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Lu YL, Wu K, Huang YH, Li WC, Cao ZM, Yan XH, Zhang XD, Liu CH, Ruan J, Xu HS, Pan M, Su CY. Stereochemical Control of Redox Co II/Co III-Cages with Switchable Cotton Effects Based on Labile-Static States. J Am Chem Soc 2024; 146:20414-20424. [PMID: 38982611 DOI: 10.1021/jacs.4c06102] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/11/2024]
Abstract
The structural dynamics of artificial assemblies, in aspects such as molecular recognition and structural transformation, provide us with a blueprint to achieve bioinspired applications. Here, we describe the assembly of redox-switchable chiral metal-organic cages Λ8/Δ8-[Pd6(CoIIL3)8]28+ and Λ8/Δ8-[Pd6(CoIIIL3)8]36+. These isomeric cages demonstrate an on-off chirality logic gate controlled by their chemical and stereostructural dynamics tunable through redox transitions between the labile CoII-state and static CoIII-state with a distinct Cotton effect. The transition between different states is enabled by a reversible redox process and chiral recognition originating in the tris-chelate Co-centers. All cages in two states are thoroughly characterized by NMR, ESI-MS, CV, CD, and X-ray crystallographic analysis, which clarify their redox-switching behaviors upon chemical reduction/oxidation. The stereochemical lability of the CoII-center endows the Λ8/Δ8-CoII-cages with efficient chiral-induction by enantiomeric guests, leading to enantiomeric isomerization to switch between Λ8/Δ8-CoII-cages, which can be stabilized by oxidation to their chemically inert forms of Λ8/Δ8-CoIII-cages. Kinetic studies reveal that the isomerization rate of the Δ8-CoIII-cage is at least an order of magnitude slower than that of the Δ8-CoII-cage even at an elevated temperature, while its activation energy is 16 kcal mol-1 higher than that of the CoII-cage.
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Affiliation(s)
- Yu-Lin Lu
- MOE Key Laboratory of Bioinorganic and Synthetic Chemistry, GBRCE for Functional Molecular Engineering, LIFM, IGCME, School of Chemistry, Sun Yat-Sen University, Guangzhou 510275, China
| | - Kai Wu
- MOE Key Laboratory of Bioinorganic and Synthetic Chemistry, GBRCE for Functional Molecular Engineering, LIFM, IGCME, School of Chemistry, Sun Yat-Sen University, Guangzhou 510275, China
| | - Yin-Hui Huang
- MOE Key Laboratory of Bioinorganic and Synthetic Chemistry, GBRCE for Functional Molecular Engineering, LIFM, IGCME, School of Chemistry, Sun Yat-Sen University, Guangzhou 510275, China
| | - Wei-Chun Li
- MOE Key Laboratory of Bioinorganic and Synthetic Chemistry, GBRCE for Functional Molecular Engineering, LIFM, IGCME, School of Chemistry, Sun Yat-Sen University, Guangzhou 510275, China
| | - Zhong-Min Cao
- MOE Key Laboratory of Bioinorganic and Synthetic Chemistry, GBRCE for Functional Molecular Engineering, LIFM, IGCME, School of Chemistry, Sun Yat-Sen University, Guangzhou 510275, China
| | - Xiang-Han Yan
- MOE Key Laboratory of Bioinorganic and Synthetic Chemistry, GBRCE for Functional Molecular Engineering, LIFM, IGCME, School of Chemistry, Sun Yat-Sen University, Guangzhou 510275, China
| | - Xiao-Dong Zhang
- MOE Key Laboratory of Bioinorganic and Synthetic Chemistry, GBRCE for Functional Molecular Engineering, LIFM, IGCME, School of Chemistry, Sun Yat-Sen University, Guangzhou 510275, China
| | - Chen-Hui Liu
- MOE Key Laboratory of Bioinorganic and Synthetic Chemistry, GBRCE for Functional Molecular Engineering, LIFM, IGCME, School of Chemistry, Sun Yat-Sen University, Guangzhou 510275, China
| | - Jia Ruan
- MOE Key Laboratory of Bioinorganic and Synthetic Chemistry, GBRCE for Functional Molecular Engineering, LIFM, IGCME, School of Chemistry, Sun Yat-Sen University, Guangzhou 510275, China
| | - Hai-Sen Xu
- MOE Key Laboratory of Bioinorganic and Synthetic Chemistry, GBRCE for Functional Molecular Engineering, LIFM, IGCME, School of Chemistry, Sun Yat-Sen University, Guangzhou 510275, China
| | - Mei Pan
- MOE Key Laboratory of Bioinorganic and Synthetic Chemistry, GBRCE for Functional Molecular Engineering, LIFM, IGCME, School of Chemistry, Sun Yat-Sen University, Guangzhou 510275, China
| | - Cheng-Yong Su
- MOE Key Laboratory of Bioinorganic and Synthetic Chemistry, GBRCE for Functional Molecular Engineering, LIFM, IGCME, School of Chemistry, Sun Yat-Sen University, Guangzhou 510275, China
- State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, Shanghai 200032, China
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2
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Stuut Balsam S, Zhong F, Pence N, Levintov L, Andhare D, Hammond JH, Ragusa MJ, Vashisth H, Hogan DA, Pletneva EV. Conserved C-Terminal Tail Is Responsible for Membrane Localization and Function of Pseudomonas aeruginosa Hemerythrin. Biochemistry 2024; 63:1795-1807. [PMID: 38951132 DOI: 10.1021/acs.biochem.4c00174] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/03/2024]
Abstract
Many bacteria have hemerythrin (Hr) proteins that bind O2, including Pseudomonas aeruginosa, in which microoxia-induced Hr (Mhr) provide fitness advantages under microoxic conditions. Mhr has a 23 amino-acid extension at its C-terminus relative to a well-characterized Hr from Methylococcus capsulatus, and similar extensions are also found in Hrs from other bacteria. The last 11 amino acids of this extended, C-terminal tail are highly conserved in gammaproteobacteria and predicted to form a helix with positively charged and hydrophobic faces. In cellular fractionation assays, wild-type (WT) Mhr was found in both membrane and cytosolic fractions, while a MhrW143* variant lacking the last 11 residues was largely in the cytosol and did not complement Mhr function in competition assays. MhrL112Y, a variant that has a much longer-lived O2-bound form, was fully functional and had a similar localization pattern to that of WT Mhr. Both MhrW143* and MhrL112Y had secondary structures, stabilities, and O2-binding kinetics similar to those of WT Mhr. Fluorescence studies revealed that the C-terminal tail, and particularly the fragment corresponding to its last 11 residues, was sufficient and necessary for association with lipid vesicles. Molecular dynamics simulations and subsequent cellular analysis of Mhr variants have demonstrated that conserved, positively charged residues in the tail are important for Mhr interactions with negatively charged membranes and the contribution of this protein to competitive fitness. Together, these data suggest that peripheral interactions of Mhr with membranes are guided by the C-terminal tail and are independent of O2-binding.
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Affiliation(s)
- Stacie Stuut Balsam
- Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire 03755, United States
| | - Fangfang Zhong
- Department of Chemistry, Dartmouth College, Hanover, New Hampshire 03755, United States
| | - Natasha Pence
- Department of Chemistry, Dartmouth College, Hanover, New Hampshire 03755, United States
| | - Lev Levintov
- Department of Chemical Engineering and Bioengineering, University of New Hampshire, Durham, New Hampshire 03824, United States
| | - Devika Andhare
- Department of Chemistry, Dartmouth College, Hanover, New Hampshire 03755, United States
| | - John H Hammond
- Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire 03755, United States
| | - Michael J Ragusa
- Department of Chemistry, Dartmouth College, Hanover, New Hampshire 03755, United States
| | - Harish Vashisth
- Department of Chemical Engineering and Bioengineering, University of New Hampshire, Durham, New Hampshire 03824, United States
- Department of Chemistry, University of New Hampshire, Durham, New Hampshire 03824, United States
- Integrated Applied Mathematics Program, University of New Hampshire, Durham, New Hampshire 03824, United States
- Molecular and Cellular Biotechnology Program, University of New Hampshire, Durham, New Hampshire 03824, United States
| | - Deborah A Hogan
- Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire 03755, United States
| | - Ekaterina V Pletneva
- Department of Chemistry, Dartmouth College, Hanover, New Hampshire 03755, United States
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3
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Sharma V, Joo JU, Mottafegh A, Kim DP. Continuous and autonomous-flow separation of laccase enzyme utilizing functionalized aqueous two-phase system with computer vision control. BIORESOURCE TECHNOLOGY 2024; 403:130888. [PMID: 38788804 DOI: 10.1016/j.biortech.2024.130888] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/11/2024] [Revised: 05/14/2024] [Accepted: 05/21/2024] [Indexed: 05/26/2024]
Abstract
Downstream processing of biomolecules, particularly therapeutic proteins and enzymes, presents a formidable challenge due to intricate unit operations and high costs. This study introduces a novel cysteine (cys) functionalized aqueous two-phase system (ATPS) utilizing polyethylene glycol (PEG) and potassium phosphate, referred as PEG-K3PO4/cys, for selective extraction of laccase from complex protein mixtures. A 3D-baffle micro-mixer and phase separator was meticulously designed and equipped with computer vision controller, to enable precise mixing and continuous phase separation under automated-flow. Microfluidic-assisted ATPS exhibits substantial increase in partition coefficient (Kflow = 16.3) and extraction efficiency (EEflow = 88 %) for laccase compared to conventional batch process. Integrated and continuous-flow process efficiently partitioned laccase, even in low concentrations and complex crude extracts. Circular dichroism spectra of laccase confirm structural stability of enzyme throughout the purification process. Eventually, continuous-flow microfluidic bioseparation is highly useful for seamless downstream processing of target biopharmaceuticals in integrated and autonomous manner.
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Affiliation(s)
- Vikas Sharma
- Center for Intelligent Microprocess of Pharmaceutical Synthesis, Department of Chemical Engineering, Pohang University of Science and Technology (POSTECH), Pohang 37673, Republic of Korea
| | - Jeong-Un Joo
- Center for Intelligent Microprocess of Pharmaceutical Synthesis, Department of Chemical Engineering, Pohang University of Science and Technology (POSTECH), Pohang 37673, Republic of Korea
| | - Amirreza Mottafegh
- Center for Intelligent Microprocess of Pharmaceutical Synthesis, Department of Chemical Engineering, Pohang University of Science and Technology (POSTECH), Pohang 37673, Republic of Korea
| | - Dong-Pyo Kim
- Center for Intelligent Microprocess of Pharmaceutical Synthesis, Department of Chemical Engineering, Pohang University of Science and Technology (POSTECH), Pohang 37673, Republic of Korea.
