external reducing system, the turnover number is dictated by the ratio of α2:β2, their concentrations, and the concentration and nature of the reducing system; the rate-limiting step can change from the conformational gating to a step or steps involving disulfide rereduction, dissociation of the inhibited α4β4 state, or both. The issues encountered with E. coli RNR are likely of importance in all class I RNRs and are central to understanding the development of screening assays for inhibitors of these enzymes.
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Affiliation(s)
- Kanchana Ravichandran
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139
| | - Lisa Olshansky
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139
- Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, MA 02138
| | - Daniel G. Nocera
- Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, MA 02138
| | - JoAnne Stubbe
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139
- Department of Biology, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139
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73
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Tyson KJ, Davis AN, Norris JL, Bartolotti LJ, Hvastkovs EG, Offenbacher AR. Impact of Local Electrostatics on the Redox Properties of Tryptophan Radicals in Azurin: Implications for Redox-Active Tryptophans in Proton-Coupled Electron Transfer. J Phys Chem Lett 2020; 11:2408-2413. [PMID: 32134666 DOI: 10.1021/acs.jpclett.0c00614] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Tyrosine and tryptophan play critical roles in facilitating proton-coupled electron transfer (PCET) processes essential to life. The local protein environment is anticipated to modulate the thermodynamics of amino acid radicals to achieve controlled, unidirectional PCET. Herein, square-wave voltammetry was employed to investigate the electrostatic effects on the redox properties of tryptophan in two variants of the protein azurin. Each variant contains a single redox-active tryptophan, W48 or W108, in a unique and buried protein environment. These tryptophan residues exhibit reversible square-wave voltammograms. A Pourbaix plot, representing the reduction potentials versus pH, is presented for the non-H-bonded W48, which has potentials comparable to those of tryptophan in solution. The reduction potentials of W108 are seen to be increased by more than 100 mV across the same pH range. Molecular dynamics shows that, despite its buried indole ring, the N-H of W108 hydrogen bonds with a water cluster, while W48 is completely excluded from interactions with water or polar groups. These redox properties provide insight into the role of the protein in tuning the reactivity of tryptophan radicals, a requirement for controlled biological PCET.
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Affiliation(s)
- Kristin J Tyson
- Department of Chemistry, East Carolina University, Greenville, North Carolina 27858, United States
| | - Amanda N Davis
- Department of Chemistry, East Carolina University, Greenville, North Carolina 27858, United States
| | - Jessica L Norris
- Department of Chemistry, East Carolina University, Greenville, North Carolina 27858, United States
| | - Libero J Bartolotti
- Department of Chemistry, East Carolina University, Greenville, North Carolina 27858, United States
| | - Eli G Hvastkovs
- Department of Chemistry, East Carolina University, Greenville, North Carolina 27858, United States
| | - Adam R Offenbacher
- Department of Chemistry, East Carolina University, Greenville, North Carolina 27858, United States
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74
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Odella E, Mora SJ, Wadsworth BL, Goings JJ, Gervaldo MA, Sereno LE, Groy TL, Gust D, Moore TA, Moore GF, Hammes-Schiffer S, Moore AL. Proton-coupled electron transfer across benzimidazole bridges in bioinspired proton wires. Chem Sci 2020; 11:3820-3828. [PMID: 34122850 PMCID: PMC8152432 DOI: 10.1039/c9sc06010c] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
Abstract
Designing molecular platforms for controlling proton and electron movement in artificial photosynthetic systems is crucial to efficient catalysis and solar energy conversion. The transfer of both protons and electrons during a reaction is known as proton-coupled electron transfer (PCET) and is used by nature in myriad ways to provide low overpotential pathways for redox reactions and redox leveling, as well as to generate bioenergetic proton currents. Herein, we describe theoretical and electrochemical studies of a series of bioinspired benzimidazole-phenol (BIP) derivatives and a series of dibenzimidazole-phenol (BI2P) analogs with each series bearing the same set of terminal proton-accepting (TPA) groups. The set of TPAs spans more than 6 pKa units. These compounds have been designed to explore the role of the bridging benzimidazole(s) in a one-electron oxidation process coupled to intramolecular proton translocation across either two (the BIP series) or three (the BI2P series) acid/base sites. These molecular constructs feature an electrochemically active phenol connected to the TPA group through a benzimidazole-based bridge, which together with the phenol and TPA group form a covalent framework supporting a Grotthuss-type hydrogen-bonded network. Infrared spectroelectrochemistry demonstrates that upon oxidation of the phenol, protons translocate across this well-defined hydrogen-bonded network to a TPA group. The experimental data show the benzimidazole bridges are non-innocent participants in the PCET process in that the addition of each benzimidazole unit lowers the redox potential of the phenoxyl radical/phenol couple by 60 mV, regardless of the nature of the TPA group. Using a series of hypothetical thermodynamic steps, density functional theory calculations correctly predicted the dependence of the redox potential of the phenoxyl radical/phenol couple on the nature of the final protonated species and provided insight into the thermodynamic role of dibenzimidazole units in the PCET process. This information is crucial for developing molecular “dry proton wires” with these moieties, which can transfer protons via a Grotthuss-type mechanism over long distances without the intervention of water molecules. Experimental and theoretical methods characterize the thermodynamics of electrochemically driven proton-coupled electron transfer processes in bioinspired constructs involving multiple proton translocations over Grotthus-type proton wires.![]()
