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Kachi K, Sato T, Nagasawa M, Cann I, Atomi H. The Lreu_1276 protein from Limosilactobacillus reuteri represents a third family of dihydroneopterin triphosphate pyrophosphohydrolases in bacteria. Appl Environ Microbiol 2024:e0081424. [PMID: 38888337 DOI: 10.1128/aem.00814-24] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2024] [Accepted: 05/14/2024] [Indexed: 06/20/2024] Open
Abstract
Tetrahydrofolate is a cofactor involved in C1 metabolism including biosynthesis pathways for adenine and serine. In the classical tetrahydrofolate biosynthesis pathway, the steps removing three phosphate groups from the precursor 7,8-dihydroneopterin triphosphate (DHNTP) remain unclear in many bacteria. DHNTP pyrophosphohydrolase hydrolyzes pyrophosphate from DHNTP and produces 7,8-dihydroneopterin monophosphate. Although two structurally distinct DHNTP pyrophosphohydrolases have been identified in the intestinal bacteria Lactococcus lactis and Escherichia coli, the distribution of their homologs is limited. Here, we aimed to identify a third DHNTP pyrophosphohydrolase gene in the intestinal lactic acid bacterium Limosilactobacillus reuteri. In a gene operon including genes involved in dihydrofolate biosynthesis, we focused on the lreu_1276 gene, annotated as Ham1 family protein or XTP/dITP diphosphohydrolase, as a candidate encoding DHNTP pyrophosphohydrolase. The Lreu_1276 recombinant protein was prepared using E. coli and purified. Biochemical analyses of the reaction product revealed that the Lreu_1276 protein displays significant pyrophosphohydrolase activity toward DHNTP. The optimal reaction temperature and pH were 35°C and around 7, respectively. Substrate specificity was relatively strict among 17 tested compounds. Although previously characterized DHNTP pyrophosphohydrolases prefer Mg2+, the Lreu_1276 protein exhibited maximum activity in the presence of Mn2+, with a specific activity of 28.2 ± 2.0 µmol min-1 mg-1 in the presence of 1 mM Mn2+. The three DHNTP pyrophosphohydrolases do not share structural similarity to one another, and the distribution of their homologs does not overlap, implying that the Lreu_1276 protein represents a third structurally novel DHNTP pyrophosphohydrolase in bacteria. IMPORTANCE The identification of a structurally novel DHNTP pyrophosphohydrolase in L. reuteri provides valuable information in understanding tetrahydrofolate biosynthesis in bacteria that possess lreu_1276 homologs. Interestingly, however, even with the identification of a third family of DHNTP pyrophosphohydrolases, there are still a number of bacteria that do not harbor homologs for any of the three genes while possessing other genes involved in the biosynthesis of the pterin ring structure. This suggests the presence of an unrecognized DHNTP pyrophosphohydrolase gene in bacteria. As humans do not harbor DHNTP pyrophosphohydrolase, the high structural diversity of enzymes responsible for a reaction in tetrahydrofolate biosynthesis may provide an advantage in designing inhibitors targeting a specific group of bacteria in the intestinal microbiota.
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Affiliation(s)
- Kaede Kachi
- Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Kyoto, Japan
| | - Takaaki Sato
- Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Kyoto, Japan
- Integrated Research Center for Carbon Negative Science, Kyoto University, Kyoto, Japan
| | - Maina Nagasawa
- Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Kyoto, Japan
| | - Isaac Cann
- Department of Animal Science, University of Illinois Urbana-Champaign, Urbana, Illinois, USA
- Department of Microbiology, University of Illinois Urbana-Champaign, Urbana, Illinois, USA
- Carl R. Woese Institute for Genomic Biology, University of Illinois Urbana-Champaign, Urbana, Illinois, USA
| | - Haruyuki Atomi
- Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Kyoto, Japan
- Integrated Research Center for Carbon Negative Science, Kyoto University, Kyoto, Japan
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de Crécy-Lagard V, Hutinet G, Cediel-Becerra JDD, Yuan Y, Zallot R, Chevrette MG, Ratnayake RMMN, Jaroch M, Quaiyum S, Bruner S. Biosynthesis and function of 7-deazaguanine derivatives in bacteria and phages. Microbiol Mol Biol Rev 2024; 88:e0019923. [PMID: 38421302 PMCID: PMC10966956 DOI: 10.1128/mmbr.00199-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/02/2024] Open
Abstract
SUMMARYDeazaguanine modifications play multifaceted roles in the molecular biology of DNA and tRNA, shaping diverse yet essential biological processes, including the nuanced fine-tuning of translation efficiency and the intricate modulation of codon-anticodon interactions. Beyond their roles in translation, deazaguanine modifications contribute to cellular stress resistance, self-nonself discrimination mechanisms, and host evasion defenses, directly modulating the adaptability of living organisms. Deazaguanine moieties extend beyond nucleic acid modifications, manifesting in the structural diversity of biologically active natural products. Their roles in fundamental cellular processes and their presence in biologically active natural products underscore their versatility and pivotal contributions to the intricate web of molecular interactions within living organisms. Here, we discuss the current understanding of the biosynthesis and multifaceted functions of deazaguanines, shedding light on their diverse and dynamic roles in the molecular landscape of life.
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Affiliation(s)
- Valérie de Crécy-Lagard
- Department of Microbiology and Cell Science, University of Florida, Gainesville, Florida, USA
- University of Florida Genetics Institute, Gainesville, Florida, USA
| | - Geoffrey Hutinet
- Department of Biology, Haverford College, Haverford, Pennsylvania, USA
| | | | - Yifeng Yuan
- Department of Microbiology and Cell Science, University of Florida, Gainesville, Florida, USA
| | - Rémi Zallot
- Department of Life Sciences, Manchester Metropolitan University, Manchester, United Kingdom
| | - Marc G. Chevrette
- Department of Microbiology and Cell Science, University of Florida, Gainesville, Florida, USA
| | | | - Marshall Jaroch
- Department of Microbiology and Cell Science, University of Florida, Gainesville, Florida, USA
| | - Samia Quaiyum
- Department of Microbiology and Cell Science, University of Florida, Gainesville, Florida, USA
| | - Steven Bruner
- Department of Chemistry, University of Florida, Gainesville, Florida, USA
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3
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Dual RNA-Seq of Flavobacterium psychrophilum and Its Outer Membrane Vesicles Distinguishes Genes Associated with Susceptibility to Bacterial Cold-Water Disease in Rainbow Trout (Oncorhynchus mykiss). Pathogens 2023; 12:pathogens12030436. [PMID: 36986358 PMCID: PMC10057207 DOI: 10.3390/pathogens12030436] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2022] [Revised: 03/01/2023] [Accepted: 03/08/2023] [Indexed: 03/12/2023] Open
Abstract
Flavobacterium psychrophilum (Fp), the causative agent of Bacterial Cold-Water disease in salmonids, causes substantial losses in aquaculture. Bacterial outer membrane vesicles (OMVs) contain several virulence factors, enzymes, toxins, and nucleic acids and are expected to play an essential role in host–pathogen interactions. In this study, we used transcriptome sequencing, RNA-seq, to investigate the expression abundance of the protein-coding genes in the Fp OMVs versus the Fp whole cell. RNA-seq identified 2190 transcripts expressed in the whole cell and 2046 transcripts in OMVs. Of them, 168 transcripts were uniquely identified in OMVs, 312 transcripts were expressed only in the whole cell, and 1878 transcripts were shared in the two sets. Functional annotation analysis of the OMV-abundant transcripts showed an association with the bacterial translation machinery and histone-like DNA-binding proteins. RNA-Seq of the pathogen transcriptome on day 5 post-infection of Fp-resistant versus Fp-susceptible rainbow trout genetic lines revealed differential gene expression of OMV-enriched genes, suggesting a role for the OMVs in shaping the host–microbe interaction. Interestingly, a cell wall-associated hydrolase (CWH) gene was the most highly expressed gene in OMVs and among the top upregulated transcripts in susceptible fish. The CWH sequence was conserved in 51 different strains of Fp. The study provides insights into the potential role of OMVs in host–pathogen interactions and explores microbial genes essential for virulence and pathogenesis.
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4
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Reed CJ, Hutinet G, de Crécy-Lagard V. Comparative Genomic Analysis of the DUF34 Protein Family Suggests Role as a Metal Ion Chaperone or Insertase. Biomolecules 2021; 11:1282. [PMID: 34572495 PMCID: PMC8469502 DOI: 10.3390/biom11091282] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2021] [Revised: 08/20/2021] [Accepted: 08/24/2021] [Indexed: 12/12/2022] Open
Abstract
Members of the DUF34 (domain of unknown function 34) family, also known as the NIF3 protein superfamily, are ubiquitous across superkingdoms. Proteins of this family have been widely annotated as "GTP cyclohydrolase I type 2" through electronic propagation based on one study. Here, the annotation status of this protein family was examined through a comprehensive literature review and integrative bioinformatic analyses that revealed varied pleiotropic associations and phenotypes. This analysis combined with functional complementation studies strongly challenges the current annotation and suggests that DUF34 family members may serve as metal ion insertases, chaperones, or metallocofactor maturases. This general molecular function could explain how DUF34 subgroups participate in highly diversified pathways such as cell differentiation, metal ion homeostasis, pathogen virulence, redox, and universal stress responses.
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Affiliation(s)
- Colbie J. Reed
- Department of Microbiology and Cell Science, University of Florida, Gainesville, FL 32611, USA; (C.J.R.); (G.H.)
| | - Geoffrey Hutinet
- Department of Microbiology and Cell Science, University of Florida, Gainesville, FL 32611, USA; (C.J.R.); (G.H.)
| | - Valérie de Crécy-Lagard
- Department of Microbiology and Cell Science, University of Florida, Gainesville, FL 32611, USA; (C.J.R.); (G.H.)
- Genetics Institute, University of Florida, Gainesville, FL 32611, USA
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5
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Edmonds KA, Jordan MR, Giedroc DP. COG0523 proteins: a functionally diverse family of transition metal-regulated G3E P-loop GTP hydrolases from bacteria to man. Metallomics 2021; 13:6327566. [PMID: 34302342 PMCID: PMC8360895 DOI: 10.1093/mtomcs/mfab046] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2021] [Accepted: 07/15/2021] [Indexed: 01/13/2023]
Abstract
Transition metal homeostasis ensures that cells and organisms obtain sufficient metal to meet cellular demand while dispensing with any excess so as to avoid toxicity. In bacteria, zinc restriction induces the expression of one or more Zur (zinc-uptake repressor)-regulated Cluster of Orthologous Groups (COG) COG0523 proteins. COG0523 proteins encompass a poorly understood sub-family of G3E P-loop small GTPases, others of which are known to function as metallochaperones in the maturation of cobalamin (CoII) and NiII cofactor-containing metalloenzymes. Here, we use genomic enzymology tools to functionally analyse over 80 000 sequences that are evolutionarily related to Acinetobacter baumannii ZigA (Zur-inducible GTPase), a COG0523 protein and candidate zinc metallochaperone. These sequences segregate into distinct sequence similarity network (SSN) clusters, exemplified by the ZnII-Zur-regulated and FeIII-nitrile hydratase activator CxCC (C, Cys; X, any amino acid)-containing COG0523 proteins (SSN cluster 1), NiII-UreG (clusters 2, 8), CoII-CobW (cluster 4), and NiII-HypB (cluster 5). A total of five large clusters that comprise ≈ 25% of all sequences, including cluster 3 which harbors the only structurally characterized COG0523 protein, Escherichia coli YjiA, and many uncharacterized eukaryotic COG0523 proteins. We also establish that mycobacterial-specific protein Y (Mpy) recruitment factor (Mrf), which promotes ribosome hibernation in actinomycetes under conditions of ZnII starvation, segregates into a fifth SSN cluster (cluster 17). Mrf is a COG0523 paralog that lacks all GTP-binding determinants as well as the ZnII-coordinating Cys found in CxCC-containing COG0523 proteins. On the basis of this analysis, we discuss new perspectives on the COG0523 proteins as cellular reporters of widespread nutrient stress induced by ZnII limitation.