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4
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Al-Sadeq DW, Thanassoulas A, Theodoridou M, Nasrallah GK, Nomikos M. Pathogenic Homocystinuria-Associated T236N Mutation Dramatically Alters the Biochemical Properties of Cystathionine Beta-Synthase Protein. Biomedicines 2024; 12:929. [PMID: 38790892 PMCID: PMC11118236 DOI: 10.3390/biomedicines12050929] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2024] [Revised: 04/03/2024] [Accepted: 04/09/2024] [Indexed: 05/26/2024] Open
Abstract
BACKGROUND Cystathione beta-synthase (CBS) T236N is a novel mutation associated with pyridoxine non-responsiveness, which presents a significant difficulty in the medical treatment of homocystinuria. Reported severe phenotypes in homocystinuria patients highlight the urgent requirement to comprehend the molecular mechanisms underlying mutation pathogenicity for the advancement of the disease. METHODOLOGY In this study, we used a multidisciplinary approach to investigate the molecular properties of bacterially expressed and purified recombinant CBST236N protein, which we directly compared to those of the wild-type (CBSWT) protein. RESULTS Our data revealed a profound impact of the p.T236N mutation on CBS enzymatic activity, with a dramatic reduction of ~96% compared to the CBSWT protein. Circular dichroism (CD) experiments indicated that the p.T236N mutation did not significantly alter the secondary structure of the protein. However, CD spectra unveiled distinct differences in the thermal stability of CBSWT and CBST236N mutant protein species. In addition, chemical denaturation experiments further highlighted that the CBSWT protein exhibited greater thermodynamic stability than the CBST236N mutant, suggesting a destabilizing effect of this mutation. CONCLUSIONS Our findings provide an explanation of the pathogenicity of the p.T236N mutation, shedding light on its role in severe homocystinuria phenotypes. This study contributes to a deeper understanding of CBS deficiency and may improve the development of targeted therapeutic strategies for affected individuals.
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Affiliation(s)
- Duaa W. Al-Sadeq
- Biomedical Research Center, Qatar University, Doha P.O. Box 2713, Qatar; (D.W.A.-S.); (G.K.N.)
- College of Medicine, QU Health, Qatar University, Doha P.O. Box 2713, Qatar;
| | | | - Maria Theodoridou
- Biomedical Research Center, Qatar University, Doha P.O. Box 2713, Qatar; (D.W.A.-S.); (G.K.N.)
| | - Gheyath K. Nasrallah
- Biomedical Research Center, Qatar University, Doha P.O. Box 2713, Qatar; (D.W.A.-S.); (G.K.N.)
- Department of Biomedical Science, College of Health Sciences, QU Health, Qatar University, Doha P.O. Box 2713, Qatar
| | - Michail Nomikos
- College of Medicine, QU Health, Qatar University, Doha P.O. Box 2713, Qatar;
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5
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Zhong F, Albert T, Moënne-Loccoz P, Pletneva EV. Influence of the Interdomain Interface on Structural and Redox Properties of Multiheme Proteins. Inorg Chem 2022; 61:20949-20963. [PMID: 36493379 PMCID: PMC11034829 DOI: 10.1021/acs.inorgchem.2c03427] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Multiheme proteins are important in energy conversion and biogeochemical cycles of nitrogen and sulfur. A diheme cytochrome c4 (c4) was used as a model to elucidate roles of the interdomain interface on properties of iron centers in its hemes A and B. Isolated monoheme domains c4-A and c4-B, together with the full-length diheme c4 and its Met-to-His ligand variants, were characterized by a variety of spectroscopic and stability measurements. In both isolated domains, the heme iron is Met/His-ligated at pH 5.0, as in the full-length c4, but becomes His/His-ligated in c4-B at higher pH. Intradomain contacts in c4-A are minimally affected by the separation of c4-A and c4-B domains, and isolated c4-A is folded. In contrast, the isolated c4-B is partially unfolded, and the interface with c4-A guides folding of this domain. The c4-A and c4-B domains have the propensity to interact even without the polypeptide linker. Thermodynamic cycles have revealed properties of monomeric folded isolated domains, suggesting that ferrous (FeII), but not ferric (FeIII) c4-A and c4-B, is stabilized by the interface. This study illustrates the effects of the interface on tuning structural and redox properties of multiheme proteins and enriches our understanding of redox-dependent complexation.
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Affiliation(s)
- Fangfang Zhong
- Department of Chemistry, Dartmouth College, Hanover, NH 03755, United States
| | - Therese Albert
- Department of Chemical Physiology and Biochemistry, School of Medicine, Oregon Health & Science University, Portland, OR 97239, United States
| | - Pierre Moënne-Loccoz
- Department of Chemical Physiology and Biochemistry, School of Medicine, Oregon Health & Science University, Portland, OR 97239, United States
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6
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Jenner LP, Crack JC, Kurth JM, Soldánová Z, Brandt L, Sokol KP, Reisner E, Bradley JM, Dahl C, Cheesman MR, Butt JN. Reaction of Thiosulfate Dehydrogenase with a Substrate Mimic Induces Dissociation of the Cysteine Heme Ligand Giving Insights into the Mechanism of Oxidative Catalysis. J Am Chem Soc 2022; 144:18296-18304. [PMID: 36173876 PMCID: PMC9562282 DOI: 10.1021/jacs.2c06062] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
![]()
Thiosulfate dehydrogenases are bacterial cytochromes
that contribute
to the oxidation of inorganic sulfur. The active sites of these enzymes
contain low-spin c-type heme with Cys–/His axial ligation. However, the reduction potentials of these hemes
are several hundred mV more negative than that of the thiosulfate/tetrathionate
couple (Em, +198 mV), making it difficult
to rationalize the thiosulfate oxidizing capability. Here, we describe
the reaction of Campylobacter jejuni thiosulfate dehydrogenase (TsdA) with sulfite, an analogue of thiosulfate.
The reaction leads to stoichiometric conversion of the active site
Cys to cysteinyl sulfonate (Cα-CH2-S-SO3–) such that the protein exists in a form
closely resembling a proposed intermediate in the pathway for thiosulfate
oxidation that carries a cysteinyl thiosulfate (Cα-CH2-S-SSO3–). The active
site heme in the stable sulfonated protein displays an Em approximately 200 mV more positive than the Cys–/His-ligated state. This can explain the thiosulfate
oxidizing activity of the enzyme and allows us to propose a catalytic
mechanism for thiosulfate oxidation. Substrate-driven release of the
Cys heme ligand allows that side chain to provide the site of substrate
binding and redox transformation; the neighboring heme then simply
provides a site for electron relay to an appropriate partner. This
chemistry is distinct from that displayed by the Cys-ligated hemes
found in gas-sensing hemoproteins and in enzymes such as the cytochromes
P450. Thus, a further class of thiolate-ligated hemes is proposed,
as exemplified by the TsdA centers that have evolved to catalyze the
controlled redox transformations of inorganic oxo anions of sulfur.
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Affiliation(s)
- Leon P Jenner
- Centre for Molecular and Structural Biochemistry, School of Chemistry and School of Biological Sciences, University of East Anglia, Norwich Research Park, NorwichNR4 7TJ, United Kingdom
| | - Jason C Crack
- Centre for Molecular and Structural Biochemistry, School of Chemistry and School of Biological Sciences, University of East Anglia, Norwich Research Park, NorwichNR4 7TJ, United Kingdom
| | - Julia M Kurth
- Institut für Mikrobiologie & Biotechnologie, Friedrich Wilhelms Universität Bonn, D-53115Bonn, Germany
| | - Zuzana Soldánová
- Centre for Molecular and Structural Biochemistry, School of Chemistry and School of Biological Sciences, University of East Anglia, Norwich Research Park, NorwichNR4 7TJ, United Kingdom
| | - Linda Brandt
- Institut für Mikrobiologie & Biotechnologie, Friedrich Wilhelms Universität Bonn, D-53115Bonn, Germany
| | - Katarzyna P Sokol
- Yusuf Hamied Department of Chemistry, University of Cambridge, Lensfield Road, CambridgeCB2 1EW, United Kingdom
| | - Erwin Reisner
- Yusuf Hamied Department of Chemistry, University of Cambridge, Lensfield Road, CambridgeCB2 1EW, United Kingdom
| | - Justin M Bradley
- Centre for Molecular and Structural Biochemistry, School of Chemistry and School of Biological Sciences, University of East Anglia, Norwich Research Park, NorwichNR4 7TJ, United Kingdom
| | - Christiane Dahl
- Institut für Mikrobiologie & Biotechnologie, Friedrich Wilhelms Universität Bonn, D-53115Bonn, Germany
| | - Myles R Cheesman
- Centre for Molecular and Structural Biochemistry, School of Chemistry and School of Biological Sciences, University of East Anglia, Norwich Research Park, NorwichNR4 7TJ, United Kingdom
| | - Julea N Butt
- Centre for Molecular and Structural Biochemistry, School of Chemistry and School of Biological Sciences, University of East Anglia, Norwich Research Park, NorwichNR4 7TJ, United Kingdom
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7
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Skeens E, Gadzuk-Shea M, Shah D, Bhandari V, Schweppe DK, Berlow RB, Lisi GP. Redox-dependent structure and dynamics of macrophage migration inhibitory factor reveal sites of latent allostery. Structure 2022; 30:840-850.e6. [PMID: 35381187 DOI: 10.1016/j.str.2022.03.007] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2021] [Revised: 01/20/2022] [Accepted: 03/09/2022] [Indexed: 01/01/2023]
Abstract
Macrophage migration inhibitory factor (MIF) is a multifunctional immunoregulatory protein that is a key player in the innate immune response. Given its overexpression at sites of inflammation and in diseases marked by increasingly oxidative environments, a comprehensive understanding of how cellular redox conditions impact the structure and function of MIF is necessary. We used NMR spectroscopy and mass spectrometry to investigate biophysical signatures of MIF under varied solution redox conditions. Our results indicate that the MIF structure is modified and becomes increasingly dynamic in an oxidative environment, which may be a means to alter the MIF conformation and functional response in a redox-dependent manner. We identified latent allosteric sites within MIF through mutational analysis of redox-sensitive residues, revealing that a loss of redox-responsive residues attenuates CD74 receptor activation. Leveraging sites of redox sensitivity as targets for structure-based drug design therefore reveals an avenue to modulate MIF function in its "disease state."
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Affiliation(s)
- Erin Skeens
- Department of Molecular Biology, Cell Biology, & Biochemistry, Brown University, Providence, RI 02903, USA
| | - Meagan Gadzuk-Shea
- Department of Genome Sciences, University of Washington, Seattle, WA 98195, USA
| | - Dilip Shah
- Section of Neonatology, Department of Pediatrics, Cooper University Hospital, Camden, NJ 08103, USA
| | - Vineet Bhandari
- Section of Neonatology, Department of Pediatrics, Cooper University Hospital, Camden, NJ 08103, USA
| | - Devin K Schweppe
- Department of Genome Sciences, University of Washington, Seattle, WA 98195, USA
| | - Rebecca B Berlow
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, CA 92037, USA; Department of Biochemistry and Biophysics and Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
| | - George P Lisi
- Department of Molecular Biology, Cell Biology, & Biochemistry, Brown University, Providence, RI 02903, USA.
