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Information on EC 2.7.7.79 - tRNAHis guanylyltransferase and Organism(s) Homo sapiens and UniProt Accession Q9NWX6
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2.7.7.79 tRNAHis guanylyltransferaseIUBMB Comments
In eukarya an additional guanosine residue is added post-transcriptionally to the 5'-end of tRNAHis molecules. The addition occurs opposite a universally conserved adenosine73 and is thus the result of a non-templated 3'-5' addition reaction. The additional guanosine residue is an important determinant for aminoacylation by EC 6.1.1.21, histidine---tRNA ligase.The enzyme requires a divalent cation for activity . ATP activation is not required when the substrate contains a 5'-triphosphate (ppp-tRNAHis) .
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Word Map
- 2.7.7.79
- guanosine
- polymerases
- polymerization
-
histidyl-trna
- aminoacylation
-
fidelity
-
anticodon
-
post-transcriptionally
-
watson-crick
-
template-dependent
-
nucleotidyl
-
genome-encoded
- methanosarcina
- ntp
- acetivorans
-
phosphodiester
- thuringiensis
- medicine
The taxonomic range for the selected organisms is: Homo sapiens
The enzyme appears in selected viruses and cellular organisms
The enzyme appears in selected viruses and cellular organisms
Reaction Schemes
hide(Overall reactions are displayed. Show all >>)
p-tRNAHis
+
+
+
=
pGp-tRNAHis
+
+
2
p-tRNAHis
+
=
App-tRNAHis
+
App-tRNAHis
+
=
pppGp-tRNAHis
+
Synonyms
trna(his) guanylyltransferase, thg1l, trnahis guanylyltransferase, hsthg1, thg1p, mathg1, hthg1, bttlp, pathg1, dditlp3, 
more
topSYNONYM 
ORGANISM
UNIPROT
COMMENTARY 
LITERATURE
SYSTEMATIC NAME
IUBMB Comments
p-tRNAHis:GTP guanylyltransferase (ATP-hydrolysing)
In eukarya an additional guanosine residue is added post-transcriptionally to the 5'-end of tRNAHis molecules. The addition occurs opposite a universally conserved adenosine73 and is thus the result of a non-templated 3'-5' addition reaction. The additional guanosine residue is an important determinant for aminoacylation by EC 6.1.1.21, histidine---tRNA ligase.The enzyme requires a divalent cation for activity [2]. ATP activation is not required when the substrate contains a 5'-triphosphate (ppp-tRNAHis) [3].
SUBSTRATE
PRODUCT
REACTION DIAGRAM
ORGANISM
UNIPROT
COMMENTARY
(Substrate)
(Substrate)
LITERATURE
(Substrate)
(Substrate)
COMMENTARY
(Product)
(Product)
LITERATURE
(Product)
(Product)
Reversibility
r=reversible
ir=irreversible
?=not specified
r=reversible
ir=irreversible
?=not specified
p-ctRNAHis + ATP + GTP + H2O
pGp-ctRNAHis + AMP + 2 diphosphate
cytoplasmic tRNAHis
-
-
?
p-mtRNAHis + ATP + GTP + H2O
pGp-mtRNAHis + AMP + 2 diphosphate
mitochondrial tRNAHis
-
-
?
p-tRNAHis + ATP + GTP + H2O
pGp-tRNAHis + AMP + 2 diphosphate
overall reaction
-
-
?
p-tRNAHis + ATP + GTP + H2O
pGp-tRNAHis + AMP + 2 diphosphate
-
overall reaction
-
-
?
additional information
?
-
human Thg1 (hThg1) catalyzes the G-1 addition reaction for both human ctRNAHis and mtRNAHis through recognition of the anticodon. While hThg1 catalyzes consecutive GTP additions to mtRNAHis in vitr (consecutive G-2 and G-3 addition to pppG-1-hmtRNAHis), it does not exhibit any activity toward mature pG-1-mtRNAHis. hThg1 can add a GMP directly to the 5'-terminus of mtRNAHis in a template-dependent manner, but not to ctRNAHis. Acceleration of the diphosphate removal activity before or after the G-1 addition reaction is a key feature of hThg1 for maintaining a normal 5'-terminus of mtRNAHis in human mitochondria. The GUG to GAA conversion completely abolishes the ability of hThg1 to catalyze the adenylylation of both tRNAs, anticodon variants of hmtRNAHisGAA and hctRNAHis GAA, respetively, suggesting that hThg1 recognizes both of them in a His anticodon-dependent manner. The mobility of mtRNAHis is significantly faster than that of hctRNAHis on a native-PAGE gel, further suggesting a structural difference between them that is consistent with secondary structure predictions
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-
-
additional information
?
