1
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Alvarez-Hernandez JL, Salamatian AA, Sopchak AE, Bren KL. Hydrogen evolution catalysis by a cobalt porphyrin peptide: A proposed role for porphyrin propionic acid groups. J Inorg Biochem 2023; 249:112390. [PMID: 37801884 DOI: 10.1016/j.jinorgbio.2023.112390] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2023] [Revised: 09/11/2023] [Accepted: 09/26/2023] [Indexed: 10/08/2023]
Abstract
Cobalt microperoxidase-11 (CoMP11-Ac) is a cobalt porphyrin-peptide catalyst for hydrogen (H2) evolution from water. Herein, we assess electrocatalytic activity of CoMP11-Ac from pH 1.0-10.0. This catalyst remains intact and active under highly acidic conditions (pH 1.0) that are desirable for maximizing H2 evolution activity. Analysis of electrochemical data indicate that H2 evolution takes place by two pH-dependent mechanisms. At pH < 4.3, a proton transfer mechanism involving the propionic acid groups of the porphyrin is proposed, decreasing the catalytic overpotential by 280 mV.
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Affiliation(s)
| | - Alison A Salamatian
- Department of Chemistry, University of Rochester. Rochester, NY 14627-0216, United States.
| | - Andrew E Sopchak
- Department of Chemistry, University of Rochester. Rochester, NY 14627-0216, United States.
| | - Kara L Bren
- Department of Chemistry, University of Rochester. Rochester, NY 14627-0216, United States.
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2
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Edwards EH, Jelušić J, Kosko RM, McClelland KP, Ngarnim SS, Chiang W, Lampa-Pastirk S, Krauss TD, Bren KL. Shewanella oneidensis MR-1 respires CdSe quantum dots for photocatalytic hydrogen evolution. Proc Natl Acad Sci U S A 2023; 120:e2206975120. [PMID: 37068259 PMCID: PMC10151509 DOI: 10.1073/pnas.2206975120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2022] [Accepted: 03/21/2023] [Indexed: 04/19/2023] Open
Abstract
Living bio-nano systems for artificial photosynthesis are of growing interest. Typically, these systems use photoinduced charge transfer to provide electrons for microbial metabolic processes, yielding a biosynthetic solar fuel. Here, we demonstrate an entirely different approach to constructing a living bio-nano system, in which electrogenic bacteria respire semiconductor nanoparticles to support nanoparticle photocatalysis. Semiconductor nanocrystals are highly active and robust photocatalysts for hydrogen (H2) evolution, but their use is hindered by the oxidative side of the reaction. In this system, Shewanella oneidensis MR-1 provides electrons to a CdSe nanocrystalline photocatalyst, enabling visible light-driven H2 production. Unlike microbial electrolysis cells, this system requires no external potential. Illuminating this system at 530 nm yields continuous H2 generation for 168 h, which can be lengthened further by replenishing bacterial nutrients.
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Affiliation(s)
- Emily H. Edwards
- Department of Chemistry, University of Rochester, Rochester, NY14627
| | - Jana Jelušić
- Department of Chemistry, University of Rochester, Rochester, NY14627
| | - Ryan M. Kosko
- Department of Chemistry, University of Rochester, Rochester, NY14627
| | | | - Soraya S. Ngarnim
- Department of Chemistry, University of Rochester, Rochester, NY14627
| | - Wesley Chiang
- Department of Biochemistry and Biophysics, University of Rochester, Rochester, NY14627
| | | | - Todd D. Krauss
- Department of Chemistry, University of Rochester, Rochester, NY14627
- Department of Optics, University of Rochester, Rochester, NY14627
| | - Kara L. Bren
- Department of Chemistry, University of Rochester, Rochester, NY14627
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3
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Salamatian AA, Bren KL. Bioinspired and biomolecular catalysts for energy conversion and storage. FEBS Lett 2023; 597:174-190. [PMID: 36331366 DOI: 10.1002/1873-3468.14533] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2022] [Revised: 10/25/2022] [Accepted: 10/26/2022] [Indexed: 11/06/2022]
Abstract
Metalloenzymes are remarkable for facilitating challenging redox transformations with high efficiency and selectivity. In the area of alternative energy, scientists aim to capture these properties in bioinspired and engineered biomolecular catalysts for the efficient and fast production of fuels from low-energy feedstocks such as water and carbon dioxide. In this short review, efforts to mimic biological catalysts for proton reduction and carbon dioxide reduction are highlighted. Two important recurring themes are the importance of the microenvironment of the catalyst active site and the key role of proton delivery to the active site in achieving desired reactivity. Perspectives on ongoing and future challenges are also provided.
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Affiliation(s)
| | - Kara L Bren
- Department of Chemistry, University of Rochester, NY, USA
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4
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Alvarez-Hernandez JL, Salamatian AA, Han JW, Bren KL. Potential- and Buffer-Dependent Selectivity for the Conversion of CO 2 to CO by a Cobalt Porphyrin-Peptide Electrocatalyst in Water. ACS Catal 2022; 12:14689-14697. [PMID: 36504916 PMCID: PMC9724230 DOI: 10.1021/acscatal.2c03297] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2022] [Revised: 11/02/2022] [Indexed: 11/17/2022]
Abstract
A semisynthetic electrocatalyst for carbon dioxide reduction to carbon monoxide in water is reported. Cobalt microperoxidase-11 (CoMP11-Ac) is shown to reduce CO2 to CO with a turnover number of up to 32,000 and a selectivity of up to 88:5 CO:H2. Higher selectivity for CO production is favored by a less cathodic applied potential and use of a higher pK a buffer. A mechanistic hypothesis is presented in which avoiding the formation and protonation of a formal Co(I) species favors CO production. These results demonstrate how tuning reaction conditions impact reactivity toward CO2 reduction for a biocatalyst previously developed for H2 production.
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5
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Chattopadhyay S, Mukherjee M, Kandemir B, Bowman SEJ, Bren KL, Dey A. Contributions to cytochrome c inner- and outer-sphere reorganization energy. Chem Sci 2021; 12:11894-11913. [PMID: 34659730 PMCID: PMC8442690 DOI: 10.1039/d1sc02865k] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2021] [Accepted: 08/05/2021] [Indexed: 11/21/2022] Open
Abstract
Cytochromes c are small water-soluble proteins that catalyze electron transfer in metabolism and energy conversion processes. Hydrogenobacter thermophilus cytochrome c552 presents a curious case in displaying fluxionality of its heme axial methionine ligand; this behavior is altered by single point mutation of the Q64 residue to N64 or V64, which fixes the ligand in a single configuration. The reorganization energy (λ) of these cytochrome c552 variants is experimentally determined using a combination of rotating disc electrochemistry, chronoamperometry and cyclic voltammetry. The differences between the λ determined from these complementary techniques helps to deconvolute the contribution of the active site and its immediate environment to the overall λ (λTotal). The experimentally determined λ values in conjunction with DFT calculations indicate that the differences in λ among the protein variants are mainly due to the differences in contributions from the protein environment and not just inner-sphere λ. DFT calculations indicate that the position of residue 64, responsible for the orientation of the axial methionine, determines the geometric relaxation of the redox active molecular orbital (RAMO). The orientation of the RAMO with respect to the heme is key to determining electron transfer coupling (HAB) which results in higher ET rates in the wild-type protein relative to the Q64V mutant despite a 150 mV higher λTotal in the former. Efficient delocalization of the redox-active molecular orbital (RAMO) in HtWT results in an increase in HAB value which in turn accelerates the electron transfer (ET) rate in spite of the higher reorganization energy (λ) than the HtQ64V mutant.![]()
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Affiliation(s)
- Samir Chattopadhyay
- School of Chemical Sciences, Indian Association for the Cultivation of Science 2A Raja SC Mullick Road Kolkata WB 700032 India
| | - Manjistha Mukherjee
- School of Chemical Sciences, Indian Association for the Cultivation of Science 2A Raja SC Mullick Road Kolkata WB 700032 India
| | - Banu Kandemir
- Department of Chemistry, University of Rochester Rochester NY 14627-0216 USA
| | - Sarah E J Bowman
- Department of Chemistry, University of Rochester Rochester NY 14627-0216 USA
| | - Kara L Bren
- Department of Chemistry, University of Rochester Rochester NY 14627-0216 USA
| | - Abhishek Dey
- School of Chemical Sciences, Indian Association for the Cultivation of Science 2A Raja SC Mullick Road Kolkata WB 700032 India
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6
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Zuo K, Marjault HB, Bren KL, Rossetti G, Nechushtai R, Carloni P. The two redox states of the human NEET proteins' [2Fe-2S] clusters. J Biol Inorg Chem 2021; 26:763-774. [PMID: 34453614 PMCID: PMC8463382 DOI: 10.1007/s00775-021-01890-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2021] [Accepted: 07/26/2021] [Indexed: 11/04/2022]
Abstract
The NEET proteins constitute a unique class of [2Fe–2S] proteins. The metal ions bind to three cysteines and one histidine. The proteins’ clusters exist in two redox states; the oxidized protein (containing two FeIII ions) can transfer the cluster to apo-acceptor protein(s), while the reduced form (containing one ferrous ion) remains bound to the protein frame. Here, we perform in silico and in vitro studies on human NEET proteins in both reduced and oxidized forms. Quantum chemical calculations on all available human NEET proteins structures suggest that reducing the cluster weakens the Fe–NHis and Fe–SCys bonds, similar to what is seen in other Fe–S proteins (e.g., ferredoxin and Rieske protein). We further show that the extra electron in the [2Fe–2S]+ clusters of one of the NEET proteins (mNT) is localized on the His-bound iron ion, consistently with our previous spectroscopic studies. Kinetic measurements demonstrate that the mNT [2Fe–2S]+ is released only by an increase in temperature. Thus, the reduced state of human NEET proteins [2Fe–2S] cluster is kinetically inert. This previously unrecognized kinetic inertness of the reduced state, along with the reactivity of the oxidized state, is unique across all [2Fe–2S] proteins. Finally, using a coevolutionary analysis, along with molecular dynamics simulations, we provide insight on the observed allostery between the loop L2 and the cluster region. Specifically, we show that W75, R76, K78, K79, F82 and G85 in the latter region share similar allosteric characteristics in both redox states.
