|
|
call loadScript javascripts\jsmol\core\package.js call loadScript javascripts\jsmol\core\core.z.js -- required by ClazzNode call loadScript javascripts\jsmol\J\awtjs2d\WebOutputChannel.js Jmol JavaScript applet jmolApplet0_object__071024302049352__ initializing getValue debug = null getValue logLevel = null getValue allowjavascript = null AppletRegistry.checkIn(jmolApplet0_object__071024302049352__) call loadScript javascripts\jsmol\core\corestate.z.js viewerOptions: { "name":"jmolApplet0_object","applet":true,"documentBase":"https://www.ebi.ac.uk/chebi/searchId.do?chebiId=CHEBI:45075","platform":"J.awtjs2d.Platform","fullName":"jmolApplet0_object__071024302049352__","display":"jmolApplet0_canvas2d","signedApplet":"true","appletReadyCallback":"Jmol._readyCallback","statusListener":"[J.appletjs.Jmol.MyStatusListener object]","codeBase":"https://www.ebi.ac.uk/chebi/javascripts/jsmol/","syncId":"071024302049352","bgcolor":"#000" } (C) 2012 Jmol Development Jmol Version: 13.2.7 $Date: 2013-10-01 11:35:15 -0500 (Tue, 01 Oct 2013) $ java.vendor: j2s java.version: 0.0 os.name: j2s Access: ALL memory: 0.0/0.0 processors available: 1 useCommandThread: false appletId:jmolApplet0_object (signed) starting HoverWatcher_1 getValue emulate = null defaults = "Jmol" getValue boxbgcolor = null getValue bgcolor = #000 backgroundColor = "#000" getValue ANIMFRAMECallback = null getValue APPLETREADYCallback = Jmol._readyCallback APPLETREADYCallback = "Jmol._readyCallback" getValue ATOMMOVEDCallback = null getValue CLICKCallback = null getValue ECHOCallback = null getValue ERRORCallback = null getValue EVALCallback = null getValue HOVERCallback = null getValue LOADSTRUCTCallback = null getValue MEASURECallback = null getValue MESSAGECallback = null getValue MINIMIZATIONCallback = null getValue PICKCallback = null getValue RESIZECallback = null getValue SCRIPTCallback = null getValue SYNCCallback = null getValue STRUCTUREMODIFIEDCallback = null getValue doTranslate = null language=en_US getValue popupMenu = null getValue script = null Jmol applet jmolApplet0_object__071024302049352__ ready call loadScript javascripts\jsmol\core\corescript.z.js call loadScript javascripts\jsmol\J\script\FileLoadThread.js starting QueueThread0_2 script 1 started starting HoverWatcher_3 starting HoverWatcher_4 The Resolver thinks Mol Marvin 09130721053D starting HoverWatcher_5 Time for openFile( Marvin 09130721053D 18 19 0 0 0 0 999 V2000 -1.2520 -0.0030 1.6650 N 0 0 0 0 0 0 0 0 0 0 0 0 -0.0810 0.0010 2.3630 C 0 0 0 0 0 0 0 0 0 0 0 0 1.0870 0.0000 1.7640 N 0 0 0 0 0 0 0 0 0 0 0 0 1.1830 0.0000 0.4270 C 0 0 0 0 0 0 0 0 0 0 0 0 0.0130 0.0000 -0.3390 C 0 0 0 0 0 0 0 0 0 0 0 0 -1.2360 0.0000 0.3130 C 0 0 0 0 0 0 0 0 0 0 0 0 -2.2750 0.0000 -0.3250 O 0 0 0 0 0 0 0 0 0 0 0 0 0.4430 0.0000 -1.7460 C 0 0 0 0 0 0 0 0 0 0 0 0 -0.3990 0.0000 -2.9030 C 0 0 0 0 0 0 0 0 0 0 0 0 -1.0690 0.0000 -3.8210 N 0 0 0 0 0 0 0 0 0 0 0 0 1.8060 0.0000 -1.7270 C 0 0 0 0 0 0 0 0 0 0 0 0 2.2420 0.0000 -0.4370 N 0 0 0 0 0 0 0 0 0 0 0 0 -0.1250 0.0010 3.7340 N 0 0 0 0 0 0 0 0 0 0 0 0 -2.0980 -0.0030 2.1390 H 0 0 0 0 0 0 0 0 0 0 0 0 0.6980 0.0000 4.2460 H 0 0 0 0 0 0 0 0 0 0 0 0 -0.9810 0.0060 4.1920 H 0 0 0 0 0 0 0 0 0 0 0 0 3.1740 -0.0010 -0.1690 H 0 0 0 0 0 0 0 0 0 0 0 0 2.4420 0.0000 -2.6000 H 0 0 0 0 0 0 0 0 0 0 0 0 1 2 1 0 0 0 0 1 6 1 0 0 0 0 1 14 1 0 0 0 0 2 3 2 0 0 0 0 2 13 1 0 0 0 0 3 4 1 0 0 0 0 4 5 4 0 0 0 0 4 12 4 0 0 0 0 5 6 1 0 0 0 0 5 8 4 0 0 0 0 6 7 2 0 0 0 0 8 9 1 0 0 0 0 8 11 4 0 0 0 0 9 10 3 0 0 0 0 11 12 4 0 0 0 0 11 18 1 0 0 0 0 12 17 1 0 0 0 0 13 15 1 0 0 0 0 13 16 1 0 0 0 0 M END): 29 ms reading 18 atoms ModelSet: haveSymmetry:false haveUnitcells:false haveFractionalCoord:false 1 model in this collection. Use getProperty "modelInfo" or getProperty "auxiliaryInfo" to inspect them. Default Van der Waals type for model set to Babel 18 atoms created ModelSet: not autobonding; use forceAutobond=true to force automatic bond creation Script completed Jmol script terminated