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8
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Zhong F, Alden SL, Hughes RP, Pletneva EV. Comparing Properties of Common Bioinorganic Ligands with Switchable Variants of Cytochrome c. Inorg Chem 2021; 61:1207-1227. [PMID: 34699724 DOI: 10.1021/acs.inorgchem.1c02322] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Ligand substitution at the metal center is common in catalysis and signal transduction of metalloproteins. Understanding the effects of particular ligands, as well as the polypeptide surrounding, is critical for uncovering mechanisms of these biological processes and exploiting them in the design of bioinspired catalysts and molecular devices. A series of switchable K79G/M80X/F82C (X = Met, His, or Lys) variants of cytochrome (cyt) c was employed to directly compare the stability of differently ligated proteins and activation barriers for Met, His, and Lys replacement at the ferric heme iron. Studies of these variants and their nonswitchable counterparts K79G/M80X have revealed stability trends Met < Lys < His and Lys < His < Met for the protein FeIII-X and FeII-X species, respectively. The differences in the hydrogen-bonding interactions in folded proteins and in solvation of unbound X in the unfolded proteins explain these trends. Calculations of free energy of ligand dissociation in small heme model complexes reveal that the ease of the FeIII-X bond breaking increases in the series amine < imidazole < thioether, mirroring trends in hardness of these ligands. Experimental rate constants for X dissociation in differently ligated cyt c variants are consistent with this sequence, but the differences between Met and His dissociation rates are attenuated because the former process is limited by the heme crevice opening. Analyses of activation parameters and comparisons to those for the Lys-to-Met ligand switch in the alkaline transition suggest that ligand dissociation is entropically driven in all the variants and accompanied by Lys protonation at neutral pH. The described thiolate redox-linked switches have offered a wealth of new information about interactions of different protein-derived ligands with the heme iron in cyt c model proteins, and we anticipate that the strategy of employing these switches could benefit studies of other redox metalloproteins and model complexes.
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Affiliation(s)
- Fangfang Zhong
- Department of Chemistry, Dartmouth College, Hanover, New Hampshire 03755, United States
| | - Stephanie L Alden
- Department of Chemistry, Dartmouth College, Hanover, New Hampshire 03755, United States
| | - Russell P Hughes
- Department of Chemistry, Dartmouth College, Hanover, New Hampshire 03755, United States
| | - Ekaterina V Pletneva
- Department of Chemistry, Dartmouth College, Hanover, New Hampshire 03755, United States
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9
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Shin I, Davis I, Nieves-Merced K, Wang Y, McHardy S, Liu A. A novel catalytic heme cofactor in SfmD with a single thioether bond and a bis-His ligand set revealed by a de novo crystal structural and spectroscopic study. Chem Sci 2021; 12:3984-3998. [PMID: 34163669 PMCID: PMC8179489 DOI: 10.1039/d0sc06369j] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2020] [Accepted: 01/21/2021] [Indexed: 12/13/2022] Open
Abstract
SfmD is a heme-dependent enzyme in the biosynthetic pathway of saframycin A. Here, we present a 1.78 Å resolution de novo crystal structure of SfmD, which unveils a novel heme cofactor attached to the protein with an unusual Hx n HxxxC motif (n ∼ 38). This heme cofactor is unique in two respects. It contains a single thioether bond in a cysteine-vinyl link with Cys317, and the ferric heme has two axial protein ligands, i.e., His274 and His313. We demonstrated that SfmD heme is catalytically active and can utilize dioxygen and ascorbate for a single-oxygen insertion into 3-methyl-l-tyrosine. Catalytic assays using ascorbate derivatives revealed the functional groups of ascorbate essential to its function as a cosubstrate. Abolishing the thioether linkage through mutation of Cys317 resulted in catalytically inactive SfmD variants. EPR and optical data revealed that the heme center undergoes a substantial conformational change with one axial histidine ligand dissociating from the iron ion in response to substrate 3-methyl-l-tyrosine binding or chemical reduction by a reducing agent, such as the cosubstrate ascorbate. The labile axial ligand was identified as His274 through redox-linked structural determinations. Together, identifying an unusual heme cofactor with a previously unknown heme-binding motif for a monooxygenase activity and the structural similarity of SfmD to the members of the heme-based tryptophan dioxygenase superfamily will broaden understanding of heme chemistry.
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Affiliation(s)
- Inchul Shin
- Department of Chemistry, The University of Texas at San Antonio One UTSA Circle Texas 78249 USA
| | - Ian Davis
- Department of Chemistry, The University of Texas at San Antonio One UTSA Circle Texas 78249 USA
| | - Karinel Nieves-Merced
- Department of Chemistry, The University of Texas at San Antonio One UTSA Circle Texas 78249 USA
- Center for Innovative Drug Discovery, The University of Texas at San Antonio One UTSA Circle Texas 78249 USA
| | - Yifan Wang
- Department of Chemistry, The University of Texas at San Antonio One UTSA Circle Texas 78249 USA
| | - Stanton McHardy
- Department of Chemistry, The University of Texas at San Antonio One UTSA Circle Texas 78249 USA
- Center for Innovative Drug Discovery, The University of Texas at San Antonio One UTSA Circle Texas 78249 USA
| | - Aimin Liu
- Department of Chemistry, The University of Texas at San Antonio One UTSA Circle Texas 78249 USA
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10
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A comparison of steroid and lipid binding cytochrome P450s from Mycobacterium marinum and Mycobacterium tuberculosis. J Inorg Biochem 2020; 209:111116. [PMID: 32473484 DOI: 10.1016/j.jinorgbio.2020.111116] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2019] [Revised: 05/11/2020] [Accepted: 05/14/2020] [Indexed: 11/22/2022]
Abstract
The steroid lipid binding cytochrome P450 (CYP) enzymes of Mycobacterium tuberculosis are essential for organism survival through metabolism of cholesterol and its derivatives. The counterparts to these enzymes from Mycobacterium marinum were studied to determine the degree of functional conservation between them. Spectroscopic analyses of substrate and inhibitor binding for the four M. marinum enzymes CYP125A6, CYP125A7, CYP142A3 and CYP124A1 were performed and compared to the equivalent enzymes of M. tuberculosis. The sequence of CYP125A7 from M. marinum was more similar to CYP125A1 from M. tuberculosis than CYP125A6 but both showed differences in the resting heme spin state and in the binding modes and affinities of certain azole inhibitors. CYP125A7 did not show a significant Type II inhibitor-like shift with any of the azoles tested. CYP142A3 bound a similar range of steroids and inhibitors to CYP142A1. However, there were some differences in the extent of the Type I shifts to the high-spin form with steroids and a higher affinity for the azole inhibitors compared to CYP142A1. The two CYP124 enzymes had similar substrate binding properties. M. marinum CYP124 was characterised by X-ray crystallography and displayed strong conservation of active site residues, except near the region where the carboxylate terminus of the phytanic acid substrate would be bound. As these enzymes in M. tuberculosis have been identified as candidates for inhibition the data here demonstrates that alternative strategies for inhibitor design may be required to target CYP family members from distinct pathogenic Mycobacterium species or other bacteria.
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11
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Zuccarello L, Berthomieu C, Boussac A, Brubach JB, Díaz-Moreno I, Díaz Quintana AJ, Hienerwadel R. Protonation of the Cysteine Axial Ligand Investigated in His/Cys c-Type Cytochrome by UV-Vis and Mid- and Far-IR Spectroscopy. J Phys Chem Lett 2020; 11:4198-4205. [PMID: 32364390 DOI: 10.1021/acs.jpclett.0c01016] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
His/Cys coordination was recently found in several c-type cytochromes, which could act as sensors, in electron transport or in regulation. Toward a better understanding of Cys function and reactivity in these cytochromes, we compare cytochrome c6 (c6wt) from the cyanobacterium Nostoc PCC 7120 with its Met58Cys mutant. We probe the axial ligands and heme properties by combining visible and mid- to far-FTIR difference spectroscopies. Cys58 determines the strong negative redox potential and pH dependence of M58C (EmM58C = -375 mV, versus Emc6wt = +339 mV). Mid-IR (notably Cys ν(SH), His ν(C5N1), heme δ(CmH)) and far-IR (ν(Fe(II)-His), ν(His-Fe(III)-Cys)) markers of the heme and ligands show that Cys58 remains a strong thiolate ligand of reduced Met58Cys at alkaline pH, while it is protonated at pH 7.5, is stabilized by a strong hydrogen bonding interaction, and weakly interacts with Fe(II). These data provide a benchmark for further analysis of c-type cytochromes with natural His/Cys coordination.
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Affiliation(s)
- Lidia Zuccarello
- CEA, CNRS, Aix Marseille Univ., BIAM, Interactions Protéine Métal UMR 7265, 13108 Saint Paul-Lez-Durance, France
- Aix Marseille Univ., CEA, CNRS, BIAM, Luminy Genetics and Biophysic of Plants, UMR 7265, 13288 Marseille Cedex, France
| | - Catherine Berthomieu
- CEA, CNRS, Aix Marseille Univ., BIAM, Interactions Protéine Métal UMR 7265, 13108 Saint Paul-Lez-Durance, France
| | - Alain Boussac
- I2BC, UMR CNRS 9198, CEA Saclay, 91191 Gif-sur-Yvette, France
| | - Jean-Blaise Brubach
- Synchrotron SOLEIL, AILES Beamline, L'Orme des Merisier, Saint-Aubin, BP 48, F-91192 Gif-sur-Yvette Cedex, France
| | - Irene Díaz-Moreno
- Instituto de Investigaciones Químicas (IIQ), Centro de Investigaciones Científicas Isla de la Cartuja (cicCartuja), Universidad de Sevilla - Consejo Superior de Investigaciones Científicas (CSIC), Avda. Américo Vespucio 49, Sevilla 41092, Spain
| | - Antonio J Díaz Quintana
- Instituto de Investigaciones Químicas (IIQ), Centro de Investigaciones Científicas Isla de la Cartuja (cicCartuja), Universidad de Sevilla - Consejo Superior de Investigaciones Científicas (CSIC), Avda. Américo Vespucio 49, Sevilla 41092, Spain
| | - Rainer Hienerwadel
- Aix Marseille Univ., CEA, CNRS, BIAM, Luminy Genetics and Biophysic of Plants, UMR 7265, 13288 Marseille Cedex, France
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12
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Deng Y, Weaver ML, Hoke KR, Pletneva EV. A Heme Propionate Staples the Structure of Cytochrome c for Methionine Ligation to the Heme Iron. Inorg Chem 2019; 58:14085-14106. [PMID: 31589413 DOI: 10.1021/acs.inorgchem.9b02111] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Ligand-switch reactions at the heme iron are common in biological systems, but their mechanisms and the features of the polypeptide fold that support dual ligation are not well understood. In cytochrome c (cyt c), two low-stability loops (Ω-loop C and Ω-loop D) are connected by the heme propionate HP6. At alkaline pH, the native Met80 ligand from Ω-loop D switches to a Lys residue from the same loop. Deprotonation of an as yet unknown group triggers the alkaline transition. We have created the two cyt c variants T49V/K79G and T78V/K79G with altered connections of these two loops to HP6. Electronic absorption, NMR, and EPR studies demonstrate that at pH 7.4 ferric forms of these variants are Lys-ligated, whereas ferrous forms maintain the native Met80 ligation. Measurements of protein stability, cyclic voltammetry, pH-jump and gated electron-transfer kinetics have revealed that these Thr to Val substitutions greatly affect the alkaline transition in both ferric and ferrous proteins. The substitutions modify the stability of the Met-ligated species and reduction potentials of the heme iron. The kinetics of ligand-switch processes are also altered, and analyses of these effects implicate redox-dependent differences in metal-ligand interactions and the role of the protein dynamics, including cross-talk between the two Ω-loops. With the two destabilized variants, it is possible to map energy levels for the Met- and Lys-ligated species in both ferric and ferrous proteins and assess the role of the protein scaffold in redox-dependent preferences for these two ligands. The estimated shift in the heme iron reduction potential upon deprotonation of the "trigger" group is consistent with those associated with deprotonation of an HP, suggesting that HP6, on its own or as a part of a hydrogen-bonded cluster, is a likely "trigger" for the Met to Lys ligand switch.
