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Dong L, Li X, Li A, Yi J, Zhou J. Isolation of Mitochondria from Murine Skeletal Muscle. Methods Mol Biol 2024; 2816:77-85. [PMID: 38977590 DOI: 10.1007/978-1-0716-3902-3_8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/10/2024]
Abstract
Skeletal muscle is one of the largest tissues in human body. Besides enabling voluntary movements and maintaining body's metabolic homeostasis, skeletal muscle is also a target of many pathological conditions. Mitochondria occupy 10-15% volume of a muscle myofiber and regulate many cellular processes, which often determine the fate of the cell. Isolation of mitochondria from skeletal muscle provides opportunities for various multi-omics studies with a focus on mitochondria in biomedical research field. Here we describe a protocol to efficiently isolate mitochondria with high quality and purity from skeletal muscle of mice using Nycodenz density gradient ultracentrifugation.
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Affiliation(s)
- Li Dong
- Bone-Muscle Research Center, Department of Kinesiology, College of Nursing and Health Innovation, University of Texas at Arlington, Arlington, TX, USA
| | - Xuejun Li
- Bone-Muscle Research Center, Department of Kinesiology, College of Nursing and Health Innovation, University of Texas at Arlington, Arlington, TX, USA
| | - Ang Li
- Bone-Muscle Research Center, Department of Kinesiology, College of Nursing and Health Innovation, University of Texas at Arlington, Arlington, TX, USA
| | - Jianxun Yi
- Bone-Muscle Research Center, Department of Kinesiology, College of Nursing and Health Innovation, University of Texas at Arlington, Arlington, TX, USA
| | - Jingsong Zhou
- Bone-Muscle Research Center, Department of Kinesiology, College of Nursing and Health Innovation, University of Texas at Arlington, Arlington, TX, USA.
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Rickard BP, Overchuk M, Chappell VA, Kemal Ruhi M, Sinawang PD, Nguyen Hoang TT, Akin D, Demirci U, Franco W, Fenton SE, Santos JH, Rizvi I. Methods to Evaluate Changes in Mitochondrial Structure and Function in Cancer. Cancers (Basel) 2023; 15:2564. [PMID: 37174030 PMCID: PMC10177605 DOI: 10.3390/cancers15092564] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2023] [Revised: 04/25/2023] [Accepted: 04/26/2023] [Indexed: 05/15/2023] Open
Abstract
Mitochondria are regulators of key cellular processes, including energy production and redox homeostasis. Mitochondrial dysfunction is associated with various human diseases, including cancer. Importantly, both structural and functional changes can alter mitochondrial function. Morphologic and quantifiable changes in mitochondria can affect their function and contribute to disease. Structural mitochondrial changes include alterations in cristae morphology, mitochondrial DNA integrity and quantity, and dynamics, such as fission and fusion. Functional parameters related to mitochondrial biology include the production of reactive oxygen species, bioenergetic capacity, calcium retention, and membrane potential. Although these parameters can occur independently of one another, changes in mitochondrial structure and function are often interrelated. Thus, evaluating changes in both mitochondrial structure and function is crucial to understanding the molecular events involved in disease onset and progression. This review focuses on the relationship between alterations in mitochondrial structure and function and cancer, with a particular emphasis on gynecologic malignancies. Selecting methods with tractable parameters may be critical to identifying and targeting mitochondria-related therapeutic options. Methods to measure changes in mitochondrial structure and function, with the associated benefits and limitations, are summarized.
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Affiliation(s)
- Brittany P. Rickard
- Curriculum in Toxicology & Environmental Medicine, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Marta Overchuk
- Joint Department of Biomedical Engineering, University of North Carolina at Chapel Hill, Chapel Hill, NC, and North Carolina State University, Raleigh, NC 27695, USA
| | - Vesna A. Chappell
- Mechanistic Toxicology Branch, Division of Translational Toxicology, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709, USA
| | - Mustafa Kemal Ruhi
- Institute of Biomedical Engineering, Boğaziçi University, Istanbul 34684, Turkey
| | - Prima Dewi Sinawang
- Canary Center at Stanford for Cancer Early Detection, Department of Radiology, School of Medicine, Palo Alto, CA 94304, USA
- Department of Chemical Engineering, Stanford University, Stanford, CA 94305, USA
| | - Tina Thuy Nguyen Hoang
- Department of Biomedical Engineering, University of Massachusetts Lowell, Lowell, MA 01854, USA
| | - Demir Akin
- Canary Center at Stanford for Cancer Early Detection, Department of Radiology, School of Medicine, Palo Alto, CA 94304, USA
- Center for Cancer Nanotechnology Excellence for Translational Diagnostics (CCNE-TD), School of Medicine, Stanford University, Stanford, CA 94305, USA
| | - Utkan Demirci
- Canary Center at Stanford for Cancer Early Detection, Department of Radiology, School of Medicine, Palo Alto, CA 94304, USA
| | - Walfre Franco
- Department of Biomedical Engineering, University of Massachusetts Lowell, Lowell, MA 01854, USA
| | - Suzanne E. Fenton
- Mechanistic Toxicology Branch, Division of Translational Toxicology, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709, USA
| | - Janine H. Santos
- Mechanistic Toxicology Branch, Division of Translational Toxicology, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709, USA
| | - Imran Rizvi
- Joint Department of Biomedical Engineering, University of North Carolina at Chapel Hill, Chapel Hill, NC, and North Carolina State University, Raleigh, NC 27695, USA
- Lineberger Comprehensive Cancer Center, University of North Carolina School of Medicine, Chapel Hill, NC 27599, USA
- Center for Environmental Health and Susceptibility, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
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3
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Tetrabromobisphenol Exposure Impairs Bovine Oocyte Maturation by Inducing Mitochondrial Dysfunction. Molecules 2022; 27:molecules27228111. [PMID: 36432212 PMCID: PMC9696588 DOI: 10.3390/molecules27228111] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2022] [Revised: 11/10/2022] [Accepted: 11/17/2022] [Indexed: 11/23/2022] Open
Abstract
Tetrabromobisphenol (TBBPA) is the most widely used brominated flame retardant in the world and displays toxicity to humans and animals. However, few studies have focused on its impact on oocyte maturation. Here, TBBPA was added to the culture medium of bovine cumulus-oocyte complexes (COCs) to examine its effect on oocytes. We found that TBBPA exposure displayed an adverse influence on oocyte maturation and subsequent embryonic development. The results of this study showed that TBBPA exposure induced oocyte meiotic failure by disturbing the polar-body extrusion of oocytes and the expansion of cumulus cells. We further found that TBBPA exposure led to defective spindle assembly and chromosome alignment. Meanwhile, TBBPA induced oxidative stress and early apoptosis by mediating the expression of superoxide dismutase 2 (SOD2). TBBPA exposure also caused mitochondrial dysfunction, displaying a decrease in mitochondrial membrane potential, mitochondrial content, mtDNA copy number, and ATP levels, which are regulated by the expression of pyruvate dehydrogenase kinase 3 (PDK3). In addition, the developmental competence of oocytes and the quality of blastocysts were also reduced after TBBPA treatment. These results demonstrated that TBBPA exposure impaired oocyte maturation and developmental competence by disrupting both nuclear and cytoplasmic maturation of the oocyte, which might have been caused by oxidative stress induced by mitochondrial dysfunction.
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Yang X, Xu Y, Gao W, Wang L, Zhao X, Liu G, Fan K, Liu S, Hao H, Qu S, Dong R, Ma X, Ma J. Hyperinsulinemia-induced microglial mitochondrial dynamic and metabolic alterations lead to neuroinflammation in vivo and in vitro. Front Neurosci 2022; 16:1036872. [DOI: 10.3389/fnins.2022.1036872] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2022] [Accepted: 10/31/2022] [Indexed: 11/17/2022] Open
Abstract
Numerous studies have demonstrated that type 2 diabetes (T2D) is closely linked to the occurrence of Alzheimer’s disease (AD). Nevertheless, the underlying mechanisms for this association are still unknown. Insulin resistance (IR) hallmarked by hyperinsulinemia, as the earliest and longest-lasting pathological change in T2D, might play an important role in AD. Since hyperinsulinemia has an independent contribution to related disease progressions by promoting inflammation in the peripheral system, we hypothesized that hyperinsulinemia might have an effect on microglia which plays a crucial role in neuroinflammation of AD. In the present study, we fed 4-week-old male C57BL/6 mice with a high-fat diet (HFD) for 12 weeks to establish IR model, and the mice treated with standard diet (SD) were used as control. HFD led to obesity in mice with obvious glucose and lipid metabolism disorder, the higher insulin levels in both plasma and cerebrospinal fluid, and aberrant insulin signaling pathway in the whole brain. Meanwhile, IR mice appeared impairments of spatial learning and memory accompanied by neuroinflammation which was characterized by activated microglia and upregulated expression of pro-inflammatory factors in different brain regions. To clarify whether insulin contributes to microglial activation, we treated primary cultured microglia and BV2 cell lines with insulin in vitro to mimic hyperinsulinemia. We found that hyperinsulinemia not only increased microglial proliferation and promoted M1 polarization by enhancing the production of pro-inflammatory factors, but also impaired membrane translocation of glucose transporter 4 (GLUT4) serving as the insulin-responding glucose transporter in the processes of glucose up-taking, reduced ATP production and increased mitochondrial fission. Our study provides new perspectives and evidence for the mechanism underlying the association between T2D and AD.
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Simple to Complex: The Role of Actin and Microtubules in Mitochondrial Dynamics in Amoeba, Yeast, and Mammalian Cells. Int J Mol Sci 2022; 23:ijms23169402. [PMID: 36012665 PMCID: PMC9409391 DOI: 10.3390/ijms23169402] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2022] [Revised: 08/14/2022] [Accepted: 08/16/2022] [Indexed: 11/17/2022] Open
Abstract
Mitochondria are complex organelles that provide energy for the cell in the form of adenosine triphosphate (ATP) and have very specific structures. For most organisms, this is a reticular or tubular mitochondrial network, while others have singular oval-shaped organelles. Nonetheless, maintenance of this structure is dependent on the mitochondrial dynamics, fission, fusion, and motility. Recently, studies have shown that the cytoskeleton has a significant role in the regulation of mitochondrial dynamics. In this review, we focus on microtubules and actin filaments and look at what is currently known about the cytoskeleton’s role in mitochondrial dynamics in complex models like mammals and yeast, as well as what is known in the simple model system, Dictyostelium discoideum. Understanding how the cytoskeleton is involved in mitochondrial dynamics increases our understanding of mitochondrial disease, especially neurodegenerative diseases. Increases in fission, loss of fusion, and fragmented mitochondria are seen in several neurodegenerative diseases such as Parkinson’s, Alzheimer’s, and Huntington’s disease. There is no known cure for these diseases, but new therapeutic strategies using drugs to alter mitochondrial fusion and fission activity are being considered. The future of these therapeutic studies is dependent on an in-depth understanding of the mechanisms of mitochondrial dynamics. Understanding the cytoskeleton’s role in dynamics in multiple model organisms will further our understanding of these mechanisms and could potentially uncover new therapeutic targets for these neurodegenerative diseases.