|
| InChI=1S/C7H5N5O/c8-1-3-2-10-5-4(3)6(13)12-7(9)11-5/h2H,(H4,9,10,11,12,13) |
| FMKSMYDYKXQYRV-UHFFFAOYSA-N |
| Nc1nc2[nH]cc(C#N)c2c(=O)[nH]1 |
|
|
Escherichia coli
(NCBI:txid562)
|
See:
PubMed
|
|
Escherichia coli metabolite
Any bacterial metabolite produced during a metabolic reaction in Escherichia coli.
|
|
View more via ChEBI Ontology
|
2-amino-4-oxo-4,7-dihydro-3H-pyrrolo[2,3-d]pyrimidine-5-carbonitrile
|
|
2-AMINO-4-OXO-4,7-DIHYDRO-3H-PYRROLO[2,3-D]PYRIMIDINE-5-CARBONITRILE
|
PDBeChem
|
|
7-CN-7-deazaG
|
ChEBI
|
|
7-Cyano-7-carbaguanine
|
KEGG COMPOUND
|
|
7-cyano-7-deazaguanine
|
UniProt
|
|
7-Cyano-7-deazaguanine
|
KEGG COMPOUND
|
|
preQ(0)
|
ChEBI
|
|
5022878
|
Reaxys Registry Number
|
Reaxys
|
Thiaville JJ, Kellner SM, Yuan Y, Hutinet G, Thiaville PC, Jumpathong W, Mohapatra S, Brochier-Armanet C, Letarov AV, Hillebrand R, Malik CK, Rizzo CJ, Dedon PC, de Crécy-Lagard V (2016)
Novel genomic island modifies DNA with 7-deazaguanine derivatives.
Proceedings of the National Academy of Sciences of the United States of America 113, E1452-9 [PubMed:26929322]
[show Abstract]
The discovery of ∼20-kb gene clusters containing a family of paralogs of tRNA guanosine transglycosylase genes, called tgtA5, alongside 7-cyano-7-deazaguanine (preQ0) synthesis and DNA metabolism genes, led to the hypothesis that 7-deazaguanine derivatives are inserted in DNA. This was established by detecting 2'-deoxy-preQ0 and 2'-deoxy-7-amido-7-deazaguanosine in enzymatic hydrolysates of DNA extracted from the pathogenic, Gram-negative bacteria Salmonella enterica serovar Montevideo. These modifications were absent in the closely related S. enterica serovar Typhimurium LT2 and from a mutant of S Montevideo, each lacking the gene cluster. This led us to rename the genes of the S. Montevideo cluster as dpdA-K for 7-deazapurine in DNA. Similar gene clusters were analyzed in ∼150 phylogenetically diverse bacteria, and the modifications were detected in DNA from other organisms containing these clusters, including Kineococcus radiotolerans, Comamonas testosteroni, and Sphingopyxis alaskensis Comparative genomic analysis shows that, in Enterobacteriaceae, the cluster is a genomic island integrated at the leuX locus, and the phylogenetic analysis of the TgtA5 family is consistent with widespread horizontal gene transfer. Comparison of transformation efficiencies of modified or unmodified plasmids into isogenic S. Montevideo strains containing or lacking the cluster strongly suggests a restriction-modification role for the cluster in Enterobacteriaceae. Another preQ0 derivative, 2'-deoxy-7-formamidino-7-deazaguanosine, was found in the Escherichia coli bacteriophage 9 g, as predicted from the presence of homologs of genes involved in the synthesis of the archaeosine tRNA modification. These results illustrate a deep and unexpected evolutionary connection between DNA and tRNA metabolism. | Winkler M, Dokulil K, Weber H, Pavkov-Keller T, Wilding B (2015)
The Nitrile-Forming Enzyme 7-Cyano-7-Deazaguanine Synthase from Geobacillus kaustophilus: A Reverse Nitrilase?
