1
|
Pollo-Oliveira L, Davis NK, Hossain I, Ho P, Yuan Y, Salguero García P, Pereira C, Byrne SR, Leng J, Sze M, Blaby-Haas CE, Sekowska A, Montoya A, Begley T, Danchin A, Aalberts DP, Angerhofer A, Hunt J, Conesa A, Dedon PC, de Crécy-Lagard V. The absence of the queuosine tRNA modification leads to pleiotropic phenotypes revealing perturbations of metal and oxidative stress homeostasis in Escherichia coli K12. Metallomics 2022; 14:mfac065. [PMID: 36066904 PMCID: PMC9508795 DOI: 10.1093/mtomcs/mfac065] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2022] [Accepted: 09/09/2022] [Indexed: 02/04/2023]
Abstract
Queuosine (Q) is a conserved hypermodification of the wobble base of tRNA containing GUN anticodons but the physiological consequences of Q deficiency are poorly understood in bacteria. This work combines transcriptomic, proteomic and physiological studies to characterize a Q-deficient Escherichia coli K12 MG1655 mutant. The absence of Q led to an increased resistance to nickel and cobalt, and to an increased sensitivity to cadmium, compared to the wild-type (WT) strain. Transcriptomic analysis of the WT and Q-deficient strains, grown in the presence and absence of nickel, revealed that the nickel transporter genes (nikABCDE) are downregulated in the Q- mutant, even when nickel is not added. This mutant is therefore primed to resist to high nickel levels. Downstream analysis of the transcriptomic data suggested that the absence of Q triggers an atypical oxidative stress response, confirmed by the detection of slightly elevated reactive oxygen species (ROS) levels in the mutant, increased sensitivity to hydrogen peroxide and paraquat, and a subtle growth phenotype in a strain prone to accumulation of ROS.
Collapse
Affiliation(s)
- Leticia Pollo-Oliveira
- Department of Microbiology and Cell Science, University of Florida, Gainesville, FL 32611, USA
| | - Nick K Davis
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Intekhab Hossain
- Department of Physics, Williams College, Williamstown, MA 01267, USA
| | - Peiying Ho
- Antimicrobial Resistance Interdisciplinary Research Group, Singapore-MIT Alliance for Research and Technology, Singapore 138602, Singapore
| | - Yifeng Yuan
- Department of Microbiology and Cell Science, University of Florida, Gainesville, FL 32611, USA
| | - Pedro Salguero García
- Department of Applied Statistics, Operations Research and Quality, Universitat Politècnica de València, Valencia 46022, Spain
| | - Cécile Pereira
- Department of Microbiology and Cell Science, University of Florida, Gainesville, FL 32611, USA
| | - Shane R Byrne
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Jiapeng Leng
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Melody Sze
- Department of Microbiology and Cell Science, University of Florida, Gainesville, FL 32611, USA
| | - Crysten E Blaby-Haas
- Department of Microbiology and Cell Science, University of Florida, Gainesville, FL 32611, USA
| | | | - Alvaro Montoya
- Department of Chemistry, University of Florida, Gainesville, FL 32611, USA
| | - Thomas Begley
- The RNA Institute and Department of Biology, University at Albany, Albany, NY 12222, USA
| | - Antoine Danchin
- Kodikos Labs, 23 rue Baldassini, Lyon 69007, France
- School of Biomedical Sciences, Li Kashing Faculty of Medicine, University of Hong Kong, Pokfulam, SAR Hong Kong
| | - Daniel P Aalberts
- Department of Physics, Williams College, Williamstown, MA 01267, USA
| | | | - John Hunt
- Department of Biological Sciences, Columbia University, New York, NY 10024, USA
| | - Ana Conesa
- Department of Microbiology and Cell Science, University of Florida, Gainesville, FL 32611, USA
- Institute for Integrative Systems Biology, Spanish National Research Council, Paterna 46980, Spain
| | - Peter C Dedon
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
- Antimicrobial Resistance Interdisciplinary Research Group, Singapore-MIT Alliance for Research and Technology, Singapore 138602, Singapore
| | - Valérie de Crécy-Lagard
- Department of Microbiology and Cell Science, University of Florida, Gainesville, FL 32611, USA
- Genetic Institute, University of Florida, Gainesville, FL 32611, USA
| |
Collapse
|
2
|
Bashor CJ, Hilton IB, Bandukwala H, Smith DM, Veiseh O. Engineering the next generation of cell-based therapeutics. Nat Rev Drug Discov 2022; 21:655-675. [PMID: 35637318 PMCID: PMC9149674 DOI: 10.1038/s41573-022-00476-6] [Citation(s) in RCA: 111] [Impact Index Per Article: 55.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/21/2022] [Indexed: 12/19/2022]
Abstract
Cell-based therapeutics are an emerging modality with the potential to treat many currently intractable diseases through uniquely powerful modes of action. Despite notable recent clinical and commercial successes, cell-based therapies continue to face numerous challenges that limit their widespread translation and commercialization, including identification of the appropriate cell source, generation of a sufficiently viable, potent and safe product that meets patient- and disease-specific needs, and the development of scalable manufacturing processes. These hurdles are being addressed through the use of cutting-edge basic research driven by next-generation engineering approaches, including genome and epigenome editing, synthetic biology and the use of biomaterials.
Collapse
Affiliation(s)
- Caleb J Bashor
- Department of Bioengineering, Rice University, Houston, TX, USA.
- Department of Biosciences, Rice University, Houston, TX, USA.
| | - Isaac B Hilton
- Department of Bioengineering, Rice University, Houston, TX, USA.
- Department of Biosciences, Rice University, Houston, TX, USA.
| | - Hozefa Bandukwala
- Sigilon Therapeutics, Cambridge, MA, USA
- Flagship Pioneering, Cambridge, MA, USA
| | - Devyn M Smith
- Sigilon Therapeutics, Cambridge, MA, USA
- Arbor Biotechnologies, Cambridge, MA, USA
| | - Omid Veiseh
- Department of Bioengineering, Rice University, Houston, TX, USA.
| |
Collapse
|
3
|
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 contains 31 different modified nucleosides, which are all, except for one (Queuosine[Q]), synthesized on an oligonucleotide precursor, which through specific enzymes later matures into tRNA. The corresponding structural genes for these enzymes are found in mono- and polycistronic operons, the latter of which have a complex transcription and translation pattern. The syntheses of some of them (e.g.,several methylated derivatives) are catalyzed by one enzyme, which is position and base specific, but synthesis of some have a very complex biosynthetic pathway involving several enzymes (e.g., 2-thiouridines, N6-threonyladenosine [t6A],and Q). Several of the modified nucleosides are essential for viability (e.g.,lysidin, t6A, 1-methylguanosine), whereas deficiency in 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, which are present in the body of the tRNA, have a primarily stabilizing effect on the tRNA. Thus, the ubiquitouspresence 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.
