Information on EC 2.4.2.48 - tRNA-guanine15 transglycosylase

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The expected taxonomic range for this enzyme is: Euryarchaeota

EC NUMBER
COMMENTARY
2.4.2.48
-
RECOMMENDED NAME
GeneOntology No.
tRNA-guanine15 transglycosylase
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REACTION
REACTION DIAGRAM
COMMENTARY
ORGANISM
UNIPROT ACCESSION NO.
LITERATURE
guanine15 in tRNA + 7-cyano-7-carbaguanine = 7-cyano-7-carbaguanine15 in tRNA + guanine
show the reaction diagram
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-
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PATHWAY
KEGG Link
MetaCyc Link
archaeosine biosynthesis
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SYSTEMATIC NAME
IUBMB Comments
tRNA-guanine15:7-cyano-7-carbaguanine tRNA-D-ribosyltransferase
Archaeal tRNAs contain the modified nucleoside archaeosine at position 15. This archaeal enzyme catalyses the exchange of guanine at position 15 of tRNA with the base preQ0, which is ultimately modified to form the nucleoside archaeosine (cf. EC 2.6.1.97) [1].
SYNONYMS
ORGANISM
UNIPROT ACCESSION NO.
COMMENTARY
LITERATURE
archaeosine tRNA-guanine transglycosylase
O58843
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ArcTGT
O58843
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transfer ribonucleic acid guanine15 transglycosylase
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-
-
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tRNA guanine15 transglycosidase
-
-
-
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tRNA-guanine transglycosylase
Q9C4M3
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tRNA-guanine transglycosylase
Haloferax volcanii ATCC 29605
Q9C4M3
-
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tRNA-guanine transglycosylase
Q57878
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ORGANISM
COMMENTARY
LITERATURE
SEQUENCE CODE
SEQUENCE DB
SOURCE
Haloferax volcanii ATCC 29605
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SwissProt
Manually annotated by BRENDA team
gene tgtA, orf MJ0436; gene tgt
UniProt
Manually annotated by BRENDA team
GENERAL INFORMATION
ORGANISM
UNIPROT ACCESSION NO.
COMMENTARY
LITERATURE
evolution
Q57878
biogenetic relationship of queuosine and archaeosine, overview. The elements necessary for tRNA recognition by the enzyme are not unique to archaeal tRNA
metabolism
Q57878
GTP is apparently the primary precursor in the biosynthesis of queuosine, which in a series of steps is converted to 7-(cyano)-7-deazaguanine, i.e. preQ0. PreQ0 is then reduced to PreQ1, and preQ1 is subsequently inserted into the tRNA by the enzyme TGT in a transglycosylation reaction in which the genetically encoded base guanine is eliminated
additional information
Q57878
the nature of the temperature dependence is consistent with a requirement for some degree of tRNA tertiary structure in order for recognition by the enzyme to occur
SUBSTRATE
PRODUCT                      
REACTION DIAGRAM
ORGANISM
UNIPROT ACCESSION NO.
COMMENTARY
(Substrate)
LITERATURE
(Substrate)
COMMENTARY
(Product)
LITERATURE
(Product)
Reversibility
r=reversible
ir=irreversible
?=not specified
guanine15 in tRNA + 7-cyano-7-carbaguanine
7-cyano-7-carbaguanine15 in tRNA + guanine
show the reaction diagram
Q57878
i.e. 7-(cyano)-7-deazaguanine = preQ0, i.e. 7-(cyano)-7-deazaguanine = preQ0. Haloferax volcanii tRNASer is used as substrate
-
-
?
guanine15 in tRNA + 7-cyano-7-carbaguanine
7-cyano-7-carbaguanine15 in tRNA + guanine
show the reaction diagram
Q9C4M3
key enzyme for the biosynthetic pathway leading to archaeosine in archaeal tRNAs, archaeosine base and 7-aminomethyl-7-deazaguanine are not incorporated into tRNA by this enzyme. Does not require ATP for the base replacement reaction
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-
?
tRNAguanine + 7-cyano-7-deazaguanine
?
show the reaction diagram
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archaeal TGT substitutes 7-cyano-7-deazaguanine for the G in position 15 of tRNA as the first step in archaeosine formation
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-
?
guanine15 in tRNA + 7-cyano-7-carbaguanine
7-cyano-7-carbaguanine15 in tRNA + guanine
show the reaction diagram
Haloferax volcanii ATCC 29605
Q9C4M3
key enzyme for the biosynthetic pathway leading to archaeosine in archaeal tRNAs, archaeosine base and 7-aminomethyl-7-deazaguanine are not incorporated into tRNA by this enzyme. Does not require ATP for the base replacement reaction
-
-
?
additional information
?
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Q57878
the enzyme catalyzes a transglycosylation reaction in which guanine is eliminated from position 15 of the tRNA and an archaeosine precursor (preQ0) is inserted. The enzyme is able to utilize both guanine and the 7-deazaguanine base preQ0 as substrates, but not other 7-deazaguanine bases, and is able to modify tRNA from all three phylogenetic domains. The enzyme shows good activity with the tRNASer transcript as well as tRNA from Escherichia coli and yeast
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NATURAL SUBSTRATES
NATURAL PRODUCTS
REACTION DIAGRAM
ORGANISM
UNIPROT ACCESSION NO.