Chembiochem : a European journal of chemical biology 16, 2373-2378 [PubMed:26391327]
[show Abstract]
7-Cyano-7-deazaguanine synthase (E.C. 6.3.4.20) is an enzyme that catalyzes the formation of a nitrile from a carboxylic acid and ammonia at the expense of ATP. The protein from G. kaustophilus was heterologously expressed, and its biochemical characteristics were explored by using a newly developed HPLC-MS based assay, (31) P NMR, and a fluorescence-based thermal-shift assay. The protein showed the expected high thermostability, had a pH optimum at pH 9.5, and an apparent temperature optimum at 60 °C. We observed strict substrate specificity of QueC for the natural substrate 7-carboxy-7-deazaguanine, and determined AMP and pyrophosphate as co-products of preQ0. | Nomura Y, Onda Y, Ohno S, Taniguchi H, Ando K, Oka N, Nishikawa K, Yokogawa T (2013)
Purification and comparison of native and recombinant tRNA-guanine transglycosylases from Methanosarcina acetivorans.
Protein expression and purification 88, 13-19 [PubMed:23201278]
[show Abstract]
Many archaeal tRNAs have archaeosine (G(+)) at position 15 in the D-loop and this is thought to strengthen the tertiary interaction with C48 in the V-loop. In the first step of G(+) biosynthesis, archaeosine tRNA-guanine transglycosylase (ArcTGT)(1) catalyzes the base exchange reaction from guanine to 7-cyano-7-deazaguanine (preQ(0)). ArcTGT is classified into full-size or split types, according to databases of genomic information. Although the full-size type forms a homodimeric structure, the split type has been assumed to form a heterotetrameric structure, consisting of two kinds of peptide. However, there has been no definitive evidence for this presented to date. Here, we show that native ArcTGT could be isolated from Methanosarcina acetivorans and two peptides formed a robust complex in cells. Consequently, the two peptides function as actual subunits of ArcTGT. We also overexpressed recombinant ArcTGT in Escherichia coli cells. Product was successfully obtained by co-overexpression of the two subunits but one subunit alone was not adequately expressed in soluble fractions. This result suggests that interaction between the two subunits may contribute to the conformational stability of split ArcTGT. The values of the kinetic parameters for the recombinant and native ArcTGT were closely similar. Moreover, tRNA transcript with preQ(0) at position 15 was successfully prepared using the recombinant ArcTGT. This tRNA transcript is expected to be useful as a substrate for studies seeking the enzymes responsible for G(+) biosynthesis. | Phillips G, Swairjo MA, Gaston KW, Bailly M, Limbach PA, Iwata-Reuyl D, de Crécy-Lagard V (2012)
Diversity of archaeosine synthesis in crenarchaeota.
ACS chemical biology 7, 300-305 [PubMed:22032275]
[show Abstract]
Archaeosine (G(+)) is found at position 15 of many archaeal tRNAs. In Euryarchaeota, the G(+) precursor, 7-cyano-7-deazaguanine (preQ(0)), is inserted into tRNA by tRNA-guanine transglycosylase (arcTGT) before conversion into G(+) by ARChaeosine Synthase (ArcS). However, many Crenarchaeota known to harbor G(+) lack ArcS homologues. Using comparative genomics approaches, two families that could functionally replace ArcS in these organisms were identified: (1) GAT-QueC, a two-domain family with an N-terminal glutamine amidotransferase class-II domain fused to a domain homologous to QueC, the enzyme that produces preQ(0) and (2) QueF-like, a family homologous to the bacterial enzyme catalyzing the reduction of preQ(0) to 7-aminomethyl-7-deazaguanine. Here we show that these two protein families are able to catalyze the formation of G(+) in a heterologous system. Structure and sequence comparisons of crenarchaeal and euryarchaeal arcTGTs suggest the crenarchaeal enzymes have broader substrate specificity. These results led to a new model for the synthesis and salvage of G(+) in Crenarchaeota. | Chikwana VM, Stec B, Lee BW, de Crécy-Lagard V, Iwata-Reuyl D, Swairjo MA (2012)
Structural basis of biological nitrile reduction.
