151
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Abstract
Neutrophils are essential for killing bacteria and other microorganisms, and they also have a significant role in regulating the inflammatory response. Stimulated neutrophils activate their NADPH oxidase (NOX2) to generate large amounts of superoxide, which acts as a precursor of hydrogen peroxide and other reactive oxygen species that are generated by their heme enzyme myeloperoxidase. When neutrophils engulf bacteria they enclose them in small vesicles (phagosomes) into which superoxide is released by activated NOX2 on the internalized neutrophil membrane. The superoxide dismutates to hydrogen peroxide, which is used by myeloperoxidase to generate other oxidants, including the highly microbicidal species hypochlorous acid. NOX activation occurs at other sites in the cell, where it is considered to have a regulatory function. Neutrophils also release oxidants, which can modify extracellular targets and affect the function of neighboring cells. We discuss the identity and chemical properties of the specific oxidants produced by neutrophils in different situations, and what is known about oxidative mechanisms of microbial killing, inflammatory tissue damage, and signaling.
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Affiliation(s)
- Christine C Winterbourn
- Centre for Free Radical Research, Department of Pathology, University of Otago, Christchurch 8011, New Zealand; , ,
| | - Anthony J Kettle
- Centre for Free Radical Research, Department of Pathology, University of Otago, Christchurch 8011, New Zealand; , ,
| | - Mark B Hampton
- Centre for Free Radical Research, Department of Pathology, University of Otago, Christchurch 8011, New Zealand; , ,
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152
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Groitl B, Horowitz S, Makepeace KAT, Petrotchenko EV, Borchers CH, Reichmann D, Bardwell JCA, Jakob U. Protein unfolding as a switch from self-recognition to high-affinity client binding. Nat Commun 2016; 7:10357. [PMID: 26787517 PMCID: PMC4735815 DOI: 10.1038/ncomms10357] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2015] [Accepted: 12/02/2015] [Indexed: 01/20/2023] Open
Abstract
Stress-specific activation of the chaperone Hsp33 requires the unfolding of a central linker region. This activation mechanism suggests an intriguing functional relationship between the chaperone's own partial unfolding and its ability to bind other partially folded client proteins. However, identifying where Hsp33 binds its clients has remained a major gap in our understanding of Hsp33's working mechanism. By using site-specific Fluorine-19 nuclear magnetic resonance experiments guided by in vivo crosslinking studies, we now reveal that the partial unfolding of Hsp33's linker region facilitates client binding to an amphipathic docking surface on Hsp33. Furthermore, our results provide experimental evidence for the direct involvement of conditionally disordered regions in unfolded protein binding. The observed structural similarities between Hsp33's own metastable linker region and client proteins present a possible model for how Hsp33 uses protein unfolding as a switch from self-recognition to high-affinity client binding. Under stress conditions the molecular chaperone Hsp33 is activated to process unfolded proteins. Here, the authors use in vivo and in vitro crosslinking and 19F-NMR to elucidate the binding site for misfolded proteins and are able to propose a model for its mechanism of action.
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Affiliation(s)
- Bastian Groitl
- Department of Molecular, Cellular and Developmental Biology, University of Michigan, 830 N-University Avenue, Ann Arbor, Michigan 48109-1048, USA
| | - Scott Horowitz
- Department of Molecular, Cellular and Developmental Biology, University of Michigan, 830 N-University Avenue, Ann Arbor, Michigan 48109-1048, USA.,Howard Hughes Medical Institute, University of Michigan, 830 N-University Avenue, Ann Arbor, Michigan 48109-1048, USA
| | - Karl A T Makepeace
- Department of Biochemistry and Microbiology, Genome BC Proteomics Centre, University of Victoria, 4464 Markham Street #3101, Victoria, British Columbia, Canada V8Z5N3
| | - Evgeniy V Petrotchenko
- Department of Biochemistry and Microbiology, Genome BC Proteomics Centre, University of Victoria, 4464 Markham Street #3101, Victoria, British Columbia, Canada V8Z5N3
| | - Christoph H Borchers
- Department of Biochemistry and Microbiology, Genome BC Proteomics Centre, University of Victoria, 4464 Markham Street #3101, Victoria, British Columbia, Canada V8Z5N3
| | - Dana Reichmann
- Department of Molecular, Cellular and Developmental Biology, University of Michigan, 830 N-University Avenue, Ann Arbor, Michigan 48109-1048, USA
| | - James C A Bardwell
- Department of Molecular, Cellular and Developmental Biology, University of Michigan, 830 N-University Avenue, Ann Arbor, Michigan 48109-1048, USA.,Howard Hughes Medical Institute, University of Michigan, 830 N-University Avenue, Ann Arbor, Michigan 48109-1048, USA
| | - Ursula Jakob
- Department of Molecular, Cellular and Developmental Biology, University of Michigan, 830 N-University Avenue, Ann Arbor, Michigan 48109-1048, USA
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153
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Han X, Wang Z, Wang X, Zheng X, Ma J, Wu Z. Microbial responses to membrane cleaning using sodium hypochlorite in membrane bioreactors: Cell integrity, key enzymes and intracellular reactive oxygen species. WATER RESEARCH 2016; 88:293-300. [PMID: 26512807 DOI: 10.1016/j.watres.2015.10.033] [Citation(s) in RCA: 78] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/18/2015] [Revised: 09/24/2015] [Accepted: 10/17/2015] [Indexed: 06/05/2023]
Abstract
Sodium hypochlorite (NaClO) is a commonly used reagent for membrane cleaning in membrane bioreactors (MBRs), while it, being a kind of disinfectant (oxidant), may impair viability of microbes or even totally inactivate them upon its diffusion into mixed liquor during membrane cleaning. In this study, we systematically examine the effects of NaClO on microorganisms in terms of microbial cell integrity, metabolism behaviours (key enzymes), and intracellular reactive oxygen species (ROS) under various NaClO concentrations. Different proportions of microbial cells in activated sludge were damaged within several minutes dependent on NaClO dosages (5-50 mg/g-SS), and correspondingly organic matters were released to bulk solution. Inhibition of key enzymes involved in organic matter biodegradation, nitrification and denitrification was observed in the presence of NaClO above 1 mg/g-SS, and thus organic matter and nitrogen removal efficiencies were decreased. It was also demonstrated that intracellular ROS production was increased with the NaClO dosage higher than 1 mg/g-SS, which likely induced further damage to microbial cells.
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Affiliation(s)
- Xiaomeng Han
- State Key Laboratory of Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Tongji University, Shanghai 200092, PR China
| | - Zhiwei Wang
- State Key Laboratory of Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Tongji University, Shanghai 200092, PR China.
| | - Xueye Wang
- State Key Laboratory of Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Tongji University, Shanghai 200092, PR China
| | - Xiang Zheng
- School of Environment and Natural Resources, Renmin University of China, Beijing 100872, PR China
| | - Jinxing Ma
- State Key Laboratory of Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Tongji University, Shanghai 200092, PR China
| | - Zhichao Wu
- State Key Laboratory of Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Tongji University, Shanghai 200092, PR China
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154
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Lee YS, Kim JH, Seo MD, Ryu KS, Kim EH, Won HS. Oxidation-induced conformational change of Hsp33, monitored by NMR. JOURNAL OF THE KOREAN MAGNETIC RESONANCE SOCIETY 2015. [DOI: 10.6564/jkmrs.2015.19.3.099] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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155
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Lee YS, Lee J, Ryu KS, Lee Y, Jung TG, Jang JH, Sim DW, Kim EH, Seo MD, Lee KW, Won HS. Semi-Empirical Structure Determination of Escherichia coli Hsp33 and Identification of Dynamic Regulatory Elements for the Activation Process. J Mol Biol 2015; 427:3850-61. [DOI: 10.1016/j.jmb.2015.09.029] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2015] [Revised: 09/21/2015] [Accepted: 09/30/2015] [Indexed: 11/27/2022]
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156
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Malheiro J, Araújo P, Machado I, Lemos M, Mergulhão F, Melo L, Simões M. The Effects of Selected Brominated and Chlorinated Chemicals onPseudomonas fluorescensPlanktonic Cells and Flow-Generated Biofilms. J FOOD PROCESS PRES 2015. [DOI: 10.1111/jfpp.12609] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Affiliation(s)
- J. Malheiro
- LEPABE; Department of Chemical Engineering; Faculty of Engineering; University of Porto; Rua Dr. Roberto Frias s/n 4200-465 Porto Portugal
| | - P. Araújo
- LEPABE; Department of Chemical Engineering; Faculty of Engineering; University of Porto; Rua Dr. Roberto Frias s/n 4200-465 Porto Portugal
| | - I. Machado
- LEPABE; Department of Chemical Engineering; Faculty of Engineering; University of Porto; Rua Dr. Roberto Frias s/n 4200-465 Porto Portugal
| | - M. Lemos
- LEPABE; Department of Chemical Engineering; Faculty of Engineering; University of Porto; Rua Dr. Roberto Frias s/n 4200-465 Porto Portugal
- Department of Chemical Engineering & Biotechnology; New Museums Site; Cambridge UK
| | - F. Mergulhão
- LEPABE; Department of Chemical Engineering; Faculty of Engineering; University of Porto; Rua Dr. Roberto Frias s/n 4200-465 Porto Portugal
| | - L. Melo
- LEPABE; Department of Chemical Engineering; Faculty of Engineering; University of Porto; Rua Dr. Roberto Frias s/n 4200-465 Porto Portugal
| | - M. Simões
- LEPABE; Department of Chemical Engineering; Faculty of Engineering; University of Porto; Rua Dr. Roberto Frias s/n 4200-465 Porto Portugal
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157
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Abstract
The ancestors of Escherichia coli and Salmonella ultimately evolved to thrive in air-saturated liquids, in which oxygen levels reach 210 μM at 37°C. However, in 1976 Brown and colleagues reported that some sensitivity persists: growth defects still become apparent when hyperoxia is imposed on cultures of E. coli. This residual vulnerability was important in that it raised the prospect that normal levels of oxygen might also injure bacteria, albeit at reduced rates that are not overtly toxic. The intent of this article is both to describe the threat that molecular oxygen poses for bacteria and to detail what we currently understand about the strategies by which E. coli and Salmonella defend themselves against it. E. coli mutants that lack either superoxide dismutases or catalases and peroxidases exhibit a variety of growth defects. These phenotypes constitute the best evidence that aerobic cells continually generate intracellular superoxide and hydrogen peroxide at potentially lethal doses. Superoxide has reduction potentials that allow it to serve in vitro as either a weak univalent reductant or a stronger univalent oxidant. The addition of micromolar hydrogen peroxide to lab media will immediately block the growth of most cells, and protracted exposure will result in the loss of viability. The need for inducible antioxidant systems seems especially obvious for enteric bacteria, which move quickly from the anaerobic gut to fully aerobic surface waters or even to ROS-perfused phagolysosomes. E. coli and Salmonella have provided two paradigmatic models of oxidative-stress responses: the SoxRS and OxyR systems.