COMMENTARY
(Substrate)
LITERATURE
(Substrate)
COMMENTARY
(Product)
LITERATURE
(Product)
REVERSIBILITY
r=reversible
ir=irreversible
?=not specified
guanine15 in tRNA + 7-cyano-7-carbaguanine
7-cyano-7-carbaguanine15 in tRNA + guanine
show the reaction diagram
Q57878
i.e. 7-(cyano)-7-deazaguanine = preQ0
-
-
?
guanine15 in tRNA + 7-cyano-7-carbaguanine
7-cyano-7-carbaguanine15 in tRNA + guanine
show the reaction diagram
Haloferax volcanii, Haloferax volcanii ATCC 29605
Q9C4M3
key enzyme for the biosynthetic pathway leading to archaeosine in archaeal tRNAs
-
-
?
METALS and IONS
ORGANISM
UNIPROT ACCESSION NO.
COMMENTARY
LITERATURE
Zn2+
-
contains a zinc-binding site
Mg2+
Q9C4M3
Mg2+ may be responsible for conformational rigidity of the tRNA, but not for the enzymatic activity itself. Mg2+ ion is required for activity with the T7 transcript as a substrate. Activity with unfractionated Escherichia coli tRNA does not require Mg2+
additional information
Q9C4M3
high salt concentration approximately 2.4 M is necessary for maximum activity
KM VALUE [mM]
KM VALUE [mM] Maximum
SUBSTRATE
ORGANISM
UNIPROT ACCESSION NO.
COMMENTARY
LITERATURE
IMAGE
additional information
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additional information
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SPECIFIC ACTIVITY [µmol/min/mg]
SPECIFIC ACTIVITY MAXIMUM
ORGANISM
UNIPROT ACCESSION NO.
COMMENTARY
LITERATURE
134
-
Q57878
purified recombinant TGT, pH 5.5, 80°C
pH OPTIMUM
pH MAXIMUM
ORGANISM
UNIPROT ACCESSION NO.
COMMENTARY
LITERATURE
5.5
-
Q57878
assay at
7.5
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Q9C4M3
-
additional information
-
Q57878
optimal activity at acidic pH
TEMPERATURE OPTIMUM
TEMPERATURE OPTIMUM MAXIMUM
ORGANISM
UNIPROT ACCESSION NO.
COMMENTARY
LITERATURE
80
-
Q57878
assay at
additional information
-
Q57878
optimal activity at high temperatures
PDB
SCOP
CATH
ORGANISM
Pyrococcus horikoshii (strain ATCC 700860 / DSM 12428 / JCM 9974 / NBRC 100139 / OT-3)
Pyrococcus horikoshii (strain ATCC 700860 / DSM 12428 / JCM 9974 / NBRC 100139 / OT-3)
Pyrococcus horikoshii (strain ATCC 700860 / DSM 12428 / JCM 9974 / NBRC 100139 / OT-3)
Pyrococcus horikoshii (strain ATCC 700860 / DSM 12428 / JCM 9974 / NBRC 100139 / OT-3)
MOLECULAR WEIGHT
MOLECULAR WEIGHT MAXIMUM
ORGANISM
UNIPROT ACCESSION NO.
COMMENTARY
LITERATURE
SUBUNITS
ORGANISM
UNIPROT ACCESSION NO.
COMMENTARY
LITERATURE
?
Q9C4M3
x * 78000, SDS-PAGE
?
Haloferax volcanii ATCC 29605
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x * 78000, SDS-PAGE
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Crystallization/COMMENTARY
ORGANISM
UNIPROT ACCESSION NO.
LITERATURE
crystal structure of tRNAVal in complex with archaeosine tRNA-guanine transglycosylase at 3.3 A resolution. The enzyme binds a different tRNA conformation (lambda form), in which the canonical core is completely disrupted and the melted D arm is protruded. The PUA domain is found to be crucial for the precise location of the tRNA molecule on the enzyme
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crystal structures of the enzyme at 2.2 A resolution and its complexes with guanine and 7-cyano-7-deazaguanine, at 2.3 and 2.5 A resolutions, respectively
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Purification/COMMENTARY
ORGANISM
UNIPROT ACCESSION NO.
LITERATURE
recombinant TGT 16.8fold from Escherichia coli strain BL21(DE3)/pYB-I-120 by ammonium sulfate fractionation, anion and cation exchange chromatography, and heat treatment
Q57878
Cloned/COMMENTARY
ORGANISM
UNIPROT ACCESSION NO.
LITERATURE
gene tgt, overexpression in Escherichia coli strain BL21(DE3)/pYB-I-120, subcloning in Escherichia coli strain DH5alpha
Q57878
truncated forms of TGT expressed in Escherichia coli
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ENGINEERING
ORGANISM
UNIPROT ACCESSION NO.
COMMENTARY
LITERATURE
additional information
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the C-terminal extension of the enzyme is not required for the selection of G15 as the site of base exchange. Truncated forms of Pyrococcus furiosus TGT retain their specificity for guanine exchange at position 15. Deletion of the PUA domain causes a 4fold drop in the observed kcat and results in a 75fold increased Km for tRNAAsp compared with full-length TGT