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Affiliation(s)
- Katherine A Edmonds
- Department of Chemistry, Indiana University, Bloomington, IN 47405-7102, USA
| | - Matthew R Jordan
- Department of Chemistry, Indiana University, Bloomington, IN 47405-7102, USA.,Department of Molecular and Cellular Biochemistry, Indiana University, Bloomington, IN 47405, USA
| | - David P Giedroc
- Department of Chemistry, Indiana University, Bloomington, IN 47405-7102, USA.,Department of Molecular and Cellular Biochemistry, Indiana University, Bloomington, IN 47405, USA
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Agarwal P, Meena S, Meena LS. Comprehensive analysis of GTP cyclohydrolase I activity in Mycobacterium tuberculosis H 37 Rv via in silico studies. Biotechnol Appl Biochem 2020; 68:756-768. [PMID: 32691412 DOI: 10.1002/bab.1988] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2020] [Accepted: 07/14/2020] [Indexed: 11/06/2022]
Abstract
GTP cyclohydrolase I enzyme (GTPCH-I) is a rate limiting enzyme in the biosynthesis pathway of tetrahydrobiopterin (BH4) and tetrahydrofolate (THF) compounds; latter being are an essential compounds involved in many biological functions. This enzyme has been evaluated structurally and functionally in many organisms to understand its putative role in cell processes, kinetics, regulations, drug targeting in infectious diseases, pain sensitivity in humans, and so on. In Mycobacterium tuberculosis (a human pathogen causing tuberculosis), this GTPCH-I activity has been predicted to be present in Rv3609c gene (folE) of H37 Rv strain, which till date has not been studied in detail. In order to understand in depth, the structure and function of folE protein in M. tuberculosis H37 Rv, in silico study was designed by using many different bioinformatics tools. Comparative and structural analysis predicts that Rv3609c gene is similar to folE protein ortholog of Listeria monocytogenes (cause food born disease), and uses zinc ion as a cofactor for its catalysis. Result shows that mutation of folE protein at 52th residue from tyrosine to glycine or variation in pH and temperature can lead to high destability in protein structure. Studies here have also predicted about the functional regions and interacting partners involved with folE protein. This study has provided clues to carry out experimentally the analysis of folE protein in mycobacteria and if found suitable will be used for drug targeting.
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Affiliation(s)
- Preeti Agarwal
- CSIR-Institute of Genomics and Integrative Biology, Mall Road, Delhi, India
| | - Swati Meena
- CSIR-Institute of Genomics and Integrative Biology, Mall Road, Delhi, India
| | - Laxman S Meena
- CSIR-Institute of Genomics and Integrative Biology, Mall Road, Delhi, India
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Archaeosine Modification of Archaeal tRNA: Role in Structural Stabilization. J Bacteriol 2020; 202:JB.00748-19. [PMID: 32041795 DOI: 10.1128/jb.00748-19] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2019] [Accepted: 01/29/2020] [Indexed: 12/20/2022] Open
Abstract
Archaeosine (G+) is a structurally complex modified nucleoside found quasi-universally in the tRNA of Archaea and located at position 15 in the dihydrouridine loop, a site not modified in any tRNA outside the Archaea G+ is characterized by an unusual 7-deazaguanosine core structure with a formamidine group at the 7-position. The location of G+ at position 15, coupled with its novel molecular structure, led to a hypothesis that G+ stabilizes tRNA tertiary structure through several distinct mechanisms. To test whether G+ contributes to tRNA stability and define the biological role of G+, we investigated the consequences of introducing targeted mutations that disrupt the biosynthesis of G+ into the genome of the hyperthermophilic archaeon Thermococcus kodakarensis and the mesophilic archaeon Methanosarcina mazei, resulting in modification of the tRNA with the G+ precursor 7-cyano-7-deazaguansine (preQ0) (deletion of arcS) or no modification at position 15 (deletion of tgtA). Assays of tRNA stability from in vitro-prepared and enzymatically modified tRNA transcripts, as well as tRNA isolated from the T. kodakarensis mutant strains, demonstrate that G+ at position 15 imparts stability to tRNAs that varies depending on the overall modification state of the tRNA and the concentration of magnesium chloride and that when absent results in profound deficiencies in the thermophily of T. kodakarensis IMPORTANCE Archaeosine is ubiquitous in archaeal tRNA, where it is located at position 15. Based on its molecular structure, it was proposed to stabilize tRNA, and we show that loss of archaeosine in Thermococcus kodakarensis results in a strong temperature-sensitive phenotype, while there is no detectable phenotype when it is lost in Methanosarcina mazei Measurements of tRNA stability show that archaeosine stabilizes the tRNA structure but that this effect is much greater when it is present in otherwise unmodified tRNA transcripts than in the context of fully modified tRNA, suggesting that it may be especially important during the early stages of tRNA processing and maturation in thermophiles. Our results demonstrate how small changes in the stability of structural RNAs can be manifested in significant biological-fitness changes.
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8
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Structure-based design of guanosine analogue inhibitors targeting GTP cyclohydrolase IB towards a new class of antibiotics. Bioorg Med Chem Lett 2020; 30:126818. [PMID: 31771800 DOI: 10.1016/j.bmcl.2019.126818] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2019] [Revised: 11/07/2019] [Accepted: 11/08/2019] [Indexed: 11/24/2022]
Abstract
GTP cyclohydrolase (GCYH-I) is an enzyme in the folate biosynthesis pathway that has not been previously exploited as an antibiotic target, although several pathogens including N. gonorrhoeae use a form of the enzyme GCYH-IB that is structurally distinct from the human homologue GCYH-IA. A comparison of the crystal structures of GCYH-IA and -IB with the nM inhibitor 8-oxo-GTP bound shows that the active site of GCYH-IB is larger and differently shaped. Based on this structural information, we designed and synthesized a small set of 8-oxo-G derivatives with ether linkages at O6 and O8 expected to displace water molecules from the expanded active site of GCYH-IB. The most potent of these compounds, G3, is selective for GCYH-IB, supporting the premise that potent and selective inhibitors of GCYH-IB could constitute a new class of small molecule antibiotics.
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Schüssler S, Haase I, Perbandt M, Illarionov B, Siemens A, Richter K, Bacher A, Fischer M, Gräwert T. Structure of GTP cyclohydrolase I from Listeria monocytogenes, a potential anti-infective drug target. ACTA CRYSTALLOGRAPHICA SECTION F-STRUCTURAL BIOLOGY COMMUNICATIONS 2019; 75:586-592. [PMID: 31475925 PMCID: PMC6718149 DOI: 10.1107/s2053230x19010902] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/15/2019] [Accepted: 08/04/2019] [Indexed: 12/03/2022]
Abstract
GTP cyclohydrolase I from Listeria monocytogenes, a putative anti-infective drug target, has been crystallized and the crystal structure was solved at 2.4 Å resolution. A putative open reading frame encoding GTP cyclohydrolase I from Listeria monocytogenes was expressed in a recombinant Escherichia coli strain. The recombinant protein was purified and was confirmed to convert GTP to dihydroneopterin triphosphate (Km = 53 µM; vmax = 180 nmol mg−1 min−1). The protein was crystallized from 1.3 M sodium citrate pH 7.3 and the crystal structure was solved at a resolution of 2.4 Å (Rfree = 0.226) by molecular replacement using human GTP cyclohydrolase I as a template. The protein is a D5-symmetric decamer with ten topologically equivalent active sites. Screening a small library of about 9000 compounds afforded several inhibitors with IC50 values in the low-micromolar range. Several inhibitors had significant selectivity with regard to human GTP cyclohydrolase I. Hence, GTP cyclohydrolase I may be a potential target for novel drugs directed at microbial infections, including listeriosis, a rare disease with high mortality.
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Affiliation(s)
- Sonja Schüssler
- Hamburg School of Food Science, Universität Hamburg, Grindelallee 117, 20146 Hamburg, Germany
| | - Ilka Haase
- Hamburg School of Food Science, Universität Hamburg, Grindelallee 117, 20146 Hamburg, Germany
| | - Markus Perbandt
- Institute for Biochemistry and Molecular Biology, Laboratory for Structural Biology of Infection and Inflammation, Universität Hamburg, Notkestrasse 85, 22607 Hamburg, Germany
| | - Boris Illarionov
- Hamburg School of Food Science, Universität Hamburg, Grindelallee 117, 20146 Hamburg, Germany
| | - Alexandra Siemens
- Hamburg School of Food Science, Universität Hamburg, Grindelallee 117, 20146 Hamburg, Germany
| | - Klaus Richter
- Department of Chemistry, Technical University of Munich, Lichtenbergstrasse 4, 85748 Garching, Germany
| | - Adelbert Bacher
- Hamburg School of Food Science, Universität Hamburg, Grindelallee 117, 20146 Hamburg, Germany
| | - Markus Fischer
- Hamburg School of Food Science, Universität Hamburg, Grindelallee 117, 20146 Hamburg, Germany
| | - Tobias Gräwert
- Hamburg School of Food Science, Universität Hamburg, Grindelallee 117, 20146 Hamburg, Germany
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10
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Chandrangsu P, Huang X, Gaballa A, Helmann JD. Bacillus subtilis FolE is sustained by the ZagA zinc metallochaperone and the alarmone ZTP under conditions of zinc deficiency. Mol Microbiol 2019; 112:751-765. [PMID: 31132310 DOI: 10.1111/mmi.14314] [Citation(s) in RCA: 45] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/22/2019] [Indexed: 12/23/2022]
Abstract
Bacteria tightly regulate intracellular zinc levels to ensure sufficient zinc to support essential functions, while preventing toxicity. The bacterial response to zinc limitation includes the expression of putative zinc metallochaperones belonging to subfamily 1 of the COG0523 family of G3E GTPases. However, the client proteins and the metabolic processes served by these chaperones are unclear. Here, we demonstrate that the Bacillus subtilis YciC zinc metallochaperone (here renamed ZagA for ZTP activated GTPase A) supports de novo folate biosynthesis under conditions of zinc limitation, and interacts directly with the zinc-dependent GTP cyclohydrolase IA, FolE (GCYH-IA). Furthermore, we identify a role for the alarmone ZTP, a modified purine biosynthesis intermediate, in the response to zinc limitation. ZTP, a signal of 10-formyl-tetrahydrofolate (10f-THF) deficiency in bacteria, transiently accumulates as FolE begins to fail, stimulates the interaction between ZagA and FolE, and thereby helps to sustain folate synthesis despite declining zinc availability.
