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Zhang X, Cao Y, Liu Y, Lei Y, Zhai R, Chen W, Shi G, Jin JM, Liang C, Tang SY. Designing glucose utilization "highway" for recombinant biosynthesis. Metab Eng 2023; 78:235-247. [PMID: 37394056 DOI: 10.1016/j.ymben.2023.06.016] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2023] [Revised: 06/28/2023] [Accepted: 06/29/2023] [Indexed: 07/04/2023]
Abstract
cAMP receptor protein (CRP) is known as a global regulatory factor mainly mediating carbon source catabolism. Herein, we successfully engineered CRP to develop microbial chassis cells with improved recombinant biosynthetic capability in minimal medium with glucose as single carbon source. The obtained best-performing cAMP-independent CRPmu9 mutant conferred both faster cell growth and a 133-fold improvement in expression level of lac promoter in presence of 2% glucose, compared with strain under regulation of CRPwild-type. Promoters free from "glucose repression" are advantageous for recombinant expression, as glucose is a frequently used inexpensive carbon source in high-cell-density fermentations. Transcriptome analysis demonstrated that the CRP mutant globally rewired cell metabolism, displaying elevated tricarboxylic acid cycle activity; reduced acetate formation; increased nucleotide biosynthesis; and improved ATP synthesis, tolerance, and stress-resistance activity. Metabolites analysis confirmed the enhancement of glucose utilization with the upregulation of glycolysis and glyoxylate-tricarboxylic acid cycle. As expected, an elevated biosynthetic capability was demonstrated with vanillin, naringenin and caffeic acid biosynthesis in strains regulated by CRPmu9. This study has expanded the significance of CRP optimization into glucose utilization and recombinant biosynthesis, beyond the conventionally designated carbon source utilization other than glucose. The Escherichiacoli cell regulated by CRPmu9 can be potentially used as a beneficial chassis for recombinant biosynthesis.
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Affiliation(s)
- Xuanxuan Zhang
- CAS Key Laboratory of Microbial Physiological and Metabolic Engineering, State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China; State Key Laboratory of Transducer Technology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China; University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Yufeng Cao
- CAS Key Laboratory of Microbial Physiological and Metabolic Engineering, State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China; State Key Laboratory of Transducer Technology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China; University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Ying Liu
- Yingsheng (Beijing) Biotechnology Co., Ltd., Beijing, 100081, China
| | - Yanyan Lei
- CAS Key Laboratory of Microbial Physiological and Metabolic Engineering, State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China; State Key Laboratory of Transducer Technology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China; University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Ruixue Zhai
- Yingsheng (Beijing) Biotechnology Co., Ltd., Beijing, 100081, China
| | - Wei Chen
- CAS Key Laboratory of Microbial Physiological and Metabolic Engineering, State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China; State Key Laboratory of Transducer Technology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China
| | - Guizhi Shi
- Yingsheng (Beijing) Biotechnology Co., Ltd., Beijing, 100081, China; University of Chinese Academy of Sciences, Beijing, 100049, China.
| | - Jian-Ming Jin
- Beijing Key Laboratory of Plant Resources Research and Development, Beijing Technology and Business University, Beijing, 100048, China.
| | - Chaoning Liang
- CAS Key Laboratory of Microbial Physiological and Metabolic Engineering, State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China; State Key Laboratory of Transducer Technology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China.
| | - Shuang-Yan Tang
- CAS Key Laboratory of Microbial Physiological and Metabolic Engineering, State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China; State Key Laboratory of Transducer Technology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China.
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Yu M, Tang Y, Lu L, Kong W, Ye J. CysB Is a Key Regulator of the Antifungal Activity of Burkholderia pyrrocinia JK-SH007. Int J Mol Sci 2023; 24:ijms24098067. [PMID: 37175772 PMCID: PMC10179380 DOI: 10.3390/ijms24098067] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2023] [Revised: 04/19/2023] [Accepted: 04/28/2023] [Indexed: 05/15/2023] Open
Abstract
Burkholderia pyrrocinia JK-SH007 can effectively control poplar canker caused by pathogenic fungi. Its antifungal mechanism remains to be explored. Here, we characterized the functional role of CysB in B. pyrrocinia JK-SH007. This protein was shown to be responsible for the synthesis of cysteine and the siderophore ornibactin, as well as the antifungal activity of B. pyrrocinia JK-SH007. We found that deletion of the cysB gene reduced the antifungal activity and production of the siderophore ornibactin in B. pyrrocinia JK-SH007. However, supplementation with cysteine largely restored these two abilities in the mutant. Further global transcriptome analysis demonstrated that the amino acid metabolic pathway was significantly affected and that some sRNAs were significantly upregulated and targeted the iron-sulfur metabolic pathway by TargetRNA2 prediction. Therefore, we suggest that, in B. pyrrocinia JK-SH007, CysB can regulate the expression of genes related to Fe-S clusters in the iron-sulfur metabolic pathway to affect the antifungal activity of B. pyrrocinia JK-SH007. These findings provide new insights into the various biological functions regulated by CysB in B. pyrrocinia JK-SH007 and the relationship between iron-sulfur metabolic pathways and fungal inhibitory substances. Additionally, they lay the foundation for further investigation of the main antagonistic substances of B. pyrrocinia JK-SH007.