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158
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Sawada K, Caballé-Serrano J, Bosshardt DD, Schaller B, Miron RJ, Buser D, Gruber R. Antiseptic solutions modulate the paracrine-like activity of bone chips: differential impact of chlorhexidine and sodium hypochlorite. J Clin Periodontol 2015; 42:883-891. [PMID: 26284317 DOI: 10.1111/jcpe.12447] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/12/2015] [Indexed: 12/14/2022]
Abstract
AIM Chemical decontamination increases the availability of bone grafts; however, it remains unclear whether antiseptic processing changes the biological activity of bone. MATERIALS AND METHODS Bone chips were incubated with four different antiseptic solutions including (1) povidone-iodine (0.5%), (2) chlorhexidine diguluconate (0.2%), (3) hydrogen peroxide (1%) and (4) sodium hypochlorite (0.25%). After 10 min. of incubation, changes in the capacity of the bone-conditioned medium (BCM) to modulate gene expression of gingival fibroblasts was investigated. RESULTS Conditioned medium obtained from freshly prepared bone chips increased the expression of TGF-β target genes interleukin 11 (IL11), proteoglycan4 (PRG4), NADPH oxidase 4 (NOX4), and decreased the expression of adrenomedullin (ADM), and pentraxin 3 (PTX3) in gingival fibroblasts. Incubation of bone chips with 0.2% chlorhexidine, followed by vigorously washing resulted in a BCM with even higher expression of IL11, PRG4 and NOX4. These findings were also detected with a decrease in cell viability and an activation of apoptosis signalling. Chlorhexidine alone, at low concentrations, increased IL11, PRG4 and NOX4 expression, independent of the TGF-β receptor I kinase activity. In contrast, 0.25% sodium hypochlorite almost entirely abolished the activity of BCM, whereas the other two antiseptic solutions, 1% hydrogen peroxide and 0.5% povidone-iodine, had relatively no impact respectively. CONCLUSION These in vitro findings demonstrate that incubation of bone chips with chlorhexidine differentially affects the activity of the respective BCM compared to the other antiseptic solutions. The data further suggest that the main effects are caused by chlorhexidine remaining in the BCM after repeated washing of the bone chips.
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Affiliation(s)
- Kosaku Sawada
- Department of Cranio Maxillofacial Surgery, Inselspital, University of Bern, Bern, Switzerland
| | - Jordi Caballé-Serrano
- Department of Oral Surgery and Stomatology, School of Dental Medicine, University of Bern, Bern, Switzerland.,Department of Oral and Maxillofacial Surgery, College of Dentistry, Universitat Internacional de Catalunya, Barcelona, Spain
| | - Dieter D Bosshardt
- Department of Oral Surgery and Stomatology, School of Dental Medicine, University of Bern, Bern, Switzerland.,Robert K. Schenk Laboratory of Oral Histology, School of Dental Medicine, University of Bern, Bern, Switzerland
| | - Benoit Schaller
- Department of Cranio Maxillofacial Surgery, Inselspital, University of Bern, Bern, Switzerland
| | - Richard J Miron
- Department of Oral Surgery and Stomatology, School of Dental Medicine, University of Bern, Bern, Switzerland
| | - Daniel Buser
- Department of Oral Surgery and Stomatology, School of Dental Medicine, University of Bern, Bern, Switzerland
| | - Reinhard Gruber
- Department of Oral Surgery and Stomatology, School of Dental Medicine, University of Bern, Bern, Switzerland.,Department of Preventive, Restorative and Pediatric Dentistry, University of Bern, Bern, Switzerland.,Department of Oral Biology, Medical University of Vienna, Vienna, Austria
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159
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Lee HJ, Cho MJ, Chang SK. Ratiometric Signaling of Hypochlorite by the Oxidative Cleavage of Sulfonhydrazide-Based Rhodamine–Dansyl Dyad. Inorg Chem 2015; 54:8644-9. [DOI: 10.1021/acs.inorgchem.5b01284] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Affiliation(s)
- Hyo Jin Lee
- Department of Chemistry, Chung-Ang University, Seoul 156-756, Republic of Korea
| | - Min Jeoung Cho
- Department of Chemistry, Chung-Ang University, Seoul 156-756, Republic of Korea
| | - Suk-Kyu Chang
- Department of Chemistry, Chung-Ang University, Seoul 156-756, Republic of Korea
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160
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Lebrun V, Tron A, Lebrun C, Latour J, McClenaghan ND, Sénèque O. Reactivity of a Zn(Cys)
2
(His)
2
Zinc Finger with Singlet Oxygen: Oxidation Directed toward Cysteines but not Histidines. Chemistry 2015; 21:14002-10. [DOI: 10.1002/chem.201501749] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2015] [Indexed: 11/10/2022]
Affiliation(s)
- Vincent Lebrun
- Univ. Grenoble Alpes, LCBM/PMB and CEA, IRTSV/CBM/PMB and CNRS, LCBM UMR 5249, PMB, 38000 Grenoble (France)
| | - Arnaud Tron
- Univ. Bordeaux and CNRS, ISM, 33405 Talence (France)
| | - Colette Lebrun
- Univ. Grenoble Alpes and CEA, INAC/SCIB/RICC, 38000 Grenoble (France)
| | - Jean‐Marc Latour
- Univ. Grenoble Alpes, LCBM/PMB and CEA, IRTSV/CBM/PMB and CNRS, LCBM UMR 5249, PMB, 38000 Grenoble (France)
| | | | - Olivier Sénèque
- Univ. Grenoble Alpes, LCBM/PMB and CEA, IRTSV/CBM/PMB and CNRS, LCBM UMR 5249, PMB, 38000 Grenoble (France)
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161
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Lu HC, Chung SS, Fornili A, Fraternali F. Anatomy of protein disorder, flexibility and disease-related mutations. Front Mol Biosci 2015; 2:47. [PMID: 26322316 PMCID: PMC4532925 DOI: 10.3389/fmolb.2015.00047] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2015] [Accepted: 07/29/2015] [Indexed: 01/23/2023] Open
Abstract
Integration of protein structural information with human genetic variation and pathogenic mutations is essential to understand molecular mechanisms associated with the effects of polymorphisms on protein interactions and cellular processes. We investigate occurrences of non-synonymous SNPs in ordered and disordered protein regions by systematic mapping of common variants and disease-related SNPs onto these regions. We show that common variants accumulate in disordered regions; conversely pathogenic variants are significantly depleted in disordered regions. These different occurrences of pathogenic and common SNPs can be attributed to a negative selection on random mutations in structurally highly constrained regions. New approaches in the study of quantitative effects of pathogenic-related mutations should effectively account for all the possible contexts and relative functional constraints in which the sequence variation occurs.
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Affiliation(s)
- Hui-Chun Lu
- Randall Division of Cell and Molecular Biophysics, King's College London London, UK
| | - Sun Sook Chung
- Randall Division of Cell and Molecular Biophysics, King's College London London, UK ; Department of Haematological Medicine, King's College London London, UK
| | - Arianna Fornili
- Randall Division of Cell and Molecular Biophysics, King's College London London, UK ; School of Biological and Chemical Sciences, Queen Mary University of London London, UK
| | - Franca Fraternali
- Randall Division of Cell and Molecular Biophysics, King's College London London, UK
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162
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Chen TY, Kuo SH, Chen ST, Hwang DF. Differential proteomics to explore the inhibitory effects of acidic, slightly acidic electrolysed water and sodium hypochlorite solution on Vibrio parahaemolyticus. Food Chem 2015; 194:529-37. [PMID: 26471589 DOI: 10.1016/j.foodchem.2015.08.019] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2015] [Revised: 07/24/2015] [Accepted: 08/06/2015] [Indexed: 01/18/2023]
Abstract
Slightly acidic electrolysed water (SlAEW) and acidic electrolysed water (AEW) have been demonstrated to effectively inactivate food-borne pathogens. However, the underlying mechanism of inactivation remains unknown. Therefore, in this study, a differential proteomic platform was used to investigate the bactericidal mechanism of SlAEW, AEW, and sodium hypochlorite (NaOCl) solutions against Vibrio parahaemolyticus. The upregulated proteins after SlAEW, AEW, and NaOCl treatments were identified as outer membrane proteins K and U. The downregulated proteins after the SlAEW, AEW, and NaOCl treatments were identified as adenylate kinase, phosphoglycerate kinase, glyceraldehyde-3-phosphate dehydrogenase (GAPDH), and enolase, all of which are responsible for energy metabolism. Protein synthesis-associated proteins were downregulated and identified as elongation factor Tu and GAPDH. The inhibitory effects of SlAEW and AEW solutions against V. parahaemolyticus may be attributed to the changes in cell membrane permeability, protein synthesis activity, and adenosine triphosphate (ATP) biosynthesis pathways such as glycolysis and ATP replenishment.
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Affiliation(s)
- Tai-Yuan Chen
- Department of Food Science, Center of Excellence for the Oceans, National Taiwan Ocean University, Keelung 202, Taiwan, ROC.
| | - Shu-Hao Kuo
- Department of Food Science, Center of Excellence for the Oceans, National Taiwan Ocean University, Keelung 202, Taiwan, ROC
| | - Shui-Tein Chen
- Institute of Biological Chemistry, Academia Sinica, Taipei 115, Taiwan, ROC
| | - Deng-Fwu Hwang
- Department of Food Science, Center of Excellence for the Oceans, National Taiwan Ocean University, Keelung 202, Taiwan, ROC
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163
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Suss O, Reichmann D. Protein plasticity underlines activation and function of ATP-independent chaperones. Front Mol Biosci 2015; 2:43. [PMID: 26284255 PMCID: PMC4516975 DOI: 10.3389/fmolb.2015.00043] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2015] [Accepted: 07/13/2015] [Indexed: 12/31/2022] Open
Abstract
One of the key issues in biology is to understand how cells cope with protein unfolding caused by changes in their environment. Self-protection is the natural immediate response to any sudden threat and for cells the critical issue is to prevent aggregation of existing proteins. Cellular response to stress is therefore indistinguishably linked to molecular chaperones, which are the first line of defense and function to efficiently recognize misfolded proteins and prevent their aggregation. One of the major protein families that act as cellular guards includes a group of ATP-independent chaperones, which facilitate protein folding without the consumption of ATP. This review will present fascinating insights into the diversity of ATP-independent chaperones, and the variety of mechanisms by which structural plasticity is utilized in the fine-tuning of chaperone activity, as well as in crosstalk within the proteostasis network. Research into this intriguing class of chaperones has introduced new concepts of stress response to a changing cellular environment, and paved the way to uncover how this environment affects protein folding.
