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Pathirage R, Favrot L, Petit C, Yamsek M, Singh S, Mallareddy JR, Rana S, Natarajan A, Ronning DR. Mycobacterium tuberculosis CitA activity is modulated by cysteine oxidation and pyruvate binding. RSC Med Chem 2023; 14:921-933. [PMID: 37252106 PMCID: PMC10211323 DOI: 10.1039/d3md00058c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2023] [Accepted: 04/05/2023] [Indexed: 11/12/2023] Open
Abstract
As an adaptation for survival during infection, Mycobacterium tuberculosis becomes dormant, reducing its metabolism and growth. Two types of citrate synthases have been identified in Mycobacterium tuberculosis, GltA2 and CitA. Previous work shows that overexpression of CitA, the secondary citrate synthase, stimulates the growth of Mycobacterium tuberculosis under hypoxic conditions without showing accumulation of triacylglycerols and makes mycobacteria more sensitive to antibiotics, suggesting that CitA may play a role as a metabolic switch during infection and may be an interesting TB drug target. To assess the druggability and possible mechanisms of targeting CitA with small-molecule compounds, the CitA crystal structure was solved to 2.1 Å by X-ray crystallography. The solved structure shows that CitA lacks an NADH binding site that would afford allosteric regulation, which is atypical of most citrate synthases. However, a pyruvate molecule is observed within the analogous domain, suggesting pyruvate may instead be the allosteric regulator for CitA. The R149 and R153 residues forming the charged portion of the pyruvate binding pocket were mutated to glutamate and methionine, respectively, to assess the effect of mutations on activity. Protein thermal shift assay shows thermal stabilization of CitA in the presence of pyruvate compared to the two CitA variants designed to decrease pyruvate affinity. Solved crystal structures of both variants show no significant structural changes. However, the catalytic efficiency of the R153M variant increases by 2.6-fold. Additionally, we show that covalent modification of C143 of CitA by Ebselen completely arrests enzyme activity. Similar inhibition is observed using two spirocyclic Michael acceptor containing compounds, which inhibit CitA with ICapp50 values of 6.6 and 10.9 μM. A crystal structure of CitA modified by Ebselen was solved, but significant structural changes were lacking. Considering that covalent modification of C143 inactivates CitA and the proximity of C143 to the pyruvate binding site, this suggests that structural and/or chemical changes in this sub-domain are responsible for regulating CitA enzymatic activity.
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Affiliation(s)
- Rasangi Pathirage
- Department of Pharmaceutical Sciences, University of Nebraska Medical Center Omaha NE 68198 USA
| | - Lorenza Favrot
- Department of Chemistry and Biochemistry, University of Toledo Toledo OH 43606 USA
| | - Cecile Petit
- Department of Chemistry and Biochemistry, University of Toledo Toledo OH 43606 USA
| | - Melvin Yamsek
- Department of Chemistry and Biochemistry, University of Toledo Toledo OH 43606 USA
| | - Sarbjit Singh
- Eppley Institute for Cancer Research, University of Nebraska Medical Center Omaha NE 68198 USA
| | | | - Sandeep Rana
- Eppley Institute for Cancer Research, University of Nebraska Medical Center Omaha NE 68198 USA
| | - Amarnath Natarajan
- Department of Pharmaceutical Sciences, University of Nebraska Medical Center Omaha NE 68198 USA
- Eppley Institute for Cancer Research, University of Nebraska Medical Center Omaha NE 68198 USA
- Department of Genetics Cell Biology and Anatomy, University of Nebraska Medical Center Omaha NE 68198 USA
- Fred & Pamela Buffett Cancer Center, University of Nebraska Medical Center Omaha NE USA
| | - Donald R Ronning
- Department of Pharmaceutical Sciences, University of Nebraska Medical Center Omaha NE 68198 USA
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2
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Bedaquiline reprograms central metabolism to reveal glycolytic vulnerability in Mycobacterium tuberculosis. Nat Commun 2020; 11:6092. [PMID: 33257709 PMCID: PMC7705017 DOI: 10.1038/s41467-020-19959-4] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2020] [Accepted: 11/04/2020] [Indexed: 02/06/2023] Open
Abstract
The approval of bedaquiline (BDQ) for the treatment of tuberculosis has generated substantial interest in inhibiting energy metabolism as a therapeutic paradigm. However, it is not known precisely how BDQ triggers cell death in Mycobacterium tuberculosis (Mtb). Using 13C isotopomer analysis, we show that BDQ-treated Mtb redirects central carbon metabolism to induce a metabolically vulnerable state susceptible to genetic disruption of glycolysis and gluconeogenesis. Metabolic flux profiles indicate that BDQ-treated Mtb is dependent on glycolysis for ATP production, operates a bifurcated TCA cycle by increasing flux through the glyoxylate shunt, and requires enzymes of the anaplerotic node and methylcitrate cycle. Targeting oxidative phosphorylation (OXPHOS) with BDQ and simultaneously inhibiting substrate level phosphorylation via genetic disruption of glycolysis leads to rapid sterilization. Our findings provide insight into the metabolic mechanism of BDQ-induced cell death and establish a paradigm for the development of combination therapies that target OXPHOS and glycolysis.
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3
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Abstract
SIGNIFICANCE Iron-sulfur cluster proteins carry out multiple functions, including as regulators of gene transcription/translation in response to environmental stimuli. In all known cases, the cluster acts as the sensory module, where the inherent reactivity/fragility of iron-sulfur clusters with small/redox-active molecules is exploited to effect conformational changes that modulate binding to DNA regulatory sequences. This promotes an often substantial reprogramming of the cellular proteome that enables the organism or cell to adapt to, or counteract, its changing circumstances. Recent Advances: Significant progress has been made recently in the structural and mechanistic characterization of iron-sulfur cluster regulators and, in particular, the O2 and NO sensor FNR, the NO sensor NsrR, and WhiB-like proteins of Actinobacteria. These are the main focus of this review. CRITICAL ISSUES Striking examples of how the local environment controls the cluster sensitivity and reactivity are now emerging, but the basis for this is not yet fully understood for any regulatory family. FUTURE DIRECTIONS Characterization of iron-sulfur cluster regulators has long been hampered by a lack of high-resolution structural data. Although this still presents a major future challenge, recent advances now provide a firm foundation for detailed understanding of how a signal is transduced to effect gene regulation. This requires the identification of often unstable intermediate species, which are difficult to detect and may be hard to distinguish using traditional techniques. Novel approaches will be required to solve these problems.
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Affiliation(s)
- Jason C Crack
- Centre for Molecular and Structural Biochemistry, School of Chemistry, University of East Anglia , Norwich Research Park, Norwich, United Kingdom
| | - Nick E Le Brun
- Centre for Molecular and Structural Biochemistry, School of Chemistry, University of East Anglia , Norwich Research Park, Norwich, United Kingdom
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4
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Ferraris DM, Miggiano R, Rossi F, Rizzi M. Mycobacterium tuberculosis Molecular Determinants of Infection, Survival Strategies, and Vulnerable Targets. Pathogens 2018; 7:E17. [PMID: 29389854 PMCID: PMC5874743 DOI: 10.3390/pathogens7010017] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2017] [Revised: 01/26/2018] [Accepted: 01/28/2018] [Indexed: 12/13/2022] Open
Abstract
Mycobacterium tuberculosis is the causative agent of tuberculosis, an ancient disease which, still today, represents a major threat for the world population. Despite the advances in medicine and the development of effective antitubercular drugs, the cure of tuberculosis involves prolonged therapies which complicate the compliance and monitoring of drug administration and treatment. Moreover, the only available antitubercular vaccine fails to provide an effective shield against adult lung tuberculosis, which is the most prevalent form. Hence, there is a pressing need for effective antitubercular drugs and vaccines. This review highlights recent advances in the study of selected M. tuberculosis key molecular determinants of infection and vulnerable targets whose structures could be exploited for the development of new antitubercular agents.
