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Nehme H, Ayde H, El Obeid D, Sabatier JM, Fajloun Z. Potential Inhibitory Effect of Apis mellifera's Venom and of Its Two Main Components-Melittin and PLA 2-on Escherichia coli F 1F 0-ATPase. Antibiotics (Basel) 2020; 9:E824. [PMID: 33218209 DOI: 10.3390/antibiotics9110824] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2020] [Revised: 11/12/2020] [Accepted: 11/17/2020] [Indexed: 01/16/2023] Open
Abstract
Bacterial resistance has become a worrying problem for human health, especially since certain bacterial strains of Escherichia coli (E. coli) can cause very serious infections. Thus, the search for novel natural inhibitors with new bacterial targets would be crucial to overcome resistance to antibiotics. Here, we evaluate the inhibitory effects of Apis mellifera bee venom (BV-Am) and of its two main components -melittin and phospholipase A2 (PLA2)- on E. coli F1F0-ATPase enzyme, a crucial molecular target for the survival of these bacteria. Thus, we optimized a spectrophotometric method to evaluate the enzymatic activity by quantifying the released phosphate from ATP hydrolysis catalyzed by E. coli F1F0-ATPase. The protocol developed for inhibition assays of this enzyme was validated by two reference inhibitors, thymoquinone (IC50 = 57.5 μM) and quercetin (IC50 = 30 μM). Results showed that BV-Am has a dose-dependent inhibitory effect on E. coli F1F0-ATPase with 50% inhibition at 18.43 ± 0.92 μg/mL. Melittin inhibits this enzyme with IC50 = 9.03 ± 0.27 µM, emphasizing a more inhibitory effect than the two previous reference inhibitors adopted. Likewise, PLA2 inhibits E. coli F1F0-ATPase with a dose-dependent effect (50% inhibition at 2.11 ± 0.11 μg/mL) and its combination with melittin enhanced the inhibition extent of this enzyme. Crude venom and mainly melittin and PLA2, inhibit E. coli F1F0-ATPase and could be considered as important candidates for combating resistant bacteria.
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Hiramatsu N, Chiang K, Aivati C, Rodvold JJ, Lee JM, Han J, Chea L, Zanetti M, Koo EH, Lin JH. PERK-mediated induction of microRNA-483 disrupts cellular ATP homeostasis during the unfolded protein response. J Biol Chem 2020; 295:237-249. [PMID: 31792031 PMCID: PMC6952592 DOI: 10.1074/jbc.ra119.008336] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2019] [Revised: 11/26/2019] [Indexed: 01/08/2023] Open
Abstract
Endoplasmic reticulum (ER) stress activates the unfolded protein response (UPR), which reduces levels of misfolded proteins. However, if ER homeostasis is not restored and the UPR remains chronically activated, cells undergo apoptosis. The UPR regulator, PKR-like endoplasmic reticulum kinase (PERK), plays an important role in promoting cell death when persistently activated; however, the underlying mechanisms are poorly understood. Here, we profiled the microRNA (miRNA) transcriptome in human cells exposed to ER stress and identified miRNAs that are selectively induced by PERK signaling. We found that expression of a PERK-induced miRNA, miR-483, promotes apoptosis in human cells. miR-483 induction was mediated by a transcription factor downstream of PERK, activating transcription factor 4 (ATF4), but not by the CHOP transcription factor. We identified the creatine kinase brain-type (CKB) gene, encoding an enzyme that maintains cellular ATP reserves through phosphocreatine production, as being repressed during the UPR and targeted by miR-483. We found that ER stress, selective PERK activation, and CKB knockdown all decrease cellular ATP levels, leading to increased vulnerability to ER stress-induced cell death. Our findings identify miR-483 as a downstream target of the PERK branch of the UPR. We propose that disruption of cellular ATP homeostasis through miR-483-mediated CKB silencing promotes ER stress-induced apoptosis.