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Affiliation(s)
- Ke Zuo
- The Alexander Silberman Institute of Life Science, The Hebrew University of Jerusalem, Edmond J. Safra Campus at Givat Ram, 91904, Jerusalem, Israel.,Department of Physics, RWTH Aachen University, 52074, Aachen, Germany
| | - Henri-Baptiste Marjault
- The Alexander Silberman Institute of Life Science, The Hebrew University of Jerusalem, Edmond J. Safra Campus at Givat Ram, 91904, Jerusalem, Israel.,Department of Physics, RWTH Aachen University, 52074, Aachen, Germany
| | - Kara L Bren
- Department of Chemistry, University of Rochester, Rochester, NY, 14627-0216, USA
| | - Giulia Rossetti
- Computational Biomedicine, Institute of Advanced Simulation IAS-5 and Institute of Neuroscience and Medicine INM-9, Forschungszentrum Jülich GmbH, 52425, Jülich, Germany.,Jülich Supercomputing Center (JSC), Forschungszentrum Jülich GmbH, Jülich, Germany.,Department of Neurology, Faculty of Medicine, RWTH Aachen University, 52074, Aachen, Germany
| | - Rachel Nechushtai
- The Alexander Silberman Institute of Life Science, The Hebrew University of Jerusalem, Edmond J. Safra Campus at Givat Ram, 91904, Jerusalem, Israel.
| | - Paolo Carloni
- Department of Physics, RWTH Aachen University, 52074, Aachen, Germany. .,Computational Biomedicine, Institute of Advanced Simulation IAS-5 and Institute of Neuroscience and Medicine INM-9, Forschungszentrum Jülich GmbH, 52425, Jülich, Germany. .,JARA Institute: Molecular Neuroscience and Imaging, Institute of Neuroscience and Medicine INM-11, Forschungszentrum Jülich GmbH, 52425, Jülich, Germany.
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7
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Burke R, Chakraborty S, McClelland KP, Jelušić J, Matson EM, Bren KL, Krauss TD. Light-driven hydrogen production with CdSe quantum dots and a cobalt glutathione catalyst. Chem Commun (Camb) 2021; 57:2053-2056. [PMID: 33507176 DOI: 10.1039/d0cc07364d] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
A photocatalytic hydrogen (H2) production system is reported using glutathione (GSH)-capped CdSe QDs with a cobalt precatalyst, yielding 130 000 mol H2 per mol cobalt over 48 hours. Analysis of the reaction mixtures after catalysis indicates that the active catalyst is a labile complex of cobalt and GSH formed in situ.
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Affiliation(s)
- Rebeckah Burke
- Department of Chemistry, University of Rochester, Rochester, New York 14627, USA.
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8
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Edwards EH, Jelušić J, Chakraborty S, Bren KL. Photochemical hydrogen evolution from cobalt microperoxidase-11. J Inorg Biochem 2021; 217:111384. [PMID: 33588276 DOI: 10.1016/j.jinorgbio.2021.111384] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2020] [Revised: 12/27/2020] [Accepted: 01/26/2021] [Indexed: 12/24/2022]
Abstract
A photochemical system utilizing the semisynthetic biomolecular catalyst acetylated cobalt microperoxidase-11 (CoMP11-Ac) along with [Ru(bpy)3]2+ as a photosensitizer and ascorbic acid as an electron donor is shown to generate hydrogen from water in a visible light-driven reaction. The reductive quenching pathway facilitated by photoexcited [Ru(bpy)3]2+ overcomes the high overpotential observed for CoMP11-Ac in electrocatalysis, yielding turnover numbers ranging from 606 to 2390 (2 μM - 0.1 μM CoMP11-Ac). The longevity of CoMP11-Ac in the photochemical system, sustaining catalysis for over 20 h, is in contrast to its previously reported behavior in an electrochemical system where catalysis slows after 15 min. Proton reduction turnover number and rate are highest at a neutral pH, a rare feature among cobalt catalysts in similar photochemical systems, which typically function best under acidic conditions. Incorporating biomolecular components into the design of catalysts for photochemical systems may address the need for hydrogen generation from neutral-pH water sources.
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Affiliation(s)
- Emily H Edwards
- Department of Chemistry, University of Rochester, Rochester, NY 14627, United States of America.
| | - Jana Jelušić
- Department of Chemistry, University of Rochester, Rochester, NY 14627, United States of America.
| | - Saikat Chakraborty
- Department of Chemistry, University of Rochester, Rochester, NY 14627, United States of America.
| | - Kara L Bren
- Department of Chemistry, University of Rochester, Rochester, NY 14627, United States of America.
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9
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Affiliation(s)
- Rebeckah Burke
- Department of Chemistry, University of Rochester, Rochester, New York 14627, USA
| | - Kara L. Bren
- Department of Chemistry, University of Rochester, Rochester, New York 14627, USA
| | - Todd D. Krauss
- Department of Chemistry, University of Rochester, Rochester, New York 14627, USA
- The Institute of Optics, University of Rochester, Rochester, New York 14627, USA
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10
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Affiliation(s)
- Jesse R. Stroka
- Department of Chemistry, University of Rochester, Rochester, New York 14627-0216, United States
| | - Banu Kandemir
- Department of Chemistry, University of Rochester, Rochester, New York 14627-0216, United States
| | - Ellen M. Matson
- 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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11
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Dissanayake DMMM, Petel BE, Brennessel WW, Bren KL, Matson EM. Hydrogen bonding promotes diversity in nitrite coordination modes at a single iron(II) center. J COORD CHEM 2020. [DOI: 10.1080/00958972.2020.1821373] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
| | - Brittney E. Petel
- Department of Chemistry, University of Rochester, Rochester, NY, USA
| | | | - Kara L. Bren
- Department of Chemistry, University of Rochester, Rochester, NY, USA
| | - Ellen M. Matson
- Department of Chemistry, University of Rochester, Rochester, NY, USA
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12
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Edwards EH, Fertig AA, McClelland KP, Meidenbauer MT, Chakraborty S, Krauss TD, Bren KL, Matson EM. Enhancing the activity of photocatalytic hydrogen evolution from CdSe quantum dots with a polyoxovanadate cluster. Chem Commun (Camb) 2020; 56:8762-8765. [PMID: 32628236 DOI: 10.1039/d0cc03163a] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
We report the improvement of photocatalytic proton reduction using molecular polyoxovanadate-alkoxide clusters as hole scavengers for CdSe quantum dots. The increased hydrogen production is explained by favorable charge interactions between reduced forms of the cluster and the charge on the quantum dots arising from the capping ligands.