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Affiliation(s)
- Emmanuel Odella
- School of Molecular Sciences, Arizona State University Tempe Arizona 85287-1604 USA
| | - S Jimena Mora
- School of Molecular Sciences, Arizona State University Tempe Arizona 85287-1604 USA
| | - Brian L Wadsworth
- School of Molecular Sciences, Arizona State University Tempe Arizona 85287-1604 USA
| | - Joshua J Goings
- Department of Chemistry, Yale University New Haven Connecticut 06520-8107 USA
| | - Miguel A Gervaldo
- Departamento de Química, Facultad de Ciencias Exactas, Físico-Químicas y Naturales, Universidad Nacional de Río Cuarto Agencia Postal No 3 5800 Río Cuarto Córdoba Argentina
| | - Leonides E Sereno
- Departamento de Química, Facultad de Ciencias Exactas, Físico-Químicas y Naturales, Universidad Nacional de Río Cuarto Agencia Postal No 3 5800 Río Cuarto Córdoba Argentina
| | - Thomas L Groy
- School of Molecular Sciences, Arizona State University Tempe Arizona 85287-1604 USA
| | - Devens Gust
- School of Molecular Sciences, Arizona State University Tempe Arizona 85287-1604 USA
| | - Thomas A Moore
- School of Molecular Sciences, Arizona State University Tempe Arizona 85287-1604 USA
| | - Gary F Moore
- School of Molecular Sciences, Arizona State University Tempe Arizona 85287-1604 USA
| | | | - Ana L Moore
- School of Molecular Sciences, Arizona State University Tempe Arizona 85287-1604 USA
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75
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Li S, Chen W, Hu X, Feng F. Self-Assembly of Albumin and [FeFe]-Hydrogenase Mimics for Photocatalytic Hydrogen Evolution. ACS APPLIED BIO MATERIALS 2020; 3:2482-2488. [DOI: 10.1021/acsabm.0c00194] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Shuyi Li
- Key Laboratory of High Performance Polymer Material and Technology of Ministry of Education, Department of Polymer Science & Engineering, School of Chemistry & Chemical Engineering, Nanjing University, Nanjing 210023, China
| | - Weijian Chen
- Key Laboratory of High Performance Polymer Material and Technology of Ministry of Education, Department of Polymer Science & Engineering, School of Chemistry & Chemical Engineering, Nanjing University, Nanjing 210023, China
| | - Xiantao Hu
- Key Laboratory of High Performance Polymer Material and Technology of Ministry of Education, Department of Polymer Science & Engineering, School of Chemistry & Chemical Engineering, Nanjing University, Nanjing 210023, China
| | - Fude Feng
- Key Laboratory of High Performance Polymer Material and Technology of Ministry of Education, Department of Polymer Science & Engineering, School of Chemistry & Chemical Engineering, Nanjing University, Nanjing 210023, China
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76
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Drienovská I, Roelfes G. Expanding the enzyme universe with genetically encoded unnatural amino acids. Nat Catal 2020. [DOI: 10.1038/s41929-019-0410-8] [Citation(s) in RCA: 86] [Impact Index Per Article: 21.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
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77
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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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78
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Morozova OB. Reduction of Transient Histidine Radicals by Tyrosine: Influence of the Protonation State of Reactants. Chemphyschem 2020; 21:43-50. [PMID: 31709709 DOI: 10.1002/cphc.201901020] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2019] [Indexed: 11/07/2022]
Abstract
The role of tyrosine radicals as mediators of electron transfer reactions in enzymes is well established, as is the involvement of histidine as a binding partner. But how environmental factors affect these reactions remains poorly explored. In the study presented here, kinetic data on the influence of the protonation state of the reactants on the reduction of transient histidine radicals by tyrosine were obtained in neutral and basic aqueous solution (pH 6-12) using time-resolved chemically induced dynamic nuclear polarization (CIDNP). The histidine radicals were generated in the photo-induced reaction with the photosensitizer 3,3',4,4'-tetracarboxy benzophenone. From model simulations of the detected CIDNP kinetics, pH dependent second-order rate constants of the reduction of histidine radicals were obtained for four possible combinations of the amino acids and their N-acetyl derivatives, and also for the systems histidine-phenylalanine dipeptide/N-acetyl tyrosine, and N-acetyl histidine/tyrosine-glutamine dipeptide. The pH dependences of the rate constant of the reduction reaction are explained accounting for the protonation states of reactants, and also protonation state of the equilibrium form of the product - reduced form of histidine radical, which is histidine with neutral or a positively charged imidazole.
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Affiliation(s)
- Olga B Morozova
- International Tomography Center, Institutskaya 3a, 630090, Novosibirsk, Russia.,Novosibirsk State University, Pirogova 2, 630090, Novosibirsk, Russia
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79
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Yu J, Horsley JR, Abell AD. Unravelling electron transfer in peptide-cation complexes: a model for mimicking redox centres in proteins. Phys Chem Chem Phys 2020; 22:8409-8417. [DOI: 10.1039/d0cp00635a] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
We provide evidence that bound zinc promotes electron transfer in a peptide by changing the electronic properties of the peptide.
