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![Glutaminase activity of TgtA2 from M. jannaschii (MJ1022). A, glutaminase activity as a function of MjTgtA2 (2.0 –20 g). Assays contained 100 mM Hepes (pH 7.0), 0.5 M NaCl, 15 mM MgCl 2 , 2 mM DTT, 12.4 M L-[U-14 C]Gln, and 50 M preQ 0 -tRNA Ser . B, pH profile of MjTgtA2 glutaminase activity; reaction conditions were 100 mM Tris/Mes/acetate at the designated pH, 0.5 M NaCl, 20 mM MgCl 2 , 1 mM DTT, 10 M [U-14 C]Gln, 50 M preQ 0 -tRNA Ser , and 7.8 g of MjTgtA2. C, temperature profile for MjTgtA2 glutaminase activity; reactions were carried out in 100 mM Hepes (pH 7.0), 0.5 M NaCl, 20 mM MgCl 2 , 1 mM DTT, 10 M [U-14 C]Gln, 50 M preQ 0 -tRNA Ser , and 7.8 g of MjTgtA2.](profile/Vimbai-Chikwana/publication/41404856/figure/fig2/AS:408032497422338@1474293937238/Glutaminase-activity-of-TgtA2-from-M-jannaschii-MJ1022-A-glutaminase-activity-as-a.png)
Glutaminase activity of TgtA2 from M. jannaschii (MJ1022). A, glutaminase activity as a function of MjTgtA2 (2.0 –20 g). Assays contained 100 mM Hepes (pH 7.0), 0.5 M NaCl, 15 mM MgCl 2 , 2 mM DTT, 12.4 M L-[U-14 C]Gln, and 50 M preQ 0 -tRNA Ser . B, pH profile of MjTgtA2 glutaminase activity; reaction conditions were 100 mM Tris/Mes/acetate at the designated pH, 0.5 M NaCl, 20 mM MgCl 2 , 1 mM DTT, 10 M [U-14 C]Gln, 50 M preQ 0 -tRNA Ser , and 7.8 g of MjTgtA2. C, temperature profile for MjTgtA2 glutaminase activity; reactions were carried out in 100 mM Hepes (pH 7.0), 0.5 M NaCl, 20 mM MgCl 2 , 1 mM DTT, 10 M [U-14 C]Gln, 50 M preQ 0 -tRNA Ser , and 7.8 g of MjTgtA2.
Source publication
The presence of the 7-deazaguanosine derivative archaeosine (G+) at position 15 in tRNA is one of the diagnostic molecular characteristics of the Archaea. The biosynthesis of this modified
nucleoside is especially complex, involving the initial production of 7-cyano-7-deazaguanine (preQ0), an advanced precursor that is produced in a tRNA-independen...
Contexts in source publication
Context 1
... Assays were initially run in the absence of preQ 0 -tRNA in the presence or absence of ATP for 10 min over a pH range of 4.0 -9.0 and a temperature range of 30 -80 °C. Glutamate formation in the MjTgtA2 reaction, as deduced from glutamate dehydrogenase activity or from the direct pro- duction of L-[U-14 C]glutamate, was dependent on MjTgtA2 (Fig. 3A), did not require ATP, and was observed over a broad pH range (pH 5.0 -8.0) (Fig. 3B). Surprisingly, maximal activity occurred at 40 °C and dropped off significantly above 45 °C at all pH values (Fig. 3C). Based on radiochemical assays, specific activities of 7.7, 11.4, and 16.3 M/min/mg were calculated for the self-cleaved protein, the ...
Context 2
... of ATP for 10 min over a pH range of 4.0 -9.0 and a temperature range of 30 -80 °C. Glutamate formation in the MjTgtA2 reaction, as deduced from glutamate dehydrogenase activity or from the direct pro- duction of L-[U-14 C]glutamate, was dependent on MjTgtA2 (Fig. 3A), did not require ATP, and was observed over a broad pH range (pH 5.0 -8.0) (Fig. 3B). Surprisingly, maximal activity occurred at 40 °C and dropped off significantly above 45 °C at all pH values (Fig. 3C). Based on radiochemical assays, specific activities of 7.7, 11.4, and 16.3 M/min/mg were calculated for the self-cleaved protein, the full fusion protein, and the C-ter- minal tagged protein, ...