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Affiliation(s)
- Nobuhiko Hiramatsu
- Department of Pathology, University of California San Diego, La Jolla, California 92093-0612
| | - Karen Chiang
- Department of Pathology, University of California San Diego, La Jolla, California 92093-0612; Department of Neurosciences, University of California San Diego, La Jolla, California 92093-0612
| | - Cathrine Aivati
- Department of Pathology, University of California San Diego, La Jolla, California 92093-0612
| | - Jeffrey J Rodvold
- Moores Cancer Center, University of California San Diego, La Jolla, California 92093-0612
| | - Ji-Min Lee
- Soonchunhyang Institute of Med-bio Science, Soonchunhyang University, Asan 31151, Korea
| | - Jaeseok Han
- Soonchunhyang Institute of Med-bio Science, Soonchunhyang University, Asan 31151, Korea
| | - Leon Chea
- Department of Pathology, Stanford University, Stanford, California 94304
| | - Maurizio Zanetti
- Moores Cancer Center, University of California San Diego, La Jolla, California 92093-0612
| | - Edward H Koo
- Department of Neurosciences, University of California San Diego, La Jolla, California 92093-0612; Departments of Medicine and Physiology, Yong Loo Lin School of Medicine, National University of Singapore, 117549 Singapore
| | - Jonathan H Lin
- Department of Pathology, University of California San Diego, La Jolla, California 92093-0612; Department of Pathology, Stanford University, Stanford, California 94304; Veterans Affairs Palo Alto Healthcare System, Palo Alto, California 94304.
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Małecki JM, Willemen HLDM, Pinto R, Ho AYY, Moen A, Kjønstad IF, Burgering BMT, Zwartkruis F, Eijkelkamp N, Falnes PØ. Lysine methylation by the mitochondrial methyltransferase FAM173B optimizes the function of mitochondrial ATP synthase. J Biol Chem 2018; 294:1128-1141. [PMID: 30530489 DOI: 10.1074/jbc.ra118.005473] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2018] [Revised: 12/05/2018] [Indexed: 01/23/2023] Open
Abstract
Lysine methylation is an important post-translational modification that is also present on mitochondrial proteins, but the mitochondrial lysine-specific methyltransferases (KMTs) responsible for modification are in most cases unknown. Here, we set out to determine the function of human family with sequence similarity 173 member B (FAM173B), a mitochondrial methyltransferase (MTase) reported to promote chronic pain. Using bioinformatics analyses and biochemical assays, we found that FAM173B contains an atypical, noncleavable mitochondrial targeting sequence responsible for its localization to mitochondria. Interestingly, CRISPR/Cas9-mediated KO of FAM173B in mammalian cells abrogated trimethylation of Lys-43 in ATP synthase c-subunit (ATPSc), a modification previously reported as ubiquitous among metazoans. ATPSc methylation was restored by complementing the KO cells with enzymatically active human FAM173B or with a putative FAM173B orthologue from the nematode Caenorhabditis elegans Interestingly, lack of Lys-43 methylation caused aberrant incorporation of ATPSc into the ATP synthase complex and resulted in decreased ATP-generating ability of the complex, as well as decreased mitochondrial respiration. In summary, we have identified FAM173B as the long-sought KMT responsible for methylation of ATPSc, a key protein in cellular ATP production, and have demonstrated functional significance of ATPSc methylation. We suggest renaming FAM173B to ATPSc-KMT (gene name ATPSCKMT).
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Affiliation(s)
- Jędrzej M Małecki
- Department of Biosciences, Faculty of Mathematics and Natural Sciences, University of Oslo, 0316 Oslo, Norway.
| | | | - Rita Pinto
- Department of Biosciences, Faculty of Mathematics and Natural Sciences, University of Oslo, 0316 Oslo, Norway
| | - Angela Y Y Ho
- Department of Biosciences, Faculty of Mathematics and Natural Sciences, University of Oslo, 0316 Oslo, Norway
| | - Anders Moen
- Department of Biosciences, Faculty of Mathematics and Natural Sciences, University of Oslo, 0316 Oslo, Norway
| | - Ingrid F Kjønstad
- Department of Biosciences, Faculty of Mathematics and Natural Sciences, University of Oslo, 0316 Oslo, Norway
| | - Boudewijn M T Burgering
- Molecular Cancer Research, Center for Molecular Medicine, Oncode Institute, University Medical Center Utrecht, Utrecht University, 3584 EA Utrecht, The Netherlands
| | - Fried Zwartkruis
- Molecular Cancer Research, Center for Molecular Medicine, Oncode Institute, University Medical Center Utrecht, Utrecht University, 3584 EA Utrecht, The Netherlands
| | - Niels Eijkelkamp
- Laboratory of Translational Immunology (LTI), 3584 EA Utrecht, The Netherlands
| | - Pål Ø Falnes
- Department of Biosciences, Faculty of Mathematics and Natural Sciences, University of Oslo, 0316 Oslo, Norway.