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Affiliation(s)
- Davide M Ferraris
- Department of Pharmaceutical Sciences, Università del Piemonte Orientale "A. Avogadro", Largo Donegani 2, 28100 Novara, Italy.
| | - Riccardo Miggiano
- Department of Pharmaceutical Sciences, Università del Piemonte Orientale "A. Avogadro", Largo Donegani 2, 28100 Novara, Italy.
| | - Franca Rossi
- Department of Pharmaceutical Sciences, Università del Piemonte Orientale "A. Avogadro", Largo Donegani 2, 28100 Novara, Italy.
| | - Menico Rizzi
- Department of Pharmaceutical Sciences, Università del Piemonte Orientale "A. Avogadro", Largo Donegani 2, 28100 Novara, Italy.
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5
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Abstract
SIGNIFICANCE Iron-sulfur cluster proteins carry out a wide range of functions, including as regulators of gene transcription/translation in response to environmental stimuli. In all known cases, the cluster acts as the sensory module, where the inherent reactivity/fragility of iron-sulfur clusters towards small/redox active molecules is exploited to effect conformational changes that modulate binding to DNA regulatory sequences. This promotes an often substantial re-programming of the cellular proteome that enables the organism or cell to adapt to, or counteract, its changing circumstances. Recent Advances. Significant progress has been made recently in the structural and mechanistic characterization of iron-sulfur cluster regulators and, in particular, the O2 and NO sensor FNR, the NO sensor NsrR, and WhiB-like proteins of Actinobacteria. These are the main focus of this review. CRITICAL ISSUES Striking examples of how the local environment controls the cluster sensitivity and reactivity are now emerging, but the basis for this is not yet fully understood for any regulatory family. FUTURE DIRECTIONS Characterization of iron-sulfur cluster regulators has long been hampered by a lack of high resolution structural data. Though this still presents a major future challenge, recent advances now provide a firm foundation for detailed understanding of how a signal is transduced to effect gene regulation. This requires the identification of often unstable intermediate species, which are difficult to detect and may be hard to distinguish using traditional techniques. Novel approaches will be required to solve these problems.
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Affiliation(s)
- Jason C Crack
- School of Chemistry , University of East Anglia , Norwich, United Kingdom of Great Britain and Northern Ireland , NR4 7TJ ;
| | - Nick E Le Brun
- University of East Anglia, School of Chemistry , University plain , Norwich, United Kingdom of Great Britain and Northern Ireland , NR4 7TJ ;
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6
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Mass spectrometric identification of intermediates in the O 2-driven [4Fe-4S] to [2Fe-2S] cluster conversion in FNR. Proc Natl Acad Sci U S A 2017; 114:E3215-E3223. [PMID: 28373574 DOI: 10.1073/pnas.1620987114] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
The iron-sulfur cluster containing protein Fumarate and Nitrate Reduction (FNR) is the master regulator for the switch between anaerobic and aerobic respiration in Escherichia coli and many other bacteria. The [4Fe-4S] cluster functions as the sensory module, undergoing reaction with O2 that leads to conversion to a [2Fe-2S] form with loss of high-affinity DNA binding. Here, we report studies of the FNR cluster conversion reaction using time-resolved electrospray ionization mass spectrometry. The data provide insight into the reaction, permitting the detection of cluster conversion intermediates and products, including a [3Fe-3S] cluster and persulfide-coordinated [2Fe-2S] clusters [[2Fe-2S](S) n , where n = 1 or 2]. Analysis of kinetic data revealed a branched mechanism in which cluster sulfide oxidation occurs in parallel with cluster conversion and not as a subsequent, secondary reaction to generate [2Fe-2S](S) n species. This methodology shows great potential for broad application to studies of protein cofactor-small molecule interactions.
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7
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Metabolic plasticity of central carbon metabolism protects mycobacteria. Proc Natl Acad Sci U S A 2015; 112:13135-6. [PMID: 26483480 DOI: 10.1073/pnas.1518171112] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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8
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Ferraris DM, Spallek R, Oehlmann W, Singh M, Rizzi M. Structures of citrate synthase and malate dehydrogenase of M
ycobacterium tuberculosis. Proteins 2015; 83:389-94. [DOI: 10.1002/prot.24743] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2014] [Revised: 11/20/2014] [Accepted: 11/26/2014] [Indexed: 11/11/2022]
Affiliation(s)
- Davide M. Ferraris
- Department of Pharmaceutical Sciences; Università del Piemonte Orientale “A. Avogadro”, Largo Donegani 2; 28100 Novara Italy
| | - Ralf Spallek
- Lionex Diagnostics and Therapeutic GmbH; D-38126 Braunschweig Germany
| | - Wulf Oehlmann
- Lionex Diagnostics and Therapeutic GmbH; D-38126 Braunschweig Germany
| | - Mahavir Singh
- Lionex Diagnostics and Therapeutic GmbH; D-38126 Braunschweig Germany
| | - Menico Rizzi
- Department of Pharmaceutical Sciences; Università del Piemonte Orientale “A. Avogadro”, Largo Donegani 2; 28100 Novara Italy
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9
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Influence of association state and DNA binding on the O₂-reactivity of [4Fe-4S] fumarate and nitrate reduction (FNR) regulator. Biochem J 2014; 463:83-92. [PMID: 25019503 PMCID: PMC4214427 DOI: 10.1042/bj20140169] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The fumarate and nitrate reduction (FNR) regulator is the master switch for the transition between anaerobic and aerobic respiration in Escherichia coli. Reaction of dimeric [4Fe-4S] FNR with O2 results in conversion of the cluster into a [2Fe-2S] form, via a [3Fe-4S] intermediate, leading to the loss of DNA binding through dissociation of the dimer into monomers. In the present paper, we report studies of two previously identified variants of FNR, D154A and I151A, in which the form of the cluster is decoupled from the association state. In vivo studies of permanently dimeric D154A FNR show that DNA binding does not affect the rate of cluster incorporation into the apoprotein or the rate of O2-mediated cluster loss. In vitro studies show that O2-mediated cluster conversion for D154A and the permanent monomer I151A FNR is the same as in wild-type FNR, but with altered kinetics. Decoupling leads to an increase in the rate of the [3Fe-4S]1+ into [2Fe-2S]2+ conversion step, consistent with the suggestion that this step drives association state changes in the wild-type protein. We have also shown that DNA-bound FNR reacts more rapidly with O2 than FNR free in solution, implying that transcriptionally active FNR is the preferred target for reaction with O2.
