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Rajbongshi J, Das DK, Mazumdar S. Spectroscopic and electrochemical studies of the pH-Induced transition in the CuA centre from Thermus thermophilus. Inorganica Chim Acta 2022. [DOI: 10.1016/j.ica.2021.120749] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Melin F, Hellwig P. Redox Properties of the Membrane Proteins from the Respiratory Chain. Chem Rev 2020; 120:10244-10297. [DOI: 10.1021/acs.chemrev.0c00249] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- Frederic Melin
- Chimie de la Matière Complexe UMR 7140, Laboratoire de Bioelectrochimie et Spectroscopie, CNRS-Université de Strasbourg, 1 rue Blaise Pascal, 67070 Strasbourg, France
| | - Petra Hellwig
- Chimie de la Matière Complexe UMR 7140, Laboratoire de Bioelectrochimie et Spectroscopie, CNRS-Université de Strasbourg, 1 rue Blaise Pascal, 67070 Strasbourg, France
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Carreira C, Dos Santos MMC, Pauleta SR, Moura I. Proton-coupled electron transfer mechanisms of the copper centres of nitrous oxide reductase from Marinobacter hydrocarbonoclasticus - An electrochemical study. Bioelectrochemistry 2020; 133:107483. [PMID: 32120320 DOI: 10.1016/j.bioelechem.2020.107483] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2019] [Revised: 02/13/2020] [Accepted: 02/13/2020] [Indexed: 11/16/2022]
Abstract
Reduction of N2O to N2 is catalysed by nitrous oxide reductase in the last step of the denitrification pathway. This multicopper enzyme has an electron transferring centre, CuA, and a tetranuclear copper-sulfide catalytic centre, "CuZ", which exists as CuZ*(4Cu1S) or CuZ(4Cu2S). The redox behaviour of these metal centres in Marinobacter hydrocarbonoclasticus nitrous oxide reductase was investigated by potentiometry and for the first time by direct electrochemistry. The reduction potential of CuA and CuZ(4Cu2S) was estimated by potentiometry to be +275 ± 5 mV and +65 ± 5 mV vs SHE, respectively, at pH 7.6. A proton-coupled electron transfer mechanism governs CuZ(4Cu2S) reduction potential, due to the protonation/deprotonation of Lys397 with a pKox of 6.0 ± 0.1 and a pKred of 9.2 ± 0.1. The reduction potential of CuA, in enzyme samples with CuZ*(4Cu1S), is controlled by protonation of the coordinating histidine residues in a two-proton coupled electron transfer process. In the cyclic voltammograms, two redox pairs were identified corresponding to CuA and CuZ(4Cu2S), with no additional signals being detected that could be attributed to CuZ*(4Cu1S). However, an enhanced cathodic signal for the activated enzyme was observed under turnover conditions, which is explained by the binding of nitrous oxide to CuZ0(4Cu1S), an intermediate species in the catalytic cycle.
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Affiliation(s)
- Cíntia Carreira
- Microbial Stress Lab, UCIBIO, REQUIMTE, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Campus da Caparica, 2829-516 Caparica, Portugal; Biological Chemistry Lab, LAQV, REQUIMTE, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Campus da Caparica, 2829-516 Caparica, Portugal
| | - Margarida M C Dos Santos
- Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal
| | - Sofia R Pauleta
- Microbial Stress Lab, UCIBIO, REQUIMTE, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Campus da Caparica, 2829-516 Caparica, Portugal. http://docentes.fct.unl.pt/srp/
| | - Isabel Moura
- Biological Chemistry Lab, LAQV, REQUIMTE, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Campus da Caparica, 2829-516 Caparica, Portugal.