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Affiliation(s)
- Jingxian Yu
- ARC Centre of Excellence for Nanoscale BioPhotonics (CNBP)
- Institute of Photonics and Advanced Sensing (IPAS)
- Department of Chemistry
- The University of Adelaide
- Adelaide
| | - John R. Horsley
- ARC Centre of Excellence for Nanoscale BioPhotonics (CNBP)
- Institute of Photonics and Advanced Sensing (IPAS)
- Department of Chemistry
- The University of Adelaide
- Adelaide
| | - Andrew D. Abell
- ARC Centre of Excellence for Nanoscale BioPhotonics (CNBP)
- Institute of Photonics and Advanced Sensing (IPAS)
- Department of Chemistry
- The University of Adelaide
- Adelaide
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80
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D'Amore L, Belpassi L, Klein JEMN, Swart M. Spin-resolved charge displacement analysis as an intuitive tool for the evaluation of cPCET and HAT scenarios. Chem Commun (Camb) 2020; 56:12146-12149. [DOI: 10.1039/d0cc04995f] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The spin-resolved version of the charge displacement function is introduced as an intuitive tool for differentiating between hydrogen-atom transfer and concerted proton-coupled electron transfer.
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Affiliation(s)
- Lorenzo D'Amore
- IQCC and Dept. Chem
- Universitat de Girona
- Campus Montilivi
- 17003 Girona
- Spain
| | - Leonardo Belpassi
- Istituto di Scienze e Tecnologie Chimiche del CNR (SCITEC-CNR) c/o Università degli Studi di Perugia
- Via Elce di Sotto 8
- 06123 Perugia
- Italy
| | - Johannes E. M. N. Klein
- Molecular Inorganic Chemistry
- Stratingh Institute for Chemistry
- Faculty of Science and Engineering
- University of Groningen
- Groningen
| | - Marcel Swart
- IQCC and Dept. Chem
- Universitat de Girona
- Campus Montilivi
- 17003 Girona
- Spain
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81
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Yee EF, Dzikovski B, Crane BR. Tuning Radical Relay Residues by Proton Management Rescues Protein Electron Hopping. J Am Chem Soc 2019; 141:17571-17587. [PMID: 31603693 DOI: 10.1021/jacs.9b05715] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Transient tyrosine and tryptophan radicals play key roles in the electron transfer (ET) reactions of photosystem (PS) II, ribonucleotide reductase (RNR), photolyase, and many other proteins. However, Tyr and Trp are not functionally interchangeable, and the factors controlling their reactivity are often unclear. Cytochrome c peroxidase (CcP) employs a Trp191•+ radical to oxidize reduced cytochrome c (Cc). Although a Tyr191 replacement also forms a stable radical, it does not support rapid ET from Cc. Here we probe the redox properties of CcP Y191 by non-natural amino acid substitution, altering the ET driving force and manipulating the protic environment of Y191. Higher potential fluorotyrosine residues increase ET rates marginally, but only addition of a hydrogen bond donor to Tyr191• (via Leu232His or Glu) substantially alters activity by increasing the ET rate by nearly 30-fold. ESR and ESEEM spectroscopies, crystallography, and pH-dependent ET kinetics provide strong evidence for hydrogen bond formation to Y191• by His232/Glu232. Rate measurements and rapid freeze quench ESR spectroscopy further reveal differences in radical propagation and Cc oxidation that support an increased Y191• formal potential of ∼200 mV in the presence of E232. Hence, Y191 inactivity results from a potential drop owing to Y191•+ deprotonation. Incorporation of a well-positioned base to accept and donate back a hydrogen bond upshifts the Tyr• potential into a range where it can effectively oxidize Cc. These findings have implications for the YZ/YD radicals of PS II, hole-hopping in RNR and cryptochrome, and engineering proteins for long-range ET reactions.
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Affiliation(s)
- Estella F Yee
- Department of Chemistry and Chemical Biology , Cornell University , Ithaca , New York 14853 , United States
| | - Boris Dzikovski
- Department of Chemistry and Chemical Biology , Cornell University , Ithaca , New York 14853 , United States.,National Biomedical Center for Advanced ESR Technologies (ACERT) , Cornell University , Ithaca , New York 14850 , United States
| | - Brian R Crane
- Department of Chemistry and Chemical Biology , Cornell University , Ithaca , New York 14853 , United States
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82
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Samanta D, Saha P, Ghosh P. Proton-Coupled Oxidation of Aldimines and Stabilization of H-Bonded Phenoxyl Radical-Phenol Skeletons. Inorg Chem 2019; 58:15060-15077. [DOI: 10.1021/acs.inorgchem.9b01568] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Debasish Samanta
- Department of Chemistry, R. K. Mission Residential College, Narendrapur, Kolkata 700103, India
| | - Pinaki Saha
- Department of Chemistry, R. K. Mission Residential College, Narendrapur, Kolkata 700103, India
| | - Prasanta Ghosh
- Department of Chemistry, R. K. Mission Residential College, Narendrapur, Kolkata 700103, India
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83
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Sayfutyarova ER, Lam YC, Hammes-Schiffer S. Strategies for Enhancing the Rate Constant of C-H Bond Cleavage by Concerted Proton-Coupled Electron Transfer. J Am Chem Soc 2019; 141:15183-15189. [PMID: 31464122 DOI: 10.1021/jacs.9b06849] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Recently selective C-H bond cleavage under mild conditions with weak oxidants was reported for fluorenyl-benzoates. This mechanism is based on multi-site concerted proton-coupled electron transfer (PCET) involving intermolecular electron transfer to an outer-sphere oxidant coupled to intramolecular proton transfer to a well-positioned proton acceptor. The electron transfer driving force depends predominantly on the oxidant, and the proton transfer driving force depends mainly on the basicity of the carboxylate, which is influenced by the substituent on the benzoate fragment. Experiments showed that the rate constants are much more sensitive to the carboxylate basicity than to the redox potential of the oxidant. Herein a vibronically nonadiabatic PCET theory is used to explain how changing the driving force for the electron and proton transfer components of the reaction through varying the oxidant and the substituent, respectively, impacts the PCET rate constant. In addition to increasing the driving force for proton transfer, enhancing the basicity of the carboxylate also decreases the equilibrium proton donor-acceptor distance, thereby facilitating the sampling of shorter proton donor-acceptor distances. This additional effect arising from the strong dependence of proton transfer on the proton donor-acceptor distance provides an explanation for the greater sensitivity of the rate constant to the carboxylate basicity than to the redox potential of the oxidant. These fundamental insights have broad implications for developing new strategies to activate C-H bonds, specifically by designing systems with shorter equilibrium proton donor-acceptor distances.
