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Koone J, Simmang M, Saenger DL, Hunsicker-Wang LM, Shaw BF. Charge Regulation in a Rieske Proton Pump Pinpoints Zero, One, and Two Proton-Coupled Electron Transfer. J Am Chem Soc 2023; 145:16488-16497. [PMID: 37486967 PMCID: PMC10402712 DOI: 10.1021/jacs.3c03006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2023] [Indexed: 07/26/2023]
Abstract
The degree to which redox-driven proton pumps regulate net charge during electron transfer (ΔZET) remains undetermined due to difficulties in measuring the net charge of solvated proteins. Values of ΔZET can reflect reorganization energies or redox potentials associated with ET and can be used to distinguish ET from proton(s)-coupled electron transfer (PCET). Here, we synthesized protein "charge ladders" of a Rieske [2Fe-2S] subunit from Thermus thermophilus (truncTtRp) and made 120 electrostatic measurements of ΔZET across pH. Across pH 5-10, truncTtRp is suspected of transitioning from ET to PCET, and then to two proton-coupled ET (2PCET). Upon reduction, we found that truncTtRp became more negative at pH 6.0 by one unit (ΔZET = -1.01 ± 0.14), consistent with single ET; was isoelectric at pH 8.8 (ΔZET = -0.01 ± 0.45), consistent with PCET; and became more positive at pH 10.6 (ΔZET = +1.37 ± 0.60), consistent with 2PCET. These ΔZET values are attributed to protonation of H154 and H134. Across pH, redox potentials of TtRp (measured previously) correlated with protonation energies of H154 and H134 and ΔZET for truncTtRp, supporting a discrete proton pumping mechanism for Rieske proteins at the Fe-coordinating histidines.
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Affiliation(s)
- Jordan
C. Koone
- Department
of Chemistry and Biochemistry, Baylor University, Waco, Texas 76706, United States
| | - Mikaela Simmang
- Department
of Chemistry, Trinity University, San Antonio, Texas 78212, United States
| | - Devin L. Saenger
- Department
of Chemistry, Trinity University, San Antonio, Texas 78212, United States
| | | | - Bryan F. Shaw
- Department
of Chemistry and Biochemistry, Baylor University, Waco, Texas 76706, United States
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Devlin T, Hofman CR, Acevedo ZPV, Kohler KR, Tao L, Britt RD, Hoke KR, Hunsicker-Wang LM. DEPC modification of the Cu A protein from Thermus thermophilus. J Biol Inorg Chem 2018; 24:117-135. [PMID: 30523412 DOI: 10.1007/s00775-018-1632-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2018] [Accepted: 11/28/2018] [Indexed: 11/28/2022]
Abstract
The CuA center is the initial electron acceptor in cytochrome c oxidase, and it consists of two copper ions bridged by two cysteines and ligated by two histidines, a methionine, and a carbonyl in the peptide backbone of a nearby glutamine. The two ligating histidines are of particular interest as they may influence the electronic and redox properties of the metal center. To test for the presence of reactive ligating histidines, a portion of cytochrome c oxidase from the bacteria Thermus thermophilus that contains the CuA site (the TtCuA protein) was treated with the chemical modifier diethyl pyrocarbonate (DEPC) and the reaction followed through UV-visible, circular dichroism, and electron paramagnetic resonance spectroscopies at pH 5.0-9.0. A mutant protein (H40A/H117A) with the non-ligating histidines removed was similarly tested. Introduction of an electron-withdrawing DEPC-modification onto the ligating histidine 157 of TtCuA increased the reduction potential by over 70 mV, as assessed by cyclic voltammetry. Results from both proteins indicate that DEPC reacts with one of the two ligating histidines, modification of a ligating histidine raises the reduction potential of the CuA site, and formation of the DEPC adduct is reversible at room temperature. The existence of the reactive ligating histidine suggests that this residue may play a role in modulating the electronic and redox properties of TtCuA through kinetically-controlled proton exchange with the solvent. Lack of reactivity by the metalloproteins Sco and azurin, both of which contain a mononuclear copper center, indicate that reactivity toward DEPC is not a characteristic of all ligating histidines.