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Sgarbi G, Gorini G, Liuzzi F, Solaini G, Baracca A. Hypoxia and IF₁ Expression Promote ROS Decrease in Cancer Cells. Cells 2018; 7:E64. [PMID: 29933600 PMCID: PMC6071258 DOI: 10.3390/cells7070064] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2018] [Revised: 06/15/2018] [Accepted: 06/19/2018] [Indexed: 12/11/2022] Open
Abstract
The role of reactive oxygen species (ROS) in the metabolic reprogramming of cells adapted to hypoxia and the interplay between ROS and hypoxia in malignancy is under debate. Here, we examined how ROS levels are modulated by hypoxia in human cancer compared to untransformed cells. Short time exposure (20 min) of either fibroblasts or 143B osteosarcoma cells to low oxygen tension down to 0.5% induced a significant decrease of the cellular ROS level, as detected by the CellROX fluorescent probe (−70%). Prolonging the cells’ exposure to hypoxia for 24 h, ROS decreased further, reaching nearly 20% of the normoxic value. In this regard, due to the debated role of the endogenous inhibitor protein (IF₁) of the ATP synthase complex in cancer cell bioenergetics, we investigated whether IF₁ is involved in the control of ROS generation under severe hypoxic conditions. A significant ROS content decrease was observed in hypoxia in both IF₁-expressing and IF₁- silenced cells compared to normoxia. However, IF₁-silenced cells showed higher ROS levels compared to IF1-containing cells. In addition, the MitoSOX Red-measured superoxide level of all the hypoxic cells was significantly lower compared to normoxia; however, the decrease was milder than the marked drop of ROS content. Accordingly, the difference between IF₁-expressing and IF₁-silenced cells was smaller but significant in both normoxia and hypoxia. In conclusion, the interplay between ROS and hypoxia and its modulation by IF₁ have to be taken into account to develop therapeutic strategies against cancer.
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Affiliation(s)
- Gianluca Sgarbi
- Department of Biomedical and Neuromotor Sciences, Laboratory of Biochemistry and Mitochondrial Pathophysiology, University of Bologna, Bologna 40126, Italy.
| | - Giulia Gorini
- Department of Biomedical and Neuromotor Sciences, Laboratory of Biochemistry and Mitochondrial Pathophysiology, University of Bologna, Bologna 40126, Italy.
- Department of Biomedical, Experimental, and Clinical Sciences "Mario Serio", University of Florence, Florence 50121, Italy.
| | - Francesca Liuzzi
- Department of Biomedical and Neuromotor Sciences, Laboratory of Biochemistry and Mitochondrial Pathophysiology, University of Bologna, Bologna 40126, Italy.
| | - Giancarlo Solaini
- Department of Biomedical and Neuromotor Sciences, Laboratory of Biochemistry and Mitochondrial Pathophysiology, University of Bologna, Bologna 40126, Italy.
| | - Alessandra Baracca
- Department of Biomedical and Neuromotor Sciences, Laboratory of Biochemistry and Mitochondrial Pathophysiology, University of Bologna, Bologna 40126, Italy.