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Affiliation(s)
- Ohad Suss
- Department of Biological Chemistry, The Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem Jerusalem, Israel
| | - Dana Reichmann
- Department of Biological Chemistry, The Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem Jerusalem, Israel
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164
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Martin NL, Bass P, Liss SN. Antibacterial Properties and Mechanism of Activity of a Novel Silver-Stabilized Hydrogen Peroxide. PLoS One 2015; 10:e0131345. [PMID: 26154263 PMCID: PMC4496041 DOI: 10.1371/journal.pone.0131345] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2015] [Accepted: 06/01/2015] [Indexed: 11/18/2022] Open
Abstract
Huwa-San peroxide (hydrogen peroxide; HSP) is a NSF Standard 60 (maximum 8 mg/L(-1)) new generation peroxide stabilized with ionic silver suitable for continuous disinfection of potable water. Experiments were undertaken to examine the mechanism of HSP against planktonic and biofilm cultures of indicator bacterial strains. Contact/kill time (CT) relationships that achieve effective control were explored to determine the potential utility in primary disinfection. Inhibitory assays were conducted using both nutrient rich media and a medium based on synthetic wastewater. Assays were compared for exposures to three disinfectants (HSP, laboratory grade hydrogen peroxide (HP) and sodium hypochlorite) at concentrations of 20 ppm (therefore at 2.5 and 5 times the NSF limit for HP and sodium hypochlorite, respectively) and at pH 7.0 and 8.5 in dechlorinated tap water. HSP was found to be more or equally effective as hypochlorite or HP. Results from CT assays comparing HSP and HP at different bacterial concentrations with neutralization of residual peroxide with catalase suggested that at a high bacterial concentration HSP, but not HP, was protected from catalase degradation possibly through sequestration by bacterial cells. Consistent with this hypothesis, at a low bacterial cell density residual HSP was more effectively neutralized as less HSP was associated with bacteria and therefore accessible to catalase. Silver in HSP may facilitate this association through electrostatic interactions at the cell surface. This was supported by experiments where the addition of mono (K(+)) and divalent (Ca(+2)) cations (0.005-0.05M) reduced the killing efficacy of HSP but not HP. Experiments designed to distinguish any inhibitory effect of silver from that of peroxide in HSP were carried out by monitoring the metabolic activity of established P. aeruginosa PAO1 biofilms. Concentrations of 70-500 ppm HSP had a pronounced effect on metabolic activity while the equivalent concentrations of ionic silver (50- 375 ppb) had a negligible effect, demonstrating that the microbiocidal activity of HSP was due to peroxide rather than silver. Overall, it was found that the antimicrobial activity of HSP is enhanced over that of hydrogen peroxide; the presence of the ionic silver enhances interactions of HSP with the bacterial cell surface rather than acting directly as a biocide at the tested concentrations.
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Affiliation(s)
- Nancy L. Martin
- Department of Biomedical and Molecular Sciences, Queen's University, Kingston, Ontario, Canada
| | - Paul Bass
- School of Environmental Studies, Queen's University, Kingston, Ontario, Canada
| | - Steven N. Liss
- School of Environmental Studies, Queen's University, Kingston, Ontario, Canada
- Department of Chemical Engineering, Queen's University, Kingston, Ontario, Canada
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165
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Abstract
The era in which ROS (reactive oxygen species) were simply the 'bad boys of biology' is clearly over. High levels of ROS are still rightfully considered to be toxic to many cellular processes and, as such, contribute to disease conditions and cell death. However, the high toxicity of ROS is also extremely beneficial, particularly as it is used to kill invading micro-organisms during mammalian host defence. Moreover, a transient, often more localized, increase in ROS levels appears to play a major role in signal transduction processes and positively affects cell growth, development and differentiation. At the heart of all these processes are redox-regulated proteins, which use oxidation-sensitive cysteine residues to control their function and by extension the function of the pathways that they are part of. Our work has contributed to changing the view about ROS through: (i) our characterization of Hsp33 (heat-shock protein 33), one of the first redox-regulated proteins identified, whose function is specifically activated by ROS, (ii) the development of quantitative tools that reveal extensive redox-sensitive processes in bacteria and eukaryotes, and (iii) the discovery of a link between early exposure to oxidants and aging. Our future research programme aims to generate an integrated and system-wide view of the beneficial and deleterious effects of ROS with the central goal to develop more effective antioxidant strategies and more powerful antimicrobial agents.
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166
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Metabolic Response of Escherichia coli upon Treatment with Hypochlorite at Sub-Lethal Concentrations. PLoS One 2015; 10:e0125823. [PMID: 25932918 PMCID: PMC4416902 DOI: 10.1371/journal.pone.0125823] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2014] [Accepted: 03/25/2015] [Indexed: 01/11/2023] Open
Abstract
Hypochlorite is a reactive oxygen species that is worldwide as an antibacterial disinfectant. Hypochlorite exposure is known to cause oxidative damage to DNA and proteins. As a response to these effects, the metabolite profiles of organisms treated with sub-lethal doses of hypochlorite are assumed to be severely modified; however, the nature of these changes is hardly understood. Therefore, using nuclear magnetic resonance spectroscopy and gas chromatography-coupled mass spectrometry, we analyzed the time-dependent impact of hypochlorite exposure with a sub-lethal concentration (50 µM) on the metabolite profile of the Escherichia coli strain MG1655. Principle component analysis clearly distinguished between the metabolite profiles of bacteria treated for 0, 5,10, 20, 40, or 60 min. Major changes in the relative amounts of fatty acids, acetic acid, and formic acid occurred within the first 5 min. Comparative gas chromatography-coupled mass spectrometry analyses revealed that the amounts of free methionine and alanine were significantly decreased in the treated cells, demonstrating their susceptibility to hypochlorite exposure. The concentrations of succinate, urea, orotic acid, 2-aminobutyric acid, and 2-hydroxybutyric acid were also severely affected, indicating general changes in the metabolic network by hypochlorite. However, most metabolite levels relaxed to the reference values of untreated cells after 40–60 min, reflecting the capability of E. coli to rapidly adapt to environmental stress factors such as the presence of sub-lethal oxidant levels.
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167
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Dahl JU, Gray MJ, Jakob U. Protein quality control under oxidative stress conditions. J Mol Biol 2015; 427:1549-63. [PMID: 25698115 PMCID: PMC4357566 DOI: 10.1016/j.jmb.2015.02.014] [Citation(s) in RCA: 117] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2015] [Revised: 02/11/2015] [Accepted: 02/11/2015] [Indexed: 12/22/2022]
Abstract
Accumulation of reactive oxygen and chlorine species (RO/CS) is generally regarded to be a toxic and highly undesirable event, which serves as contributing factor in aging and many age-related diseases. However, it is also put to excellent use during host defense, when high levels of RO/CS are produced to kill invading microorganisms and regulate bacterial colonization. Biochemical and cell biological studies of how bacteria and other microorganisms deal with RO/CS have now provided important new insights into the physiological consequences of oxidative stress, the major targets that need protection, and the cellular strategies employed by organisms to mitigate the damage. This review examines the redox-regulated mechanisms by which cells maintain a functional proteome during oxidative stress. We will discuss the well-characterized redox-regulated chaperone Hsp33, and we will review recent discoveries demonstrating that oxidative stress-specific activation of chaperone function is a much more widespread phenomenon than previously anticipated. New members of this group include the cytosolic ATPase Get3 in yeast, the Escherichia coli protein RidA, and the mammalian protein α2-macroglobulin. We will conclude our review with recent evidence showing that inorganic polyphosphate (polyP), whose accumulation significantly increases bacterial oxidative stress resistance, works by a protein-like chaperone mechanism. Understanding the relationship between oxidative and proteotoxic stresses will improve our understanding of both host-microbe interactions and how mammalian cells combat the damaging side effects of uncontrolled RO/CS production, a hallmark of inflammation.
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Affiliation(s)
- Jan-Ulrik Dahl
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI 48109-1048, USA
| | - Michael J Gray
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI 48109-1048, USA
| | - Ursula Jakob
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI 48109-1048, USA.
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168
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Gil MI, Gómez-López VM, Hung YC, Allende A. Potential of Electrolyzed Water as an Alternative Disinfectant Agent in the Fresh-Cut Industry. FOOD BIOPROCESS TECH 2015. [DOI: 10.1007/s11947-014-1444-1] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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169
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Nascimento MA, Magri ME, Schissi CD, Barardi CR. Recombinant adenovirus as a model to evaluate the efficiency of free chlorine disinfection in filtered water samples. Virol J 2015; 12:30. [PMID: 25889833 PMCID: PMC4349469 DOI: 10.1186/s12985-015-0259-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2014] [Accepted: 02/03/2015] [Indexed: 01/12/2023] Open
Abstract
BACKGROUND In Brazil, ordinance no. 2,914/2011 of the Ministry of Health requires the absence of total coliforms and Escherichia coli (E. coli) in treated water. However it is essential that water treatment is effective against all pathogens. Disinfection in Water Treatment Plants (WTP) is commonly performed with chlorine. METHODS The recombinant adenovirus (rAdV), which expresses green fluorescent protein (GFP) when cultivated in HEK 293A cells, was chosen as a model to evaluate the efficiency of chlorine for human adenovirus (HAdV) inactivation in filtered water samples from two WTPs: Lagoa do Peri (pH 6.9) and Morro dos Quadros (pH 6.5). Buffered demand free (BDF) water (pH 6.9 and 8.0) was used as control. The samples were previously submitted to physicochemical characterization, and bacteriological analysis. Two free chlorine concentrations and two temperatures were assayed for all samples (0.2 mg/L, 0.5 mg/L, and 15°C, and 20°C). Fluorescence microscopy (FM) was used to check viral infectivity in vitro and qPCR as a molecular method to determine viral genome copies. Real treated water samples from the WTP (at the output of WTP and the distribution network) were also evaluated for total coliforms, E. coli and HAdV. RESULTS The time required to inactivate 4log₁₀ of rAdV was less than 1 min, when analyzed by FM, except for BDF pH 8.0 (up to 2.5 min for 4log₁₀). The pH had a significant influence on the efficiency of disinfection. The qPCR assay was not able to provide information regarding rAdV inactivation. The data were modeled (Chick-Watson), and the observed Ct values were comparable with the values reported in the literature and smaller than the values recommended by the EPA. In the treated water samples, HAdV was detected in the distribution network of the WTP Morro dos Quadros (2.75 × 10(3) PFU/L). CONCLUSION The Chick-Watson model proved to have adjusted well to the experimental conditions used, and it was possible to prove that the adenoviruses were rapidly inactivated in the surface water treated with chlorine and that the recombinant adenovirus expressing GFP is a good model for this evaluation.
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Affiliation(s)
- Mariana A Nascimento
- Laboratório de Virologia Aplicada, Departamento de Microbiologia, Imunologia e Parasitologia, Universidade Federal de Santa Catarina, 88040-900, Florianópolis, Santa Catarina, Brazil.
| | - Maria E Magri
- Laboratório de Virologia Aplicada, Departamento de Microbiologia, Imunologia e Parasitologia, Universidade Federal de Santa Catarina, 88040-900, Florianópolis, Santa Catarina, Brazil.
| | - Camila D Schissi
- Laboratório de Virologia Aplicada, Departamento de Microbiologia, Imunologia e Parasitologia, Universidade Federal de Santa Catarina, 88040-900, Florianópolis, Santa Catarina, Brazil.
| | - Célia Rm Barardi
- Laboratório de Virologia Aplicada, Departamento de Microbiologia, Imunologia e Parasitologia, Universidade Federal de Santa Catarina, 88040-900, Florianópolis, Santa Catarina, Brazil.