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Affiliation(s)
- Yunling Deng
- Department of Chemistry , Dartmouth College , Hanover , New Hampshire 03755 , United States
| | - Madeline L Weaver
- Department of Chemistry and Biochemistry , Berry College , Mount Berry , Georgia 30149 , United States
| | - Kevin R Hoke
- Department of Chemistry and Biochemistry , Berry College , Mount Berry , Georgia 30149 , United States
| | - Ekaterina V Pletneva
- Department of Chemistry , Dartmouth College , Hanover , New Hampshire 03755 , United States
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13
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Ferousi C, Lindhoud S, Baymann F, Hester ER, Reimann J, Kartal B. Discovery of a functional, contracted heme-binding motif within a multiheme cytochrome. J Biol Chem 2019; 294:16953-16965. [PMID: 31582564 DOI: 10.1074/jbc.ra119.010568] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2019] [Revised: 10/02/2019] [Indexed: 11/06/2022] Open
Abstract
Anaerobic ammonium-oxidizing (anammox) bacteria convert nitrite and ammonium via nitric oxide (NO) and hydrazine into dinitrogen gas by using a diverse array of proteins, including numerous c-type cytochromes. Many new catalytic and spectroscopic properties of c-type cytochromes have been unraveled by studies on the biochemical pathways underlying the anammox process. The unique anammox intermediate hydrazine is produced by a multiheme cytochrome c protein, hydrazine synthase, through the comproportionation of ammonium and NO and the input of three electrons. It is unclear how these electrons are delivered to hydrazine synthase. Here, we report the discovery of a functional tetraheme c-type cytochrome from the anammox bacterium Kuenenia stuttgartiensis with a naturally-occurring contracted Cys-Lys-Cys-His (CKCH) heme-binding motif, which is encoded in the hydrazine synthase gene cluster. The purified tetraheme protein (named KsTH) exchanged electrons with hydrazine synthase. Complementary spectroscopic techniques revealed that this protein harbors four low-spin hexa-coordinated hemes with His/Lys (heme 1), His/Cys (heme 2), and two His/His ligations (hemes 3 and 4). A genomic database search revealed that c-type cytochromes with a contracted CXCH heme-binding motif are present throughout the bacterial and archaeal domains in the tree of life, suggesting that this heme recognition site may be employed by many different groups of microorganisms.
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Affiliation(s)
- Christina Ferousi
- Department of Microbiology, IWWR, Radboud University, 6525 AJ Nijmegen, The Netherlands
| | - Simon Lindhoud
- Department of Microbiology, IWWR, Radboud University, 6525 AJ Nijmegen, The Netherlands
| | - Frauke Baymann
- Laboratoire de Bioénergétique et Ingénierie des Protéines UMR 7281 CNRS/AMU, Marseille Cedex 09, France
| | - Eric R Hester
- Department of Microbiology, IWWR, Radboud University, 6525 AJ Nijmegen, The Netherlands
| | - Joachim Reimann
- Department of Microbiology, IWWR, Radboud University, 6525 AJ Nijmegen, The Netherlands
| | - Boran Kartal
- Microbial Physiology Group, Max Planck Institute for Marine Microbiology, D-28359 Bremen, Germany
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14
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Verstraete MM, Morales LD, Kobylarz MJ, Loutet SA, Laakso HA, Pinter TB, Stillman MJ, Heinrichs DE, Murphy MEP. The heme-sensitive regulator SbnI has a bifunctional role in staphyloferrin B production by Staphylococcus aureus. J Biol Chem 2019; 294:11622-11636. [PMID: 31197035 DOI: 10.1074/jbc.ra119.007757] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2019] [Revised: 06/12/2019] [Indexed: 01/30/2023] Open
Abstract
Staphylococcus aureus infection relies on iron acquisition from its host. S. aureus takes up iron through heme uptake by the iron-responsive surface determinant (Isd) system and by the production of iron-scavenging siderophores. Staphyloferrin B (SB) is a siderophore produced by the 9-gene sbn gene cluster for SB biosynthesis and efflux. Recently, the ninth gene product, SbnI, was determined to be a free l-serine kinase that produces O-phospho-l-serine (OPS), a substrate for SB biosynthesis. Previous studies have also characterized SbnI as a DNA-binding regulatory protein that senses heme to control sbn gene expression for SB synthesis. Here, we present crystal structures at 1.9-2.1 Å resolution of a SbnI homolog from Staphylococcus pseudintermedius (SpSbnI) in both apo form and in complex with ADP, a product of the kinase reaction; the latter confirmed the active-site location. The structures revealed that SpSbnI forms a dimer through C-terminal domain swapping and a dimer of dimers through intermolecular disulfide formation. Heme binding had only a modest effect on SbnI enzymatic activity, suggesting that its two functions are independent and structurally distinct. We identified a heme-binding site and observed catalytic heme transfer between a heme-degrading protein of the Isd system, IsdI, and SbnI. These findings support the notion that SbnI has a bifunctional role contributing precursor OPS to SB synthesis and directly sensing heme to control expression of the sbn locus. We propose that heme transfer from IsdI to SbnI enables S. aureus to control iron source preference according to the sources available in the environment.
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Affiliation(s)
- Meghan M Verstraete
- Department of Microbiology and Immunology, University of British Columbia, Vancouver, BC V6T 1Z3, Canada
| | - L Daniela Morales
- Department of Microbiology and Immunology, University of British Columbia, Vancouver, BC V6T 1Z3, Canada
| | - Marek J Kobylarz
- Department of Microbiology and Immunology, University of British Columbia, Vancouver, BC V6T 1Z3, Canada
| | - Slade A Loutet
- Department of Microbiology and Immunology, University of British Columbia, Vancouver, BC V6T 1Z3, Canada
| | - Holly A Laakso
- Department of Microbiology and Immunology, University of Western Ontario, London, Ontario N6A 5C1, Canada
| | - Tyler B Pinter
- Department of Chemistry, University of Western Ontario, London, Ontario N6A 5C1, Canada
| | - Martin J Stillman
- Department of Chemistry, University of Western Ontario, London, Ontario N6A 5C1, Canada
| | - David E Heinrichs
- Department of Microbiology and Immunology, University of Western Ontario, London, Ontario N6A 5C1, Canada
| | - Michael E P Murphy
- Department of Microbiology and Immunology, University of British Columbia, Vancouver, BC V6T 1Z3, Canada
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15
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Versantvoort W, Pol A, Daumann LJ, Larrabee JA, Strayer AH, Jetten MS, van Niftrik L, Reimann J, Op den Camp HJ. Characterization of a novel cytochrome c as the electron acceptor of XoxF-MDH in the thermoacidophilic methanotroph Methylacidiphilum fumariolicum SolV. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2019; 1867:595-603. [DOI: 10.1016/j.bbapap.2019.04.001] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/15/2019] [Revised: 03/28/2019] [Accepted: 04/02/2019] [Indexed: 11/29/2022]
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16
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Mondal A, Das M, Mazumdar S. Substitution of iron with cobalt in the prosthetic group of bacterial cytochrome P450: Effects on the stability and structure of the protein. Inorganica Chim Acta 2019. [DOI: 10.1016/j.ica.2018.12.043] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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17
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Shimizu T, Lengalova A, Martínek V, Martínková M. Heme: emergent roles of heme in signal transduction, functional regulation and as catalytic centres. Chem Soc Rev 2019; 48:5624-5657. [DOI: 10.1039/c9cs00268e] [Citation(s) in RCA: 81] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Molecular mechanisms of unprecedented functions of exchangeable/labile heme and heme proteins including transcription, DNA binding, protein kinase activity, K+ channel functions, cis–trans isomerization, N–N bond formation, and other functions are described.
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Affiliation(s)
- Toru Shimizu
- Department of Biochemistry
- Faculty of Science
- Charles University
- Prague 2
- Czech Republic
| | - Alzbeta Lengalova
- Department of Biochemistry
- Faculty of Science
- Charles University
- Prague 2
- Czech Republic
| | - Václav Martínek
- Department of Biochemistry
- Faculty of Science
- Charles University
- Prague 2
- Czech Republic
| | - Markéta Martínková
- Department of Biochemistry
- Faculty of Science
- Charles University
- Prague 2
- Czech Republic
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18
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Deng Y, Zhong F, Alden SL, Hoke KR, Pletneva EV. The K79G Mutation Reshapes the Heme Crevice and Alters Redox Properties of Cytochrome c. Biochemistry 2018; 57:5827-5840. [PMID: 30142276 DOI: 10.1021/acs.biochem.8b00650] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The two roles of cytochrome c (cyt c), in oxidative phosphorylation and apoptosis, critically depend on redox properties of its heme iron center. The K79G mutant has served as a parent protein for a series of mutants of yeast iso-1 cyt c. The mutation preserves the Met80 coordination to the heme iron, as found in WT* (K72A/C102S), and many spectroscopic properties of K79G and WT* are indistinguishable. The K79G mutation does not alter the global stability, fold, rate of Met80 dissociation, or thermodynamics of the alkaline transition (p Ka) of the protein. However, the reduction potential of the heme iron decreases; further, the p KH of the trigger group and the rate of the Met-to-Lys ligand exchange associated with the alkaline transition decrease, suggesting changes in the environment of the heme. The rates of electron self-exchange and bimolecular electron transfer (ET) with positively charged inorganic complexes increase, as does the intrinsic peroxidase activity. Analysis of the reaction rates suggests that there is increased accessibility of the heme edge in K79G and supports the importance of the Lys79 site for bimolecular ET reactions of cyt c, including those with some of its native redox partners. Structural modeling rationalizes the observed effects to arise from changes in the volume of the heme pocket and solvent accessibility of the heme group. Kinetic and structural analyses of WT* characterize the properties of the heme crevice of this commonly employed reference variant. This study highlights the important role of Lys79 for defining functional redox properties of cyt c.