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Affiliation(s)
- Elvira R Sayfutyarova
- Department of Chemistry , Yale University , 225 Prospect Street , New Haven , Connecticut 06520 , United States
| | - Yan-Choi Lam
- Department of Chemistry , Yale University , 225 Prospect Street , New Haven , Connecticut 06520 , United States
| | - Sharon Hammes-Schiffer
- Department of Chemistry , Yale University , 225 Prospect Street , New Haven , Connecticut 06520 , United States
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84
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North ML, Wilcox DE. Shift from Entropic Cu 2+ Binding to Enthalpic Cu + Binding Determines the Reduction Thermodynamics of Blue Copper Proteins. J Am Chem Soc 2019; 141:14329-14339. [PMID: 31433629 DOI: 10.1021/jacs.9b06836] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The enthalpic and entropic components of Cu2+ and Cu+ binding to the blue copper protein azurin have been quantified with isothermal titration calorimetry (ITC) measurements and analysis, providing the first such experimental values for Cu+ binding to a protein. The high affinity of azurin for Cu2+ is entirely due to a very favorable binding entropy, while its even higher affinity for Cu+ is due to a favorable binding enthalpy and entropy. The binding thermodynamics provide insight into bond enthalpies at the blue copper site and entropic contributions from desolvation and proton displacement. These values were used in thermodynamic cycles to determine the enthalpic and entropic contributions to the free energy of reduction and thus the reduction potential. The reduction thermodynamics obtained with this method are in good agreement with previous results from temperature-dependent electrochemical measurements. The calorimetry method, however, provides new insight into contributions from the initial (oxidized) and final (reduced) states of the reduction. Since ITC measurements quantify the protons that are displaced upon metal binding, the proton transfer that is coupled with electron transfer is also determined with this method. Preliminary results for Cu2+ and Cu+ binding to the Phe114Pro variant of azurin demonstrate the insight about protein tuning of the reduction potential that is provided by the binding thermodynamics of each metal oxidation state.
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Affiliation(s)
- Molly L North
- Department of Chemistry , Dartmouth College , Hanover , New Hampshire 03755 , United States
| | - Dean E Wilcox
- Department of Chemistry , Dartmouth College , Hanover , New Hampshire 03755 , United States
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85
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The interaction between methionine and two aromatic amino acids is an abundant and multifunctional motif in proteins. Arch Biochem Biophys 2019; 672:108053. [DOI: 10.1016/j.abb.2019.07.018] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2019] [Revised: 07/08/2019] [Accepted: 07/24/2019] [Indexed: 12/29/2022]
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86
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Class Id ribonucleotide reductase utilizes a Mn 2(IV,III) cofactor and undergoes large conformational changes on metal loading. J Biol Inorg Chem 2019; 24:863-877. [PMID: 31414238 PMCID: PMC6754362 DOI: 10.1007/s00775-019-01697-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2019] [Accepted: 08/02/2019] [Indexed: 12/15/2022]
Abstract
Outside of the photosynthetic machinery, high-valent manganese cofactors are rare in biology. It was proposed that a recently discovered subclass of ribonucleotide reductase (RNR), class Id, is dependent on a Mn2(IV,III) cofactor for catalysis. Class I RNRs consist of a substrate-binding component (NrdA) and a metal-containing radical-generating component (NrdB). Herein we utilize a combination of EPR spectroscopy and enzyme assays to underscore the enzymatic relevance of the Mn2(IV,III) cofactor in class Id NrdB from Facklamia ignava. Once formed, the Mn2(IV,III) cofactor confers enzyme activity that correlates well with cofactor quantity. Moreover, we present the X-ray structure of the apo- and aerobically Mn-loaded forms of the homologous class Id NrdB from Leeuwenhoekiella blandensis, revealing a dimanganese centre typical of the subclass, with a tyrosine residue maintained at distance from the metal centre and a lysine residue projected towards the metals. Structural comparison of the apo- and metal-loaded forms of the protein reveals a refolding of the loop containing the conserved lysine and an unusual shift in the orientation of helices within a monomer, leading to the opening of a channel towards the metal site. Such major conformational changes have not been observed in NrdB proteins before. Finally, in vitro reconstitution experiments reveal that the high-valent manganese cofactor is not formed spontaneously from oxygen, but can be generated from at least two different reduced oxygen species, i.e. H2O2 and superoxide (O 2 ·- ). Considering the observed differences in the efficiency of these two activating reagents, we propose that the physiologically relevant mechanism involves superoxide.