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Zhang T, Che X, Li H, Zhang L, Liu J. The Damage Mechanisms of Dark Hypoxic Stress on Photosystem
II
of
Cymodocea Rotundata. Photochem Photobiol 2022; 98:1323-1331. [DOI: 10.1111/php.13641] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2022] [Accepted: 05/05/2022] [Indexed: 11/28/2022]
Affiliation(s)
- Tie Zhang
- CAS and Shandong Key Laboratory of Experimental Marine Biology, Center for Ocean Mega‐Science Institute of Oceanology Chinese Academy of Sciences, 7 Nanhai Road Qingdao 266071 China
- University of Chinese Academy of Sciences Beijing 100049 China
| | - Xingkai Che
- CAS and Shandong Key Laboratory of Experimental Marine Biology, Center for Ocean Mega‐Science Institute of Oceanology Chinese Academy of Sciences, 7 Nanhai Road Qingdao 266071 China
- Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, 1 Wenhai Road, Aoshanwei Town, Jimo Qingdao 266237 China
| | - Hu Li
- CAS and Shandong Key Laboratory of Experimental Marine Biology, Center for Ocean Mega‐Science Institute of Oceanology Chinese Academy of Sciences, 7 Nanhai Road Qingdao 266071 China
- Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, 1 Wenhai Road, Aoshanwei Town, Jimo Qingdao 266237 China
| | - Litao Zhang
- CAS and Shandong Key Laboratory of Experimental Marine Biology, Center for Ocean Mega‐Science Institute of Oceanology Chinese Academy of Sciences, 7 Nanhai Road Qingdao 266071 China
- Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, 1 Wenhai Road, Aoshanwei Town, Jimo Qingdao 266237 China
| | - Jianguo Liu
- CAS and Shandong Key Laboratory of Experimental Marine Biology, Center for Ocean Mega‐Science Institute of Oceanology Chinese Academy of Sciences, 7 Nanhai Road Qingdao 266071 China
- Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, 1 Wenhai Road, Aoshanwei Town, Jimo Qingdao 266237 China
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Wang X, Jia L, Wang M, Yang H, Chen M, Li X, Liu H, Li Q, Liu N. The complete mitochondrial genome of medicinal fungus Taiwanofungus camphoratus reveals gene rearrangements and intron dynamics of Polyporales. Sci Rep 2020; 10:16500. [PMID: 33020532 PMCID: PMC7536210 DOI: 10.1038/s41598-020-73461-x] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2020] [Accepted: 09/08/2020] [Indexed: 12/31/2022] Open
Abstract
Taiwanofungus camphoratus is a highly valued medicinal mushroom that is endemic to Taiwan, China. In the present study, the mitogenome of T. camphoratus was assembled and compared with other published Polyporales mitogenomes. The T. camphoratus mitogenome was composed of circular DNA molecules, with a total size of 114,922 bp. Genome collinearity analysis revealed large-scale gene rearrangements between the mitogenomes of Polyporales, and T. camphoratus contained a unique gene order. The number and classes of introns were highly variable in 12 Polyporales species we examined, which proved that numerous intron loss or gain events occurred in the evolution of Polyporales. The Ka/Ks values for most core protein coding genes in Polyporales species were less than 1, indicating that these genes were subject to purifying selection. However, the rps3 gene was found under positive or relaxed selection between some Polyporales species. Phylogenetic analysis based on the combined mitochondrial gene set obtained a well-supported topology, and T. camphoratus was identified as a sister species to Laetiporus sulphureus. This study served as the first report on the mitogenome in the Taiwanofungus genus, which will provide a basis for understanding the phylogeny and evolution of this important fungus.
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Affiliation(s)
- Xu Wang
- College of Life Sciences, Henan Agricultural University, Zhengzhou, 450002, Henan, China
| | - Lihua Jia
- College of Life Sciences, Henan Agricultural University, Zhengzhou, 450002, Henan, China
| | - Mingdao Wang
- College of Life Sciences, Henan Agricultural University, Zhengzhou, 450002, Henan, China
| | - Hao Yang
- College of Life Sciences, Henan Agricultural University, Zhengzhou, 450002, Henan, China
| | - Mingyue Chen
- College of Life Sciences, Henan Agricultural University, Zhengzhou, 450002, Henan, China
| | - Xiao Li
- College of Life Sciences, Henan Agricultural University, Zhengzhou, 450002, Henan, China
| | - Hanyu Liu
- College of Life Sciences, Henan Agricultural University, Zhengzhou, 450002, Henan, China
| | - Qiang Li
- School of Food and Biological Engineering, Chengdu University, Chengdu, 610106, Sichuan, China.
- College of Life Sciences, Henan Agricultural University, Zhengzhou, 450002, Henan, China.
| | - Na Liu
- College of Life Sciences, Henan Agricultural University, Zhengzhou, 450002, Henan, China.
- College of Life Sciences, Henan Agricultural University, Zhengzhou, 450002, Henan, China.
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Protection against Mitochondrial and Metal Toxicity Depends on Functional Lipid Binding Sites in ATP13A2. PARKINSONS DISEASE 2016; 2016:9531917. [PMID: 27073711 PMCID: PMC4814700 DOI: 10.1155/2016/9531917] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/29/2015] [Accepted: 02/23/2016] [Indexed: 12/29/2022]
Abstract
The late endo-/lysosomal P-type ATPase ATP13A2 (PARK9) is implicated in Parkinson's disease (PD) and Kufor-Rakeb syndrome, early-onset atypical Parkinsonism. ATP13A2 interacts at the N-terminus with the signaling lipids phosphatidic acid (PA) and phosphatidylinositol (3,5) bisphosphate (PI(3,5)P2), which modulate ATP13A2 activity under cellular stress conditions. Here, we analyzed stable human SHSY5Y cell lines overexpressing wild-type (WT) or ATP13A2 mutants in which three N-terminal lipid binding sites (LBS1–3) were mutated. We explored the regulatory role of LBS1–3 in the cellular protection by ATP13A2 against mitochondrial stress induced by rotenone and found that the LBS2-3 mutants displayed an abrogated protective effect. Moreover, in contrast to WT, the LBS2 and LBS3 mutants responded poorly to pharmacological inhibition of, respectively, PI(3,5)P2 and PA formation. We further demonstrate that PA and PI(3,5)P2 are also required for the ATP13A2-mediated protection against the toxic metals Mn2+, Zn2+, and Fe3+, suggesting a general lipid-dependent activation mechanism of ATP13A2 in various PD-related stress conditions. Our results indicate that the ATP13A2-mediated protection requires binding of PI(3,5)P2 to LBS2 and PA to LBS3. Thus, targeting the N-terminal lipid binding sites of ATP13A2 might offer a therapeutic approach to reduce cellular toxicity of various PD insults including mitochondrial stress.
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Abstract
The F1F0-ATP synthase (EC 3.6.1.34) is a remarkable enzyme that functions as a rotary motor. It is found in the inner membranes of Escherichia coli and is responsible for the synthesis of ATP in response to an electrochemical proton gradient. Under some conditions, the enzyme functions reversibly and uses the energy of ATP hydrolysis to generate the gradient. The ATP synthase is composed of eight different polypeptide subunits in a stoichiometry of α3β3γδεab2c10. Traditionally they were divided into two physically separable units: an F1 that catalyzes ATP hydrolysis (α3β3γδε) and a membrane-bound F0 sector that transports protons (ab2c10). In terms of rotary function, the subunits can be divided into rotor subunits (γεc10) and stator subunits (α3β3δab2). The stator subunits include six nucleotide binding sites, three catalytic and three noncatalytic, formed primarily by the β and α subunits, respectively. The stator also includes a peripheral stalk composed of δ and b subunits, and part of the proton channel in subunit a. Among the rotor subunits, the c subunits form a ring in the membrane, and interact with subunit a to form the proton channel. Subunits γ and ε bind to the c-ring subunits, and also communicate with the catalytic sites through interactions with α and β subunits. The eight subunits are expressed from a single operon, and posttranscriptional processing and translational regulation ensure that the polypeptides are made at the proper stoichiometry. Recent studies, including those of other species, have elucidated many structural and rotary properties of this enzyme.
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Wang ZP, Ding XZ, Wang J, Li YM. Double-edged sword in cells: chemical biology studies of the vital role of cytochrome c in the intrinsic pre-apoptotic mitochondria leakage pathway. RSC Adv 2015. [DOI: 10.1039/c4ra16856a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Besides functioning as an electron transporter in the mitochondrial electron transport chain, cytochrome c (cyt c) is also one of the determinants in the execution of cell death.
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Affiliation(s)
- Zhi-Peng Wang
- School of Medical Engineering
- Hefei University of Technology
- Hefei
- China
- Department of Chemistry
| | - Xiao-Zhe Ding
- Department of Chemistry
- School of Life Sciences
- Tsinghua University
- Beijing 100084
- China
| | - Jun Wang
- School of Medical Engineering
- Hefei University of Technology
- Hefei
- China
| | - Yi-Ming Li
- School of Medical Engineering
- Hefei University of Technology
- Hefei
- China
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Maioli MA, de Medeiros HCD, Guelfi M, Trinca V, Pereira FTV, Mingatto FE. The role of mitochondria and biotransformation in abamectin-induced cytotoxicity in isolated rat hepatocytes. Toxicol In Vitro 2012; 27:570-9. [PMID: 23142325 DOI: 10.1016/j.tiv.2012.10.017] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2012] [Revised: 10/27/2012] [Accepted: 10/29/2012] [Indexed: 11/27/2022]
Abstract
Abamectin (ABA), which belongs to the family of avermectins, is used as a parasiticide; however, ABA poisoning can impair liver function. In a previous study using isolated rat liver mitochondria, we observed that ABA inhibited the activity of adenine nucleotide translocator and FoF1-ATPase. The aim of this study was to characterize the mechanism of ABA toxicity in isolated rat hepatocytes and to evaluate whether this effect is dependent on its metabolism. The toxicity of ABA was assessed by monitoring oxygen consumption and mitochondrial membrane potential, intracellular ATP concentration, cell viability, intracellular Ca(2+) homeostasis, release of cytochrome c, caspase 3 activity and necrotic cell death. ABA reduces cellular respiration in cells energized with glutamate and malate or succinate. The hepatocytes that were previously incubated with proadifen, a cytochrome P450 inhibitor, are more sensitive to the compound as observed by a rapid decrease in the mitochondrial membrane potential accompanied by reductions in ATP concentration and cell viability and a disruption of intracellular Ca(2+) homeostasis followed by necrosis. Our results indicate that ABA biotransformation reduces its toxicity, and its toxic action is related to the inhibition of mitochondrial activity, which leads to decreased synthesis of ATP followed by cell death.