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Affiliation(s)
- Pete Chandrangsu
- Department of Microbiology, Cornell University, Ithaca, NY, 14853, USA.,W.M. Keck Science Department, Claremont McKenna, Pitzer and Scripps College, Claremont, CA, 91711, USA
| | - Xiaojuan Huang
- Department of Microbiology, Cornell University, Ithaca, NY, 14853, USA
| | - Ahmed Gaballa
- Department of Microbiology, Cornell University, Ithaca, NY, 14853, USA
| | - John D Helmann
- Department of Microbiology, Cornell University, Ithaca, NY, 14853, USA
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11
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Folate biosynthesis pathway: mechanisms and insights into drug design for infectious diseases. Future Med Chem 2018; 10:935-959. [PMID: 29629843 DOI: 10.4155/fmc-2017-0168] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Folate pathway is a key target for the development of new drugs against infectious diseases since the discovery of sulfa drugs and trimethoprim. The knowledge about this pathway has increased in the last years and the catalytic mechanism and structures of all enzymes of the pathway are fairly understood. In addition, differences among enzymes from prokaryotes and eukaryotes could be used for the design of specific inhibitors. In this review, we show a panorama of progress that has been achieved within the folate pathway obtained in the last years. We explored the structure and mechanism of enzymes, several genetic features, strategies, and approaches used in the design of new inhibitors that have been used as targets in pathogen chemotherapy.
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12
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Abstract
Abstract
Pterins are widely conserved biomolecules that play essential roles in diverse organisms. First described as enzymatic cofactors in eukaryotic systems, bacterial pterins were discovered in cyanobacteria soon after. Several pterin structures unique to bacteria have been described, with conjugation to glycosides and nucleotides commonly observed. Despite this significant structural diversity, relatively few biological functions have been elucidated. Molybdopterin, the best studied bacterial pterin, plays an essential role in the function of the Moco cofactor. Moco is an essential component of molybdoenzymes such as sulfite oxidase, nitrate reductase, and dimethyl sulfoxide reductase, all of which play important roles in bacterial metabolism and global nutrient cycles. Outside of the molybdoenzymes, pterin cofactors play important roles in bacterial cyanide utilization and aromatic amino acid metabolism. Less is known about the roles of pterins in nonenzymatic processes. Cyanobacterial pterins have been implicated in phenotypes related to UV protection and phototaxis. Research describing the pterin-mediated control of cyclic nucleotide metabolism, and their influence on virulence and attachment, points to a possible role for pterins in regulation of bacterial behavior. In this review, we describe the variety of pterin functions in bacteria, compare and contrast structural and mechanistic differences, and illuminate promising avenues of future research.
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Affiliation(s)
- Nathan Feirer
- Department of Biology, Indiana University, Bloomington, IN 47405, USA
| | - Clay Fuqua
- Department of Biology, Indiana University, Bloomington, IN 47405, USA
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13
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Bon Ramos A, Bao L, Turner B, de Crécy-Lagard V, Iwata-Reuyl D. QueF-Like, a Non-Homologous Archaeosine Synthase from the Crenarchaeota. Biomolecules 2017; 7:biom7020036. [PMID: 28383498 PMCID: PMC5485725 DOI: 10.3390/biom7020036] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2017] [Revised: 03/23/2017] [Accepted: 03/24/2017] [Indexed: 12/17/2022] Open
Abstract
Archaeosine (G+) is a structurally complex modified nucleoside ubiquitous to the Archaea, where it is found in the D-loop of virtually all archaeal transfer RNA (tRNA). Its unique structure, which includes a formamidine group that carries a formal positive charge, and location in the tRNA, led to the proposal that it serves a key role in stabilizing tRNA structure. Although G+ is limited to the Archaea, it is structurally related to the bacterial modified nucleoside queuosine, and the two share homologous enzymes for the early steps of their biosynthesis. In the Euryarchaeota, the last step of the archaeosine biosynthetic pathway involves the amidation of a nitrile group on an archaeosine precursor to give formamidine, a reaction catalyzed by the enzyme Archaeosine Synthase (ArcS). Most Crenarchaeota lack ArcS, but possess two proteins that inversely distribute with ArcS and each other, and are implicated in G+ biosynthesis. Here, we describe biochemical studies of one of these, the protein QueF-like (QueF-L) from Pyrobaculum calidifontis, that demonstrate the catalytic activity of QueF-L, establish where in the pathway QueF-L acts, and identify the source of ammonia in the reaction.
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Affiliation(s)
- Adriana Bon Ramos
- Department of Chemistry, Portland State University, Portland, OR 97207, USA.
| | - Lide Bao
- Department of Chemistry, Portland State University, Portland, OR 97207, USA.
| | - Ben Turner
- Department of Chemistry, Portland State University, Portland, OR 97207, USA.
| | - Valérie de Crécy-Lagard
- The Department of Microbiology and Cell Science Department, University of Florida, Gainesville, FL 32611, USA.
| | - Dirk Iwata-Reuyl
- Department of Chemistry, Portland State University, Portland, OR 97207, USA.
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Mechanism and catalytic strategy of the prokaryotic-specific GTP cyclohydrolase-IB. Biochem J 2017; 474:1017-1039. [PMID: 28126741 DOI: 10.1042/bcj20161025] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2016] [Revised: 01/22/2017] [Accepted: 01/25/2017] [Indexed: 12/30/2022]
Abstract
Guanosine 5'-triphosphate (GTP) cyclohydrolase-I (GCYH-I) catalyzes the first step in folic acid biosynthesis in bacteria and plants, biopterin biosynthesis in mammals, and the biosynthesis of 7-deazaguanosine-modified tRNA nucleosides in bacteria and archaea. The type IB GCYH (GCYH-IB) is a prokaryotic-specific enzyme found in many pathogens. GCYH-IB is structurally distinct from the canonical type IA GCYH involved in biopterin biosynthesis in humans and animals, and thus is of interest as a potential antibacterial drug target. We report kinetic and inhibition data of Neisseria gonorrhoeae GCYH-IB and two high-resolution crystal structures of the enzyme; one in complex with the reaction intermediate analog and competitive inhibitor 8-oxoguanosine 5'-triphosphate (8-oxo-GTP), and one with a tris(hydroxymethyl)aminomethane molecule bound in the active site and mimicking another reaction intermediate. Comparison with the type IA enzyme bound to 8-oxo-GTP (guanosine 5'-triphosphate) reveals an inverted mode of binding of the inhibitor ribosyl moiety and, together with site-directed mutagenesis data, shows that the two enzymes utilize different strategies for catalysis. Notably, the inhibitor interacts with a conserved active-site Cys149, and this residue is S-nitrosylated in the structures. This is the first structural characterization of a biologically S-nitrosylated bacterial protein. Mutagenesis and biochemical analyses demonstrate that Cys149 is essential for the cyclohydrolase reaction, and S-nitrosylation maintains enzyme activity, suggesting a potential role of the S-nitrosothiol in catalysis.
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15
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Zallot R, Yuan Y, de Crécy-Lagard V. The Escherichia coli COG1738 Member YhhQ Is Involved in 7-Cyanodeazaguanine (preQ₀) Transport. Biomolecules 2017; 7:E12. [PMID: 28208705 PMCID: PMC5372724 DOI: 10.3390/biom7010012] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2016] [Revised: 01/27/2017] [Accepted: 01/30/2017] [Indexed: 11/17/2022] Open
Abstract
Queuosine (Q) is a complex modification of the wobble base in tRNAs with GUN anticodons. The full Q biosynthesis pathway has been elucidated in Escherichia coli. FolE, QueD, QueE and QueC are involved in the conversion of guanosine triphosphate (GTP) to 7-cyano-7-deazaguanine (preQ₀), an intermediate of increasing interest for its central role in tRNA and DNA modification and secondary metabolism. QueF then reduces preQ₀ to 7-aminomethyl-7-deazaguanine (preQ₁). PreQ₁ is inserted into tRNAs by tRNA guanine(34) transglycosylase (TGT). The inserted base preQ₁ is finally matured to Q by two additional steps involving QueA and QueG or QueH. Most Eubacteria harbor the full set of Q synthesis genes and are predicted to synthesize Q de novo. However, some bacteria only encode enzymes involved in the second half of the pathway downstream of preQ₀ synthesis, including the signature enzyme TGT. Different patterns of distribution of the queF, tgt, queA and queG or queH genes are observed, suggesting preQ₀, preQ₁ or even the queuine base being salvaged in specific organisms. Such salvage pathways require the existence of specific 7-deazapurine transporters that have yet to be identified. The COG1738 family was identified as a candidate for a missing preQ₀/preQ₁ transporter in prokaryotes, by comparative genomics analyses. The existence of Q precursor salvage was confirmed for the first time in bacteria, in vivo, through an indirect assay. The involvement of the COG1738 in salvage of a Q precursor was experimentally validated in Escherichia coli, where it was shown that the COG1738 family member YhhQ is essential for preQ₀ transport.
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Affiliation(s)
- Rémi Zallot
- Department of Microbiology and Cell Science, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL 32611, USA.
| | - Yifeng Yuan
- Department of Microbiology and Cell Science, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL 32611, USA.
| | - Valérie de Crécy-Lagard
- Department of Microbiology and Cell Science, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL 32611, USA.
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Hunter DJ, Torkelson JL, Bodnar J, Mortazavi B, Laurent T, Deason J, Thephavongsa K, Zhong J. The Rickettsia Endosymbiont of Ixodes pacificus Contains All the Genes of De Novo Folate Biosynthesis. PLoS One 2015; 10:e0144552. [PMID: 26650541 PMCID: PMC4674097 DOI: 10.1371/journal.pone.0144552] [Citation(s) in RCA: 82] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2015] [Accepted: 11/19/2015] [Indexed: 11/30/2022] Open
Abstract
Ticks and other arthropods often are hosts to nutrient providing bacterial endosymbionts, which contribute to their host’s fitness by supplying nutrients such as vitamins and amino acids. It has been detected, in our lab, that Ixodes pacificus is host to Rickettsia species phylotype G021. This endosymbiont is predominantly present, and 100% maternally transmitted in I. pacificus. To study roles of phylotype G021 in I. pacificus, bioinformatic and molecular approaches were carried out. MUMmer genome alignments of whole genome sequence of I. scapularis, a close relative to I. pacificus, against completely sequenced genomes of R. bellii OSU85-389, R. conorii, and R. felis, identified 8,190 unique sequences that are homologous to Rickettsia sequences in the NCBI Trace Archive. MetaCyc metabolic reconstructions revealed that all folate gene orthologues (folA, folC, folE, folKP, ptpS) required for de novo folate biosynthesis are present in the genome of Rickettsia buchneri in I. scapularis. To examine the metabolic capability of phylotype G021 in I. pacificus, genes of the folate biosynthesis pathway of the bacterium were PCR amplified using degenerate primers. BLAST searches identified that nucleotide sequences of the folA, folC, folE, folKP, and ptpS genes possess 98.6%, 98.8%, 98.9%, 98.5% and 99.0% identity respectively to the corresponding genes of Rickettsia buchneri. Phylogenetic tree constructions show that the folate genes of phylotype G021 and homologous genes from various Rickettsia species are monophyletic. This study has shown that all folate genes exist in the genome of Rickettsia species phylotype G021 and that this bacterium has the genetic capability for de novo folate synthesis.