Collapse
|
4
|
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.
Collapse
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
| |
Collapse
|
5
|
Molybdenum reduction to molybdenum blue in Serratia sp. Strain DRY5 is catalyzed by a novel molybdenum-reducing enzyme. BIOMED RESEARCH INTERNATIONAL 2014; 2014:853084. [PMID: 24724104 PMCID: PMC3958783 DOI: 10.1155/2014/853084] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/22/2013] [Revised: 12/22/2013] [Accepted: 12/24/2013] [Indexed: 12/02/2022]
Abstract
The first purification of the Mo-reducing enzyme from Serratia sp. strain DRY5 that is responsible for molybdenum reduction to molybdenum blue in the bacterium is reported. The monomeric enzyme has an apparent molecular weight of 105 kDalton. The isoelectric point of this enzyme was 7.55. The enzyme has an optimum pH of 6.0 and maximum activity between 25 and 35°C. The Mo-reducing enzyme was extremely sensitive to temperatures above 50°C (between 54 and 70°C). A plot of initial rates against substrate concentrations at 15 mM 12-MP registered a Vmax for NADH at 12.0 nmole Mo blue/min/mg protein. The apparent Km for NADH was 0.79 mM. At 5 mM NADH, the apparent Vmax and apparent Km values for 12-MP of 12.05 nmole/min/mg protein and 3.87 mM, respectively, were obtained. The catalytic efficiency (kcat/Km) of the Mo-reducing enzyme was 5.47 M−1 s−1. The purification of this enzyme could probably help to solve the phenomenon of molybdenum reduction to molybdenum blue first reported in 1896 and would be useful for the understanding of the underlying mechanism in molybdenum bioremediation involving bioreduction.
Collapse
|
6
|
Site-directed mutagenesis identifies a molecular switch involved in copper sensing by the histidine kinase CinS in Pseudomonas putida KT2440. J Bacteriol 2009; 191:5304-11. [PMID: 19542288 DOI: 10.1128/jb.00551-09] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In the presence of copper, Pseudomonas putida activates transcription of cinAQ via the two-component system CinS-CinR. The CinS-CinR TCS was responsive to 0.5 microM copper and was specifically activated only by copper and silver. Modeling studies of CinS identified a potential copper binding site containing H37 and H147. CinS mutants with H37R and H147R mutations had an almost 10-fold reduced copper-dependent induction of cinAQ compared to the wild type.
Collapse
|
7
|
Environmental and growth phase regulation of the Streptococcus gordonii arginine deiminase genes. Appl Environ Microbiol 2008; 74:5023-30. [PMID: 18552185 DOI: 10.1128/aem.00556-08] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A 1,026-bp open reading frame sharing significant similarity with queA, which encodes a predicted S-adenosylmethionine:tRNA ribosyltransferase-isomerase responsible for queosine modification of tRNAs, was found immediately 5' of the gene for the transcriptional activator (ArcR) of the arginine deiminase system (ADS) operon of Streptococcus gordonii. The role of QueA in bacterial physiology is enigmatic, but loss of QueA has been shown to compromise stationary-phase survival or virulence in certain enteric bacteria. Interestingly, S. gordonii appears to be unique among ADS-positive bacteria in the linkage of queA with the ADS genes. A putative sigma(70) promoter (p(queA); TTGCCA-N(21)-TATAAT) was mapped 5' of queA by primer extension, and queA and arcR were shown to be cotranscribed. The expression from p(queA) was found to be constitutive under all conditions tested, but the expression of p(arcA), which drives the expression of the arc structural genes, was enhanced in stationary phase and could be induced by low pH and arginine. QueA and CcpA acted repressively on arc transcription, but neither QueA-deficient strains nor CcpA-deficient strains showed significant differences in arginine deiminase enzyme activities compared with the wild-type strain. The growth rate of a QueA-deficient strain did not differ significantly from that of the parental strain, but the QueA-deficient strain did not compete well with the wild-type during serial passage. In addition to the finding that ADS expression can be regulated separately by growth phase and pH, a significant linkage between the ADS, translational efficiency modulated by QueA, and post-exponential-phase survival of S. gordonii was found.
Collapse
|
8
|
Quaranta D, McCarty R, Bandarian V, Rensing C. The copper-inducible cin operon encodes an unusual methionine-rich azurin-like protein and a pre-Q0 reductase in Pseudomonas putida KT2440. J Bacteriol 2007; 189:5361-71. [PMID: 17483220 PMCID: PMC1951875 DOI: 10.1128/jb.00377-07] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The genome sequences of several pseudomonads have revealed a gene cluster containing genes for a two-component heavy metal histidine sensor kinase and response regulator upstream of cinA and cinQ, which we show herein to encode a copper-containing azurin-like protein and a pre-Q(0) reductase, respectively. In the presence of copper, Pseudomonas putida KT2440 produces the CinA and CinQ proteins from a bicistronic mRNA. UV-visible spectra of CinA show features at 439, 581, and 719 nm, which is typical of the plastocyanin family of proteins. The redox potential of the protein was shown to be 456 +/- 4 mV by voltametric titrations. Surprisingly, CinQ is a pyridine nucleotide-dependent nitrile oxidoreductase that catalyzes the conversion of pre-Q(0) to pre-Q(1) in the nucleoside queuosine biosynthetic pathway. Gene disruptions of cinA and cinQ did not lead to a significant increase in the copper sensitivity of P. putida KT2440 under the conditions tested. Possible roles of CinA and CinQ to help pseudomonads adapt and survive under prolonged copper stress are discussed.
Collapse
Affiliation(s)
- Davide Quaranta
- Department of Soil, Water, and Environmental Science, University of Arizona, Shantz Blvd. #38, Rm. 429, Tucson, AZ 85721, USA
| | | | | | | |
Collapse
|
9
|
Roth A, Winkler WC, Regulski EE, Lee BWK, Lim J, Jona I, Barrick JE, Ritwik A, Kim JN, Welz R, Iwata-Reuyl D, Breaker RR. A riboswitch selective for the queuosine precursor preQ1 contains an unusually small aptamer domain. Nat Struct Mol Biol 2007; 14:308-17. [PMID: 17384645 DOI: 10.1038/nsmb1224] [Citation(s) in RCA: 185] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2006] [Accepted: 03/05/2007] [Indexed: 01/09/2023]
Abstract
A previous bioinformatics-based search for riboswitches yielded several candidate motifs in eubacteria. One of these motifs commonly resides in the 5' untranslated regions of genes involved in the biosynthesis of queuosine (Q), a hypermodified nucleoside occupying the anticodon wobble position of certain transfer RNAs. Here we show that this structured RNA is part of a riboswitch selective for 7-aminomethyl-7-deazaguanine (preQ(1)), an intermediate in queuosine biosynthesis. Compared with other natural metabolite-binding RNAs, the preQ(1) aptamer appears to have a simple structure, consisting of a single stem-loop and a short tail sequence that together are formed from as few as 34 nucleotides. Despite its small size, this aptamer is highly selective for its cognate ligand in vitro and has an affinity for preQ(1) in the low nanomolar range. Relatively compact RNA structures can therefore serve effectively as metabolite receptors to regulate gene expression.