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170
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Du Z, Nandakumar R, Nickerson KW, Li X. Proteomic adaptations to starvation prepare Escherichia coli for disinfection tolerance. WATER RESEARCH 2015; 69:110-119. [PMID: 25463932 PMCID: PMC4351261 DOI: 10.1016/j.watres.2014.11.016] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/07/2014] [Revised: 11/10/2014] [Accepted: 11/12/2014] [Indexed: 05/10/2023]
Abstract
Despite the low nutrient level and constant presence of secondary disinfectants, bacterial re-growth still occurs in drinking water distribution systems. The molecular mechanisms that starved bacteria use to survive low-level chlorine-based disinfectants are not well understood. The objective of this study is to investigate these molecular mechanisms at the protein level that prepare starved cells for disinfection tolerance. Two commonly used secondary disinfectants chlorine and monochloramine, both at 1 mg/L, were used in this study. The proteomes of normal and starved Escherichia coli (K12 MG1655) cells were studied using quantitative proteomics. Over 60-min disinfection, starved cells showed significantly higher disinfection tolerance than normal cells based on the inactivation curves for both chlorine and monochloramine. Proteomic analyses suggest that starvation may prepare cells for the oxidative stress that chlorine-based disinfection will cause by affecting glutathione metabolism. In addition, proteins involved in stress regulation and stress responses were among the ones up-regulated under both starvation and chlorine/monochloramine disinfection. By comparing the fold changes under different conditions, it is suggested that starvation prepares E. coli for disinfection tolerance by increasing the expression of enzymes that can help cells survive chlorine/monochloramine disinfection. Protein co-expression analyses show that proteins in glycolysis and pentose phosphate pathway that were up-regulated under starvation are also involved in disinfection tolerance. Finally, the production and detoxification of methylglyoxal may be involved in the chlorine-based disinfection and cell defense mechanisms.
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Affiliation(s)
- Zhe Du
- Department of Civil Engineering, University of Nebraska-Lincoln, USA
| | - Renu Nandakumar
- Proteomics and Metabolomics Core Facility, Redox Biology Center, Department of Biochemistry, University of Nebraska-Lincoln, USA
| | | | - Xu Li
- Department of Civil Engineering, University of Nebraska-Lincoln, USA.
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171
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Theoretical insights into the mechanism of redox switch in heat shock protein Hsp33. J Biol Inorg Chem 2015; 20:555-62. [PMID: 25637463 DOI: 10.1007/s00775-015-1240-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2014] [Accepted: 01/10/2015] [Indexed: 10/24/2022]
Abstract
Heat shock protein 33 (Hsp33) is activated in the presence of H2O2 by a very interesting redox switch based on a tetra-coordinated zinc-cysteine complex present in the fully reduced and inactive protein form. The oxidation of this zinc center by H2O2 induces formation of two S-S bridges and the zinc release followed by the protein unfolding. We report here a theoretical study of the step-by-step sequence of the overall process starting with the oxidation of the first cysteine residue and ending with the zinc release. Each reaction step is characterized by its Gibbs free energy barrier (∆G (‡)). It is predicted that the first reaction step consists in the oxidation of Cys263 by H2O2 which is by far the most reactive cysteine (∆G (‡) = 15.4 kcal mol(-1)). The next two reaction steps are the formation of the first S-S bridge between Cys263 and Cys266 (∆G (‡) = 13.6 kcal mol(-1)) and the oxidation of Cys231 by H2O2 (∆G (‡) = 20.4 kcal mol(-1)). It is then shown that the formation of the second S-S bridge (Cys231-Cys233) before the zinc release is most unlikely (∆G (‡) = 34.8 kcal mol(-1)). Instead, the release of zinc just after the oxidation of the third cysteine (Cys231) is shown to be thermodynamically (dissociation Gibbs free energy ∆G d = 6.0 kcal mol(-1)) and kinetically (reaction rate constant k d ≈ 10(6) s(-1)) favored. This result is in good agreement with the experimental data on the oxidation mechanism of Hsp33 zinc center available to date.
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172
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Oxidative stress control by apicomplexan parasites. BIOMED RESEARCH INTERNATIONAL 2015; 2015:351289. [PMID: 25722976 PMCID: PMC4324108 DOI: 10.1155/2015/351289] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/03/2014] [Accepted: 10/27/2014] [Indexed: 01/01/2023]
Abstract
Apicomplexan parasites cause infectious diseases that are either a severe public health problem or an economic burden. In this paper we will shed light on how oxidative stress can influence the host-pathogen relationship by focusing on three major diseases: babesiosis, coccidiosis, and toxoplasmosis.
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173
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Celis AI, Geeraerts Z, Ngmenterebo D, Machovina MM, Kurker RC, Rajakumar K, Ivancich A, Rodgers KR, Lukat-Rodgers GS, DuBois JL. A dimeric chlorite dismutase exhibits O2-generating activity and acts as a chlorite antioxidant in Klebsiella pneumoniae MGH 78578. Biochemistry 2014; 54:434-46. [PMID: 25437493 PMCID: PMC4303309 DOI: 10.1021/bi501184c] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
![]()
Chlorite
dismutases (Clds) convert chlorite to O2 and
Cl–, stabilizing heme in the presence of strong
oxidants and forming the O=O bond with high efficiency. The
enzyme from the pathogen Klebsiella pneumoniae (KpCld) represents a subfamily of Clds that share most of
their active site structure with efficient O2-producing
Clds, even though they have a truncated monomeric structure, exist
as a dimer rather than a pentamer, and come from Gram-negative bacteria
without a known need to degrade chlorite. We hypothesized that KpCld, like others in its subfamily, should be able to make
O2 and may serve an in vivo antioxidant
function. Here, it is demonstrated that it degrades chlorite with
limited turnovers relative to the respiratory Clds, in part because
of the loss of hypochlorous acid from the active site and destruction
of the heme. The observation of hypochlorous acid, the expected leaving
group accompanying transfer of an oxygen atom to the ferric heme,
is consistent with the more open, solvent-exposed heme environment
predicted by spectroscopic measurements and inferred from the crystal
structures of related proteins. KpCld is more susceptible
to oxidative degradation under turnover conditions than the well-characterized
Clds associated with perchlorate respiration. However, wild-type K. pneumoniae has a significant growth advantage in the
presence of chlorate relative to a Δcld knockout
strain, specifically under nitrate-respiring conditions. This suggests
that a physiological function of KpCld may be detoxification
of endogenously produced chlorite.
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Affiliation(s)
- Arianna I Celis
- Department of Chemistry and Biochemistry, Montana State University , Bozeman, Montana 59715, United States
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174
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Müller A, Langklotz S, Lupilova N, Kuhlmann K, Bandow JE, Leichert LIO. Activation of RidA chaperone function by N-chlorination. Nat Commun 2014; 5:5804. [PMID: 25517874 PMCID: PMC4284807 DOI: 10.1038/ncomms6804] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2014] [Accepted: 11/07/2014] [Indexed: 12/25/2022] Open
Abstract
Escherichia coli RidA is a member of a structurally conserved, yet functionally highly diverse protein family involved in translation inhibition (human), Hsp90-like chaperone activity (fruit fly) and enamine/imine deamination (Salmonella enterica). Here, we show that E. coli RidA modified with HOCl acts as a highly effective chaperone. Although activation of RidA is reversed by treatment with DTT, ascorbic acid, the thioredoxin system and glutathione, it is independent of cysteine modification. Instead, treatment with HOCl or chloramines decreases the amino group content of RidA by reversibly N-chlorinating positively charged residues. N-chlorination increases hydrophobicity of RidA and promotes binding to a wide spectrum of unfolded cytosolic proteins. Deletion of ridA results in an HOCl-sensitive phenotype. HOCl-mediated N-chlorination thus is a cysteine-independent post-translational modification that reversibly turns RidA into an effective chaperone holdase, which plays a crucial role in the protection of cytosolic proteins during oxidative stress. Hypochlorous acid generated by neutrophils acts as a potent antibacterial agent. Müller et al. now show that this oxidant directly activates a protective counter-response in E. coli by N-chlorinating the protein RidA and converting it into an effective protein chaperone.
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Affiliation(s)
- Alexandra Müller
- Institute of Biochemistry and Pathobiochemistry-Microbial Biochemistry, Ruhr-Universität Bochum, Universitätsstrasse 150, 44780 Bochum, Germany
| | - Sina Langklotz
- Biology of Microorganisms, Ruhr-Universität Bochum, Universitätsstrasse 150, 44780 Bochum, Germany
| | - Nataliya Lupilova
- Institute of Biochemistry and Pathobiochemistry-Microbial Biochemistry, Ruhr-Universität Bochum, Universitätsstrasse 150, 44780 Bochum, Germany
| | - Katja Kuhlmann
- Medizinisches Proteom-Center, Ruhr-Universität Bochum, Universitätsstrasse 150, 44780 Bochum, Germany
| | - Julia Elisabeth Bandow
- Biology of Microorganisms, Ruhr-Universität Bochum, Universitätsstrasse 150, 44780 Bochum, Germany
| | - Lars Ingo Ole Leichert
- Institute of Biochemistry and Pathobiochemistry-Microbial Biochemistry, Ruhr-Universität Bochum, Universitätsstrasse 150, 44780 Bochum, Germany
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175
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Lee M, Van Bever H. The role of antiseptic agents in atopic dermatitis. Asia Pac Allergy 2014; 4:230-40. [PMID: 25379483 PMCID: PMC4215429 DOI: 10.5415/apallergy.2014.4.4.230] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2014] [Accepted: 09/12/2014] [Indexed: 11/04/2022] Open
Abstract
The skin of individuals with atopic dermatitis has a susceptibility to be colonized with Staphylococcus aureus. This has been associated with increased frequency and severity of exacerbations of atopic dermatitis. Therefore, there is a growing interest in the use of antiseptic agents to target primary bacterial colonization and infection. Antiseptic agents have been found to be better tolerated and less likely to induce bacterial resistance as compared to antibiotics. There is also a wide variety of antiseptic agents available. The efficacy of antiseptic agents has yet to be established as the studies reviewed previously have been small and of suboptimal quality. This review discusses the rationale behind targeting S. aureus with antiseptic agents and presents findings from a review of studies assessing the efficacy of antiseptics in atopic dermatitis in the last five years. Four studies were found, including a bleach bath study which has already been reviewed elsewhere. The remaining 3 studies assessed the efficacy of sodium hypochlorite containing cleansing body wash, sodium hypochlorite baths and 1% triclosan in leave on emollient. These studies suggested some benefit for the inclusion of antiseptic use with the mainstay management of atopic dermatitis, including a potential steroid sparring effect. However, there are many limitations to these studies which therefore warrant further investigation on the impact of antiseptic use in atopic dermatitis.
