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Singh D, Rahi A, Kumari R, Gupta V, Gautam G, Aggarwal S, Rehan M, Bhatnagar R. Computational and mutational analysis of TatD DNase of Bacillus anthracis. J Cell Biochem 2019; 120:11318-11330. [PMID: 30719750 DOI: 10.1002/jcb.28408] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2018] [Revised: 12/12/2018] [Accepted: 12/14/2018] [Indexed: 01/24/2023]
Abstract
The role of TatD DNases as DNA repair enzymes or cell death (apoptotic) nucleases is well established in prokaryotes as well as eukaryotes. The current study aims to characterize the TatD nuclease from Bacillus anthracis (Ba TatD) and to explore its key histidine catalytic residues. Ba TatD was found to be a metal-dependent, nonspecific endonuclease which could efficiently cleave double-stranded DNA substrates. Moreover, Ba TatD nuclease was observed to be thermostable up to 55°C and act in a wide pH range indicating its industrial applicability. Diethyl pyrocarbonate-based histidine-selective alkylation of the Ba TatD resulted in a loss of its nuclease activity suggesting a crucial role of the histidine residues in its activity. The key residues of Ba TatD were predicted using sequence analysis and structure-based approaches, and then the predicted residues were further tested by mutational analysis. Upon mutational analysis, H128 and H153 have been found to be crucial for Ba TatD activity, though H153 seems to bear an important but a dispensable role for the Ba TatD nuclease. Ba TatD had a uniform expression in the cytosol of B. anthracis, which indicates a significant role of the protein in the pathogen's life cycle. This is the first study to identify and characterize the TatD DNase from B. anthracis and will be helpful in gaining more insights on the role of TatD proteins in Gram-positive bacteria where it remains unexplored.
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Affiliation(s)
- Damini Singh
- Laboratory of Molecular Biology and Genetic Engineering, School of Biotechnology, Jawaharlal Nehru University, New Delhi, India
| | - Amit Rahi
- Laboratory of Molecular Biology and Genetic Engineering, School of Biotechnology, Jawaharlal Nehru University, New Delhi, India
| | - Romika Kumari
- Finland Institute for Molecular Medicine (FIMM), Helsinki, Finland
| | - Vatika Gupta
- Laboratory of Molecular Biology and Genetic Engineering, School of Biotechnology, Jawaharlal Nehru University, New Delhi, India
| | - Gunjan Gautam
- School of Life Sciences, Jawaharlal Nehru University, New Delhi, India
| | - Somya Aggarwal
- Laboratory of Molecular Biology and Genetic Engineering, School of Biotechnology, Jawaharlal Nehru University, New Delhi, India
| | - Mohd Rehan
- King Fahd Medical Research Center, King Abdulaziz University, Jeddah, Kingdom of Saudi Arabia
| | - Rakesh Bhatnagar
- Laboratory of Molecular Biology and Genetic Engineering, School of Biotechnology, Jawaharlal Nehru University, New Delhi, India
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Smith MR, Vayalil PK, Zhou F, Benavides GA, Beggs RR, Golzarian H, Nijampatnam B, Oliver PG, Smith RAJ, Murphy MP, Velu SE, Landar A. Mitochondrial thiol modification by a targeted electrophile inhibits metabolism in breast adenocarcinoma cells by inhibiting enzyme activity and protein levels. Redox Biol 2016; 8:136-48. [PMID: 26774751 PMCID: PMC4732023 DOI: 10.1016/j.redox.2016.01.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2015] [Revised: 01/07/2016] [Accepted: 01/07/2016] [Indexed: 11/30/2022] Open
Abstract
Many cancer cells follow an aberrant metabolic program to maintain energy for rapid cell proliferation. Metabolic reprogramming often involves the upregulation of glutaminolysis to generate reducing equivalents for the electron transport chain and amino acids for protein synthesis. Critical enzymes involved in metabolism possess a reactive thiolate group, which can be modified by certain oxidants. In the current study, we show that modification of mitochondrial protein thiols by a model compound, iodobutyl triphenylphosphonium (IBTP), decreased mitochondrial metabolism and ATP in MDA-MB 231 (MB231) breast adenocarcinoma cells up to 6 days after an initial 24 h treatment. Mitochondrial thiol modification also depressed oxygen consumption