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Affiliation(s)
- Daniel J. Hunter
- Department of Biological Sciences, Humboldt State University, Arcata, California, United States of America
| | - Jessica L. Torkelson
- Department of Biological Sciences, Humboldt State University, Arcata, California, United States of America
| | - James Bodnar
- Department of Biological Sciences, Humboldt State University, Arcata, California, United States of America
| | - Bobak Mortazavi
- Center for Outcomes Research and Evaluation, Yale School of Medicine, New Haven, Connecticut, United States of America
| | - Timothy Laurent
- Department of Biological Sciences, Humboldt State University, Arcata, California, United States of America
| | - Jeff Deason
- Department of Biological Sciences, Humboldt State University, Arcata, California, United States of America
| | - Khanhkeo Thephavongsa
- Department of Biological Sciences, Humboldt State University, Arcata, California, United States of America
| | - Jianmin Zhong
- Department of Biological Sciences, Humboldt State University, Arcata, California, United States of America
- * E-mail:
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17
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Adams NE, Thiaville JJ, Proestos J, Juárez-Vázquez AL, McCoy AJ, Barona-Gómez F, Iwata-Reuyl D, de Crécy-Lagard V, Maurelli AT. Promiscuous and adaptable enzymes fill "holes" in the tetrahydrofolate pathway in Chlamydia species. mBio 2014; 5:e01378-14. [PMID: 25006229 PMCID: PMC4161248 DOI: 10.1128/mbio.01378-14] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2014] [Accepted: 06/03/2014] [Indexed: 11/20/2022] Open
Abstract
Folates are tripartite molecules comprising pterin, para-aminobenzoate (PABA), and glutamate moieties, which are essential cofactors involved in DNA and amino acid synthesis. The obligately intracellular Chlamydia species have lost several biosynthetic pathways for essential nutrients which they can obtain from their host but have retained the capacity to synthesize folate. In most bacteria, synthesis of the pterin moiety of folate requires the FolEQBK enzymes, while synthesis of the PABA moiety is carried out by the PabABC enzymes. Bioinformatic analyses reveal that while members of Chlamydia are missing the genes for FolE (GTP cyclohydrolase) and FolQ, which catalyze the initial steps in de novo synthesis of the pterin moiety, they have genes for the rest of the pterin pathway. We screened a chlamydial genomic library in deletion mutants of Escherichia coli to identify the "missing genes" and identified a novel enzyme, TrpFCtL2, which has broad substrate specificity. TrpFCtL2, in combination with GTP cyclohydrolase II (RibA), the first enzyme of riboflavin synthesis, provides a bypass of the first two canonical steps in folate synthesis catalyzed by FolE and FolQ. Notably, TrpFCtL2 retains the phosphoribosyl anthranilate isomerase activity of the original annotation. Additionally, we independently confirmed the recent discovery of a novel enzyme, CT610, which uses an unknown precursor to synthesize PABA and complements E. coli mutants with deletions of pabA, pabB, or pabC. Thus, Chlamydia species have evolved a variant folate synthesis pathway that employs a patchwork of promiscuous and adaptable enzymes recruited from other biosynthetic pathways. Importance: Collectively, the involvement of TrpFCtL2 and CT610 in the tetrahydrofolate pathway completes our understanding of folate biosynthesis in Chlamydia. Moreover, the novel roles for TrpFCtL2 and CT610 in the tetrahydrofolate pathway are sophisticated examples of how enzyme evolution plays a vital role in the adaptation of obligately intracellular organisms to host-specific niches. Enzymes like TrpFCtL2 which possess an enzyme fold common to many other enzymes are highly versatile and possess the capacity to evolve to catalyze related reactions in two different metabolic pathways. The continued identification of unique enzymes such as these in bacterial pathogens is important for development of antimicrobial compounds, as drugs that inhibit such enzymes would likely not have any targets in the host or the host's normal microbial flora.
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Affiliation(s)
- Nancy E Adams
- Department of Microbiology and Immunology, F. Edward Hébert School of Medicine, Uniformed Services University, Bethesda, Maryland, USA
| | - Jennifer J Thiaville
- Department of Microbiology and Cell Science, University of Florida, Gainesville, Florida, USA
| | - James Proestos
- Department of Chemistry, Portland State University, Portland, Oregon, USA
| | - Ana L Juárez-Vázquez
- Evolution of Metabolic Diversity Laboratory, Laboratorio Nacional de Genómica para la Biodiversidad (Langebio), Cinvestav-IPN, Irapuato, Mexico
| | - Andrea J McCoy
- Department of Microbiology and Immunology, F. Edward Hébert School of Medicine, Uniformed Services University, Bethesda, Maryland, USA
| | - Francisco Barona-Gómez
- Evolution of Metabolic Diversity Laboratory, Laboratorio Nacional de Genómica para la Biodiversidad (Langebio), Cinvestav-IPN, Irapuato, Mexico
| | - Dirk Iwata-Reuyl
- Department of Chemistry, Portland State University, Portland, Oregon, USA
| | - Valérie de Crécy-Lagard
- Department of Microbiology and Cell Science, University of Florida, Gainesville, Florida, USA
| | - Anthony T Maurelli
- Department of Microbiology and Immunology, F. Edward Hébert School of Medicine, Uniformed Services University, Bethesda, Maryland, USA
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18
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El Yacoubi B, de Crécy-Lagard V. Integrative data-mining tools to link gene and function. Methods Mol Biol 2014; 1101:43-66. [PMID: 24233777 DOI: 10.1007/978-1-62703-721-1_4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/10/2023]
Abstract
Information derived from genomic and post-genomic data can be efficiently used to link gene and function. Several web-based platforms have been developed to mine these types of data by integrating different tools. This method paper is designed to allow the user to navigate these platforms in order to make functional predictions. The main focus is on phylogenetic distribution and physical clustering tools, but other tools such as pathway reconstruction, gene fusions, and analysis of high-throughput experimental data are also surveyed.
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Affiliation(s)
- Basma El Yacoubi
- Department of Microbiology and Cell Science, University of Florida, Gainesville, FL, USA
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19
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de Crécy-Lagard V. Variations in metabolic pathways create challenges for automated metabolic reconstructions: Examples from the tetrahydrofolate synthesis pathway. Comput Struct Biotechnol J 2014; 10:41-50. [PMID: 25210598 PMCID: PMC4151868 DOI: 10.1016/j.csbj.2014.05.008] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
The availability of thousands of sequenced genomes has revealed the diversity of biochemical solutions to similar chemical problems. Even for molecules at the heart of metabolism, such as cofactors, the pathway enzymes first discovered in model organisms like Escherichia coli or Saccharomyces cerevisiae are often not universally conserved. Tetrahydrofolate (THF) (or its close relative tetrahydromethanopterin) is a universal and essential C1-carrier that most microbes and plants synthesize de novo. The THF biosynthesis pathway and enzymes are, however, not universal and alternate solutions are found for most steps, making this pathway a challenge to annotate automatically in many genomes. Comparing THF pathway reconstructions and functional annotations of a chosen set of folate synthesis genes in specific prokaryotes revealed the strengths and weaknesses of different microbial annotation platforms. This analysis revealed that most current platforms fail in metabolic reconstruction of variant pathways. However, all the pieces are in place to quickly correct these deficiencies if the different databases were built on each other's strengths.
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Affiliation(s)
- Valérie de Crécy-Lagard
- Department of Microbiology and Cell Science and Genetics Institute, University of Florida, Gainesville, FL, United States
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20
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Björk GR, Hagervall TG. Transfer RNA Modification: Presence, Synthesis, and Function. EcoSal Plus 2014; 6. [PMID: 26442937 DOI: 10.1128/ecosalplus.esp-0007-2013] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2014] [Indexed: 06/05/2023]
Abstract
Transfer RNA (tRNA) from all organisms on this planet contains modified nucleosides, which are derivatives of the four major nucleosides. tRNA from Escherichia coli/Salmonella enterica serovar Typhimurium contains 33 different modified nucleosides, which are all, except one (Queuosine [Q]), synthesized on an oligonucleotide precursor, which by specific enzymes later matures into tRNA. The structural genes for these enzymes are found in mono- and polycistronic operons, the latter of which have a complex transcription and translation pattern. The synthesis of the tRNA-modifying enzymes is not regulated similarly, and it is not coordinated to that of their substrate, the tRNA. The synthesis of some of them (e.g., several methylated derivatives) is catalyzed by one enzyme, which is position and base specific, whereas synthesis of some has a very complex biosynthetic pathway involving several enzymes (e.g., 2-thiouridines, N 6-cyclicthreonyladenosine [ct6A], and Q). Several of the modified nucleosides are essential for viability (e.g., lysidin, ct6A, 1-methylguanosine), whereas the deficiency of others induces severe growth defects. However, some have no or only a small effect on growth at laboratory conditions. Modified nucleosides that are present in the anticodon loop or stem have a fundamental influence on the efficiency of charging the tRNA, reading cognate codons, and preventing missense and frameshift errors. Those that are present in the body of the tRNA primarily have a stabilizing effect on the tRNA. Thus, the ubiquitous presence of these modified nucleosides plays a pivotal role in the function of the tRNA by their influence on the stability and activity of the tRNA.
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Affiliation(s)
- Glenn R Björk
- Department of Molecular Biology, Umeå University, S-90187 Umeå, Sweden
| | - Tord G Hagervall
- Department of Molecular Biology, Umeå University, S-90187 Umeå, Sweden
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21
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Sousa FL, Martin WF. Biochemical fossils of the ancient transition from geoenergetics to bioenergetics in prokaryotic one carbon compound metabolism. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2014; 1837:964-81. [PMID: 24513196 DOI: 10.1016/j.bbabio.2014.02.001] [Citation(s) in RCA: 64] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 10/26/2013] [Revised: 01/31/2014] [Accepted: 02/03/2014] [Indexed: 12/27/2022]
Abstract
The deep dichotomy of archaea and bacteria is evident in many basic traits including ribosomal protein composition, membrane lipid synthesis, cell wall constituents, and flagellar composition. Here we explore that deep dichotomy further by examining the distribution of genes for the synthesis of the central carriers of one carbon units, tetrahydrofolate (H4F) and tetrahydromethanopterin (H4MPT), in bacteria and archaea. The enzymes underlying those distinct biosynthetic routes are broadly unrelated across the bacterial-archaeal divide, indicating that the corresponding pathways arose independently. That deep divergence in one carbon metabolism is mirrored in the structurally unrelated enzymes and different organic cofactors that methanogens (archaea) and acetogens (bacteria) use to perform methyl synthesis in their H4F- and H4MPT-dependent versions, respectively, of the acetyl-CoA pathway. By contrast, acetyl synthesis in the acetyl-CoA pathway - from a methyl group, CO2 and reduced ferredoxin - is simpler, uniform and conserved across acetogens and methanogens, and involves only transition metals as catalysts. The data suggest that the acetyl-CoA pathway, while being the most ancient of known CO2 assimilation pathways, reflects two phases in early evolution: an ancient phase in a geochemically confined and non-free-living universal common ancestor, in which acetyl thioester synthesis proceeded spontaneously with the help of geochemically supplied methyl groups, and a later phase that reflects the primordial divergence of the bacterial and archaeal stem groups, which independently invented genetically-encoded means to synthesize methyl groups via enzymatic reactions. This article is part of a Special Issue entitled: 18th European Bioenergetic Conference.