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Affiliation(s)
- Marcos A Maioli
- Laboratório de Bioquímica Metabólica e Toxicológica (LaBMeT), UNESP - Univ Estadual Paulista, Campus de Dracena, 17900-000 Dracena, SP, Brazil
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Choi EM, Lee YS. Protective effect of apocynin on antimycin A-induced cell damage in osteoblastic MC3T3-E1 cells. J Appl Toxicol 2011; 32:714-21. [PMID: 21538410 DOI: 10.1002/jat.1689] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2011] [Revised: 04/03/2011] [Accepted: 04/04/2011] [Indexed: 12/13/2022]
Abstract
Apocynin is a naturally occurring methoxy-substituted catechol, experimentally used as an inhibitor of NADPH-oxidase. In the present study, we investigated the protective effects of apocynin on antimycin A (AMA)-induced toxicicy in osteoblastic MC3T3-E1 cells. Exposure of MC3T3-E1 cells to AMA caused significant cell viability loss, as well as mitochondrial membrane potential (MMP) dissipation, complex IV inactivation, ATP loss, intracellular calcium ([Ca2+]i) elevation and oxidative stress. Pretreatment with apocynin prior to AMA exposure significantly reduced AMA-induced cell damage by preventing MMP dissipation, complex IV inactivation, ATP loss, [Ca2+]i elevation and oxidative stress. These results suggest that apocynin has a protective effect against AMA-induced cell damage by its antioxidant effects and the attenuation of mitochondrial dysfunction. Apocynin also induced the activation of PI3K (phosphoinositide 3-kinase), Akt (protein kinase B) and CREB (cAMP-response element-binding protein) inhibited by AMA. All these data indicate that apocynin may reduce or prevent osteoblasts degeneration in osteoporosis or other degenerative disorders.
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Affiliation(s)
- Eun Mi Choi
- Department of Food and Nutrition, Education Graduate School, Kyung Hee University, 1, Hoegi-dong, Dongdaemun-gu, Seoul, 130-701, Korea.
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Sancho-Martínez SM, Piedrafita FJ, Cannata-Andía JB, López-Novoa JM, López-Hernández FJ. Necrotic concentrations of cisplatin activate the apoptotic machinery but inhibit effector caspases and interfere with the execution of apoptosis. Toxicol Sci 2011; 122:73-85. [PMID: 21527773 DOI: 10.1093/toxsci/kfr098] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Cisplatin is a chemotherapeutic drug whose cytotoxicity is key to its therapeutic and side effects. Nephrotoxicity, mainly due to renal tubular injury, poses its most important therapeutic limitation. Tubular necrosis is derived from epithelial cell death by apoptosis and necrosis in the proximal and distal tubuli. The mode of cell death has been related to drug concentration, with necrosis occurring with high concentrations and apoptosis with lower concentrations. To fully understand the toxic effects of cisplatin to potentially improve its pharmaco-toxicological profile, it is necessary to unravel the cellular events and signaling pathways implicated in the appearance of both modes of cell death. We used cultured human lymphoma and renal tubule cells to investigate the biochemical and phenotypic characteristics of the death mode induced by increasing concentrations of cisplatin. Our results indicate that pronecrotic concentrations of cisplatin early activate the apoptotic machinery, which is in turn directly blocked by cisplatin at the level of effector caspases. Aborted apoptosis induces a death phenotype lacking some typical characteristics of this process, which more closely resembles necrosis. Furthermore, unidentified Bcl-2- and mitochondria-independent pathways are induced by pronecrotic and not by proapoptotic concentrations of cisplatin. Cisplatin-induced cell necrosis is the result of an aborted apoptosis at the level of effector caspases. Yet, Bcl-2-independent effects lead to cell death, which may pose potential targets for pharmacological intervention aimed at reducing cisplatin nephrotoxicity.
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Affiliation(s)
- Sandra M Sancho-Martínez
- Unidad de Fisiopatología Renal y Cardiovascular, Departamento de Fisiología y Farmacología, Universidad de Salamanca, Salamanca, Spain
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Abstract
Since the early studies on the resolution and reconstitution of the oxidative phosphorylation system from animal mitochondria, coupling factor B was recognized as an essential component of the machinery responsible for energy-driven ATP synthesis. At the phenomenological level, factor B was agreed to lie at the interface of energy transfer between the respiratory chain and the ATP synthase complex. However, biochemical characterization of the factor B polypeptide has proved difficult. It was not until 1990 that the N-terminal amino acid sequence of bovine mitochondrial factor B was reported, which followed, a decade later, by the report describing the amino acid sequence of full-length human factor B and its functional characterization. The present review summarizes the recent advances in structure-functional studies of factor B, including its recently determined crystal structure at 0.96 A resolution. Ectopic expression of human factor B in cultured animal cells has unexpectedly revealed its role in shaping mitochondrial morphology. The supramolecular assembly of ATP synthase as dimer ribbons at highly curved apices of the mitochondrial cristae was recently suggested to optimize ATP synthesis under proton-limited conditions. We propose that the binding of the ATP synthase dimers with factor B tetramers could be a means to enhance the efficiency of the terminal step of oxidative phosphorylation in animal mitochondria.
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Belogrudov GI. The proximal N-terminal amino acid residues are required for the coupling activity of the bovine heart mitochondrial factor B. Arch Biochem Biophys 2008; 473:76-87. [PMID: 18319055 DOI: 10.1016/j.abb.2008.02.022] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2008] [Revised: 02/12/2008] [Accepted: 02/16/2008] [Indexed: 11/24/2022]
Abstract
Treatment of the recombinant bovine factor B with trypsin yielded a fragment (amino acid residues 62-175) devoid of coupling activity. Removal of the N-terminal Trp2-Gly3-Trp4 peptide resulted in a significant loss of coupling activity in the FB(DeltaW)(2)(-W)(4) deletion mutant. Sucrose density gradient centrifugation demonstrated co-sedimentation of recombinant factor B with the ADP/ATP carrier, which is present in preparations of H(+)-translocating F(0)F(1)-ATPase, but not in preparations of complex V. The N-terminally truncated factor B mutant FB(DeltaW)(2)(-W)(4) did not co-sediment with the ADP/ATP carrier. Recombinant factor B co-sedimented with partially purified membrane sector F(0), extracted from F(1)-stripped bovine submitochondrial particles with n-dodecyl-beta-d-maltoside. Factor B inhibited the passive proton conductance catalyzed by F(0) reconstituted into asolectin liposomes. A factor B mutant, bearing a photoreactive unnatural amino acid pbenzoyl-l-phenylalanine (pBpa) substituted for Trp2, cross-linked with F(0) subunits e and g as well as the ADP/ATP carrier. These results suggest that the N-terminal domain and, in particular, the proximal N-terminal amino acids are important for the coupling activity and protein-protein interactions of bovine factor B.
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Affiliation(s)
- Grigory I Belogrudov
- Department of Physiology, David Geffen School of Medicine, University of California at Los Angeles, VA Greater Los Angeles Healthcare System, Rm. 324, Los Angeles, CA 90073, USA.
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Peluso JJ, Liu X, Romak J. Progesterone maintains basal intracellular adenosine triphosphate levels and viability of spontaneously immortalized granulosa cells by promoting an interaction between 14-3-3sigma and ATP synthase beta/precursor through a protein kinase G-dependent mechanism. Endocrinology 2007; 148:2037-44. [PMID: 17303654 DOI: 10.1210/en.2006-1603] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The present studies were designed to 1) describe changes in both the mitochondrial membrane potential and ATP content of spontaneously immortalized granulosa cells as they undergo apoptosis, 2) identify some of the downstream events that are activated by progesterone (P4), and 3) relate these downstream events to changes in mitochondrial function and apoptotic cell death. These studies revealed that in response to serum deprivation, the mitochondrial membrane potential initially hyperpolarizes and ATP content increases. That this increase in ATP is required for apoptosis was demonstrated by the finding that oligomycin inhibited the increase in ATP and apoptosis. Piridoxalphosphate-6-azopeyl-2'-4'-disulfonic acid, an inhibitor of purinergic receptors, which are activated by ATP, also inhibited apoptosis due to serum withdrawal. This study provides additional support for ATP's causative role in apoptosis. Moreover, 8-Br-cGMP, a protein kinase G (PKG) activator, mimicked P4's action, whereas a PKG antagonist, DT-3, attenuated P4's suppressive effect on ATP and apoptosis. Finally, DT-3 treatment was shown to attenuate P4-regulated phosphorylation of 14-3-3sigma and its binding partner, ATP synthasebeta/precursor and the amount of ATP synthasebeta/precursor that bound to 14-3-3sigma. Based on these data, it is proposed that P4 prevents apoptosis in part by activating PKG, which in turn maintains the interaction between ATP synthasebeta/precursor and 14-3-3sigma. In the absence of P4-induced PKG activity, we further propose that some ATP synthasebeta precursor dissociates from 14-3-3sigma, resulting in its activation and incorporation into the ATP synthase complex, which ultimately results in an increase in ATP and apoptosis.
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Affiliation(s)
- John J Peluso
- Department of Physiology, University of Connecticut Health Center, Farmington, Connecticut 06030-1230, USA.
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17
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Iero A, Manente S, Perin G, Bragadin M. Frozen mitochondria as rapid water quality bioassay. CHEMOSPHERE 2003; 52:1115-1123. [PMID: 12820992 DOI: 10.1016/s0045-6535(02)00843-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
A rapid and relatively low cost bioassay, usable in routine screening water test has been developed modifying the beef heart mitochondria test. In our experiments, mitochondria (FM22) were frozen at -22 degrees C, instead of -80 degrees C (FM80), and their applicability and sensitivity was verified. The oxygen consumption was measured by a Clark electrode that was interfaced to a PC to collect test analysis data. Blank tests were carried out to verify the oxygen consumption linear fitting. Toxicity tests were performed using pure organic and inorganic compounds, such to verify the FM22 sensitivity. A piecewise regression, through an Excel Macro, identified the break-point in the oxygen consumption and calculated the toxicity. The IC50s of the tested compounds were calculated and ranged from 0.123 to 0.173 mg/l for heavy metals (Cd, Cr, Cu, Ni, Pb and Zn) and from 0.572 to 10.545 mg/l for organics (benzene, DMSO, DDE, endrin, dichloromethane, chlorobenzene, 1,2-dichlorobenzene and 1,3-dichlorobenzene). Water effluent samples were then tested. The FM22 gave different toxic reactions to them. Water samples were characterised for heavy metals. The FM22 bioassay had a higher sensitivity than the FM80 and a high reproducibility in the toxicity test with pure compounds. The FM22 test was a good predictor of toxicity for water samples; the bioassay is easy, low cost and rapid, then usable for routine tests.