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Affiliation(s)
- Emily H Edwards
- Department of Chemistry, University of Rochester, Rochester, New York 14627, USA.
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13
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Edwards EH, Bren KL. Light-driven catalysis with engineered enzymes and biomimetic systems. Biotechnol Appl Biochem 2020; 67:463-483. [PMID: 32588914 DOI: 10.1002/bab.1976] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2020] [Accepted: 06/21/2020] [Indexed: 01/01/2023]
Abstract
Efforts to drive catalytic reactions with light, inspired by natural processes like photosynthesis, have a long history and have seen significant recent growth. Successfully engineering systems using biomolecular and bioinspired catalysts to carry out light-driven chemical reactions capitalizes on advantages offered from the fields of biocatalysis and photocatalysis. In particular, driving reactions under mild conditions and in water, in which enzymes are operative, using sunlight as a renewable energy source yield environmentally friendly systems. Furthermore, using enzymes and bioinspired systems can take advantage of the high efficiency and specificity of biocatalysts. There are many challenges to overcome to fully capitalize on the potential of light-driven biocatalysis. In this mini-review, we discuss examples of enzymes and engineered biomolecular catalysts that are activated via electron transfer from a photosensitizer in a photocatalytic system. We place an emphasis on selected forefront chemical reactions of high interest, including CH oxidation, proton reduction, water oxidation, CO2 reduction, and N2 reduction.
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Affiliation(s)
- Emily H Edwards
- Department of Chemistry, University of Rochester, Rochester, NY, USA
| | - Kara L Bren
- Department of Chemistry, University of Rochester, Rochester, NY, USA
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14
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Alvarez-Hernandez JL, Sopchak AE, Bren KL. Buffer pKa Impacts the Mechanism of Hydrogen Evolution Catalyzed by a Cobalt Porphyrin-Peptide. Inorg Chem 2020; 59:8061-8069. [DOI: 10.1021/acs.inorgchem.0c00362] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Affiliation(s)
| | - Andrew E. Sopchak
- 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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15
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Le JM, Alachouzos G, Chino M, Frontier AJ, Lombardi A, Bren KL. Tuning Mechanism through Buffer Dependence of Hydrogen Evolution Catalyzed by a Cobalt Mini-enzyme. Biochemistry 2020; 59:1289-1297. [DOI: 10.1021/acs.biochem.0c00060] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Affiliation(s)
- Jennifer M. Le
- Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
| | - Georgios Alachouzos
- Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
| | - Marco Chino
- Department of Chemical Sciences, University of Naples Federico II, Complesso Universitario Monte S. Angelo, via Cintia 45, 80126 Naples, Italy
| | - Alison J. Frontier
- Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
| | - Angela Lombardi
- Department of Chemical Sciences, University of Naples Federico II, Complesso Universitario Monte S. Angelo, via Cintia 45, 80126 Naples, Italy
| | - Kara L. Bren
- Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
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16
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Chakraborty S, Edwards EH, Kandemir B, Bren KL. Photochemical Hydrogen Evolution from Neutral Water with a Cobalt Metallopeptide Catalyst. Inorg Chem 2019; 58:16402-16410. [DOI: 10.1021/acs.inorgchem.9b02067] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Affiliation(s)
- Saikat Chakraborty
- Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
| | - Emily H. Edwards
- Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
| | - Banu Kandemir
- Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
| | - Kara L. Bren
- Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
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17
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Guo Y, Stroka JR, Kandemir B, Dickerson CE, Bren KL. Cobalt Metallopeptide Electrocatalyst for the Selective Reduction of Nitrite to Ammonium. J Am Chem Soc 2018; 140:16888-16892. [PMID: 30457856 DOI: 10.1021/jacs.8b09612] [Citation(s) in RCA: 46] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
A cobalt-tripeptide complex (CoGGH) is developed as an electrocatalyst for the selective six-electron, eight-proton reduction of nitrite to ammonium in aqueous buffer near neutral pH. The onset potential for nitrite reduction occurs at -0.65 V vs Ag/AgCl (1 M KCl). Controlled potential electrolysis at -0.90 V generates ammonium with a faradaic efficiency of 90 ± 3% and a turnover number of 3550 ± 420 over 5.5 h. CoGGH also catalyzes the reduction of the proposed intermediates nitric oxide and hydroxylamine to ammonium. These results reveal that a simple metallopeptide is an active functional mimic of the complex enzymes cytochrome c nitrite reductase and siroheme-containing nitrite reductase.
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Affiliation(s)
- Yixing Guo
- Department of Chemistry , University of Rochester , Rochester , New York 14627-0216 , United States
| | - Jesse R Stroka
- Department of Chemistry , University of Rochester , Rochester , New York 14627-0216 , United States
| | - Banu Kandemir
- Department of Chemistry , University of Rochester , Rochester , New York 14627-0216 , United States.,Department of Chemistry , Middle East Technical University , North Cyprus via Mersin 10 , Turkey
| | - Claire E Dickerson
- 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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18
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Firpo V, Le JM, Pavone V, Lombardi A, Bren KL. Hydrogen evolution from water catalyzed by cobalt-mimochrome VI*a, a synthetic mini-protein. Chem Sci 2018; 9:8582-8589. [PMID: 30568783 PMCID: PMC6253682 DOI: 10.1039/c8sc01948g] [Citation(s) in RCA: 51] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2018] [Accepted: 09/14/2018] [Indexed: 12/14/2022] Open
Abstract
The folding of a synthetic mini-hydrogenase is shown to enhance catalyst efficiency and longevity.
A synthetic enzyme is reported that electrocatalytically reduces protons to hydrogen (H2) in water near neutral pH under aerobic conditions. Cobalt mimochrome VI*a (CoMC6*a) is a mini-protein with a cobalt deuteroporphyrin active site within a scaffold of two synthetic peptides covalently bound to the porphyrin. Comparison of the activity of CoMC6*a to that of cobalt microperoxidase-11 (CoMP11-Ac), a cobalt porphyrin catalyst with a single “proximal” peptide and no organized secondary structure, reveals that CoMC6*a has significantly enhanced longevity, yielding a turnover number exceeding 230 000, in comparison to 25 000 for CoMP11-Ac. Furthermore, comparison of cyclic voltammograms of CoMC6*a and CoMP11-Ac indicates that the trifluoroethanol-induced folding of CoMC6*a lowers the overpotential for catalytic H2 evolution by up to 100 mV. These results demonstrate that even a minimal polypeptide matrix can enhance longevity and efficiency of a H2-evolution catalyst.
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Affiliation(s)
- Vincenzo Firpo
- Department of Chemical Sciences , University of Naples Federico II , Complesso Universitario Monte S. Angelo , via Cintia 45 , 80126 Naples , Italy .
| | - Jennifer M Le
- Department of Chemistry , University of Rochester , Rochester , NY 14627 , USA .
| | - Vincenzo Pavone
- Department of Chemical Sciences , University of Naples Federico II , Complesso Universitario Monte S. Angelo , via Cintia 45 , 80126 Naples , Italy .
| | - Angela Lombardi
- Department of Chemical Sciences , University of Naples Federico II , Complesso Universitario Monte S. Angelo , via Cintia 45 , 80126 Naples , Italy .
| | - Kara L Bren
- Department of Chemistry , University of Rochester , Rochester , NY 14627 , USA .
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19
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Chen JG, Crooks RM, Seefeldt LC, Bren KL, Bullock RM, Darensbourg MY, Holland PL, Hoffman B, Janik MJ, Jones AK, Kanatzidis MG, King P, Lancaster KM, Lymar SV, Pfromm P, Schneider WF, Schrock RR. Beyond fossil fuel-driven nitrogen transformations. Science 2018; 360:360/6391/eaar6611. [PMID: 29798857 DOI: 10.1126/science.aar6611] [Citation(s) in RCA: 740] [Impact Index Per Article: 123.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Nitrogen is fundamental to all of life and many industrial processes. The interchange of nitrogen oxidation states in the industrial production of ammonia, nitric acid, and other commodity chemicals is largely powered by fossil fuels. A key goal of contemporary research in the field of nitrogen chemistry is to minimize the use of fossil fuels by developing more efficient heterogeneous, homogeneous, photo-, and electrocatalytic processes or by adapting the enzymatic processes underlying the natural nitrogen cycle. These approaches, as well as the challenges involved, are discussed in this Review.
