1
|
Sanfui S, Chakraborty P, Garribba E, Rath SP. Diheme cytochromes: Effect of mixed-axial ligation on the electronic structure and electrochemical properties with cobalt porphyrin dimer. J Inorg Biochem 2023; 240:112109. [PMID: 36592509 DOI: 10.1016/j.jinorgbio.2022.112109] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2022] [Revised: 12/11/2022] [Accepted: 12/15/2022] [Indexed: 12/24/2022]
Abstract
A series of six-coordinate diCo(III) porphyrin dimers, as synthetic analogues of diheme cytochromes, have been reported here having bis(imidazole), bis(pyridine) and mixed thiophenolate-pyridine/imidazole axial ligands. In the X-ray structures of bis(imidazole) and bis(pyridine) complexes, the axial ligands are in perpendicular orientation while they are parallelly oriented in their monomeric analog. The porphyrin rings are also highly ruffle-distorted in dimer but planar in monomer which reflect the effect of intramolecular interaction between two Co(porphyrin) units in dimers. In the X-ray structure of diCo(III) thiophenolate-pyridine mixed-ligated complex, the axial Co-S and Co-N(py) distances are 2.256(1) and 2.063(2) Å, respectively. The Co-N(py) distance of 2.063(2) Å is much longer than the distances of 1.961(3) and 1.972(3) Å observed in bis(pyridine) complex and the Co-S distance is larger than Co-N(py) in the mixed ligated complex which results in a displacement of Co by 0.15 Å towards the pyridine ligand from the mean porphyrin plane. Indeed, this is the first X-ray structure of a metalloporphyrin with mixed thiophenolate-pyridine axial ligands. The effect of mixed-axial ligation is demonstrated by a blue-shift of the Soret band in the UV-visible spectroscopy and also a positive shift of the Co(III)/Co(II) redox couple as compared to their bis(pyridine) analogue. The redox potentials are shifted to a large negative value just upon replacing the metal from iron to cobalt. The present investigation emphasizes the role of axial ligation, metal ions, and also the effect of heme-heme interaction in controlling the spectral and electrochemical properties.
Collapse
Affiliation(s)
- Sarnali Sanfui
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur 208016, India
| | - Paulami Chakraborty
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur 208016, India
| | - Eugenio Garribba
- Dipartimento di Medicina, Chirurgia e Farmacia, Università di Sassari, Viale San Pietro, I-07100 Sassari, Italy
| | - Sankar Prasad Rath
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur 208016, India.
| |
Collapse
|
2
|
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: 96] [Impact Index Per Article: 32.0] [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.
Collapse
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
| |
Collapse
|
3
|
Khan FST, Samanta D, Chandel D, Shah SJ, Rath SP. Heme-Heme Interactions in Diheme Cytochromes: Effect of Mixed-Axial Ligation on the Electronic Structure and Electrochemical Properties. Inorg Chem 2021; 60:12870-12882. [PMID: 34370470 DOI: 10.1021/acs.inorgchem.1c01215] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Diheme cytochromes, the simplest members in the multiheme family, play substantial biochemical roles in enzymatic catalysis as well as in electron transfer. A series of diiron(III) porphyrin dimers have been synthesized as active site analogues of diheme cytochromes. The complexes contain six-coordinated iron(III) having thiophenol and imidazole at the fifth and sixth coordination sites, respectively. The iron centers in the complexes have been found to be in a low-spin state, as confirmed through solid-state Mössbauer and electron paramagnetic resonance (EPR) spectroscopic investigations. Mössbauer quadrupole splitting of complexes having mixed ligands is substantially larger than that observed when both axial ligands are the same. Rhombic types of EPR spectra with narrow separation between gx, gy, and gz clearly distinguish heme thiolate coordination compared to bis(imidazole)-ligated low-spin heme centers. The redox potential in diheme cytochromes has been found to be tuned by interheme interactions along with the nature of axial ligands. The effect of mixed-axial ligation within the diiron(III) porphyrin dimers is demonstrated by a positive shift in the Fe(III)/Fe(II) redox couple upon thiophenolate coordination compared to their bis(imidazole) analogues. The pKa of the imidazole also decides the extent of the shift for the Fe(III)/Fe(II) couple, while the potential of the mixed-ligated diiron(III) porphyrin dimer is more positive compared to their monomeric analogue. A variation of around 1.1 V for the Fe(III)/Fe(II) redox potential in the diiron(III) porphyrin dimer can be achieved with the combined effect of axial ligation and a metal spin state, while such a large variation in the redox potential, compared to their monomeric analogues, is attributed to the heme-heme interactions observed in dihemes. Moreover, theoretical calculations also support the experimental shifts in the redox potential values.