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10
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Cai W, Wannemuehler Y, Dell'Anna G, Nicholson B, Barbieri NL, Kariyawasam S, Feng Y, Logue CM, Nolan LK, Li G. A novel two-component signaling system facilitates uropathogenic Escherichia coli's ability to exploit abundant host metabolites. PLoS Pathog 2013; 9:e1003428. [PMID: 23825943 PMCID: PMC3694859 DOI: 10.1371/journal.ppat.1003428] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2012] [Accepted: 04/25/2013] [Indexed: 12/20/2022] Open
Abstract
Two-component signaling systems (TCSs) are major mechanisms by which bacteria adapt to environmental conditions. It follows then that TCSs would play important roles in the adaptation of pathogenic bacteria to host environments. However, no pathogen-associated TCS has been identified in uropathogenic Escherichia coli (UPEC). Here, we identified a novel TCS, which we termed KguS/KguR (KguS: α-ketoglutarate utilization sensor; KguR: α-ketoglutarate utilization regulator) in UPEC CFT073, a strain isolated from human pyelonephritis. kguS/kguR was strongly associated with UPEC but was found only rarely among other E. coli including commensal and intestinal pathogenic strains. An in vivo competition assay in a mouse UTI model showed that deletion of kguS/kguR in UPEC CFT073 resulted in a significant reduction in its colonization of the bladders and kidneys of mice, suggesting that KguS/KguR contributed to UPEC fitness in vivo. Comparative proteomics identified the target gene products of KguS/KguR, and sequence analysis showed that TCS KguS/KguR and its targeted-genes, c5032 to c5039, are encoded on a genomic island, which is not present in intestinal pathogenic E. coli. Expression of the target genes was induced by α-ketoglutarate (α-KG). These genes were further shown to be involved in utilization of α-KG as a sole carbon source under anaerobic conditions. KguS/KguR contributed to the regulation of the target genes with the direct regulation by KguR verified using an electrophoretic mobility shift assay. In addition, oxygen deficiency positively modulated expression of kguS/kguR and its target genes. Taken altogether, this study describes the first UPEC-associated TCS that functions in controlling the utilization of α-ketoglutarate in vivo thereby facilitating UPEC adaptation to life inside the urinary tract.
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Affiliation(s)
- Wentong Cai
- Department of Veterinary Microbiology and Preventive Medicine, College of Veterinary Medicine, Iowa State University, Ames, Iowa, United States of America
| | - Yvonne Wannemuehler
- Department of Veterinary Microbiology and Preventive Medicine, College of Veterinary Medicine, Iowa State University, Ames, Iowa, United States of America
| | - Giuseppe Dell'Anna
- Laboratory Animal Resources, College of Veterinary Medicine, Iowa State University, Ames, Iowa, United States of America
| | - Bryon Nicholson
- Department of Veterinary Microbiology and Preventive Medicine, College of Veterinary Medicine, Iowa State University, Ames, Iowa, United States of America
| | - Nicolle L. Barbieri
- Department of Veterinary Microbiology and Preventive Medicine, College of Veterinary Medicine, Iowa State University, Ames, Iowa, United States of America
- Departamento de Biofísica, Universidade Federal do Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, Brasil
| | - Subhashinie Kariyawasam
- Department of Veterinary and Biomedical Sciences, Pennsylvania State University, University Park, Pennsylvania, United States of America
| | - Yaping Feng
- Laurence H. Baker Center for Bioinformatics and Biological Statistics, Iowa State University, Ames, Iowa, United States of America
| | - Catherine M. Logue
- Department of Veterinary Microbiology and Preventive Medicine, College of Veterinary Medicine, Iowa State University, Ames, Iowa, United States of America
| | - Lisa K. Nolan
- Department of Veterinary Microbiology and Preventive Medicine, College of Veterinary Medicine, Iowa State University, Ames, Iowa, United States of America
| | - Ganwu Li
- Department of Veterinary Microbiology and Preventive Medicine, College of Veterinary Medicine, Iowa State University, Ames, Iowa, United States of America
- * E-mail:
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11
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Prasad UV, Vasu D, Kumar YN, Kumar PS, Yeswanth S, Swarupa V, Phaneendra BV, Chaudhary A, Sarma PVGK. Cloning, expression and characterization of NADP-dependent isocitrate dehydrogenase from Staphylococcus aureus. Appl Biochem Biotechnol 2013; 169:862-9. [PMID: 23288593 DOI: 10.1007/s12010-012-0027-8] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2012] [Accepted: 12/10/2012] [Indexed: 12/01/2022]
Abstract
The Krebs cycle dictates oxidative and reductive conditions in Staphylococcus aureus and is mainly regulated by isocitrate dehydrogenase (IDH) which plays pivotal role in the growth and pathogenesis of the bacteria. In the present study, IDH gene from S. aureus ATCC12600 was cloned in the Sma I site of pQE 30 vector; the resultant clone was named as UVIDH1. The insert in the clone was sequenced (accession number HM067707), and the sequence showed complete homology with IDH sequence of other S. aureus strains reported in the database indicating presence of single enzyme in S. aureus, and considerable sequence homology with other bacteria was observed; however, only 24% homology was found with NADP-dependent human IDH. Phylogenetically, the S. aureus IDH showed close identity with Bacillus subtilis and high degree of variability with other bacteria and human IDH. The expression of IDH in the clone UVIDH1 was induced with 1 mM IPTG, and the recombinant IDH was purified by passing through nickel metal chelate column; the purified recombinant IDH showed a single band in SDS-PAGE with a molecular weight of 40 kDa; K(m) and V(max) for isocitrate are 8.2 ± 0.28 and 525 ± 25 μM NADPH/mg/min, respectively, and for cofactor NADP 67.5 ± 2.82 μM and V(max) 50.5 ± 2.12 μM NADPH/mg/min.
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Affiliation(s)
- U Venkateswara Prasad
- Department of Biotechnology, Sri Venkateswara Institute of Medical Sciences, Tirupati 517507, India
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12
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Unden G, Nilkens S, Singenstreu M. Bacterial sensor kinases using Fe-S cluster binding PAS or GAF domains for O2 sensing. Dalton Trans 2012; 42:3082-7. [PMID: 23138661 DOI: 10.1039/c2dt32089d] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
[4Fe-4S](2+) clusters are used by very diverse types of bacterial sensors for response to oxygen, including DNA-binding proteins of the CRP/FNR family and sensor kinases like NreB. In NreB the cluster is bound by an input domain of the PAS type. The [4Fe-4S](2+) cluster of NreB responds to O(2) by degradation to a [2Fe-2S](2+) cluster which is labile and decomposes. NreB constitutes together with AirS the NreB/AirS family of bacterial sensor kinases that contain PAS or GAF domains for binding of [4Fe-4S](2+) or [2Fe-2S](2+) clusters and oxygen sensing. The NreB/AirS family is related to the FixL sensor kinases that use hemeB binding PAS domains for oxygen sensing.
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Affiliation(s)
- Gottfried Unden
- Institute for Microbiology and Wine Research, University of Mainz, Mainz, Germany.
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13
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Sun Z, Do PM, Rhee MS, Govindasamy L, Wang Q, Ingram LO, Shanmugam KT. Amino acid substitutions at glutamate-354 in dihydrolipoamide dehydrogenase of Escherichia coli lower the sensitivity of pyruvate dehydrogenase to NADH. MICROBIOLOGY-SGM 2012; 158:1350-1358. [PMID: 22343352 DOI: 10.1099/mic.0.055590-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Pyruvate dehydrogenase (PDH) of Escherichia coli is inhibited by NADH. This inhibition is partially reversed by mutational alteration of the dihydrolipoamide dehydrogenase (LPD) component of the PDH complex (E354K or H322Y). Such a mutation in lpd led to a PDH complex that was functional in an anaerobic culture as seen by restoration of anaerobic growth of a pflB, ldhA double mutant of E. coli utilizing a PDH- and alcohol dehydrogenase-dependent homoethanol fermentation pathway. The glutamate at position 354 in LPD was systematically changed to all of the other natural amino acids to evaluate the physiological consequences. These amino acid replacements did not affect the PDH-dependent aerobic growth. With the exception of E354M, all changes also restored PDH-dependent anaerobic growth of and fermentation by an ldhA, pflB double mutant. The PDH complex with an LPD alteration E354G, E354P or E354W had an approximately 20-fold increase in the apparent K(i) for NADH compared with the native complex. The apparent K(m) for pyruvate or NAD(+) for the mutated forms of PDH was not significantly different from that of the native enzyme. A structural model of LPD suggests that the amino acid at position 354 could influence movement of NADH from its binding site to the surface. These results indicate that glutamate at position 354 plays a structural role in establishing the NADH sensitivity of LPD and the PDH complex by restricting movement of the product/substrate NADH, although this amino acid is not directly associated with NAD(H) binding.