-
-
human Thg1 (hThg1) catalyzes the G-1 addition reaction for both human ctRNAHis and mtRNAHis through recognition of the anticodon. While hThg1 catalyzes consecutive GTP additions to mtRNAHis in vitr (consecutive G-2 and G-3 addition to pppG-1-hmtRNAHis), it does not exhibit any activity toward mature pG-1-mtRNAHis. hThg1 can add a GMP directly to the 5'-terminus of mtRNAHis in a template-dependent manner, but not to ctRNAHis. Acceleration of the diphosphate removal activity before or after the G-1 addition reaction is a key feature of hThg1 for maintaining a normal 5'-terminus of mtRNAHis in human mitochondria. The GUG to GAA conversion completely abolishes the ability of hThg1 to catalyze the adenylylation of both tRNAs, anticodon variants of hmtRNAHisGAA and hctRNAHis GAA, respetively, suggesting that hThg1 recognizes both of them in a His anticodon-dependent manner. The mobility of mtRNAHis is significantly faster than that of hctRNAHis on a native-PAGE gel, further suggesting a structural difference between them that is consistent with secondary structure predictions
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-
-
additional information
?
-
the enzyme performs 3' to 5' or reverse polymerization
-
-
-
additional information
?
-
-
Thg1 activity assay with 5'-triphosphorylated tRNAHis
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-
-
NATURAL SUBSTRATE
NATURAL PRODUCT
REACTION DIAGRAM
ORGANISM
UNIPROT
COMMENTARY
(Substrate)
(Substrate)
LITERATURE
(Substrate)
(Substrate)
COMMENTARY
(Product)
(Product)
LITERATURE
(Product)
(Product)
REVERSIBILITY
r=reversible
ir=irreversible
?=not specified
r=reversible
ir=irreversible
?=not specified
p-ctRNAHis + ATP + GTP + H2O
pGp-ctRNAHis + AMP + 2 diphosphate
cytoplasmic tRNAHis
-
-
?
p-mtRNAHis + ATP + GTP + H2O
pGp-mtRNAHis + AMP + 2 diphosphate
mitochondrial tRNAHis
-
-
?
p-tRNAHis + ATP + GTP + H2O
pGp-tRNAHis + AMP + 2 diphosphate
overall reaction
-
-
?
p-tRNAHis + ATP + GTP + H2O
pGp-tRNAHis + AMP + 2 diphosphate
-
overall reaction
-
-
?
COFACTOR
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
IMAGE
METALS and IONS
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
Mg2+
Mg2+
the dGTP-bound crystal structure reveales two bound Mg2+ ions associated with the nucleoside triphosphate. The distance between the two metal ions is 4.3 A. The two hTHG1 aspartates (D29 and D76) coordinate the two divalent metal ions, whereas E77 points away from the metals
Mg2+
required for ATPase activity, the 5'-triphosphophate of the incoming GTP is coordinated with a Mg2+ ion
pH OPTIMUM
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
TEMPERATURE OPTIMUM
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
ORGANISM
COMMENTARY
LITERATURE
UNIPROT
SEQUENCE DB
SOURCE
LOCALIZATION
ORGANISM
UNIPROT
COMMENTARY
GeneOntology No.