Collapse
Affiliation(s)
- Adam Roth
- Howard Hughes Medical Institute, USA
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
10
|
Schmitz RA, Achebach S, Unden G. Analysis of Fumarate Nitrate Reductase Regulator as an Oxygen Sensor in Escherichia coli. Methods Enzymol 2004; 381:628-44. [PMID: 15063703 DOI: 10.1016/s0076-6879(04)81041-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/29/2023]
Affiliation(s)
- Ruth A Schmitz
- Institute for Micorbiology and Genetics, University of Göttingen, Germany
| | | | | |
Collapse
|
11
|
Abstract
Transfer RNA (tRNA) is structurally unique among nucleic acids in harboring an astonishing diversity of post-transcriptionally modified nucleoside. Two of the most radically modified nucleosides known to occur in tRNA are queuosine and archaeosine, both of which are characterized by a 7-deazaguanosine core structure. In spite of the phylogenetic segregation observed for these nucleosides (queuosine is present in Eukarya and Bacteria, while archaeosine is present only in Archaea), their structural similarity suggested a common biosynthetic origin, and recent biochemical and genetic studies have provided compelling evidence that a significant portion of their biosynthesis may in fact be identical. This review covers current understanding of the physiology and biosynthesis of these remarkable nucleosides, with particular emphasis on the only two enzymes that have been discovered in the pathways: tRNA-guanine transglycosylase (TGT), which catalyzes the insertion of a modified base into the polynucleotide with the concomitant elimination of the genetically encoded guanine in the biosynthesis of both nucleosides, and S-adenosylmethionine:tRNA ribosyltransferase-isomerase (QueA), which catalyzes the penultimate step in the biosynthesis of queuosine, the construction of the carbocyclic side chain.
Collapse
Affiliation(s)
- Dirk Iwata-Reuyl
- Department of Chemistry, Portland State University, P.O. Box 751, Portland, OR 97201, USA.
| |
Collapse
|
12
|
Dineshkumar TK, Thanedar S, Subbulakshmi C, Varshney U. An unexpected absence of queuosine modification in the tRNAs of an Escherichia coli B strain. MICROBIOLOGY (READING, ENGLAND) 2002; 148:3779-3787. [PMID: 12480882 DOI: 10.1099/00221287-148-12-3779] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The post-transcriptional processing of tRNAs decorates them with a number of modified bases important for their biological functions. Queuosine, found in the tRNAs with GUN anticodons (Asp, Asn, His, Tyr), is an extensively modified base whose biosynthetic pathway is still unclear. In this study, it was observed that the tRNA(Tyr) from Escherichia coli B105 (a B strain) migrated faster than that from E. coli CA274 (a K-12 strain) on acid urea gels. The organization of tRNA(Tyr) genes in E. coli B105 was found to be typical of the B strains. Subsequent analysis of tRNA(Tyr) and tRNA(His) from several strains of E. coli on acid urea gels, and modified base analysis of tRNA preparations enriched for tRNA(Tyr), showed that E. coli B105 lacked queuosine in its tRNAs. However, the lack of queuosine in tRNAs was not a common feature of all E. coli B strains. The tgt and queA genes in B105 were shown to be functional by their ability to complement tgt and queA mutant strains. These observations suggested a block at the step of the biosynthesis of preQ(1) (or preQ(0)) in the B105 strain. Interestingly, a multicopy vector harbouring a functional tgt gene was toxic to E. coli B105 but not to CA274. Also, in mixed cultures, E. coli B105 was readily competed out by the CA274 strain. The importance of these observations and this novel strain (E. coli B105) in unravelling the mechanism of preQ(1) or preQ(0) biosynthesis is discussed.
Collapse
MESH Headings
- Electrophoresis, Polyacrylamide Gel
- Escherichia coli/genetics
- Escherichia coli/growth & development
- Escherichia coli/metabolism
- Nucleoside Q/metabolism
- Pentosyltransferases/metabolism
- Pyrimidinones/metabolism
- Pyrroles/metabolism
- RNA, Bacterial/chemistry
- RNA, Bacterial/genetics
- RNA, Bacterial/metabolism
- RNA, Transfer, Tyr/chemistry
- RNA, Transfer, Tyr/genetics
- RNA, Transfer, Tyr/metabolism
- Urea
Collapse
Affiliation(s)
- T K Dineshkumar
- Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore 560012, India1
| | - Swapna Thanedar
- Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore 560012, India1
| | - C Subbulakshmi
- Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore 560012, India1
| | - Umesh Varshney
- Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore 560012, India1
| |
Collapse
|
13
|
Deshpande KL, Katze JR. Characterization of cDNA encoding the human tRNA-guanine transglycosylase (TGT) catalytic subunit. Gene 2001; 265:205-12. [PMID: 11255023 DOI: 10.1016/s0378-1119(01)00368-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Queuosine (Q) is a 7-deazaguanosine found in the first position of the anticodon of tRNAs that recognize NAU and NAC codons (Tyr, Asn, Asp and His). Eukaryotes synthesize Q by the base-for-base exchange of queuine (Q base) for guanine in the unmodified tRNA, a reaction catalyzed by TGT. A search of the human EST database for sequences with significant homology to the well studied TGT from Escherichia coli identified several candidates for full-length (1.3-1.4 kb) cDNA clones. Three candidate cDNA clones, available from IMAGE Consortium, LLNL, (Lennon et al., 1996, Genomics 33, 151-152) were obtained: IMAGE Clone Id Nos. 611146, 1422928, and 72154. Here we report the complete sequences of these clones. IMAGE:72154 contains an ORF encoding a 44 kDa polypeptide with high homology to bacterial TGTs and was subcloned into the mammalian expression vector pMAMneo-Cat. When this construct was transfected into the TGT-negative cell line, GC(3)/c1 (Gündüz et al., 1992, Biochim. Biophys. Acta 1139, 229-238), it restored the ability of the cells to form Q-containing tRNA. This TGT cDNA sequence is encoded in human chromosome 19 clone CTC-539A10 (GenBank accession no. AC011475), enabling determination of the exon-intron boundaries for the TGT gene. The sequence of IMAGE:611146 is 5'-truncated by 76 bp compared to that from IMAGE:72154 and, except for two differences in the 3'-non-coding region, the remainder of the sequence is identical to that of IMAGE:72154. IMAGE:1422928 is a 1390 bp chimera: the 5'-portion, bp 1-708, is identical to a genomic DNA sequence from chromosome 15 (GenBank accession no. AC067805, bp 148976-149683); the 3'-end, bp 726-1390, is identical to the 3'-end of the TGT cDNA sequence from IMAGE:611146.
