Differential heterocyclic substrate recognition by, and pteridine inhibition of E. coli and human tRNA-guanine transglycosylases

Thomas, Charles E.; Chen, Yi‐Chen; Garcia, George A.

doi:10.1016/j.bbrc.2011.05.100

Cited by 4 publications

(4 citation statements)

References 21 publications

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“…Kinetic analysis of the human QTRT enzyme has shown that it exhibits similar K M and k cat values for both guanine and queuine as substrate ( 4 , 42 ), raising the question of how the enzyme exercises selectivity for the correct substrate. This anomaly has previously been explained by the irreversible nature of queuine-incorporation, which differs from guanine, which can be reversibly displaced after tRNA insertion ( 20 ).…”

Section: Discussionmentioning

confidence: 99%

The human tRNA-guanine transglycosylase displays promiscuous nucleobase preference but strict tRNA specificity

Fergus

Alqasem

Cotter

et al. 2021

Nucleic Acids Research

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Base-modification can occur throughout a transfer RNA molecule; however, elaboration is particularly prevalent at position 34 of the anticodon loop (the wobble position), where it functions to influence protein translation. Previously, we demonstrated that the queuosine modification at position 34 can be substituted with an artificial analogue via the queuine tRNA ribosyltransferase enzyme to induce disease recovery in an animal model of multiple sclerosis. Here, we demonstrate that the human enzyme can recognize a very broad range of artificial 7-deazaguanine derivatives for transfer RNA incorporation. By contrast, the enzyme displays strict specificity for transfer RNA species decoding the dual synonymous NAU/C codons, determined using a novel enzyme-RNA capture-release method. Our data highlight the broad scope and therapeutic potential of exploiting the queuosine incorporation pathway to intentionally engineer chemical diversity into the transfer RNA anticodon.

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Section: Discussionmentioning

confidence: 99%

The human tRNA-guanine transglycosylase displays promiscuous nucleobase preference but strict tRNA specificity

Fergus

Alqasem

Cotter

et al. 2021

Nucleic Acids Research

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“…The side chain of the valine residue corresponding to Cys158 of Z. mobilis Tgt appears at a position where it might form an interaction with the dihydroxy-cyclopentenyl substituent. While Cys158 and Val233 are highly conserved in bacterial Tgt, the corresponding valine and glycine residues are invariant in all eucaryotic Tgt catalytic subunits whose sequences have been determined so far [42].…”

Section: Discussionmentioning

confidence: 99%

“…Accordingly, the side chain conformation of Thr159 induced upon preQ 1 binding may well be correlated with the reduced preQ 1 affinity observed upon mutation of Cys158 to valine. It should be noted, that Thr159 is in most eucaryotic Tgt catalytic subunits replaced by a nearly isosteric valine residue [42].…”

Section: Discussionmentioning

confidence: 99%

Investigation of Specificity Determinants in Bacterial tRNA-Guanine Transglycosylase Reveals Queuine, the Substrate of Its Eucaryotic Counterpart, as Inhibitor

et al. 2013

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Bacterial tRNA-guanine transglycosylase (Tgt) catalyses the exchange of the genetically encoded guanine at the wobble position of tRNAsHis,Tyr,Asp,Asn by the premodified base preQ1, which is further converted to queuine at the tRNA level. As eucaryotes are not able to synthesise queuine de novo but acquire it through their diet, eucaryotic Tgt directly inserts the hypermodified base into the wobble position of the tRNAs mentioned above. Bacterial Tgt is required for the efficient pathogenicity of Shigella sp, the causative agent of bacillary dysentery and, hence, it constitutes a putative target for the rational design of anti-Shigellosis compounds. Since mammalian Tgt is known to be indirectly essential to the conversion of phenylalanine to tyrosine, it is necessary to create substances which only inhibit bacterial but not eucaryotic Tgt. Therefore, it seems of utmost importance to study selectivity-determining features within both types of proteins. Homology models of Caenorhabditis elegans Tgt and human Tgt suggest that the replacement of Cys158 and Val233 in bacterial Tgt (Zymomonas mobilis Tgt numbering) by valine and accordingly glycine in eucaryotic Tgt largely accounts for the different substrate specificities. In the present study we have created mutated variants of Z. mobilis Tgt in order to investigate the impact of a Cys158Val and a Val233Gly exchange on catalytic activity and substrate specificity. Using enzyme kinetics and X-ray crystallography, we gained evidence that the Cys158Val mutation reduces the affinity to preQ1 while leaving the affinity to guanine unaffected. The Val233Gly exchange leads to an enlarged substrate binding pocket, that is necessary to accommodate queuine in a conformation compatible with the intermediately covalently bound tRNA molecule. Contrary to our expectations, we found that a priori queuine is recognised by the binding pocket of bacterial Tgt without, however, being used as a substrate.

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“…In culture, pterin was found to inhibit the formation of aspartyl Q-tRNA in mouse fibroblasts ( K i ~1 μM) [ 44 ]. More recently the inhibition of human queuine-insertase by biopterin was evaluated, yielding a K i of 8.9 μM [ 116 ]. Being an order of magnitude above the K m value for queuine (260 nM), this data would suggest that biopterin is not a particularly potent inhibitor of the enzyme [ 116 ].…”

Section: Queuine and Queuosine In Metabolism Development And Aginmentioning

confidence: 99%

The Queuine Micronutrient: Charting a Course from Microbe to Man

et al. 2015

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Micronutrients from the diet and gut microbiota are essential to human health and wellbeing. Arguably, among the most intriguing and enigmatic of these micronutrients is queuine, an elaborate 7-deazaguanine derivative made exclusively by eubacteria and salvaged by animal, plant and fungal species. In eubacteria and eukaryotes, queuine is found as the sugar nucleotide queuosine within the anticodon loop of transfer RNA isoacceptors for the amino acids tyrosine, asparagine, aspartic acid and histidine. The physiological requirement for the ancient queuine molecule and queuosine modified transfer RNA has been the subject of varied scientific interrogations for over four decades, establishing relationships to development, proliferation, metabolism, cancer, and tyrosine biosynthesis in eukaryotes and to invasion and proliferation in pathogenic bacteria, in addition to ribosomal frameshifting in viruses. These varied effects may be rationalized by an important, if ill-defined, contribution to protein translation or may manifest from other presently unidentified mechanisms. This article will examine the current understanding of queuine uptake, tRNA incorporation and salvage by eukaryotic organisms and consider some of the physiological consequence arising from deficiency in this elusive and lesser-recognized micronutrient.

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Differential heterocyclic substrate recognition by, and pteridine inhibition of E. coli and human tRNA-guanine transglycosylases

Cited by 4 publications

References 21 publications

The human tRNA-guanine transglycosylase displays promiscuous nucleobase preference but strict tRNA specificity

The human tRNA-guanine transglycosylase displays promiscuous nucleobase preference but strict tRNA specificity

Investigation of Specificity Determinants in Bacterial tRNA-Guanine Transglycosylase Reveals Queuine, the Substrate of Its Eucaryotic Counterpart, as Inhibitor

The Queuine Micronutrient: Charting a Course from Microbe to Man

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