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Affiliation(s)
- Meng Yu
- Co-Innovation Center for Sustainable Forestry in Southern China, College of Forestry, Nanjing Forestry University, Nanjing 210037, China
| | - Yuwei Tang
- Co-Innovation Center for Sustainable Forestry in Southern China, College of Forestry, Nanjing Forestry University, Nanjing 210037, China
| | - Lanxiang Lu
- Co-Innovation Center for Sustainable Forestry in Southern China, College of Forestry, Nanjing Forestry University, Nanjing 210037, China
| | - Weiliang Kong
- Co-Innovation Center for Sustainable Forestry in Southern China, College of Forestry, Nanjing Forestry University, Nanjing 210037, China
| | - Jianren Ye
- Co-Innovation Center for Sustainable Forestry in Southern China, College of Forestry, Nanjing Forestry University, Nanjing 210037, China
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Alkhaldi HA, Vik SB. Analysis of compound heterozygous and homozygous mutations found in peripheral subunits of human respiratory Complex I, NDUFS1, NDUFS2, NDUFS8 and NDUFV1, by modeling in the E. coli enzyme. Mitochondrion 2023; 68:87-104. [PMID: 36462614 PMCID: PMC9805526 DOI: 10.1016/j.mito.2022.11.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2022] [Revised: 11/14/2022] [Accepted: 11/26/2022] [Indexed: 12/05/2022]
Abstract
Respiratory Complex I (NADH:ubiquinone oxidoreductase) is composed of 45 subunits, seven mitochondrially-encoded and 38 imported. Mutations in the nuclearly-encoded subunits have been regularly discovered in humans in recent years, and many lead to cardiomyopathy, Leigh Syndrome, and early death. From the literature, we have identified mutations at 17 different sites and constructed 31 mutants in a bacterial model system. Many of these mutations, found in NDUFS1, NDUFS2, NDUFS8, and NDUFV1, map to subunit interfaces, and we hypothesized that they would disrupt assembly of Complex I. The mutations were constructed in the homologous E. coli genes, nuoG, nuoCD, nuoI and nuoF, respectively, and expressed from a plasmid containing all Complex I genes. Membrane vesicles were prepared and rates of deamino-NADH oxidase activity measured, which indicated a range of reduced activity. Some mutants were also analyzed using recently developed assays of assembly, time-delayed expression, and co-immunoprecipitation, which showed that assembly was disrupted. With compound heterozygotes, we determined which mutation was more deleterious. Construction of alanine mutations allowed us to distinguish between phenotypes that were caused by loss of the original amino acid or introduction of the mutant residue.
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Affiliation(s)
- Hind A Alkhaldi
- Department of Biological Sciences, Southern Methodist University, Dallas, TX 75275-0376, USA
| | - Steven B Vik
- Department of Biological Sciences, Southern Methodist University, Dallas, TX 75275-0376, USA.
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Thomason LC, Court DL. Study of Ren, RexA, and RexB Functions Provides Insight Into the Complex Interaction Between Bacteriophage λ and Its Host, Escherichia coli. PHAGE (NEW ROCHELLE, N.Y.) 2022; 3:153-164. [PMID: 36204488 PMCID: PMC9529316 DOI: 10.1089/phage.2022.0020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
The phage λ rexA and rexB genes are expressed from the P RM promoter in λ lysogens along with the cI repressor gene. RexB is also expressed from a second promoter, P LIT, embedded in rexA. The combined expression of rexA and rexB causes Escherichia coli to be more ultraviolet (UV) sensitive. Sensitivity is further increased when RexB levels are reduced by a defect in the P LIT promoter, thus the degree of sensitivity can be modulated by the ratio of RexA/RexB. Expression of the phage λ ren gene rescues this host UV sensitive phenotype; Ren also rescues an aberrant lysis phenotype caused by RexA and RexB. We screened an E. coli two-hybrid library to identify bacterial proteins with which each of these phage proteins physically interact. The results extend previous observations concerning λ Rex exclusion and show the importance of E. coli electron transport and sulfur assimilation pathways for the phage.
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Affiliation(s)
- Lynn C. Thomason
- Basic Science Program, Frederick National Laboratory for Cancer Research, Frederick, Maryland, USA
- RNA Biology Laboratory, National Cancer Institute/Frederick Cancer Research and Development Center, Frederick, Maryland, USA
| | - Donald L. Court
- RNA Biology Laboratory, National Cancer Institute/Frederick Cancer Research and Development Center, Frederick, Maryland, USA
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Zhou Q, Li L, Liu F, Hu J, Cao Y, Qiao S, Zhou Y, Wang B, Jia Y, Chen Y, Xu S, Feng X. Mining and characterization of oxidative stress-related binding proteins of parthenolide in Xanthomonas oryzae pv. oryzae. PEST MANAGEMENT SCIENCE 2022; 78:3345-3355. [PMID: 35491536 DOI: 10.1002/ps.6961] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/19/2022] [Revised: 04/27/2022] [Accepted: 05/01/2022] [Indexed: 06/14/2023]
Abstract
BACKGROUND Lack of control agents and development of bacterial resistance are emergent problems in the chemical control of rice bacterial blight, therefore novel bactericides against Xanthomonas oryzae pv. oryzae (Xoo, the causal agent of rice bacterial blight) are urgently needed. We previously found that parthenolide (PTL) is a potential lead against Xoo, and PTL inhibits Xoo growth via oxidative stress. However, the mechanism of action of PTL against Xoo needs further elucidation. RESULTS In this study, a biotinylated PTL probe was synthesized, and two important subunits in the respiratory chain (NuoF of complex I and SdhB of complex II) of Xoo were captured with the probe and identified with liquid chromatography tandem mass spectrometry (LC-MS/MS). The binding between them was verified with pull-down and drug affinity responsive target stability technologies. In addition, purified proteins of NuoF and SdhB greatly lowered the antibacterial activity of PTL, and PTL evidently inhibited the enzyme activities of complexes I and II. Moreover, knockout of nuoF and sdhB in Xoo caused elevated reactive oxygen species (ROS) levels and increased sensitivity to PTL. Furthermore, molecular simulations indicated that PTL may form covalent bonds with Cys105 and Cys187 in NuoF and Cys106 in SdhB. CONCLUSION PTL can directly bind to NuoF and SdhB, which impairs the enzyme functions of complexes I and II in the respiratory chain, leading to ROS accumulation in Xoo. This study will provide deep insight into the mechanism of action of PTL against Xoo. © 2022 Society of Chemical Industry.