Collapse
Affiliation(s)
- K L Deshpande
- Department of Molecular Sciences, The University of Tennessee Health Science Center, 858 Madison Avenue, 38163, Memphis, TN, USA
| | | |
Collapse
|
14
|
Durand JM, Dagberg B, Uhlin BE, Björk GR. Transfer RNA modification, temperature and DNA superhelicity have a common target in the regulatory network of the virulence of Shigella flexneri: the expression of the virF gene. Mol Microbiol 2000; 35:924-35. [PMID: 10692168 DOI: 10.1046/j.1365-2958.2000.01767.x] [Citation(s) in RCA: 112] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Full expression of the virulence genes of Shigella flexneri requires the presence of two modified nucleosides in the tRNA [queuosine, Q34, present in the wobble position (position 34) and 2-methylthio-N6-isopentenyladenosine (ms2i6A37, adjacent to and 3' of the anticodon)]. The synthesis of these two nucleosides depends on the products of the tgt and miaA genes respectively. We have shown that the intracellular concentration of the virulence-related transcriptional regulator VirF is reduced in the absence of either of these modified nucleosides. The intracellular concentration of VirF is correlated with the expression of the virulence genes. Overproduction of VirF in the tgt and the miaA mutants suppressed the less virulent (tgt) or the avirulent (miaA) phenotypes respectively, caused by the tRNA modification deficiency. This suggests that the primary result of undermodification of the tRNA is a poor translation of virF mRNA and not of any other mRNA whose product acts downstream of the action of VirF. Shigella showed no virulence phenotypes at 30 degrees C, but forced synthesis of VirF at 30 degrees C induced the virulence phenotype at this low temperature. In addition, removal of the known gene silencer H-NS by a mutation in its structural gene hns increased the synthesis of VirF at low temperature and thus induced a virulent phenotype at 30 degrees C. Conversely, decreased expression of VirF at 37 degrees C induced by the addition of novobiocin, a known inhibitor of gyrase, led to an avirulent phenotype. We conclude that tRNA modification, temperature and superhelicity have the same target - the expression of VirF - to influence the expression of the central regulatory gene virB and thereby the virulence of Shigella. These results further strengthen the suggestion that the concentration of VirF is the critical factor in the regulation of virulence in Shigella. In addition, they emphasize the role of the bacterial translational machinery in the regulation of the expression of virulence genes which appears here quantitatively as important as the well-established regulation on the transcriptional level.
Collapse
Affiliation(s)
- J M Durand
- Department of Microbiology, Umeå University, S-90187 Umeå, Sweden
| | | | | | | |
Collapse
|
15
|
Abstract
This review discusses various mechanisms that regulatory proteins use to control gene expression in response to alterations in redox. The transcription factor SoxR contains stable [2Fe-2S] centers that promote transcription activation when oxidized. FNR contains [4Fe-4S] centers that disassemble under oxidizing conditions, which affects DNA-binding activity. FixL is a histidine sensor kinase that utilizes heme as a cofactor to bind oxygen, which affects its autophosphorylation activity. NifL is a flavoprotein that contains FAD as a redox responsive cofactor. Under oxidizing conditions, NifL binds and inactivates NifA, the transcriptional activator of the nitrogen fixation genes. OxyR is a transcription factor that responds to redox by breaking or forming disulfide bonds that affect its DNA-binding activity. The ability of the histidine sensor kinase ArcB to promote phosphorylation of the response regulator ArcA is affected by multiple factors such as anaerobic metabolites and the redox state of the membrane. The global regulator of anaerobic gene expression in alpha-purple proteobacteria, RegB, appears to directly monitor respiratory activity of cytochrome oxidase. The aerobic repressor of photopigment synthesis, CrtJ, seems to contain a redox responsive cysteine. Finally, oxygen-sensitive rhizobial NifA proteins presumably bind a metal cofactor that senses redox. The functional variability of these regulatory proteins demonstrates that prokaryotes apply many different mechanisms to sense and respond to alterations in redox.
Collapse
Affiliation(s)
- C E Bauer
- Department of Biology, Indiana University, Bloomington 47405, USA
| | | | | |
Collapse
|
16
|
Björk GR, Durand JM, Hagervall TG, Leipuviene R, Lundgren HK, Nilsson K, Chen P, Qian Q, Urbonavicius J. Transfer RNA modification: influence on translational frameshifting and metabolism. FEBS Lett 1999; 452:47-51. [PMID: 10376676 DOI: 10.1016/s0014-5793(99)00528-1] [Citation(s) in RCA: 97] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Transfer RNA modification improves the rate of aa-tRNA selection at the A-site and the fitness in the P-site and thereby prevents frameshifting according to a new model how frameshifting occurs [Qian et al. (1998) Mol. Cell 1, 471-482]. Evidence that the presence of various modified nucleosides in tRNA also influences central metabolism, thiamine metabolism, and bacterial virulence is reviewed.