Context 3
... reaction, as deduced from glutamate dehydrogenase activity or from the direct pro- duction of L-[U-14 C]glutamate, was dependent on MjTgtA2 (Fig. 3A), did not require ATP, and was observed over a broad pH range (pH 5.0 -8.0) (Fig. 3B). Surprisingly, maximal activity occurred at 40 °C and dropped off significantly above 45 °C at all pH values (Fig. 3C). Based on radiochemical assays, specific activities of 7.7, 11.4, and 16.3 M/min/mg were calculated for the self-cleaved protein, the full fusion protein, and the C-ter- minal tagged protein, ...
Context 4
... Analysis of the TgtA2 Family-Analytical gel fil- tration of both the Trx-His 6 fusion and the protein produced from self-cleavage exhibited elution times consistent with the molecular mass of a dimer (154 and 122 kDa, respectively) (supplemental Text S2 and supplemental Fig. S3), demonstrat- ing that like arcTGT (12), TgtA2 also functions as a dimer. To obtain a more comprehensive understanding of TgtA2 pro- teins, we analyzed TgtA2 sequences in 36 Archaea. Based on ClustalW alignment of 50 TgtA2 sequences, three forms of TgtA2 proteins can be distinguished (supplemental Fig. S1). The first is a long form ...
Citations
... PreQ 0 is directly inserted in tRNA in archaea by arcTGT, where it is further modified into G + . The distant TGT paralog, ArcS ( 21 ), as well as Ga t-QueC , a fusion protein of QueC and a glutamine amidotr ansfer ase ( 22 ), and QueF-L, a paralog of the unimodular QueF that lacks the NADPH-dependent reduction acti vity ( 22 , 23 ), hav e been found as interchangeable proteins for this reaction. ...
... We belie v ed that its ArcS e volv ed to re v ert preQ 0 into CDG. To inv estigate this, we aligned STSV-2 ArcS sequence with canonical ArcS proteins ( 21 ) and with homologs previously identified in other viruses ( 7 ) (Alignment S5). The phage / virus ArcS corresponds to only the core catalytic domain of the canonical ArcS (PF17884.4 ...
... annotated as DUF5591, 99.9% similar for STSV2 16 encoded by Sulfolobus virus STSV2, Supplementary Data S17, and 99.9% for VPFG 00169 encoded by Vibrio phage nt-1, Supplementary Data S18). It has previously been demonstra ted tha t the ArcS have a high degree of di v ersity ( 21 ). Initially, four domains were identified in ArcS (Nt, C1, C2 and PUA). ...
Bacteriophages and bacteria are engaged in a constant arms race, continually evolving new molecular tools to survive one another. To protect their genomic DNA from restriction enzymes, the most common bacterial defence systems, double-stranded DNA phages have evolved complex modifications that affect all four bases. This study focuses on modifications at position 7 of guanines. Eight derivatives of 7-deazaguanines were identified, including four previously unknown ones: 2′-deoxy-7-(methylamino)methyl-7-deazaguanine (mdPreQ1), 2′-deoxy-7-(formylamino)methyl-7-deazaguanine (fdPreQ1), 2′-deoxy-7-deazaguanine (dDG) and 2′-deoxy-7-carboxy-7-deazaguanine (dCDG). These modifications are inserted in DNA by a guanine transglycosylase named DpdA. Three subfamilies of DpdA had been previously characterized: bDpdA, DpdA1, and DpdA2. Two additional subfamilies were identified in this work: DpdA3, which allows for complete replacement of the guanines, and DpdA4, which is specific to archaeal viruses. Transglycosylases have now been identified in all phages and viruses carrying 7-deazaguanine modifications, indicating that the insertion of these modifications is a post-replication event. Three enzymes were predicted to be involved in the biosynthesis of these newly identified DNA modifications: 7-carboxy-7-deazaguanine decarboxylase (DpdL), dPreQ1 formyltransferase (DpdN) and dPreQ1 methyltransferase (DpdM), which was experimentally validated and harbors a unique fold not previously observed for nucleic acid methylases.
