Effects of a Diet Deficient in Tyrosine and Queuine on Germfree Mice

Marks, Thomas A.; Farkas, Walter R.

doi:10.1006/bbrc.1996.5768

Cited by 53 publications

(51 citation statements)

References 28 publications

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“…QueA Activity Assays-Routine assays of QueA activity were initially carried out in 100 mM Tris-HCl (pH 8.7), 50 mM KCl, 10 mM MgCl 2 , 0.5 mM DTT, 25 g of crude preQ 1 -tRNA Tyr , and 50 M [U-ribosyl- 14 C]AdoMet in a final volume of 50 l at 37°C. Reactions were terminated at the appropriate times by the addition of 3 volumes of cold 10% trichloroacetic acid, and the precipitated tRNA was collected on Whatman GF-B filters by vacuum filtration, rinsed with cold 5% trichloroacetic acid followed by ethanol, and dried, and the radioactivity was quantitated by liquid scintillation counting.…”

Section: Construction Of a Homologous Overexpression System For E Comentioning

confidence: 99%

“…Reactions were terminated at the appropriate times by the addition of 3 volumes of cold 10% trichloroacetic acid, and the precipitated tRNA was collected on Whatman GF-B filters by vacuum filtration, rinsed with cold 5% trichloroacetic acid followed by ethanol, and dried, and the radioactivity was quantitated by liquid scintillation counting. After optimum conditions for enzyme activity were elucidated, routine assays were carried out in 100 mM glygly (pH 8.7), 100 mM EDTA, 100 mM KCl, 0.5 mM DTT, 3.75 M preQ 1 -tRNA Tyr , and 100 M [U-ribosyl- 14 C]AdoMet in a final volume of 50 l at 37°C. Activity assays were initiated and terminated as described above.…”

Section: Construction Of a Homologous Overexpression System For E Comentioning

confidence: 99%

“…A definitive picture of the biochemical function or functions of queuosine has yet to emerge, but it has been correlated with eukaryotic cell development and proliferation (7)(8)(9)(10), neoplastic transformation (8,(11)(12)(13), tyrosine biosynthesis in animals (14), translational frameshifts essential to retroviral protein biosynthesis (15)(16)(17), and the ability of pathogenic bacteria to invade and proliferate in human tissue (18). Underlying most, if not all, of these phenomena is a role in modulating translational fidelity, consistent with the location of queuosine in the anticodon.…”

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confidence: 99%

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tRNA Modification by S-Adenosylmethionine:tRNA Ribosyltransferase-Isomerase

Lanen

Kinzie

Matthieu

et al. 2003

Journal of Biological Chemistry

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The enzyme S-adenosylmethionine:tRNA ribosyltransferase-isomerase catalyzes the penultimate step in the biosynthesis of the hypermodified tRNA nucleoside queuosine (Q), an unprecedented ribosyl transfer from the cofactor S-adenosylmethionine (AdoMet) to a modified-tRNA precursor to generate epoxyqueuosine (oQ). The complexity of the reaction makes it an especially interesting mechanistic problem, and as a foundation for detailed kinetic and mechanistic studies we have carried out the basic characterization of the enzyme. Importantly, to allow for the direct measurement of oQ formation, we have developed protocols for the preparation of homogeneous substrates; specifically, an overexpression system was constructed for tRNA Tyr in an E. coli queA deletion mutant to allow for the isolation of large quantities of substrate tRNA, and [U-ribosyl-14 C]AdoMet was synthesized. The enzyme shows optimal activity at pH 8.7 in buffers containing various oxyanions, including acetate, carbonate, EDTA, and phosphate. Unexpectedly, the enzyme was inhibited by Mg 2؉and Mn 2؉ in millimolar concentrations. The steady-state kinetic parameters were determined to be K m AdoMet ‫؍‬ 101.4 M, K m tRNA ‫؍‬ 1.5 M, and k cat ‫؍‬ 2.5 min ؊1 . A short minihelix RNA was synthesized and modified with the precursor 7-aminomethyl-7-deazaguanine, and this served as an efficient substrate for the enzyme (K m RNA ‫؍‬ 37.7 M and k cat ‫؍‬ 14.7 min ؊1 ), demonstrating that the anticodon stem-loop is sufficient for recognition and catalysis by QueA.

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Section: Construction Of a Homologous Overexpression System For E Comentioning

confidence: 99%

Section: Construction Of a Homologous Overexpression System For E Comentioning

confidence: 99%

mentioning

confidence: 99%

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tRNA Modification by S-Adenosylmethionine:tRNA Ribosyltransferase-Isomerase

Lanen

Kinzie

Matthieu

et al. 2003

Journal of Biological Chemistry

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“…This loss is caused by mistranslation of virF, a transcription factor responsible for up-regulation of a suite of virulence-associated proteins (Durand et al, 2000). Similarly, Q is essential in the biosynthesis of tyrosine in animals by its preventing a (Q À )-tRNA-dependent mistranslation of mRNA coding for the tyrosine-biosynthesis enzyme phenylalanine hydroxylase (Marks & Farkas, 1997).…”