The Journal of biological chemistry 287, 30560-30570 [PubMed:22787148]
[show Abstract]
The enzyme QueF catalyzes the reduction of the nitrile group of 7-cyano-7-deazaguanine (preQ(0)) to 7-aminomethyl-7-deazaguanine (preQ(1)), the only nitrile reduction reaction known in biology. We describe here two crystal structures of Bacillus subtilis QueF, one of the wild-type enzyme in complex with the substrate preQ(0), trapped as a covalent thioimide, a putative intermediate in the reaction, and the second of the C55A mutant in complex with the substrate preQ(0) bound noncovalently. The QueF enzyme forms an asymmetric tunnel-fold homodecamer of two head-to-head facing pentameric subunits, harboring 10 active sites at the intersubunit interfaces. In both structures, a preQ(0) molecule is bound at eight sites, and in the wild-type enzyme, it forms a thioimide covalent linkage to the catalytic residue Cys-55. Both structural and transient kinetic data show that preQ(0) binding, not thioimide formation, induces a large conformational change in and closure of the active site. Based on these data, we propose a mechanism for the activation of the Cys-55 nucleophile and subsequent hydride transfer. | Kim Y, Zhou M, Moy S, Morales J, Cunningham MA, Joachimiak A (2010)
High-resolution structure of the nitrile reductase QueF combined with molecular simulations provide insight into enzyme mechanism.
Journal of molecular biology 404, 127-137 [PubMed:20875425]
[show Abstract]
Here, we report the 1.53-Å crystal structure of the enzyme 7-cyano-7-deazaguanine reductase (QueF) from Vibrio cholerae, which is responsible for the complete reduction of a nitrile (CN) bond to a primary amine (H(2)C-NH(2)). At present, this is the only example of a biological pathway that includes reduction of a nitrile bond, establishing QueF as particularly noteworthy. The structure of the QueF monomer resembles two connected ferrodoxin-like domains that assemble into dimers. Ligands identified in the crystal structure suggest the likely binding conformation of the native substrates NADPH and 7-cyano-7-deazaguanine. We also report on a series of numerical simulations that have shed light on the mechanism by which this enzyme affects the transfer of four protons (and electrons) to the 7-cyano-7-deazaguanine substrate. In particular, the simulations suggest that the initial step of the catalytic process is the formation of a covalent adduct with the residue Cys194, in agreement with previous studies. The crystal structure also suggests that two conserved residues (His233 and Asp102) play an important role in the delivery of a fourth proton to the substrate. | Phillips G, Chikwana VM, Maxwell A, El-Yacoubi B, Swairjo MA, Iwata-Reuyl D, de Crécy-Lagard V (2010)
Discovery and characterization of an amidinotransferase involved in the modification of archaeal tRNA.
The Journal of biological chemistry 285, 12706-12713 [PubMed:20129918]
[show Abstract]
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 (preQ(0)), an advanced precursor that is produced in a tRNA-independent portion of the biosynthesis, followed by its insertion into the tRNA by the enzyme tRNA-guanine transglycosylase (arcTGT), which replaces the target guanine base yielding preQ(0)-tRNA. The enzymes responsible for the biosynthesis of preQ(0) were recently identified, but the enzyme(s) catalyzing the conversion of preQ(0)-tRNA to G(+)-tRNA have remained elusive. Using a comparative genomics approach, we identified a protein family implicated in the late stages of archaeosine biosynthesis. Notably, this family is a paralog of arcTGT and is generally annotated as TgtA2. Structure-based alignments comparing arcTGT and TgtA2 reveal that TgtA2 lacks key arcTGT catalytic residues and contains an additional module. We constructed a Haloferax volcanii DeltatgtA2 derivative and demonstrated that tRNA from this strain lacks G(+) and instead accumulates preQ(0). We also cloned the corresponding gene from Methanocaldococcus jannaschii (mj1022) and characterized the purified recombinant enzyme. Recombinant MjTgtA2 was shown to convert preQ(0)-tRNA to G(+)-tRNA using several nitrogen sources and to do so in an ATP-independent process. This is the only example of the conversion of a nitrile to a formamidine known in biology and represents a new class of amidinotransferase chemistry. | McCarty RM, Somogyi A, Lin G, Jacobsen NE, Bandarian V (2009)
The deazapurine biosynthetic pathway revealed: in vitro enzymatic synthesis of PreQ(0) from guanosine 5'-triphosphate in four steps.