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Affiliation(s)
- Qian Zhou
- Jiangsu Key Laboratory for the Research and Utilization of Plant Resources, Institute of Botany, Jiangsu Province and Chinese Academy of Sciences, Nanjing, China
- Jiangsu Province Engineering Research Center of Eco-cultivation and High-Value Utilization of Chinese Medicinal Materials, Institute of Botany, Jiangsu Province and Chinese Academy of Sciences, Nanjing, China
| | - Linwei Li
- The Jiangsu Provincial Platform for Conservation and Utilization of Agricultural Germplasm, Institute of Botany, Jiangsu Province and Chinese Academy of Sciences, Nanjing, China
| | - Fei Liu
- Jiangsu Key Laboratory for the Research and Utilization of Plant Resources, Institute of Botany, Jiangsu Province and Chinese Academy of Sciences, Nanjing, China
- Jiangsu Province Engineering Research Center of Eco-cultivation and High-Value Utilization of Chinese Medicinal Materials, Institute of Botany, Jiangsu Province and Chinese Academy of Sciences, Nanjing, China
| | - Jun Hu
- The Jiangsu Provincial Platform for Conservation and Utilization of Agricultural Germplasm, Institute of Botany, Jiangsu Province and Chinese Academy of Sciences, Nanjing, China
| | - Yan Cao
- The Jiangsu Provincial Platform for Conservation and Utilization of Agricultural Germplasm, Institute of Botany, Jiangsu Province and Chinese Academy of Sciences, Nanjing, China
| | - Siwei Qiao
- Jiangsu Key Laboratory for the Research and Utilization of Plant Resources, Institute of Botany, Jiangsu Province and Chinese Academy of Sciences, Nanjing, China
- Jiangsu Province Engineering Research Center of Eco-cultivation and High-Value Utilization of Chinese Medicinal Materials, Institute of Botany, Jiangsu Province and Chinese Academy of Sciences, Nanjing, China
- Nanjing University of Chinese Medicine, Nanjing, China
| | - Yuxin Zhou
- The Jiangsu Provincial Platform for Conservation and Utilization of Agricultural Germplasm, Institute of Botany, Jiangsu Province and Chinese Academy of Sciences, Nanjing, China
| | - Bi Wang
- Jiangsu Key Laboratory for the Research and Utilization of Plant Resources, Institute of Botany, Jiangsu Province and Chinese Academy of Sciences, Nanjing, China
- Jiangsu Province Engineering Research Center of Eco-cultivation and High-Value Utilization of Chinese Medicinal Materials, Institute of Botany, Jiangsu Province and Chinese Academy of Sciences, Nanjing, China
| | - Yihe Jia
- State Key Laboratory of Natural Medicines and Jiangsu Key Laboratory of Drug Design and Optimization, China Pharmaceutical University, Nanjing, China
| | - Yu Chen
- Jiangsu Key Laboratory for the Research and Utilization of Plant Resources, Institute of Botany, Jiangsu Province and Chinese Academy of Sciences, Nanjing, China
- Jiangsu Province Engineering Research Center of Eco-cultivation and High-Value Utilization of Chinese Medicinal Materials, Institute of Botany, Jiangsu Province and Chinese Academy of Sciences, Nanjing, China
| | - Shu Xu
- Jiangsu Key Laboratory for the Research and Utilization of Plant Resources, Institute of Botany, Jiangsu Province and Chinese Academy of Sciences, Nanjing, China
- Jiangsu Province Engineering Research Center of Eco-cultivation and High-Value Utilization of Chinese Medicinal Materials, Institute of Botany, Jiangsu Province and Chinese Academy of Sciences, Nanjing, China
| | - Xu Feng
- The Jiangsu Provincial Platform for Conservation and Utilization of Agricultural Germplasm, Institute of Botany, Jiangsu Province and Chinese Academy of Sciences, Nanjing, China
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Li Q, Tu J, Jiang N, Zheng Q, Fu D, Song X, Shao Y, Qi K. Serum resistance factors in avian pathogenic Escherichia coli mediated by ETT2 gene cluster. Avian Pathol 2021; 51:34-44. [PMID: 34708677 DOI: 10.1080/03079457.2021.1998361] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
Serum resistance is a poorly understood but common trait of some systemic disease pathogenic strains of bacteria. In this study, we analysed the role Escherichia coli type three secretion system 2 (ETT2) of avian pathogenic Escherichia coli (APEC) in serum resistance by bacteria survival number in serum culture, mRNA Seq and Tandem Mass Tag™ (TMT™) detection, lipopolysaccharide (LPS) extraction, and biofilm formation detection. We found that the ETT2 gene cluster deletion strain (ΔETT2) is more resistant to the killing effect of serum than wild type APEC40. The analysis of ΔETT2 compared to APEC40 in the transcriptomics and proteomics data showed that ETT2 has a negative effect in the ATP-binding cassette (ABC) translator system and quorum sensing system and a positive effect in purine metabolism. ETT2 may affect the LPS, biofilm, flagella, and fimbriae which may affect the serum resistance. These results could lead to effective strategies for managing the infection of APEC. The mRNA Seq data of this study are available in the Sequence Read Archive of the National Center for Biotechnology Information under the BioProject PRJNA757182, and proteomic raw data have been deposited under the accession number IPX0003420000 at iProX.