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Affiliation(s)
- Jingguang G Chen
- Department of Chemical Engineering, Columbia University, New York, NY 10027, USA. .,Chemistry Division, Brookhaven National Laboratory, Upton, NY 11973, USA
| | - Richard M Crooks
- Department of Chemistry, The University of Texas at Austin, Austin, TX 78712, USA.
| | - Lance C Seefeldt
- Department of Chemistry and Biochemistry, Utah State University, Logan, UT 84332, USA.
| | - Kara L Bren
- Department of Chemistry, University of Rochester, Rochester, NY 14627, USA
| | | | | | | | - Brian Hoffman
- Department of Chemistry, Northwestern University, Evanston, IL 60208, USA
| | - Michael J Janik
- Department of Chemical Engineering, Pennsylvania State University, University Park, PA 16802, USA
| | - Anne K Jones
- School of Molecular Sciences, Arizona State University, Tempe, AZ 85282, USA
| | | | - Paul King
- National Renewable Energy Laboratory, Golden, CO 80401, USA
| | - Kyle M Lancaster
- Department of Chemistry and Chemical Biology, Cornell University, Baker Laboratory, Ithaca, NY 14853, USA
| | - Sergei V Lymar
- Chemistry Division, Brookhaven National Laboratory, Upton, NY 11973, USA
| | - Peter Pfromm
- Voiland School of Chemical Engineering and Bioengineering, Washington State University, Pullman, WA 99164-6515, USA
| | - William F Schneider
- Department of Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, IN 46556, USA
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20
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Affiliation(s)
- Kara L Bren
- Department of Chemistry, University of Rochester, Rochester, NY 14627, USA.
| | - Emma L Raven
- Department of Chemistry and Leicester Institute of Structural and Chemical Biology, University of Leicester, Leicester LE1 7RH, UK.
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Sgheiza V, Novick B, Stanton S, Pierce J, Kalmeta B, Holmquist MF, Grimaldi K, Bren KL, Michel LV. Covalent bonding of heme to protein prevents heme capture by nontypeable Haemophilus influenzae. FEBS Open Bio 2017; 7:1778-1783. [PMID: 29123985 PMCID: PMC5666386 DOI: 10.1002/2211-5463.12324] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2017] [Revised: 09/15/2017] [Accepted: 09/19/2017] [Indexed: 12/31/2022] Open
Abstract
Nontypeable Haemophilus influenzae (NTHi) are Gram‐negative pathogens that contribute to a variety of diseases, including acute otitis media and chronic obstructive pulmonary disease. As NTHi have an absolute requirement for heme during aerobic growth, these bacteria have to scavenge heme from their human hosts. These heme sources can range from free heme to heme bound to proteins, such as hemoglobin. To test the impact of heme structural factors on heme acquisition by NTHi, we prepared a series of heme sources that systematically vary in heme exposure and covalent binding of heme to peptide/protein and tested the ability of NTHi to use these sources to support growth. Results from this study suggest that NTHi can utilize protein‐associated heme only if it is noncovalently attached to the protein.
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Affiliation(s)
- Valerie Sgheiza
- School of Chemistry and Materials Science Rochester Institute of Technology NY USA
| | - Bethany Novick
- School of Chemistry and Materials Science Rochester Institute of Technology NY USA
| | - Sarah Stanton
- School of Chemistry and Materials Science Rochester Institute of Technology NY USA
| | - Jeanetta Pierce
- School of Chemistry and Materials Science Rochester Institute of Technology NY USA
| | - Breanne Kalmeta
- School of Chemistry and Materials Science Rochester Institute of Technology NY USA
| | | | - Kyle Grimaldi
- School of Chemistry and Materials Science Rochester Institute of Technology NY USA
| | - Kara L Bren
- Department of Chemistry University of Rochester NY USA
| | - Lea Vacca Michel
- School of Chemistry and Materials Science Rochester Institute of Technology NY USA
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Kubie L, Amori AR, Chakraborty S, Bren KL, Krauss TD. Photoinduced charge separation in single-walled carbon nanotube/protein integrated systems. Nanoscale Horiz 2017; 2:163-166. [PMID: 32260660 DOI: 10.1039/c6nh00172f] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Zinc-substituted cytochrome c (Zn-cyt c) is noncovalently bound to single-walled carbon nanotubes (SWNTs), causing the Zn-cyt c fluorescence to be quenched by up to 95%, primarily due to photoinduced charge transfer. Deposition of Zn-cyt c/SWNT films onto conductive oxides allows for harvesting of photoexcited electrons with an internal quantum efficiency of over 5%.
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Affiliation(s)
- Lenore Kubie
- Department of Chemistry, University of Rochester, Rochester, NY 14627, USA.
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24
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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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25
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Affiliation(s)
- Kara L. Bren
- Department of Chemistry University of Rochester Rochester NY 14627-0216 USA
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26
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Kandemir B, Kubie L, Guo Y, Sheldon B, Bren KL. Hydrogen Evolution from Water under Aerobic Conditions Catalyzed by a Cobalt ATCUN Metallopeptide. Inorg Chem 2016; 55:1355-7. [DOI: 10.1021/acs.inorgchem.5b02157] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Affiliation(s)
- Banu Kandemir
- Department
of Chemistry, University of Rochester, Rochester, New York 14627-0216, United States
| | - Lenore Kubie
- Department
of Chemistry, University of Rochester, Rochester, New York 14627-0216, United States
| | - Yixing Guo
- Department
of Chemistry, University of Rochester, Rochester, New York 14627-0216, United States
| | - Brian Sheldon
- 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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27
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Affiliation(s)
- Banu Kandemir
- Department of Chemistry, University of Rochester, Rochester New York 14627-0216, United States
| | - Saikat Chakraborty
- Department of Chemistry, University of Rochester, Rochester New York 14627-0216, United States
| | - Yixing Guo
- 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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28
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Abstract
Hemes are ubiquitous in biology and carry out a wide range of functions. The heme group is largely invariant across proteins with different functions, although there are a few variations seen in nature. The most common variant is heme c, which is formed by a post-translational modification in which heme is covalently linked to two Cys residues on the polypeptide via thioether bonds. In this Account, the influence of this covalent attachment on heme c properties and function is discussed, and examples of how covalent attachment has been used in selected applications are presented. Proteins that bind heme c are among the most well-characterized proteins in biochemistry. Most of these proteins are cytochromes c (cyts c) that serve as electron carriers in photosynthesis and respiration. Despite the intense study of cyts c, the functional significance of heme covalent attachment has remained elusive. One observation is that heme c reaches a lower reduction potential in nature than its noncovalently linked counterpart, heme b, when comparing proteins with the same axial ligands. Furthermore, covalent attachment is known to enhance protein stability and allow the heme to be relatively solvent exposed. However, an inorganic chemistry perspective on the effects of covalent attachment has been lacking. Spectroscopic measurements and computations on cyts c and model systems reveal a number of effects of covalent attachment on heme electronic structure and reactivity. One is that the predominant nonplanar ruffling distortion seen in heme c lowers heme reduction potential. Another is that covalent attachment influences the interaction of the heme iron with the proximal His ligand. Heme ruffling also has been shown to influence electronic coupling to redox partners and, therefore, electron transfer rates by altering the distribution of the orbital hole on the porphyrin in oxidized cyt c. Another consequence of heme covalent attachment is the strong vibrational coupling seen between the iron and the protein surface as revealed by nuclear resonance vibrational spectroscopy studies. Finally, heme covalent attachment is proposed to be an important feature supporting multiple roles of cyt c in programmed cell death (apoptosis). Heme covalent attachment is not only vital for the biological functions of cyt c but also provides a useful handle in a number of applications. For one, the engineering of heme c onto an exposed portion of a protein of interest has been shown to provide a visible affinity purification tag. In addition, peptides with covalently attached heme, known as microperoxidases, have been studied as model compounds and oxidation catalysts and, more recently, in applications for energy conversion and storage. The wealth of insight gained about heme c through fundamental studies of cyts c forms a basis for future efforts toward engineering natural and artificial cytochromes for a variety of applications.