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Affiliation(s)
- Yunling Deng
- Department of Chemistry , Dartmouth College , Hanover , New Hampshire 03755 , United States
| | - Fangfang Zhong
- Department of Chemistry , Dartmouth College , Hanover , New Hampshire 03755 , United States
| | - Stephanie L Alden
- Department of Chemistry , Dartmouth College , Hanover , New Hampshire 03755 , United States
| | - Kevin R Hoke
- Department of Chemistry and Biochemistry , Berry College , Mount Berry , Georgia 30149 , United States
| | - Ekaterina V Pletneva
- Department of Chemistry , Dartmouth College , Hanover , New Hampshire 03755 , United States
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19
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Boubeta FM, Bieza SA, Bringas M, Estrin DA, Boechi L, Bari SE. Mechanism of Sulfide Binding by Ferric Hemeproteins. Inorg Chem 2018; 57:7591-7600. [DOI: 10.1021/acs.inorgchem.8b00478] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Affiliation(s)
- Fernando M. Boubeta
- Instituto de Química Física de los Materiales, Medio Ambiente y Energía (INQUIMAE), CONICET and Universidad de Buenos Aires, Buenos Aires 1053, Argentina
| | - Silvina A. Bieza
- Instituto de Química Física de los Materiales, Medio Ambiente y Energía (INQUIMAE), CONICET and Universidad de Buenos Aires, Buenos Aires 1053, Argentina
| | - Mauro Bringas
- Instituto de Química Física de los Materiales, Medio Ambiente y Energía (INQUIMAE), CONICET and Universidad de Buenos Aires, Buenos Aires 1053, Argentina
| | - Darío A. Estrin
- Instituto de Química Física de los Materiales, Medio Ambiente y Energía (INQUIMAE), CONICET and Universidad de Buenos Aires, Buenos Aires 1053, Argentina
| | | | - Sara E. Bari
- Instituto de Química Física de los Materiales, Medio Ambiente y Energía (INQUIMAE), CONICET and Universidad de Buenos Aires, Buenos Aires 1053, Argentina
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20
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Abstract
Met80, one of the heme iron ligands in cytochrome c (cyt c), is readily oxidized to Met sulfoxide (Met-SO) by several biologically relevant oxidants. The modification has been suggested to affect both the electron-transfer (ET) and apoptotic functions of this metalloprotein. The coordination of the heme iron in Met-oxidized cyt c (Met-SO cyt c) is critical for both of these functions but has remained poorly defined. We present electronic absorption, NMR, and EPR spectroscopic investigations as well as kinetic studies and mutational analyses to identify the heme iron ligands in yeast iso-1 Met-SO cyt c. Similar to the alkaline form of native cyt c, Lys73 and Lys79 ligate to the ferric heme iron in the Met80-oxidized protein, but this coordination takes place at much lower pH. The ferrous heme iron is ligated by Met-SO, implying the redox-linked ligand switch in the modified protein. Binding studies with the model peptide microperoxidase-8 provide a rationale for alterations in ligation and for the role of the polypeptide packing in native and Met-SO cyt c. Imidazole binding experiments have revealed that Lys dissociation from the ferric heme in K73A/K79G/M80K (M80K#) and Met-SO is more than 3 orders of magnitude slower than the opening of the heme pocket that limits Met80 replacement in native cyt c. The Lys-to-Met-SO ligand substitution gates ET of ferric Met-SO cyt c with Co(terpy)22+. Owing to the slow Lys dissociation step, ET reaction is slow but possible, which is not the case for nonswitchable M80A and M80K#. Acidic conditions cause Lys replacement by a water ligand in Met-SO cyt c (p Ka = 6.3 ± 0.1), increasing the intrinsic peroxidase activity of the protein. This pH-driven ligand switch may be a mechanism to boost peroxidase function of cyt c specifically in apoptotic cells.
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Affiliation(s)
- Fangfang Zhong
- Department of Chemistry, Dartmouth College, Hanover, NH 03755
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21
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Tanabe J, Nakano K, Hirata R, Himeno T, Ishimatsu R, Imato T, Okabe H, Matsuda N. Totally synthetic microperoxidase-11. ROYAL SOCIETY OPEN SCIENCE 2018; 5:172311. [PMID: 29892416 PMCID: PMC5990835 DOI: 10.1098/rsos.172311] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/09/2018] [Accepted: 04/18/2018] [Indexed: 06/08/2023]
Abstract
A totally synthetic microperoxidase-11 (MP-11) is reported. Accordingly, the undecapeptide (VQKCAQCHTVE) was synthesized by solid-phase peptide synthesis followed by the thiol-ene click reaction with haemin for reconstitution. High-speed atomic force microscopy measurement conducted in water confirmed the protein reconstitution by visualizing the morphological differences as animated molecular images. The synthetic MP-11 showed a considerable magnitude of catalytic activity (27%) against the natural MP-11 in the oxidation of 3,3',5,5'-tetramethylbenzidine by hydrogen peroxide, whereas it showed very low (2.7%) activity of a synthetic variant with a point mutation (VQKCAQC M TVE, H8M). Slab waveguide spectroscopic measurements revealed that the ferrous/ferric redox reaction occurred by the direct electron transfer with specific spectral changes. Indeed, if hydrogen peroxide existed in the solution phase, the peroxidase-modified electrode showed catalytic current-voltage behaviour regardless of whether it was prepared using natural MP-11 or the synthetic MP-11. If a substrate recycling reaction was assumed, computer simulation well reproduced the experimental curves to give a global set of electrocatalytic reaction parameters. In any of the experiments, the synthetic MP-11 and natural MP-11 gave almost identical results. Our approach will be a convenient means of preparing MP-11, as well as its mutants, that does not rely on nature.
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Affiliation(s)
- Junichi Tanabe
- Department of Applied Chemistry, Faculty of Engineering, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan
| | - Koji Nakano
- Department of Applied Chemistry, Faculty of Engineering, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan
| | - Ryutaro Hirata
- Department of Applied Chemistry, Faculty of Engineering, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan
| | - Toshiki Himeno
- Department of Applied Chemistry, Faculty of Engineering, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan
| | - Ryoichi Ishimatsu
- Department of Applied Chemistry, Faculty of Engineering, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan
| | - Toshihiko Imato
- Department of Applied Chemistry, Faculty of Engineering, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan
| | - Hirotaka Okabe
- National Institute of Advanced Industrial Science and Technology, Kyushu, 807-1 Shuku-machi, Tosu, Saga 841-0052, Japan
| | - Naoki Matsuda
- National Institute of Advanced Industrial Science and Technology, Kyushu, 807-1 Shuku-machi, Tosu, Saga 841-0052, Japan
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22
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Abstract
Aerobic organisms have evolved to activate oxygen from the atmosphere, which allows them to catalyze the oxidation of different kinds of substrates. This activation of oxygen is achieved by a metal center (usually iron or copper) buried within a metalloprotein. In the case of iron-containing heme enzymes, the activation of oxygen is achieved by formation of transient iron-oxo (ferryl) intermediates; these intermediates are called Compound I and Compound II. The Compound I and II intermediates were first discovered in the 1930s in horseradish peroxidase, and it is now known that these same species are used across the family of heme enzymes, which include all of the peroxidases, the heme catalases, the P450s, cytochrome c oxidase, and NO synthase. Many years have passed since the first observations, but establishing the chemical nature of these transient ferryl species remains a fundamental question that is relevant to the reactivity, and therefore the usefulness, of these species in biology. This Account summarizes experiments that were conceived and conducted at Leicester and presents our ideas on the chemical nature, stability, and reactivity of these ferryl heme species. We begin by briefly summarizing the early milestones in the field, from the 1940s and 1950s. We present comparisons between the nature and reactivity of the ferryl species in horseradish peroxidase, cytochrome c peroxidase, and ascorbate peroxidase; and we consider different modes of electron delivery to ferryl heme, from different substrates in different peroxidases. We address the question of whether the ferryl heme is best formulated as an (unprotonated) FeIV═O or as a (protonated) FeIV-OH species. A range of spectroscopic approaches (EXAFS, resonance Raman, Mossbauer, and EPR) have been used over many decades to examine this question, and in the last ten years, X-ray crystallography has also been employed. We describe how information from all of these studies has blended together to create an overall picture, and how the recent application of neutron crystallography has directly identified protonation states and has helped to clarify the precise nature of the ferryl heme in cytochrome c peroxidase and ascorbate peroxidase. We draw comparisons between the Compound I and Compound II species that we have observed in peroxidases with those found in other heme systems, notably the P450s, highlighting possible commonality across these heme ferryl systems. The identification of proton locations from neutron structures of these ferryl species opens the door for understanding the proton translocations that need to occur during O-O bond cleavage.
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Affiliation(s)
- Peter C. E. Moody
- Department
of Molecular and Cell Biology and Leicester Institute of Structural
and Chemical Biology, University of Leicester, Lancaster Road, Leicester LE1 9HN, England
| | - Emma L. Raven
- Department
of Chemistry and Leicester Institute of Structural and Chemical Biology, University of Leicester, University Road, Leicester LE1 7RH, U.K
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23
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Prieto T, Santana V, Britto AMM, Araujo-Chaves JC, R Nascimento O, L Nantes-Cardoso I. Structure and Catalysis of Fe(III) and Cu(II) Microperoxidase-11 Interacting with the Positively Charged Interfaces of Lipids. Molecules 2017; 22:molecules22081212. [PMID: 28933729 PMCID: PMC6151982 DOI: 10.3390/molecules22081212] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2017] [Revised: 06/20/2017] [Accepted: 07/14/2017] [Indexed: 11/24/2022] Open
Abstract
Numerous applications have been described for microperoxidases (MPs) such as in photoreceptors, sensing, drugs, and hydrogen evolution. The last application was obtained by replacing Fe(III), the native central metal, by cobalt ion and inspired part of the present study. Here, the Fe(III) of MP-11 was replaced by Cu(II) that is also a stable redox state in aerated medium, and the structure and activity of both MPs were modulated by the interaction with the positively charged interfaces of lipids. Comparative spectroscopic characterization of Fe(III) and Cu(II)MP-11 in the studied media demonstrated the presence of high and low spin species with axial distortion. The association of the Fe(III)MP-11 with CTAB and Cu(II)MP-11 with DODAB affected the colloidal stability of the surfactants that was recovered by heating. This result is consistent with hydrophobic interactions of MPs with DODAB vesicles and CTAB micelles. The hydrophobic interactions decreased the heme accessibility to substrates and the Fe(III) MP-11catalytic efficiency. Cu(II)MP-11 challenged by peroxides exhibited a cyclic Cu(II)/Cu(I) interconversion mechanism that is suggestive of a mimetic Cu/ZnSOD (superoxide dismutase) activity against peroxides. Hydrogen peroxide-activated Cu(II)MP-11 converted Amplex Red® to dihydroresofurin. This study opens more possibilities for technological applications of MPs.
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Affiliation(s)
- Tatiana Prieto
- Universidade Federal do ABC, Santo André 09210-170, SP, Brazil.
| | - Vinicius Santana
- Universidade de São Paulo, Instituto de Física de São Carlos, São Carlos 13400-970, SP, Brazil.
| | | | | | - Otaciro R Nascimento
- Universidade de São Paulo, Instituto de Física de São Carlos, São Carlos 13400-970, SP, Brazil.