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Affiliation(s)
- Filipa L Sousa
- Institute for Molecular Evolution,University of Düsseldorf, 40225 Düsseldorf, Germany
| | - William F Martin
- Institute for Molecular Evolution,University of Düsseldorf, 40225 Düsseldorf, Germany.
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22
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Utility of the Biosynthetic Folate Pathway for Targets in Antimicrobial Discovery. Antibiotics (Basel) 2014; 3:1-28. [PMID: 27025730 PMCID: PMC4790348 DOI: 10.3390/antibiotics3010001] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2013] [Revised: 01/08/2014] [Accepted: 01/09/2014] [Indexed: 01/07/2023] Open
Abstract
The need for new antimicrobials is great in face of a growing pool of resistant pathogenic organisms. This review will address the potential for antimicrobial therapy based on polypharmacological activities within the currently utilized bacterial biosynthetic folate pathway. The folate metabolic pathway leads to synthesis of required precursors for cellular function and contains a critical node, dihydrofolate reductase (DHFR), which is shared between prokaryotes and eukaryotes. The DHFR enzyme is currently targeted by methotrexate in anti-cancer therapies, by trimethoprim for antibacterial uses, and by pyrimethamine for anti-protozoal applications. An additional anti-folate target is dihyropteroate synthase (DHPS), which is unique to prokaryotes as they cannot acquire folate through dietary means. It has been demonstrated as a primary target for the longest standing antibiotic class, the sulfonamides, which act synergistically with DHFR inhibitors. Investigations have revealed most DHPS enzymes possess the ability to utilize sulfa drugs metabolically, producing alternate products that presumably inhibit downstream enzymes requiring the produced dihydropteroate. Recent work has established an off-target effect of sulfonamide antibiotics on a eukaryotic enzyme, sepiapterin reductase, causing alterations in neurotransmitter synthesis. Given that inhibitors of both DHFR and DHPS are designed to mimic their cognate substrate, which contain shared substructures, it is reasonable to expect such “off-target” effects. These inhibitors are also likely to interact with the enzymatic neighbors in the folate pathway that bind products of the DHFR or DHPS enzymes and/or substrates of similar substructure. Computational studies designed to assess polypharmacology reiterate these conclusions. This leads to hypotheses exploring the vast utility of multiple members of the folate pathway for modulating cellular metabolism, and includes an appealing capacity for prokaryotic-specific polypharmacology for antimicrobial applications.
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23
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Identification of Salmonella enterica serovar Pullorum antigenic determinants expressed in vivo. Infect Immun 2013; 81:3119-27. [PMID: 23774596 DOI: 10.1128/iai.00145-13] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Salmonella enterica serovar Pullorum affecting poultry causes pullorum disease and results in severe economic loss in the poultry industry. Currently, it remains a major threat in countries with poor poultry surveillance and no efficient control measures. As S. Pullorum could induce strong humoral immune responses, we applied an immunoscreening technique, the in vivo-induced antigen technology (IVIAT), to identify immunogenic bacterial proteins expressed or upregulated during S. Pullorum infection. Convalescent-phase sera from chickens infected with S. Pullorum were pooled, adsorbed against antigens expressed in vitro, and used to screen an S. Pullorum genomic expression library. Forty-five proteins were screened out, and their functions were implicated in molecular biosynthesis and degradation, transport, metabolism, regulation, cell wall synthesis and antibiotic resistance, environmental adaptation, or putative functions. In addition, 11 of these 45 genes were assessed for their differential expression by quantitative real-time reverse transcription-PCR (RT-PCR), revealing that 9 of 11 genes were upregulated to different degrees under in vivo conditions, especially the regulator of virulence determinants, phoQ. Then, four in vivo-induced proteins (ShdA, PhoQ, Cse3, and PbpC) were tested for their immunoreactivity in 28 clinical serum samples from chickens infected with S. Pullorum. The rate of detection of antibodies against ShdA reached 82% and was the highest among these proteins. ShdA is a host colonization factor known to be upregulated in vivo and related to the persistence of S. Typhimurium in the intestine. Furthermore, these antigens identified by IVIAT warrant further evaluation for their contributions to pathogenesis, and more potential roles, such as diagnostic, therapeutic, and preventive uses, need to be developed in future studies.
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Gräwert T, Fischer M, Bacher A. Structures and reaction mechanisms of GTP cyclohydrolases. IUBMB Life 2013; 65:310-22. [PMID: 23457054 DOI: 10.1002/iub.1153] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2013] [Accepted: 01/25/2013] [Indexed: 11/09/2022]
Abstract
GTP cyclohydrolases generate the first committed intermediates for the biosynthesis of certain vitamins/cofactors (folic acid, riboflavin, deazaflavin, and tetrahydrobiopterin), deazapurine antibiotics, some t-RNA bases (queuosine, archaeosine), and the phytotoxin, toxoflavin. They depend on divalent cations for hydrolytic opening of the imidazole ring of the substrate, guanosine triphosphate (GTP). Surprisingly, the ring opening reaction is not the rate-limiting step for GTP cyclohydrolases I and II whose mechanism have been studied in some detail. GTP cyclohydrolase I, Ib, and II are potential targets for novel anti-infectives. Genetic factors modulating the activity of human GTP cyclohydrolase are highly pleiotropic, since the signal transponders whose biosyntheses require their participation (nitric oxide, catecholamines) impact a very wide range of physiological phenomena. Recent studies suggest that human GTP cyclohydrolase may become an oncology target.
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Affiliation(s)
- Tobias Gräwert
- Hamburg School of Food Science, Institut für Lebensmittelchemie, Grindelallee 117, 20146 Hamburg, Germany
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25
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Crécy-Lagard VD, Phillips G, Grochowski LL, Yacoubi BE, Jenney F, Adams MWW, Murzin AG, White RH. Comparative genomics guided discovery of two missing archaeal enzyme families involved in the biosynthesis of the pterin moiety of tetrahydromethanopterin and tetrahydrofolate. ACS Chem Biol 2012; 7:1807-16. [PMID: 22931285 PMCID: PMC3500442 DOI: 10.1021/cb300342u] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
![]()
C-1 carriers are essential cofactors in all domains of
life, and
in Archaea, these can be derivatives of tetrahydromethanopterin (H4-MPT) or tetrahydrofolate (H4-folate). Their synthesis
requires 6-hydroxymethyl-7,8-dihydropterin diphosphate (6-HMDP) as
the precursor, but the nature of pathways that lead to its formation
were unknown until the recent discovery of the GTP cyclohydrolase
IB/MptA family that catalyzes the first step, the conversion of GTP
to dihydroneopterin 2′,3′-cyclic phosphate or 7,8-dihydroneopterin
triphosphate [El Yacoubi, B.; et al. (2006) J. Biol. Chem., 281, 37586–37593
and Grochowski, L. L.; et al. (2007) Biochemistry46, 6658–6667]. Using a combination of comparative
genomics analyses, heterologous complementation tests, and in vitro assays, we show that the archaeal protein families
COG2098 and COG1634 specify two of the missing 6-HMDP synthesis enzymes.
Members of the COG2098 family catalyze the formation of 6-hydroxymethyl-7,8-dihydropterin
from 7,8-dihydroneopterin, while members of the COG1634 family catalyze
the formation of 6-HMDP from 6-hydroxymethyl-7,8-dihydropterin. The
discovery of these missing genes solves a long-standing mystery and
provides novel examples of convergent evolutions where proteins of
dissimilar architectures perform the same biochemical function.
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Affiliation(s)
- Valérie de Crécy-Lagard
- Department of Microbiology and
Department of Microbiology and Cell Science, University of Florida, P.O. Box 110700, Gainesville, Florida 32611-0700,
United States
| | - Gabriela Phillips
- Department of Microbiology and
Department of Microbiology and Cell Science, University of Florida, P.O. Box 110700, Gainesville, Florida 32611-0700,
United States
| | - Laura L. Grochowski
- Department
of Biochemistry (0308), Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061, United
States
| | - Basma El Yacoubi
- Department of Microbiology and
Department of Microbiology and Cell Science, University of Florida, P.O. Box 110700, Gainesville, Florida 32611-0700,
United States
| | - Francis Jenney
- Department of Basic
Sciences,
Georgia Campus, Philadelphia College of Osteopathic Medicine, Suwanee, Georgia 30024, United States
| | - Michael W. W. Adams
- Department of Biochemistry and
Molecular Biology, University of Georgia, Athens, Georgia 30602, United States
| | - Alexey G. Murzin
- MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 0QH,
U.K
| | - Robert H. White
- Department
of Biochemistry (0308), Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061, United
States
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Braakman R, Smith E. The emergence and early evolution of biological carbon-fixation. PLoS Comput Biol 2012; 8:e1002455. [PMID: 22536150 PMCID: PMC3334880 DOI: 10.1371/journal.pcbi.1002455] [Citation(s) in RCA: 119] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2011] [Accepted: 02/13/2012] [Indexed: 11/18/2022] Open
Abstract
The fixation of CO₂ into living matter sustains all life on Earth, and embeds the biosphere within geochemistry. The six known chemical pathways used by extant organisms for this function are recognized to have overlaps, but their evolution is incompletely understood. Here we reconstruct the complete early evolutionary history of biological carbon-fixation, relating all modern pathways to a single ancestral form. We find that innovations in carbon-fixation were the foundation for most major early divergences in the tree of life. These findings are based on a novel method that fully integrates metabolic and phylogenetic constraints. Comparing gene-profiles across the metabolic cores of deep-branching organisms and requiring that they are capable of synthesizing all their biomass components leads to the surprising conclusion that the most common form for deep-branching autotrophic carbon-fixation combines two disconnected sub-networks, each supplying carbon to distinct biomass components. One of these is a linear folate-based pathway of CO₂ reduction previously only recognized as a fixation route in the complete Wood-Ljungdahl pathway, but which more generally may exclude the final step of synthesizing acetyl-CoA. Using metabolic constraints we then reconstruct a "phylometabolic" tree with a high degree of parsimony that traces the evolution of complete carbon-fixation pathways, and has a clear structure down to the root. This tree requires few instances of lateral gene transfer or convergence, and instead suggests a simple evolutionary dynamic in which all divergences have primary environmental causes. Energy optimization and oxygen toxicity are the two strongest forces of selection. The root of this tree combines the reductive citric acid cycle and the Wood-Ljungdahl pathway into a single connected network. This linked network lacks the selective optimization of modern fixation pathways but its redundancy leads to a more robust topology, making it more plausible than any modern pathway as a primitive universal ancestral form.
