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Eady RR, Samar Hasnain S. New horizons in structure-function studies of copper nitrite reductase. Coord Chem Rev 2022. [DOI: 10.1016/j.ccr.2022.214463] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
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Lehnert N, Kim E, Dong HT, Harland JB, Hunt AP, Manickas EC, Oakley KM, Pham J, Reed GC, Alfaro VS. The Biologically Relevant Coordination Chemistry of Iron and Nitric Oxide: Electronic Structure and Reactivity. Chem Rev 2021; 121:14682-14905. [PMID: 34902255 DOI: 10.1021/acs.chemrev.1c00253] [Citation(s) in RCA: 101] [Impact Index Per Article: 33.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Nitric oxide (NO) is an important signaling molecule that is involved in a wide range of physiological and pathological events in biology. Metal coordination chemistry, especially with iron, is at the heart of many biological transformations involving NO. A series of heme proteins, nitric oxide synthases (NOS), soluble guanylate cyclase (sGC), and nitrophorins, are responsible for the biosynthesis, sensing, and transport of NO. Alternatively, NO can be generated from nitrite by heme- and copper-containing nitrite reductases (NIRs). The NO-bearing small molecules such as nitrosothiols and dinitrosyl iron complexes (DNICs) can serve as an alternative vehicle for NO storage and transport. Once NO is formed, the rich reaction chemistry of NO leads to a wide variety of biological activities including reduction of NO by heme or non-heme iron-containing NO reductases and protein post-translational modifications by DNICs. Much of our understanding of the reactivity of metal sites in biology with NO and the mechanisms of these transformations has come from the elucidation of the geometric and electronic structures and chemical reactivity of synthetic model systems, in synergy with biochemical and biophysical studies on the relevant proteins themselves. This review focuses on recent advancements from studies on proteins and model complexes that not only have improved our understanding of the biological roles of NO but also have provided foundations for biomedical research and for bio-inspired catalyst design in energy science.
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Affiliation(s)
- Nicolai Lehnert
- Department of Chemistry and Department of Biophysics, University of Michigan, Ann Arbor, Michigan 48109-1055, United States
| | - Eunsuk Kim
- Department of Chemistry, Brown University, Providence, Rhode Island 02912, United States
| | - Hai T Dong
- Department of Chemistry and Department of Biophysics, University of Michigan, Ann Arbor, Michigan 48109-1055, United States
| | - Jill B Harland
- Department of Chemistry and Department of Biophysics, University of Michigan, Ann Arbor, Michigan 48109-1055, United States
| | - Andrew P Hunt
- Department of Chemistry and Department of Biophysics, University of Michigan, Ann Arbor, Michigan 48109-1055, United States
| | - Elizabeth C Manickas
- Department of Chemistry and Department of Biophysics, University of Michigan, Ann Arbor, Michigan 48109-1055, United States
| | - Kady M Oakley
- Department of Chemistry, Brown University, Providence, Rhode Island 02912, United States
| | - John Pham
- Department of Chemistry, Brown University, Providence, Rhode Island 02912, United States
| | - Garrett C Reed
- Department of Chemistry and Department of Biophysics, University of Michigan, Ann Arbor, Michigan 48109-1055, United States
| | - Victor Sosa Alfaro
- Department of Chemistry and Department of Biophysics, University of Michigan, Ann Arbor, Michigan 48109-1055, United States
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Schröder GC, Meilleur F. Metalloprotein catalysis: structural and mechanistic insights into oxidoreductases from neutron protein crystallography. Acta Crystallogr D Struct Biol 2021; 77:1251-1269. [PMID: 34605429 PMCID: PMC8489226 DOI: 10.1107/s2059798321009025] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2021] [Accepted: 08/31/2021] [Indexed: 11/11/2022] Open
Abstract
Metalloproteins catalyze a range of reactions, with enhanced chemical functionality due to their metal cofactor. The reaction mechanisms of metalloproteins have been experimentally characterized by spectroscopy, macromolecular crystallography and cryo-electron microscopy. An important caveat in structural studies of metalloproteins remains the artefacts that can be introduced by radiation damage. Photoreduction, radiolysis and ionization deriving from the electromagnetic beam used to probe the structure complicate structural and mechanistic interpretation. Neutron protein diffraction remains the only structural probe that leaves protein samples devoid of radiation damage, even when data are collected at room temperature. Additionally, neutron protein crystallography provides information on the positions of light atoms such as hydrogen and deuterium, allowing the characterization of protonation states and hydrogen-bonding networks. Neutron protein crystallography has further been used in conjunction with experimental and computational techniques to gain insight into the structures and reaction mechanisms of several transition-state metal oxidoreductases with iron, copper and manganese cofactors. Here, the contribution of neutron protein crystallography towards elucidating the reaction mechanism of metalloproteins is reviewed.