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Affiliation(s)
- Jesse G. Kleingardner
- Department
of Chemistry, Ithaca College, Ithaca, New York 14850, United States
- Department
of Chemistry, University of Rochester, Rochester, New York 14618, United States
| | - Kara L. Bren
- Department
of Chemistry, University of Rochester, Rochester, New York 14618, United States
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Abstract
This review summarizes three different approaches to engineering systems for the solar-driven evolution of hydrogen fuel from water: molecular, nanomaterials and biomolecular. Molecular systems have the advantage of being highly amenable to modification and detailed study and have provided great insight into photophysics, electron transfer and catalytic mechanism. However, they tend to display poor stability. Systems based on nanomaterials are more robust but also are more difficult to synthesize in a controlled manner and to modify and study in detail. Biomolecular systems share many properties with molecular systems and have the advantage of displaying inherently high efficiencies for light absorption, electron-hole separation and catalysis. However, biological systems must be engineered to couple modules that capture and convert solar photons to modules that produce hydrogen fuel. Furthermore, biological systems are prone to degradation when employed in vitro. Advances that use combinations of these three tactics also are described. Multidisciplinary approaches to this problem allow scientists to take advantage of the best features of biological, molecular and nanomaterials systems provided that the components can be coupled for efficient function.
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Affiliation(s)
- Kara L. Bren
- Department of Chemistry, University of Rochester, Rochester, NY 14627-0216, USA
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Galinato MGI, Bowman SEJ, Kleingardner JG, Martin S, Zhao J, Sturhahn W, Alp EE, Bren KL, Lehnert N. Effects of protein structure on iron-polypeptide vibrational dynamic coupling in cytochrome c. Biochemistry 2015; 54:1064-76. [PMID: 25531247 PMCID: PMC4318584 DOI: 10.1021/bi501430z] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Cytochrome c (Cyt c) has a heme covalently bound to the polypeptide via a Cys-X-X-Cys-His (CXXCH) linker that is located in the interface region for protein-protein interactions. To determine whether the polypeptide matrix influences iron vibrational dynamics, nuclear resonance vibrational spectroscopy (NRVS) measurements were performed on (57)Fe-labeled ferric Hydrogenobacter thermophilus cytochrome c-552, and variants M13V, M13V/K22M, and A7F, which have structural modifications that alter the composition or environment of the CXXCH pentapeptide loop. Simulations of the NRVS data indicate that the 150-325 cm(-1) region is dominated by NHis-Fe-SMet axial ligand and polypeptide motions, while the 325-400 cm(-1) region shows dominant contributions from ν(Fe-NPyr) (Pyr = pyrrole) and other heme-based modes. Diagnostic spectral signatures that directly relate to structural features of the heme active site are identified using a quantum chemistry-centered normal coordinate analysis (QCC-NCA). In particular, spectral features that directly correlate with CXXCH loop stiffness, the strength of the Fe-His interaction, and the degree of heme distortion are identified. Cumulative results from our investigation suggest that compared to the wild type (wt), variants M13V and M13V/K22M have a more rigid CXXCH pentapeptide segment, a stronger Fe-NHis interaction, and a more ruffled heme. Conversely, the A7F variant has a more planar heme and a weaker Fe-NHis bond. These results are correlated to the observed changes in reduction potential between wt protein and the variants studied here. Implications of these results for Cyt c biogenesis and electron transfer are also discussed.
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Affiliation(s)
- Mary Grace I Galinato
- Department of Chemistry, University of Michigan , Ann Arbor, Michigan 48109, United States
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31
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Abstract
Direct electrochemical analysis of adsorbed bacterial monoheme cytochromes c has revealed a phenomenological loss of the axial methionine when examined using pyrolytic "edge-plane" graphite (EPG) electrodes. While prior findings have reported that the Met-loss state may be quantitatively understood using the cytochrome c from Hydrogenobacter thermophilus as a model system, here we demonstrate that the formation of the Met-loss state upon EPG electrodes can be observed for a range of cytochrome orthologs. Through an electrochemical comparison of the wild-type proteins from organisms of varying growth temperature optima, we establish that Met-ligand losses at graphite surfaces have similar energetics to the "foldons" for known protein folding pathways. Furthermore, a downward shift in reduction potential to approximately -100 mV vs standard hydrogen electrode was observed, similar to that of the alkaline transition found in mitochondrial cytochromes c. Pourbaix diagrams for the Met-loss forms of each cytochrome, considered here in comparison to mutants where the Met-ligand has been substituted to His or Ala, suggest that the nature of the Met-loss state is distinct from either a His-/aquo- or a bis-His-ligated heme center, yet more closely matches the pKa values found for bis-His-ligated hemes., We find the propensity for adoption of the Met-loss state in bacterial monoheme cytochromes c scales with their overall thermal stability, though not with the specific stability of the Fe-Met bond.
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Affiliation(s)
- Benjamin D Levin
- Department of Chemistry, Boston University , 590 Commonwealth Avenue, Boston, Massachusetts 02215, United States
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Kleingardner JG, Kandemir B, Bren KL. Hydrogen Evolution from Neutral Water under Aerobic Conditions Catalyzed by Cobalt Microperoxidase-11. J Am Chem Soc 2013; 136:4-7. [DOI: 10.1021/ja406818h] [Citation(s) in RCA: 151] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Affiliation(s)
- Jesse G. Kleingardner
- Department
of Chemistry, University of Rochester, Rochester New York 14627-0216, United States
| | - Banu Kandemir
- 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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Kleingardner JG, Bowman SEJ, Bren KL. The influence of heme ruffling on spin densities in ferricytochromes c probed by heme core 13C NMR. Inorg Chem 2013; 52:12933-46. [PMID: 24187968 DOI: 10.1021/ic401250d] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The heme in cytochromes c undergoes a conserved out-of-plane distortion known as ruffling. For cytochromes c from the bacteria Hydrogenobacter thermophilus and Pseudomonas aeruginosa , NMR and EPR spectra have been shown to be sensitive to the extent of heme ruffling and to provide insights into the effect of ruffling on the electronic structure. Through the use of mutants of each of these cytochromes that differ in the amount of heme ruffling, NMR characterization of the low-spin (S = ½) ferric proteins has confirmed and refined the developing understanding of how ruffling influences the spin distribution on heme. The chemical shifts of the core heme carbons were obtained through site-specific labeling of the heme via biosynthetic incorporation of (13)C-labeled 5-aminolevulinic acid derivatives. Analysis of the contact shifts of these core heme carbons allowed Fermi contact spin densities to be estimated and changes upon ruffling to be evaluated. The results allow a deconvolution of the contributions to heme hyperfine shifts and a test of the influence of heme ruffling on the electronic structure and hyperfine shifts. The data indicate that as heme ruffling increases, the spin densities on the β-pyrrole carbons decrease while the spin densities on the α-pyrrole carbons and meso carbons increase. Furthermore, increased ruffling is associated with stronger bonding to the heme axial His ligand.
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Affiliation(s)
- Jesse G Kleingardner
- Department of Chemistry, University of Rochester , Rochester, New York 14627-0216, United States
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34
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Abstract
Analysis of NMR spectra reveals that the heme axial Met ligand orientation and dynamics in Nitrosomonas europaea cytochrome c552 (Ne cyt c) are dependent on the heme redox state. In the oxidized state, the heme axial Met is fluxional, interconverting between two conformers related to each other by inversion through the Met δS atom. In the reduced state, there is no evidence of fluxionality, with the Met occupying one conformation similar to that seen in the homologous Pseudomonas aeruginosa cytochrome c551. Comparison of the observed and calculated pseudocontact shifts for oxidized Ne cyt c using the reduced protein structure as a reference structure reveals a redox-dependent change in the structure of the loop bearing the axial Met (loop 3). Analysis of nuclear Overhauser effects (NOEs) and existing structural data provides further support for the redox state dependence of the loop 3 structure. Implications for electron transfer function are discussed.
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Affiliation(s)
- Ravinder Kaur
- Center for Infectious Disease and Immunology, Research Institute, Rochester General Hospital , Rochester, New York 14621, United States
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35
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Lee AJ, Asher WB, Stern HA, Bren KL, Krauss TD. Single-Molecule Analysis of Cytochrome c Folding by Monitoring the Lifetime of an Attached Fluorescent Probe. J Phys Chem Lett 2013; 4:2727-2733. [PMID: 24116268 PMCID: PMC3791595 DOI: 10.1021/jz401259y] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Conformational dynamics of proteins are important for function. However, obtaining information about specific conformations is difficult for samples displaying heterogeneity. Here, time-resolved fluorescence resonance energy transfer is used to characterize the folding of single cytochrome c molecules. In particular, measurements of the fluorescence lifetimes of individual cytochrome c molecules labeled with a single dye that is quenched by energy transfer to the heme were used to monitor conformational transitions of the protein under partially denaturing conditions. These studies indicate significantly more conformational heterogeneity than has been described previously. Importantly, the use of a purified singly-labeled sample made a direct comparison to ensemble data possible. The distribution of lifetimes of single-proteins was compared to the distribution of lifetimes determined from analysis of ensemble lifetime fluorescence data. The results show broad agreement between single-molecule and ensemble data, with a similar range of lifetimes. However, the single-molecule data reveal greater conformational heterogeneity.