... In archaea, preQ 0 serves as a substrate for tRNA-guanine transglycosylase, which catalyzes the exchange of guanine at position 15 for preQ 0 (100). In most Euryarchaeota, including methanogens, preQ 0 -tRNA is then converted to G 1 -tRNA by archaeosine synthase (ArcS), of which the enzyme from M. jannaschii has been investigated in vitro (101). While it was originally thought that ArcS alone synthesizes G 1 from PreQ 0 , it was recently shown that some Euryarchaeota, including M. acetivorans, utilize a complex consisting of ArcS and the radical SAM enzyme for archaeosine formation (RaSEA) (102). ...
... Virtually all sequenced Euryarchaeota contain homologs of both ArcS and RaSEA; thus, this may be the main pathway for G 1 synthesis in these organisms (102). In the future, further biochemical and structural studies of ArcS/RaSEA should be carried out to elucidate the mechanistic details of the reaction and to clarify the dependence of ArcS on a radical SAM partner since in vitro experiments with ArcS from M. jannaschii showed that the enzyme alone can produce G 1 from preQ 0 (101). ...
Radical S-adenosylmethionine (SAM) enzymes catalyze an impressive variety of difficult biochemical reactions in various pathways across all domains of life. These metalloenzymes employ a reduced [4Fe-4S] cluster and SAM to generate a highly reactive 5'-deoxyadenosyl radical that is capable of initiating catalysis on otherwise unreactive substrates. Interestingly, the genomes of methanogenic archaea encode many unique radical SAM enzymes with underexplored or completely unknown functions. These organisms are responsible for the yearly production of nearly 1 billion tons of methane, a potent greenhouse gas as well as a valuable energy source. Thus, understanding the details of methanogenic metabolism and elucidating the functions of essential enzymes in these organisms can provide insights into strategies to decrease greenhouse gas emissions as well as inform advances in bioenergy production processes. This minireview provides an overview of the current state of the field regarding the functions of radical SAM enzymes in methanogens and discusses gaps in knowledge that should be addressed.
... Additionally, it is still unknown whether dADG of MED16 is synthesized and incorporated into DNA during replication or if is it modified after replication. In archaea, preQ 0 is directly incorporated into tRNA by arcTGT before being further modified by the amidotransferases ArcS, GatQueC, or QueF-L [72][73][74]. In bacteria, preQ 0 is reduced to 7-aminomethyl-7-deazaguanine (preQ 1 ) by QueF [75] before TGT incorporates it in tRNA [76], where it is further modified to Q in two steps [77][78][79]. ...
A novel siphovirus, vB_PagS_MED16 (MED16) was isolated in Lithuania using Pantoea agglomerans strain BSL for the phage propagation. The double-stranded DNA genome of MED16 (46,103 bp) contains 73 predicted open reading frames (ORFs) encoding proteins, but no tRNA. Our comparative sequence analysis revealed that 26 of these ORFs code for unique proteins that have no reliable identity when compared to database entries. Based on phylogenetic analysis, MED16 represents a new genus with siphovirus morphology. In total, 35 MED16 ORFs were given a putative functional annotation, including those coding for the proteins responsible for virion morphogenesis, phage–host interactions, and DNA metabolism. In addition, a gene encoding a preQ0 DNA deoxyribosyltransferase (DpdA) is present in the genome of MED16 and the LC–MS/MS analysis indicates 2′-deoxy-7-amido-7-deazaguanosine (dADG)-modified phage DNA, which, to our knowledge, has never been experimentally validated in genomes of Pantoea phages. Thus, the data presented in this study provide new information on Pantoea-infecting viruses and offer novel insights into the diversity of DNA modifications in bacteriophages.
... Q34 can also be further modified to contain a glutamine (GluQ) moiety via the bacterial GluQRS enzyme (Campanacci et al., 2004;Ehrenhofer-Murray, 2017;Salazar, Ambrogelly, Crain, McCloskey, & Soll, 2004). In some archaeal species, preQ 0 is incorporated into a tRNA molecule at G15 and subsequently modified to become G + 15 by the enzymatic complex consisting of the ArcS/arcTGT enzyme and the RaSEA enzyme (Mohammad et al., 2017;Phillips et al., 2010;Yokogawa et al., 2019). However, numerous Crenarchaeota species lack ArcS and could instead form G + with either the GAT-QueC or QueF-like protein families (Phillips et al., 2012). ...