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24
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Yan JA, Chen YS, Chang YH, Tsai CY, Lyu CL, Luo CG, Lee GH, Hsu HF. Redox Interconversion of Non-Oxido Vanadium Complexes Accompanied by Acid–Base Chemistry of Thiol and Thiolate. Inorg Chem 2017; 56:9055-9063. [DOI: 10.1021/acs.inorgchem.7b01040] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Jyun-An Yan
- Department of Chemistry, National Cheng Kung University, Tainan 701, Taiwan
| | - Yu-Sen Chen
- Department of Chemistry, National Cheng Kung University, Tainan 701, Taiwan
| | - Ya-Ho Chang
- Department of Chemistry, National Cheng Kung University, Tainan 701, Taiwan
| | - Cheng-Yun Tsai
- Department of Chemistry, National Cheng Kung University, Tainan 701, Taiwan
| | - Chiao-Ling Lyu
- Department of Chemistry, National Cheng Kung University, Tainan 701, Taiwan
| | - Chun-Gang Luo
- Department of Chemistry, National Cheng Kung University, Tainan 701, Taiwan
| | - Gene-Hsiang Lee
- Department of Chemistry, National Taiwan University, Taipei 106, Taiwan
| | - Hua-Fen Hsu
- Department of Chemistry, National Cheng Kung University, Tainan 701, Taiwan
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25
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Gu J, Shin DW, Pletneva EV. Remote Perturbations in Tertiary Contacts Trigger Ligation of Lysine to the Heme Iron in Cytochrome c. Biochemistry 2017; 56:2950-2966. [PMID: 28474881 DOI: 10.1021/acs.biochem.6b01187] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Perturbations in protein structure define the mechanism of allosteric regulation and biological information transfer. In cytochrome c (cyt c), ligation of Met80 to the heme iron is critical for the protein's electron-transfer (ET) function in oxidative phosphorylation and for suppressing its peroxidase activity in apoptosis. The hard base Lys is a better match for the hard ferric iron than the soft base Met is, suggesting the key role of the protein scaffold in favoring Met ligation. To probe the role of the protein structure in the maintenance of Met ligation, mutations T49V and Y67R/M80A were designed to disrupt hydrogen bonding and packing of the heme coordination loop, respectively. Electronic absorption, nuclear magnetic resonance, and electron paramagnetic resonance spectra reveal that ferric forms of both variants are Lys-ligated at neutral pH. A minor change in the tertiary contacts in T49V, away from the heme coordination loop, appears to be sufficient to execute a change in ligation, suggesting a cross-talk between the different regions of the protein structure and a possibility of built-in conformational switches in cyt c. Analyses of thermodynamic stability, kinetics of Lys binding and dissociation, and the pH-dependent changes in ligation provide a detailed characterization of the Lys coordination in these variants and relate these properties to the extent of structural perturbations. The findings emphasize the importance of the hydrogen-bonding network in controlling ligation of the native Met80 to the heme iron.
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Affiliation(s)
- Jie Gu
- Department of Chemistry, Dartmouth College , Hanover, New Hampshire 03755, United States
| | - Dong-Woo Shin
- Department of Chemistry, Dartmouth College , Hanover, New Hampshire 03755, United States
| | - Ekaterina V Pletneva
- Department of Chemistry, Dartmouth College , Hanover, New Hampshire 03755, United States
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26
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Motomura T, Suga M, Hienerwadel R, Nakagawa A, Lai TL, Nitschke W, Kuma T, Sugiura M, Boussac A, Shen JR. Crystal structure and redox properties of a novel cyanobacterial heme protein with a His/Cys heme axial ligation and a Per-Arnt-Sim (PAS)-like domain. J Biol Chem 2017; 292:9599-9612. [PMID: 28428249 DOI: 10.1074/jbc.m116.746263] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2016] [Revised: 04/17/2017] [Indexed: 01/05/2023] Open
Abstract
Photosystem II catalyzes light-induced water oxidation leading to the generation of dioxygen indispensable for sustaining aerobic life on Earth. The Photosystem II reaction center is composed of D1 and D2 proteins encoded by psbA and psbD genes, respectively. In cyanobacteria, different psbA genes are present in the genome. The thermophilic cyanobacterium Thermosynechococcus elongatus contains three psbA genes: psbA1, psbA2, and psbA3, and a new c-type heme protein, Tll0287, was found to be expressed in a strain expressing the psbA2 gene only, but the structure and function of Tll0287 are unknown. Here we solved the crystal structure of Tll0287 at a 2.0 Å resolution. The overall structure of Tll0287 was found to be similar to some kinases and sensor proteins with a Per-Arnt-Sim-like domain rather than to other c-type cytochromes. The fifth and sixth axial ligands for the heme were Cys and His, instead of the His/Met or His/His ligand pairs observed for most of the c-type hemes. The redox potential, E½, of Tll0287 was -255 ± 20 mV versus normal hydrogen electrode at pH values above 7.5. Below this pH value, the E½ increased by ≈57 mV/pH unit at 15 °C, suggesting the involvement of a protonatable group with a pKred = 7.2 ± 0.3. Possible functions of Tll0287 as a redox sensor under microaerobic conditions or a cytochrome subunit of an H2S-oxidizing system are discussed in view of the environmental conditions in which psbA2 is expressed, as well as phylogenetic analysis, structural, and sequence homologies.
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Affiliation(s)
- Taiki Motomura
- From the Department of Picobiology, Graduate School of Life Science, University of Hyogo, Hyogo 678-1297, Japan.,the Research Institute for Interdisciplinary Science and Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan
| | - Michihiro Suga
- the Research Institute for Interdisciplinary Science and Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan
| | - Rainer Hienerwadel
- the Laboratoire de Génétique et Biophysique des Plantes, UMR 7265, CNRS-CEA-Aix-Marseille Université, Faculté des Sciences de Luminy, 13288 Marseille, France
| | - Akiko Nakagawa
- the Research Institute for Interdisciplinary Science and Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan.,the Proteo-Science Research Center, Ehime University, Ehime 790-8577, Japan
| | - Thanh-Lan Lai
- iBiTec-S, SB2SM, CNRS UMR 9198, CEA Saclay, 91191 Gif-sur-Yvette, France, and
| | - Wolfgang Nitschke
- the Laboratoire de Bioénergétique et Ingénierie des Protéines, CNRS UMR 7281, 13402 Marseille Cedex 20, France
| | - Takahiro Kuma
- the Research Institute for Interdisciplinary Science and Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan
| | - Miwa Sugiura
- the Proteo-Science Research Center, Ehime University, Ehime 790-8577, Japan
| | - Alain Boussac
- iBiTec-S, SB2SM, CNRS UMR 9198, CEA Saclay, 91191 Gif-sur-Yvette, France, and
| | - Jian-Ren Shen
- From the Department of Picobiology, Graduate School of Life Science, University of Hyogo, Hyogo 678-1297, Japan, .,the Research Institute for Interdisciplinary Science and Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan
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27
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Engineered holocytochrome c synthases that biosynthesize new cytochromes c. Proc Natl Acad Sci U S A 2017; 114:2235-2240. [PMID: 28196881 DOI: 10.1073/pnas.1615929114] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Cytochrome c (cyt c), required for electron transport in mitochondria, possesses a covalently attached heme cofactor. Attachment is catalyzed by holocytochrome c synthase (HCCS), leading to two thioether bonds between heme and a conserved CXXCH motif of cyt c In cyt c, histidine (His19) of CXXCH acts as an axial ligand to heme iron and upon release of holocytochrome c from HCCS, folding leads to formation of a second axial interaction with methionine (Met81). We previously discovered mutations in human HCCS that facilitate increased biosynthesis of cyt c in recombinant Escherichia coli Focusing on HCCS E159A, novel cyt c variants in quantities that are sufficient for biophysical analysis are biosynthesized. Cyt c H19M, the first bis-Met liganded cyt c, is compared with other axial ligand variants (M81A, M81H) and single thioether cyt c variants. For variants with axial ligand substitutions, electronic absorption, near-UV circular dichroism, and electron paramagnetic resonance spectroscopy provide evidence that axial ligands are changed and the heme environment is altered. Circular dichroism spectra in far UV and thermal denaturation analyses demonstrate that axial ligand changes do not affect secondary structures and stability. Redox potentials span a 400-mV range (+349 mV vs. standard hydrogen electrode, H19M; +252 mV, WT; -19 mV, M81A; -69 mV, M81H). We discuss the results in the context of a four-step mechanism for HCCS, whereby HCCS mutants such as E159A are enhanced in release (step 4) of cyt c from the HCCS active site; thus, we term these "release mutants."
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28
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Galardon E, Huguet F, Herrero C, Ricoux R, Artaud I, Padovani D. Reactions of persulfides with the heme cofactor of oxidized myoglobin and microperoxidase 11: reduction or coordination. Dalton Trans 2017; 46:7939-7946. [DOI: 10.1039/c7dt01638g] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Persulfides reduce both met- and ferryl-oxidized forms of myoglobin, and coordinate to N-acetylated microperoxidase-11.
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Affiliation(s)
- Erwan Galardon
- UMR 8601
- LCBPT
- CNRS-Université Paris Descartes
- 75006 Paris
- France
| | - Florian Huguet
- UMR 8601
- LCBPT
- CNRS-Université Paris Descartes
- 75006 Paris
- France
| | - Christian Herrero
- UMR 8182
- ICMMO
- Institut de Chimie Moléculaire et des Matériaux d'Orsay
- Université Paris-Sud
- 91405 Orsay Cedex
| | - Rémy Ricoux
- UMR 8182
- ICMMO
- Institut de Chimie Moléculaire et des Matériaux d'Orsay
- Université Paris-Sud
- 91405 Orsay Cedex
| | - Isabelle Artaud
- UMR 8601
- LCBPT
- CNRS-Université Paris Descartes
- 75006 Paris
- France
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29
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Kleingardner EC, Asher WB, Bren KL. Efficient and Flexible Preparation of Biosynthetic Microperoxidases. Biochemistry 2016; 56:143-148. [DOI: 10.1021/acs.biochem.6b00915] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Erin C. Kleingardner
- Department of Chemistry, University of Rochester, Rochester, New York 14627-0216, United States
| | - Wesley B. Asher
- Department of Chemistry, University of Rochester, Rochester, New York 14627-0216, United States
| | - Kara L. Bren
- Department of Chemistry, University of Rochester, Rochester, New York 14627-0216, United States
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30
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Bouzhir-Sima L, Motterlini R, Gross J, Vos MH, Liebl U. Unusual Dynamics of Ligand Binding to the Heme Domain of the Bacterial CO Sensor Protein RcoM-2. J Phys Chem B 2016; 120:10686-10694. [DOI: 10.1021/acs.jpcb.6b08160] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Latifa Bouzhir-Sima
- LOB,
Ecole Polytechnique, CNRS, INSERM, Université Paris-Saclay, 91128 Palaiseau Cedex, France
| | - Roberto Motterlini
- Faculté
de Médicine, Université Paris-Est, Créteil 94000, France
- INSERM, U955, Equipe 12, Créteil 94000, France
| | - Julia Gross
- LOB,
Ecole Polytechnique, CNRS, INSERM, Université Paris-Saclay, 91128 Palaiseau Cedex, France
| | - Marten H. Vos
- LOB,
Ecole Polytechnique, CNRS, INSERM, Université Paris-Saclay, 91128 Palaiseau Cedex, France
| | - Ursula Liebl
- LOB,
Ecole Polytechnique, CNRS, INSERM, Université Paris-Saclay, 91128 Palaiseau Cedex, France
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31
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Potentiation of hydrogen peroxide toxicity: From catalase inhibition to stable DNA-iron complexes. MUTATION RESEARCH-REVIEWS IN MUTATION RESEARCH 2016; 773:274-281. [PMID: 28927535 DOI: 10.1016/j.mrrev.2016.08.006] [Citation(s) in RCA: 70] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 04/22/2016] [Accepted: 08/29/2016] [Indexed: 12/15/2022]
Abstract
Hydrogen peroxide (H2O2) is unique among general toxins, because it is stable in abiotic environments at ambient temperature and neutral pH, yet rapidly kills any type of cells by producing highly-reactive hydroxyl radicals. This life-specific reactivity follows the distribution of soluble iron, Fe(II) (which combines with H2O2 to form the famous Fenton's reagent),Fe(II) is concentrated inside cells, but is virtually absent outside them. Because of the immediate danger of H2O2, all cells have powerful H2O2 scavengers, the equally famous catalases, which enable cells to survive thousand-fold higher concentrations of H2O2 and, in combination with adequate movement of H2O2 across membranes, make the killing H2O2 concentrations virtually impractical to generate in vivo. And yet, low concentrations of H2O2 are somehow used as an efficient biological weapon. Here we review several examples of how cells potentiate H2O2 toxicity with other chemicals. At first, these potentiators were thought to simply inhibit catalases, but recent findings with cyanide suggest that potentiators mostly promote the other side of Fenton's reaction, recruiting iron from cell depots into stable DNA-iron complexes that, in the presence of elevated H2O2, efficiently break duplex DNA, pulverizing the chromosome. This multifaceted potentiation of H2O2 toxicity results in robust and efficient killing.