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36
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Can M, Krucinska J, Zoppellaro G, Andersen NH, Wedekind JE, Hersleth HP, Andersson KK, Bren KL. Structural characterization of nitrosomonas europaea cytochrome c-552 variants with marked differences in electronic structure. Chembiochem 2013; 14:1828-38. [PMID: 23908017 DOI: 10.1002/cbic.201300118] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2013] [Indexed: 11/09/2022]
Abstract
Nitrosomonas europaea cytochrome c-552 (Ne c-552) variants with the same His/Met axial ligand set but with different EPR spectra have been characterized structurally, to aid understanding of how molecular structure determines heme electronic structure. Visible light absorption, Raman, and resonance Raman spectroscopy of the protein crystals was performed along with structure determination. The structures solved are those of Ne c-552, which displays a "HALS" (or highly anisotropic low-spin) EPR spectrum, and of the deletion mutant Ne N64Δ, which has a rhombic EPR spectrum. Two X-ray crystal structures of wild-type Ne c-552 are reported; one is of the protein isolated from N. europaea cells (Ne c-552n, 2.35 Å resolution), and the other is of recombinant protein expressed in Escherichia coli (Ne c-552r, 1.63 Å resolution). Ne N64Δ crystallized in two different space groups, and two structures are reported [monoclinic (2.1 Å resolution) and hexagonal (2.3 Å resolution)]. Comparison of the structures of the wild-type and mutant proteins reveals that heme ruffling is increased in the mutant; increased ruffling is predicted to yield a more rhombic EPR spectrum. The 2.35 Å Ne c-552n structure shows 18 molecules in the asymmetric unit; analysis of the structure is consistent with population of more than one axial Met configuration, as seen previously by NMR. Finally, the mutation was shown to yield a more hydrophobic heme pocket and to expel water molecules from near the axial Met. These structures reveal that heme pocket residue 64 plays multiple roles in regulating the axial ligand orientation and the interaction of water with the heme. These results support the hypothesis that more ruffled hemes lead to more rhombic EPR signals in cytochromes c with His/Met axial ligation.
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Affiliation(s)
- Mehmet Can
- Department of Chemistry, University of Rochester, Rochester, NY 14627 (USA)
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37
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Novick BR, Sgheiza V, Frink M, Kalmeta B, Grimaldi K, Bren KL, Vacca‐Michel L. Probing the biological significance of c‐heme attachment in cytochrome c. FASEB J 2013. [DOI: 10.1096/fasebj.27.1_supplement.790.6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Bethany Rose Novick
- School of Chemistry and Materials ScienceRochester Institute of TechnologyRochesterNY
| | - Valerie Sgheiza
- School of Chemistry and Materials ScienceRochester Institute of TechnologyRochesterNY
| | - Melody Frink
- School of Chemistry and Materials ScienceRochester Institute of TechnologyRochesterNY
| | - Breanna Kalmeta
- School of Chemistry and Materials ScienceRochester Institute of TechnologyRochesterNY
| | - Kyle Grimaldi
- School of Chemistry and Materials ScienceRochester Institute of TechnologyRochesterNY
| | - Kara L. Bren
- Department of ChemistryUniversity of RochesterRochesterNY
| | - Lea Vacca‐Michel
- School of Chemistry and Materials ScienceRochester Institute of TechnologyRochesterNY
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38
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Asher WB, Bren KL. Cytochrome c heme lyase can mature a fusion peptide composed of the amino-terminal residues of horse cytochrome c. Chem Commun (Camb) 2012; 48:8344-6. [PMID: 22792539 DOI: 10.1039/c2cc31112g] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
It is shown that cytochrome c heme lyase (CCHL) attaches heme covalently to peptides composed of the N-terminal segment of cyt c fused to a non-heme containing protein, lending insight into the substrate specificity of CCHL and providing a new route to artificial heme proteins.
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Affiliation(s)
- Wesley B Asher
- Department of Chemistry, University of Rochester, Rochester, New York 14627-0216, USA
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39
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Kalmeta B, Grimaldi K, Iqbal A, Weekes D, Bren KL, Michel LV. Using NTHi growth studies to demonstrate the biological significance of c‐heme covalent attachment. FASEB J 2012. [DOI: 10.1096/fasebj.26.1_supplement.581.1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Breanna Kalmeta
- Department of ChemistryRochester Institute of TechnologyRochesterNY
| | - Kyle Grimaldi
- Department of ChemistryRochester Institute of TechnologyRochesterNY
| | - Arooj Iqbal
- Department of ChemistryRochester Institute of TechnologyRochesterNY
| | - Danielle Weekes
- Department of ChemistryRochester Institute of TechnologyRochesterNY
| | - Kara L Bren
- Department of ChemistryUniversity of RochesterRochesterNY
| | - Lea Vacca Michel
- Department of ChemistryRochester Institute of TechnologyRochesterNY
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Can M, Zoppellaro G, Andersson KK, Bren KL. Modulation of ligand-field parameters by heme ruffling in cytochromes c revealed by EPR spectroscopy. Inorg Chem 2011; 50:12018-24. [PMID: 22044358 DOI: 10.1021/ic201479q] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Electron paramagnetic resonance (EPR) spectra of variants of Hydrogenobacter thermophilus cytochrome c(552) (Ht c-552) and Pseudomonas aeruginosa cytochrome c(551) (Pa c-551) are analyzed to determine the effect of heme ruffling on ligand-field parameters. Mutations introduced at positions 13 and 22 in Ht c-552 were previously demonstrated to influence hydrogen bonding in the proximal heme pocket and to tune reduction potential (E(m)) over a range of 80 mV [Michel, L. V.; Ye, T.; Bowman, S. E. J.; Levin, B. D.; Hahn, M. A.; Russell, B. S.; Elliott, S. J.; Bren, K. L. Biochemistry 2007, 46, 11753-11760]. These mutations are shown here to also increase heme ruffling as E(m) decreases. The primary effect on electronic structure of increasing heme ruffling is found to be a decrease in the axial ligand-field term Δ/λ, which is proposed to arise from an increase in the energy of the d(xy) orbital. Mutations at position 7, previously demonstrated to influence heme ruffling in Pa c-551 and Ht c-552, are utilized to test this correlation between molecular and electronic structure. In conclusion, the structure of the proximal heme pocket of cytochromes c is shown to play a role in determining heme conformation and electronic structure.
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Affiliation(s)
- Mehmet Can
- Department of Chemistry, University of Rochester, Rochester, New York 14627-0216, USA
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41
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Levin BD, Can M, Bowman SEJ, Bren KL, Elliott SJ. Methionine ligand lability in bacterial monoheme cytochromes c: an electrochemical study. J Phys Chem B 2011; 115:11718-26. [PMID: 21870858 DOI: 10.1021/jp203292h] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The direct electrochemical analysis of adsorbed redox active proteins has proven to be a powerful technique in biophysical chemistry, frequently making use of the electrode material pyrolytic "edge-plane" graphite. However, many heme-bearing proteins such as cytochromes c have been also examined systematically at alkanethiol-modified gold surfaces, and previously we reported the characterization of the redox properties of a series of bacterial cytochromes c in a side-by-side comparison of carbon and gold electrode materials. In our prior findings, we reported an unanticipated, low potential (E(m) ∼ -100 mV vs SHE) redox couple that could be analogously observed when a variety of monoheme cytochromes c are adsorbed onto carbon-based electrodes. Here we demonstrate that our prior phenomological data can be understood quantitatively in the loss of the methionine ligand of the heme iron, using the cytochrome c from Hydrogenbacter thermophilum as a model system. Through the comparison of wild-type protein with M61H and M61A mutants, in direct electrochemical analyses conducted as a function of temperature and exogenous ligand concentration, we are able to show that Met-ligated cytochromes c have a propensity to lose their Met ligand at graphite surfaces, and that energetics of this process (6.3 ± 0.2 kJ/mol) is similar to the energies associated with "foldons" of known protein folding pathways.