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Affiliation(s)
- Gabriela C. Schröder
- Department of Molecular and Structural Biochemistry, North Carolina State University, Raleigh, NC 27695, USA
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
| | - Flora Meilleur
- Department of Molecular and Structural Biochemistry, North Carolina State University, Raleigh, NC 27695, USA
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA
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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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Beagan DM, Cabelof AC, Caulton KG. Back donation, intramolecular electron transfer and N-O bond scission targeting nitrogen oxyanion reduction: how can a metal complex assist? Dalton Trans 2021; 50:2149-2157. [PMID: 33491695 DOI: 10.1039/d0dt03430d] [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
A density functional theory exploration studies a range of ancillary coordinated ligands accompanying nitrogen oxyanions with the goal of promoting back donation towards varied nitrogen oxidation states. Evaluation of a suite of Ru and Rh metal complexes reveals minimum back donation to the κ1-nitrogen oxyanion ligand, even upon one-electron reduction. This reveals some surprising consequences of reduction, including redox activity at pyridine and nitrogen oxyanion dissociation. Bidentate nitrate was therefore considered, where ancillary ligands enforce geometries that maximize M-NOx orbital overlap. This strategy is successful and leads to full electron transfer in several cases to form a pyramidal radical NO32- ligand. The impact of ancillary ligand on degree of nitrate reduction is probed by comparing the powerful o-donor tris-carbene borate (TCB) to a milder donor, tris-pyrazolyl borate (Tp). This reveals that with the milder Tp donor, nitrate reduction is only seen upon addition of a Lewis base. Protonation of neutral and anionic (TCB)Ru(κ2-NO3) at both terminal and internal oxygens reveals exergonic N-O bond cleavage for the reduced species, with one electron coming from Ru, yielding a RuIII hydroxide product. Comparison of H+ to Na+ electrophile shows weaker progress towards N-O bond scission. Finally, calculations on (TCB)Fe(κ2-NO3) and [(TCB)Fe(κ2-NO3)]- show that electron transfer to nitrate is possible even with an earth abundant 3d metal.
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Affiliation(s)
- Daniel M Beagan
- Department of Chemistry, Indiana University, 800 E. Kirkwood Ave., Bloomington, IN 47401, USA.
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Qin X, Chen X. Remote Water-Mediated Proton Transfer Triggers Inter-Cu Electron Transfer: Nitrite Reduction Activation in Copper-Containing Nitrite Reductase. Chembiochem 2021; 22:1405-1414. [PMID: 33295048 DOI: 10.1002/cbic.202000644] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2020] [Revised: 12/07/2020] [Indexed: 11/05/2022]
Abstract
The copper-containing nitrite reductase (CuNiR) catalyzes the biological conversion of nitrite to nitric oxide; key long-range electron/proton transfers are involved in the catalysis. However, the details of the electron-/proton-transfer mechanism are still unknown. In particular, the driving force of the electron transfer from the type-1 copper (T1Cu) site to the type-2 copper (T2Cu) site is ambiguous. Here, we explored the two possible proton-transfer channels, the high-pH proton channel and the primary proton channel, by using two-layered ONIOM calculations. Our calculation results reveal that the driving force for electron transfer from T1Cu to T2Cu comes from a remote water-mediated triple-proton-coupled electron-transfer mechanism. In the high-pH proton channel, the water-mediated triple-proton transfer occurs from Glu113 to an intermediate water molecule, whereas in the primary channel, the transfer is from Lys128 to His260. Subsequently, the two channels employ another two or three distinct proton-transfer steps to deliver the proton to the nitrite substrate at the T2Cu site. These findings explain the detailed proton-/electron-transfer mechanisms of copper-containing nitrite reductase and could extend our understanding of the diverse proton-coupled electron-transfer mechanisms in complicated proteins.