Collapse
Affiliation(s)
- G R Björk
- Department of Microbiology, Umeå University, Sweden.
| | | | | | | | | | | | | | | | | |
Collapse
|
17
|
Durand JM, Björk GR, Kuwae A, Yoshikawa M, Sasakawa C. The modified nucleoside 2-methylthio-N6-isopentenyladenosine in tRNA of Shigella flexneri is required for expression of virulence genes. J Bacteriol 1997; 179:5777-82. [PMID: 9294434 PMCID: PMC179466 DOI: 10.1128/jb.179.18.5777-5782.1997] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The virulence of the human pathogen Shigella flexneri is dependent on both chromosome- and large-virulence-plasmid-encoded genes. A kanamycin resistance cassette mutation in the miaA gene (miaA::Km Sma), which encodes the tRNA N6-isopentyladenosine (i6A37) synthetase and is involved in the first step of the synthesis of the modified nucleoside 2-methylthio-N6-isopentenyladenosine (ms2i6A), was transferred to the chromosome of S. flexneri 2a by phage P1 transduction. In the wild-type bacterium, ms2i6A37 is present in position 37 (next to and 3' of the anticodon) in a subset of tRNA species-reading codons starting with U (except tRNA(Ser) species SerI and SerV). The miaA::Km Sma mutant of S. flexneri accordingly lacked ms2i6A37 in its tRNA. In addition, the mutant strains showed reduced expression of the virulence-related genes ipaB, ipaC, ipaD, virG, and virF, accounting for sixfold-reduced contact hemolytic activity and a delayed response in the focus plaque assay. A cloned sequence resulting from PCR amplification of the wild-type Shigella chromosome and exhibiting 99% homology with the nucleotide sequence of the Escherichia coli miaA gene complemented the virulence-associated phenotypes as well as the level of the modified nucleoside ms2i6A in the tRNA of the miaA mutants. In the miaA mutant, the level of the virulence-associated protein VirF was reduced 10-fold compared with the wild type. However, the levels of virF mRNA were identical in the mutant and in the wild type. These findings suggest that a posttranscriptional mechanism influenced by the presence of the modified nucleoside ms2i6A in the tRNA is involved in the expression of the virF gene. The role of the miaA gene in the virulence of other Shigella species and in enteroinvasive E. coli was further generalized.
Collapse
Affiliation(s)
- J M Durand
- Department of Microbiology, Umeå University, Sweden
| | | | | | | | | |
Collapse
|
18
|
Reuter K, Ficner R. Sequence analysis and overexpression of the Zymomonas mobilis tgt gene encoding tRNA-guanine transglycosylase: purification and biochemical characterization of the enzyme. J Bacteriol 1995; 177:5284-8. [PMID: 7665516 PMCID: PMC177320 DOI: 10.1128/jb.177.18.5284-5288.1995] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
tRNA-guanine transglycosylase (Tgt) is involved in the biosynthesis of the hypermodified tRNA nucleoside queuosine (Q). It catalyzes the posttranscriptional base exchange of the Q precursor 7-aminomethyl-7-deazaguanine (preQ1) with the genetically encoded guanine in the anticodon of tRNA(Asp), tRNA(Asn), tRNA(His), and tRNA(Tyr). A partially sequenced gene upstream of the DNA ligase (lig) gene of the Zymomonas mobilis chromosome shows strong homology to the tgt gene of Escherichia coli (K.B. Shark and T. Conway, FEMS Microbiol. Lett. 96:19-26, 1992). We showed that this gene is able to complement the tgt mutation in E. coli SJ1505, and we determined its complete sequence. Four start codons were possible for this gene, resulting in proteins of 386 to 399 amino acids (M(r), 42,800 to 44,300) showing 60.4% sequence identity with Tgt from E. coli. The smallest of the four possible reading frames, which was still extended at its 5' end compared with the E. coli tgt gene, was overexpressed in E. coli. The gene product was purified to homogeneity and was biochemically characterized. The kinetical parameters were virtually identical to those published for the E. coli enzyme. In contrast to E. coli Tgt, which is reported to be a homotrimer, Z. mobilis Tgt was found to be a monomer according to gel filtration. In this study, it was shown that the formation of homotrimers by the E. coli enzyme is readily reversible and is dependent on protein concentration.
Collapse
Affiliation(s)
- K Reuter
- Institut für Biochemie, Universität Erlangen-Nürnberg, Germany
| | | |
Collapse
|
19
|
Björk GR. Genetic dissection of synthesis and function of modified nucleosides in bacterial transfer RNA. PROGRESS IN NUCLEIC ACID RESEARCH AND MOLECULAR BIOLOGY 1995; 50:263-338. [PMID: 7538683 DOI: 10.1016/s0079-6603(08)60817-x] [Citation(s) in RCA: 88] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Affiliation(s)
- G R Björk
- Department of Microbiology, Umeå University, Sweden
| |
Collapse
|
20
|
Nakanishi S, Ueda T, Hori H, Yamazaki N, Okada N, Watanabe K. A UGU sequence in the anticodon loop is a minimum requirement for recognition by Escherichia coli tRNA-guanine transglycosylase. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(18)31624-7] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
|
21
|
Durand JM, Okada N, Tobe T, Watarai M, Fukuda I, Suzuki T, Nakata N, Komatsu K, Yoshikawa M, Sasakawa C. vacC, a virulence-associated chromosomal locus of Shigella flexneri, is homologous to tgt, a gene encoding tRNA-guanine transglycosylase (Tgt) of Escherichia coli K-12. J Bacteriol 1994; 176:4627-34. [PMID: 8045893 PMCID: PMC196283 DOI: 10.1128/jb.176.15.4627-4634.1994] [Citation(s) in RCA: 108] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
The genetic determinants required for invasion of epithelial cells by Shigella flexneri and for the subsequent bacterial spreading are encoded by the large virulence plasmid. Expression of the virulence genes is under the control of various genes on the large plasmid as well as on the chromosome. We previously identified one of the virulence-associated loci near phoBR in the NotI-C fragment of the chromosome of S. flexneri 2a YSH6000 and designated the locus vacC. The vacC mutant showed decreased levels of IpaC, and IpaD proteins as well as transcription of ipa, an operon essential for bacterial invasion (N. Okada, C. Sasakawa, T. Tobe, M. Yamada, S. Nagai, K. A. Talukder, K. Komatsu, S. Kanegasaki, and M. Yoshikawa, Mol. Microbiol. 5:187-195, 1991). To elucidate the molecular nature of the vacC locus, we cloned the vacC region from YSH6000 on a 1.8-kb SalI-BamHI DNA fragment. The nucleotide sequence of the 1,822-bp vacC clone was highly (> 98%) homologous to the tgt region of Escherichia coli K-12, which is located at 9.3 min on the linkage map. Complementation tests indicated that the vacC function was encoded by an open reading frame expressing a 42.5-kDa protein, which corresponded to the tgt gene of E. coli K-12, coding for tRNA-guanine transglycosylase (Tgt) (K. Reuter, R. Slany, F. Ullrich, and H. Kersten, J. Bacteriol. 173:2256-2264, 1991). The cloned tgt gene from E. coli K-12 restored the virulence phenotype to the vacC mutant of YSH6000. Characterization of the vacC mutant indicated that levels of VirG, a protein essential for bacterial spreading, and VirF, the positive regulator for the expression of the virG and ipaBCD operons, decreased significantly compared with those of the wild type. Similar phenotypic changes occurred in vacC mutants constructed by insertion of a neomycin resistance gene in shigellae and enteroinvasive E. coli strains, consistent with the hypothesis that the vacC (tgt) gene contributes to the pathogenicity of Shigella flexneri.