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Affiliation(s)
- Benjamin D Levin
- Department of Chemistry, Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215, United States
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Chung JK, Thielges MC, Bowman SEJ, Bren KL, Fayer MD. Temperature dependent equilibrium native to unfolded protein dynamics and properties observed with IR absorption and 2D IR vibrational echo experiments. J Am Chem Soc 2011; 133:6681-91. [PMID: 21469666 PMCID: PMC3088310 DOI: 10.1021/ja111009s] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Dynamic and structural properties of carbonmonoxy (CO)-coordinated cytochrome c(552) from Hydrogenobacter thermophilus (Ht-M61A) at different temperatures under thermal equilibrium conditions were studied with infrared absorption spectroscopy and ultrafast two-dimensional infrared (2D IR) vibrational echo experiments using the heme-bound CO as the vibrational probe. Depending on the temperature, the stretching mode of CO shows two distinct bands corresponding to the native and unfolded proteins. As the temperature is increased from low temperature, a new absorption band for the unfolded protein grows in and the native band decreases in amplitude. Both the temperature-dependent circular dichroism and the IR absorption area ratio R(A)(T), defined as the ratio of the area under the unfolded band to the sum of the areas of the native and unfolded bands, suggest a two-state transition from the native to the unfolded protein. However, it is found that the absorption spectrum of the unfolded protein increases its inhomogeneous line width and the center frequency shifts as the temperature is increased. The changes in line width and center frequency demonstrate that the unfolding does not follow simple two-state behavior. The temperature-dependent 2D IR vibrational echo experiments show that the fast dynamics of the native protein are virtually temperature independent. In contrast, the fast dynamics of the unfolded protein are slower than those of the native protein, and the unfolded protein fast dynamics and at least a portion of the slower dynamics of the unfolded protein change significantly, becoming faster as the temperature is raised. The temperature dependence of the absorption spectrum and the changes in dynamics measured with the 2D IR experiments confirm that the unfolded ensemble of conformers continuously changes its nature as unfolding proceeds, in contrast to the native state, which displays a temperature-independent distribution of structures.
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Affiliation(s)
- Jean K. Chung
- Department of Chemistry, Stanford University, Stanford, California 94305
| | - Megan C. Thielges
- Department of Chemistry, Stanford University, Stanford, California 94305
| | - Sarah E. J. Bowman
- Department of Chemistry, University of Rochester, Rochester, New York 14627
| | - Kara L. Bren
- Department of Chemistry, University of Rochester, Rochester, New York 14627
| | - M. D. Fayer
- Department of Chemistry, Stanford University, Stanford, California 94305
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Kleingardner JG, Bren KL. Comparing substrate specificity between cytochrome c maturation and cytochrome c heme lyase systems for cytochrome c biogenesis. Metallomics 2011; 3:396-403. [PMID: 21380436 PMCID: PMC3081496 DOI: 10.1039/c0mt00086h] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Hemes c are characterized by their covalent attachment to a polypeptide via a widely conserved CXXCH motif. There are multiple biological systems that facilitate heme c biogenesis. System I, the cytochrome c maturation (CCM) system, is found in many bacteria and is commonly employed in the maturation of bacterial cytochromes c in Escherichia coli-based expression systems. System III, cytochrome c heme lyase (CCHL), is an enzyme found in the mitochondria of many eukaryotes and is used for heterologous expression of mitochondrial holocytochromes c. To test CCM specificity, a series of Hydrogenobacter thermophilus cytochrome c(552) variants was successfully expressed and matured by the CCM system with CX(n)CH motifs where n = 1-4, further extending the known substrate flexibility of the CCM system by successful maturation of a bacterial cytochrome c with a novel CXCH motif. Horse cytochrome c variants with both expanded and contracted attachment motifs (n = 1-3) were also tested for expression and maturation by both CCM and CCHL, allowing direct comparison of CCM and CCHL substrate specificities. Successful maturation of horse cytochrome c by CCHL with an extended CXXXCH motif was observed, demonstrating that CCHL shares the ability of CCM to mature hemes c with extended heme attachment motifs. In contrast, two single amino acid mutants were found in horse cytochrome c that severely limit maturation by CCHL, yet were efficiently matured with CCM. These results identify potentially important residues for the substrate recognition of CCHL.
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Liptak MD, Fagerlund RD, Ledgerwood EC, Wilbanks SM, Bren KL. The proapoptotic G41S mutation to human cytochrome c alters the heme electronic structure and increases the electron self-exchange rate. J Am Chem Soc 2010; 133:1153-5. [PMID: 21192676 DOI: 10.1021/ja106328k] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The naturally occurring G41S mutation to human (Hs) cytochrome (cyt) c enhances apoptotic activity based upon previous in vitro and in vivo studies, but the molecular mechanism underlying this enhancement remains unknown. Here, X-ray crystallography, nuclear magnetic resonance (NMR) spectroscopy, and density functional theory (DFT) calculations have been used to identify the structural and electronic differences between wild-type (WT) and G41S Hs cyt c. S41 is part of the hydrogen bonding network for propionate 7 of heme pyrrole ring A in the X-ray structure of G41S Hs cyt c and, compared to WT, G41S Hs cyt c has increased spin density on pyrrole ring C and a faster electron self-exchange rate. DFT calculations illustrate an electronic mechanism where structural changes near ring A can result in electronic changes at ring C. Since ring C is part of the solvent-exposed protein surface, we propose that this heme electronic structure change may ultimately be responsible for the enhanced proapoptotic activity of G41S Hs cyt c.
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Affiliation(s)
- Matthew D Liptak
- Department of Chemistry, University of Rochester, Rochester, New York 14627, United States
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Abstract
Out-of-plane (OOP) deformations of the heme cofactor are found in numerous heme-containing proteins and the type of deformation tends to be conserved within functionally related classes of heme proteins. We demonstrate correlations between the heme ruffling OOP deformation and the (13)C and (1)H nuclear magnetic resonance (NMR) hyperfine shifts of heme aided by density functional theory (DFT) calculations. The degree of ruffling in the heme cofactor of Hydrogenobacter thermophilus cytochrome c(552) has been modified by a single amino acid mutation in the second coordination sphere of the cofactor. The (13)C and (1)H resonances of the cofactor have been assigned using one- and two-dimensional NMR spectroscopy aided by selective (13)C-enrichment of the heme. DFT has been used to predict the NMR hyperfine shifts and electron paramagnetic resonance (EPR) g-tensor at several points along the ruffling deformation coordinate. The DFT-predicted NMR and EPR parameters agree with the experimental observations, confirming that an accurate theoretical model of the electronic structure and its response to ruffling has been established. As the degree of ruffling increases, the heme methyl (1)H resonances move upfield while the heme methyl and meso (13)C resonances move downfield. These changes are a consequence of altered overlap of the Fe 3d and porphyrin pi orbitals, which destabilizes all three occupied Fe 3d-based molecular orbitals and decreases the positive and negative spin density on the beta-pyrrole and meso carbons, respectively. Consequently, the heme ruffling deformation decreases the electronic coupling of the cofactor with external redox partners and lowers the reduction potential of heme.
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Affiliation(s)
- Matthew D Liptak
- Department of Chemistry, University of Rochester, Rochester, New York 14627-0216, USA
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Asher WB, Bren KL. A heme fusion tag for protein affinity purification and quantification. Protein Sci 2010; 19:1830-9. [PMID: 20665691 PMCID: PMC2998719 DOI: 10.1002/pro.460] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2010] [Revised: 07/07/2010] [Accepted: 07/09/2010] [Indexed: 11/10/2022]
Abstract
We report a novel affinity-based purification method for proteins expressed in Escherichia coli that uses the coordination of a heme tag to an L-histidine-immobilized sepharose (HIS) resin. This approach provides an affinity purification tag visible to the eye, facilitating tracking of the protein. We show that azurin and maltose binding protein are readily purified from cell lysate using the heme tag and HIS resin. Mild conditions are used; heme-tagged proteins are bound to the HIS resin in phosphate buffer, pH 7.0, and eluted by adding 200-500 mM imidazole or binding buffer at pH 5 or 8. The HIS resin exhibits a low level of nonspecific binding of untagged cellular proteins for the systems studied here. An additional advantage of the heme tag-HIS method for purification is that the heme tag can be used for protein quantification by using the pyridine hemochrome absorbance method for heme concentration determination.