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Affiliation(s)
- Qianwen Li
- Anhui Province Key Laboratory of Veterinary and Disease Control, College of Animal Science and Technology, Anhui Agricultural University, Hefei 230036, PR China
| | - Jian Tu
- Anhui Province Key Laboratory of Veterinary and Disease Control, College of Animal Science and Technology, Anhui Agricultural University, Hefei 230036, PR China
| | - Nan Jiang
- Anhui Province Key Laboratory of Veterinary and Disease Control, College of Animal Science and Technology, Anhui Agricultural University, Hefei 230036, PR China
| | - Qianqian Zheng
- Anhui Province Key Laboratory of Veterinary and Disease Control, College of Animal Science and Technology, Anhui Agricultural University, Hefei 230036, PR China
| | - Dandan Fu
- Anhui Province Key Laboratory of Veterinary and Disease Control, College of Animal Science and Technology, Anhui Agricultural University, Hefei 230036, PR China
| | - Xiangjun Song
- Anhui Province Key Laboratory of Veterinary and Disease Control, College of Animal Science and Technology, Anhui Agricultural University, Hefei 230036, PR China
| | - Ying Shao
- Anhui Province Key Laboratory of Veterinary and Disease Control, College of Animal Science and Technology, Anhui Agricultural University, Hefei 230036, PR China
| | - Kezong Qi
- Anhui Province Key Laboratory of Veterinary and Disease Control, College of Animal Science and Technology, Anhui Agricultural University, Hefei 230036, PR China
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Kang F, Yu L, Xia Y, Yu M, Xia L, Wang Y, Yang L, Wang T, Gong W, Tian C, Liu X, Wang J. Rational Design of a Miniature Photocatalytic CO 2-Reducing Enzyme. ACS Catal 2021. [DOI: 10.1021/acscatal.1c00287] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- Fuying Kang
- Laboratory of RNA Biology, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Lu Yu
- High Magnetic Field Laboratory, Chinese Academy of Sciences, Hefei, Anhui 230031, China
| | - Yan Xia
- Laboratory of RNA Biology, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Minling Yu
- Laboratory of RNA Biology, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Lin Xia
- Institute of Synthetic Biology, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China
| | - Yuchuan Wang
- Institute of Synthetic Biology, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China
| | - Lin Yang
- Hefei National Laboratory of Physical Sciences at Microscale and School of Life Sciences, University of Science and Technology of China, Hefei 230027, China
| | - Tianyuan Wang
- Laboratory of RNA Biology, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
| | - Weimin Gong
- Hefei National Laboratory of Physical Sciences at Microscale and School of Life Sciences, University of Science and Technology of China, Hefei 230027, China
| | - Changlin Tian
- High Magnetic Field Laboratory, Chinese Academy of Sciences, Hefei, Anhui 230031, China
- Hefei National Laboratory of Physical Sciences at Microscale and School of Life Sciences, University of Science and Technology of China, Hefei 230027, China
| | - Xiaohong Liu
- Laboratory of RNA Biology, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
| | - Jiangyun Wang
- Laboratory of RNA Biology, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
- University of Chinese Academy of Sciences, Beijing 100049, China
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Pernil R, Schleiff E. Metalloproteins in the Biology of Heterocysts. Life (Basel) 2019; 9:E32. [PMID: 30987221 PMCID: PMC6616624 DOI: 10.3390/life9020032] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2019] [Revised: 03/18/2019] [Accepted: 03/28/2019] [Indexed: 12/15/2022] Open
Abstract
Cyanobacteria are photoautotrophic microorganisms present in almost all ecologically niches on Earth. They exist as single-cell or filamentous forms and the latter often contain specialized cells for N₂ fixation known as heterocysts. Heterocysts arise from photosynthetic active vegetative cells by multiple morphological and physiological rearrangements including the absence of O₂ evolution and CO₂ fixation. The key function of this cell type is carried out by the metalloprotein complex known as nitrogenase. Additionally, many other important processes in heterocysts also depend on metalloproteins. This leads to a high metal demand exceeding the one of other bacteria in content and concentration during heterocyst development and in mature heterocysts. This review provides an overview on the current knowledge of the transition metals and metalloproteins required by heterocysts in heterocyst-forming cyanobacteria. It discusses the molecular, physiological, and physicochemical properties of metalloproteins involved in N₂ fixation, H₂ metabolism, electron transport chains, oxidative stress management, storage, energy metabolism, and metabolic networks in the diazotrophic filament. This provides a detailed and comprehensive picture on the heterocyst demands for Fe, Cu, Mo, Ni, Mn, V, and Zn as cofactors for metalloproteins and highlights the importance of such metalloproteins for the biology of cyanobacterial heterocysts.
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Affiliation(s)
- Rafael Pernil
- Institute for Molecular Biosciences, Goethe University Frankfurt, Max-von-Laue-Straβe 9, 60438 Frankfurt am Main, Germany.
| | - Enrico Schleiff
- Institute for Molecular Biosciences, Goethe University Frankfurt, Max-von-Laue-Straβe 9, 60438 Frankfurt am Main, Germany.