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Affiliation(s)
- Zhentao Sun
- Department of Microbiology and Cell Science, University of Florida, Gainesville, FL 32611, USA
- College of Resources and Environmental Sciences, China Agricultural University, PR China
| | - Phi Minh Do
- Department of Microbiology and Cell Science, University of Florida, Gainesville, FL 32611, USA
| | - Mun Su Rhee
- Department of Microbiology and Cell Science, University of Florida, Gainesville, FL 32611, USA
| | - Lakshmanan Govindasamy
- Department of Biochemistry and Molecular Biology, University of Florida, Gainesville, FL 32611, USA
| | - Qingzhao Wang
- Department of Microbiology and Cell Science, University of Florida, Gainesville, FL 32611, USA
| | - Lonnie O Ingram
- Department of Microbiology and Cell Science, University of Florida, Gainesville, FL 32611, USA
| | - K T Shanmugam
- Department of Microbiology and Cell Science, University of Florida, Gainesville, FL 32611, USA
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14
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Wagner T, Bellinzoni M, Wehenkel A, O'Hare HM, Alzari PM. Functional plasticity and allosteric regulation of α-ketoglutarate decarboxylase in central mycobacterial metabolism. ACTA ACUST UNITED AC 2011; 18:1011-20. [PMID: 21867916 DOI: 10.1016/j.chembiol.2011.06.004] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2011] [Revised: 05/24/2011] [Accepted: 06/07/2011] [Indexed: 11/18/2022]
Abstract
The α-ketoglutarate dehydrogenase (KDH) complex is a major regulatory point of aerobic energy metabolism. Mycobacterium tuberculosis was reported to lack KDH activity, and the putative KDH E1o component, α-ketoglutarate decarboxylase (KGD), was instead assigned as a decarboxylase or carboligase. Here, we show that this protein does in fact sustain KDH activity, as well as the additional two reactions, and these multifunctional properties are shared by the Escherichia coli homolog, SucA. We also show that the mycobacterial enzyme is finely regulated by an additional acyltransferase-like domain and by the action of acetyl-CoA, a powerful allosteric activator able to enhance the concerted protein motions observed during catalysis. Our results uncover the functional plasticity of a crucial node in bacterial metabolism, which may be important for M. tuberculosis during host infection.
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Affiliation(s)
- Tristan Wagner
- Institut Pasteur, Unité de Biochimie Structurale (CNRS URA 2185), 25 rue du Dr. Roux, 75724 Paris, France
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15
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Zhao H, de Carvalho LPS, Nathan C, Ouerfelli O. A protecting group-free synthesis of deazathiamine: a step toward inhibitor design. Bioorg Med Chem Lett 2010; 20:6472-4. [PMID: 20943392 DOI: 10.1016/j.bmcl.2010.09.053] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2010] [Revised: 09/07/2010] [Accepted: 09/10/2010] [Indexed: 11/19/2022]
Abstract
The discovery of 3-deazathiamine diphosphate (deazaThDP) as a potent inhibitor analog of the cofactor thiamine diphosphate (ThDP) has highlighted the need for an efficient and scalable synthesis of deazaThDP. Such a method would facilitate development of analogs with the ability to inhibit individual ThDP-dependent enzymes selectively. Toward the goal of developing selective inhibitors of the mycobacterial enzyme 2-hydroxy-3-oxoadipate synthase (HOAS), we report an improved synthesis of deazaThDP without use of protecting groups. Tribromo-3-methylthiophene served as a versatile starting material whose selective functionalization permitted access to deazaThDP in five steps, with potential to make other analogs accessible in substantial amounts.
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Affiliation(s)
- Hong Zhao
- Organic Synthesis Core Facility, Molecular Pharmacology and Chemistry Program, Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, PO Box 237, New York, NY 10065, United States
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16
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The O2 sensitivity of the transcription factor FNR is controlled by Ser24 modulating the kinetics of [4Fe-4S] to [2Fe-2S] conversion. Proc Natl Acad Sci U S A 2009; 106:4659-64. [PMID: 19261852 DOI: 10.1073/pnas.0804943106] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Fumarate and nitrate reduction regulatory (FNR) proteins are bacterial transcription factors that coordinate the switch between aerobic and anaerobic metabolism. In the absence of O(2), FNR binds a [4Fe-4S](2+) cluster (ligated by Cys-20, 23, 29, 122) promoting the formation of a transcriptionally active dimer. In the presence of O(2), FNR is converted into a monomeric, non-DNA-binding form containing a [2Fe-2S](2+) cluster. The reaction of the [4Fe-4S](2+) cluster with O(2) has been shown to proceed via a 2-step process, an O(2)-dependent 1-electron oxidation to yield a [3Fe-4S](+) intermediate with release of 1 Fe(2+) ion, followed by spontaneous rearrangement to the [2Fe-2S](2+) form with release of 1 Fe(3+) and 2 S(2-) ions. Here, we show that replacement of Ser-24 by Arg, His, Phe, Trp, or Tyr enhances aerobic activity of FNR in vivo. The FNR-S24F protein incorporates a [4Fe-4S](2+) cluster with spectroscopic properties similar to those of FNR. However, the substitution enhances the stability of the [4Fe-4S](2+) cluster in the presence of O(2). Kinetic analysis shows that both steps 1 and 2 are slower for FNR-S24F than for FNR. A molecular model suggests that step 1 of the FNR-S24F iron-sulfur cluster reaction with O(2) is inhibited by shielding of the iron ligand Cys-23, suggesting that Cys-23 or the cluster iron bound to it is a primary site of O(2) interaction. These data lead to a simple model of the FNR switch with physiological implications for the ability of FNR proteins to operate over different ranges of in vivo O(2) concentrations.
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Abstract
The metabolic flexibility of bacteria is key to their ability to survive and thrive in a wide range of environments. Optimal switching from one metabolic pathway to another is a key requirement for this flexibility. Respiration is a good example: many bacteria utilize O(2) as the terminal electron acceptor, but can switch to a range of other acceptors, such as nitrate, when O(2) becomes limiting. Sensing environmental levels of O(2) is the key step in switching from aerobic to anaerobic respiration. In Escherichia coli, the fumarate and nitrate reduction transcriptional regulator (FNR) controls this switch. Under O(2)-limiting conditions, FNR binds a [4Fe-4S](2+) cluster, generating a transcriptionally active dimeric form. Exposure to O(2) results in conversion of the cluster into a [2Fe-2S](2+) form, leading to dissociation of the protein into inactive monomers. The mechanism of cluster conversion, together with the nature of the reaction products, is of considerable current interest, and a near-complete description of the process has now emerged. The [4Fe-4S](2+) into [2Fe-2S](2+) cluster conversion proceeds via a two-step mechanism. In step 1, a one-electron oxidation of the cluster takes place, resulting in the release of a Fe(2+) ion, the formation of an intermediate [3Fe-4S](1+) cluster, together with the generation of a superoxide anion. In step 2, the intermediate [3Fe-4S](1+) cluster rearranges spontaneously to form the [2Fe-2S](2+) cluster, releasing two sulfide ions and an Fe(3+) ion in the process. The one-electron activation of the cluster, coupled to catalytic recycling of the superoxide anion back to oxygen via superoxide dismutase and catalase, provides a novel means of amplifying the sensitivity of [4Fe-4S](2+) FNR to its signal molecule.