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Affiliation(s)
- Alessandra Iero
- Department of Environmental Sciences, Dorsoduro 2137, Venezia 30123, Italy
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18
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Abstract
The heart is capable of dramatically altering its overall energy flux with minimal changes in the concentrations of metabolites that are associated with energy metabolism. This cardiac energy metabolism homeostasis is discussed with regard to the potential cytosolic control network responsible for controlling the major energy conversion pathway, oxidative phosphorylation in mitochondria. Several models for this cytosolic control network have been proposed, but a cytosolic Ca(2+) dependent parallel activation scheme for metabolism and work is consistent with most of the experimental results. That model proposes that cytosolic Ca(2+) regulates both the utilization of ATP by the work producing ATPases as well as the mitochondrial production of ATP. Recent studies have provided evidence supporting this role of cytosolic Ca(2+). These data include the demonstration that mitochondrial [Ca(2+)] can track cytosolic [Ca(2+)] and that the compartmentation of cytosolic [Ca(2+)] can facilitate this process. On the metabolic side, Ca(2+) has been shown to rapidly activate several steps in oxidative phosphorylation, including F(1)F(0)-ATPase ATP production as well as several dehydrogenases, which results in a homeostasis of mitochondrial metabolites similar to that observed in the cytosol. Numerous problems with the Ca(2+) parallel activation hypothesis remain including the lack of specific mechanisms of mitochondrial Ca(2+) transport and regulation of F(1)F(0)-ATPase, the time dependence of Ca(2+) activation of cytosolic ATPases as well as oxidative phosphorylation, and the role of cytosolic compartmentation. In addition, the lack of cytosolic or mitochondrial [Ca(2+)] measurements under in vivo conditions is problematic. Several lines of investigation to address these issues are suggested. A model of the cardiac energy metabolism control network is proposed that includes a Ca(2+) parallel activation component together with more classical elements including metabolite feedback and cytosolic compartmentation.
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Affiliation(s)
- Robert S Balaban
- Laboratory of Cardiac Energetics, National Heart Lung and Blood Institute/NIH, Building 10, Room B1 D161, Bethesda, MD 20892, USA.
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19
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Nath S. The molecular mechanism of ATP synthesis by F1F0-ATP synthase: a scrutiny of the major possibilities. ADVANCES IN BIOCHEMICAL ENGINEERING/BIOTECHNOLOGY 2002; 74:65-98. [PMID: 11991184 DOI: 10.1007/3-540-45736-4_4] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/24/2023]
Abstract
A critical goal of metabolism in living cells is the synthesis of adenosine triphosphate (ATP). ATP is synthesized by the enzyme F1F0-ATP synthase. This enzyme, the smallest-known molecular machine, couples proton translocation through its membrane-embedded, hydrophobic domain, F0, to the synthesis of ATP from adenosine diphosphate (ADP) and inorganic phosphate (Pi) in its soluble, hydrophilic headpiece, F1. Animals, plants and microorganisms all capture and utilize energy by this important chemical reaction. How does it occur? The binding change mechanism and the torsional mechanism of energy transduction and ATP synthesis are two mechanisms that have been proposed in the literature. According to the binding change mechanism (which considers reversible catalysis and site-site cooperativity), energy is required primarily for release of synthesized ATP, but not for its synthesis. On the other hand, according to the torsional mechanism (which considers an irreversible mode of catalysis and absence of cooperativity), all the elementary steps require energy, and the ion-protein interaction energy obtained from the ion gradients is used to synthesize ATP, for Pi binding, and for straining the beta-epsilon bond in order to enable ADP to bind. The energy to release preformed ATP from the tight catalytic site (betaDP) is provided by the formation of the beta-epsilon ester linkage. First, the central features of these mechanisms are clearly delineated. Then, a critical scrutiny of these mechanisms is undertaken. The predictions of the torsional mechanism are listed. In particular, how the torsional mechanism deals with the specific difficulties associated with other mechanisms, and how it seeks to explain a wealth of structural, spectroscopic, and biochemical data is discussed in detail. Recent experimental data in support of the mechanism are presented. Finally, in view of the molecular machine nature of energy transduction, the indispensability of applying engineering tools at the molecular level is highlighted. This paves the way for the development of a new field: Molecular Physiological Engineering.
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Affiliation(s)
- Sunil Nath
- Department of Biochemical Engineering and Biotechnology, Indian Institute of Technology, Hauz Khas, New Delhi.
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20
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Buntinas L, Gunter KK, Sparagna GC, Gunter TE. The rapid mode of calcium uptake into heart mitochondria (RaM): comparison to RaM in liver mitochondria. BIOCHIMICA ET BIOPHYSICA ACTA 2001; 1504:248-61. [PMID: 11245789 DOI: 10.1016/s0005-2728(00)00254-1] [Citation(s) in RCA: 114] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
A mechanism of Ca(2+) uptake, capable of sequestering significant amounts of Ca(2+) from cytosolic Ca(2+) pulses, has previously been identified in liver mitochondria. This mechanism, the Rapid Mode of Ca(2+) uptake (RaM), was shown to sequester Ca(2+) very rapidly at the beginning of each pulse in a sequence [Sparagna et al. (1995) J. Biol. Chem. 270, 27510-27515]. The existence and properties of RaM in heart mitochondria, however, are unknown and are the basis for this study. We show that RaM functions in heart mitochondria with some of the characteristics of RaM in liver, but its activation and inhibition are quite different. It is feasible that these differences represent different physiological adaptations in these two tissues. In both tissues, RaM is highly conductive at the beginning of a Ca(2+) pulse, but is inhibited by the rising [Ca(2+)] of the pulse itself. In heart mitochondria, the time required at low [Ca(2+)] to reestablish high Ca(2+) conductivity via RaM i.e. the 'resetting time' of RaM is much longer than in liver. RaM in liver mitochondria is strongly activated by spermine, activated by ATP or GTP and unaffected by ADP and AMP. In heart, RaM is activated much less strongly by spermine and unaffected by ATP or GTP. RaM in heart is strongly inhibited by AMP and has a biphasic response to ADP; it is activated at low concentrations and inhibited at high concentrations. Finally, an hypothesis consistent with the data and characteristics of liver and heart is presented to explain how RaM may function to control the rate of oxidative phosphorylation in each tissue. Under this hypothesis, RaM functions to create a brief, high free Ca(2+) concentration inside mitochondria which may activate intramitochondrial metabolic reactions with relatively small amounts of Ca(2+) uptake. This hypothesis is consistent with the view that intramitochondrial [Ca(2+)] may be used to control the rate of ADP phosphorylation in such a way as to minimize the probability of activating the Ca(2+)-induced mitochondrial membrane permeability transition (MPT).
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Affiliation(s)
- L Buntinas
- Department of Biochemistry and Biophysics, University of Rochester, School of Medicine and Dentistry, Rochester, NY 14642, USA.
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21
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Beharry S, Bragg PD. Properties of bound inorganic phosphate on bovine mitochondrial F1F0-ATP synthase. J Bioenerg Biomembr 2001; 33:35-42. [PMID: 11460924 DOI: 10.1023/a:1005620606871] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Beef-heart mitochondrial F1F0-ATP synthase contained six molecules of bound inorganic phosphate (Pi). This phosphate exchanged completely with exogenous 32Pi when the enzyme was exposed to 30% (v/v) dimethyl sulfoxide (DMSO) and then returned to a DMSO-free buffer (Beharry and Bragg 2001). Only two molecules were replaced by 32Pi when the enzyme was not pretreated with DMSO. These two molecules of 32Pi were not displaced from the enzyme by the treatment with 1 mM ATP. Similarly, two molecules of bound 32Pi remained on the DMSO-pretreated enzyme following addition of ATP, that is, four molecules of 32Pi were displaced by ATP. The ATP-resistant 32Pi was removed from the enzyme by pyrophosphate. It is proposed that these molecules of 32Pi are bound at an unfilled adenine nucleotide-binding noncatalytic site on the enzyme. Brief exposure of the enzyme loaded with two molecules of 32Pi to DMSO, followed by removal of the DMSO, resulted in the loss of the bound 32Pi and in the formation of two molecules of bound ATP from exogenous ADP. A third catalytic site on the enzyme was occupied by ATP, which could undergo a Pi <--> ATP exchange reaction with bound Pi. The presence of two catalytic sites containing bound Pi is consistent with the X-ray crystallographic structure of F1 (Bianchet, et al., 1998). Thus, five of the six molecules of bound Pi were accounted for. Three molecules of bound Pi were at catalytic sites and participated in ATP synthesis or Pi <--> ATP exchange. Two other molecules of bound Pi were present at a noncatalytic adenine nucleotide-binding site. The location and role of the remaining molecule of bound Pi remains to be established. We were unable to demonstrate, using chemical modification of sulfhydryl groups by iodoacetic acid, any gross difference in the conformation of F1F0 in DMSO-containing compared with DMSO-free buffers.
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Affiliation(s)
- S Beharry
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, Canada
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22
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Beharry S, Bragg PD. Phosphate exchange and ATP synthesis by DMSO-pretreated purified bovine mitochondrial ATP synthase. Biochem J 2001; 353:215-22. [PMID: 11139383 PMCID: PMC1221561 DOI: 10.1042/0264-6021:3530215] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Purified soluble bovine mitochondrial F(1)F(o)-ATP synthase contained 2 mol of ATP, 2 mol of ADP and 6 mol of P(i)/mol. Incubation of this enzyme with 1 mM [(32)P]P(i) caused the exchange of 2 mol of P(i)/mol of F(1)F(o)-ATP synthase. The labelled phosphates were not displaced by ATP. Transfer of F(1)F(o)-ATP synthase to a buffer containing 30% (v/v) DMSO and 1 mM [(32)P]P(i) resulted in the loss of bound nucleotides with the retention of 1 mol of ATP/mol of F(1)F(o)-ATP synthase. Six molecules of [(32)P]P(i) were incorporated by exchange with the existing bound phosphate. Removal of the DMSO by passage of the enzyme through a centrifuged column of Sephadex G-50 resulted in the exchange of one molecule of bound [(32)P]P(i) into the bound ATP. Azide did not prevent this [(32)P]P(i)<-->ATP exchange reaction. The bound labelled ATP could be displaced from the enzyme by exogenous ATP. Addition of ADP to the DMSO-pretreated F(1)F(o)-ATP synthase in the original DMSO-free buffer resulted in the formation of an additional molecule of bound ATP. It was concluded that following pretreatment with and subsequent removal of DMSO the F(1)F(o)-ATP synthase contained one molecule of ATP at a catalytic site which was competent to carry out a phosphate-ATP exchange reaction using enzyme-bound inorganic radiolabelled phosphate. In the presence of ADP an additional molecule of labelled ATP was formed from enzyme-bound P(i) at a second catalytic site. The bound phosphate-ATP exchange reaction is not readily accommodated by current mechanisms for the ATP synthase.