- Frankfurt Institute for Advanced Studies, Ruth-Moufang-Straße 1, 60438 Frankfurt am Main, Germany.
- Buchmann Institute for Molecular Life Sciences, Goethe University Frankfurt, Max-von-Laue-Straβe 15, 60438 Frankfurt am Main, Germany.
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Mitochondrial complex I in the post-ischemic heart: reperfusion-mediated oxidative injury and protein cysteine sulfonation. J Mol Cell Cardiol 2018; 121:190-204. [PMID: 30031815 DOI: 10.1016/j.yjmcc.2018.07.244] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/21/2018] [Revised: 07/17/2018] [Accepted: 07/18/2018] [Indexed: 12/20/2022]
Abstract
A serious consequence of ischemia-reperfusion injury (I/R) is oxidative damage leading to mitochondrial dysfunction. Such I/R-induced mitochondrial dysfunction is observed as impaired state 3 respiration and overproduction of O2-. The cascading ROS can propagate cysteine oxidation on mitochondrial complex I and add insult to injury. Herein we employed LC-MS/MS to identify protein sulfonation of complex I in mitochondria from the infarct region of rat hearts subjected to 30-min of coronary ligation and 24-h of reperfusion in vivo as well as the mitochondria of sham controls. Mitochondrial preparations from the I/R regions had enhanced sulfonation levels on the cysteine ligands of iron‑sulfur clusters, including N3 (C425), N1b (C92), N4 (C226), N2 (C158/C188), and N1a (C134/C139). The 4Fe-4S centers of N3, N1b, N4, and N2 are key redox-active components of complex I, thus sulfonation of metal-binding sites impaired the main electron transfer pathway. The binuclear N1a has a very low redox potential and an antioxidative function. Increased C134/C139 sulfonation by I/R impaired the N1a cluster, potentially contributing to overall O2- generation by the FMN moiety of complex I. MS analysis also revealed I/R-mediated increased sulfonation at the core subunits of 51 kDa (C125, C187, C206, C238, C255, C286), 75 kDa (C367, C554, C564, C727), 49 kDa (C146, C326, C347), and PSST (C188). These results were consistent with the consensus indicating that 51 kDa and 75 kDa are two of major subunits hosting regulatory thiols, and their enhanced sulfonation by I/R predisposed the myocardium to further oxidant stress with impaired ubiquinone reduction. MS analysis further showed I/R-mediated enhanced sulfonation at the supernumerary subunits of 42 kDa (C67, C112, C183, C253), 15 kDa (C43), and 13 kDa (C79). The 42 kDa protein is metazoan-specific, which was reported to stabilize mammalian complex I. C43 of the 15 kDa subunit forms an intramolecular disulfide bond with C56, which was reported to stabilize complex I structure. C79 of the 13 kDa subunit is involved in Zn2+-binding, which was reported functionally important for complex I assembly. C79 sulfonation by I/R was found to impair Zn2+-binding. No significant enhancement of protein sulfonation was observed in mitochondrial complex I from the rat heart subjected to 30-min ischemia alone in vivo despite a decreased state 3 respiration, suggesting that the physiologic conditions of hyperoxygenation during reperfusion mediated an increase in complex I sulfonation and oxidative injury. In conclusion, sulfonation of specific cysteines of complex I mediates I/R-induced mitochondrial dysfunction via impaired ETC activity, increasing •O2- production, and mediating redox dysfunction of complex I.
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Ohnishi T, Ohnishi ST, Salerno JC. Five decades of research on mitochondrial NADH-quinone oxidoreductase (complex I). Biol Chem 2018; 399:1249-1264. [DOI: 10.1515/hsz-2018-0164] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2018] [Accepted: 06/16/2018] [Indexed: 02/06/2023]
Abstract
Abstract
NADH-quinone oxidoreductase (complex I) is the largest and most complicated enzyme complex of the mitochondrial respiratory chain. It is the entry site into the respiratory chain for most of the reducing equivalents generated during metabolism, coupling electron transfer from NADH to quinone to proton translocation, which in turn drives ATP synthesis. Dysfunction of complex I is associated with neurodegenerative diseases such as Parkinson’s and Alzheimer’s, and it is proposed to be involved in aging. Complex I has one non-covalently bound FMN, eight to 10 iron-sulfur clusters, and protein-associated quinone molecules as electron transport components. Electron paramagnetic resonance (EPR) has previously been the most informative technique, especially in membrane in situ analysis. The structure of complex 1 has now been resolved from a number of species, but the mechanisms by which electron transfer is coupled to transmembrane proton pumping remains unresolved. Ubiquinone-10, the terminal electron acceptor of complex I, is detectable by EPR in its one electron reduced, semiquinone (SQ) state. In the aerobic steady state of respiration the semi-ubiquinone anion has been observed and studied in detail. Two distinct protein-associated fast and slow relaxing, SQ signals have been resolved which were designated SQNf and SQNs. This review covers a five decade personal journey through the field leading to a focus on the unresolved questions of the role of the SQ radicals and their possible part in proton pumping.