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Chakraborty S, Polen MJ, Chacón KN, Wilson TD, Yu Y, Reed J, Nilges MJ, Blackburn NJ, Lu Y. Binuclear Cu(A) Formation in Biosynthetic Models of Cu(A) in Azurin Proceeds via a Novel Cu(Cys)2His Mononuclear Copper Intermediate. Biochemistry 2016; 54:6071-81. [PMID: 26352296 DOI: 10.1021/acs.biochem.5b00659] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Cu(A) is a binuclear electron transfer (ET) center found in cytochrome c oxidases (CcOs), nitrous oxide reductases (N₂ORs), and nitric oxide reductase (NOR). In these proteins, the Cu(A) centers facilitate efficient ET (kET > 10⁴s⁻¹) under low thermodynamic driving forces (10-90 mV). While the structure and functional properties of Cu(A) are well understood, a detailed mechanism of the incorporation of copper into the protein and the identity of the intermediates formed during the Cu(A) maturation process are still lacking. Previous studies of the Cu(A) assembly mechanism in vitro using a biosynthetic model Cu(A) center in azurin (Cu(A)Az) identified a novel intermediate X (Ix) during reconstitution of the binuclear site. However, because of the instability of Ix and the coexistence of other Cu centers, such as Cu(A)' and type 1 copper centers, the identity of this intermediate could not be established. Here, we report the mechanism of Cu(A) assembly using variants of Glu114XCuAAz (X = Gly, Ala, Leu, or Gln), the backbone carbonyl of which acts as a ligand to the Cu(A) site, with a major focus on characterization of the novel intermediate Ix. We show that Cu(A) assembly in these variants proceeds through several types of Cu centers, such as mononuclear red type 2 Cu, the novel intermediate Ix, and blue type 1 Cu. Our results show that the backbone flexibility of the Glu114 residue is an important factor in determining the rates of T2Cu → Ix formation, suggesting that Cu(A) formation is facilitated by swinging of the ligand loop, which internalizes the T2Cu capture complex to the protein interior. The kinetic data further suggest that the nature of the Glu114 side chain influences the time scales on which these intermediates are formed, the wavelengths of the absorption peaks, and how cleanly one intermediate is converted to another. Through careful understanding of these mechanisms and optimization of the conditions, we have obtained Ix in ∼80-85% population in these variants, which allowed us to employ ultraviolet-visible, electron paramagnetic resonance, and extended X-ray absorption fine structure spectroscopic techniques to identify the Ix as a mononuclear Cu(Cys)(2)(His) complex. Because some of the intermediates have been proposed to be involved in the assembly of native Cu(A), these results shed light on the structural features of the important intermediates and mechanism of Cu(A) formation.
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Affiliation(s)
- Saumen Chakraborty
- Department of Chemistry, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States
| | - Michael J Polen
- Department of Chemistry, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States
| | - Kelly N Chacón
- Institute of Environmental Health, Oregon Health & Sciences University , Portland, Oregon 97239, United States
| | - Tiffany D Wilson
- Department of Chemistry, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States
| | - Yang Yu
- Department of Chemistry, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States
| | - Julian Reed
- Department of Chemistry, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States
| | - Mark J Nilges
- Department of Chemistry, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States
| | - Ninian J Blackburn
- Institute of Environmental Health, Oregon Health & Sciences University , Portland, Oregon 97239, United States
| | - Yi Lu
- Department of Chemistry, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States
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Ghosh MK, Basak P, Mazumdar S. Mechanism of copper incorporation in subunit II of cytochrome C oxidase from Thermus thermophilus: identification of intermediate species. Biochemistry 2013; 52:4620-35. [PMID: 23745508 DOI: 10.1021/bi400101g] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Detailed spectroscopic and kinetic studies of incorporation of copper ion in the wild type (WT) and the D111AA (AA = K, N, or E) mutants of the metal ion binding site of the soluble fragment of subunit II of cytochrome c oxidase from Thermus thermophilus (TtCuA) showed the formation of at least two distinct intermediates. The global analyses of the multiwavelength kinetic results suggested a four-step reaction scheme involving two distinct intermediates in the pathway of incorporation of copper ions into the apoprotein forming the purple dinuclear CuA. An early intermediate similar to the red copper binding proteins was detected in the WT as well as in all the mutants. The second intermediate was a green copper species in the case of WT TtCuA. Mutation of Asp111, however, formed a second intermediate that is distinctly different from that formed in the case of the WT protein, suggesting that mutants follow pathways of copper ion incorporation different from that in the WT protein. The electrostatic interaction between Asp111 and the coordinating His114 possibly plays a subtle role in the mechanism of incorporation of metal ion into the protein. The overall Kd for WT TtCuA was found to be ~8 nM, which changed with mutation of the Asp111 residue. The activation and thermodynamic parameters were also determined from the temperature- and pH-dependent multiwavelength kinetics, and the results are discussed to unravel the role of Asp111 in the mechanism of formation of the dinuclear CuA center in cytochrome c oxidase.
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Affiliation(s)
- Manas Kumar Ghosh
- Department of Chemical Sciences, Tata Institute of Fundamental Research , Colaba, Mumbai 400005, India
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