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Whitham JM, Moon JW, Rodriguez M, Engle NL, Klingeman DM, Rydzak T, Abel MM, Tschaplinski TJ, Guss AM, Brown SD. Clostridium thermocellum LL1210 pH homeostasis mechanisms informed by transcriptomics and metabolomics. Biotechnol Biofuels 2018; 11:98. [PMID: 29632556 PMCID: PMC5887222 DOI: 10.1186/s13068-018-1095-y] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/11/2017] [Accepted: 03/24/2018] [Indexed: 05/21/2023]
Abstract
BACKGROUND Clostridium (Ruminiclostridium) thermocellum is a model fermentative anaerobic thermophile being studied and engineered for consolidated bioprocessing of lignocellulosic feedstocks into fuels and chemicals. Engineering efforts have resulted in significant improvements in ethanol yields and titers although further advances are required to make the bacterium industry-ready. For instance, fermentations at lower pH could enable co-culturing with microbes that have lower pH optima, augment productivity, and reduce buffering cost. C. thermocellum is typically grown at neutral pH, and little is known about its pH limits or pH homeostasis mechanisms. To better understand C. thermocellum pH homeostasis we grew strain LL1210 (C. thermocellum DSM1313 Δhpt ΔhydG Δldh Δpfl Δpta-ack), currently the highest ethanol producing strain of C. thermocellum, at different pH values in chemostat culture and applied systems biology tools. RESULTS Clostridium thermocellum LL1210 was found to be growth-limited below pH 6.24 at a dilution rate of 0.1 h-1. F1F0-ATPase gene expression was upregulated while many ATP-utilizing enzymes and pathways were downregulated at pH 6.24. These included most flagella biosynthesis genes, genes for chemotaxis, and other motility-related genes (> 50) as well as sulfate transport and reduction, nitrate transport and nitrogen fixation, and fatty acid biosynthesis genes. Clustering and enrichment of differentially expressed genes at pH values 6.48, pH 6.24 and pH 6.12 (washout conditions) compared to pH 6.98 showed inverse differential expression patterns between the F1F0-ATPase and genes for other ATP-utilizing enzymes. At and below pH 6.24, amino acids including glutamate and valine; long-chain fatty acids, their iso-counterparts and glycerol conjugates; glycolysis intermediates 3-phosphoglycerate, glucose 6-phosphate, and glucose accumulated intracellularly. Glutamate was 267 times more abundant in cells at pH 6.24 compared to pH 6.98, and intercellular concentration reached 1.8 μmol/g pellet at pH 5.80 (stopped flow). CONCLUSIONS Clostridium thermocellum LL1210 can grow under slightly acidic conditions, similar to limits reported for other strains. This foundational study provides a detailed characterization of a relatively acid-intolerant bacterium and provides genetic targets for strain improvement. Future studies should examine adding gene functions used by more acid-tolerant bacteria for improved pH homeostasis at acidic pH values.
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Affiliation(s)
- Jason M. Whitham
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN USA
- BioEnergy Science Center, National Laboratory, Oak Ridge, TN USA
| | - Ji-Won Moon
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN USA
| | - Miguel Rodriguez
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN USA
- BioEnergy Science Center, National Laboratory, Oak Ridge, TN USA
| | - Nancy L. Engle
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN USA
- BioEnergy Science Center, National Laboratory, Oak Ridge, TN USA
| | - Dawn M. Klingeman
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN USA
- BioEnergy Science Center, National Laboratory, Oak Ridge, TN USA
| | - Thomas Rydzak
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN USA
- BioEnergy Science Center, National Laboratory, Oak Ridge, TN USA
- Present Address: Department of Biological Science, University of Calgary, Calgary, AB T2N 1N4 Canada
| | - Malaney M. Abel
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN USA
- BioEnergy Science Center, National Laboratory, Oak Ridge, TN USA
| | - Timothy J. Tschaplinski
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN USA
- BioEnergy Science Center, National Laboratory, Oak Ridge, TN USA
| | - Adam M. Guss
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN USA
- BioEnergy Science Center, National Laboratory, Oak Ridge, TN USA
| | - Steven D. Brown
- Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN USA
- BioEnergy Science Center, National Laboratory, Oak Ridge, TN USA
- Present Address: LanzaTech, Inc., Skokie, IL USA
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McMillan DGG, Watanabe R, Ueno H, Cook GM, Noji H. Biophysical Characterization of a Thermoalkaliphilic Molecular Motor with a High Stepping Torque Gives Insight into Evolutionary ATP Synthase Adaptation. J Biol Chem 2016; 291:23965-23977. [PMID: 27624936 DOI: 10.1074/jbc.m116.743633] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2016] [Revised: 09/12/2016] [Indexed: 11/06/2022] Open
Abstract
F1F0 ATP synthases are bidirectional molecular motors that translocate protons across the cell membrane by either synthesizing or hydrolyzing ATP. Alkaliphile ATP synthases are highly adapted, performing oxidative phosphorylation at high pH against an inverted pH gradient (acidin/alkalineout). Unlike mesophilic ATP synthases, alkaliphilic enzymes have tightly regulated ATP hydrolysis activity, which can be relieved in the presence of lauryldimethylamine oxide. Here, we characterized the rotary dynamics of the Caldalkalibacillus thermarum TA2.A1 F1 ATPase (TA2F1) with two forms of single molecule analysis, a magnetic bead duplex and a gold nanoparticle. TA2F1 rotated in a counterclockwise direction in both systems, adhering to Michaelis-Menten kinetics with a maximum rotation rate (Vmax) of 112.4 revolutions/s. TA2F1 displayed 120° unitary steps coupled with ATP hydrolysis. Torque measurements revealed the highest torque (52.4 piconewtons) derived from an F1 molecule using fluctuation theorem. The implications of high torque in terms of extreme environment adaptation are discussed.