rates (OCR) in a dose-dependent manner to a greater extent than a non-thiol modifying analog, suggesting that thiol reactivity is an important factor in the inhibition of cancer cell metabolism. In non-tumorigenic MCF-10A cells, IBTP also decreased OCR; however the extracellular acidification rate was significantly increased at all but the highest concentration (10 µM) of IBTP indicating that thiol modification can have significantly different effects on bioenergetics in tumorigenic versus non-tumorigenic cells. ATP and other adenonucleotide levels were also decreased by thiol modification up to 6 days post-treatment, indicating a decreased overall energetic state in MB231 cells. Cellular proliferation of MB231 cells was also inhibited up to 6 days post-treatment with little change to cell viability. Targeted metabolomic analyses revealed that thiol modification caused depletion of both Krebs cycle and glutaminolysis intermediates. Further experiments revealed that the activity of the Krebs cycle enzyme, aconitase, was attenuated in response to thiol modification. Additionally, the inhibition of glutaminolysis corresponded to decreased glutaminase C (GAC) protein levels, although other protein levels were unaffected. This study demonstrates for the first time that mitochondrial thiol modification inhibits metabolism via inhibition of both aconitase and GAC in a breast cancer cell model. IBTP dependent thiol modification decreases bioenergetics in MB231 and MCF-10A cells. IBTP treatment decreases ATP and other adenonucleotides after 1 to 6 days. IBTP treatment does not result in overt cellular toxicity. IBTP treatment decreases levels of bioenergetically-linked metabolites. IBTP treatment decreases aconitase activity and glutaminase protein levels.
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Affiliation(s)
- M Ryan Smith
- Department of Pathology, University of Alabama at Birmingham, AL, USA; Center for Free Radical Biology, University of Alabama at Birmingham, AL, USA
| | - Praveen K Vayalil
- Department of Pathology, University of Alabama at Birmingham, AL, USA; Center for Free Radical Biology, University of Alabama at Birmingham, AL, USA
| | - Fen Zhou
- Department of Pathology, University of Alabama at Birmingham, AL, USA; Center for Free Radical Biology, University of Alabama at Birmingham, AL, USA
| | - Gloria A Benavides
- Department of Pathology, University of Alabama at Birmingham, AL, USA; Center for Free Radical Biology, University of Alabama at Birmingham, AL, USA
| | - Reena R Beggs
- Department of Pathology, University of Alabama at Birmingham, AL, USA
| | - Hafez Golzarian
- Department of Chemistry, University of Alabama at Birmingham, AL, USA
| | | | - Patsy G Oliver
- Department of Radiation Oncology, University of Alabama at Birmingham, AL, USA
| | - Robin A J Smith
- Department of Chemistry, University of Otago, Dunedin, New Zealand
| | | | - Sadanandan E Velu
- Department of Chemistry, University of Alabama at Birmingham, AL, USA
| | - Aimee Landar
- Department of Pathology, University of Alabama at Birmingham, AL, USA; Center for Free Radical Biology, University of Alabama at Birmingham, AL, USA.
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Abstract
Mammalian glutaminases catalyze the stoichiometric conversion of L-glutamine to L-glutamate and ammonium ions. In brain, glutaminase is considered the prevailing pathway for synthesis of the neurotransmitter pool of glutamate. Besides neurotransmission, the products of glutaminase reaction also fulfill crucial roles in energy and metabolic homeostasis in mammalian brain. In the last years, new functional roles for brain glutaminases are being uncovered by using functional genomic and proteomic approaches. Glutaminases may act as multifunctional proteins able to perform different tasks: the discovery of multiple transcript variants in neurons and glial cells, novel extramitochondrial localizations, and isoform-specific proteininteracting partners strongly support possible moonlighting functions for these proteins. In this chapter, we present a critical account of essential works on brain glutaminase 80 years after its discovery. We will highlight the impact of recent findings and thoughts in the context of the glutamate/glutamine brain homeostasis.