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Affiliation(s)
- S Beharry
- Department of Biochemistry and Molecular Biology, University of British Columbia, 2146 Health Sciences Mall, Vancouver, BC, Canada V6T 1Z3
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23
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Response. Nat Cell Biol 2000; 2:E172-3. [PMID: 11025672 DOI: 10.1038/35036418] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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24
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Weber J, Senior AE. ATP synthase: what we know about ATP hydrolysis and what we do not know about ATP synthesis. BIOCHIMICA ET BIOPHYSICA ACTA 2000; 1458:300-9. [PMID: 10838046 DOI: 10.1016/s0005-2728(00)00082-7] [Citation(s) in RCA: 130] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
In ATP synthase, X-ray structures, demonstration of ATP-driven gamma-subunit rotation, and tryptophan fluorescence techniques to determine catalytic site occupancy and nucleotide binding affinities have resulted in pronounced progress in understanding ATP hydrolysis, for which a mechanism is presented here. In contrast, ATP synthesis remains enigmatic. The molecular mechanism by which ADP is bound in presence of a high ATP/ADP concentration ratio is a fundamental unknown; similarly P(i) binding is not understood. Techniques to measure catalytic site occupancy and ligand binding affinity changes during net ATP synthesis are much needed. Relation of these parameters to gamma-rotation is a further goal. A speculative model for ATP synthesis is offered.
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Affiliation(s)
- J Weber
- Department of Biochemistry and Biophysics, Box 712, University of Rochester Medical Center, Rochester, NY 14642, USA
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25
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Herzig RP, Scacco S, Scarpulla RC. Sequential serum-dependent activation of CREB and NRF-1 leads to enhanced mitochondrial respiration through the induction of cytochrome c. J Biol Chem 2000; 275:13134-41. [PMID: 10777619 DOI: 10.1074/jbc.275.17.13134] [Citation(s) in RCA: 141] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Progression through the cell cycle requires ATP for protein synthesis, cytoskeletal rearrangement, chromatin remodeling, and protein degradation. The mechanisms by which mammalian cells increase respiratory capacity and ATP production in preparation for cell division are largely unexplored. Here, we demonstrate that serum induction of cytochrome c mRNA and processed protein in quiescent BALB/3T3 fibroblasts is associated with a marked increase in mitochondrial respiration. Cytochrome c was induced in the absence of any increase in citrate synthase activity or in subunit IV of the cytochrome c oxidase complex mRNA or protein, indicating that the enhanced respiratory rate did not require a general increase in mitochondrial biogenesis or respiratory chain expression. Transfections with a series of cytochrome c promoter mutants showed that both nuclear respiratory factor 1 (NRF-1) and cAMP-response element-binding protein (CREB) binding sites contributed equally to induced expression by serum. Moreover, CREB and NRF-1 were phosphorylated sequentially in response to serum, and the NRF-1 phosphorylation was accompanied by an increase in its ability to trans-activate target gene expression. The results demonstrate that the differential transcriptional expression of cytochrome c, through sequential transcription factor phosphorylations, leads to enhanced mitochondrial respiratory capacity upon serum-induced entry to the cell cycle.
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Affiliation(s)
- R P Herzig
- Department of Cell and Molecular Biology, Northwestern Medical School, Chicago, Illinois 60611, USA
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26
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Ren H, Allison WS. Substitution of betaGlu(201) in the alpha(3)beta(3)gamma subcomplex of the F(1)-ATPase from the thermophilic Bacillus PS3 increases the affinity of catalytic sites for nucleotides. J Biol Chem 2000; 275:10057-63. [PMID: 10744684 DOI: 10.1074/jbc.275.14.10057] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In the crystal structure of bovine mitochondrial F(1)-ATPase (MF(1)) (Abrahams, J. P., Leslie, A. G. W., Lutter, R., and Walker, J. E. (1994) Nature 370, 621-628), the side chain oxygen of betaThr(163) interacts directly with Mg(2+) coordinated to 5'-adenylyl beta, gamma-imidodiphosphate or ADP bound to catalytic sites of beta subunits present in closed conformations. In the unliganded beta subunit present in an open conformation, the hydroxyl of betaThr(163) is hydrogen-bonded to the carboxylate of betaGlu(199). Substitution of betaGlu(201) (equivalent to betaGlu(199) in MF(1)) in the alpha(3)beta(3)gamma subcomplex of the F(1)-ATPase from the thermophilic Bacillus PS3 with cysteine or valine increases the propensity to entrap inhibitory MgADP in a catalytic site during hydrolysis of 50 microM ATP. These substitutions lower K(m3) (the Michaelis constant for trisite ATP hydrolysis) relative to that of the wild type by 25- and 10-fold, respectively. Fluorescence quenching of alpha(3)(betaE201C/Y341W)(3)gamma and alpha(3)(betaY341W)(3)gamma mutant subcomplexes showed that MgATP and MgADP bind to the third catalytic site of the double mutant with 8.4- and 4.4-fold higher affinity, respectively, than to the single mutant. These comparisons support the hypothesis that the hydrogen bond observed between the side chains of betaThr(163) and betaGlu(199) in the unliganded catalytic site in the crystal structure of MF(1) stabilizes the open conformation of the catalytic site during ATP hydrolysis.
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Affiliation(s)
- H Ren
- Department of Chemistry and Biochemistry, University of California at San Diego, La Jolla, California 92093-0506, USA
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27
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Baracca A, Barogi S, Carelli V, Lenaz G, Solaini G. Catalytic activities of mitochondrial ATP synthase in patients with mitochondrial DNA T8993G mutation in the ATPase 6 gene encoding subunit a. J Biol Chem 2000; 275:4177-82. [PMID: 10660580 DOI: 10.1074/jbc.275.6.4177] [Citation(s) in RCA: 82] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We investigated the biochemical phenotype of the mtDNA T8993G point mutation in the ATPase 6 gene, associated with neurogenic muscle weakness, ataxia, and retinitis pigmentosa (NARP), in three patients from two unrelated families. All three carried >80% mutant genome in platelets and were manifesting clinically various degrees of the NARP phenotype. Coupled submitochondrial particles prepared from platelets capable of succinate-sustained ATP synthesis were studied using very sensitive and rapid luminometric and fluorescence methods. A sharp decrease (>95%) in the succinate-sustained ATP synthesis rate of the particles was found, but both the ATP hydrolysis rate and ATP-driven proton translocation (when the protons flow from the matrix to the cytosol) were minimally affected. The T8993G mutation changes the highly conserved residue Leu(156) to Arg in the ATPase 6 subunit (subunit a). This subunit, together with subunit c, is thought to cooperatively catalyze proton translocation and rotate, one with respect to the other, during the catalytic cycle of the F(1)F(0) complex. Our results suggest that the T8993G mutation induces a structural defect in human F(1)F(0)-ATPase that causes a severe impairment of ATP synthesis. This is possibly due to a defect in either the vectorial proton transport from the cytosol to the mitochondrial matrix or the coupling of proton flow through F(0) to ATP synthesis in F(1). Whatever mechanism is involved, this leads to impaired ATP synthesis. On the other hand, ATP hydrolysis that involves proton flow from the matrix to the cytosol is essentially unaffected.
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Affiliation(s)
- A Baracca
- Dipartimento di Biochimica, Università di Bologna, 48026 Bologna, Italy
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28
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Curti C, Mingatto FE, Polizello AC, Galastri LO, Uyemura SA, Santos AC. Fluoxetine interacts with the lipid bilayer of the inner membrane in isolated rat brain mitochondria, inhibiting electron transport and F1F0-ATPase activity. Mol Cell Biochem 1999; 199:103-9. [PMID: 10544958 DOI: 10.1023/a:1006912010550] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The effects of fluoxetine on the oxidative phosphorylation of mitochondria isolated from rat brain and on the kinetic properties of submitochondrial particle F1F0-ATPase were evaluated. The state 3 respiration rate supported by pyruvate + malate, succinate, or ascorbate + tetramethyl-p-phenylenediamine (TMPD) was substantially decreased by fluoxetine. The IC50 for pyruvate + malate oxidation was approximately 0.15 mM and the pattern of inhibition was the typical one of the electron-transport inhibitors, in that the drug inhibited both ADP- and carbonyl cyanide m-chlorophenylhydrazone (CCCP)-stimulated respirations and the former inhibition was not released by the uncoupler. Fluoxetine also decreased the activity of submitochondrial particle F1F0-ATPase (IC50 approximately 0.08 mM) even though K0.5 and activity of Triton X-100 solubilized enzyme were not changed substantially. As a consequence of these effects, fluoxetine decreased the rate of ATP synthesis and depressed the phosphorylation potential of mitochondria. Incubation of mitochondria or submitochondrial particles with fluoxetine under the conditions of respiration or F1F0-ATPase assays, respectively, caused a dose-dependent enhancement of 1-anilino-8-naphthalene sulfonate (ANS) fluorescence. These results show that fluoxetine indirectly and nonspecifically affects electron transport and F1F0)-ATPase activity inhibiting oxidative phosphorylation in isolated rat brain mitochondria. They suggest, in addition, that these effects are mediated by the drug interference with the physical state of lipid bilayer of inner mitochondrial membrane.