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Affiliation(s)
- Taylor Devlin
- Department of Chemistry, Trinity University, San Antonio, TX, 78212-7200, USA
- Department of Biophysics, Johns Hopkins University, 3400 N. Charles Street, Baltimore, MD, 21218, USA
| | - Cristina R Hofman
- Department of Chemistry, Trinity University, San Antonio, TX, 78212-7200, USA
| | - Zachary P V Acevedo
- Department of Chemistry, Trinity University, San Antonio, TX, 78212-7200, USA
| | - Kelsey R Kohler
- Department of Chemistry, Trinity University, San Antonio, TX, 78212-7200, USA
| | - Lizhi Tao
- Department of Chemistry, University of California at Davis, Davis, CA, 95616, USA
| | - R David Britt
- Department of Chemistry, University of California at Davis, Davis, CA, 95616, USA
| | - Kevin R Hoke
- Department of Chemistry and Biochemistry, Berry College, Mount Berry, GA, 30149, USA
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Deyu H, Luqing C, Xianglian L, Pu G, Qirong L, Xu W, Zonghui Y. Protective mechanisms involving enhanced mitochondrial functions and mitophagy against T-2 toxin-induced toxicities in GH3 cells. Toxicol Lett 2018; 295:41-53. [PMID: 29870751 DOI: 10.1016/j.toxlet.2018.05.041] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2018] [Revised: 05/29/2018] [Accepted: 05/31/2018] [Indexed: 12/21/2022]
Abstract
T-2 toxin is the most toxic member of trichothecene mycotoxin. So far, the mechanism of mitochondrial toxicity and protective mechanism in mammalian cells against T-2 toxin are not fully understood. In this study, we aimed to investigate the cellular and mitochondrial toxicity of T-2 toxin, and the cellular protective mechanisms in rat pituitary GH3 cells. We showed that T-2 toxin significantly increased reactive oxygen species (ROS) and DNA damage and caused apoptosis in GH3 cells. T-2 toxin induced abnormal cell morphology, cytoplasm and nuclear shrinkage, nuclear fragmentation and formation of apoptotic bodies and autophagosomes. The mitochondrial degradative morphologies included local or total cristae collapse and small condensed mitochondria. T-2 toxin decreased the mitochondrial membrane potential. However, T-2 toxin significantly increased the superoxide dismutase (SOD) activity and expression of antioxidant genes glutathione peroxidase 1 (GPx-1), catalase (CAT), mitochondria-specific SOD-2 and mitochondrial uncoupling protein-1, -2 and -3 (UCP-1, 2 and 3). Interestingly, T-2 toxin increased adenosine triphosphate (ATP) levels and mitochondrial complex I activity, and increased the expression of most of mitochondrial electron transport chain subunits tested and critical transcription factors controlling mitochondrial biogenesis and mitochondrial DNA transcription and replication. T-2 toxin increased mitophagic activity by increasing the expression of mitophagy-specific proteins NIP-like protein X (NIX), PTEN-induced putative kinase protein 1 (PINK1) and E3 ubiquitin ligase Parkin. T-2 toxin activated the protective protein kinase A (PKA) signaling pathway, which activated the nuclear factor (erythroid-derived 2)-like 2 (Nrf2)/PINK1/Parkin pathway to mediate mitophagy. Taken together, our results suggested that the mammalian cells could increase their resistance against T-2 toxin by increasing the antioxidant activity, mitophagy and mitochondrial function.
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Affiliation(s)
- Huang Deyu
- Department of Animal Sciences & Technology, Key Laboratory for the Detection of Veterinary Drug Residues, Huazhong Agricultural University, Wuhan, Hubei, 430070, China
| | - Cui Luqing
- Department of Animal Sciences & Technology, Laboratory of Quality & Safety Risk Assessment for Livestock and Poultry Products, Huazhong Agricultural University, Wuhan, Hubei, 430070, China
| | - Liu Xianglian
- Department of Animal Sciences & Technology, Laboratory of Quality & Safety Risk Assessment for Livestock and Poultry Products, Huazhong Agricultural University, Wuhan, Hubei, 430070, China
| | - Guo Pu
- Department of Animal Sciences & Technology, Laboratory of Quality & Safety Risk Assessment for Livestock and Poultry Products, Huazhong Agricultural University, Wuhan, Hubei, 430070, China
| | - Lu Qirong
- Department of Animal Sciences & Technology, Laboratory of Quality & Safety Risk Assessment for Livestock and Poultry Products, Huazhong Agricultural University, Wuhan, Hubei, 430070, China
| | - Wang Xu
- Department of Animal Sciences & Technology, Key Laboratory for the Detection of Veterinary Drug Residues, Huazhong Agricultural University, Wuhan, Hubei, 430070, China; Department of Animal Sciences & Technology, Laboratory of Quality & Safety Risk Assessment for Livestock and Poultry Products, Huazhong Agricultural University, Wuhan, Hubei, 430070, China.
| | - Yuan Zonghui
- Department of Animal Sciences & Technology, Key Laboratory for the Detection of Veterinary Drug Residues, Huazhong Agricultural University, Wuhan, Hubei, 430070, China; Department of Animal Sciences & Technology, Laboratory of Quality & Safety Risk Assessment for Livestock and Poultry Products, Huazhong Agricultural University, Wuhan, Hubei, 430070, China.
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Kal S, Que L. Dioxygen activation by nonheme iron enzymes with the 2-His-1-carboxylate facial triad that generate high-valent oxoiron oxidants. J Biol Inorg Chem 2017; 22:339-365. [PMID: 28074299 DOI: 10.1007/s00775-016-1431-2] [Citation(s) in RCA: 159] [Impact Index Per Article: 22.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2016] [Accepted: 12/13/2016] [Indexed: 11/24/2022]
Abstract
The 2-His-1-carboxylate facial triad is a widely used scaffold to bind the iron center in mononuclear nonheme iron enzymes for activating dioxygen in a variety of oxidative transformations of metabolic significance. Since the 1990s, over a hundred different iron enzymes have been identified to use this platform. This structural motif consists of two histidines and the side chain carboxylate of an aspartate or a glutamate arranged in a facial array that binds iron(II) at the active site. This triad occupies one face of an iron-centered octahedron and makes the opposite face available for the coordination of O2 and, in many cases, substrate, allowing the tailoring of the iron-dioxygen chemistry to carry out a plethora of diverse reactions. Activated dioxygen-derived species involved in the enzyme mechanisms include iron(III)-superoxo, iron(III)-peroxo, and high-valent iron(IV)-oxo intermediates. In this article, we highlight the major crystallographic, spectroscopic, and mechanistic advances of the past 20 years that have significantly enhanced our understanding of the mechanisms of O2 activation and the key roles played by iron-based oxidants.
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Affiliation(s)
- Subhasree Kal
- Department of Chemistry, Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, MN, 55455, USA
| | - Lawrence Que
- Department of Chemistry, Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, MN, 55455, USA.
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