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Affiliation(s)
- Rogier Braakman
- Santa Fe Institute, Santa Fe, New Mexico, United States of America
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Characterization of the response to zinc deficiency in the cyanobacterium Anabaena sp. strain PCC 7120. J Bacteriol 2012; 194:2426-36. [PMID: 22389488 DOI: 10.1128/jb.00090-12] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Zur regulators control zinc homeostasis by repressing target genes under zinc-sufficient conditions in a wide variety of bacteria. This paper describes how part of a survey of duplicated genes led to the identification of the open reading frame all2473 as the gene encoding the Zur regulator of the cyanobacterium Anabaena sp. strain PCC 7120. All2473 binds to DNA in a zinc-dependent manner, and its DNA-binding sequence was characterized, which allowed us to determine the relative contribution of particular nucleotides to Zur binding. A zur mutant was found to be impaired in the regulation of zinc homeostasis, showing sensitivity to elevated concentrations of zinc but not other metals. In an effort to characterize the Zur regulon in Anabaena, 23 genes containing upstream putative Zur-binding sequences were identified and found to be regulated by Zur. These genes are organized in six single transcriptional units and six operons, some of them containing multiple Zur-regulated promoters. The identities of genes of the Zur regulon indicate that Anabaena adapts to conditions of zinc deficiency by replacing zinc metalloproteins with paralogues that fulfill the same function but presumably with a lower zinc demand, and with inducing putative metallochaperones and membrane transport systems likely being involved in the scavenging of extracellular zinc, including plasma membrane ABC transport systems and outer membrane TonB-dependent receptors. Among the Zur-regulated genes, the ones showing the highest induction level encode proteins of the outer membrane, suggesting a primary role for components of this cell compartment in the capture of zinc cations from the extracellular medium.
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Phillips G, Grochowski LL, Bonnett S, Xu H, Bailly M, Haas-Blaby C, El Yacoubi B, Iwata-Reuyl D, White RH, de Crécy-Lagard V. Functional promiscuity of the COG0720 family. ACS Chem Biol 2012; 7:197-209. [PMID: 21999246 PMCID: PMC3262898 DOI: 10.1021/cb200329f] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The biosynthesis of GTP derived metabolites such as tetrahydrofolate (THF), biopterin (BH(4)), and the modified tRNA nucleosides queuosine (Q) and archaeosine (G(+)) relies on several enzymes of the Tunnel-fold superfamily. A subset of these proteins includes the 6-pyruvoyltetrahydropterin (PTPS-II), PTPS-III, and PTPS-I homologues, all members of the COG0720 family that have been previously shown to transform 7,8-dihydroneopterin triphosphate (H(2)NTP) into different products. PTPS-II catalyzes the formation of 6-pyruvoyltetrahydropterin in the BH(4) pathway, PTPS-III catalyzes the formation of 6-hydroxylmethyl-7,8-dihydropterin in the THF pathway, and PTPS-I catalyzes the formation of 6-carboxy-5,6,7,8-tetrahydropterin in the Q pathway. Genes of these three enzyme families are often misannotated as they are difficult to differentiate by sequence similarity alone. Using a combination of physical clustering, signature motif, phylogenetic codistribution analyses, in vivo complementation studies, and in vitro enzymatic assays, a complete reannotation of the COG0720 family was performed in prokaryotes. Notably, this work identified and experimentally validated dual function PTPS-I/III enzymes involved in both THF and Q biosynthesis. Both in vivo and in vitro analyses showed that the PTPS-I family could tolerate a translation of the active site cysteine and was inherently promiscuous, catalyzing different reactions on the same substrate or the same reaction on different substrates. Finally, the analysis and experimental validation of several archaeal COG0720 members confirmed the role of PTPS-I in archaeosine biosynthesis and resulted in the identification of PTPS-III enzymes with variant signature sequences in Sulfolobus species. This study reveals an expanded versatility of the COG0720 family members and illustrates that for certain protein families extensive comparative genomic analysis beyond homology is required to correctly predict function.
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Affiliation(s)
- Gabriela Phillips
- Department of Microbiology and Department of Microbiology and Cell Science, University of Florida, Gainesville, FL 32611
| | - Laura L. Grochowski
- Department of Biochemistry, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061
| | - Shilah Bonnett
- Department of Chemistry, Portland State University, Portland, OR 97207
| | - Huimin Xu
- Department of Biochemistry, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061
| | - Marc Bailly
- Department of Microbiology and Department of Microbiology and Cell Science, University of Florida, Gainesville, FL 32611
| | - Crysten Haas-Blaby
- Department of Microbiology and Department of Microbiology and Cell Science, University of Florida, Gainesville, FL 32611
| | - Basma El Yacoubi
- Department of Microbiology and Department of Microbiology and Cell Science, University of Florida, Gainesville, FL 32611
| | - Dirk Iwata-Reuyl
- Department of Chemistry, Portland State University, Portland, OR 97207
| | - Robert H. White
- Department of Biochemistry, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061
| | - Valérie de Crécy-Lagard
- Department of Microbiology and Department of Microbiology and Cell Science, University of Florida, Gainesville, FL 32611
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Merchant SS, Helmann JD. Elemental economy: microbial strategies for optimizing growth in the face of nutrient limitation. Adv Microb Physiol 2012; 60:91-210. [PMID: 22633059 PMCID: PMC4100946 DOI: 10.1016/b978-0-12-398264-3.00002-4] [Citation(s) in RCA: 123] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Microorganisms play a dominant role in the biogeochemical cycling of nutrients. They are rightly praised for their facility for fixing both carbon and nitrogen into organic matter, and microbial driven processes have tangibly altered the chemical composition of the biosphere and its surrounding atmosphere. Despite their prodigious capacity for molecular transformations, microorganisms are powerless in the face of the immutability of the elements. Limitations for specific elements, either fleeting or persisting over eons, have left an indelible trace on microbial genomes, physiology, and their very atomic composition. We here review the impact of elemental limitation on microbes, with a focus on selected genetic model systems and representative microbes from the ocean ecosystem. Evolutionary adaptations that enhance growth in the face of persistent or recurrent elemental limitations are evident from genome and proteome analyses. These range from the extreme (such as dispensing with a requirement for a hard to obtain element) to the extremely subtle (changes in protein amino acid sequences that slightly, but significantly, reduce cellular carbon, nitrogen, or sulfur demand). One near-universal adaptation is the development of sophisticated acclimation programs by which cells adjust their chemical composition in response to a changing environment. When specific elements become limiting, acclimation typically begins with an increased commitment to acquisition and a concomitant mobilization of stored resources. If elemental limitation persists, the cell implements austerity measures including elemental sparing and elemental recycling. Insights into these fundamental cellular properties have emerged from studies at many different levels, including ecology, biological oceanography, biogeochemistry, molecular genetics, genomics, and microbial physiology. Here, we present a synthesis of these diverse studies and attempt to discern some overarching themes.
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Affiliation(s)
- Sabeeha S. Merchant
- Institute for Genomics and Proteomics and Department of Chemistry and Biochemistry, University of California, Los Angeles, CA 90095
| | - John D. Helmann
- Department of Microbiology, Cornell University, Ithaca, NY, 14853-8101
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Singh S, Joshi P, Chopade BA. Pathway Analysis of Acinetobacter baylyi: A Combined Bioinformatic and Genomics Approach. Chem Biol Drug Des 2011; 78:893-905. [DOI: 10.1111/j.1747-0285.2011.01191.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Hanson AD, Gregory JF. Folate biosynthesis, turnover, and transport in plants. ANNUAL REVIEW OF PLANT BIOLOGY 2011; 62:105-25. [PMID: 21275646 DOI: 10.1146/annurev-arplant-042110-103819] [Citation(s) in RCA: 145] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
Folates are essential cofactors for one-carbon transfer reactions and are needed in the diets of humans and animals. Because plants are major sources of dietary folate, plant folate biochemistry has long been of interest but progressed slowly until the genome era. Since then, genome-enabled approaches have brought rapid advances: We now know (a) all the plant folate synthesis genes and some genes of folate turnover and transport, (b) certain mechanisms governing folate synthesis, and (c) the subcellular locations of folate synthesis enzymes and of folates themselves. Some of this knowledge has been applied, simply and successfully, to engineer folate-enriched food crops (i.e., biofortification). Much remains to be discovered about folates, however, particularly in relation to homeostasis, catabolism, membrane transport, and vacuolar storage. Understanding these processes, which will require both biochemical and -omics research, should lead to improved biofortification strategies based on transgenic or conventional approaches.
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Affiliation(s)
- Andrew D Hanson
- Horticultural Sciences Department, University of Florida, Gainesville, Florida 32611, USA
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Molecular characterization of beta-lactamase genes and their genetic structures in Acinetobacter genospecies 3 isolates in Taiwan. Antimicrob Agents Chemother 2010; 54:2699-703. [PMID: 20368407 DOI: 10.1128/aac.01624-09] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
The genetic structure of beta-lactamases in Acinetobacter genospecies 3 (AG3) isolates in Taiwan was studied to analyze their high rates of resistance to beta-lactams, including carbapenems (57.9%). bla(IMP-1) and bla(IMP-8) were located in a class 1 integron. bla(OXA-58) was bracketed by ISAba3. A novel TnpF-like integrase gene was identified upstream of bla(VEB-3). Adjacent to the 5' sequence of the bla(ADC) gene, folE was identified. Four new Acinetobacter-derived cephalosporinase (ADC) enzymes were found, which clustered phylogenetically with published AG3 ADC proteins.
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33
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A systematic survey of in vivo obligate chaperonin-dependent substrates. EMBO J 2010; 29:1552-64. [PMID: 20360681 DOI: 10.1038/emboj.2010.52] [Citation(s) in RCA: 134] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2009] [Accepted: 03/08/2010] [Indexed: 01/17/2023] Open
Abstract
Chaperonins are absolutely required for the folding of a subset of proteins in the cell. An earlier proteome-wide analysis of Escherichia coli chaperonin GroEL/GroES (GroE) interactors predicted obligate chaperonin substrates, which were termed Class III substrates. However, the requirement of chaperonins for in vivo folding has not been fully examined. Here, we comprehensively assessed the chaperonin requirement using a conditional GroE expression strain, and concluded that only approximately 60% of Class III substrates are bona fide obligate GroE substrates in vivo. The in vivo obligate substrates, combined with the newly identified obligate substrates, were termed Class IV substrates. Class IV substrates are restricted to proteins with molecular weights that could be encapsulated in the chaperonin cavity, are enriched in alanine/glycine residues, and have a strong structural preference for aggregation-prone folds. Notably, approximately 70% of the Class IV substrates appear to be metabolic enzymes, supporting a hypothetical role of GroE in enzyme evolution.
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Mashhadi Z, Xu H, White RH. An Fe2+-dependent cyclic phosphodiesterase catalyzes the hydrolysis of 7,8-dihydro-D-neopterin 2',3'-cyclic phosphate in methanopterin biosynthesis. Biochemistry 2009; 48:9384-92. [PMID: 19746965 DOI: 10.1021/bi9010336] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
7,8-Dihydro-D-neopterin 2',3'-cyclic phosphate (H(2)N-cP) is the first intermediate in biosynthesis of the pterin portion of tetrahydromethanopterin (H(4)MPT), a C(1) carrier coenzyme first identified in the methanogenic archaea. This intermediate is produced from GTP by MptA (MJ0775 gene product), a new class of GTP cyclohydrolase I [Grochowski, L. L., Xu, H., Leung, K., and White, R. H. (2007) Biochemistry 46, 6658-6667]. Here we report the identification of a cyclic phosphodiesterase that hydrolyzes the cyclic phosphate of H(2)N-cP and converts it to a mixture of 7,8-dihydro-D-neopterin 2'-monophosphate and 7,8-dihydro-d-neopterin 3'-monophosphate. The enzyme from Methanocaldococcus jannachii is designated MptB (MJ0837 gene product) to indicate that it catalyzes the second step of the biosynthesis of methanopterin. MptB is a member of the HD domain superfamily of enzymes, which require divalent metals for activity. Direct metal analysis of the recombinant enzyme demonstrated that MptB contained 1.0 mol of zinc and 0.8 mol of iron per protomer. MptB requires Fe(2+) for activity, the same as observed for MptA. Thus the first two enzymes involved in H(4)MPT biosynthesis in the archaea are Fe(2+) dependent.