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87
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Odella E, Wadsworth BL, Mora SJ, Goings JJ, Huynh MT, Gust D, Moore TA, Moore GF, Hammes-Schiffer S, Moore AL. Proton-Coupled Electron Transfer Drives Long-Range Proton Translocation in Bioinspired Systems. J Am Chem Soc 2019; 141:14057-14061. [DOI: 10.1021/jacs.9b06978] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Affiliation(s)
- Emmanuel Odella
- School of Molecular Sciences, Arizona State University, Tempe, Arizona 85287-1604, United States
| | - Brian L. Wadsworth
- School of Molecular Sciences, Arizona State University, Tempe, Arizona 85287-1604, United States
| | - S. Jimena Mora
- School of Molecular Sciences, Arizona State University, Tempe, Arizona 85287-1604, United States
| | - Joshua J. Goings
- Department of Chemistry, Yale University, New Haven, Connecticut 06520-8107, United States
| | - Mioy T. Huynh
- Department of Chemistry, Yale University, New Haven, Connecticut 06520-8107, United States
| | - Devens Gust
- School of Molecular Sciences, Arizona State University, Tempe, Arizona 85287-1604, United States
| | - Thomas A. Moore
- School of Molecular Sciences, Arizona State University, Tempe, Arizona 85287-1604, United States
| | - Gary F. Moore
- School of Molecular Sciences, Arizona State University, Tempe, Arizona 85287-1604, United States
| | - Sharon Hammes-Schiffer
- Department of Chemistry, Yale University, New Haven, Connecticut 06520-8107, United States
| | - Ana L. Moore
- School of Molecular Sciences, Arizona State University, Tempe, Arizona 85287-1604, United States
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88
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Maróti P. Thermodynamic View of Proton Activated Electron Transfer in the Reaction Center of Photosynthetic Bacteria. J Phys Chem B 2019; 123:5463-5473. [PMID: 31181159 DOI: 10.1021/acs.jpcb.9b03506] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The temperature dependence of the sequential coupling of proton transfer to the second interquinone electron transfer is studied in the reaction center proteins of photosynthetic bacteria modified by different mutations and treatment by divalent cations. The Eyring plots of kinetics were evaluated by the Marcus theory of electron and proton transfer. In mutants of electron transfer limitation (including the wild type), the observed thermodynamic parameters had to be corrected for those of the fast proton pre-equilibrium. The electron transfer is nonadiabatic with transmission coefficient 6 × 10-4, and the reorganization energy amounts to 1.2 eV. If the proton transfer is the rate limiting step, the reorganization energy and the works terms fall in the range of 200-500 meV, depending on the site of damage in the proton transfer chain. The product term is 100-150 meV larger than the reactant term. While the electron transfer mutants have a low free energy of activation (∼200 meV), the proton transfer variants show significantly elevated levels of the free energy barrier (∼500 meV). The second electron transfer in the bacterial reaction center can serve as a model system of coupled electron and proton transfer in other proteins or ion channels.
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Affiliation(s)
- Péter Maróti
- Institute of Medical Physics , University of Szeged , Rerrich Béla tér 1 , Szeged , H-6720 , Hungary
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89
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Ultrafast structural rearrangement dynamics induced by the photodetachment of phenoxide in aqueous solution. Nat Commun 2019; 10:2944. [PMID: 31270331 PMCID: PMC6610110 DOI: 10.1038/s41467-019-10989-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2019] [Accepted: 06/14/2019] [Indexed: 01/28/2023] Open
Abstract
The elementary processes that accompany the interaction of ionizing radiation with biologically relevant molecules are of fundamental importance. However, the ultrafast structural rearrangement dynamics induced by the ionization of biomolecules in aqueous solution remain hitherto unknown. Here, we employ femtosecond optical pump-probe spectroscopy to elucidate the vibrational wave packet dynamics that follow the photodetachment of phenoxide, a structural mimic of tyrosine, in aqueous solution. Photodetachment of phenoxide leads to wave packet dynamics of the phenoxyl radical along 12 different vibrational modes. Eight of the modes are totally symmetric and support structural rearrangement upon electron ejection. Comparison to a previous photodetachment study of phenoxide in the gas phase reveals the important role played by the solvent environment in driving ultrafast structural reorganization induced by ionizing radiation. This work provides insight into the ultrafast molecular dynamics that follow the interaction of ionizing radiation with molecules in aqueous solution. The interaction of biomolecules with ionizing radiation induces structural changes which are still largely unknown. The authors use femtosecond wave packet spectroscopy to observe ultrafast structural dynamics that follow the photodetachment of phenoxide in aqueous solution.
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90
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Sandoval BA, Kurtoic SI, Chung MM, Biegasiewicz KF, Hyster TK. Photoenzymatic Catalysis Enables Radical-Mediated Ketone Reduction in Ene-Reductases. Angew Chem Int Ed Engl 2019; 58:8714-8718. [PMID: 30951226 PMCID: PMC6570536 DOI: 10.1002/anie.201902005] [Citation(s) in RCA: 66] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2019] [Revised: 03/22/2019] [Indexed: 11/12/2022]
Abstract
Flavin-dependent ene-reductases (EREDs) are known to stereoselectively reduce activated alkenes, but are inactive toward carbonyls. Demonstrated here is that in the presence of photoredox catalysts, these enzymes will reduce aromatic ketones. Mechanistic experiments suggest this reaction proceeds through ketyl radical formation, a reaction pathway that is distinct from the native hydride-transfer mechanism. Furthermore, this reactivity is accessible without modification of either the enzyme or cofactors, allowing both native and non-natural mechanisms to occur simultaneously. Based on control experiments, we hypothesize that binding to the enzyme active site attenuates the reduction potential of the substrate, enabling single-electron reduction. This reactivity highlights opportunities to access new catalytic manifolds by merging photoredox catalysis with biocatalysis.