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Müllner M, Hammel O, Mienert B, Schlag S, Bill E, Unden G. A PAS domain with an oxygen labile [4Fe-4S](2+) cluster in the oxygen sensor kinase NreB of Staphylococcus carnosus. Biochemistry 2009; 47:13921-32. [PMID: 19102705 DOI: 10.1021/bi8014086] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The cytoplasmic histidine sensor kinase NreB of Staphylococcus carnosus responds to O(2) and controls together with the response regulator NreC the expression of genes of nitrate/nitrite respiration. nreBC homologous genes were found in Staphylococcus strains and Bacillus clausii, and a modified form was found in some Lactobacillus strains. NreB contains a sensory domain with similarity to heme B binding PAS domains. Anaerobically prepared NreB of S. carnosus exhibited a (diamagnetic) [4Fe-4S](2+) cluster when assessed by Mossbauer spectroscopy. Upon reaction with air, the cluster was degraded with a half-life of approximately 2.5 min. No significant amounts of Mossbauer or EPR detectable intermediates were found during the decay, but magnetic Mossbauer spectra revealed formation of diamagnetic [2Fe-2S](2+) clusters. After extended exposure to air, NreB was devoid of a FeS cluster. Photoreduction with deazaflavin produced small amounts of [4Fe-4S](+), which were degraded subsequently. The magnetically perturbed Mossbauer spectrum of the [4Fe-4S](2+) cluster corroborated the S = 0 spin state and revealed uniform electric field gradient tensors of the iron sites, suggesting full delocalization of the valence electrons and binding of each of the Fe ions by four S ligands, including the ligand to the protein. Mutation of each of the four Cys residues inactivated NreB function in vivo in accordance with their role as ligands. [4Fe-4S](2+) cluster-containing NreB had high kinase activity. Exposure to air decreased the kinase activity and content of the [4Fe-4S](2+) cluster with similar half-lives. We conclude that the sensory domain of NreB represents a new type of PAS domain containing a [4Fe-4S](2+) cluster for sensing and function.
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Affiliation(s)
- Martin Müllner
- Institut fur Mikrobiologie and Weinforschung, Universitat Mainz, Becherweg 15, 55099 Mainz, Germany
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Yee N, Kobayashi DY. Chapter 3 Molecular Genetics of Selenate Reduction by Enterobacter cloacae SLD1a‐1. ADVANCES IN APPLIED MICROBIOLOGY 2008; 64:107-23, 2 p following 264. [DOI: 10.1016/s0065-2164(08)00403-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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20
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Crack JC, Le Brun NE, Thomson AJ, Green J, Jervis AJ. Reactions of nitric oxide and oxygen with the regulator of fumarate and nitrate reduction, a global transcriptional regulator, during anaerobic growth of Escherichia coli. Methods Enzymol 2008; 437:191-209. [PMID: 18433630 DOI: 10.1016/s0076-6879(07)37011-0] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The Escherichia coli fumarate and nitrate reductase (FNR) regulator protein is an important transcriptional regulator that controls the expression of a large regulon of more than 100 genes in response to changes in oxygen availability. FNR is active when it acquires a [4Fe-4S](2+) cluster under anaerobic conditions. The presence of the [4Fe-4S](2+) cluster promotes protein dimerization and site-specific DNA binding, facilitating activation or repression of target promoters. Oxygen is sensed by the controlled disassembly of the [4Fe-4S](2+) cluster, ultimately resulting in inactive, monomeric, apo-FNR. The FNR [4Fe-4S](2+) cluster is also sensitive to nitric oxide, such that under anaerobic conditions the protein is inactivated by nitrosylation of the iron-sulfur cluster, yielding a mixture of monomeric and dimeric dinitrosyl-iron cysteine species. This chapter describes some of the methods used to produce active [4Fe-4S] FNR protein and investigates the reaction of the [4Fe-4S](2+) cluster with nitric oxide and oxygen in vitro.
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Affiliation(s)
- Jason C Crack
- Centre for Metalloprotein Spectroscopy and Biology, School of Chemical Sciences and Pharmacy, University of East Anglia, Norwich, United Kingdom
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21
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Jervis AJ, Green J. In vivo demonstration of FNR dimers in response to lower O(2) availability. J Bacteriol 2007; 189:2930-2. [PMID: 17277055 PMCID: PMC1855794 DOI: 10.1128/jb.01921-06] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Escherichia coli FNR is an O(2)-sensing transcription factor. In vitro studies indicate that anaerobic iron-sulfur cluster acquisition promotes FNR dimerization. Here, two-hybrid assays show that iron-sulfur cluster-dependent FNR dimers are formed in vivo in response to lower O(2) availability, consistent with the current model of FNR activation.
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Affiliation(s)
- Adrian J Jervis
- Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield S10 2TN, United Kingdom
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Crack JC, Green J, Cheesman MR, Le Brun NE, Thomson AJ. Superoxide-mediated amplification of the oxygen-induced switch from [4Fe-4S] to [2Fe-2S] clusters in the transcriptional regulator FNR. Proc Natl Acad Sci U S A 2007; 104:2092-7. [PMID: 17267605 PMCID: PMC1892919 DOI: 10.1073/pnas.0609514104] [Citation(s) in RCA: 99] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In Escherichia coli, the switch between aerobic and anaerobic metabolism is controlled primarily by FNR (regulator of fumarate and nitrate reduction), the protein that regulates the transcription of >100 genes in response to oxygen. Under oxygen-limiting conditions, FNR binds a [4Fe-4S]2+ cluster, generating a transcriptionally active dimeric form. Upon exposure to oxygen the cluster converts to a [2Fe-2S]2+ form, leading to dissociation of the protein into monomers, which are incapable of binding DNA with high affinity. The mechanism of cluster conversion together with the nature of the products of conversion is of considerable current interest. Here, we demonstrate that [4Fe-4S]2+ to [2Fe-2S]2+ cluster conversion, in both native and reconstituted [4Fe-4S] FNR, proceeds via a one electron oxidation of the cluster, to give a [3Fe-4S]1+ cluster intermediate, with the release of one Fe2+ ion and a superoxide ion. The cluster intermediate subsequently rearranges spontaneously to form the [2Fe-2S]2+ cluster, with the release of a Fe3+ ion and, as previously shown, two sulfide ions. Superoxide ion undergoes dismutation to hydrogen peroxide and oxygen. This mechanism, a one electron activation of the cluster, coupled to catalytic recycling of the resulting superoxide ion back to oxygen, provides a means of amplifying the sensitivity of [4Fe-4S] FNR to its signal molecule.