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Affiliation(s)
- Tomoko Ohnishi
- Department of Biochemistry and Biophysics , Perelman School of Medicine at University of Pennsylvania , Philadelphia, PA 19104 , USA
| | | | - John C. Salerno
- Cell and Molecular Biology Department , Kennesaw State University , Kennesaw, GA 30144 , USA
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Artz JH, Mulder DW, Ratzloff MW, Lubner CE, Zadvornyy OA, LeVan AX, Williams SG, Adams MWW, Jones AK, King PW, Peters JW. Reduction Potentials of [FeFe]-Hydrogenase Accessory Iron-Sulfur Clusters Provide Insights into the Energetics of Proton Reduction Catalysis. J Am Chem Soc 2017. [PMID: 28635269 DOI: 10.1021/jacs.7b02099] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
An [FeFe]-hydrogenase from Clostridium pasteurianum, CpI, is a model system for biological H2 activation. In addition to the catalytic H-cluster, CpI contains four accessory iron-sulfur [FeS] clusters in a branched series that transfer electrons to and from the active site. In this work, potentiometric titrations have been employed in combination with electron paramagnetic resonance (EPR) spectroscopy at defined electrochemical potentials to gain insights into the role of the accessory clusters in catalysis. EPR spectra collected over a range of potentials were deconvoluted into individual components attributable to the accessory [FeS] clusters and the active site H-cluster, and reduction potentials for each cluster were determined. The data suggest a large degree of magnetic coupling between the clusters. The distal [4Fe-4S] cluster is shown to have a lower reduction potential (∼ < -450 mV) than the other clusters, and molecular docking experiments indicate that the physiological electron donor, ferredoxin (Fd), most favorably interacts with this cluster. The low reduction potential of the distal [4Fe-4S] cluster thermodynamically restricts the Fdox/Fdred ratio at which CpI can operate, consistent with the role of CpI in recycling Fdred that accumulates during fermentation. Subsequent electron transfer through the additional accessory [FeS] clusters to the H-cluster is thermodynamically favorable.
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Affiliation(s)
- Jacob H Artz
- Institute of Biological Chemistry, Washington State University , 258 Clark Hall, Pullman, Washington 99163, United States
| | - David W Mulder
- Biosciences Center, National Renewable Energy Laboratory , 15013 Denver West Parkway, Golden, Colorado 80401, United States
| | - Michael W Ratzloff
- Biosciences Center, National Renewable Energy Laboratory , 15013 Denver West Parkway, Golden, Colorado 80401, United States
| | - Carolyn E Lubner
- Biosciences Center, National Renewable Energy Laboratory , 15013 Denver West Parkway, Golden, Colorado 80401, United States
| | - Oleg A Zadvornyy
- Institute of Biological Chemistry, Washington State University , 258 Clark Hall, Pullman, Washington 99163, United States
| | - Axl X LeVan
- Department of Chemistry and Biochemistry, Montana State University , 224 Chemistry and Biochemistry Building, Bozeman, Montana 59717, United States
| | - S Garrett Williams
- School of Molecular Sciences, Arizona State University , P.O. Box 871604, Tempe, Arizona 85287, United States
| | - Michael W W Adams
- B216B Life Sciences Complex, Department of Biochemistry, The University of Georgia , Athens, Georgia 30602, United States
| | - Anne K Jones
- School of Molecular Sciences, Arizona State University , P.O. Box 871604, Tempe, Arizona 85287, United States
| | - Paul W King
- Biosciences Center, National Renewable Energy Laboratory , 15013 Denver West Parkway, Golden, Colorado 80401, United States
| | - John W Peters
- Institute of Biological Chemistry, Washington State University , 258 Clark Hall, Pullman, Washington 99163, United States
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12
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Sinha PK, Castro-Guerrero N, Patki G, Sato M, Torres-Bacete J, Sinha S, Miyoshi H, Matsuno-Yagi A, Yagi T. Conserved amino acid residues of the NuoD segment important for structure and function of Escherichia coli NDH-1 (complex I). Biochemistry 2015; 54:753-64. [PMID: 25545070 PMCID: PMC4310626 DOI: 10.1021/bi501403t] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
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The NuoD segment (homologue of mitochondrial
49 kDa subunit) of
the proton-translocating NADH:quinone oxidoreductase (complex I/NDH-1)
from Escherichia coli is in the hydrophilic domain
and bears many highly conserved amino acid residues. The three-dimensional
structural model of NDH-1 suggests that the NuoD segment, together
with the neighboring subunits, constitutes a putative quinone binding
cavity. We used the homologous DNA recombination technique to clarify
the role of selected key amino acid residues of the NuoD segment.
Among them, residues Tyr273 and His224 were considered candidates
for having important interactions with the quinone headgroup. Mutant
Y273F retained partial activity but lost sensitivity to capsaicin-40.
Mutant H224R scarcely affected the activity, suggesting that this
residue may not be essential. His224 is located in a loop near the
N-terminus of the NuoD segment (Gly217–Phe227) which is considered
to form part of the quinone binding cavity. In contrast to the His224
mutation, mutants G217V, P218A, and G225V almost completely lost the
activity. One region of this loop is positioned close to a cytosolic
loop of the NuoA subunit in the membrane domain, and together they
seem to be important in keeping the quinone binding cavity intact.
The structural role of the longest helix in the NuoD segment located
behind the quinone binding cavity was also investigated. Possible
roles of other highly conserved residues of the NuoD segment are discussed.