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32
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Da Silva JCS, Pennifold RCR, Harvey JN, Rocha WR. A radical rebound mechanism for the methane oxidation reaction promoted by the dicopper center of a pMMO enzyme: a computational perspective. Dalton Trans 2016; 45:2492-504. [DOI: 10.1039/c5dt02638e] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Hydrogen Atom Transfer (HAT) promoted by a triplet state of the bis-oxoCu2(iii) core generates a new radical rebound mechanism for the hydroxylation of methane catalyzed by the binuclear copper site of a pMMO enzyme.
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Affiliation(s)
- Júlio C. S. Da Silva
- BioMat: Biomaterial Modeling Group
- Departamento de Química Fundamental
- CCEN
- Universidade Federal de Pernambuco
- Cidade Universitária
| | | | | | - Willian R. Rocha
- LQC-MM: Laboratório de Química Computacional e Modelagem Molecular
- Departamento de Química
- ICEX
- Universidade Federal de Minas Gerais
- Belo Horizonte
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33
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Morozov AN, Pardillo AD, Chatfield DC. Chloroperoxidase-Catalyzed Epoxidation of Cis-β-Methylstyrene: NH-S Hydrogen Bonds and Proximal Helix Dipole Change the Catalytic Mechanism and Significantly Lower the Reaction Barrier. J Phys Chem B 2015; 119:14350-63. [PMID: 26452587 DOI: 10.1021/acs.jpcb.5b06731] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Proximal hydrogen bonding of the axial sulfur with the backbone amides (NH-S) is a conserved feature of heme-thiolate enzymes such as chloroperoxidase (CPO) and cytochrome P450 (P450). In CPO, the effect of NH-S bonds is amplified by the dipole moment of the proximal helix. Our gas-phase DFT studies show that the proximal pocket effect significantly enhances CPO's reactivity toward the epoxidation of olefinic substrates. Comparison of models with and without proximal pocket residues shows that with them, the barrier for Cβ-O bond formation is lowered by about ∼4.6 kcal/mol, while Cα-O-Cβ ring closure becomes barrierless. The dipole moment of the proximal helix was estimated to contribute 1/3 of the decrease, while the rest is attributed to the effect of NH-S bonds. The decrease of the reaction barrier correlates with increased electron density transfer to residues of the proximal pocket. The effect is most pronounced on the doublet spin surface and involves a change in the electron-transfer mechanism. A full enzyme QMMM study on the doublet spin surface gives about the same barrier as the gas-phase DFT study. The free-energy barrier was estimated to be in agreement with the experimental results for the CPO-catalyzed epoxidation of styrene.
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Affiliation(s)
- Alexander N Morozov
- Department of Chemistry and Biochemistry, Florida International University , 11200 Southwest Eighth Street, Miami, Florida 33199, United States
| | - Armando D Pardillo
- Department of Chemistry and Biochemistry, Florida International University , 11200 Southwest Eighth Street, Miami, Florida 33199, United States
| | - David C Chatfield
- Department of Chemistry and Biochemistry, Florida International University , 11200 Southwest Eighth Street, Miami, Florida 33199, United States
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34
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Haddad AZ, Kumar D, Ouch Sampson K, Matzner AM, Mashuta MS, Grapperhaus CA. Proposed Ligand-Centered Electrocatalytic Hydrogen Evolution and Hydrogen Oxidation at a Noninnocent Mononuclear Metal-Thiolate. J Am Chem Soc 2015; 137:9238-41. [PMID: 26161802 DOI: 10.1021/jacs.5b05561] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The noninnocent coordinatively saturated mononuclear metal-thiolate complex ReL3 (L = diphenylphosphinobenzenethiolate) serves as an electrocatalyst for hydrogen evolution or hydrogen oxidation dependent on the presence of acid or base and the applied potential. ReL3 reduces acids to H2 in dichloromethane with an overpotential of 380 mV and a turnover frequency of 32 ± 3 s(-1). The rate law displays a second-order dependence on acid concentration and a first-order dependence on catalyst concentration with an overall third-order rate constant (k) of 184 ± 2 M(-2) s(-1). Reactions with deuterated acid display a kinetic isotope effect of 9 ± 1. In the presence of base, ReL3 oxidizes H2 with a turnover frequency of 4 ± 1 s(-1). The X-ray crystal structure of the monoprotonated species [Re(LH)L2](+), an intermediate in both catalytic H2 evolution and oxidation, has been determined. A ligand-centered mechanism, which does not require metal hydride intermediates, is suggested based on similarities to the redox-regulated, ligand-centered binding of ethylene to ReL3.
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Affiliation(s)
- Andrew Z Haddad
- Department of Chemistry, University of Louisville, 2320 South Brook Street, Louisville, Kentucky 40292, United States
| | - Davinder Kumar
- Department of Chemistry, University of Louisville, 2320 South Brook Street, Louisville, Kentucky 40292, United States
| | - Kagna Ouch Sampson
- Department of Chemistry, University of Louisville, 2320 South Brook Street, Louisville, Kentucky 40292, United States
| | - Anna M Matzner
- Department of Chemistry, University of Louisville, 2320 South Brook Street, Louisville, Kentucky 40292, United States
| | - Mark S Mashuta
- Department of Chemistry, University of Louisville, 2320 South Brook Street, Louisville, Kentucky 40292, United States
| | - Craig A Grapperhaus
- Department of Chemistry, University of Louisville, 2320 South Brook Street, Louisville, Kentucky 40292, United States
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35
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Amacher JF, Zhong F, Lisi GP, Zhu MQ, Alden SL, Hoke KR, Madden DR, Pletneva EV. A Compact Structure of Cytochrome c Trapped in a Lysine-Ligated State: Loop Refolding and Functional Implications of a Conformational Switch. J Am Chem Soc 2015; 137:8435-49. [PMID: 26038984 DOI: 10.1021/jacs.5b01493] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
It has been suggested that the alkaline form of cytochrome c (cyt c) regulates function of this protein as an electron carrier in oxidative phosphorylation and as a peroxidase that reacts with cardiolipin (CL) during apoptosis. In this form, Met80, the native ligand to the heme iron, is replaced by a Lys. While it has become clear that the structure of cyt c changes, the extent and sequence of conformational rearrangements associated with this ligand replacement remain a subject of debate. Herein we report a high-resolution crystal structure of a Lys73-ligated cyt c conformation that reveals intricate change in the heme environment upon this switch in the heme iron ligation. The structure is surprisingly compact, and the heme coordination loop refolds into a β-hairpin with a turn formed by the highly conserved residues Pro76 and Gly77. Repositioning of residue 78 modifies the intraprotein hydrogen-bonding network and, together with adjustments of residues 52 and 74, increases the volume of the heme pocket to allow for insertion of one of the CL acyl moieties next to Asn52. Derivatization of Cys78 with maleimide creates a solution mimic of the Lys-ligated cyt c that has enhanced peroxidase activity, adding support for a role of the Lys-ligated cyt c in the apoptotic mechanism. Experiments with the heme peptide microperoxidase-8 and engineered model proteins provide a thermodynamic rationale for the switch to Lys ligation upon perturbations in the protein scaffold.
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Affiliation(s)
- Jeanine F Amacher
- †Department of Biochemistry, Geisel School of Medicine, Hanover, New Hampshire 03755, United States
| | - Fangfang Zhong
- ‡Department of Chemistry, Dartmouth College, Hanover, New Hampshire 03755, United States
| | - George P Lisi
- ‡Department of Chemistry, Dartmouth College, Hanover, New Hampshire 03755, United States
| | - Michael Q Zhu
- ‡Department of Chemistry, Dartmouth College, Hanover, New Hampshire 03755, United States
| | - Stephanie L Alden
- ‡Department of Chemistry, Dartmouth College, Hanover, New Hampshire 03755, United States
| | - Kevin R Hoke
- §Department of Chemistry, Berry College, Mount Berry, Georgia 30149, United States
| | - Dean R Madden
- †Department of Biochemistry, Geisel School of Medicine, Hanover, New Hampshire 03755, United States
| | - Ekaterina V Pletneva
- †Department of Biochemistry, Geisel School of Medicine, Hanover, New Hampshire 03755, United States.,‡Department of Chemistry, Dartmouth College, Hanover, New Hampshire 03755, United States
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36
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Beltrán J, Kloss B, Hosler JP, Geng J, Liu A, Modi A, Dawson JH, Sono M, Shumskaya M, Ampomah-Dwamena C, Love JD, Wurtzel ET. Control of carotenoid biosynthesis through a heme-based cis-trans isomerase. Nat Chem Biol 2015; 11:598-605. [PMID: 26075523 PMCID: PMC4509827 DOI: 10.1038/nchembio.1840] [Citation(s) in RCA: 66] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2014] [Accepted: 05/13/2015] [Indexed: 01/27/2023]
Abstract
Plants synthesize carotenoids essential for plant development and survival. These metabolites also serve as essential nutrients for human health. The biosynthetic pathway leading to all plant carotenoids occurs in chloroplasts and other plastids and requires 15-cis-ζ-carotene isomerase (Z-ISO). It was not certain whether isomerization was achieved by Z-ISO alone or in combination with other enzymes. Here we show that Z-ISO is a bona fide enzyme and integral membrane protein. Z-ISO independently catalyzes the cis-to-trans isomerization of the 15–15′ C=C bond in 9,15,9′-cis-ζ-carotene to produce the substrate required by the following biosynthetic pathway enzyme. We discovered that isomerization depends upon a ferrous heme b cofactor that undergoes redox-regulated ligand-switching between the heme iron and alternate Z-ISO amino acid residues. Heme b-dependent isomerization of a large, hydrophobic compound in a membrane is unprecedented. As an isomerase, Z-ISO represents a new prototype for heme b proteins and potentially utilizes a novel chemical mechanism.