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Affiliation(s)
- Braddock A Sandoval
- Department of Chemistry, Princeton University, Frick Chemical Laboratory, Princeton, NJ, 08544, USA
| | - Sarah I Kurtoic
- Department of Chemistry, Princeton University, Frick Chemical Laboratory, Princeton, NJ, 08544, USA
| | - Megan M Chung
- Department of Chemistry, Princeton University, Frick Chemical Laboratory, Princeton, NJ, 08544, USA
| | - Kyle F Biegasiewicz
- Department of Chemistry, Princeton University, Frick Chemical Laboratory, Princeton, NJ, 08544, USA
| | - Todd K Hyster
- Department of Chemistry, Princeton University, Frick Chemical Laboratory, Princeton, NJ, 08544, USA
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91
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Berggren G, Sahlin M, Crona M, Tholander F, Sjöberg BM. Compounds with capacity to quench the tyrosyl radical in Pseudomonas aeruginosa ribonucleotide reductase. J Biol Inorg Chem 2019; 24:841-848. [PMID: 31218442 PMCID: PMC6754346 DOI: 10.1007/s00775-019-01679-w] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2019] [Accepted: 06/12/2019] [Indexed: 11/02/2022]
Abstract
Ribonucleotide reductase (RNR) has been extensively probed as a target enzyme in the search for selective antibiotics. Here we report on the mechanism of inhibition of nine compounds, serving as representative examples of three different inhibitor classes previously identified by us to efficiently inhibit RNR. The interaction between the inhibitors and Pseudomonas aeruginosa RNR was elucidated using a combination of electron paramagnetic resonance spectroscopy and thermal shift analysis. All nine inhibitors were found to efficiently quench the tyrosyl radical present in RNR, required for catalysis. Three different mechanisms of radical quenching were identified, and shown to depend on reduction potential of the assay solution and quaternary structure of the protein complex. These results form a good foundation for further development of P. aeruginosa selective antibiotics. Moreover, this study underscores the complex nature of RNR inhibition and the need for detailed spectroscopic studies to unravel the mechanism of RNR inhibitors.
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Affiliation(s)
- Gustav Berggren
- Department of Chemistry, Ångström Laboratory, Uppsala University, Uppsala, Sweden.
| | - Margareta Sahlin
- Department of Biochemistry and Biophysics, Stockholm University, Stockholm, Sweden
| | - Mikael Crona
- Department of Biochemistry and Biophysics, Stockholm University, Stockholm, Sweden.,Swedish Orphan Biovitrum AB, Stockholm, Sweden
| | - Fredrik Tholander
- Department of Biochemistry and Biophysics, Stockholm University, Stockholm, Sweden
| | - Britt-Marie Sjöberg
- Department of Biochemistry and Biophysics, Stockholm University, Stockholm, Sweden.
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92
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Zhang J, Lalevée J, Hill NS, Peng X, Zhu D, Kiehl J, Morlet-Savary F, Stenzel MH, Coote ML, Xiao P. Photoinitiation Mechanism and Ability of Monoamino-Substituted Anthraquinone Derivatives as Cationic Photoinitiators of Polymerization under LEDs. Macromol Rapid Commun 2019; 40:e1900234. [PMID: 31210405 DOI: 10.1002/marc.201900234] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2019] [Revised: 06/03/2019] [Indexed: 12/13/2022]
Abstract
The design and development of photoinitiating systems applicable to UV or even visible light delivered from light-emitting diodes (LEDs) has been attracting increasing attention due to their great potential applications in various fields. Compared to the strategy of synthesizing novel compounds, the exploration of existing chemicals with interesting photochemical/photophysical properties for their usage as photoinitiators is more appealing and easily commercialized. Nevertheless, a number of compounds such as monoamino-substituted anthraquinone derivatives, which are intensively investigated for their photophysical and photochemical properties, have seldom been studied for their roles as photoinitiators under LED irradiation. Herein, three monoamino-substituted anthraquinone derivatives, that is, 1-aminoanthraquinone, 1-(methylamino)anthraquinone and 1-(benzamido)anthraquinone, are studied for their potential as photoinitiators. The photoinitiation mechanism of these monoamino-substituted anthraquinone derivatives, when combined with iodonium salt, is first clarified using computational quantum chemistry, fluorescence, steady-state photolysis, and electron spin resonance spin-trapping techniques. Then, their photoinitiation ability for the cationic photopolymerization of epoxide and divinyl ether monomers is also investigated.