The chemical identity of RNA molecules beyond the four standard ribonucleosides has fascinated scientists since pseudouridine was characterized as the “fifth” ribonucleotide in 1951. Since then, the ever‐increasing number and complexity of modified ribonucleosides have been found in viruses and throughout all three domains of life. Such modifications can be as simple as methylations, hydroxylations, or thiolations, complex as ring closures, glycosylations, acylations, or aminoacylations, or unusual as the incorporation of selenium. While initially found in transfer and ribosomal RNAs, modifications also exist in messenger RNAs and noncoding RNAs. Modifications have profound cellular outcomes at various levels, such as altering RNA structure or being essential for cell survival or organism viability. The aberrant presence or absence of RNA modifications can lead to human disease, ranging from cancer to various metabolic and developmental illnesses such as Hoyeraal–Hreidarsson syndrome, Bowen–Conradi syndrome, or Williams–Beuren syndrome. In this review article, we summarize the characterization of all 143 currently known modified ribonucleosides by describing their taxonomic distributions, the enzymes that generate the modifications, and any implications in cellular processes, RNA structure, and disease. We also highlight areas of active research, such as specific RNAs that contain a particular type of modification as well as methodologies used to identify novel RNA modifications.
This article is categorized under:
• RNA Processing > RNA Editing and Modification
Abstract
Adenosine, guanosine, cytidine, and uridine can be modified at various positions (red) with a myriad of functional groups (outside circle).
... PreQ 0 is the point of divergence in the bacterial and archaeal pathways, with preQ 0 serving as the substrate for the enzyme tRNA-guanine transglycosylase (aTGT in Archaea, also known as 7-cyano-7-deazaguanine tRNA-ribosyltransferase), which catalyzes the exchange of the genetically encoded guanine-15 for preQ 0 in archaeal tRNA. The preQ 0 -modified tRNA is converted to G ϩ -modified tRNA by the action of either ArcS (32), QueF-L (33), or GAT-QueC (34), depending on the organism. In Bacteria, preQ 0 is first reduced to preQ 1 (35) before being inserted into specific bacterial tRNA at position 34 (the wobble position) by a bacterial tRNA-guanine transglycosylase (bTGT) (23) and further elaborated to Q-modified tRNA (36)(37)(38). ...
... A portion of the tRNA Gln transcript was then reacted in vitro with recombinant aTGT (Fig. 1) from Methanocaldococcus jannaschii (50) to replace the genetically encoded G at position 15 with preQ 0 . A portion of the preQ 0 -modified tRNA was then further reacted with recombinant M. jannaschii ArcS (32) to produce G ϩ -modified tRNA (Fig. 1). Quantitation of preQ 0 incorporation and subsequent conversion to G ϩ was carried out as described in Materials and Methods, and the modification state of the tRNA was confirmed by HPLC (see Fig. S5 in the supplemental material). ...
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.
... The biosynthesis pathway of G + has been reported [9][10][11][12][13][14][15][16][17][18][19] . First, ArcTGT catalyzes the exchange of the guanine base at the 15th position of a tRNA (G15-tRNA) for preQ 0 to synthesize preQ 0nucleoside 15-tRNA (q 0 N15-tRNA). ...
... Phillips et al. reported that a paralog of arcTGT, which encodes archaeosine synthase (ArcS), is involved in the G + formation, which they determined by means of disruption of the arcS ortholog in Haloferax volcanii (KEGG accession HVO_2008; https://www.genome.jp/ kegg/) and in vitro G + synthesis using glutamine and recombinant Methanocaldococcus jannaschii ArcS (MjArcS; KEGG accession MJ_1022) 15 . Although an arcS ortholog is found in almost all euryarchaeal species, it is not conserved in Crenarchaeota. ...
... This observation suggested that the ε-amino group of lysine is added to the cyano group of the preQ 0 base. To confirm this structure, we tried to prepare preQ 0 [ 13 C, 15 N]Lysnucleotide and measure its 13 C NMR spectrum. About 100 µg of enzymatically synthesized preQ 0 [ 13 C, 15 N]Lys-nucleotide was purified from 15 mg of M. acetivorans tRNA Mete I transcript treated with recombinant MaArcTGT, MaArcS and nuclease P 1 ( Supplementary Fig. 4a,b). ...