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Affiliation(s)
- Jesús Beltrán
- 1] Department of Biological Sciences, Lehman College, City University of New York (CUNY), Bronx, New York, USA. [2] Graduate School and University Center, CUNY, New York, New York, USA
| | - Brian Kloss
- New York Structural Biology Center, New York, New York, USA
| | - Jonathan P Hosler
- Department of Biochemistry, University of Mississippi Medical Center, Jackson, Mississippi, USA
| | - Jiafeng Geng
- Department of Chemistry, Georgia State University, Atlanta, Georgia, USA
| | - Aimin Liu
- Department of Chemistry, Georgia State University, Atlanta, Georgia, USA
| | - Anuja Modi
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina, USA
| | - John H Dawson
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina, USA
| | - Masanori Sono
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina, USA
| | - Maria Shumskaya
- Department of Biological Sciences, Lehman College, City University of New York (CUNY), Bronx, New York, USA
| | - Charles Ampomah-Dwamena
- Department of Biological Sciences, Lehman College, City University of New York (CUNY), Bronx, New York, USA
| | - James D Love
- New York Structural Biology Center, New York, New York, USA
| | - Eleanore T Wurtzel
- 1] Department of Biological Sciences, Lehman College, City University of New York (CUNY), Bronx, New York, USA. [2] Graduate School and University Center, CUNY, New York, New York, USA
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Vitvitsky V, Yadav PK, Kurthen A, Banerjee R. Sulfide oxidation by a noncanonical pathway in red blood cells generates thiosulfate and polysulfides. J Biol Chem 2015; 290:8310-20. [PMID: 25688092 PMCID: PMC4375485 DOI: 10.1074/jbc.m115.639831] [Citation(s) in RCA: 122] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2015] [Revised: 02/12/2015] [Indexed: 11/06/2022] Open
Abstract
A cardioprotectant at low concentrations, H2S is a toxin at high concentrations and inhibits cytochrome c oxidase. A conundrum in H2S homeostasis is its fate in red blood cells (RBCs), which produce H2S but lack the canonical mitochondrial sulfide oxidation pathway for its clearance. The sheer abundance of RBCs in circulation enhances the metabolic significance of their clearance strategy for H2S, necessary to avoid systemic toxicity. In this study, we demonstrate that H2S generation by RBCs is catalyzed by mercaptopyruvate sulfurtransferase. Furthermore, we have discovered the locus of sulfide oxidation in RBCs and describe a new role for an old protein, hemoglobin, which in the ferric or methemoglobin state binds H2S and oxidizes it to a mixture of thiosulfate and hydropolysulfides. Our study reveals a previously undescribed route for the biogenesis of hydropolysulfides, which are increasingly considered important for H2S-based signaling, but their origin in mammalian cells is unknown. An NADPH/flavoprotein oxidoreductase system restores polysulfide-carrying hemoglobin derivatives to ferrous hemoglobin, thus completing the methemoglobin-dependent sulfide oxidation cycle. Methemoglobin-dependent sulfide oxidation in mammals is complex and has similarities to chemistry reported for the dissolution of iron oxides in sulfidic waters and during bioleaching of metal sulfides. The catalytic oxidation of H2S by hemoglobin explains how RBCs maintain low steady-state H2S levels in circulation, and suggests that additional hemeproteins might be involved in sulfide homeostasis in other tissues.
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Affiliation(s)
- Victor Vitvitsky
- From the Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, Michigan 48109-0600
| | - Pramod K Yadav
- From the Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, Michigan 48109-0600
| | - Angelika Kurthen
- From the Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, Michigan 48109-0600
| | - Ruma Banerjee
- From the Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, Michigan 48109-0600
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Smith AT, Pazicni S, Marvin KA, Stevens DJ, Paulsen KM, Burstyn JN. Functional divergence of heme-thiolate proteins: a classification based on spectroscopic attributes. Chem Rev 2015; 115:2532-58. [PMID: 25763468 DOI: 10.1021/cr500056m] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Aaron T Smith
- †Department of Molecular Biosciences, Northwestern University, 2205 Tech Drive, Evanston, Illinois 60208, United States
| | - Samuel Pazicni
- ‡Department of Chemistry, University of New Hampshire, 23 Academic Way, Durham, New Hampshire 03824, United States
| | - Katherine A Marvin
- §Department of Chemistry, Hendrix College, 1600 Washington Avenue, Conway, Arkansas 72032, United States
| | - Daniel J Stevens
- ∥Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, Wisconsin 53706, United States
| | - Katherine M Paulsen
- ∥Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, Wisconsin 53706, United States
| | - Judith N Burstyn
- ∥Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, Wisconsin 53706, United States
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Brito JA, Denkmann K, Pereira IAC, Archer M, Dahl C. Thiosulfate dehydrogenase (TsdA) from Allochromatium vinosum: structural and functional insights into thiosulfate oxidation. J Biol Chem 2015; 290:9222-38. [PMID: 25673691 DOI: 10.1074/jbc.m114.623397] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2014] [Indexed: 11/06/2022] Open
Abstract
Although the oxidative condensation of two thiosulfate anions to tetrathionate constitutes a well documented and significant part of the natural sulfur cycle, little is known about the enzymes catalyzing this reaction. In the purple sulfur bacterium Allochromatium vinosum, the reaction is catalyzed by the periplasmic diheme c-type cytochrome thiosulfate dehydrogenase (TsdA). Here, we report the crystal structure of the "as isolated" form of A. vinosum TsdA to 1.98 Å resolution and those of several redox states of the enzyme to different resolutions. The protein contains two typical class I c-type cytochrome domains wrapped around two hemes axially coordinated by His(53)/Cys(96) and His(164)/Lys(208). These domains are very similar, suggesting a gene duplication event during evolution. A ligand switch from Lys(208) to Met(209) is observed upon reduction of the enzyme. Cys(96) is an essential residue for catalysis, with the specific activity of the enzyme being completely abolished in several TsdA-Cys(96) variants. TsdA-K208N, K208G, and M209G variants were catalytically active in thiosulfate oxidation as well as in tetrathionate reduction, pointing to heme 2 as the electron exit point. In this study, we provide spectroscopic and structural evidence that the TsdA reaction cycle involves the transient presence of heme 1 in the high-spin state caused by movement of the Sγ atom of Cys(96) out of the iron coordination sphere. Based on the presented data, we draw important conclusions about the enzyme and propose a possible reaction mechanism for TsdA.
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Affiliation(s)
- José A Brito
- From the Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa (ITQB-UNL), Avenida da República, 2780-157 Oeiras, Portugal and
| | - Kevin Denkmann
- the Institut für Mikrobiologie & Biotechnologie, Rheinische Friedrich-Wilhelms-Universität Bonn, D-53115 Bonn, Germany
| | - Inês A C Pereira
- From the Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa (ITQB-UNL), Avenida da República, 2780-157 Oeiras, Portugal and
| | - Margarida Archer
- From the Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa (ITQB-UNL), Avenida da República, 2780-157 Oeiras, Portugal and
| | - Christiane Dahl
- the Institut für Mikrobiologie & Biotechnologie, Rheinische Friedrich-Wilhelms-Universität Bonn, D-53115 Bonn, Germany
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40
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Du JF, Li W, Li L, Wen GB, Lin YW, Tan X. Regulating the coordination state of a heme protein by a designed distal hydrogen-bonding network. ChemistryOpen 2014; 4:97-101. [PMID: 25969804 PMCID: PMC4420578 DOI: 10.1002/open.201402108] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2014] [Indexed: 01/03/2023] Open
Abstract
Heme coordination state determines the functional diversity of heme proteins. Using myoglobin as a model protein, we designed a distal hydrogen-bonding network by introducing both distal glutamic acid (Glu29) and histidine (His43) residues and regulated the heme into a bis-His coordination state with native ligands His64 and His93. This resembles the heme site in natural bis-His coordinated heme proteins such as cytoglobin and neuroglobin. A single mutation of L29E or F43H was found to form a distinct hydrogen-bonding network involving distal water molecules, instead of the bis-His heme coordination, which highlights the importance of the combination of multiple hydrogen-bonding interactions to regulate the heme coordination state. Kinetic studies further revealed that direct coordination of distal His64 to the heme iron negatively regulates fluoride binding and hydrogen peroxide activation by competing with the exogenous ligands. The new approach developed in this study can be generally applicable for fine-tuning the structure and function of heme proteins.
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Affiliation(s)
- Jun-Fang Du
- School of Chemistry and Chemical Engineering, University of South China Hengyang, 421001, (P. R. China))
| | - Wei Li
- Department of Chemistry and Institute of Biomedical Science, Fudan University Shanghai, 200433, (P. R. China)
| | - Lianzhi Li
- School of Chemistry and Chemical Engineering, Liaocheng University Liaocheng, 252059, (P. R. China)
| | - Ge-Bo Wen
- Laboratory of Protein Structure and Function, University of South China Hengyang, 421001, (P. R. China)
| | - Ying-Wu Lin
- School of Chemistry and Chemical Engineering, University of South China Hengyang, 421001, (P. R. China)) ; Laboratory of Protein Structure and Function, University of South China Hengyang, 421001, (P. R. China)
| | - Xiangshi Tan
- Department of Chemistry and Institute of Biomedical Science, Fudan University Shanghai, 200433, (P. R. China)
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Pramanik S, Kutzner A, Heese K. Lead discovery and in silico 3D structure modeling of tumorigenic FAM72A (p17). Tumour Biol 2014; 36:239-49. [PMID: 25234718 DOI: 10.1007/s13277-014-2620-7] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2014] [Accepted: 09/09/2014] [Indexed: 12/30/2022] Open
Abstract
FAM72A (p17) is a novel neuronal protein that has been linked to tumorigenic effects in non-neuronal tissue. Using state of the art in silico physicochemical analyses (e.g., I-TASSER, RaptorX, and Modeller), we determined the three-dimensional (3D) protein structure of FAM72A and further identified potential ligand-protein interactions. Our data indicate a Zn(2+)/Fe(3+)-containing 3D protein structure, based on a 3GA3_A model template, which potentially interacts with the organic molecule RSM ((2s)-2-(acetylamino)-N-methyl-4-[(R)-methylsulfinyl] butanamide). The discovery of RSM may serve as potential lead for further anti-FAM72A drug screening tests in the pharmaceutical industry because interference with FAM72A's activities via RSM-related molecules might be a novel option to influence the tumor suppressor protein p53 signaling pathways for the treatment of various types of cancers.
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Affiliation(s)
- Subrata Pramanik
- Graduate School of Biomedical Science and Engineering, Hanyang University, 222 Wangsimni-ro, Seongdong-gu, Seoul, 133-791, Republic of Korea
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The dynamic complex of cytochrome c6 and cytochrome f studied with paramagnetic NMR spectroscopy. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2014; 1837:1305-15. [DOI: 10.1016/j.bbabio.2014.03.009] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/27/2014] [Revised: 03/13/2014] [Accepted: 03/16/2014] [Indexed: 11/23/2022]
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