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Affiliation(s)
- Zahra Mashhadi
- Department of Biochemistry (0308), Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061, USA
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Zinc-independent folate biosynthesis: genetic, biochemical, and structural investigations reveal new metal dependence for GTP cyclohydrolase IB. J Bacteriol 2009; 191:6936-49. [PMID: 19767425 PMCID: PMC2772490 DOI: 10.1128/jb.00287-09] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
GTP cyclohydrolase I (GCYH-I) is an essential Zn(2+)-dependent enzyme that catalyzes the first step of the de novo folate biosynthetic pathway in bacteria and plants, the 7-deazapurine biosynthetic pathway in Bacteria and Archaea, and the biopterin pathway in mammals. We recently reported the discovery of a new prokaryotic-specific GCYH-I (GCYH-IB) that displays no sequence identity to the canonical enzyme and is present in approximately 25% of bacteria, the majority of which lack the canonical GCYH-I (renamed GCYH-IA). Genomic and genetic analyses indicate that in those organisms possessing both enzymes, e.g., Bacillus subtilis, GCYH-IA and -IB are functionally redundant, but differentially expressed. Whereas GCYH-IA is constitutively expressed, GCYH-IB is expressed only under Zn(2+)-limiting conditions. These observations are consistent with the hypothesis that GCYH-IB functions to allow folate biosynthesis during Zn(2+) starvation. Here, we present biochemical and structural data showing that bacterial GCYH-IB, like GCYH-IA, belongs to the tunneling-fold (T-fold) superfamily. However, the GCYH-IA and -IB enzymes exhibit significant differences in global structure and active-site architecture. While GCYH-IA is a unimodular, homodecameric, Zn(2+)-dependent enzyme, GCYH-IB is a bimodular, homotetrameric enzyme activated by a variety of divalent cations. The structure of GCYH-IB and the broad metal dependence exhibited by this enzyme further underscore the mechanistic plasticity that is emerging for the T-fold superfamily. Notably, while humans possess the canonical GCYH-IA enzyme, many clinically important human pathogens possess only the GCYH-IB enzyme, suggesting that this enzyme is a potential new molecular target for antibacterial development.
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Pribat A, Jeanguenin L, Lara-Núñez A, Ziemak MJ, Hyde JE, de Crécy-Lagard V, Hanson AD. 6-pyruvoyltetrahydropterin synthase paralogs replace the folate synthesis enzyme dihydroneopterin aldolase in diverse bacteria. J Bacteriol 2009; 191:4158-65. [PMID: 19395485 PMCID: PMC2698474 DOI: 10.1128/jb.00416-09] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2009] [Accepted: 04/19/2009] [Indexed: 01/15/2023] Open
Abstract
Dihydroneopterin aldolase (FolB) catalyzes conversion of dihydroneopterin to 6-hydroxymethyldihydropterin (HMDHP) in the classical folate biosynthesis pathway. However, folB genes are missing from the genomes of certain bacteria from the phyla Chloroflexi, Acidobacteria, Firmicutes, Planctomycetes, and Spirochaetes. Almost all of these folB-deficient genomes contain an unusual paralog of the tetrahydrobiopterin synthesis enzyme 6-pyruvoyltetrahydropterin synthase (PTPS) in which a glutamate residue replaces or accompanies the catalytic cysteine. A similar PTPS paralog from the malaria parasite Plasmodium falciparum is known to form HMDHP from dihydroneopterin triphosphate in vitro and has been proposed to provide a bypass to the FolB step in vivo. Bacterial genes encoding PTPS-like proteins with active-site glutamate, cysteine, or both residues were accordingly tested together with the P. falciparum gene for complementation of the Escherichia coli folB mutation. The P. falciparum sequence and bacterial sequences with glutamate or glutamate plus cysteine were active; those with cysteine alone were not. These results demonstrate that PTPS paralogs with an active-site glutamate (designated PTPS-III proteins) can functionally replace FolB in vivo. Recombinant bacterial PTPS-III proteins, like the P. falciparum enzyme, mediated conversion of dihydroneopterin triphosphate to HMDHP, but other PTPS proteins did not. Neither PTPS-III nor other PTPS proteins exhibited significant dihydroneopterin aldolase activity. Phylogenetic analysis indicated that PTPS-III proteins may have arisen independently in various PTPS lineages. Consistent with this possibility, merely introducing a glutamate residue into the active site of a PTPS protein conferred incipient activity in the growth complementation assay, and replacing glutamate with alanine in a PTPS-III protein abolished complementation.
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Affiliation(s)
- Anne Pribat
- Horticultural Sciences Department, University of Florida, Gainesville, Florida 32611, USA
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Chaudhuri RR, Allen AG, Owen PJ, Shalom G, Stone K, Harrison M, Burgis TA, Lockyer M, Garcia-Lara J, Foster SJ, Pleasance SJ, Peters SE, Maskell DJ, Charles IG. Comprehensive identification of essential Staphylococcus aureus genes using Transposon-Mediated Differential Hybridisation (TMDH). BMC Genomics 2009; 10:291. [PMID: 19570206 PMCID: PMC2721850 DOI: 10.1186/1471-2164-10-291] [Citation(s) in RCA: 220] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2009] [Accepted: 07/01/2009] [Indexed: 11/10/2022] Open
Abstract
Background In recent years there has been an increasing problem with Staphylococcus aureus strains that are resistant to treatment with existing antibiotics. An important starting point for the development of new antimicrobial drugs is the identification of "essential" genes that are important for bacterial survival and growth. Results We have developed a robust microarray and PCR-based method, Transposon-Mediated Differential Hybridisation (TMDH), that uses novel bioinformatics to identify transposon inserts in genome-wide libraries. Following a microarray-based screen, genes lacking transposon inserts are re-tested using a PCR and sequencing-based approach. We carried out a TMDH analysis of the S. aureus genome using a large random mariner transposon library of around a million mutants, and identified a total of 351 S. aureus genes important for survival and growth in culture. A comparison with the essential gene list experimentally derived for Bacillus subtilis highlighted interesting differences in both pathways and individual genes. Conclusion We have determined the first comprehensive list of S. aureus essential genes. This should act as a useful starting point for the identification of potential targets for novel antimicrobial compounds. The TMDH methodology we have developed is generic and could be applied to identify essential genes in other bacterial pathogens.
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Affiliation(s)
- Roy R Chaudhuri
- Department of Veterinary Medicine, University of Cambridge, Madingley Road, Cambridge, CB3 0ES, UK.
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A Gateway platform for functional genomics in Haloferax volcanii: deletion of three tRNA modification genes. ARCHAEA-AN INTERNATIONAL MICROBIOLOGICAL JOURNAL 2009; 2:211-9. [PMID: 19478918 DOI: 10.1155/2009/428489] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/24/2008] [Accepted: 01/21/2009] [Indexed: 11/17/2022]
Abstract
In part due to the existence of simple methods for its cultivation and genetic manipulation, Haloferax volcanii is a major archaeal model organism. It is the only archaeon for which the whole set of post-transcriptionally modified tRNAs has been sequenced, allowing for an in silico prediction of all RNA modification genes present in the organism. One approach to check these predictions experimentally is via the construction of targeted gene deletion mutants. Toward this goal, an integrative "Gateway vector" that allows gene deletion in H. volcanii uracil auxotrophs was constructed. The vector was used to delete three predicted tRNA modification genes: HVO_2001 (encoding an archaeal transglycosyl tranferase or arcTGT), which is involved in archeosine biosynthesis; HVO_2348 (encoding a newly discovered GTP cyclohydrolase I), which catalyzes the first step common to archaeosine and folate biosynthesis; and HVO_2736 (encoding a member of the COG1444 family), which is involved in N(4)-acetylcytidine (ac(4)C) formation. Preliminary phenotypic analysis of the deletion mutants was conducted, and confirmed all three predictions.
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McCarty RM, Bandarian V. Deciphering deazapurine biosynthesis: pathway for pyrrolopyrimidine nucleosides toyocamycin and sangivamycin. ACTA ACUST UNITED AC 2008; 15:790-8. [PMID: 18721750 DOI: 10.1016/j.chembiol.2008.07.012] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2008] [Revised: 06/03/2008] [Accepted: 07/07/2008] [Indexed: 11/28/2022]
Abstract
Pyrrolopyrimidine nucleosides analogs, collectively referred to as deazapurines, are an important class of structurally diverse compounds found in a wide variety of biological niches. In this report, a cluster of genes from Streptomyces rimosus (ATCC 14673) involved in production of the deazapurine antibiotics sangivamycin and toyocamycin was identified. The cluster includes toyocamycin nitrile hydratase, an enzyme that catalyzes the conversion of toyocamycin to sangivamycin. In addition to this rare nitrile hydratase, the cluster encodes a GTP cyclohydrolase I, linking the biosynthesis of deazapurines to folate biosynthesis, and a set of purine salvage/biosynthesis genes, which presumably convert the guanine moiety from GTP to the adenine-like deazapurine base found in toyocamycin and sangivamycin. The gene cluster presented here could potentially serve as a model to allow identification of deazapurine biosynthetic pathways in other bacterial species.
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Affiliation(s)
- Reid M McCarty
- Department of Biochemistry and Molecular Biophysics, University of Arizona, 1041 E. Lowell Street, Tucson, AZ 85721, USA
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Biosynthesis of 7-deazaguanosine-modified tRNA nucleosides: a new role for GTP cyclohydrolase I. J Bacteriol 2008; 190:7876-84. [PMID: 18931107 DOI: 10.1128/jb.00874-08] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Queuosine (Q) and archaeosine (G(+)) are hypermodified ribonucleosides found in tRNA. Q is present in the anticodon region of tRNA(GUN) in Eukarya and Bacteria, while G(+) is found at position 15 in the D-loop of archaeal tRNA. Prokaryotes produce these 7-deazaguanosine derivatives de novo from GTP through the 7-cyano-7-deazaguanine (pre-Q(0)) intermediate, but mammals import the free base, queuine, obtained from the diet or the intestinal flora. By combining the results of comparative genomic analysis with those of genetic studies, we show that the first enzyme of the folate pathway, GTP cyclohydrolase I (GCYH-I), encoded in Escherichia coli by folE, is also the first enzyme of pre-Q(0) biosynthesis in both prokaryotic kingdoms. Indeed, tRNA extracted from an E. coli DeltafolE strain is devoid of Q and the deficiency is complemented by expressing GCYH-I-encoding genes from different bacterial or archaeal origins. In a similar fashion, tRNA extracted from a Haloferax volcanii strain carrying a deletion of the GCYH-I-encoding gene contains only traces of G(+). These results link the production of a tRNA-modified base to primary metabolism and further clarify the biosynthetic pathway for these complex modified nucleosides.