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Affiliation(s)
- C Curti
- Department of Physics and Chemistry, School of Pharmaceutical Sciences, University of São Paulo, Brasil
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29
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Abstract
Studies using in vivo imaging or microscopic analysis of autopsy specimens indicate abnormalities in the striatum of schizophrenics including lower striatal metabolism, a change which can be normalized by antipsychotic medication. To investigate the possibility that abnormalities in schizophrenia brain may be due, in part, to pathology in mitochondria, organelles which generate energy, postmortem brain tissue from schizophrenic and control cases was obtained from the Maryland Brain Collection. Mitochondria in electron micrographs of striatal neuropil were counted and digitized. The caudate and the putamen of the schizophrenic subjects contained significantly (P < 0.05) fewer (a decrease of approximately 20%) mitochondrial profiles throughout the neuropil than did normal controls. The numbers of mitochondrial profiles per axon terminal appeared lower in the subset of schizophrenics off-drug as compared to either the subset of schizophrenics on-drug or to controls, suggesting that neuroleptic treatment may normalize this measure. The structural integrity of mitochondrial profiles in the schizophrenic striata was not obviously different from that of controls. Fewer mitochondrial profiles suggest decreased energy demands or diminished capacity to respond to energy requirements in the structures that contain them. These data are consistent with other studies showing decreased metabolism in the striatum of schizophrenics and may identify, in part, the anatomical basis of this deficit.
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Affiliation(s)
- L Kung
- Maryland Psychiatric Research Center, Department of Psychiatry, University of Maryland School of Medicine, Baltimore 21228, USA
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30
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Vázquez-Memije ME, Shanske S, Santorelli FM, Kranz-Eble P, DeVivo DC, DiMauro S. Comparative biochemical studies of ATPases in cells from patients with the T8993G or T8993C mitochondrial DNA mutations. J Inherit Metab Dis 1998; 21:829-36. [PMID: 9870208 DOI: 10.1023/a:1005418718299] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
We performed comparative biochemical studies in cultured fibroblast mitochondria from patients with the T8993G or the T8993C point mutations in the ATPase 6 gene of mitochondrial DNA. We found that ATP production was much more severely decreased in cells from patients with the T8993G mutation than in those from patients with the T8993C mutation. Kinetic studies suggest that both mutations affect only the F0 sector of the mitochondrial ATPase complex. We conclude that these two mutations, which result in the substitution of different amino acids at the same site of the ATPase, result in an enzyme with different biochemical characteristics.
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Affiliation(s)
- M E Vázquez-Memije
- Unidad de Investigación en Genética Humana, Hospital de Pediatría, Centro Médico Nacional-IMSS, México, D.F
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31
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Cammack R, Shergill JK, Ananda Inalsingh V, Hughes MN. Applications of electron paramagnetic resonance spectroscopy to study interactions of iron proteins in cells with nitric oxide. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 1998; 54A:2393-2402. [PMID: 9974226 DOI: 10.1016/s1386-1425(98)00219-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Nitric oxide and species derived from it have a wide range of biological functions. Some applications of electron paramagnetic resonance (EPR) spectroscopy are reviewed, for observing nitrosyl species in biological systems. Nitrite has long been used as a food preservative owing to its bacteriostatic effect on spoilage bacteria. Nitrosyl complexes such as sodium nitroprusside, which are added experimentally as NO-generators, themselves produce paramagnetic nitrosyl species, which may be seen by EPR. We have used this to observe the effects of nitroprusside on clostridial cells. After growth in the presence of sublethal concentrations of nitroprusside, the cells show they have been converted into other, presumably less toxic, nitrosyl complexes such as (RS)2Fe(NO)2. Nitric oxide is cytotoxic, partly due to its effects on mitochondria. This is exploited in the destruction of cancer cells by the immune system. The targets include iron-sulfur proteins. It appears that species derived from nitric oxide such as peroxynitrite may be responsible. Addition of peroxynitrite to mitochondria led to depletion of the EPR-detectable iron-sulfur clusters. Paramagnetic complexes are formed in vivo from hemoglobin, in conditions such as experimental endotoxic shock. This has been used to follow the course of production of NO by macrophages. We have examined the effects of suppression of NO synthase using biopterin antagonists. Another method is to use an injected NO-trapping agent, Fe-diethyldithiocarbamate (Fe-DETC) to detect accumulated NO by EPR. In this way we have observed the effects of depletion of serum arginine by arginase. In brains from victims of Parkinson's disease, a nitrosyl species, identified as nitrosyl hemoglobin, has been observed in substantia nigra. This is an indication for the involvement of nitric oxide or a derived species in the damage to this organ.
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Affiliation(s)
- R Cammack
- Centre for the Study of Metals in Biology and Medicine, King's College, London, UK.
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32
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Allison WS. F1-ATPase: A Molecular Motor That Hydrolyzes ATP with Sequential Opening and Closing of Catalytic Sites Coupled to Rotation of Its γ Subunit. Acc Chem Res 1998. [DOI: 10.1021/ar960257v] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- William S. Allison
- Department of Chemistry & Biochemistry, University of California at San Diego, La Jolla, California 92093-0601
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33
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Yagi T, Yano T, Di Bernardo S, Matsuno-Yagi A. Procaryotic complex I (NDH-1), an overview. BIOCHIMICA ET BIOPHYSICA ACTA 1998; 1364:125-33. [PMID: 9593856 DOI: 10.1016/s0005-2728(98)00023-1] [Citation(s) in RCA: 187] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- T Yagi
- Division of Biochemistry, Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, CA 92037, USA.
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34
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Aggeler R, Grüber G, Capaldi RA. Trapping of conformations of the Escherichia coli F1 ATPase by disulfide bond formation. A state of the enzyme with all three catalytic sites of equal and low affinity for nucleotides. FEBS Lett 1998; 426:37-40. [PMID: 9598974 DOI: 10.1016/s0014-5793(98)00306-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
A mutant of Escherichia coli F1F0-ATPase, alphaS411C/betaY331W/betaE381C/gammaC87S, has been generated. CuCl2 treatment of this mutant led to cross-linking between alpha and beta subunits in yields of up to 90%. This cross-linking across non-catalytic site interfaces inhibited ATP hydrolysis activity. In the absence of cross-linking, MgATP bound in catalytic sites of the mutant with three different affinities of 0.1 microM, 6 microM and 60 microM, respectively, values that are comparable to wild-type. For MgADP, there was one tight site (0.34 microM) and two sites of lower affinity (each 27 microM), again comparable to wild-type enzyme. After cross-linking all three catalytic sites bound MgATP or MgADP with the same relatively low affinity (approximately 60 microM). Thus cross-linking fixed all three catalytic sites in the same conformation. Trypsin cleavage experiments showed that cross-linking fixed the epsilon subunit in the ATP+EDTA conformation.
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Affiliation(s)
- R Aggeler
- Institute of Molecular Biology, University of Oregon, Eugene 97403-1229, USA
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35
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Yamaguchi M, Belogrudov GI, Hatefi Y. Mitochondrial NADH-ubiquinone oxidoreductase (Complex I). Effect of substrates on the fragmentation of subunits by trypsin. J Biol Chem 1998; 273:8094-8. [PMID: 9525911 DOI: 10.1074/jbc.273.14.8094] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
It has been shown that treatment of bovine mitochondrial complex I (NADH-ubiquinone oxidoreductase) with NADH or NADPH, but not with NAD or NADP, increases the susceptibility of a number of subunits to tryptic degradation. This increased susceptibility involved subunits that contain electron carriers, such as FMN and iron-sulfur clusters, as well as subunits that lack electron carriers. Results shown elsewhere on changes in the cross-linking pattern of complex I subunits when the enzyme was pretreated with NADH or NADPH (Belogrudov, G., and Hatefi, Y. (1994) Biochemistry 33, 4571-4576) also indicated that complex I undergoes extensive conformation changes when reduced by substrate. Furthermore, we had previously shown that in submitochondrial particles the affinity of complex I for NAD increases by >/=20-fold in electron transfer from succinate to NAD when the particles are energized by ATP hydrolysis. Together, these results suggest that energy coupling in complex I may involve protein conformation changes as a key step. In addition, it has been shown here that treatment of complex I with trypsin in the presence of NADPH, but not NADH or NAD(P), produced from the 39-kDa subunit a 33-kDa degradation product that resisted further hydrolysis. Like the 39-kDa subunit, the 33-kDa product bound to a NADP-agarose affinity column, and could be eluted with a buffer containing NADPH. It is possible that together with the acyl carrier protein of complex I the NADP(H)-binding 39-kDa subunit is involved in intramitochondrial fatty acid synthesis.
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Affiliation(s)
- M Yamaguchi
- Division of Biochemistry, Department of Molecular and Experimental Medicine, The Scripps Research Institute, La Jolla, California 92037, USA
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36
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Chi TB, Brown B SV, Williams N. Subunit 9 of the mitochondrial ATP synthase of Trypanosoma brucei is nuclearly encoded and developmentally regulated. Mol Biochem Parasitol 1998; 92:29-38. [PMID: 9574907 DOI: 10.1016/s0166-6851(97)00222-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
We have previously shown that the mitochondrial ATP synthase is developmentally regulated through the life cycle of Trypanosoma brucei. The mechanism of this regulation is as yet unknown. We are currently examining regulation of expression of several key subunits of the ATP synthase to investigate this mechanism. In the work presented here, we have cloned, sequenced, and confirmed the identity of the ATPase subunit 9 homologue from T. brucei. The ATPase subunit 9 gene that we have identified from T. brucei has between 40 and 600% identity with subunit 9 from a variety of organisms. This gene possesses a putative mitochondrial import sequence at the N terminus of the encoded protein sequence. The protein expressed from this gene by in vitro transcription/translation comigrates with native protein isolated from inner mitochondrial membrane vesicles from T. brucei. We have shown that the cDNA identifies a copy of this gene in the nuclear genome, but does not identify a similar gene in kinetoplast DNA (kDNA) prepared from T. brucei. This gene does not show homology to any published sequence data from maxicircle DNA or edited maxicircle derived sequences. Steady state transcripts of a single size have been identified by Northern analysis and demonstrate significant developmental regulation through the T. brucei life cycle. Northern analysis and quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) results show that the transcript is 10-14-fold higher in procyclic form than in early and late bloodstream forms.
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Affiliation(s)
- T B Chi
- Department of Microbiology, State University of New York at Buffalo, 14214, USA
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37
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Knowles AF, Penefsky HS. Reconstitution of beef heart mitochondrial F0F1 in reverse phase evaporation vesicles. BIOCHIMICA ET BIOPHYSICA ACTA 1997; 1329:311-20. [PMID: 9371423 DOI: 10.1016/s0005-2736(97)00123-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Beef heart mitochondrial F0F1 was reconstituted in proteoliposomes by a new procedure. MF0F1 was inserted in preformed reverse phase evaporation vesicles of large diameters prepared from asolectin (MF0F1-REV). Reconstitution was mediated by Triton X-100, which was subsequently removed by treatment with Bio-Beads. Parameters which resulted in optimal reconstitution were described. The MF0F1-REV proteoliposomes catalyzed an exchange between Pi and ATP and were capable of proton pumping. Both reactions were inhibited by oligomycin and uncoupler of oxidative phosphorylation. The range of Pi-ATP exchange activity of the proteoliposomes (70-110 nmol min[-1] mg[-1]) compared favorably with activities obtained in vesicles reconstituted by cholate dialysis or cholate dilution. The most important aspect of this method is that, unlike other reconstitution methods, exogenous F1 and other coupling factors are not required to obtain high Pi-ATP exchange activity by MF0F1-REV. This simple and rapid reconstitution procedure should be useful for future studies dealing with functional analysis of MF0F1.