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de la Rosa V, Campos-Sandoval JA, Martín-Rufián M, Cardona C, Matés JM, Segura JA, Alonso FJ, Márquez J. A novel glutaminase isoform in mammalian tissues. Neurochem Int 2009; 55:76-84. [PMID: 19428810 DOI: 10.1016/j.neuint.2009.02.021] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2008] [Revised: 02/24/2009] [Accepted: 02/27/2009] [Indexed: 12/18/2022]
Abstract
The synthesis of neurotransmitter glutamate in brain is mainly carried out by glutaminase enzymes. This synthesis must be exquisitely regulated because of its harmful potential giving rise to excitotoxic damage. It is noteworthy that two glutaminase isozymes coded by different genes are expressed in the brain of mammals. The need for two genes and two isozymes to support the single process of glutamate synthesis is unexplained, and identifying the role of each glutaminase is an important factor in understanding glutamate-mediated neurotransmission. Multiple transcripts for glutaminase genes and simultaneous expression of glutaminase isoforms have been reported in mammalian tissues and cells. The recent discovery of protein interacting partners widens the possibilities of regulatory mechanisms controlling these biosynthetic enzymes. The expression of distinct isozymes and binding partners may represent the biochemical and molecular basis to achieve fine-tuning control of glutamate synthesis in different cell types or developmental states. In this review, we will briefly summarize recent works on glutaminase proteins in mammals, with particular emphasis on brain studies. We present convergent evidence supporting the existence of a novel glutaminase isozyme in mammalian tissues.
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Affiliation(s)
- Vanessa de la Rosa
- Departamento de Biología Molecular y Bioquímica, Facultad de Ciencias, Laboratorio de Química de Proteínas, Universidad de Málaga, Málaga, Spain
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Campos-Sandoval JA, López de la Oliva AR, Lobo C, Segura JA, Matés JM, Alonso FJ, Márquez J. Expression of functional human glutaminase in baculovirus system: Affinity purification, kinetic and molecular characterization. Int J Biochem Cell Biol 2007; 39:765-73. [PMID: 17267261 DOI: 10.1016/j.biocel.2006.12.002] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2006] [Revised: 12/05/2006] [Accepted: 12/06/2006] [Indexed: 11/29/2022]
Abstract
Glutaminase catalyzes the hydrolysis of glutamine yielding stoichiometric amounts of glutamate plus ammonium ions. In mammals, there are two different genes encoding for glutaminase, known as liver (L) and kidney (K) types. The human L-type isoform expressed in baculovirus yielded functional recombinant enzyme in Sf9 insect cells. A novel affinity chromatography method, based on its specific interaction with a PDZ protein, was developed for purification. Kinetic constants were determined for the purified human isozyme, which showed an allosteric behaviour for glutamine, with a Hill index of 2.7 and S(0.5) values of 32 and 64 mM for high and low P(i) concentrations, respectively. Whereas the protein showed a low P(i) dependence typical for L-type glutaminases, the enzyme was unexpectedly inhibited by glutamate, a kinetic characteristic exclusive of K-type isozymes, and was slightly activated by ammonia, unlike the classical liver enzymes which show an absolute dependence on ammonia. Subcellular fractionation demonstrates that recombinant human glutaminase was targeted to both mitochondria and nucleus, and in both locations the protein was catalytically active. This is the first report of the expression of a functional L-type mammalian glutaminase enzyme. The study also provides a simple and efficient method for affinity purification of the recombinant enzyme. Moreover, the data imply that this human enzyme may represent a new isoform different from classical kidney and liver isozymes.