Biochemistry 48, 3847-3852 [PubMed:19354300]
[show Abstract]
Deazapurine-containing secondary metabolites comprise a broad range of structurally diverse nucleoside analogues found throughout biology, including various antibiotics produced by species of Streptomyces bacteria and the hypermodified tRNA bases queuosine and archaeosine. Despite early interest in deazapurines as antibiotic, antiviral, and antineoplastic agents, the biosynthetic route toward deazapurine production has remained largely elusive for more than 40 years. Here we present the first in vitro preparation of the deazapurine base preQ(0), by the successive action of four enzymes. The pathway includes the conversion of the recently identified biosynthetic intermediate, 6-carboxy-5,6,7,8-tetrahydropterin, to a novel intermediate, 7-carboxy-7-deazaguanine (CDG), by an unusual transformation catalyzed by Bacillus subtilis QueE, a member of the radical SAM enzyme superfamily. The carboxylate moiety on CDG is converted subsequently to a nitrile to yield preQ(0) by either B. subtilis QueC or Streptomyces rimosus ToyM in an ATP-dependent reaction, in which ammonia serves as the nitrogen source. The results presented here are consistent with early radiotracer studies on deazapurine biosynthesis and provide a unified pathway for the production of deazapurines in nature. | Spitale RC, Torelli AT, Krucinska J, Bandarian V, Wedekind JE (2009)
The structural basis for recognition of the PreQ0 metabolite by an unusually small riboswitch aptamer domain.
The Journal of biological chemistry 284, 11012-11016 [PubMed:19261617]
[show Abstract]
Riboswitches are RNA elements that control gene expression through metabolite binding. The preQ(1) riboswitch exhibits the smallest known ligand-binding domain and is of interest for its economical organization and high affinity interactions with guanine-derived metabolites required to confer tRNA wobbling. Here we present the crystal structure of a preQ(1) aptamer domain in complex with its precursor metabolite preQ(0). The structure is highly compact with a core that features a stem capped by a well organized decaloop. The metabolite is recognized within a deep pocket via Watson-Crick pairing with C15. Additional hydrogen bonds are made to invariant bases U6 and A29. The ligand-bound state confers continuous helical stacking throughout the core fold, thus providing a platform to promote Watson-Crick base pairing between C9 of the decaloop and the first base of the ribosome-binding site, G33. The structure offers insight into the mode of ribosome-binding site sequestration by a minimal RNA fold stabilized by metabolite binding and has implications for understanding the molecular basis by which bacterial genes are regulated. | Phillips G, El Yacoubi B, Lyons B, Alvarez S, Iwata-Reuyl D, de Crécy-Lagard V (2008)
Biosynthesis of 7-deazaguanosine-modified tRNA nucleosides: a new role for GTP cyclohydrolase I.
Journal of bacteriology 190, 7876-7884 [PubMed:18931107]
[show Abstract]
Queuosine (Q) and archaeosine (G(+)) are hypermodified ribonucleosides found in tRNA. Q is present in the anticodon region of tRNA(GUN) in Eukarya and Bacteria, while G(+) is found at position 15 in the D-loop of archaeal tRNA. Prokaryotes produce these 7-deazaguanosine derivatives de novo from GTP through the 7-cyano-7-deazaguanine (pre-Q(0)) intermediate, but mammals import the free base, queuine, obtained from the diet or the intestinal flora. By combining the results of comparative genomic analysis with those of genetic studies, we show that the first enzyme of the folate pathway, GTP cyclohydrolase I (GCYH-I), encoded in Escherichia coli by folE, is also the first enzyme of pre-Q(0) biosynthesis in both prokaryotic kingdoms. Indeed, tRNA extracted from an E. coli DeltafolE strain is devoid of Q and the deficiency is complemented by expressing GCYH-I-encoding genes from different bacterial or archaeal origins. In a similar fashion, tRNA extracted from a Haloferax volcanii strain carrying a deletion of the GCYH-I-encoding gene contains only traces of G(+). These results link the production of a tRNA-modified base to primary metabolism and further clarify the biosynthetic pathway for these complex modified nucleosides. | Lee BW, Van Lanen SG, Iwata-Reuyl D (2007)
Mechanistic studies of Bacillus subtilis QueF, the nitrile oxidoreductase involved in queuosine biosynthesis.