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Affiliation(s)
- Xin Qin
- Chongqing Key Laboratory of Theoretical and Computational Chemistry, School of Chemistry and Chemical Engineering, Chongqing University, 55 University City South Road, Shapingba District, 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, 55 University City South Road, Shapingba District, 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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High-resolution neutron crystallography visualizes an OH-bound resting state of a copper-containing nitrite reductase. Proc Natl Acad Sci U S A 2020; 117:4071-4077. [PMID: 32041886 PMCID: PMC7049163 DOI: 10.1073/pnas.1918125117] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
X-ray crystallography often fails to determine the positions of hydrogen atoms, which play crucial roles in enzymatic reactions. Despite many X-ray crystallographic studies, the reaction mechanism of copper-containing nitrite reductases (CuNIRs), which reduce nitrite using two protons, has been controversial. The high-resolution neutron structure of a CuNIR reveals the protonation states of catalytic residues and key water molecules, thus providing insights into the catalytic mechanism. The catalytic Cu is shown to be coordinated by a hydroxide ion and not water. Furthermore, the hydrogen-deuterium exchange ratio suggests that intramolecular electron transfer is involved in a hydrogen-bond jump. These observations are consistent with previous computational chemistry; therefore, our study forms a bridge between the structural biology and quantum chemistry of CuNIRs. Copper-containing nitrite reductases (CuNIRs) transform nitrite to gaseous nitric oxide, which is a key process in the global nitrogen cycle. The catalytic mechanism has been extensively studied to ultimately achieve rational control of this important geobiochemical reaction. However, accumulated structural biology data show discrepancies with spectroscopic and computational studies; hence, the reaction mechanism is still controversial. In particular, the details of the proton transfer involved in it are largely unknown. This situation arises from the failure of determining positions of hydrogen atoms and protons, which play essential roles at the catalytic site of CuNIRs, even with atomic resolution X-ray crystallography. Here, we determined the 1.50 Å resolution neutron structure of a CuNIR from Geobacillus thermodenitrificans (trimer molecular mass of ∼106 kDa) in its resting state at low pH. Our neutron structure reveals the protonation states of catalytic residues (deprotonated aspartate and protonated histidine), thus providing insights into the catalytic mechanism. We found that a hydroxide ion can exist as a ligand to the catalytic Cu atom in the resting state even at a low pH. This OH-bound Cu site is unexpected from previously given X-ray structures but consistent with a reaction intermediate suggested by computational chemistry. Furthermore, the hydrogen-deuterium exchange ratio in our neutron structure suggests that the intramolecular electron transfer pathway has a hydrogen-bond jump, which is proposed by quantum chemistry. Our study can seamlessly link the structural biology to the computational chemistry of CuNIRs, boosting our understanding of the enzymes at the atomic and electronic levels.
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Opperman DJ, Murgida DH, Dalosto SD, Brondino CD, Ferroni FM. A three-domain copper-nitrite reductase with a unique sensing loop. IUCRJ 2019; 6:248-258. [PMID: 30867922 PMCID: PMC6400189 DOI: 10.1107/s2052252519000241] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/26/2018] [Accepted: 01/06/2019] [Indexed: 06/09/2023]
Abstract
Dissimilatory nitrite reductases are key enzymes in the denitrification pathway, reducing nitrite and leading to the production of gaseous products (NO, N2O and N2). The reaction is catalysed either by a Cu-containing nitrite reductase (NirK) or by a cytochrome cd 1 nitrite reductase (NirS), as the simultaneous presence of the two enzymes has never been detected in the same microorganism. The thermophilic bacterium Thermus scotoductus SA-01 is an exception to this rule, harbouring both genes within a denitrification cluster, which encodes for an atypical NirK. The crystal structure of TsNirK has been determined at 1.63 Å resolution. TsNirK is a homotrimer with subunits of 451 residues that contain three copper atoms each. The N-terminal region possesses a type 2 Cu (T2Cu) and a type 1 Cu (T1CuN) while the C-terminus contains an extra type 1 Cu (T1CuC) bound within a cupredoxin motif. T1CuN shows an unusual Cu atom coordination (His2-Cys-Gln) compared with T1Cu observed in NirKs reported so far (His2-Cys-Met). T1CuC is buried at ∼5 Å from the molecular surface and located ∼14.1 Å away from T1CuN; T1CuN and T2Cu are ∼12.6 Å apart. All these distances are compatible with an electron-transfer process T1CuC → T1CuN → T2Cu. T1CuN and T2Cu are connected by a typical Cys-His bridge and an unexpected sensing loop which harbours a SerCAT residue close to T2Cu, suggesting an alternative nitrite-reduction mechanism in these enzymes. Biophysicochemical and functional features of TsNirK are discussed on the basis of X-ray crystallography, electron paramagnetic resonance, resonance Raman and kinetic experiments.
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Affiliation(s)
- Diederik Johannes Opperman
- Department of Biotechnology, University of the Free State, 205 Nelson Mandela Drive, Bloemfontein, Free State 9300, South Africa
| | - Daniel Horacio Murgida
- Departamento de Química Inorgánica, Analítica y Química Física and INQUIMAE (CONICET-UBA), Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pab. 2 piso 1, Buenos Aires, Buenos Aires C1428EHA, Argentina
| | - Sergio Daniel Dalosto
- Instituto de Física del Litoral, CONICET-UNL, Güemes 3450, Santa Fe, Santa Fe S3000ZAA, Argentina
| | - Carlos Dante Brondino
- Departamento de Física, Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral (UNL), CONICET, Ciudad Universitaria, Paraje El Pozo, Santa Fe, Santa Fe S3000ZAA, Argentina
| | - Felix Martín Ferroni
- Departamento de Física, Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral (UNL), CONICET, Ciudad Universitaria, Paraje El Pozo, Santa Fe, Santa Fe S3000ZAA, Argentina
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