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Affiliation(s)
- José A Campos-Sandoval
- Departamento de Biología Molecular y Bioquímica, Laboratorio de Química de Proteínas, Facultad de Ciencias, Universidad de Málaga, 29071 Málaga, Spain
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Carraro S, Doherty J, Zaman K, Gainov I, Turner R, Vaughan J, Hunt JF, Márquez J, Gaston B. S-nitrosothiols regulate cell-surface pH buffering by airway epithelial cells during the human immune response to rhinovirus. Am J Physiol Lung Cell Mol Physiol 2006; 290:L827-32. [PMID: 16603595 DOI: 10.1152/ajplung.00406.2005] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Human rhinovirus infection is a common trigger for asthma exacerbations. Asthma exacerbations and rhinovirus infections are both associated with markedly decreased pH and ammonium levels in exhaled breath condensates. This observation is thought to be related, in part, to decreased activity of airway epithelial glutaminase. We studied whether direct rhinovirus infection and/or the host immune response to the infection decreased airway epithelial cell surface pH in vitro. Interferon-gamma and tumor necrosis factor-alpha, but not direct rhinovirus infection, decreased pH, an effect partly associated with decreased ammonium concentrations. This effect was 1) prevented by nitric oxide synthase inhibition; 2) independent of cyclic GMP; 3) associated with an increase in endogenous airway epithelial cell S-nitrosothiol concentration; 4) mimicked by the exogenous S-nitrosothiol, S-nitroso-N-acetyl cysteine; and 5) independent of glutaminase expression and activity. We then confirmed that decreased epithelial pH inhibits human rhinovirus replication in airway epithelial cells. These data suggest that a nitric oxide synthase-dependent host response to viral infection mediated by S-nitrosothiols, rather than direct infection itself, plays a role in decreased airway surface pH during human rhinovirus infection. This host immune response may serve to protect the lower airways from direct infection in the normal host. In patients with asthma, however, this fall in pH could be associated with the increased mucus production, augmented inflammatory cell degranulation, bronchoconstriction, and cough characteristic of an asthma exacerbation.
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Affiliation(s)
- Silvia Carraro
- Pediatric Respiratory Medicine, University of Virginia Health System, Box 800386, Charlottesville, VA 22908, USA
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Campos JA, Aledo JC, Segura JA, Alonso FJ, Gómez-Fabre PM, Núñez de Castro I, Márquez J. Expression of recombinant human L-glutaminase in Escherichia coli: polyclonal antibodies production and immunological analysis of mouse tissues. BIOCHIMICA ET BIOPHYSICA ACTA 2003; 1648:17-23. [PMID: 12758143 DOI: 10.1016/s1570-9639(03)00026-8] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The first complete sequence of human L-glutaminase was deduced from breast cancer glutaminase cDNA cloned in our laboratory. This cDNA clone has now been engineered to synthesize both precursor and mature forms of the protein in Escherichia coli. Among several different plasmid constructions, the expression system based on phage T7 promoter (vector pET-3c) was found to be the most efficient for glutaminase overproduction. Upon induction, precursor glutaminase accounts for about 25% of total E. coli protein, whereas a lower amount (12%) was achieved for the putative mature protein. The optimal length of the translational spacer on the ribosome binding site was shown to be eight nucleotides. However, using this length of spacer, we were unable to obtain expression in the pQE vector, tagged with a 6x His sequence at the NH(2)-terminus, stressing the importance of the 5'-coding sequence in the expression efficiency. Although the precursor and mature recombinant forms of glutaminase were devoid of catalytic activity, the purified protein allowed us to obtain highly specific polyclonal antibodies, as shown by immunoblot analysis of mouse tissues. Furthermore, the antibodies were able to immunoprecipitate the in vitro translated enzyme using a reticulocyte lysate system; these antibodies might be a valuable tool for studies on L-glutaminase expression in mammalian tissues.
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Affiliation(s)
- José A Campos
- Laboratorio de Qui;mica de Proteínas, Departamento de Biología Molecular y Bioquímica, Facultad de Ciencias, Universidad de Málaga, Spain
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Abstract
Glutamine is the most abundant free amino acid in the human body; it is essential for the growth of normal and neoplastic cells and for the culture of many cell types. Cancer has been described as a nitrogen trap. The presence of a tumor produces great changes in host glutamine metabolism in such a way that host nitrogen metabolism is accommodated to the tumor-enhanced requirements of glutamine. To be used, glutamine must be transported into tumor mitochondria. Thus, an overview of the role of glutamine in cancer requires not only a discussion of host and tumor glutamine metabolism, but also its circulation and transport. Because glutamine depletion has adverse effects for the host, the effect of glutamine supplementation in the tumor-bearing state should also be studied. This communication reviews the state of knowledge of glutamine and cancer, including potential therapeutic implications.
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Affiliation(s)
- M A Medina
- Department of Molecular Biology and Biochemistry, Faculty of Sciences, University of Málaga, Málaga, Spain
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