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Affiliation(s)
- Jason C. Crack
- *Centre for Metalloprotein Spectroscopy and Biology, School of Chemical Sciences and Pharmacy, University of East Anglia, Norwich NR4 7TJ, United Kingdom; and
| | - Jeffrey Green
- Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield S10 2TN, United Kingdom
| | - Myles R. Cheesman
- *Centre for Metalloprotein Spectroscopy and Biology, School of Chemical Sciences and Pharmacy, University of East Anglia, Norwich NR4 7TJ, United Kingdom; and
| | - Nick E. Le Brun
- *Centre for Metalloprotein Spectroscopy and Biology, School of Chemical Sciences and Pharmacy, University of East Anglia, Norwich NR4 7TJ, United Kingdom; and
- To whom correspondence may be addressed. E-mail:
or
| | - Andrew J. Thomson
- *Centre for Metalloprotein Spectroscopy and Biology, School of Chemical Sciences and Pharmacy, University of East Anglia, Norwich NR4 7TJ, United Kingdom; and
- To whom correspondence may be addressed. E-mail:
or
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Yee N, Ma J, Dalia A, Boonfueng T, Kobayashi DY. Se(VI) reduction and the precipitation of Se(0) by the facultative bacterium Enterobacter cloacae SLD1a-1 are regulated by FNR. Appl Environ Microbiol 2007; 73:1914-20. [PMID: 17261520 PMCID: PMC1828800 DOI: 10.1128/aem.02542-06] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The fate of selenium in the environment is controlled, in part, by microbial selenium oxyanion reduction and Se(0) precipitation. In this study, we identified a genetic regulator that controls selenate reductase activity in the Se-reducing bacterium Enterobacter cloacae SLD1a-1. Heterologous expression of the global anaerobic regulatory gene fnr (fumarate nitrate reduction regulator) from E. cloacae in the non-Se-reducing strain Escherichia coli S17-1 activated the ability to reduce Se(VI) and precipitate insoluble Se(0) particles. Se(VI) reduction by E. coli S17-1 containing the fnr gene occurred at rates similar to those for E. cloacae, with first-order reaction constants of k = 2.07 x 10(-2) h(-1) and k = 3.36 x 10(-2) h(-1), respectively, and produced elemental selenium particles with identical morphologies and short-range atomic orders. Mutation of the fnr gene in E. cloacae SLD1a-1 resulted in derivative strains that were deficient in selenate reductase activity and unable to precipitate elemental selenium. Complementation by the wild-type fnr sequence restored the ability of mutant strains to reduce Se(VI). Our findings suggest that Se(VI) reduction and the precipitation of Se(0) by facultative anaerobes are regulated by oxygen-sensing transcription factors and occur under suboxic conditions.
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Affiliation(s)
- N Yee
- Department of Environmental Sciences, Rutgers University, 14 College Farm Rd., New Brunswick, NJ 07102, USA.
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24
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Aller MA, Arias JL, Arias JI, Sánchez-Patán F, Arias J. The inflammatory response recapitulates phylogeny through trophic mechanisms to the injured tissue. Med Hypotheses 2006; 68:202-9. [PMID: 16963191 DOI: 10.1016/j.mehy.2006.07.004] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2006] [Revised: 06/16/2006] [Accepted: 07/05/2006] [Indexed: 10/24/2022]
Abstract
The post-traumatic local acute inflammatory response is described as a succession of three functional phases of possible trophic significance: 1. Nervous or immediate (ischemia-reperfusion); 2. Immune or intermediate (infiltration by inflammatory and bacterial cells) and 3. Endocrine or late (angiogenesis with regeneration and/or cicatrization). Each of these phases emphasizes the trophic role of the mechanisms in the damaged tissue. Hence, the nervous phase is predominated by nutrition by diffusion; in the immune phase trophism is mediated by inflammatory cells and bacteria and, finally, in the endocrine phase, the blood circulation and oxidative metabolism play the most significant nutritive role. Since these trophic mechanisms are of increasing complexity, progressing from anoxia to total specialization in the use of oxygen to obtain usable energy, it could be speculated that they represent the successive reappearance of the stages that take place during the evolution of life on Earth, from ancient times without oxygen. In this sense, the inflammatory response could recapitulate phylogeny through the successive expression of pathophysiologic mechanisms that have a trophic meaning to the injured tissue.
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Affiliation(s)
- M A Aller
- Surgery Department, School of Medicine, Complutense University of Madrid, Spain
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25
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Crack JC, Green J, Le Brun NE, Thomson AJ. Detection of sulfide release from the oxygen-sensing [4Fe-4S] cluster of FNR. J Biol Chem 2006; 281:18909-13. [PMID: 16717103 DOI: 10.1074/jbc.c600042200] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The Escherichia coli FNR protein regulates the transcription of >100 genes in response to environmental O2, thereby coordinating the response to anoxia. Under O2-limiting conditions, FNR binds a [4Fe-4S]2+ cluster through four cysteine residues (Cys20, Cys23, Cys29, Cys122). The acquisition of the [4Fe-4S]2+ cluster converts FNR into the transcriptionally active dimeric form. Upon exposure to O2, the cluster converts to a [2Fe-2S]2+ form, generating FNR monomers that no longer bind DNA with high affinity. The mechanism of the cluster conversion reaction and the nature of the released iron and sulfur are of considerable current interest. Here, we report the application of a novel in vitro method, involving 5,5'-dithiobis-(2-nitrobenzoic acid), for determining the oxidation state of the sulfur atoms released during FNR cluster conversion following the addition of O2. Conversion of [4Fe-4S]2+ to [2Fe-2S]2+ clusters by O2 for both native and reconstituted FNR results in the release of approximately 2 sulfide ions per [4Fe-4S]2+ cluster. This demonstrates that the reaction between O2 and the [4Fe-4S]2+ cluster does not require sulfide oxidation and hence must entail iron oxidation.
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Affiliation(s)
- Jason C Crack
- Centre for Metalloprotein Spectroscopy and Biology, School of Chemical Sciences and Pharmacy, University of East Anglia, Norwich NR4 7TJ, United Kingdom.
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Tian J, Bryk R, Itoh M, Suematsu M, Nathan C. Variant tricarboxylic acid cycle in Mycobacterium tuberculosis: identification of alpha-ketoglutarate decarboxylase. Proc Natl Acad Sci U S A 2005; 102:10670-5. [PMID: 16027371 PMCID: PMC1180764 DOI: 10.1073/pnas.0501605102] [Citation(s) in RCA: 163] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Mycobacterium tuberculosis (Mtb) has adapted its metabolism for persistence in the human macrophage. The adaptations are likely to involve Mtb's core intermediary metabolism, whose enzymes have been little studied. The tricarboxylic acid cycle is expected to yield precursors for energy, lipids, amino acids, and heme. The genome sequence of Mtb H37Rv predicts the presence of a complete tricarboxylic acid cycle, but we recently found that alpha-ketoglutarate dehydrogenase (KDH) activity is lacking in Mtb lysates. Here we showed that citrate synthase, aconitase, isocitrate dehydrogenase, fumarase, malate dehydrogenase, and succinate dehydrogenase, but not KDH, are present, raising the possibility of separate oxidative and reductive half-cycles. As a potential link between the half-cycles, we found that Rv1248c, annotated as encoding SucA, the putative E1 component of KDH, instead encodes alpha-ketoglutarate decarboxylase (Kgd) and produces succinic semialdehyde. Succinic semialdehyde dehydrogenase activity was detected in Mtb lysates and recapitulated with recombinant proteins GabD1 (encoded by Rv0234c) and GabD2 (encoded by Rv1731). Kgd and GabD1 or GabD2 form an alternative pathway from alpha-ketoglutarate to succinate. Rv1248c, which is essential or required for normal growth of Mtb [Sassetti, C., Boyd, D. H. & Rubin, E. J. (2003) Mol. Microbiol 48, 77-84] is the first gene shown to encode a Kgd. Kgd is lacking in humans and may represent a potential target for chemotherapy of tuberculosis.