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Affiliation(s)
- Jing Zhang
- Research School of Chemistry, Australian National University, Canberra, ACT 2601, Australia.,Université de Haute-Alsace, CNRS, IS2M UMR 7361, F-68100, Mulhouse, France.,School of Chemistry, University of New South Wales, Sydney, NSW, 2052, Australia.,Department of Chemical Engineering, Monash University, Clayton, Victoria, 3800, Australia
| | - Jacques Lalevée
- Université de Haute-Alsace, CNRS, IS2M UMR 7361, F-68100, Mulhouse, France.,Université de Strasbourg, France
| | - Nicholas S Hill
- Research School of Chemistry, Australian National University, Canberra, ACT 2601, Australia.,ARC Centre of Excellence for Electromaterials Science, Research School of Chemistry, Australian National University, Canberra, ACT 2601, Australia
| | - Xiaotong Peng
- Research School of Chemistry, Australian National University, Canberra, ACT 2601, Australia
| | - Di Zhu
- Research School of Chemistry, Australian National University, Canberra, ACT 2601, Australia
| | - Jonathan Kiehl
- School of Chemistry, University of New South Wales, Sydney, NSW, 2052, Australia
| | - Fabrice Morlet-Savary
- Université de Haute-Alsace, CNRS, IS2M UMR 7361, F-68100, Mulhouse, France.,Université de Strasbourg, France
| | - Martina H Stenzel
- School of Chemistry, University of New South Wales, Sydney, NSW, 2052, Australia
| | - Michelle L Coote
- Research School of Chemistry, Australian National University, Canberra, ACT 2601, Australia.,ARC Centre of Excellence for Electromaterials Science, Research School of Chemistry, Australian National University, Canberra, ACT 2601, Australia
| | - Pu Xiao
- Research School of Chemistry, Australian National University, Canberra, ACT 2601, Australia.,Université de Haute-Alsace, CNRS, IS2M UMR 7361, F-68100, Mulhouse, France.,School of Chemistry, University of New South Wales, Sydney, NSW, 2052, Australia
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93
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Schneider J, Bangle RE, Swords WB, Troian-Gautier L, Meyer GJ. Determination of Proton-Coupled Electron Transfer Reorganization Energies with Application to Water Oxidation Catalysts. J Am Chem Soc 2019; 141:9758-9763. [DOI: 10.1021/jacs.9b01296] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Affiliation(s)
- Jenny Schneider
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill 27599, United States
| | - Rachel E. Bangle
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill 27599, United States
| | - Wesley B. Swords
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill 27599, United States
| | - Ludovic Troian-Gautier
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill 27599, United States
| | - Gerald J. Meyer
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill 27599, United States
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94
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Saura P, Frey DM, Gamiz-Hernandez AP, Kaila VRI. Electric field modulated redox-driven protonation and hydration energetics in energy converting enzymes. Chem Commun (Camb) 2019; 55:6078-6081. [PMID: 31066378 PMCID: PMC6932871 DOI: 10.1039/c9cc01135h] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Biological energy conversion is catalysed by proton-coupled electron transfer (PCET) reactions that form the chemical basis of respiratory and photosynthetic enzymes. Despite recent advances in structural, biophysical, and computational experiments, the mechanistic principles of these reactions still remain elusive. Based on common functional features observed in redox enzymes, we study here generic mechanistic models for water-mediated long-range PCET reactions. We show how a redox reaction within a buried protein environment creates an electric field that induces hydration changes between the proton acceptor and donor groups, and in turn, lowers the reaction barrier and increases the thermodynamic driving forces for the water-mediated PCET process. We predict linear free energy relationships, and discuss the proposed mechanism in context of PCET in cytochrome c oxidase.
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Affiliation(s)
- Patricia Saura
- Center for Integrated Protein Science Munich (CIPSM), Department Chemie, Technische Universität München, Lichtenbergstraße 4, 85748, Garching, Germany.
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95
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Sandoval BA, Kurtoic SI, Chung MM, Biegasiewicz KF, Hyster TK. Photoenzymatic Catalysis Enables Radical‐Mediated Ketone Reduction in Ene‐Reductases. Angew Chem Int Ed Engl 2019. [DOI: 10.1002/ange.201902005] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Affiliation(s)
- Braddock A. Sandoval
- Department of ChemistryPrinceton UniversityFrick Chemical Laboratory Princeton NJ 08544 USA
| | - Sarah I. Kurtoic
- Department of ChemistryPrinceton UniversityFrick Chemical Laboratory Princeton NJ 08544 USA
| | - Megan M. Chung
- Department of ChemistryPrinceton UniversityFrick Chemical Laboratory Princeton NJ 08544 USA
| | - Kyle F. Biegasiewicz
- Department of ChemistryPrinceton UniversityFrick Chemical Laboratory Princeton NJ 08544 USA
| | - Todd K. Hyster
- Department of ChemistryPrinceton UniversityFrick Chemical Laboratory Princeton NJ 08544 USA
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96
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Reguera G. Microbial nanowires and electroactive biofilms. FEMS Microbiol Ecol 2019; 94:5000162. [PMID: 29931163 DOI: 10.1093/femsec/fiy086] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2018] [Accepted: 05/11/2018] [Indexed: 12/14/2022] Open
Abstract
Geobacter bacteria are the only microorganisms known to produce conductive appendages or pili to electronically connect cells to extracellular electron acceptors such as iron oxide minerals and uranium. The conductive pili also promote cell-cell aggregation and the formation of electroactive biofilms. The hallmark of these electroactive biofilms is electronic heterogeneity, mediated by coordinated interactions between the conductive pili and matrix-associated cytochromes. Collectively, the matrix-associated electron carriers discharge respiratory electrons from cells in multilayered biofilms to electron-accepting surfaces such as iron oxide coatings and electrodes poised at a metabolically oxidizable potential. The presence of pilus nanowires in the electroactive biofilms also promotes the immobilization and reduction of soluble metals, even when present at toxic concentrations. This review summarizes current knowledge about the composition of the electroactive biofilm matrix and the mechanisms that allow the wired Geobacter biofilms to generate electrical currents and participate in metal redox transformations.