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Affiliation(s)
- Duncan G G McMillan
- From the Department of Applied Chemistry, Graduate School of Engineering, The University of Tokyo, Tokyo 113-8656, Japan and
| | - Rikiya Watanabe
- From the Department of Applied Chemistry, Graduate School of Engineering, The University of Tokyo, Tokyo 113-8656, Japan and
| | - Hiroshi Ueno
- From the Department of Applied Chemistry, Graduate School of Engineering, The University of Tokyo, Tokyo 113-8656, Japan and
| | - Gregory M Cook
- the Department of Microbiology and Immunology, Otago School of Medical Sciences, University of Otago, P. O. Box 56, Dunedin 9054, New Zealand
| | - Hiroyuki Noji
- From the Department of Applied Chemistry, Graduate School of Engineering, The University of Tokyo, Tokyo 113-8656, Japan and
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7
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Barbato S, Sgarbi G, Gorini G, Baracca A, Solaini G. The inhibitor protein (IF1) of the F1F0-ATPase modulates human osteosarcoma cell bioenergetics. J Biol Chem 2015; 290:6338-48. [PMID: 25605724 PMCID: PMC4358270 DOI: 10.1074/jbc.m114.631788] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2014] [Revised: 01/20/2015] [Indexed: 01/20/2023] Open
Abstract
The bioenergetics of IF1 transiently silenced cancer cells has been extensively investigated, but the role of IF1 (the natural inhibitor protein of F1F0-ATPase) in cancer cell metabolism is still uncertain. To shed light on this issue, we established a method to prepare stably IF1-silenced human osteosarcoma clones and explored the bioenergetics of IF1 null cancer cells. We showed that IF1-silenced cells proliferate normally, consume glucose, and release lactate as controls do, and contain a normal steady-state ATP level. However, IF1-silenced cells displayed an enhanced steady-state mitochondrial membrane potential and consistently showed a reduced ADP-stimulated respiration rate. In the parental cells (i.e. control cells containing IF1) the inhibitor protein was found to be associated with the dimeric form of the ATP synthase complex, therefore we propose that the interaction of IF1 with the complex either directly, by increasing the catalytic activity of the enzyme, or indirectly, by improving the structure of mitochondrial cristae, can increase the oxidative phosphorylation rate in osteosarcoma cells grown under normoxic conditions.
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Affiliation(s)
- Simona Barbato
- From the Department of Biomedical and NeuroMotor Sciences (DIBINEM), University of Bologna, Via Irnerio 48, 40126 Bologna, Italy
| | - Gianluca Sgarbi
- From the Department of Biomedical and NeuroMotor Sciences (DIBINEM), University of Bologna, Via Irnerio 48, 40126 Bologna, Italy
| | - Giulia Gorini
- From the Department of Biomedical and NeuroMotor Sciences (DIBINEM), University of Bologna, Via Irnerio 48, 40126 Bologna, Italy
| | - Alessandra Baracca
- From the Department of Biomedical and NeuroMotor Sciences (DIBINEM), University of Bologna, Via Irnerio 48, 40126 Bologna, Italy
| | - Giancarlo Solaini
- From the Department of Biomedical and NeuroMotor Sciences (DIBINEM), University of Bologna, Via Irnerio 48, 40126 Bologna, Italy
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Senouci-Rezkallah K, Jobin MP, Schmitt P. Adaptive responses of Bacillus cereus ATCC14579 cells upon exposure to acid conditions involve ATPase activity to maintain their internal pH. Microbiologyopen 2015; 4:313-322. [PMID: 25740257 PMCID: PMC4398511 DOI: 10.1002/mbo3.239] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2014] [Revised: 12/17/2014] [Accepted: 12/22/2014] [Indexed: 11/08/2022] Open
Abstract