Biochemistry 46, 12844-12854 [PubMed:17929836]
[show Abstract]
The enzyme QueF was recently identified as an enzyme involved in the biosynthesis of queuosine, a 7-deazaguanosine modified nucleoside found in bacterial and eukaryotic tRNA. QueF exhibits sequence homology to the type I GTP cyclohydrolases characterized by FolE, but contrary to the predictions based on sequence analysis the enzyme in fact catalyzes a mechanistically unrelated reaction, the NADPH-dependent reduction of 7-cyano-7-deazaguanine (preQ0) to 7-aminomethyl-7-deazaguanine (preQ1), a late step in the queuosine pathway. The reduction of a nitrile is unprecedented in biology, and we report here characterization and mechanistic studies of the enzyme from Bacillus subtilis. The recombinant enzyme exhibits optimal activity at pH 7.5 and moderate ionic strength, and is not dependent on metal ions for catalytic activity. Steady-state kinetic analysis provided a kcat = 0.66 +/- 0.04 min-1, KM (preQ0) = 0.237 +/- 0.045 microM, and KM (NADPH) = 19.2 +/- 1.1 microM. Based on sequence analysis and homology modeling we predicted previously that Cys55 would be present in the active site and in proximity to the nitrile group of preQ0. Consistent with that prediction we observed that the enzyme was inactivated when preincubated with iodoacetamide, and protected from inactivation when preQ0 was present. Furthermore, titrations of the enzyme with preQ0 in the absence of NADPH were accompanied by the appearance of a new absorption band at 376 nm in the UV-vis spectrum consistent with the formation of an alpha,beta-unsaturated thioimide. Site-directed mutagenesis of Cys55 to Ala or Ser resulted in loss of catalytic activity and no absorption at 376 nm upon addition of preQ0. Based on our data we propose a chemical mechanism for the enzyme-catalyzed reaction, and a chemical rationale for the observation of covalent catalysis. | Swairjo MA, Reddy RR, Lee B, Van Lanen SG, Brown S, de Crécy-Lagard V, Iwata-Reuyl D, Schimmel P (2005)
Crystallization and preliminary X-ray characterization of the nitrile reductase QueF: a queuosine-biosynthesis enzyme.
Acta crystallographica. Section F, Structural biology and crystallization communications 61, 945-948 [PubMed:16511203]
[show Abstract]
QueF (MW = 19.4 kDa) is a recently characterized nitrile oxidoreductase which catalyzes the NADPH-dependent reduction of 7-cyano-7-deazaguanine (preQ0) 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 A. 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 preQ0. This crystal form diffracted to 2.25 A resolution. | Watanabe M, Matsuo M, Tanaka S, Akimoto H, Asahi S, Nishimura S, Katze JR, Hashizume T, Crain PF, McCloskey JA, Okada N (1997)
Biosynthesis of archaeosine, a novel derivative of 7-deazaguanosine specific to archaeal tRNA, proceeds via a pathway involving base replacement on the tRNA polynucleotide chain.
The Journal of biological chemistry 272, 20146-20151 [PubMed:9242689]
[show Abstract]
Archaeosine is a novel derivative of 7-deazaguanosine found in transfer RNAs of most organisms exclusively in the archaeal phylogenetic lineage and is present in the D-loop at position 15. We show that this modification is formed by a posttranscriptional base replacement reaction, catalyzed by a new tRNA-guanine transglycosylase (TGT), which has been isolated from Haloferax volcanii and purified nearly to homogeneity. The molecular weight of the enzyme was estimated to be 78 kDa by SDS-gel electrophoresis. The enzyme can insert free 7-cyano-7-deazaguanine (preQ0 base) in vitro at position 15 of an H. volcanii tRNA T7 transcript, replacing the guanine originally located at that position without breakage of the phosphodiester backbone. Since archaeosine base and 7-aminomethyl-7-deazaguanine (preQ1 base) were not incorporated into tRNA by this enzyme, preQ0 base appears to be the actual substrate for the TGT of H. volcanii, a conclusion supported by characterization of preQ0 base in an acid-soluble extract of H. volcanii cells. Thus, this novel TGT in H. volcanii is a key enzyme for the biosynthetic pathway leading to archaeosine in archaeal tRNAs. |
|