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Affiliation(s)
- Melissa Lee
- Department of Paediatrics, University Children's Medical Institute, Yong Loo Lin School of Medicine, Singapore 119077, Singapore
| | - Hugo Van Bever
- Department of Paediatrics, University Children's Medical Institute, Yong Loo Lin School of Medicine, Singapore 119077, Singapore
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176
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Omotade TO, Bernhards RC, Klimko CP, Matthews ME, Hill AJ, Hunter MS, Webster WM, Bozue JA, Welkos SL, Cote CK. The impact of inducing germination of Bacillus anthracis and Bacillus thuringiensis spores on potential secondary decontamination strategies. J Appl Microbiol 2014; 117:1614-33. [PMID: 25196092 DOI: 10.1111/jam.12644] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2014] [Revised: 09/03/2014] [Accepted: 09/03/2014] [Indexed: 12/22/2022]
Abstract
AIMS Decontamination and remediation of a site contaminated by the accidental or intentional release of fully virulent Bacillus anthracis spores are difficult, costly and potentially damaging to the environment. Development of novel decontamination strategies that have minimal environmental impacts remains a high priority. Although ungerminated spores are amongst the most resilient organisms known, once exposed to germinants, the germinating spores, in some cases, become susceptible to antimicrobial environments. We evaluated the concept that once germinated, B. anthracis spores would be less hazardous and significantly easier to remediate than ungerminated dormant spores. METHODS AND RESULTS Through in vitro germination and sensitivity assays, we demonstrated that upon germination, B. anthracis Ames spores and Bacillus thuringiensis Al Hakam spores (serving as a surrogate for B. anthracis) become susceptible to environmental stressors. The majority of these germinated B. anthracis and B. thuringiensis spores were nonviable after exposure to a defined minimal germination-inducing solution for prolonged periods of time. Additionally, we examined the impact of potential secondary disinfectant strategies including bleach, hydrogen peroxide, formaldehyde and artificial UV-A, UV-B and UV-C radiation, employed after a 60-min germination-induction step. Each secondary disinfectant employs a unique mechanism of killing; as a result, germination-induction strategies are better suited for some secondary disinfectants than others. CONCLUSIONS These results provide evidence that the deployment of an optimal combination strategy of germination-induction/secondary disinfection may be a promising aspect of wide-area decontamination following a B. anthracis contamination event. SIGNIFICANCE AND IMPACT OF THE STUDY By inducing spores to germinate, our data confirm that the resulting cells exhibit sensitivities that can be leveraged when paired with certain decontamination measures. This increased susceptibility could be exploited to devise more efficient and safe decontamination measures and may obviate the need for more stringent methods that are currently in place.
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Affiliation(s)
- T O Omotade
- Bacteriology Division, United States Army Medical Research Institute of Infectious Diseases (USAMRIID), Frederick, MD, USA
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177
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Groitl B, Jakob U. Thiol-based redox switches. BIOCHIMICA ET BIOPHYSICA ACTA 2014; 1844:1335-43. [PMID: 24657586 PMCID: PMC4059413 DOI: 10.1016/j.bbapap.2014.03.007] [Citation(s) in RCA: 168] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/13/2014] [Revised: 03/04/2014] [Accepted: 03/11/2014] [Indexed: 11/30/2022]
Abstract
Regulation of protein function through thiol-based redox switches plays an important role in the response and adaptation to local and global changes in the cellular levels of reactive oxygen species (ROS). Redox regulation is used by first responder proteins, such as ROS-specific transcriptional regulators, chaperones or metabolic enzymes to protect cells against mounting levels of oxidants, repair the damage and restore redox homeostasis. Redox regulation of phosphatases and kinases is used to control the activity of select eukaryotic signaling pathways, making reactive oxygen species important second messengers that regulate growth, development and differentiation. In this review we will compare different types of reversible protein thiol modifications, elaborate on their structural and functional consequences and discuss their role in oxidative stress response and ROS adaptation. This article is part of a Special Issue entitled: Thiol-Based Redox Processes.
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Affiliation(s)
- Bastian Groitl
- Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Ursula Jakob
- Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, MI 48109, USA; Department of Biological Chemistry, University of Michigan, Ann Arbor, MI 48109, USA.
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178
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Gundlach J, Winter J. Evolution of Escherichia coli for maximum HOCl resistance through constitutive expression of the OxyR regulon. Microbiology (Reading) 2014; 160:1690-1704. [DOI: 10.1099/mic.0.074815-0] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Exposure of cells to stress impairs cellular functions and may cause killing or adaptation. Adaptation can be facilitated by stress-induced mutagenesis or epigenetic changes, i.e. phenotypic variation without mutations. Upon exposure to HOCl, which is produced by the innate immune system upon bacterial infection, bacteria trigger stress responses that enable increased survival against the stress. Here, we addressed the question whether bacteria can adapt to high HOCl doses and if so, how the acquired resistance is facilitated. We evolved Escherichia coli cells for maximum HOCl resistance by successively increasing the HOCl concentration in the cultivation medium. HOCl-resistant cells showed broad stress resistance but did not carry any chromosomal mutations as revealed by whole-genome sequencing. According to proteome analysis and analysis of transcript levels of stress-related genes, HOCl resistance was accompanied by altered levels of outer-membrane proteins A, C, F and W, and, most prominently, a constitutively expressed OxyR regulon. Induction of the OxyR regulon is facilitated by a partially oxidized OxyR leading to increased levels of antioxidant proteins such as Dps, AhpC/AhpF and KatG. These changes were maintained in evolved strains even when they were cultivated without stress for a prolonged time, indicating epigenetic changes contributed to stress resistance. This indicated that maximum HOCl resistance was conferred by the accumulated action of the OxyR stress response and other factors such as altered levels of outer-membrane proteins.
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Affiliation(s)
- Jasmin Gundlach
- Center for Integrated Protein Science Munich, Department Chemie, Technische Universität München, 85747 Garching, Germany
| | - Jeannette Winter
- Center for Integrated Protein Science Munich, Department Chemie, Technische Universität München, 85747 Garching, Germany
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179
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Jakob U, Kriwacki R, Uversky VN. Conditionally and transiently disordered proteins: awakening cryptic disorder to regulate protein function. Chem Rev 2014; 114:6779-805. [PMID: 24502763 PMCID: PMC4090257 DOI: 10.1021/cr400459c] [Citation(s) in RCA: 145] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Affiliation(s)
- Ursula Jakob
- Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, Michigan 48109-1048, United States
| | - Richard Kriwacki
- Department of Structural Biology, St. Jude Children’s Research Hospital, Memphis, Tennessee 38105, United States
- Department of Microbiology, Immunology and Biochemistry, University of Tennessee Health Science Center, Memphis, Tennessee 38163, United States
| | - Vladimir N. Uversky
- Department of Molecular Medicine, University of South Florida, Tampa, Florida 33612, United States
- Institute for Biological Instrumentation, Russian Academy of Sciences, 142290 Pushchino, Moscow Region, Russia
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180
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Macedo RG, Herrero NP, Wesselink P, Versluis M, van der Sluis L. Influence of the Dentinal Wall on the pH of Sodium Hypochlorite during Root Canal Irrigation. J Endod 2014; 40:1005-8. [DOI: 10.1016/j.joen.2013.12.018] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2013] [Revised: 12/15/2013] [Accepted: 12/16/2013] [Indexed: 10/25/2022]
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181
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Nauseef WM. Myeloperoxidase in human neutrophil host defence. Cell Microbiol 2014; 16:1146-55. [PMID: 24844117 DOI: 10.1111/cmi.12312] [Citation(s) in RCA: 170] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2014] [Revised: 05/02/2014] [Accepted: 05/13/2014] [Indexed: 12/21/2022]
Abstract
Human neutrophils represent the predominant leucocyte in circulation and the first responder to infection. Concurrent with ingestion of microorganisms, neutrophils activate and assemble the NADPH oxidase at the phagosome, thereby generating superoxide anion and hydrogen peroxide. Concomitantly, granules release their contents into the phagosome, where the antimicrobial proteins and enzymes synergize with oxidants to create an environment toxic to the captured microbe. The most rapid and complete antimicrobial action by human neutrophils against many organisms relies on the combined efforts of the azurophilic granule protein myeloperoxidase and hydrogen peroxide from the NADPH oxidase to oxidize chloride, thereby generating hypochlorous acid and a host of downstream reaction products. Although individual components of the neutrophil antimicrobial response exhibit specific activities in isolation, the situation in the environment of the phagosome is far more complicated, a consequence of multiple and complex interactions among oxidants, proteins and their by-products. In most cases, the cooperative interactions among the phagosomal contents, both from the host and the microbe, culminate in loss of viability of the ingested organism.
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Affiliation(s)
- William M Nauseef
- Inflammation Program, Department of Medicine, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, IA, USA; Veterans Administration Medical Center, Iowa City, IA, 52242, USA
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182
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Moore JE, Rendall JC. Comparison of susceptibility of cystic-fibrosis-related and non-cystic-fibrosis-related Pseudomonas aeruginosa to chlorine-based disinfecting solutions: implications for infection prevention and ward disinfection. J Med Microbiol 2014; 63:1214-1219. [PMID: 24925907 DOI: 10.1099/jmm.0.071050-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Multidrug-resistant (MDR) Pseudomonas aeruginosa isolated from cystic fibrosis (CF) sputum was shown to be more tolerant to the most commonly used chlorine-based disinfecting agent in the UK, with approximately 7 out of 10 isolates surviving a residual free chlorine (RFC) concentration of 500 p.p.m., when compared with antibiotic-sensitive invasive P. aeruginosa from a non-CF blood culture source, where 8 out of 10 isolates were killed at a RFC concentration of 100 p.p.m. All CF isolates were killed at 1000 p.p.m. chlorine. Additional studies were performed to examine factors that influenced the concentration of RFC from chlorine-based (sodium dichloroisocyanurate) disinfecting agents in contact with CF sputum and their components (bacterial cells, glycocalyx) to assess the reduction of the bactericidal activity of such disinfecting agents. Pseudomonas glycocalyx had a greater inhibitory effect of chlorine deactivation than bacterial cells. Calibration curves demonstrated the relative deactivating capacity on RFC from clinical soils, in the order pus>CF sputum>wound discharge fluid/synovial fluid>ascites fluid>bile, where quantitatively each 1 % (w/v) CF sputum reduced the RFC by 43 p.p.m. Sublethal stressing of P. aeruginosa with chlorine resulted in lowered susceptibility to colistin (P = 0.0326) but not to meropenem, tobramycin or ciprofloxacin. In conclusion, heavy contamination of healthcare fomites with CF sputum containing MDR P. aeruginosa may result in exhaustion of RFC, and this, combined with an increased resistance to chlorine with such strains, may lead to their survival and increased antibiotic resistance in such environments. CF infection prevention strategies in such scenarios should therefore target interventions with increased concentrations of chlorine to ensure the eradication of MDR P. aeruginosa from the CF healthcare environment.