Collapse
Affiliation(s)
- J M Durand
- Department of Bacteriology, University of Tokyo, Japan
| | | | | | | | | | | | | | | | | | | |
Collapse
|
22
|
Slany RK, Bösl M, Kersten H. Transfer and isomerization of the ribose moiety of AdoMet during the biosynthesis of queuosine tRNAs, a new unique reaction catalyzed by the QueA protein from Escherichia coli. Biochimie 1994; 76:389-93. [PMID: 7849103 DOI: 10.1016/0300-9084(94)90113-9] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The enzyme QueA of E coli is involved in the biosynthesis of the hypermodified tRNA nucleoside queuosine. The enzyme catalyzes the synthesis of an epoxycyclopentane moiety and transfers this compound to specific tRNAs containing the queuosine precursor 7-(aminomethyl)-7-deazaguanine (preQ1). S-adenosylmethionine (AdoMet) is the sole cofactor that is required for this reaction (Slany et al, 1993, Biochemistry 32, 7811-7817). To proof that the ribose moiety of AdoMet is the precursor of the epoxycyclopentane moiety, labeled AdoMet, was generated from different types of 3H ATP and methionine by the AdoMet synthetase enzyme (MetK) from E coli. The resulting 3H labeled AdoMet was directly used as the cofactor for the QueA reaction. Using [2,5', 8-3H]ATP, containing tritium at C5' of the ribose ring, resulted in an incorporation of radioactivity into preQ1 tRNA, whereas this was not the case when [2,8-3H]ATP was applied. A model for the reaction catalyzed by the S-adenosylmethionine:tRNA ribosyltransferase-isomerase QueA is proposed.
Collapse
Affiliation(s)
- R K Slany
- Institut für Biochimie, Universität Erlangen, Germany
| | | | | |
Collapse
|
23
|
Abstract
A list of currently identified gene products of Escherichia coli is given, together with a bibliography that provides pointers to the literature on each gene product. A scheme to categorize cellular functions is used to classify the gene products of E. coli so far identified. A count shows that the numbers of genes concerned with small-molecule metabolism are on the same order as the numbers concerned with macromolecule biosynthesis and degradation. One large category is the category of tRNAs and their synthetases. Another is the category of transport elements. The categories of cell structure and cellular processes other than metabolism are smaller. Other subjects discussed are the occurrence in the E. coli genome of redundant pairs and groups of genes of identical or closely similar function, as well as variation in the degree of density of genetic information in different parts of the genome.
Collapse
Affiliation(s)
- M Riley
- Marine Biological Laboratory, Woods Hole, Massachusetts 02543
| |
Collapse
|
24
|
Fang H, Gennis RB. Identification of the transcriptional start site of the cyd operon from Escherichia coli. FEMS Microbiol Lett 1993; 108:237-42. [PMID: 8486248 DOI: 10.1111/j.1574-6968.1993.tb06105.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
The cydAB operon encodes the two subunits of the cytochrome bd ubiquinol oxidase from Escherichia coli. This enzyme is one of two terminal oxidases in the aerobic respiratory chain of E. coli. It has been demonstrated that expression of the cyd operon is transcriptionally regulated by oxygen via both the fnr and arcA gene products. Whereas arcA clearly serves as a positive regulator at low oxygen tension, there is no consensus concerning the role of the fnr gene product (FNR). In this paper, the transcriptional start site of the cyd operon is identified at position -287 with respect to the translational start. This is located 53 basepairs downstream from the center of dyad symmetry of the putative FNR recognition sequence.
Collapse
Affiliation(s)
- H Fang
- School of Chemical Sciences, University of Illinois, Urbana
| | | |
Collapse
|
25
|
|
26
|
Wall D, Delaney JM, Fayet O, Lipinska B, Yamamoto T, Georgopoulos C. arc-dependent thermal regulation and extragenic suppression of the Escherichia coli cytochrome d operon. J Bacteriol 1992; 174:6554-62. [PMID: 1328158 PMCID: PMC207623 DOI: 10.1128/jb.174.20.6554-6562.1992] [Citation(s) in RCA: 54] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
In a screen for Escherichia coli genes whose products are required for high-temperature growth, we identified and characterized a mini-Tn10 insertion that allows the formation of wild-type-size colonies at 30 degrees C but results in microcolony formation at 36 degrees C and above (Ts- phenotype). Mapping, molecular cloning, and DNA sequencing analyses showed that the mini-Tn10 insertion resides in the cydB gene, the distal gene of the cydAB operon (cytochrome d). The Ts- growth phenotype was also shown to be associated with previously described cyd alleles. In addition, all cyd mutants were found to be extremely sensitive to hydrogen peroxide. Northern (RNA) blot analysis showed that cyd-specific mRNA levels accumulate following a shift to high temperature. Interestingly, this heat shock induction of the cyd operon was not affected in an rpoH delta background but was totally absent in an arcA or arcB mutant background. Extragenic suppressors of the Cyd Ts- phenotype are found at approximately 10(-3). Two extragenic suppressors were shown to be null alleles in either arcA or arcB. One interpretation of our results is that in the absence of ArcA or ArcB, which are required for the repression of the cyo operon (cytochrome o), elevated levels of Cyo are produced, thus compensating for the missing cytochrome d function. Consistent with this interpretation, the presence of the cyo gene on a multicopy plasmid suppressed the Ts- and hydrogen peroxide-sensitive phenotypes of cyd mutants.