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Affiliation(s)
- Prem Kumar Sinha
- Deparment of Molecular and Experimental Medicine, and ‡Department of Cell and Molecular Biology, The Scripps Research Institute , 10550 North Torrey Pines Road, MEM256, La Jolla, California 92037, United States
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13
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Sato M, Torres-Bacete J, Sinha PK, Matsuno-Yagi A, Yagi T. Essential regions in the membrane domain of bacterial complex I (NDH-1): the machinery for proton translocation. J Bioenerg Biomembr 2014; 46:279-87. [PMID: 24973951 DOI: 10.1007/s10863-014-9558-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2014] [Accepted: 06/18/2014] [Indexed: 01/09/2023]
Abstract
The proton-translocating NADH-quinone oxidoreductase (complex I/NDH-1) is the first and largest enzyme of the respiratory chain which has a central role in cellular energy production and is implicated in many human neurodegenerative diseases and aging. It is believed that the peripheral domain of complex I/NDH-1 transfers the electron from NADH to Quinone (Q) and the redox energy couples the proton translocation in the membrane domain. To investigate the mechanism of the proton translocation, in a series of works we have systematically studied all membrane subunits in the Escherichia coli NDH-1 by site-directed mutagenesis. In this mini-review, we have summarized our strategy and results of the mutagenesis by depicting residues essential for proton translocation, along with those for subunit connection. It is suggested that clues to understanding the driving forces of proton translocation lie in the similarities and differences of the membrane subunits, highlighting the communication of essential charged residues among the subunits. A possible proton translocation mechanism with all membrane subunits operating in unison is described.
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Affiliation(s)
- Motoaki Sato
- Department of Molecular and Experimental Medicine, MEM-256, The Scripps Research Institute, La Jolla, CA, 92037, USA,
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14
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Barker CS, Meshcheryakova IV, Sasaki T, Roy MC, Sinha PK, Yagi T, Samatey FA. Randomly selected suppressor mutations in genes for NADH : quinone oxidoreductase-1, which rescue motility of a Salmonella ubiquinone-biosynthesis mutant strain. MICROBIOLOGY-SGM 2014; 160:1075-1086. [PMID: 24692644 DOI: 10.1099/mic.0.075945-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The primary mobile electron-carrier in the aerobic respiratory chain of Salmonella is ubiquinone. Demethylmenaquinone and menaquinone are alternative electron-carriers involved in anaerobic respiration. Ubiquinone biosynthesis was disrupted in strains bearing deletions of the ubiA or ubiE genes. In soft tryptone agar both mutant strains swam poorly. However, the ubiA deletion mutant strain produced suppressor mutant strains with somewhat rescued motility and growth. Six independent suppressor mutants were purified and comparative genome sequence analysis revealed that they each bore a single new missense mutation, which localized to genes for subunits of NADH : quinone oxidoreductase-1. Four mutants bore an identical nuoG(Q297K) mutation, one mutant bore a nuoM(A254S) mutation and one mutant bore a nuoN(A444E) mutation. The NuoG subunit is part of the hydrophilic domain of NADH : quinone oxidoreductase-1 and the NuoM and NuoN subunits are part of the hydrophobic membrane-embedded domain. Respiration was rescued and the suppressed mutant strains grew better in Luria-Bertani broth medium and could use l-malate as a sole carbon source. The quinone pool of the cytoplasmic membrane was characterized by reversed-phase HPLC. Wild-type cells made ubiquinone and menaquinone. Strains with a ubiA deletion mutation made demethylmenaquinone and menaquinone and the ubiE deletion mutant strain made demethylmenaquinone and 2-octaprenyl-6-methoxy-1,4-benzoquinone; the total quinone pool was reduced. Immunoblotting found increased NADH : quinone oxidoreductase-1 levels for ubiquinone-biosynthesis mutant strains and enzyme assays measured electron transfer from NADH to demethylmenaquinone or menaquinone. Under certain growth conditions the suppressor mutations improved electron flow activity of NADH : quinone oxidoreductase-1 for cells bearing a ubiA deletion mutation.
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Affiliation(s)
- Clive S Barker
- Trans-membrane Trafficking Unit, Okinawa Institute of Science and Technology, Okinawa, Japan
| | - Irina V Meshcheryakova
- Trans-membrane Trafficking Unit, Okinawa Institute of Science and Technology, Okinawa, Japan
| | - Toshio Sasaki
- Research Support Section, Okinawa Institute of Science and Technology, Okinawa, Japan
| | - Michael C Roy
- Research Support Section, Okinawa Institute of Science and Technology, Okinawa, Japan
| | - Prem Kumar Sinha
- Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, CA, USA
| | - Takao Yagi
- Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, CA, USA
| | - Fadel A Samatey
- Trans-membrane Trafficking Unit, Okinawa Institute of Science and Technology, Okinawa, Japan
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15
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Sato M, Sinha PK, Torres-Bacete J, Matsuno-Yagi A, Yagi T. Energy transducing roles of antiporter-like subunits in Escherichia coli NDH-1 with main focus on subunit NuoN (ND2). J Biol Chem 2013; 288:24705-16. [PMID: 23864658 DOI: 10.1074/jbc.m113.482968] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The proton-translocating NADH-quinone oxidoreductase (complex I/NDH-1) contains a peripheral and a membrane domain. Three antiporter-like subunits in the membrane domain, NuoL, NuoM, and NuoN (ND5, ND4 and ND2, respectively), are structurally similar. We analyzed the role of NuoN in Escherichia coli NDH-1. The lysine residue at position 395 in NuoN (NLys(395)) is conserved in NuoL (LLys(399)) but is replaced by glutamic acid (MGlu(407)) in NuoM. Our mutation study on NLys(395) suggests that this residue participates in the proton translocation. Furthermore, we found that MGlu(407) is also essential and most likely interacts with conserved LArg(175). Glutamic acids, NGlu(133), MGlu(144), and LGlu(144), are corresponding residues. Unlike mutants of MGlu(144) and LGlu(144), mutation of NGlu(133) scarcely affected the energy-transducing activities. However, a double mutant of NGlu(133) and nearby KGlu(72) showed significant inhibition of these activities. This suggests that NGlu(133) bears a functional role similar to LGlu(144) and MGlu(144) but its mutation can be partially compensated by the nearby carboxyl residue. Conserved prolines located at loops of discontinuous transmembrane helices of NuoL, NuoM, and NuoN were shown to play a similar role in the energy-transducing activity. It seems likely that NuoL, NuoM, and NuoN pump protons by a similar mechanism. Our data also revealed that NLys(158) is one of the key interaction points with helix HL in NuoL. A truncation study indicated that the C-terminal amphipathic segments of NTM14 interacts with the Mβ sheet located on the opposite side of helix HL. Taken together, the mechanism of H(+) translocation in NDH-1 is discussed.