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Affiliation(s)
- John E Moore
- Northern Ireland Public Health Laboratory, Department of Bacteriology, Belfast City Hospital, Lisburn Road, Belfast BT9 7AD, UK.,Centre for Infection & Immunity, Queen's University, Health Sciences Building, Lisburn Road, Belfast BT9 7BL, UK.,Northern Ireland Regional Adult Cystic Fibrosis Centre, Level 8, Belfast City Hospital, Lisburn Road, Belfast BT9 7AB, UK.,School of Biomedical Sciences, University of Ulster, Cromore Road, Coleraine BT52 1SA, UK
| | - Jacqueline C Rendall
- Northern Ireland Regional Adult Cystic Fibrosis Centre, Level 8, Belfast City Hospital, Lisburn Road, Belfast BT9 7AB, UK.,Centre for Infection & Immunity, Queen's University, Health Sciences Building, Lisburn Road, Belfast BT9 7BL, UK
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183
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Ryan BJ, Nissim A, Winyard PG. Oxidative post-translational modifications and their involvement in the pathogenesis of autoimmune diseases. Redox Biol 2014; 2:715-24. [PMID: 24955328 PMCID: PMC4062766 DOI: 10.1016/j.redox.2014.05.004] [Citation(s) in RCA: 74] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2014] [Revised: 05/22/2014] [Accepted: 05/23/2014] [Indexed: 02/07/2023] Open
Abstract
Tissue inflammation results in the production of numerous reactive oxygen, nitrogen and chlorine species, in addition to the products of lipid and sugar oxidation. Some of these products are capable of chemically modifying amino acids. This in turn results in changes to the structure and function of proteins. Increasing evidence demonstrates that such oxidative post-translational modifications result in the generation of neo-epitopes capable of eliciting both innate and adaptive immune responses. In this paper, we focus on how free radicals and related chemical species generated in inflammatory environments modulate the antigenicity of self-proteins, resulting in immune responses which involve the generation of autoantibodies against key autoantigens in autoimmune diseases. As examples, we will focus on Ro-60 and C1q in systemic lupus erythematosus, along with type-II collagen in rheumatoid arthritis. This review also covers some of the emerging literature which demonstrates that neo-epitopes generated by oxidation are conserved, as exemplified by the evolutionarily conserved pathogen-associated molecular patterns (PAMPs). We discuss how these observations relate to the pathogenesis of both human autoimmune diseases and inflammatory disease, such as atherosclerosis. The potential for these neo-epitopes and the immune responses against them to act as biomarkers or therapeutic targets is also discussed. Oxidants can generate stable post-translational modifications (PTMs) on proteins. Oxidative PTMs are recognised in evolutionarily-conserved innate immune responses. These PTMs can represent neo-epitopes that break tolerance in autoimmune disease. Antibodies targeting these PTMs in diseases e.g. RA and SLE, can be biomarkers.
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Affiliation(s)
- Brent J. Ryan
- Department of Physiology, Anatomy and Genetics, University of Oxford, South Parks Road, Oxford OX1 3QX, UK
| | - Ahuva Nissim
- Centre for Biochemical Pharmacology, William Harvey Research Institute, Queen Mary, University of London, Charterhouse Square, London EC1M 6BQ, UK
| | - Paul G. Winyard
- University of Exeter Medical School, St Luke's Campus, Exeter, Devon EX1 2LU, UK
- Corresponding author.
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184
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Hypochlorite-induced structural modifications enhance the chaperone activity of human α2-macroglobulin. Proc Natl Acad Sci U S A 2014; 111:E2081-90. [PMID: 24799681 DOI: 10.1073/pnas.1403379111] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Hypochlorite, an oxidant generated in vivo by the innate immune system, kills invading pathogens largely by inducing the misfolding of microbial proteins. Concomitantly, the nonspecific activity of hypochlorite also damages host proteins, and the accumulation of damaged (misfolded) proteins is implicated in the pathology of a variety of debilitating human disorders (e.g., Alzheimer's disease, atherosclerosis, and arthritis). It is well-known that cells respond to oxidative stress by up-regulating proteostasis machinery, but the direct activation of mammalian chaperones by hypochlorite has not, to our knowledge, been previously reported. In this study, we show that hypochlorite-induced modifications of human α2-macroglobulin (α2M) markedly increase its chaperone activity by generating species, particularly dimers formed by dissociation of the native tetramer, which have enhanced surface hydrophobicity. Moreover, dimeric α2M is generated in whole-blood plasma in the presence of physiologically relevant amounts of hypochlorite. The chaperone activity of hypochlorite-modified α2M involves the formation of stable soluble complexes with misfolded client proteins, including heat-denatured enzymes, oxidized fibrinogen, oxidized LDL, and native or oxidized amyloid β-peptide (Aβ1-42). Here, we show that hypochlorite-modified α2M delivers its misfolded cargo to lipoprotein receptors on macrophages and reduces Aβ1-42 neurotoxicity. Our results support the conclusion that α2M is a specialized chaperone that prevents the extracellular accumulation of misfolded and potentially pathogenic proteins, particularly during innate immune system activity.
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185
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Wu J, Fan Y, Ling J. Mechanism of oxidant-induced mistranslation by threonyl-tRNA synthetase. Nucleic Acids Res 2014; 42:6523-31. [PMID: 24744241 PMCID: PMC4041444 DOI: 10.1093/nar/gku271] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Aminoacyl-tRNA synthetases maintain the fidelity during protein synthesis by selective activation of cognate amino acids at the aminoacylation site and hydrolysis of misformed aminoacyl-tRNAs at the editing site. Threonyl-tRNA synthetase (ThrRS) misactivates serine and utilizes an editing site cysteine (C182 in Escherichia coli) to hydrolyze Ser-tRNAThr. Hydrogen peroxide oxidizes C182, leading to Ser-tRNAThr production and mistranslation of threonine codons as serine. The mechanism of C182 oxidation remains unclear. Here we used a chemical probe to demonstrate that C182 was oxidized to sulfenic acid by air, hydrogen peroxide and hypochlorite. Aminoacylation experiments in vitro showed that air oxidation increased the Ser-tRNAThr level in the presence of elongation factor Tu. C182 forms a putative metal binding site with three conserved histidine residues (H73, H77 and H186). We showed that H73 and H186, but not H77, were critical for activating C182 for oxidation. Addition of zinc or nickel ions inhibited C182 oxidation by hydrogen peroxide. These results led us to propose a model for C182 oxidation, which could serve as a paradigm for the poorly understood activation mechanisms of protein cysteine residues. Our work also suggests that bacteria may use ThrRS editing to sense the oxidant levels in the environment.
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Affiliation(s)
- Jiang Wu
- Department of Microbiology and Molecular Genetics, Medical School, University of Texas Health Science Center, Houston, TX 77030, USA
| | - Yongqiang Fan
- Department of Microbiology and Molecular Genetics, Medical School, University of Texas Health Science Center, Houston, TX 77030, USA
| | - Jiqiang Ling
- Department of Microbiology and Molecular Genetics, Medical School, University of Texas Health Science Center, Houston, TX 77030, USA Graduate School of Biomedical Sciences, University of Texas, Houston, TX 77030, USA
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186
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Street TO, Zeng X, Pellarin R, Bonomi M, Sali A, Kelly MJS, Chu F, Agard DA. Elucidating the mechanism of substrate recognition by the bacterial Hsp90 molecular chaperone. J Mol Biol 2014; 426:2393-404. [PMID: 24726919 PMCID: PMC5322795 DOI: 10.1016/j.jmb.2014.04.001] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2014] [Revised: 04/01/2014] [Accepted: 04/02/2014] [Indexed: 11/17/2022]
Abstract
Hsp90 is a conformationally dynamic molecular chaperone known to promote the folding and activation of a broad array of protein substrates ("clients"). Hsp90 is believed to preferentially interact with partially folded substrates, and it has been hypothesized that the chaperone can significantly alter substrate structure as a mechanism to alter the substrate functional state. However, critically testing the mechanism of substrate recognition and remodeling by Hsp90 has been challenging. Using a partially folded protein as a model system, we find that the bacterial Hsp90 adapts its conformation to the substrate, forming a binding site that spans the middle and C-terminal domains of the chaperone. Cross-linking and NMR measurements indicate that Hsp90 binds to a large partially folded region of the substrate and significantly alters both its local and long-range structure. These findings implicate Hsp90's conformational dynamics in its ability to bind and remodel partially folded proteins. Moreover, native-state hydrogen exchange indicates that Hsp90 can also interact with partially folded states only transiently populated from within a thermodynamically stable, native-state ensemble. These results suggest a general mechanism by which Hsp90 can recognize and remodel native proteins by binding and remodeling partially folded states that are transiently sampled from within the native ensemble.
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Affiliation(s)
- Timothy O Street
- Department of Biochemistry, Brandeis University, Waltham, MA 02453, USA.
| | - Xiaohui Zeng
- Department of Molecular, Cellular, and Biomedical Sciences, University of New Hampshire, Durham, NH 03824, USA
| | - Riccardo Pellarin
- Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, CA 94158, USA
| | - Massimiliano Bonomi
- Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, CA 94158, USA
| | - Andrej Sali
- Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, CA 94158, USA
| | - Mark J S Kelly
- Department of Pharmaceutical Chemistry, University of California, San Francisco, CA 94158, USA
| | - Feixia Chu
- Department of Molecular, Cellular, and Biomedical Sciences, University of New Hampshire, Durham, NH 03824, USA
| | - David A Agard
- Department of Biochemistry and Biophysics, University of California, San Francisco, CA 94158, USA; The Howard Hughes Medical Institute, University of California, San Francisco, CA 94158, USA
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187
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Bile salts act as effective protein-unfolding agents and instigators of disulfide stress in vivo. Proc Natl Acad Sci U S A 2014; 111:E1610-9. [PMID: 24706920 DOI: 10.1073/pnas.1401941111] [Citation(s) in RCA: 86] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Commensal and pathogenic bacteria must deal with many different stress conditions to survive in and colonize the human gastrointestinal tract. One major challenge that bacteria encounter in the gut is the high concentration of bile salts, which not only aid in food absorption but also act as effective physiological antimicrobials. The mechanism by which bile salts limit bacterial growth is still largely unknown. Here, we show that bile salts cause widespread protein unfolding and aggregation, affecting many essential proteins. Simultaneously, the bacterial cytosol becomes highly oxidizing, indicative of disulfide stress. Strains defective in reducing oxidative thiol modifications, restoring redox homeostasis, or preventing irreversible protein aggregation under disulfide stress conditions are sensitive to bile salt treatment. Surprisingly, cholate and deoxycholate, two of the most abundant and very closely related physiological bile salts, vary substantially in their destabilizing effects on proteins in vitro and cause protein unfolding of different subsets of proteins in vivo. Our results provide a potential mechanistic explanation for the antimicrobial effects of bile salts, help explain the beneficial effects of bile salt mixtures, and suggest that we have identified a physiological source of protein-unfolding disulfide stress conditions in bacteria.