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Affiliation(s)
- A F Knowles
- Department of Biochemistry and Molecular Biology, SUNY Health Science Center, Syracuse, NY 13210, USA.
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38
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Grüber G, Hausrath A, Sagermann M, Capaldi RA. An improved purification of ECF1 and ECF1F0 by using a cytochrome bo-deficient strain of Escherichia coli facilitates crystallization of these complexes. FEBS Lett 1997; 410:165-8. [PMID: 9237622 DOI: 10.1016/s0014-5793(97)00528-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
A novel strategy, which employs a cytochrome bo-lacking strain (GO104) and a modified isolation procedure provides an effective approach for obtaining much purer preparations of ECF1F0 than described previously, as well as for isolating homogeneous and protein-chemically pure ECF1. ECF1 obtained in this way could be crystallized by vapor-diffusion using polyethylene glycol (PEG) as a precipitant in a form suitable for X-ray diffraction analysis. The crystals belong to the orthorhombic space group P2(1)2(1)2(1), with lattice parameters a = 110, h = 134, and c = 269 A, and diffract to a resolution of at least 6.4 A.
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Affiliation(s)
- G Grüber
- Institute of Molecular Biology, University of Oregon, Eugene 97403-1229, USA
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39
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Abstract
The structure of the core catalytic unit of ATP synthase, alpha 3 beta 3 gamma, has been determined by X-ray crystallography, revealing a roughly symmetrical arrangement of alternating alpha and beta subunits around a central cavity in which helical portions of gamma are found. A low-resolution structural model of F0, based on electron spectroscopic imaging, locates subunit a and the two copies of subunit b outside of a subunit c oligomer. The structures of individual subunits epsilon and c (largely) have been solved by NMR spectroscopy, but the oligomeric structure of c is still unknown. The structures of subunits a and delta remain undefined, that of b has not yet been defined but biochemical evidence indicates a credible model. Subunits gamma, epsilon, b, and delta are at the interface between F1 and F0; gamma epsilon complex forms one element of the stalk, interacting with c at the base and alpha and beta at the top. The locations of b and delta are less clear. Elucidation of the structure F0, of the stalk, and of the entire F1F0 remains a challenging goal.
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Affiliation(s)
- J Weber
- Department of Biochemistry, University of Rochester Medical Center, NY 14642, USA
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40
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Affiliation(s)
- P Dimroth
- Mikrobiologisches Institut, Eidgenössische Technische Hochschule, Zürich, Switzerland
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41
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Abstract
An X-ray structure of the F1 portion of the mitochondrial ATP synthase shows asymmetry and differences in nucleotide binding of the catalytic beta subunits that support the binding change mechanism with an internal rotation of the gamma subunit. Other structural and mutational probes of the F1 and F0 portions of the ATP synthase are reviewed, together with kinetic and other evaluations of catalytic site occupancy and behavior during hydrolysis or synthesis of ATP. Subunit function as related to proton translocation and rotational catalysis is considered. Physical demonstrations of the gamma subunit rotation have been achieved. The findings have implications for other enzymatic catalyses.
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Affiliation(s)
- P D Boyer
- Molecular Biology Institute, University of California, Los Angeles 90095-1570, USA
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42
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Jault JM, Dou C, Grodsky NB, Matsui T, Yoshida M, Allison WS. The alpha3beta3gamma subcomplex of the F1-ATPase from the thermophilic bacillus PS3 with the betaT165S substitution does not entrap inhibitory MgADP in a catalytic site during turnover. J Biol Chem 1996; 271:28818-24. [PMID: 8910526 DOI: 10.1074/jbc.271.46.28818] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
The hydrolytic properties of the mutant alpha3(betaT165S)3gamma and wild-type alpha3beta3gamma subcomplexes of TF1 have been compared. Whereas the wild-type complex hydrolyzes 50 microM ATP in three kinetic phases, the mutant complex hydrolyzes 50 microM ATP with a linear rate. After incubation with a slight excess of ADP in the presence of Mg2+, the wild-type complex hydrolyzes 2 mM ATP with a long lag. In contrast, prior incubation of the mutant complex under these conditions does not affect the kinetics of ATP hydrolysis. The ATPase activity of the wild-type complex is stimulated 4-fold by 0. 1% lauryl dimethylamine oxide, whereas this concentration of lauryl dimethylamine oxide inhibits the mutant complex by 25%. Compared with the wild-type complex, the activity of the mutant complex is much less sensitive to turnover-dependent inhibition by azide. This comparison suggests that the mutant complex does not entrap substantial inhibitory MgADP in a catalytic site during turnover, which is supported by the following observations. ATP hydrolysis catalyzed by the wild-type complex is progressively inhibited by increasing concentrations of Mg2+ in the assay medium, whereas the mutant complex is insensitive to increasing concentrations of Mg2+. A Lineweaver-Burk plot constructed from rates of hydrolysis of 20-2000 microM ATP by the wild-type complex is biphasic, exhibiting apparent Km values of 30 microM and 470 microM with corresponding kcat values of 26 and 77 s-1. In contrast, a Lineweaver-Burk plot for the mutant complex is linear in this range of ATP concentration, displaying a Km of 133 microM and a kcat of 360 s-1.
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Affiliation(s)
- J M Jault
- Department of Chemistry and Biochemistry, School of Medicine, University of California at San Diego, La Jolla, California 92093-0601, USA.
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43
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Clark-Walker GD, Chen XJ. A vital function for mitochondrial DNA in the petite-negative yeast Kluyveromyces lactis. MOLECULAR & GENERAL GENETICS : MGG 1996; 252:746-50. [PMID: 8917319 DOI: 10.1007/bf02173982] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Petite-negative yeasts do not form viable respiratory-deficient mutants on treatment with DNA-targeting drugs that readily eliminate the mitochondrial DNA (mtDNA) from petite-positive yeasts. However, in the petite-negative yeast Kluyveromyces lactis, specific mutations in the nuclear genes MG12 and MG15 encoding the alpha- and gamma-subunits of the mitochondrial F1-ATPase, allow mtDNA to be lost. In this study we show that wild-type K. lactis does not survive in the absence of its mitochondrial genome and that the function of mgi mutations is to suppress lethality caused by loss of mtDNA. Firstly, we find that loss of a multicopy plasmid bearing a mgi allele readily occurs from a wild-type strain with functional mtDNA but is not tolerated in the absence of mtDNA. Secondly, we cloned the K. lactis homologue of the Saccharomyces cerevisiae mitochondrial genome maintenance gene MGM101, and disrupted one of the two copies in a diploid. Following sporulation, we find that segregants containing the disrupted gene form minicolonies containing 6-8000 inviable cells. By contrast, disruption of MGM101 is not lethal in a haploid mgi strain with a specific mutation in a subunit of the mitochondrial F1-ATPase. These observations suggest that mtDNA in K. lactis encodes a vital function which may reside in one of the three mitochondrially encoded subunits of Fo.
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Affiliation(s)
- G D Clark-Walker
- Molecular and Population Genetics Group, Research School of Biological Sciences, Australian National University, Canberra City, Australia
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44
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Nurani G, Franzén LG. Isolation and characterization of the mitochondrial ATP synthase from Chlamydomonas reinhardtii. cDNA sequence and deduced protein sequence of the alpha subunit. PLANT MOLECULAR BIOLOGY 1996; 31:1105-1116. [PMID: 8914527 DOI: 10.1007/bf00040828] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
We have isolated the F0F1-ATP synthase complex from oligomycin-sensitive mitochondria of the green alga Chlamydomonas reinhardtii. A pure and active ATP synthase was obtained by means of sonication, extraction with dodecyl maltoside and ion exchange and gel permeation chromatography in the presence of glycerol, DTT, ATP and PMSF [corrected]. The enzyme consists of 14 subunits as judged by SDS-PAGE. A cDNA clone encoding the ATP synthase alpha subunit has been sequenced. The deduced protein sequence contains a presequence of 45 amino acids which is not present in the mature protein. The mature protein is 58-70% identical to corresponding mitochondrial proteins from other organisms. In contrast to the ATP synthase beta subunit from C. reinhardtii (Franzen and Falk, Plant Mol Biol 19 (1992) 771-780), the protein does not have a C-terminal extension. However, the N-terminal domain of the mature protein is 15-18 residues longer than in ATP synthase alpha subunits from other organisms. Southern blot analysis indicates that the protein is encoded by a single-copy gene.
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Affiliation(s)
- G Nurani
- Department of Biochemistry, Arrhenius laboratories, Stockholm University, Sweden
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45
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Feng Z, Aggeler R, Haughton MA, Capaldi RA. Conformational changes in the Escherichia coli ATP synthase (ECF1F0) monitored by nucleotide-dependent differences in the reactivity of Cys-87 of the gamma subunit in the mutant betaGlu-381 --> Ala. J Biol Chem 1996; 271:17986-9. [PMID: 8663500 DOI: 10.1074/jbc.271.30.17986] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Cys-87, one of two intrinsic cysteines of the gamma subunit of the Escherichia coli ATP synthase (ECF1F0), is in a short segment of this subunit that binds to the bottom domain of a beta subunit close to a glutamate (Glu-381). Cys-87 was unreactive to maleimides under all conditions in wild-type ECF1 and ECF1F0 but became reactive when Glu-381 of beta was replaced by a cysteine or alanine. The reactivity of Cys-87 with maleimides was nucleotide-dependent, occurring with ATP or ADP + EDTA in catalytic sites, in the presence of AMP.PNP + Mg2+ but not with ADP + Mg2+ bound, whether Pi was present or not, and not when nucleotide binding sites were empty. Binding of N-ethylmaleimide had no effect, whereas 7-diethyl-amino-3-(4'-maleimidylphenyl)-4-methylcoumarin increased the ATPase activity of ECF1 more than 2-fold by reaction with Cys-87. In ECF1F0, these reagents inhibited activity. The nucleotide dependence of the reaction of Cys-87 of the gamma subunit depended on the presence of the epsilon subunit. In epsilon subunit-free ECF1, maleimides reacted with Cys-87 under all nucleotide conditions, including when catalytic sites were empty. These results are discussed in terms of nucleotide-dependent movements of the gamma subunit during functioning of the F1F0-type ATPase.