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Affiliation(s)
- Motoaki Sato
- Department of Molecular and Experimental Medicine, MEM-256, The Scripps Research Institute, La Jolla, California 92037, USA
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16
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Narayanan M, Gabrieli DJ, Leung SA, Elguindy MM, Glaser CA, Saju N, Sinha SC, Nakamaru-Ogiso E. Semiquinone and cluster N6 signals in His-tagged proton-translocating NADH:ubiquinone oxidoreductase (complex I) from Escherichia coli. J Biol Chem 2013; 288:14310-14319. [PMID: 23543743 DOI: 10.1074/jbc.m113.467803] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
NADH:ubiquinone oxidoreductase (complex I) pumps protons across the membrane using downhill redox energy. The Escherichia coli complex I consists of 13 different subunits named NuoA-N coded by the nuo operon. Due to the low abundance of the protein and some difficulty with the genetic manipulation of its large ~15-kb operon, purification of E. coli complex I has been technically challenging. Here, we generated a new strain in which a polyhistidine sequence was inserted upstream of nuoE in the operon. This allowed us to prepare large amounts of highly pure and active complex I by efficient affinity purification. The purified complex I contained 0.94 ± 0.1 mol of FMN, 29.0 ± 0.37 mol of iron, and 1.99 ± 0.07 mol of ubiquinone/1 mol of complex I. The extinction coefficient of isolated complex I was 495 mM(-1) cm(-1) at 274 nm and 50.3 mM(-1) cm(-1) at 410 nm. NADH:ferricyanide activity was 219 ± 9.7 μmol/min/mg by using HEPES-Bis-Tris propane, pH 7.5. Detailed EPR analyses revealed two additional iron-sulfur cluster signals, N6a and N6b, in addition to previously assigned signals. Furthermore, we found small but significant semiquinone signal(s), which have been reported only for bovine complex I. The line width was ~12 G, indicating its neutral semiquinone form. More than 90% of the semiquinone signal originated from the single entity with P½ (half-saturation power level) = 1.85 milliwatts. The semiquinone signal(s) decreased by 60% when with asimicin, a potent complex I inhibitor. The functional role of semiquinone and the EPR assignment of clusters N6a/N6b are discussed.
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Affiliation(s)
- Madhavan Narayanan
- Johnson Research Foundation, Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104
| | - David J Gabrieli
- Johnson Research Foundation, Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104
| | - Steven A Leung
- Johnson Research Foundation, Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104
| | - Mahmoud M Elguindy
- Johnson Research Foundation, Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104
| | - Carl A Glaser
- Johnson Research Foundation, Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104
| | - Nitha Saju
- Johnson Research Foundation, Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104
| | - Subhash C Sinha
- Department of Molecular Biology, The Scripps Research Institute, La Jolla, California 92037
| | - Eiko Nakamaru-Ogiso
- Johnson Research Foundation, Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104.
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17
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Torres-Bacete J, Sinha PK, Sato M, Patki G, Kao MC, Matsuno-Yagi A, Yagi T. Roles of subunit NuoK (ND4L) in the energy-transducing mechanism of Escherichia coli NDH-1 (NADH:quinone oxidoreductase). J Biol Chem 2012; 287:42763-72. [PMID: 23105119 DOI: 10.1074/jbc.m112.422824] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The bacterial H(+)-translocating NADH:quinone oxidoreductase (NDH-1) catalyzes electron transfer from NADH to quinone coupled with proton pumping across the cytoplasmic membrane. The NuoK subunit (counterpart of the mitochondrial ND4L subunit) is one of the seven hydrophobic subunits in the membrane domain and bears three transmembrane segments (TM1-3). Two glutamic residues located in the adjacent transmembrane helices of NuoK are important for the energy coupled activity of NDH-1. In particular, mutation of the highly conserved carboxyl residue ((K)Glu-36 in TM2) to Ala led to a complete loss of the NDH-1 activities. Mutation of the second conserved carboxyl residue ((K)Glu-72 in TM3) moderately reduced the activities. To clarify the contribution of NuoK to the mechanism of proton translocation, we relocated these two conserved residues. When we shifted (K)Glu-36 along TM2 to positions 32, 38, 39, and 40, the mutants largely retained energy transducing NDH-1 activities. According to the recent structural information, these positions are located in the vicinity of (K)Glu-36, present in the same helix phase, in an immediately before and after helix turn. In an earlier study, a double mutation of two arginine residues located in a short cytoplasmic loop between TM1 and TM2 (loop-1) showed a drastic effect on energy transducing activities. Therefore, the importance of this cytosolic loop of NuoK ((K)Arg-25, (K)Arg-26, and (K)Asn-27) for the energy transducing activities was extensively studied. The probable roles of subunit NuoK in the energy transducing mechanism of NDH-1 are discussed.
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Affiliation(s)
- Jesus Torres-Bacete
- Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, California 92037, USA
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