This study examined the involvement of ATPase activity in the acid tolerance response (ATR) of Bacillus cereus ATCC14579 strain. In the current work, B. cereus cells were grown in anaerobic chemostat culture at external pH (pHe ) 7.0 or 5.5 and at a growth rate of 0.2 h-1 . Population reduction and internal pH (pHi ) after acid shock at pH 4.0 was examined either with or without ATPase inhibitor N,N'-dicyclohexylcarbodiimide (DCCD) and ionophores valinomycin and nigericin. Population reduction after acid shock at pH 4.0 was strongly limited in cells grown at pH 5.5 (acid-adapted cells) compared with cells grown at pH 7.0 (unadapted cells), indicating that B. cereus cells grown at low pHe were able to induce a significant ATR and Exercise-induced increase in ATPase activity. However, DCCD and ionophores had a negative effect on the ability of B. cereus cells to survive and maintain their pHi during acid shock. When acid shock was achieved after DCCD treatment, pHi was markedly dropped in unadapted and acid-adapted cells. The ATPase activity was also significantly inhibited by DCCD and ionophores in acid-adapted cells. Furthermore, transcriptional analysis revealed that atpB (ATP beta chain) transcripts was increased in acid-adapted cells compared to unadapted cells before and after acid shock. Our data demonstrate that B. cereus is able to induce an ATR during growth at low pH. These adaptations depend on the ATPase activity induction and pHi homeostasis. Our data demonstrate that the ATPase enzyme can be implicated in the cytoplasmic pH regulation and in acid tolerance of B. cereus acid-adapted cells.
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Affiliation(s)
- Khadidja Senouci-Rezkallah
- UMR408 Sécurité et Qualité des Produits d'Origine Végétale, INRA, Université d'Avignon, 84914, Avignon, France.,Faculté des Sciences de la Nature et de la Vie, Université de Mascara, Mascara, Algérie.,Département de Microbiologie, Infectiologie et Immunologie, Université de Montréal, Montréal, Québec, Canada
| | - Michel P Jobin
- UMR408 Sécurité et Qualité des Produits d'Origine Végétale, INRA, Université d'Avignon, 84914, Avignon, France
| | - Philippe Schmitt
- UMR408 Sécurité et Qualité des Produits d'Origine Végétale, INRA, Université d'Avignon, 84914, Avignon, France
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Steed PR, Fillingame RH. Residues in the polar loop of subunit c in Escherichia coli ATP synthase function in gating proton transport to the cytoplasm. J Biol Chem 2013; 289:2127-38. [PMID: 24297166 DOI: 10.1074/jbc.m113.527879] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Rotary catalysis in F1F0 ATP synthase is powered by proton translocation through the membrane-embedded F0 sector. Proton binding and release occur in the middle of the membrane at Asp-61 on the second transmembrane helix (TMH) of subunit c, which folds in a hairpin-like structure with two TMHs. Previously, the aqueous accessibility of Cys substitutions in the transmembrane regions of subunit c was probed by testing the inhibitory effects of Ag(+) or Cd(2+) on function, which revealed extensive aqueous access in the region around Asp-61 and on the half of TMH2 extending to the cytoplasm. In the current study, we surveyed the Ag(+) and Cd(2+) sensitivity of Cys substitutions in the loop of the helical hairpin and used a variety of assays to categorize the mechanisms by which Ag(+) or Cd(2+) chelation with the Cys thiolates caused inhibition. We identified two distinct metal-sensitive regions in the cytoplasmic loop where function was inhibited by different mechanisms. Metal binding to Cys substitutions in the N-terminal half of the loop resulted in an uncoupling of F1 from F0 with release of F1 from the membrane. In contrast, substitutions in the C-terminal half of the loop retained membrane-bound F1 after metal treatment. In several of these cases, inhibition was shown to be due to blockage of passive H(+) translocation through F0 as assayed with F0 reconstituted into liposomes. The results suggest that the C-terminal domain of the cytoplasmic loop may function in gating H(+) translocation to the cytoplasm.
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Affiliation(s)
- P Ryan Steed
- From the Department of Biomolecular Chemistry, School of Medicine and Public Health, University of Wisconsin, Madison, Wisconsin 53706
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