Section: Introductionmentioning

confidence: 99%

Crystallization and preliminary X-ray characterization of the nitrile reductase QueF: a queuosine-biosynthesis enzyme

et al. 2005

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QueF (MW = 19.4 kDa) is a recently characterized nitrile oxidoreductase which catalyzes the NADPH-dependent reduction of 7-cyano-7-deazaguanine (preQ 0 ) to 7-aminomethyl-7-deazaguanine, a late step in the biosynthesis of the modified tRNA nucleoside queuosine. Initial crystals of homododecameric Bacillus subtilis QueF diffracted poorly to 8.0 Å . A three-dimensional model based on homology with the tunnel-fold enzyme GTP cyclohydrolase I suggested catalysis at intersubunit interfaces and a potential role for substrate binding in quaternary structure stabilization. Guided by this insight, a second crystal form was grown that was strictly dependent on the presence of preQ 0 . This crystal form diffracted to 2.25 Å resolution.

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“…Q is based on a very unusual 7-deazaguanosine core, which is further modified by addition of a cyclopentendiol ring (5,6). The Q modification has long been known and has been implicated in a number of disparate physiological phenomena, such as eukaryotic cell proliferation and differentiation (7)(8)(9)(10), tyrosine biosynthesis (11), and bacterial virulence (12). However, despite the presence of Q in the tRNA anticodon loop, no definitive role for Q in translation has been established (13).…”

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confidence: 99%

Identification of Four Genes Necessary for Biosynthesis of the Modified Nucleoside Queuosine

Reader

Metzgar

Schimmel

et al. 2004

Journal of Biological Chemistry

138

134

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Queuosine (Q) is a hypermodified 7-deazaguanosine nucleoside located in the anticodon wobble position of four amino acid-specific tRNAs. In bacteria, Q is produced de novo from GTP via the 7-deazaguanosine precursor preQ 1 (7-aminoethyl 7-deazaguanine) by an uncharacterized pathway. PreQ 1 is subsequently transferred to its specific tRNA by a tRNA-guanine transglycosylase (TGT) and then further modified in situ to produce Q. Here we use comparative genomics to implicate four gene families (best exemplified by the B. subtilis operon ykvJKLM) as candidates in the preQ 1 biosynthetic pathway. Deletions were constructed in genes for each of the four orthologs in Acinetobacter. High pressure liquid chromatography analysis showed the Q nucleoside was absent from the tRNAs of each of four deletion strains. Electrospray ionization mass spectrometry confirmed the absence of Q in each mutant strain. Finally, introduction of the Bacillus subtilis ykvJKLM operon in trans complemented the Q deficiency of the two deletion mutants that were tested. Thus, the products of these four genes (named queC, -D, -E, and -F) are essential for the Q biosynthetic pathway.Nucleoside modification typically occurs in ϳ10% of the nucleosides of a particular tRNA but can involve as many as 25% of the nucleosides for a specific tRNA (1). Over 80 modified nucleosides have been characterized (1), many of which are phylogenetically conserved. The nature of nucleoside modification varies from simple methylation of the base or ribose ring to extensive "hypermodification" of the canonical bases. The latter involves multiple enzymatic steps and can result in substantive structural changes (2). Queuosine (Q) 1 is an example of a highly modified nucleoside located in the anticodon wobble position 34 of tRNAs specific for Tyr, His, Asp, and Asn (3). With few exceptions (such as yeast and mycoplasma), it is widely distributed in most prokaryotic and eukaryotic phyla (4). Q is based on a very unusual 7-deazaguanosine core, which is further modified by addition of a cyclopentendiol ring (5, 6). The Q modification has long been known and has been implicated in a number of disparate physiological phenomena, such as eukaryotic cell proliferation and differentiation (7-10), tyrosine biosynthesis (11), and bacterial virulence (12). However, despite the presence of Q in the tRNA anticodon loop, no definitive role for Q in translation has been established (13).Unlike eukaryotes that import the queuine base, bacteria synthesize Q modification de novo from a GTP starting block (14). The first stage of synthesis gives 7-cyano-7-deazaguanosine (preQ 0 ) that is then further modified into 7-aminoethyl 7-deazaguanine (preQ 1 ) (Fig. 1). The preQ 1 base is subsequently transferred to the appropriate tRNA in a guanine-exchange reaction catalyzed by a tRNA-guanine transglycosylase (TGT) (15). It is then further modified in situ to give Q (16). A second 7-deazaguanosine tRNA modification, archaeosine, is found in all archaeal tRNAs at position 15 of the D-loop (17). Archa...

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Effects of a Diet Deficient in Tyrosine and Queuine on Germfree Mice

Cited by 53 publications

References 28 publications

tRNA Modification by S-Adenosylmethionine:tRNA Ribosyltransferase-Isomerase

tRNA Modification by S-Adenosylmethionine:tRNA Ribosyltransferase-Isomerase

Crystallization and preliminary X-ray characterization of the nitrile reductase QueF: a queuosine-biosynthesis enzyme

Identification of Four Genes Necessary for Biosynthesis of the Modified Nucleoside Queuosine

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