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Affiliation(s)
- Gemma Reguera
- Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI 48824, USA
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97
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Rose HR, Maggiolo AO, McBride MJ, Palowitch GM, Pandelia ME, Davis KM, Yennawar NH, Boal AK. Structures of Class Id Ribonucleotide Reductase Catalytic Subunits Reveal a Minimal Architecture for Deoxynucleotide Biosynthesis. Biochemistry 2019; 58:1845-1860. [PMID: 30855138 PMCID: PMC6456427 DOI: 10.1021/acs.biochem.8b01252] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Class I ribonucleotide reductases (RNRs) share a common mechanism of nucleotide reduction in a catalytic α subunit. All RNRs initiate catalysis with a thiyl radical, generated in class I enzymes by a metallocofactor in a separate β subunit. Class Id RNRs use a simple mechanism of cofactor activation involving oxidation of a MnII2 cluster by free superoxide to yield a metal-based MnIIIMnIV oxidant. This simple cofactor assembly pathway suggests that class Id RNRs may be representative of the evolutionary precursors to more complex class Ia-c enzymes. X-ray crystal structures of two class Id α proteins from Flavobacterium johnsoniae ( Fj) and Actinobacillus ureae ( Au) reveal that this subunit is distinctly small. The enzyme completely lacks common N-terminal ATP-cone allosteric motifs that regulate overall activity, a process that normally occurs by dATP-induced formation of inhibitory quaternary structures to prevent productive β subunit association. Class Id RNR activity is insensitive to dATP in the Fj and Au enzymes evaluated here, as expected. However, the class Id α protein from Fj adopts higher-order structures, detected crystallographically and in solution. The Au enzyme does not exhibit these quaternary forms. Our study reveals structural similarity between bacterial class Id and eukaryotic class Ia α subunits in conservation of an internal auxiliary domain. Our findings with the Fj enzyme illustrate that nucleotide-independent higher-order quaternary structures can form in simple RNRs with truncated or missing allosteric motifs.
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Affiliation(s)
- Hannah R. Rose
- Department of Chemistry, The Pennsylvania State University, University Park, PA 16802
| | - Ailiena O. Maggiolo
- Department of Chemistry, The Pennsylvania State University, University Park, PA 16802
| | - Molly J. McBride
- Department of Chemistry, The Pennsylvania State University, University Park, PA 16802
| | - Gavin M. Palowitch
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA 16802
| | | | - Katherine M. Davis
- Department of Chemistry, The Pennsylvania State University, University Park, PA 16802
| | - Neela H. Yennawar
- Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, PA 16802
| | - Amie K. Boal
- Department of Chemistry, The Pennsylvania State University, University Park, PA 16802
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA 16802
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98
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Song X, Zhang F, Bu Y. Dynamic relaying properties of a β-turn peptide in long-range electron transfer. J Comput Chem 2019; 40:988-996. [PMID: 30451309 DOI: 10.1002/jcc.25541] [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: 04/19/2018] [Revised: 06/30/2018] [Accepted: 07/03/2018] [Indexed: 11/05/2022]
Abstract
The relay stations play a significant role in long-range charge hopping transfer in proteins. Although studies have clarified that many more protein structural motifs can function as relays in charge hopping transfers by acting as intermediate charge carriers, the relaying properties are still poorly understood. In this work, taking a β-turn oligopeptide as an example, we report a dynamic character of a relay with tunable relaying properties using the density functional theory calculations. Our main finding is that a β-turn peptide can serve as an effective electron relay in facilitating long-range electron migration and its relay properties is vibration-tunable. The vibration-induced structural transient distortions remarkably affect the lowest occupied molecular orbital (LUMO) energy, vertical electron affinity and electron-binding mode of the β-turn oligopeptide and the singly occupied molecular orbital (SOMO) energy of the corresponding electron adduct and thus the relaying properties. Different vibration modes lead to different structural distortions and thus have different effects on the relaying properties and ability of the β-turn peptide. For the relaying properties, there approximately is a linear negative correlation of electron affinity with the LUMO energy of the β-turn or the SOMO energy of its electron adduct. Besides, such relaying properties also vary in the vibration evolution process, and the electron-binding modes may be tunable. As an important addition to the known static charge relaying properties occurring in various protein structural motifs, this work reports the dynamic electron-relaying characteristics of a β-turn oligopeptide with variable relaying properties governed by molecular vibrations which can be applied to different proteins in mediating long-range charge transfers. Clearly, this work reveals molecular vibration effects on the electron relaying properties of protein structural motifs and provides new insights into the dynamics of long-range charge transfers in proteins. © 2018 Wiley Periodicals, Inc.
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Affiliation(s)
- Xiufang Song
- School of Chemistry &Chemical Engineering, Institute of Theoretical Chemistry, Shandong University, Jinan 250100, People's Republic of China
| | - Fengying Zhang
- School of Chemistry &Chemical Engineering, Institute of Theoretical Chemistry, Shandong University, Jinan 250100, People's Republic of China
| | - Yuxiang Bu
- School of Chemistry &Chemical Engineering, Institute of Theoretical Chemistry, Shandong University, Jinan 250100, People's Republic of China
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99
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Recent advances in photoinduced catalysis for water splitting and environmental applications. J IND ENG CHEM 2019. [DOI: 10.1016/j.jiec.2019.01.004] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
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100
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Mamun AA, Toda MJ, Kozlowski PM. Can photolysis of the Co C bond in coenzyme B12-dependent enzymes be used to mimic the native reaction? JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY B-BIOLOGY 2019; 191:175-184. [DOI: 10.1016/j.jphotobiol.2018.12.018] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/16/2018] [Revised: 12/19/2018] [Accepted: 12/20/2018] [Indexed: 12/22/2022]
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