Queuosine modification in tRNA and expression of the nitrate reductase in Escherichia coli.

Jänel, G.; Michelsen, Uwe; Nishimura, Susumu; Kersten, H.

doi:10.1002/j.1460-2075.1984.tb02017.x

Cited by 17 publications

(5 citation statements)

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“…Previous findings that the two tgt mutants, in contrast to the corresponding tgt+ strains, are unable to synthesize the subunits of nitrate reductase when grown anaerobically were thought to be consequences of Q deficiency in specific tRNAs (16 (17).…”

Section: Discussionmentioning

confidence: 96%

“…Furthermore, the typical absorption maxima of cytochrome a1 and the cytochrome d complex are lacking in low-temperature reduced-minus-oxidized difference spectra of cytochromes in whole cells (16,18).…”

mentioning

confidence: 99%

“…Low-temperature difference spectra of cytochromes. Dithionite-reduced minus femcyanide-oxidized cytochrome spectra were taken in whole cells at the temperature of liquid nitrogen (77 K) in an Aminco DW-2UV/VJS spectrometer as described previously (16).…”

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confidence: 99%

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Mutations in the Escherichia coli fnr and tgt genes: control of molybdate reductase activity and the cytochrome d complex by fnr

et al. 1989

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In eubacteria, the tRNA transglycosylase (Tgt) in specific tRNAs exchanges a guanine in the anticodon for 7-aminomethyl-7-deazaguanine, which is finally converted to queuosine. The tgt gene of Escherichia coli has been mapped at 9 min on the genome, and mutant pairs containing an intact or mutated tgt allele were obtained after transduction of the tgt locus by P1 bacteriophages into a genetically defined E. coli strain (S. Noguchi, Y. Nishimura, Y. Hirota, and S. Nishimura, J. Biol. Chem. 257:6544 6550, 1982). These tgt mutants grew anerobicafly with fumarate as an electron acceptor, while nitrate or trimethylamine N-oxide could not be reduced. Furthermore, molybdate reductase activity was almost lacking and the characteristic absorption maxima, corresponding to cytochrome a, and the cytochrome d complex, were not detectable in lowtemperature reduced-minus-oxidized difference spectra in anaerobically grown cells. Transduction of the mutated tgt locus into another E. coli recipient resulted in tgt mutants without anaerobic defects. Transformation of the original tgt mutants with anfnr gene-containing plasmid reversed the anaerobic defects. Clearly, the original tgt mutants harbor a second mutation, affecting the anaerobic regulator protein Fnr. The results suggest that fnr is involved in anaerobic control of components of the cytochrome d complex and of the redox system that transfers electrons to molybdate. F' plasmids containing a fused lacI-lacZ gene with the nonsense codon UAG at different positions in the lacl part were transferred to E. coli strains with a mutated or nonmutated tgt locus but intact infnr. A twofold increase in the frequency of incorrect readthrough of the UAG codon, dependent on the codon context, was observed in the tgt mutant and is suggested to be caused by a tRNATYr with G in place of queuosine.Eseherichia coli mutants with a defined genetic background were isolated, containing or lacking the tRNA guanine transglycosylase (Tgt), and consequently containing or lacking queuosine (Q), 7-(((4,5-cis-dihydroxy-2-cyclopentene-1-yl)-amino)-methyl)-7-deazaguanosine, in tRNA (31).The transglycosylase enzyme catalyzes (in tRNAsGUN specific for Asn, Asp, His, and Tyr) the exchange of the guanine residue in the first position of the anticodon for 7-aminomethyl-7-deazaguanine, a precursor of Q (32, 33). The cyclopentenediol moiety of Q is then synthesized at the level of tRNA and involves epoxy-Q which is finally converted to Q by a cobamide-dependent enzyme system (7).Noguchi et al. (31) isolated tgt mutants by random screening from a collection of Escherichia coli K-12 mutants obtained by treatment with N-methyl-N'-nitrosoguanidine. tRNA was isolated from about 400 strains, and three mutants were found with respective tRNAs containing the anticodon GUN, where N is one of the canonical nucleosides. The defective gene, named tgt, was mapped at about 9 min on the E. coli chromosome, and the gene order was shown to be phoB tgt tsx. The tgt locus was transferred into E. coli ANLO5 (see Table 1) by P1 ba...

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Section: Discussionmentioning

confidence: 96%

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confidence: 99%

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Mutations in the Escherichia coli fnr and tgt genes: control of molybdate reductase activity and the cytochrome d complex by fnr

et al. 1989

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“…Various studies have purported to implicate DNA supercoiling (433), oxygen radicals (159), or the lack of certain modified transfer ribonucleic acids (43,180) as important NT 193, 295 a +, Efficient expression in an fnr background; -, reduced or negligible expression in an fnr background. NT, fnr effect not tested.…”

Section: Physiologymentioning

confidence: 99%

Nitrate respiration in relation to facultative metabolism in enterobacteria.

Stewart¹

1988

Microbiological Reviews

249

162

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“…The physiological importance of the Q modification is not fully understood. Although it is not essential in tested cells under normal conditions (4,(10)(11)(12)(13)(14), Q plays a role in regulation of translation, cell proliferation, stress response, and cell signaling (6,(15)(16)(17). Deficiency of Q-tRNA level correlates with diseases including tumor growth (reviewed in ref.…”

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Discovery of novel bacterial queuine salvage enzymes and pathways in human pathogens

Yuan

Zallot

Grove

et al. 2019

Proc. Natl. Acad. Sci. U.S.A.

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Queuosine (Q) is a complex tRNA modification widespread in eukaryotes and bacteria that contributes to the efficiency and accuracy of protein synthesis. Eukaryotes are not capable of Q synthesis and rely on salvage of the queuine base (q) as a Q precursor. While many bacteria are capable of Q de novo synthesis, salvage of the prokaryotic Q precursors preQ0 and preQ1 also occurs. With the exception of Escherichia coli YhhQ, shown to transport preQ0 and preQ1, the enzymes and transporters involved in Q salvage and recycling have not been well described. We discovered and characterized 2 Q salvage pathways present in many pathogenic and commensal bacteria. The first, found in the intracellular pathogen Chlamydia trachomatis, uses YhhQ and tRNA guanine transglycosylase (TGT) homologs that have changed substrate specificities to directly salvage q, mimicking the eukaryotic pathway. The second, found in bacteria from the gut flora such as Clostridioides difficile, salvages preQ1 from q through an unprecedented reaction catalyzed by a newly defined subgroup of the radical-SAM enzyme family. The source of q can be external through transport by members of the energy-coupling factor (ECF) family or internal through hydrolysis of Q by a dedicated nucleosidase. This work reinforces the concept that hosts and members of their associated microbiota compete for the salvage of Q precursors micronutrients.

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Queuosine modification in tRNA and expression of the nitrate reductase in Escherichia coli.

Abstract: In eubacteria the modified nucleoside queuosine is present in tRNAAsn, tRNAAP, tRNAHis and tRNATYr. A

Cited by 17 publications

References 29 publications

Mutations in the Escherichia coli fnr and tgt genes: control of molybdate reductase activity and the cytochrome d complex by fnr

Mutations in the Escherichia coli fnr and tgt genes: control of molybdate reductase activity and the cytochrome d complex by fnr

Nitrate respiration in relation to facultative metabolism in enterobacteria.

Discovery of novel bacterial queuine salvage enzymes and pathways in human pathogens

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