Archaeosine (G⁺), 7-formamidino-7-deazaguanosine, is an archaea-specific modified nucleoside found at the 15th position of tRNAs. In Euryarchaeota, 7-cyano-7-deazaguanine (preQ0)-containing tRNA (q0N-tRNA), synthesized by archaeal tRNA-guanine transglycosylase (ArcTGT), has been believed to be converted to G⁺-containing tRNA (G⁺-tRNA) by the paralog of ArcTGT, ArcS. However, we found that several euryarchaeal ArcSs have lysine transfer activity to q0N-tRNA to form q0kN-tRNA, which has a preQ0 lysine adduct as a base. Through comparative genomics and biochemical experiments, we found that ArcS forms a robust complex with a radical S-adenosylmethionine (SAM) enzyme named RaSEA. The ArcS–RaSEA complex anaerobically converted q0N-tRNA to G⁺-tRNA in the presence of SAM and lysine via q0kN-tRNA. We propose that ArcS and RaSEA should be considered an archaeosine synthase α-subunit (lysine transferase) and β-subunit (q0kN-tRNA lyase), respectively.
... tRNA-guanine-transglycosylases (TGT in bacteria, arcTGT in archaea) are the signature enzymes in the Q and G + tRNA modification pathways, as they exchange the targeted guanines with 7-deazaguanine precursors. In archaea, preQ 0 is directly incorporated into tRNA by arcTGT before being further modified by different types of amidotransferases (ArcS, Gat-QueC, or QueF-L) [15][16][17] . In bacteria, preQ 0 is reduced to 7aminomethyl-7-deazaguanine (preQ 1 ) by QueF 18 before TGT incorporates it in tRNA 19 , where it is further modified to Q in two steps [20][21][22] (Fig. 1). ...
... Indeed, Vibrio phage nt-1 encodes an ArcS homolog, and its DNA contains mainly dPreQ 0 but also dG + and dADG ( Table 2 and Fig. 3). ArcS was the first G + synthase identified in archaea 15 . Based on the phage and archaeal ArcS cluster in the SNNs ( Supplementary Fig. 2), it is possible that some phage ArcS protein evolved to perform not only an amidotransferase reaction, such as the archaeal ArcS 15 , but also an amidohydrolase reaction, such as the bacterial DpdC 27 . ...
... However, Halovirus HVTV-1 contains mainly dPreQ 1 but also a small amount of dADG and dG + . It is possible that the QueF-L transitions between its function as an amidohydrolase to an amidotransferase, but one cannot rule out that the host ArcS could catalyze the reaction, although the PUA domain specific for tRNA binding makes it highly unlikely 15 . Fig. 6 Proposed synthesis pathway for the 2′-deoxy-7-deazaguanine modifications identified in this study. ...
Genome modifications are central components of the continuous arms race between viruses and their hosts. The archaeosine base (G+), which was thought to be found only in archaeal tRNAs, was recently detected in genomic DNA of Enterobacteria phage 9g and was proposed to protect phage DNA from a wide variety of restriction enzymes. In this study, we identify three additional 2′-deoxy-7-deazaguanine modifications, which are all intermediates of the same pathway, in viruses: 2′-deoxy-7-amido-7-deazaguanine (dADG), 2′-deoxy-7-cyano-7-deazaguanine (dPreQ0) and 2′-deoxy-7- aminomethyl-7-deazaguanine (dPreQ1). We identify 180 phages or archaeal viruses that encode at least one of the enzymes of this pathway with an overrepresentation (60%) of viruses potentially infecting pathogenic microbial hosts. Genetic studies with the Escherichia phage CAjan show that DpdA is essential to insert the 7-deazaguanine base in phage genomic DNA and that 2′-deoxy-7-deazaguanine modifications protect phage DNA from host restriction enzymes. Viral genomic DNA is often modified to evade the host bacterial restriction system. Here the authors identified 2′-deoxy-7-deazaguanine modifications on phage DNA by comparative genomics and experimental validation, showing their role in genome protection.