Collapse
Affiliation(s)
- D Wall
- Department of Cellular, Viral, and Molecular Biology, University of Utah Medical Center, Salt Lake City 84132
| | | | | | | | | | | |
Collapse
|
27
|
Weiner JH, Rothery RA, Sambasivarao D, Trieber CA. Molecular analysis of dimethylsulfoxide reductase: a complex iron-sulfur molybdoenzyme of Escherichia coli. BIOCHIMICA ET BIOPHYSICA ACTA 1992; 1102:1-18. [PMID: 1324728 DOI: 10.1016/0005-2728(92)90059-b] [Citation(s) in RCA: 104] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Affiliation(s)
- J H Weiner
- Department of Biochemistry, University of Alberta, Edmonton, Canada
| | | | | | | |
Collapse
|
28
|
Gündüz U, Elliott MS, Seubert PH, Houghton JA, Houghton PJ, Trewyn RW, Katze JR. Absence of tRNA-guanine transglycosylase in a human colon adenocarcinoma cell line. BIOCHIMICA ET BIOPHYSICA ACTA 1992; 1139:229-38. [PMID: 1378304 DOI: 10.1016/0925-4439(92)90139-e] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Queuosine (Q), found exclusively in the first position of the anticodons of tRNA(Asp), tRNA(Asn), tRNA(His) and tRNA(Tyr), is synthesized in eucaryotes by a base-for-base exchange of queuine, the base of Q, for guanine at tRNA position 34. This reaction is catalyzed by the enzyme tRNA-guanine transglycosylase (EC 2.4.2.29). We measured the specific release of queuine from Q-5'-phosphate (queuine salvage) and the extent of tRNA Q modification in 6 human tumors carried as xenografts in immune-deprived mice. Q-deficient tRNA was found in 3 of the tumors but it did not correlate with diminished queuine salvage. The low tRNA Q content of one tumor, the HxGC3 colon adenocarcinoma, prompted us to examine a HxGC3-derived cell line, GC3/M. GC3/M completely lacks Q in its tRNA and measurable tRNA-guanine transglycosylase activity; the first example of a higher eucaryotic cell which lacks this enzyme. Exposure of GC3/M cells to 5-azacytidine induces the transient appearance of Q-positive tRNA. This result suggests that at least one allele of the transglycosylase gene in GC3/M cells may have been inactivated by DNA methylation. In clinical samples, we found Q-deficient tRNA in 10 of 46 solid tumors, including 2 of 13 colonic carcinomas.
Collapse
Affiliation(s)
- U Gündüz
- Department of Microbiology and Immunology, University of Tennessee, Memphis 38163
| | | | | | | | | | | | | |
Collapse
|
29
|
Hemschemeier S, Grund M, Keuntje B, Eichenlaub R. Isolation of Escherichia coli mutants defective in uptake of molybdate. J Bacteriol 1991; 173:6499-506. [PMID: 1655715 PMCID: PMC208986 DOI: 10.1128/jb.173.20.6499-6506.1991] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
For the study of molybdenum uptake by Escherichia coli, we generated Tn5lac transposition mutants, which were screened for the pleiotropic loss of molybdoenzyme activities. Three mutants A1, A4, and M22 were finally selected for further analysis. Even in the presence of 100 microM molybdate in the growth medium, no active nitrate reductase, formate dehydrogenase, and trimethylamine-N-oxide reductase were detected in these mutants, indicating that the intracellular supply of molybdenum was not sufficient. This was also supported by the observation that introduction of plasmid pWK225 carrying the complete nif regulon of Klebsiella pneumoniae did not lead to a functional expression of nitrogenase. Finally, molybdenum determination by induced coupled plasma mass spectroscopy confirmed a significant reduction of cell-bound molybdenum in the mutants compared with that in wild-type E. coli, even at high molybdate concentrations in the medium. A genomic library established with the plasmid mini-F-derived cop(ts) vector pJE258 allowed the isolation of cosmid pBK229 complementing the molybdate uptake deficiency of the chlD mutant and the Tn5lac-induced mutants. Certain subfragments of pBK229 which do not contain the chlD gene are still able to complement the Tn5lac mutants. Mapping experiments showed that the Tn5lac insertions did not occur within the chromosomal region present in pBK229 but did occur very close to that region. We assume that the Tn5lac insertions have a polar effect, thus preventing the expression of transport genes, or that a positively acting regulatory element was inactivated.
Collapse
Affiliation(s)
- S Hemschemeier
- Gentechnologie/Mikrobiologie, Fakultät für Biologie, Universität Bielefeld, Germany
| | | | | | | |
Collapse
|
30
|
Reuter K, Slany R, Ullrich F, Kersten H. Structure and organization of Escherichia coli genes involved in biosynthesis of the deazaguanine derivative queuine, a nutrient factor for eukaryotes. J Bacteriol 1991; 173:2256-64. [PMID: 1706703 PMCID: PMC207776 DOI: 10.1128/jb.173.7.2256-2264.1991] [Citation(s) in RCA: 57] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
The plasmid pPR20 contains the gene tgt, which encodes tRNA guanine transglycosylase (Tgt), on a 33-kbp DNA insert from a region around 9 min on the Escherichia coli linkage map. The plasmid was subcloned to determine the sequence and organization of the tgt gene. Tgt is a unique enzyme that exchanges the guanine residue with 7-aminomethyl-7-deazaguanine in tRNAs with GU(N) anticodons. After this exchange, a cyclopentendiol moiety is attached to the 7-aminomethyl group of 7-deazaguanine, resulting in the hypermodified nucleoside queuosine (Q). Here we give the complete sequence of a 3,545-bp StuI-BamHI DNA fragment where we found the tgt gene and three previously unknown genes encoding proteins with calculated molecular masses of 42.5 (Tgt), 14, 39, and 12 kDa. The gene products were characterized on sodium dodecyl sulfate gels after synthesis in a combined transcription-translation system. The mRNA start sites of the open reading frames (ORFs) were determined by primer extension analysis. Plasmids containing the ORF encoding the 39-kDa protein (ORF 39) complemented a mutation in Q biosynthesis after the Tgt step. This gene was designated queA. The genes are arranged in the following order: ORF 14 (transcribed in the counterclockwise direction), queA, tgt, and ORF 12 (all transcribed in the clockwise direction). The organization of the promoter sequences and the termination sites suggests that queA, tgt, and ORF 12 are localized on a putative operon together with the genes secD and secF.
Collapse
Affiliation(s)
- K Reuter
- Institut für Biochemie, Universität Erlangen-Nürnberg, Germany
| | | | | | | |
Collapse
|
31
|
Fu HA, Iuchi S, Lin EC. The requirement of ArcA and Fnr for peak expression of the cyd operon in Escherichia coli under microaerobic conditions. MOLECULAR & GENERAL GENETICS : MGG 1991; 226:209-13. [PMID: 1851949 DOI: 10.1007/bf00273605] [Citation(s) in RCA: 89] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Transcriptional regulation of cyd, encoding the cytochrome d complex for O2 scavenging, was studied in Escherichia coli by monitoring phi(cyd-lac) expression under atmospheres containing 0-21% O2. Peak expression of this operon occurred under microaerobic conditions. Mutations in arcA (a trans-acting regulatory gene involved in aerobic respiration) greatly lowered phi(cyd-lac) expression under all conditions. Mutations in fnr (a trans-acting regulatory gene involved in anaerobic respiration) shifted the pattern of phi(cyd-lac) expression, lowering the microaerobic and aerobic expression. In an arcA-fnr double mutant, phi(cyd-lac) expression became insignificant, irrespective of the availability of O2. It thus appears that the expression of the phi(cyd-lac) operon is under dual control by the two pleiotropic activators, ArcA and Fnr, which interact to give the peak microaerobic expression.