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Affiliation(s)
- Jing Tian
- Department of Microbiology and Immunology, Weill Medical College of Cornell University, New York, NY 10021, USA
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Affiliation(s)
- Jose-Ignacio Arias
- Servicio de Cirugía General, Hospital Monte Naranco, Oviedo, Asturias, Spain
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Crack J, Green J, Thomson AJ. Mechanism of oxygen sensing by the bacterial transcription factor fumarate-nitrate reduction (FNR). J Biol Chem 2003; 279:9278-86. [PMID: 14645253 DOI: 10.1074/jbc.m309878200] [Citation(s) in RCA: 109] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The facultative anaerobe Escherichia coli adopts different metabolic modes in response to the availability of oxygen. The global transcriptional regulator FNR (fumarate-nitrate reduction) monitors the availability of oxygen in the environment. Binding as a homodimer to palindromic sequences of DNA, FNR carries a sensory domain, remote from the DNA binding helix-turn-helix motif, which responds to oxygen. The sensing mechanism involves the transformation of a [4Fe-4S](2+) cluster into a [2Fe-2S] form in vitro on reaction with oxygen. Evidence is presented to show that this process proceeds by at least two steps, the first, an oxidative one, being the formation, on reaction with O(2), of a [3Fe-4S](1+) cluster as an intermediate accompanied by the production of hydrogen peroxide. This is followed by a slower, non-redox, pseudo-first order step in which the [3Fe-4S](1+) form converts to a [2Fe-2S](2+) cluster. This must be accompanied by a substantial protein conformational change since the four cysteine ligands that bind the two forms of the FeS clusters have different spatial disposition. Hydrogen peroxide is also an oxidant of the [4Fe-4S](2+), causing a similar cluster transformation to a [2Fe-2S] form. Either the hydrogen peroxide formed on reaction with oxygen can be recycled by intracellular catalase or it can be used to oxidize further Fe-S clusters. In both cases, the efficacy of oxygen sensing by FNR will be increased.
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Affiliation(s)
- Jason Crack
- School of Chemical Sciences and Pharmacy, University of East Anglia, Norwich, NR4 7TJ
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Kokeguchi S, Hirosue M, Maeda H, Miyamoto M, Takashiba S, Murayama Y. Molecular characterization of the hlyX-like gene of Actinobacillus actinomycetemcomitans Y4. Res Microbiol 2000; 151:721-5. [PMID: 11130862 DOI: 10.1016/s0923-2508(00)01137-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
We isolated and characterized a possible regulatory gene, designated actX gene, from Actinobacillus actinomyctemcomitans Y4, which defined the Actinobacillus pleuropneumoniae hlyX-like regulatory gene. DNA sequence analysis for plasmid clone pKM317 containing a 1.6-kb DNA insert indicated an open reading frame encoding a polypeptide of 257 amino acid residues. Analysis of the deduced amino acid sequence showed the presence of five characteristic cysteine residues in the N-terminal region and a putative DNA binding residue in the C-terminal region, indicating that actX might belong to a regulatory gene family. Escherichia coli DH5alpha and a mutant strain JRG1728 transformed by plasmid carrying actX manifested apparent hemolytic activity on sheep blood agar and grew anaerobically, although the original strains did not.
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Affiliation(s)
- S Kokeguchi
- Department of Periodontology and Endodontology, Okayama University Dental School, Japan
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Pitson SM, Mendz GL, Srinivasan S, Hazell SL. The tricarboxylic acid cycle of Helicobacter pylori. EUROPEAN JOURNAL OF BIOCHEMISTRY 1999; 260:258-67. [PMID: 10091606 DOI: 10.1046/j.1432-1327.1999.00153.x] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The composition and properties of the tricarboxylic acid cycle of the microaerophilic human pathogen Helicobacter pylori were investigated in situ and in cell extracts using [1H]- and [13C]-NMR spectroscopy and spectrophotometry. NMR spectroscopy assays enabled highly specific measurements of some enzyme activities, previously not possible using spectrophotometry, in in situ studies with H. pylori, thus providing the first accurate picture of the complete tricarboxylic acid cycle of the bacterium. The presence, cellular location and kinetic parameters of citrate synthase, aconitase, isocitrate dehydrogenase, alpha-ketoglutarate oxidase, fumarate reductase, fumarase, malate dehydrogenase, and malate synthase activities in H. pylori are described. The absence of other enzyme activities of the cycle, including alpha-ketoglutarate dehydrogenase, succinyl-CoA synthetase, and succinate dehydrogenase also are shown. The H. pylori tricarboxylic acid cycle appears to be a noncyclic, branched pathway, characteristic of anaerobic metabolism, directed towards the production of succinate in the reductive dicarboxylic acid branch and alpha-ketoglutarate in the oxidative tricarboxylic acid branch. Both branches were metabolically linked by the presence of alpha-ketoglutarate oxidase activity. Under the growth conditions employed, H. pylori did not possess an operational glyoxylate bypass, owing to the absence of isocitrate lyase activity; nor a gamma-aminobutyrate shunt, owing to the absence of both gamma-aminobutyrate transaminase and succinic semialdehyde dehydrogenase activities. The catalytic and regulatory properties of the H. pylori tricarboxylic acid cycle enzymes are discussed by comparing their amino acid sequences with those of other, more extensively studied enzymes.
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Affiliation(s)
- S M Pitson
- School of Biochemistry and Molecular Genetics, University of New South Wales, Sydney, Australia
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Abstract
Escherichia coli has two primary pathways for glutamate synthesis. The glutamine synthetase-glutamate synthase (GOGAT) pathway is essential for synthesis at low ammonium concentration and for regulation of the glutamine pool. The glutamate dehydrogenase (GDH) pathway is important during glucose-limited growth. It has been hypothesized that GDH is favored when the organism is stressed for energy, because the enzyme does not use ATP as does the GOGAT pathway. The results of competition experiments between the wild-type and a GDH-deficient mutant during glucose-limited growth in the presence of the nonmetabolizable glucose analog alpha-methylglucoside were consistent with the hypothesis. Enzyme measurements showed that levels of the enzymes of the glutamate pathways dropped as the organism passed from unrestricted to glucose-restricted growth. However, other conditions influencing pathway choice had no substantial effect on enzyme levels. Therefore, substrate availability and/or modulation of enzyme activity are likely to be major determinants of pathway choice in glutamate synthesis.
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Affiliation(s)
- R B Helling
- Department of Biology, University of Michigan, Ann Arbor, Michigan 48109, USA.