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Cicmil N, Huang RH. Crystal structure of QueC from Bacillus subtilis: an enzyme involved in preQ1 biosynthesis. Proteins 2008; 72:1084-8. [PMID: 18491386 DOI: 10.1002/prot.22098] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Affiliation(s)
- Nenad Cicmil
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
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Hou S, Makarova KS, Saw JHW, Senin P, Ly BV, Zhou Z, Ren Y, Wang J, Galperin MY, Omelchenko MV, Wolf YI, Yutin N, Koonin EV, Stott MB, Mountain BW, Crowe MA, Smirnova AV, Dunfield PF, Feng L, Wang L, Alam M. Complete genome sequence of the extremely acidophilic methanotroph isolate V4, Methylacidiphilum infernorum, a representative of the bacterial phylum Verrucomicrobia. Biol Direct 2008; 3:26. [PMID: 18593465 PMCID: PMC2474590 DOI: 10.1186/1745-6150-3-26] [Citation(s) in RCA: 134] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2008] [Accepted: 07/01/2008] [Indexed: 12/31/2022] Open
Abstract
Background The phylum Verrucomicrobia is a widespread but poorly characterized bacterial clade. Although cultivation-independent approaches detect representatives of this phylum in a wide range of environments, including soils, seawater, hot springs and human gastrointestinal tract, only few have been isolated in pure culture. We have recently reported cultivation and initial characterization of an extremely acidophilic methanotrophic member of the Verrucomicrobia, strain V4, isolated from the Hell's Gate geothermal area in New Zealand. Similar organisms were independently isolated from geothermal systems in Italy and Russia. Results We report the complete genome sequence of strain V4, the first one from a representative of the Verrucomicrobia. Isolate V4, initially named "Methylokorus infernorum" (and recently renamed Methylacidiphilum infernorum) is an autotrophic bacterium with a streamlined genome of ~2.3 Mbp that encodes simple signal transduction pathways and has a limited potential for regulation of gene expression. Central metabolism of M. infernorum was reconstructed almost completely and revealed highly interconnected pathways of autotrophic central metabolism and modifications of C1-utilization pathways compared to other known methylotrophs. The M. infernorum genome does not encode tubulin, which was previously discovered in bacteria of the genus Prosthecobacter, or close homologs of any other signature eukaryotic proteins. Phylogenetic analysis of ribosomal proteins and RNA polymerase subunits unequivocally supports grouping Planctomycetes, Verrucomicrobia and Chlamydiae into a single clade, the PVC superphylum, despite dramatically different gene content in members of these three groups. Comparative-genomic analysis suggests that evolution of the M. infernorum lineage involved extensive horizontal gene exchange with a variety of bacteria. The genome of M. infernorum shows apparent adaptations for existence under extremely acidic conditions including a major upward shift in the isoelectric points of proteins. Conclusion The results of genome analysis of M. infernorum support the monophyly of the PVC superphylum. M. infernorum possesses a streamlined genome but seems to have acquired numerous genes including those for enzymes of methylotrophic pathways via horizontal gene transfer, in particular, from Proteobacteria. Reviewers This article was reviewed by John A. Fuerst, Ludmila Chistoserdova, and Radhey S. Gupta.
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Affiliation(s)
- Shaobin Hou
- Advance Studies in Genomics, Proteomics and Bioinformatics, College of Natural Sciences, University of Hawaii, Keller Hall #319, Honolulu, Hawaii, 96822, USA.
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Regulation of the Bacillus subtilis yciC gene and insights into the DNA-binding specificity of the zinc-sensing metalloregulator Zur. J Bacteriol 2008; 190:3482-8. [PMID: 18344368 DOI: 10.1128/jb.01978-07] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The Bacillus subtilis Zur protein regulates zinc homeostasis by repressing at least 10 genes in response to zinc sufficiency. One of these genes, yciC, encodes an abundant protein postulated to function as a metallochaperone. Here, we used a genetic approach to identify the cis-acting elements and trans-acting factors contributing to the tight repression of yciC. Initial studies led to the identification of only trans-acting mutations, and, when the selection was repeated using a transposon library, all recovered mutants contained insertionally inactivated zur. Using a zur merodiploid strain, we obtained two cis-acting mutations that contained large deletions in the yciC regulatory region. We demonstrate that the yciC regulatory region contains two functional Zur boxes: a primary site (C2) overlapping a sigma(A) promoter approximately 200 bp upstream of yciC and a second site near the translational start point (C1). Zur binds to both of these sites to mediate strong, zinc-dependent repression of yciC. Deletion studies indicate that either Zur box is sufficient for repression, although repression by Zur bound to C2 is more efficient. Binding studies demonstrate that both sites bind Zur with high affinity. Sequence alignment of these and previously described Zur boxes suggest that Zur recognizes a more extended operator than other Fur family members. We used synthetic oligonucleotides to identify bases critical for DNA binding by Zur. Unlike Fur and PerR, which bind efficiently to sequences containing a core 7-1-7 repeat element, Zur requires a 9-1-9 inverted repeat for high-affinity binding.
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Abstract
In spite of their common hypersaline environment, halophilic archaea are surprisingly different in their nutritional demands and metabolic pathways. The metabolic diversity of halophilic archaea was investigated at the genomic level through systematic metabolic reconstruction and comparative analysis of four completely sequenced species: Halobacterium salinarum, Haloarcula marismortui, Haloquadratum walsbyi, and the haloalkaliphile Natronomonas pharaonis. The comparative study reveals different sets of enzyme genes amongst halophilic archaea, e.g. in glycerol degradation, pentose metabolism, and folate synthesis. The carefully assessed metabolic data represent a reliable resource for future system biology approaches as it also links to current experimental data on (halo)archaea from the literature.
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de Crécy-Lagard V, Hanson AD. Finding novel metabolic genes through plant-prokaryote phylogenomics. Trends Microbiol 2007; 15:563-70. [PMID: 17997099 DOI: 10.1016/j.tim.2007.10.008] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2007] [Revised: 10/12/2007] [Accepted: 10/12/2007] [Indexed: 12/26/2022]
Abstract
Plants and prokaryotes share thousands of genes. Those with known functions mostly encode enzymes of primary metabolism or other key biochemical components, and the same is almost surely true of those whose function is still obscure. The availability of hundreds of sequenced genomes and of rich postgenomic resources now makes possible the use of comparative genomics ('phylogenomics') of plants and prokaryotes to infer, and then verify, functions for such unknown genes. In this type of analysis, plant and prokaryote data each inform the search for function, and do so synergistically. This breaks with the past pattern of gene discovery, in which the information flow was most often unidirectional from prokaryotes to plants.
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Affiliation(s)
- Valérie de Crécy-Lagard
- Microbiology and Cell Science Department, University of Florida, Gainesville, FL 32611, USA.
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de Crécy-Lagard V, El Yacoubi B, de la Garza RD, Noiriel A, Hanson AD. Comparative genomics of bacterial and plant folate synthesis and salvage: predictions and validations. BMC Genomics 2007; 8:245. [PMID: 17645794 PMCID: PMC1971073 DOI: 10.1186/1471-2164-8-245] [Citation(s) in RCA: 97] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2006] [Accepted: 07/23/2007] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Folate synthesis and salvage pathways are relatively well known from classical biochemistry and genetics but they have not been subjected to comparative genomic analysis. The availability of genome sequences from hundreds of diverse bacteria, and from Arabidopsis thaliana, enabled such an analysis using the SEED database and its tools. This study reports the results of the analysis and integrates them with new and existing experimental data. RESULTS Based on sequence similarity and the clustering, fusion, and phylogenetic distribution of genes, several functional predictions emerged from this analysis. For bacteria, these included the existence of novel GTP cyclohydrolase I and folylpolyglutamate synthase gene families, and of a trifunctional p-aminobenzoate synthesis gene. For plants and bacteria, the predictions comprised the identities of a 'missing' folate synthesis gene (folQ) and of a folate transporter, and the absence from plants of a folate salvage enzyme. Genetic and biochemical tests bore out these predictions. CONCLUSION For bacteria, these results demonstrate that much can be learnt from comparative genomics, even for well-explored primary metabolic pathways. For plants, the findings particularly illustrate the potential for rapid functional assignment of unknown genes that have prokaryotic homologs, by analyzing which genes are associated with the latter. More generally, our data indicate how combined genomic analysis of both plants and prokaryotes can be more powerful than isolated examination of either group alone.
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Affiliation(s)
- Valérie de Crécy-Lagard
- Department of Microbiology and Cell Science, University of Florida, Gainesville, FL 32611, USA
| | - Basma El Yacoubi
- Department of Microbiology and Cell Science, University of Florida, Gainesville, FL 32611, USA
| | | | - Alexandre Noiriel
- Department of Horticultural Sciences, University of Florida, Gainesville, FL 32611, USA
| | - Andrew D Hanson
- Department of Horticultural Sciences, University of Florida, Gainesville, FL 32611, USA
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Grochowski LL, Xu H, Leung K, White RH. Characterization of an Fe(2+)-dependent archaeal-specific GTP cyclohydrolase, MptA, from Methanocaldococcus jannaschii. Biochemistry 2007; 46:6658-67. [PMID: 17497938 DOI: 10.1021/bi700052a] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The first step in the biosynthesis of pterins in bacteria and plants is the conversion of GTP to 7,8-dihydro-d-neopterin triphosphate catalyzed by GTP cyclohydrolase I (GTPCHI). Although GTP has been shown to be a precursor of pterins in archaea, homologues of GTPCHI have not been identified in most archaeal genomes. Here we report the identification of a new GTP cyclohydrolase that converts GTP to 7,8-dihydro-d-neopterin 2',3'-cyclic phosphate, the first intermediate in methanopterin biosynthesis in methanogenic archaea. The enzyme from Methanocaldococcus jannaschii is designated MptA to indicate that it catalyzes the first step in the biosynthesis of methanopterin. MptA is the archetype of a new class of GTP cyclohydrolases that catalyzes a series of reactions most similar to that seen with GTPCHI but unique in that the cyclic phosphate is the product. MptA was found to require Fe2+ for activity. Mutation of conserved histidine residues H200N, H293N, and H295N, expected to be involved in Fe2+ binding, resulted in reduced enzymatic activity but no reduction in the amount of bound iron.
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Affiliation(s)
- Laura L Grochowski
- Department of Biochemistry, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061, USA
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Abstract
As the molecular adapters between codons and amino acids, transfer-RNAs are pivotal molecules of the genetic code. The coding properties of a tRNA molecule do not reside only in its primary sequence. Posttranscriptional nucleoside modifications, particularly in the anticodon loop, can modify cognate codon recognition, affect aminoacylation properties, or stabilize the codon-anticodon wobble base pairing to prevent ribosomal frameshifting. Despite a wealth of biophysical and structural knowledge of the tRNA modifications themselves, their pathways of biosynthesis had been until recently only partially characterized. This discrepancy was mainly due to the lack of obvious phenotypes for tRNA modification-deficient strains and to the difficulty of the biochemical assays used to detect tRNA modifications. However, the availability of hundreds of whole-genome sequences has allowed the identification of many of these missing tRNA-modification genes. This chapter reviews the methods that were used to identify these genes with a special emphasis on the comparative genomic approaches. Methods that link gene and function but do not rely on sequence homology will be detailed, with examples taken from the tRNA modification field.
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