Collapse
Affiliation(s)
- H A Fu
- Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, MA 02115
| | | | | |
Collapse
|
32
|
Unden G, Trageser M. Oxygen regulated gene expression in Escherichia coli: control of anaerobic respiration by the FNR protein. Antonie Van Leeuwenhoek 1991; 59:65-76. [PMID: 1854188 DOI: 10.1007/bf00445650] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Molecular oxygen is an important regulatory signal in facultative anaerobic bacteria and controls the expression of a great variety of genes positively or negatively. The expression of anaerobic respiration and of related functions of E. coli is controlled by the positive gene regulator FNR, which activates transcription in the absence of O2. The regulated genes carry a FNR consensus sequence upstream of the promoter. Under the same conditions FNR represses some of the genes of aerobic respiration. The binding to the DNA occurs by an alpha-helix-turn-alpha-helix DNA-binding domain. FNR contains 5 cysteine residues, four of which are arranged in a cluster close to the N-terminal end. For the function of FNR as a O2-dependent regulator three of the cysteine residues in the cluster and the residue outside the cluster are essential. FNR binds iron as a cofactor which most likely is involved in the O2-sensing by the protein. The experiments indicate that the cysteine residues are responsible for the binding of the iron. From the protein in vivo two functional states can be differentiated, an aerobic or metal-depleted form and an anaerobic form. Only the anaerobic form acts as a gene activator or repressor. Sensing of O2 or of positive redox potentials by the iron ion is thought to cause the conversion of the two functional states. The FNR protein in addition contains a potential nucleotide binding domain. The significance and function of this site is not clear.
Collapse
Affiliation(s)
- G Unden
- Institut für Biochemie, Heinrich-Heine-Universität, Düsseldorf, Germany
| | | |
Collapse
|
33
|
Cotter PA, Chepuri V, Gennis RB, Gunsalus RP. Cytochrome o (cyoABCDE) and d (cydAB) oxidase gene expression in Escherichia coli is regulated by oxygen, pH, and the fnr gene product. J Bacteriol 1990; 172:6333-8. [PMID: 2172211 PMCID: PMC526817 DOI: 10.1128/jb.172.11.6333-6338.1990] [Citation(s) in RCA: 208] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
The aerobic respiratory chain of Escherichia coli contains two terminal oxidases that catalyze the oxidation of ubiquinol-8 and the reduction of oxygen to water. They are the cytochrome o oxidase complex encoded by cyoABCDE and the cytochrome d oxidase complex encoded by cydAB. To determine how these genes are regulated in response to a variety of environmental stimuli, including oxygen, we examined their expression by using lacZ protein fusions in wild-type and fnr mutant strains of E. coli. Anaerobic growth resulted in a 140-fold repression of cyoA'-'lacZ expression relative to aerobic growth and a 3-fold increase in cydA'-'lacZ expression. Anaerobic repression of both fusions was mediated in part by the fnr gene product, as evidenced by a 30-fold derepression of cyoA'-'lacZ expression and a 4-fold derepression of cydA'-'lacZ expression in an fnr deletion strain. Supplying wild-type fnr in trans restored wild-type repression for both fusions. Fnr thus functions as an anaerobic repressor of both cyoABCDE and cydAB expression. Reduced-minus-oxidized difference spectrum analyses of cell membranes confirmed the effect of the fnr gene product on the production of cytochrome d oxidase in the cell. Based on the pattern of anaerobic cydAB expression observed, we propose the existence of a second, as yet unidentified, regulatory element that must function either to activate cydAB expression as oxygen becomes limiting or to repress cydAB expression aerobically. Whereas cytochrome o oxidase encoded by cyoABCDE appears to be produced only under oxygen-rich growth conditions, in keeping with its biochemical properties, cytochrome d oxidase is expressed moderately aerobically and is elevated yet further when oxygen becomes limiting so that the organism can cope better under oxygen starvation conditions. We also examined cyoABCDE and cydAB expression in response to growth on alternative carbon compounds and to changes in the culture medium pH and osmolarity.
Collapse
Affiliation(s)
- P A Cotter
- Department of Microbiology and Molecular Genetics, University of California, Los Angeles 90024-1489
| | | | | | | |
Collapse
|
34
|
Abstract
Bacteria which can grow in different environments have developed regulatory systems which allow them to exploit specific habitats to their best advantage. In the facultative anaerobe Escherichia coli two transcriptional regulators controlling independent networks of oxygen-regulated gene expression have been identified. One is a two-component sensor-regulator system (ArcB-A), which represses a wide variety of aerobic enzymes under anaerobic conditions. The other is FNR, the transcriptional regulator which is essential for expressing anaerobic respiratory processes. The purpose of this review is to summarize what is known about FNR. The fnr gene was initially defined by the isolation of some pleiotropic mutants which characteristically lacked the ability to use fumarate and nitrate as reducible substrates for supporting anaerobic growth and several other anaerobic respiratory functions. Its role as a transcriptional regulator emerged from genetic and molecular studies in which its homology with CRP (the cyclic AMP receptor protein which mediates catabolite repression) was established and has since been particularly important in identifying the structural basis of its regulatory specificities. FNR is a member of a growing family of CRP-related regulatory proteins which have a DNA-binding domain based on the helix-turn-helix structural motif, and a characteristic beta-roll that is involved in nucleotide-binding in CRP. The FNR protein has been isolated in a monomeric form (Mr 30,000) which exhibits a high but as yet non-specific affinity for DNA. Nevertheless, the DNA-recognition site and important residues conferring the functional specificity of FNR have been defined by site-directed mutagenesis. A consensus for the sequences that are recognized by FNR in the promoter regions of FNR-regulated genes, has likewise been identified. The basic features of the genes and operons regulated by FNR are reviewed, and examples in which FNR functions negatively as an anaerobic repressor as well as positively as an anaerobic activator, are included. Less is known about the way in which FNR senses anoxia and is thereby transformed into its 'active' form, but it seems likely that cysteine residues and possibly a metal ion are involved. Four of the five cysteine residues of FNR are clustered in an essential N-terminal 'domain' which is conserved in FNR and the HlyX protein of Actinobacillus pleuropneumoniae, but not in CRP or the FixK protein of Rhizobium meliloti. The relationships between FNR and other oxygen-related systems in E. coli are discussed, as well as parallel systems in other organisms.(ABSTRACT TRUNCATED AT 400 WORDS)
Collapse
Affiliation(s)
- S Spiro
- Department of Molecular Biology and Biotechnology, University of Sheffield, U.K
| | | |
Collapse
|