... This idea is consistent with the fact that a mesophilic archaeon, Haloferax volcanii, does not contain wyosine derivatives in tRNA (58,84). (85) is formed by ArcTGT (86) and ArcS (87), and ArcTGT from T. kodakarensis modifies only G15 in tRNA (20). During the preparation of this paper, it was reported that an ArcTGT gene disruptant mutant of T. kodakarensis cannot grow at 93°C (28). ...
Thermococcus kodakarensis is a hyperthermophilic archaeon that can grow at 60 to 100°C. The sequence of tRNA Trp from this archaeon was determined by liquid chromatography/mass spectrometry. Fifteen types of modified nucleoside were observed at 21 positions, including 5 modifications at novel positions; in addition, methylwyosine at position 37 was newly observed in an archaeal tRNA Trp . The construction of trm11 (Δ trm11 ) and other gene disruptant strains confirmed the enzymes responsible for modifications in this tRNA. The lack of 2-methylguanosine (m ² G) at position 67 in the trm11 trm14 double disruptant strain suggested that this position is methylated by Trm14, which was previously identified as an m ² G6 methyltransferase. The Δ trm11 strain grew poorly at 95°C, indicating that archaeal Trm11 is required for T. kodakarensis survival at high temperatures.
... Archaeosine (G ϩ ) is widely found at position 15 of archaeal tRNAs. The pathway for this modification is complex, with multiple steps(11,50), and the whole pathway can be identified in M. jannaschii: the four enzymes for synthesis of the preQ 0 precursor (MptA/MJ0775, QueD/MJ1272, QueE/MJ1645, and QueC/MJ1347); TGT (MJ0436), which inserts preQ 0 in tRNA (51); and ArcS (MJ1022), which converts preQ 0 -tRNA to G ϩ(52). Archaeosine could be identified at this position in a large number of M. jannaschii tRNAs. ...
The tRNA m1R9 methyltransferase (Trm10) family is conserved throughout Eukarya and Archaea. Despite the presence of a single Trm10 gene in Archaea and most single-celled eukaryotes, metazoans encode up to three homologs of Trm10. Several disease states correlate with a deficiency in the human homolog TRMT10A, despite the presence of another cytoplasmic enzyme, TRMT10B. Here we investigate these phenomena and demonstrate that human TRMT10A (hTRMT10A) and human TRMT10B (hTRMT10B) are not biochemically redundant. In vitro activity assays with purified hTRMT10A and hTRMT10B reveal a robust activity for hTRMT10B as a tRNAAsp-specific m1A9 methyltransferase and suggest that it is the relevant enzyme responsible for this newly discovered m1A9 modification in humans. Moreover, a comparison of the two cytosolic enzymes with multiple tRNA substrates exposes the enzymes' distinct substrate specificities, and suggests that hTRMT10B exhibits a restricted selectivity hitherto unseen in the Trm10 enzyme family. Single-turnover kinetics and tRNA binding assays highlight further differences between the two enzymes and eliminate overall tRNA affinity as a primary determinant of substrate specificity for either enzyme. These results increase our understanding of the important biology of human tRNA modification systems, which can aid in understanding the molecular basis for diseases in which their aberrant function is increasingly implicated.
... Archaeosine (G ϩ ) is widely found at position 15 of archaeal tRNAs. The pathway for this modification is complex, with multiple steps(11,50), and the whole pathway can be identified in M. jannaschii: the four enzymes for synthesis of the preQ 0 precursor (MptA/MJ0775, QueD/MJ1272, QueE/MJ1645, and QueC/MJ1347); TGT (MJ0436), which inserts preQ 0 in tRNA (51); and ArcS (MJ1022), which converts preQ 0 -tRNA to G ϩ(52). Archaeosine could be identified at this position in a large number of M. jannaschii tRNAs. ...
While many posttranscriptional modifications in M. jannaschii tRNAs are also found in bacteria and eukaryotes, several that are unique to archaea were identified. By RNA modification mapping, the modification profiles of M. jannaschii tRNA anticodon loops were characterized, allowing a comparative analysis with H. volcanii modification profiles as well as a general comparison with bacterial and eukaryotic decoding strategies. This general comparison reveals that M. jannaschii , like H. volcanii , follows codon-decoding strategies similar to those used by bacteria, although position 37 appears to be modified to a greater extent than seen in H. volcanii .