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Affiliation(s)
- Z Feng
- Institute of Molecular Biology, University of Oregon, Eugene, 97403-1229, USA
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46
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Grüber G, Capaldi RA. Differentiation of catalytic sites on Escherichia coli F1ATPase by laser photoactivated labeling with [3H]-2-Azido-ATP using the mutant beta Glu381Cys:epsilonSer108Cys to identify different beta subunits by their interactions with gamma and epsilon subunits. Biochemistry 1996; 35:3875-9. [PMID: 8672416 DOI: 10.1021/bi952949h] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
The ATP binding affinities of the catalytic sites in the three beta subunits of the Escherichia coli F1 ATPase (ECF1) have been explored in relation to the interaction of these subunits with the small subunits gamma and epsilon. ECF1 from the mutant beta E381C:epsilonS108C was reacted with different concentrations of [3H]-2-azido-ATP and covalent insertion of the nucleotide analogue induced by photoactivation of the azide group to a nitrene with single-pulse UV laser excitation. The enzyme showed cooperative binding of [3H]-2-azido-ATP in the presence of Mg2+. The highest affinity site was located at betafree, the one of the three beta subunits in the mutant that does not form disulfide bonds with either the gamma or the epsilon subunit. This beta subunit is, therefore, the site of unisite catalysis in the enzyme. The second mole of [3H]-2-azido-ATP to bind was located in the beta subunit that links to epsilon (betaepsilon), while the lowest affinity binding of the substrate analogue was with the beta subunit that links to gamma (betagamma). In the absence of Mg2+, all three beta subunits bound [3H]-2-azido-ATP with a similar, low affinity. The results show that binding of MgATP is determined by, and/or must determine, the interactions of the different alpha-beta subunit pairs with the single-copy subunits gamma, delta, and epsilon of the enzyme.
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Affiliation(s)
- G Grüber
- Institute of Molecular Biology, University of Oregon, Eugene, 97403-1229, USA
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47
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Pitard B, Richard P, Duñach M, Girault G, Rigaud JL. ATP synthesis by the F0F1 ATP synthase from thermophilic Bacillus PS3 reconstituted into liposomes with bacteriorhodopsin. 1. Factors defining the optimal reconstitution of ATP synthases with bacteriorhodopsin. EUROPEAN JOURNAL OF BIOCHEMISTRY 1996; 235:769-78. [PMID: 8654428 DOI: 10.1111/j.1432-1033.1996.00769.x] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Optimal conditions for the reconstitution of bacteriorhodopsin and H+-transporting ATP synthase from thermophilic Bacillus PS3 (TF0F1) were determined. Phosphatidylcholine/phosphatidic acid liposomes prepared by reverse-phase evaporation were treated with various amounts of Triton X-100, octyl glucoside, octaethylene glycol n-dodecylether, sodium cholate or sodium deoxycholate and the incorporation of proteins by these detergents was studied at each step of the solubilization process. After removal of detergent by means of SM-2 Bio-Beads, the light-driven ATP synthase activities of the resulting proteoliposomes were analyzed at 40 degrees C. The nature of the detergent used for reconstitution was important for determining the mechanism of protein insertions. The most efficient reconstitutions were obtained with octyl glucoside or Triton X-100 by insertion of the proteins into detergent-saturated liposomes. The conditions for reconstitutions were further optimized with regard to functional coupling between bacteriorhodopsin and TF0F1. It was demonstrated that one of the main factors limiting the production of efficient reconstituted proteoliposomes was related to activation of the highly stable TFO-F1. Activation was accomplished by total solubilization of phospholipids and proteins in a Triton X-100/octyl glucoside mixture containing 20 mM octyl glucoside, leading to a threefold stimulation of the ATP synthase activity. Final ATP synthase activities depended greatly on the lipid/bacteriorhodopsin and the lipid/TF0F1 ratios as well as on the phospholipid used. In particular, light-driven ATP synthesis depended upon the presence of negatively charged phospholipids. Cholesterol was found to induce a fourfold increase in ATP synthase activity with a concomitant 65% decrease in the Km for ADP, suggesting that sterols can modulate catalytic events mediated by F1. Preparations obtained by this step-by-step reconstitution procedure displayed activities up to 20-fold higher (500-800 nmol ATP x min(-1) x mg TF0F1(-1) in the presence of cholesterol) than the maximal values reported in the literature for light-driven ATP synthesis TF0F1 measured under similar conditions. This study also allowed rationalization of the different parameters involved in reconstitution experiments and the present simple method is shown to be of general use for preparation of efficient proteoliposomes containing bacteriorhodopsin and choloroplast or mitochondrial F0F1-type ATP synthases.
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Affiliation(s)
- B Pitard
- Section de Bioénergétique, DBCM, CEA-Saclay, Gif sur Yvette, France
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48
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Blair A, Ngo L, Park J, Paulsen IT, Saier MH. Phylogenetic analyses of the homologous transmembrane channel-forming proteins of the F0F1-ATPases of bacteria, chloroplasts and mitochondria. MICROBIOLOGY (READING, ENGLAND) 1996; 142 ( Pt 1):17-32. [PMID: 8581162 DOI: 10.1099/13500872-142-1-17] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Sequences of the three integral membrane subunits (subunits a, b and c) of the F0 sector of the proton-translocating F-type (F0F1-) ATPases of bacteria, chloroplasts and mitochondria have been analysed. All homologous-sequenced proteins of these subunits, comprising three distinct families, have been identified by database searches, and the homologous protein sequences have been aligned and analysed for phylogenetic relatedness. The results serve to define the relationships of the members of each of these three families of proteins, to identify regions of relative conservation, and to define relative rates of evolutionary divergence. Of these three subunits, c-subunits exhibited the slowest rate of evolutionary divergence, b-subunits exhibited the most rapid rate of evolutionary divergence, and a-subunits exhibited an intermediate rate of evolutionary divergence. The results allow definition of the relative times of occurrence of specific events during evolutionary history, such as the intragenic duplication event that gave rise to large c-subunits in eukaryotic vacuolar-type ATPases after eukaryotes diverged from archaea, and the extragenic duplication of F-type ATPase b-subunits that occurred in blue-green bacteria before the advent of chloroplasts. The results generally show that the three F0 subunits evolved as a unit from a primordial set of genes without appreciable horizontal transmission of the encoding genetic information although a few possible exceptions were noted.
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Affiliation(s)
- Alan Blair
- Department of Biology, University of California at San Diego, La Jolla, CA 92093-0116, USA
| | - Linh Ngo
- Department of Biology, University of California at San Diego, La Jolla, CA 92093-0116, USA
| | - James Park
- Department of Biology, University of California at San Diego, La Jolla, CA 92093-0116, USA
| | - Ian T Paulsen
- Department of Biology, University of California at San Diego, La Jolla, CA 92093-0116, USA
| | - Milton H Saier
- Department of Biology, University of California at San Diego, La Jolla, CA 92093-0116, USA
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49
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Yen MY, Lee HC, Liu JH, Wei YH. Compensatory elevation of complex II activity in Leber's hereditary optic neuropathy. Br J Ophthalmol 1996; 80:78-81. [PMID: 8664239 PMCID: PMC505389 DOI: 10.1136/bjo.80.1.78] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
AIMS To evaluate the mitochondrial respiratory enzyme activities in blood cells of Leber's hereditary optic neuropathy (LHON) with 11778 point mutation of mitochondrial DNA. METHODS Assays for the activities of NADH-cytochrome c reductase (complex I+complex III), succinate-cytochrome c reductase (complex II+complex III), and cytochrome c oxidase (complex IV) on blood cell mitochondria of seven LHON patients and 15 normal controls. RESULTS There was no statistically significant difference in NADH-cytochrome c reductase and cytochrome c oxidase activities between LHON patients and controls, but activities of succinate-cytochrome c reductase in LHON patients was significantly elevated compared with normal controls. CONCLUSION The observations that the activity of NADH-cytochrome c reductase is normal but that of succinate-cytochrome c reductase is increased in LHON patients with 11778 point mutation of mitochondrial DNA indicate an elevation of complex II activity, which may be due to a nuclear compensatory effect for defects of the respiratory function of mitochondria.
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Affiliation(s)
- M Y Yen
- Department of Ophthalmology, Taipei Veterans General Hospital, Taiwan
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50
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Baracca A, Gabellieri E, Barogi S, Solaini G. Conformational changes of the mitochondrial F1-ATPase epsilon-subunit induced by nucleotide binding as observed by phosphorescence spectroscopy. J Biol Chem 1995; 270:21845-51. [PMID: 7665607 DOI: 10.1074/jbc.270.37.21845] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Changes in conformation of the epsilon-subunit of the bovine heart mitochondrial F1-ATPase complex as a result of nucleotide binding have been demonstrated from the phosphorescence emission of tryptophan. The triplet state lifetime shows that whereas nucleoside triphosphate binding to the enzyme in the presence of Mg2+ increases the flexibility of the protein structure surrounding the chromophore, nucleoside diphosphate acts in an opposite manner, enhancing the rigidity of this region of the macromolecule. Such changes in dynamic structure of the epsilon-subunit are evident at high ligand concentration added to both the nucleotide-depleted F1 (Nd-F1) and the F1 preparation containing the three tightly bound nucleotides (F1(2,1)). Since the effects observed are similar in both the F1 forms, the binding to the low affinity sites must be responsible for the conformational changes induced in the epsilon-subunit. This is partially supported by the observation that the Trp lifetime is not significantly affected by adding an equimolar concentration of adenine nucleotide to Nd-F1. The effects on protein structure of nucleotide binding to either catalytic or noncatalytic sites have been distinguished by studying the phosphorescence emission of the F1 complex prepared with the three noncatalytic sites filled and the three catalytic sites vacant (F1(3,0)). Phosphorescence lifetime measurements on this F1 form demonstrate that the binding of Mg-NTP to catalytic sites induces a slight enhancement of the rigidity of the epsilon-subunit. This implies that the binding to the vacant noncatalytic site of F1(2,1) must exert the opposite and larger effect of enhancing the flexibility of the protein structure observed in both Nd-F1 and F1(2,1). The observation that enhanced flexibility of the protein occurs upon addition of adenine nucleotides to F1(2,1) in the absence of Mg2+ provides direct support for this suggestion. The connection between changes in structure and the possible functional role of the epsilon-subunit is discussed.
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Affiliation(s)
- A Baracca
- Dipartimento di Biochimica G. Moruzzi, Università di Bologna, Italy
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