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188
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Transcriptional and phenotypic responses of Listeria monocytogenes to chlorine dioxide. Appl Environ Microbiol 2014; 80:2951-63. [PMID: 24610841 DOI: 10.1128/aem.00004-14] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Significant food-borne disease outbreaks have occurred from consumption of ready-to-eat foods, including produce, contaminated with Listeria monocytogenes. Challenging food matrices (e.g., cantaloupe, sprouts) with limited processing steps postharvest to reduce pathogen loads have underscored a need for new mitigation strategies. Chlorine dioxide (ClO2) is increasingly being used in produce and other food systems to reduce food-borne pathogen levels. The goal of this study was to characterize the transcriptional response and survival of L. monocytogenes 10403S exposed to ClO2. The transcriptional profile of log-phase cells exposed to 300 mg/liter ClO2 for 15 min was defined by whole-genome microarray. A total of 340 genes were significantly differentially expressed. Among the differentially expressed genes, 223 were upregulated (fold change ≥ 1.5; adjusted P value < 0.05) in role categories responsible for protein fate, cellular processes, and energy metabolism. There were 113 and 16 genes differentially expressed belonging to regulatory networks of σ(B) and CtsR, respectively. We assessed L. monocytogenes 10403S survival after exposure to 100, 300, and 500 mg/liter aqueous ClO2 in brain heart infusion (BHI) broth; there was a significant difference between cells exposed to 500 mg/liter ClO2 and those exposed to all other conditions over time (P value < 0.05). Isogenic ΔsigB and ΔctsR mutants exposed to 300 mg/liter ClO2 were more sensitive to ClO2 than the wild type under the same conditions. These results provide an initial insight into the mechanisms that L. monocytogenes employs to survive sublethal ClO2 and further our understanding of the inactivation mechanisms of this increasingly used sanitizer.
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189
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Gray MJ, Wholey WY, Wagner NO, Cremers CM, Mueller-Schickert A, Hock NT, Krieger AG, Smith EM, Bender RA, Bardwell JCA, Jakob U. Polyphosphate is a primordial chaperone. Mol Cell 2014; 53:689-99. [PMID: 24560923 DOI: 10.1016/j.molcel.2014.01.012] [Citation(s) in RCA: 234] [Impact Index Per Article: 23.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2013] [Revised: 12/10/2013] [Accepted: 01/16/2014] [Indexed: 11/29/2022]
Abstract
Composed of up to 1,000 phospho-anhydride bond-linked phosphate monomers, inorganic polyphosphate (polyP) is one of the most ancient, conserved, and enigmatic molecules in biology. Here we demonstrate that polyP functions as a hitherto unrecognized chaperone. We show that polyP stabilizes proteins in vivo, diminishes the need for other chaperone systems to survive proteotoxic stress conditions, and protects a wide variety of proteins against stress-induced unfolding and aggregation. In vitro studies reveal that polyP has protein-like chaperone qualities, binds to unfolding proteins with high affinity in an ATP-independent manner, and supports their productive refolding once nonstress conditions are restored. Our results uncover a universally important function for polyP and suggest that these long chains of inorganic phosphate may have served as one of nature's first chaperones, a role that continues to the present day.
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Affiliation(s)
- Michael J Gray
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Wei-Yun Wholey
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI 48109, USA; Cellular and Molecular Biology Program, University of Michigan, Ann Arbor, MI 48109, USA
| | - Nico O Wagner
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Claudia M Cremers
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Antje Mueller-Schickert
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI 48109, USA; Howard Hughes Medical Institute, University of Michigan, Ann Arbor, MI 48109, USA
| | - Nathaniel T Hock
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Adam G Krieger
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Erica M Smith
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Robert A Bender
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI 48109, USA
| | - James C A Bardwell
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI 48109, USA; Cellular and Molecular Biology Program, University of Michigan, Ann Arbor, MI 48109, USA; Howard Hughes Medical Institute, University of Michigan, Ann Arbor, MI 48109, USA
| | - Ursula Jakob
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI 48109, USA; Cellular and Molecular Biology Program, University of Michigan, Ann Arbor, MI 48109, USA.
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190
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Moosekian SR, Jeong S, Ryser ET. Inactivation of sanitizer-injured Escherichia coli O157:H7 on baby spinach using X-ray irradiation. Food Control 2014. [DOI: 10.1016/j.foodcont.2013.08.024] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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191
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Niforou K, Cheimonidou C, Trougakos IP. Molecular chaperones and proteostasis regulation during redox imbalance. Redox Biol 2014; 2:323-32. [PMID: 24563850 PMCID: PMC3926111 DOI: 10.1016/j.redox.2014.01.017] [Citation(s) in RCA: 157] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2013] [Revised: 01/11/2014] [Accepted: 01/18/2014] [Indexed: 02/05/2023] Open
Abstract
Free radicals originate from both exogenous environmental sources and as by-products of the respiratory chain and cellular oxygen metabolism. Sustained accumulation of free radicals, beyond a physiological level, induces oxidative stress that is harmful for the cellular homeodynamics as it promotes the oxidative damage and stochastic modification of all cellular biomolecules including proteins. In relation to proteome stability and maintenance, the increased concentration of oxidants disrupts the functionality of cellular protein machines resulting eventually in proteotoxic stress and the deregulation of the proteostasis (homeostasis of the proteome) network (PN). PN curates the proteome in the various cellular compartments and the extracellular milieu by modulating protein synthesis and protein machines assembly, protein recycling and stress responses, as well as refolding or degradation of damaged proteins. Molecular chaperones are key players of the PN since they facilitate folding of nascent polypeptides, as well as holding, folding, and/or degradation of unfolded, misfolded, or non-native proteins. Therefore, the expression and the activity of the molecular chaperones are tightly regulated at both the transcriptional and post-translational level at organismal states of increased oxidative and, consequently, proteotoxic stress, including ageing and various age-related diseases (e.g. degenerative diseases and cancer). In the current review we present a synopsis of the various classes of intra- and extracellular chaperones, the effects of oxidants on cellular homeodynamics and diseases and the redox regulation of chaperones. Free radicals originate from various sources and at physiological concentrations are essential for the modulation of cell signalling pathways. Abnormally high levels of free radicals induce oxidative stress and damage all cellular biomolecules, including proteins. Molecular chaperones facilitate folding of nascent polypeptides, as well as holding, folding, and/or degradation of damaged proteins. The expression and the activity of chaperones during oxidative stress are regulated at both the transcriptional and post-translational level.
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Key Words
- AGEs, Advanced Glycation End Products
- ALS, Autophagy Lysosome System
- AP-1, Activator Protein-1
- CLU, apolipoprotein J/Clusterin
- Chaperones
- Diseases
- EPMs, Enzymatic Protein Modifications
- ER, Endoplasmic Reticulum
- ERAD, ER-Associated protein Degradation
- Free radicals
- GPx7, Glutathione Peroxidase 7
- GRP78, Glucose Regulated Protein of 78 kDa
- HSF1, Heat Shock transcription Factor-1
- HSP, Heat Shock Protein
- Hb, Haemoglobin
- Keap1, Kelch-like ECH-associated protein 1
- NADH, Nicotinamide Adenine Dinucleotide
- NEPMs, Non-Enzymatic Protein Modifications
- NOS, Nitric Oxide Synthase
- NOx, NAD(P)H Oxidase
- Nrf2, NF-E2-related factor 2
- Oxidative stress
- PDI, Protein Disulfide Isomerase
- PDR, Proteome Damage Responses
- PN, Proteostasis Network
- Proteome
- RNS, Reactive Nitrogen Species
- ROS, Reactive Oxygen Species
- Redox signalling
- UPR, Unfolded Protein Response
- UPS, Ubiquitin Proteasome System
- α(2)M, α(2)-Macroglobulin
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Affiliation(s)
- Katerina Niforou
- Department of Cell Biology and Biophysics, Faculty of Biology, University of Athens, Panepistimiopolis, Athens 15784, Greece
| | - Christina Cheimonidou
- Department of Cell Biology and Biophysics, Faculty of Biology, University of Athens, Panepistimiopolis, Athens 15784, Greece
| | - Ioannis P Trougakos
- Department of Cell Biology and Biophysics, Faculty of Biology, University of Athens, Panepistimiopolis, Athens 15784, Greece
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192
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Runde S, Molière N, Heinz A, Maisonneuve E, Janczikowski A, Elsholz AKW, Gerth U, Hecker M, Turgay K. The role of thiol oxidative stress response in heat-induced protein aggregate formation during thermotolerance in Bacillus subtilis. Mol Microbiol 2014; 91:1036-52. [PMID: 24417481 DOI: 10.1111/mmi.12521] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/11/2014] [Indexed: 11/30/2022]
Abstract
Using Bacillus subtilis as a model organism, we investigated thermotolerance development by analysing cell survival and in vivo protein aggregate formation in severely heat-shocked cells primed by a mild heat shock. We observed an increased survival during severe heat stress, accompanied by a strong reduction of heat-induced cellular protein aggregates in cells lacking the ClpXP protease. We could demonstrate that the transcription factor Spx, a regulatory substrate of ClpXP, is critical for the prevention of protein aggregate formation because its regulon encodes redox chaperones, such as thioredoxin, required for protection against thiol-specific oxidative stress. Consequently B. subtilis cells grown in the absence of oxygen were more protected against severe heat shock and much less protein aggregates were detected compared to aerobically grown cells. The presented results indicate that in B. subtilis Spx and its regulon plays not only an important role for oxidative but also for heat stress response and thermotolerance development. In addition, our experiments suggest that the protection of misfolded proteins from thiol oxidation during heat shock can be critical for the prevention of cellular protein aggregation in vivo.
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Affiliation(s)
- Stephanie Runde
- Institut für Biologie - Mikrobiologie, Freie Universität Berlin, D-14195, Berlin, Germany; Institut für Mikrobiologie, Leibniz Universität Hannover, D-30167, Hannover, Germany
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193
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Drazic A, Winter J. The physiological role of reversible methionine oxidation. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2014; 1844:1367-82. [PMID: 24418392 DOI: 10.1016/j.bbapap.2014.01.001] [Citation(s) in RCA: 139] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2013] [Revised: 12/17/2013] [Accepted: 01/02/2014] [Indexed: 01/04/2023]
Abstract
Sulfur-containing amino acids such as cysteine and methionine are particularly vulnerable to oxidation. Oxidation of cysteine and methionine in their free amino acid form renders them unavailable for metabolic processes while their oxidation in the protein-bound state is a common post-translational modification in all organisms and usually alters the function of the protein. In the majority of cases, oxidation causes inactivation of proteins. Yet, an increasing number of examples have been described where reversible cysteine oxidation is part of a sophisticated mechanism to control protein function based on the redox state of the protein. While for methionine the dogma is still that its oxidation inhibits protein function, reversible methionine oxidation is now being recognized as a powerful means of triggering protein activity. This mode of regulation involves oxidation of methionine to methionine sulfoxide leading to activated protein function, and inactivation is accomplished by reduction of methionine sulfoxide back to methionine catalyzed by methionine sulfoxide reductases. Given the similarity to thiol-based redox-regulation of protein function, methionine oxidation is now established as a novel mode of redox-regulation of protein function. This article is part of a Special Issue entitled: Thiol-Based Redox Processes.
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Affiliation(s)
- Adrian Drazic
- Center for Integrated Protein Science Munich (CiPS(M)) at the Department Chemie, Technische Universität München, 85747 Garching, Germany
| | - Jeannette Winter
- Center for Integrated Protein Science Munich (CiPS(M)) at the Department Chemie, Technische Universität München, 85747 Garching, Germany.