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Affiliation(s)
| | - Kara L Bren
- Department of Chemistry, University of RochesterRochester, New York 14627-0216
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Abstract
The electron-donating properties of the axial His ligand to heme iron in cytochromes c (cyts c) are found to be correlated with the midpoint reduction potential (E(m)) in variants of Hydrogenobacter thermophilus cytochrome c(552) (Ht cyt c(552)) in which mutations have been made in and near the Cys-X-X-Cys-His (CXXCH) heme-binding motif. To probe the strength of the His-Fe(III) interaction, we have measured (13)C nuclear magnetic resonance (NMR) chemical shifts for (13)CN(-) bound to heme iron trans to the axial His in Ht Fe(III) cyt c(552) variants. We observe a linear relationship between these (13)C chemical shifts and E(m), indicating that the His-Fe(III) bond strength correlates with E(m). To probe a conserved hydrogen bonding interaction between the axial His Hdelta1 and the backbone carbonyl of a Pro residue, we measured the pK(a) of the axial His Hdelta1 proton (pK(a(2))), which we propose to relate to the His-Fe(III) interaction, reduction potential, and local electrostatic effects. The observed linear relationship between the axial His (13)Cbeta chemical shift and E(m) is proposed to reflect histidinate (anionic) character of the ligand. A linear relationship also is seen between the average heme methyl (1)H chemical shift and E(m) which may reflect variation in axial His electron-donating properties or in the ruffling distortion of the heme plane. In summary, chemical shifts of the axial His and exogenous CN(-) bound trans to His are shown to be sensitive probes of the His-Fe(III) interaction in variants of Ht cyt c(552) and display trends that correlate with E(m).
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Affiliation(s)
- Sarah E. J. Bowman
- Department of Chemistry, University of Rochester, Rochester, New York 14627-0216
| | - Kara L. Bren
- Department of Chemistry, University of Rochester, Rochester, New York 14627-0216
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Abstract
We demonstrate that Zn(II) porphyrin in Zn(II)cytochrome c (Zn cyt c) is a fluorescence resonance energy transfer (FRET) donor to an Alexa660 dye acceptor. The energy transfer efficiency is dependent on the distance between the two fluorophores as shown through protein denaturation studies of five Zn cyt c variants labeled with Alexa660 in different positions. The relative quantum yield, excitation and emission energies, and labeling efficiencies of this donor-acceptor pair allow for a method of analysis based on sensitized emission of the acceptor. These studies show that Zn(II) porphyrin is an effective energy donor for measurement of molecular-scale distances by FRET.
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Affiliation(s)
- Andrea J Lee
- Department of Chemistry, University of Rochester, Rochester, New York 14627, USA
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Zoppellaro G, Bren KL, Ensign AA, Harbitz E, Kaur R, Hersleth HP, Ryde U, Hederstedt L, Andersson KK. Review: studies of ferric heme proteins with highly anisotropic/highly axial low spin (S = 1/2) electron paramagnetic resonance signals with bis-histidine and histidine-methionine axial iron coordination. Biopolymers 2009; 91:1064-82. [PMID: 19536822 PMCID: PMC2852197 DOI: 10.1002/bip.21267] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Six-coordinated heme groups are involved in a large variety of electron transfer reactions because of their ability to exist in both the ferrous (Fe(2+)) and ferric (Fe(3+)) state without any large differences in structure. Our studies on hemes coordinated by two histidines (bis-His) and hemes coordinated by histidine and methionine (His-Met) will be reviewed. In both of these coordination environments, the heme core can exhibit ferric low spin (electron paramagnetic resonance EPR) signals with large g(max) values (also called Type I, highly anisotropic low spin, or highly axial low spin, HALS species) as well as rhombic EPR (Type II) signals. In bis-His coordinated hemes rhombic and HALS envelopes are related to the orientation of the His groups with respect to each other such that (i) parallel His planes results in a rhombic signal and (ii) perpendicular His planes results in a HALS signal. Correlation between the structure of the heme and its ligands for heme with His-Met axial ligation and ligand-field parameters, as derived from a large series of cytochrome c variants, show, however, that for such a combination of axial ligands there is no clear-cut difference between the large g(max) and the "small g-anisotropy" cases as a result of the relative Met-His arrangements. Nonetheless, a new linear correlation links the average shift delta of the heme methyl groups with the g(max) values.
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Affiliation(s)
- Giorgio Zoppellaro
- Department of Molecular Biosciences, University of Oslo, PO Box 1041 Blindern, Oslo NO–0316, Norway
| | - Kara L. Bren
- Department of Chemistry, University of Rochester, Rochester, New York 146270216, USA
| | - Amy A. Ensign
- Department of Chemistry, University of Rochester, Rochester, New York 146270216, USA
| | - Espen Harbitz
- Department of Molecular Biosciences, University of Oslo, PO Box 1041 Blindern, Oslo NO–0316, Norway
| | - Ravinder Kaur
- Department of Chemistry, University of Rochester, Rochester, New York 146270216, USA
| | - Hans-Petter Hersleth
- Department of Molecular Biosciences, University of Oslo, PO Box 1041 Blindern, Oslo NO–0316, Norway
| | - Ulf Ryde
- Department Theoretical Chemistry, Lund University, Chemical Centre, P. O. Box 124, SE–221 00 Lund, Sweden
| | - Lars Hederstedt
- Department of Cell & Organism Biology, Lund University, Sölvegatan 35, SE–22362 Lund, Sweden
| | - K. Kristoffer Andersson
- Department of Molecular Biosciences, University of Oslo, PO Box 1041 Blindern, Oslo NO–0316, Norway
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Zoppellaro G, Harbitz E, Kaur R, Ensign AA, Bren KL, Andersson KK. Modulation of the ligand-field anisotropy in a series of ferric low-spin cytochrome c mutants derived from Pseudomonas aeruginosa cytochrome c-551 and Nitrosomonas europaea cytochrome c-552: a nuclear magnetic resonance and electron paramagnetic resonance study. J Am Chem Soc 2008; 130:15348-60. [PMID: 18947229 PMCID: PMC2664661 DOI: 10.1021/ja8033312] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Cytochromes of the c type with histidine-methionine (His-Met) heme axial ligation play important roles in electron-transfer reactions and in enzymes. In this work, two series of cytochrome c mutants derived from Pseudomonas aeruginosa (Pa c-551) and from the ammonia-oxidizing bacterium Nitrosomonas europaea (Ne c-552) were engineered and overexpressed. In these proteins, point mutations were induced in a key residue (Asn64) near the Met axial ligand; these mutations have a considerable impact both on heme ligand-field strength and on the Met orientation and dynamics (fluxionality), as judged by low-temperature electron paramagnetic resonance (EPR) and nuclear magnetic resonance (NMR) spectra. Ne c-552 has a ferric low-spin (S = 1/2) EPR signal characterized by large g anisotropy with g(max) resonance at 3.34; a similar large g(max) value EPR signal is found in the mitochondrial complex III cytochrome c1. In Ne c-552, deletion of Asn64 (NeN64Delta) changes the heme ligand field from more axial to rhombic (small g anisotropy and g(max) at 3.13) and furthermore hinders the Met fluxionality present in the wild-type protein. In Pa c-551 (g(max) at 3.20), replacement of Asn64 with valine (PaN64V) induces a decrease in the axial strain (g(max) at 3.05) and changes the Met configuration. Another set of mutants prepared by insertion (ins) and/or deletion (Delta) of a valine residue adjacent to Asn64, resulting in modifications in the length of the axial Met-donating loop (NeV65Delta, NeG50N/V65Delta, PaN50G/V65ins), did not result in appreciable alterations of the originally weak (Ne c-552) or very weak (Pa c-551) axial field but had an impact on Met orientation, fluxionality, and relaxation dynamics. Comparison of the electronic fingerprints in the overexpressed proteins and their mutants reveals a linear relationship between axial strain and average paramagnetic heme methyl shifts, irrespective of Met orientation or dynamics. Thus, for these His-Met axially coordinated Fe(III), the large g(max) value EPR signal does not represent a special case as is observed for bis-His axially coordinated Fe(III) with the two His planes perpendicular to each other.
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Affiliation(s)
- Giorgio Zoppellaro
- Department of Molecular Biosciences, University of Oslo, Post Office Box 1041 Blindern, Oslo NO-0316, Norway
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