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Green J, Guest JR. The Citric Acid Cycle and Oxygen-Regulated Gene Expression in Escherichia coli. Mol Microbiol 1998. [DOI: 10.1007/978-3-642-72071-0_2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Abstract
Denitrification is a distinct means of energy conservation, making use of N oxides as terminal electron acceptors for cellular bioenergetics under anaerobic, microaerophilic, and occasionally aerobic conditions. The process is an essential branch of the global N cycle, reversing dinitrogen fixation, and is associated with chemolithotrophic, phototrophic, diazotrophic, or organotrophic metabolism but generally not with obligately anaerobic life. Discovered more than a century ago and believed to be exclusively a bacterial trait, denitrification has now been found in halophilic and hyperthermophilic archaea and in the mitochondria of fungi, raising evolutionarily intriguing vistas. Important advances in the biochemical characterization of denitrification and the underlying genetics have been achieved with Pseudomonas stutzeri, Pseudomonas aeruginosa, Paracoccus denitrificans, Ralstonia eutropha, and Rhodobacter sphaeroides. Pseudomonads represent one of the largest assemblies of the denitrifying bacteria within a single genus, favoring their use as model organisms. Around 50 genes are required within a single bacterium to encode the core structures of the denitrification apparatus. Much of the denitrification process of gram-negative bacteria has been found confined to the periplasm, whereas the topology and enzymology of the gram-positive bacteria are less well established. The activation and enzymatic transformation of N oxides is based on the redox chemistry of Fe, Cu, and Mo. Biochemical breakthroughs have included the X-ray structures of the two types of respiratory nitrite reductases and the isolation of the novel enzymes nitric oxide reductase and nitrous oxide reductase, as well as their structural characterization by indirect spectroscopic means. This revealed unexpected relationships among denitrification enzymes and respiratory oxygen reductases. Denitrification is intimately related to fundamental cellular processes that include primary and secondary transport, protein translocation, cytochrome c biogenesis, anaerobic gene regulation, metalloprotein assembly, and the biosynthesis of the cofactors molybdopterin and heme D1. An important class of regulators for the anaerobic expression of the denitrification apparatus are transcription factors of the greater FNR family. Nitrate and nitric oxide, in addition to being respiratory substrates, have been identified as signaling molecules for the induction of distinct N oxide-metabolizing enzymes.
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Affiliation(s)
- W G Zumft
- Lehrstuhl für Mikrobiologie, Universität Fridericiana, Karlsruhe, Germany
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Contreras I, Toro CS, Troncoso G, Mora GC. Salmonella typhi mutants defective in anaerobic respiration are impaired in their ability to replicate within epithelial cells. MICROBIOLOGY (READING, ENGLAND) 1997; 143 ( Pt 8):2665-2672. [PMID: 9274020 DOI: 10.1099/00221287-143-8-2665] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
By using MudJ (Kan, lac)-directed operon fusion technology, mutants of Salmonella typhi whose gene expression is induced under anaerobic growth conditions were isolated. Characterization of their phenotypes and regulatory properties revealed that two of the mutants were unable to use nitrate as a terminal electron acceptor in the absence of oxygen, suggesting that they were defective in nitrate reductase activity. Anaerobic induction of these fusions did not further increase in response to nitrate. Strains carrying an additional mutation in oxrA were constructed. They showed a lower level of beta-galactosidase expression both aerobically and anaerobically; however, the ratios of anaerobic induction remained unaltered. These MudJ insertions mapped to the 17-19 min region of the chromosome. Based upon their phenotypes and mapping, one of the mutants probably possessed a modC (chlD)::MudJ insertion and the other a moaA (chlA)::MudJ insertion. A third mutant was unable to use either nitrate or fumarate as a terminal electron acceptor. All three mutants showed a reduced ability to enter into and proliferate within HEp-2 epithelial cells. The oxrA mutation enhanced entry and proliferation of both the wild-type cells and the three mutants. Taken together, these results suggest that anaerobic respiration plays a role in S. typhi invasiveness.
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Affiliation(s)
- Inés Contreras
- Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile, Casilla 174 Correo 22, Santiago, Chile
| | - Cecilia S Toro
- Unidad de Microbiología, Departamento de Genética Molecular y Microbiología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Casilla 114-D, Santiago, Chile
| | - Gonzalo Troncoso
- Unidad de Microbiología, Departamento de Genética Molecular y Microbiología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Casilla 114-D, Santiago, Chile
| | - Guido C Mora
- Unidad de Microbiología, Departamento de Genética Molecular y Microbiología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Casilla 114-D, Santiago, Chile
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35
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Abstract
The aconitase family contains a diverse group of iron-sulphur (Fe-S) isomerases and two types of iron regulatory protein (IRP). Structural comparisons have revealed three architecturally distinct variants in which one of the four structural domains is covalently linked at either the amino- or carboxy-terminal end of a single polypeptide or else this domain exists as an independent subunit.
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Affiliation(s)
- M J Gruer
- Krebs Institute for Biomolecular Research, Department of Molecular Biology and Biotechnology, University of Sheffield, UK
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36
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Green J, Bennett B, Jordan P, Ralph ET, Thomson AJ, Guest JR. Reconstitution of the [4Fe-4S] cluster in FNR and demonstration of the aerobic-anaerobic transcription switch in vitro. Biochem J 1996; 316 ( Pt 3):887-92. [PMID: 8670167 PMCID: PMC1217433 DOI: 10.1042/bj3160887] [Citation(s) in RCA: 153] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
The FNR protein of Escherichia coli is a redox-responsive transcription regulator that activates and represses a family of genes required for anaerobic and aerobic metabolism. Reconstitution of wild-type FNR by anaerobic treatment with ferrous ions, cysteine and the NifS protein of Azotobacter vinelandii leads to the incorporation of two [4Fe-4S]2+ clusters per FNR dimer. The UV-visible spectrum of reconstituted FNR has a broad absorbance at 420 nm. The clusters are EPR silent under anaerobic conditions but are degraded to [3Fe-4S]+ by limited oxidation with air, and completely lost on prolonged air exposure. The association of FNR with the iron-sulphur clusters is confirmed by CD spectroscopy. Incorporation of the [4Fe-4S]2+ clusters increases site-specific DNA binding about 7-fold compared with apo-FNR. Anaerobic transcription activation and repression in vitro likewise depends on the presence of the iron-sulphur cluster, and its inactivation under aerobic conditions provides a demonstration in vitro of the FNR-mediated aerobic-anaerobic transcriptional switch.
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Affiliation(s)
- J Green
- The Krebs Institute, Department of Molecular Biology and Biotechnology, University of Sheffield, Western Bank, U.K
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37
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Bradbury AJ, Gruer MJ, Rudd KE, Guest JR. The second aconitase (AcnB) of Escherichia coli. MICROBIOLOGY (READING, ENGLAND) 1996; 142 ( Pt 2):389-400. [PMID: 8932712 DOI: 10.1099/13500872-142-2-389] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The second aconitase (AcnB) of Escherichia coli was partially purified from an acnA::kanR mutant lacking AcnA, and the corresponding polypeptide identified by activity staining and weak cross-reactivity with AcnA antiserum. The acnB gene was located at 2 center dot 85 min (131 center dot 6 kb) in a region of the chromosome previously assigned to two unidentified ORFs. Aconitase specific activities were amplified up to fivefold by infection with lambdaacnB phages from the Kohara lambda-E. coli gene library, and up to 120-fold (50% of soluble protein) by inducing transformants containing a plasmid (pGS783) in which the acnB coding region is expressed from a regulated T7 promoter. The AcnB protein was purified to > or = 98% homogeneity from a genetically enriched source (JRG3171) and shown to be a monomeric protein of Mr 100 000 (SDS-PAGE) and 105 000 (gel filtration analysis) compared with Mr 93 500 predicted from the nucleotide sequence. The sequence identity between AcnA and AcnB is only 17% and the domain organization of AcnA and related proteins (1-2-3-linker-4) is rearranged in AcnB (4-1-2-3).
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Affiliation(s)
- Alan J Bradbury
- The Krebs Institute for Biomolecular Research, Department of Molecular Biology and Biotechnology, University of Sheffield, Western Bank, Sheffield S10 2UH, UK
| | - Megan J Gruer
- The Krebs Institute for Biomolecular Research, Department of Molecular Biology and Biotechnology, University of Sheffield, Western Bank, Sheffield S10 2UH, UK
| | - Kenneth E Rudd
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD 20894, USA
| | - John R Guest
- The Krebs Institute for Biomolecular Research, Department of Molecular Biology and Biotechnology, University of Sheffield, Western Bank, Sheffield S10 2UH, UK
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