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194
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195
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Drazic A, Gebendorfer KM, Mak S, Steiner A, Krause M, Bepperling A, Winter J. Tetramers are the activation-competent species of the HOCl-specific transcription factor HypT. J Biol Chem 2013; 289:977-86. [PMID: 24275662 DOI: 10.1074/jbc.m113.521401] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Hypochlorous acid (HOCl) is an important component of the immune system and is produced by neutrophils to kill invading microorganisms. The transcription factor HypT is specifically activated by HOCl by methionine oxidation and protects Escherichia coli cells from the detrimental effects of HOCl. HypT forms dodecameric ring-like oligomers. Binding of HypT to DNA induces dissociation of the dodecamers into dimers and tetramers, thus forming the DNA-binding species. To dissect HypT dissociation, binding to DNA, and activation, we aimed to dissociate the dodecamers independently of DNA and to analyze HOCl-dependent activation in vitro. We found that HypT dodecamers dissociated into tetramers in the presence of l-arginine and NaCl, which was reversible upon dilution of the additive. Making use of the reversible dissociation, we generated mixed assemblies consisting of wild-type and mutant HypT subunits and determined that mutant subunits with reduced thermal stability were stabilized by wild-type HypT in the mixed assembly. HypT tetramers, as present at high NaCl concentrations, were stabilized against thermal unfolding and aggregation triggered by high HOCl concentrations. Importantly, in vitro activation by HOCl of HypT tetramers was completed within 1 min, whereas activation of dodecamers required 1 h for completion. Furthermore, activation of HypT tetramers required stoichiometric amounts of HOCl instead of an excess of HOCl, as observed for dodecamers. This supports the idea that small HypT oligomers are the activation-competent species, whereas the dodecamers are a storage form. Our study reveals the importance of the dynamic oligomeric state for HypT activation by HOCl.
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Affiliation(s)
- Adrian Drazic
- From the Center for Integrated Protein Science Munich (CiPS), Department Chemie, Technische Universität München, 85747 Garching, Germany
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196
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Uversky VN. Disorder in the lifetime of a protein. INTRINSICALLY DISORDERED PROTEINS 2013; 1:e26782. [PMID: 28516024 PMCID: PMC5424783 DOI: 10.4161/idp.26782] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/13/2013] [Revised: 10/09/2013] [Accepted: 10/10/2013] [Indexed: 12/21/2022]
Abstract
Intrinsic disorder is everywhere and is inevitable. The non-folding propensity is inherent for numerous natural polypeptide chains, and many functional proteins and protein regions are intrinsically disordered. Furthermore, at particular moments in their life, most notably during their synthesis and degradation, all ordered proteins are at least partially unfolded (disordered). Also, there is a widely spread phenomenon of conditional (functional or transient) disorder, where functions of many ordered proteins require local or even global unfolding of their unique structures. Finally, extrinsic disorder (i.e., intrinsic disorder in functional partners of ordered proteins) should be taken into account too. Therefore, even if a protein is completely devoid of intrinsically disordered regions in its mature form (which is a rather exceptional situation), it faces different forms of disorder (intrinsic, extrinsic, or induced disorder) at all the stages of its functional life, from birth to death. The goal of this article is to briefly introduce this concept of disorder in the lifetime of a protein.
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Affiliation(s)
- Vladimir N Uversky
- Department of Molecular Medicine and Byrd Alzheimer's Research Institute; Morsani College of Medicine; University of South Florida; Tampa, FL USA.,Institute for Biological Instrumentation; Russian Academy of Sciences; Moscow Region, Russia
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197
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Promiscuity as a functional trait: intrinsically disordered regions as central players of interactomes. Biochem J 2013; 454:361-9. [PMID: 23988124 DOI: 10.1042/bj20130545] [Citation(s) in RCA: 133] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Because of their pervasiveness in eukaryotic genomes and their unique properties, understanding the role that ID (intrinsically disordered) regions in proteins play in the interactome is essential for gaining a better understanding of the network. Especially critical in determining this role is their ability to bind more than one partner using the same region. Studies have revealed that proteins containing ID regions tend to take a central role in protein interaction networks; specifically, they act as hubs, interacting with multiple different partners across time and space, allowing for the co-ordination of many cellular activities. There appear to be three different modules within ID regions responsible for their functionally promiscuous behaviour: MoRFs (molecular recognition features), SLiMs (small linear motifs) and LCRs (low complexity regions). These regions allow for functionality such as engaging in the formation of dynamic heteromeric structures which can serve to increase local activity of an enzyme or store a collection of functionally related molecules for later use. However, the use of promiscuity does not come without a cost: a number of diseases that have been associated with ID-containing proteins seem to be caused by undesirable interactions occurring upon altered expression of the ID-containing protein.
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198
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Hao Z, Lou H, Zhu R, Zhu J, Zhang D, Zhao BS, Zeng S, Chen X, Chan J, He C, Chen PR. The multiple antibiotic resistance regulator MarR is a copper sensor in Escherichia coli. Nat Chem Biol 2013; 10:21-8. [PMID: 24185215 DOI: 10.1038/nchembio.1380] [Citation(s) in RCA: 112] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2013] [Accepted: 09/13/2013] [Indexed: 12/25/2022]
Abstract
The widely conserved multiple antibiotic resistance regulator (MarR) family of transcription factors modulates bacterial detoxification in response to diverse antibiotics, toxic chemicals or both. The natural inducer for Escherichia coli MarR, the prototypical transcription repressor within this family, remains unknown. Here we show that copper signaling potentiates MarR derepression in E. coli. Copper(II) oxidizes a cysteine residue (Cys80) on MarR to generate disulfide bonds between two MarR dimers, thereby inducing tetramer formation and the dissociation of MarR from its cognate promoter DNA. We further discovered that salicylate, a putative MarR inducer, and the clinically important bactericidal antibiotics norfloxacin and ampicillin all stimulate intracellular copper elevation, most likely through oxidative impairment of copper-dependent envelope proteins, including NADH dehydrogenase-2. This membrane-associated copper oxidation and liberation process derepresses MarR, causing increased bacterial antibiotic resistance. Our study reveals that this bacterial transcription regulator senses copper(II) as a natural signal to cope with stress caused by antibiotics or the environment.
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Affiliation(s)
- Ziyang Hao
- 1] Synthetic and Functional Biomolecules Center, Beijing National Laboratory for Molecular Sciences, Department of Chemical Biology, College of Chemistry and Molecular Engineering, Peking University, Beijing, China. [2]
| | - Hubing Lou
- 1] Synthetic and Functional Biomolecules Center, Beijing National Laboratory for Molecular Sciences, Department of Chemical Biology, College of Chemistry and Molecular Engineering, Peking University, Beijing, China. [2] [3]
| | - Rongfeng Zhu
- Peking-Tsinghua Center for Life Sciences, Beijing, China
| | - Jiuhe Zhu
- College of Biological Sciences, China Agricultural University, Beijing, China
| | - Dianmu Zhang
- Synthetic and Functional Biomolecules Center, Beijing National Laboratory for Molecular Sciences, Department of Chemical Biology, College of Chemistry and Molecular Engineering, Peking University, Beijing, China
| | - Boxuan Simen Zhao
- 1] Synthetic and Functional Biomolecules Center, Beijing National Laboratory for Molecular Sciences, Department of Chemical Biology, College of Chemistry and Molecular Engineering, Peking University, Beijing, China. [2] Department of Chemistry and Institute for Biophysical Dynamics, University of Chicago, Chicago, Illinois, USA
| | - Shizhe Zeng
- International Curriculum Center, High School affiliated to Renmin University, Beijing, China
| | - Xing Chen
- Synthetic and Functional Biomolecules Center, Beijing National Laboratory for Molecular Sciences, Department of Chemical Biology, College of Chemistry and Molecular Engineering, Peking University, Beijing, China
| | - Jefferson Chan
- Department of Chemistry, University of California-Berkeley, Berkeley, California, USA
| | - Chuan He
- 1] Synthetic and Functional Biomolecules Center, Beijing National Laboratory for Molecular Sciences, Department of Chemical Biology, College of Chemistry and Molecular Engineering, Peking University, Beijing, China. [2] Department of Chemistry and Institute for Biophysical Dynamics, University of Chicago, Chicago, Illinois, USA. [3] Shanghai Universities E-Institute for Chemical Biology, Shanghai, China
| | - Peng R Chen
- 1] Synthetic and Functional Biomolecules Center, Beijing National Laboratory for Molecular Sciences, Department of Chemical Biology, College of Chemistry and Molecular Engineering, Peking University, Beijing, China. [2] Peking-Tsinghua Center for Life Sciences, Beijing, China. [3] Shanghai Universities E-Institute for Chemical Biology, Shanghai, China
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199
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Analysis of Arabidopsis thioredoxin-h isotypes identifies discrete domains that confer specific structural and functional properties. Biochem J 2013; 456:13-24. [DOI: 10.1042/bj20130618] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
In this study, we identified specific domains and amino acids responsible for the structural and functional properties of AtTrx-hs (Arabidopsis h-type thioredoxins). Specific domains and amino acids for the chaperone function of AtTrx-hs played a critical role in heat-shock-resistance in vivo.
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200
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Role of cysteines in the stability and DNA-binding activity of the hypochlorite-specific transcription factor HypT. PLoS One 2013; 8:e75683. [PMID: 24116067 PMCID: PMC3792123 DOI: 10.1371/journal.pone.0075683] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2013] [Accepted: 08/20/2013] [Indexed: 11/19/2022] Open
Abstract
Reactive oxygen species are important components of the immune response. Hypochlorite (HOCl) is produced by neutrophils to kill invading microorganisms. The bactericidal activity of HOCl is due to proteome-wide unfolding and oxidation of proteins at cysteine and methionine residues. Escherichia coli cells are protected from HOCl-killing by the previously identified dodecameric transcription factor HypT (YjiE). Here, we aimed to unravel whether HOCl activates HypT directly or via a reaction product of HOCl with a cellular component. Bacterial viability assays and analysis of target gene regulation indicate that HypT is highly specific to activation by HOCl and that no reaction products of HOCl such as monochloramine, hydroxyl radicals, or methionine sulfoxide activate HypT in vivo. Surprisingly, purified HypT lost its DNA-binding activity upon incubation with HOCl or reaction products that oxidize HypT to form a disulfide-linked dimer, and regained DNA-binding activity upon reduction. Thus, we postulate that the cysteines in HypT contribute to control the DNA-binding activity of HypT in vitro. HypT contains five cysteine residues; a HypT mutant with all cysteines substituted by serine is aggregation-prone and forms tetramers in addition to the typical dodecamers. Using single and multiple cysteine-to-serine mutants, we identified Cys150 to be required for stability and Cys4 being important for oligomerization of HypT to dodecamers. Further, oxidation of Cys4 is responsible for the loss of DNA-binding of HypT upon oxidation in vitro. It appears that Cys4 oxidation upon conditions that are insufficient to stimulate the DNA-binding activity of HypT prevents unproductive interactions of HypT with DNA. Thus, Cys4 oxidation may be a check point in the activation process of HypT.
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