Collapse
Affiliation(s)
| | - Deepannita Samanta
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur 208016, India
| | - Dolly Chandel
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur 208016, India
| | - Syed Jehanger Shah
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur 208016, India
| | - Sankar Prasad Rath
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur 208016, India
| |
Collapse
|
4
|
Benchoam D, Cuevasanta E, Julió Plana L, Capece L, Banerjee R, Alvarez B. Heme-Thiolate Perturbation in Cystathionine β-Synthase by Mercury Compounds. ACS OMEGA 2021; 6:2192-2205. [PMID: 33521459 PMCID: PMC7841933 DOI: 10.1021/acsomega.0c05475] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/09/2020] [Accepted: 12/22/2020] [Indexed: 05/11/2023]
Abstract
Cystathionine β-synthase (CBS) is an enzyme involved in sulfur metabolism that catalyzes the pyridoxal phosphate-dependent condensation of homocysteine with serine or cysteine to form cystathionine and water or hydrogen sulfide (H2S), respectively. CBS possesses a b-type heme coordinated by histidine and cysteine. Fe(III)-CBS is inert toward exogenous ligands, while Fe(II)-CBS is reactive. Both Fe(III)- and Fe(II)-CBS are sensitive to mercury compounds. In this study, we describe the kinetics of the reactions with mercuric chloride (HgCl2) and p-chloromercuribenzoic acid. These reactions were multiphasic and resulted in five-coordinate CBS lacking thiolate ligation, with six-coordinate species as intermediates. Computational QM/MM studies supported the feasibility of formation of species in which the thiolate is proximal to both the iron ion and the mercury compound. The reactions of Fe(II)-CBS were faster than those of Fe(III)-CBS. The observed rate constants of the first phase increased hyperbolically with concentration of the mercury compounds, with limiting values of 0.3-0.4 s-1 for Fe(III)-CBS and 40 ± 4 s-1 for Fe(II)-CBS. The data were interpreted in terms of alternative models of conformational selection or induced fit. Exposure of Fe(III)-CBS to HgCl2 led to heme release and activity loss. Our study reveals the complexity of the interactions between mercury compounds and CBS.
Collapse
Affiliation(s)
- Dayana Benchoam
- Laboratorio
de Enzimología, Instituto de Química Biológica,
Facultad de Ciencias, Universidad de la
República, Montevideo, 11400 Uruguay
- Centro
de Investigaciones Biomédicas (CEINBIO), Universidad de la República, Montevideo, 11800 Uruguay
| | - Ernesto Cuevasanta
- Laboratorio
de Enzimología, Instituto de Química Biológica,
Facultad de Ciencias, Universidad de la
República, Montevideo, 11400 Uruguay
- Centro
de Investigaciones Biomédicas (CEINBIO), Universidad de la República, Montevideo, 11800 Uruguay
- Unidad
de Bioquímica Analítica, Centro de Investigaciones Nucleares,
Facultad de Ciencias, Universidad de la
República, Montevideo, 11400 Uruguay
| | - Laia Julió Plana
- Departamento
de Química Inorgánica, Analítica y Química
Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires/Instituto de Química
Física de los Materiales, Medio Ambiente y Energía (INQUIMAE-CONICET), C1428EGA Buenos
Aires, Argentina
| | - Luciana Capece
- Departamento
de Química Inorgánica, Analítica y Química
Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires/Instituto de Química
Física de los Materiales, Medio Ambiente y Energía (INQUIMAE-CONICET), C1428EGA Buenos
Aires, Argentina
| | - Ruma Banerjee
- Department
of Biological Chemistry, University of Michigan
Medical School, Ann Arbor, Michigan 48109, United States
| | - Beatriz Alvarez
- Laboratorio
de Enzimología, Instituto de Química Biológica,
Facultad de Ciencias, Universidad de la
República, Montevideo, 11400 Uruguay
- Centro
de Investigaciones Biomédicas (CEINBIO), Universidad de la República, Montevideo, 11800 Uruguay
| |
Collapse
|
5
|
Hunt AP, Samanta S, Dent MR, Milbauer MW, Burstyn JN, Lehnert N. Model Complexes Elucidate the Role of the Proximal Hydrogen-Bonding Network in Cytochrome P450s. Inorg Chem 2020; 59:8034-8043. [DOI: 10.1021/acs.inorgchem.0c00245] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Andrew P. Hunt
- Department of Chemistry and Department of Biophysics, University of Michigan, Ann Arbor, Michigan 48109-1055, United States
| | - Subhra Samanta
- Department of Chemistry and Department of Biophysics, University of Michigan, Ann Arbor, Michigan 48109-1055, United States
| | - Matthew R. Dent
- Department of Chemistry, University of Wisconsin, Madison, Wisconsin 53706, United States
| | - Michael W. Milbauer
- Department of Chemistry, University of Wisconsin, Madison, Wisconsin 53706, United States
| | - Judith N. Burstyn
- Department of Chemistry, University of Wisconsin, Madison, Wisconsin 53706, United States
| | - Nicolai Lehnert
- Department of Chemistry and Department of Biophysics, University of Michigan, Ann Arbor, Michigan 48109-1055, United States
| |
Collapse
|