LITERATURE
SOURCE
additional information
additional information
mammalian Thg1 is localized to both the cytoplasm and mitochondria
-
additional information
-
mammalian Thg1 is localized to both the cytoplasm and mitochondria
-
GENERAL INFORMATION
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
evolution
the tRNAHis guanylyltransferase (Thg1) superfamily includes enzymes that are found in all three domains of life that all share the common ability to catalyze the 3' to 5' synthesis of nucleic acids. This catalytic activity is the reverse of all other known DNA and RNA polymerases. Forward 5' to 3' and reverse 3' to 5' polymerization are mechanistically similar. In bacteria and many archaea, the G-1 residue is genomically encoded and transcribed in the precursor tRNA transcript, and subsequent cleavage of the 5' leader sequence by ribonuclease P (RNase P) yields a mature tRNAHis with its identity-establishing G-1 element (tRNAHisG-1). Different pathways to establish tRNAHis identity, overview. Thg1-like proteins function in tRNA repair, TLPs in bacteria and archaea, structural comparison of Thg1 and TLPs. TLPs exhibit broader RNA recognition properties than Thg1 homologues
physiological function
evolution
-
implications for the evolution of eukaryotic Thg1 from a family of ancestral promiscuous RNA repair enzymes to the highly selective enzymes needed for their essential function in tRNAHis maturation. The HisRS requirement for Gx031 is a conserved feature throughout all domains of life, but bacteria and eukaryotes have evolved different mechanisms of incorporating the additionalx031 nucleotide into tRNAHis. Most eukaryotes studied to date incorporate G-1 posttranscriptionally to the processed 5' end of tRNAHis. This posttranscriptional addition of G-1 is performed by the tRNAHis guanylyltransferase (Thg1). Eukaryotic Thg1 enzymes are strictly specific for tRNAHis, and this specificity is accomplished by recognition of the tRNAHis GUG anticodon
malfunction
-
His152Ala and Lys187Ala mutant variants maintain a similar overall interaction with the anticodon region, arguing against the sufficiency of this interaction for driving catalysis. Instead, conservative mutagenesis reveals a distinct direct function for these residues in recognition of a non-Watson-Crick Gx021:A73 bp. tRNAHis anticodon interaction analysis in comparison to the wild-type, overview. The mutant Thg1 variants perform non-WC nucleotidyl transfer on pre-activated tRNA substrate p*pptRNAHis
physiological function
-
enzyme tRNAHis guanylyltransferase (Thg1) adds a single guanine to the-1 position of tRNAHis as part of its maturation. This seemingly modest addition of one nucleotide to tRNAHis ensures translational fidelity by providing a critical identity element for the histidyl aminoacyl tRNA synthetase (HisRS). Like HisRS, Thg1 utilizes the GUG anticodon for selective tRNAHis recognition, and Thg1-tRNA complex structures have revealed conserved residues that interact with anticodon nucleotides
additional information
physiological function
mammalian mitochondrial tRNAHis (mtRNAHis) is matured by tRNAHis guanylyltransferase through posttranscriptional addition of guanosine at the -1 position (G-1), which serves as an identity element for mitochondrial histidyl-tRNA synthetase. In cytoplasmic tRNAHis (ctRNAHis) maturation, tRNAHis guanylyltransferase (Thg1) adds a GTP onto the 5'-terminal of ctRNAHis and then removes the 5'-diphosphate to yield the mature 5'-monophospholylated G-1-ctRNAHis (pG-1-ctRNAHis). Analysis of the differences between tRNAHis maturation in the cytoplasm and mitochondria of humans, overview
physiological function
tRNAHis guanylyltransferase (Thg1) post-transcriptionally adds G-1. HistidyltRNA synthetase (HisRS) recognizes the Thg1-incorporated G-1 for the accurate histidylation of tRNAHis in eukaryotes. Role of 3' to 5' reverse RNA polymerization in tRNA fidelity and repair. G-1 is a tRNAHis identity element
additional information
hThg1 can add a GMP directly to the 5'-terminus of mtRNAHis in a template-dependent manner, while the fungal enzyme from Candida albicans cannot. Acceleration of the diphosphate removal activity before or after the G-1 addition reaction is a key feature of hThg1 for maintaining a normal 5'-terminus of mtRNAHis in human mitochondria
additional information
-
hThg1 can add a GMP directly to the 5'-terminus of mtRNAHis in a template-dependent manner, while the fungal enzyme from Candida albicans cannot. Acceleration of the diphosphate removal activity before or after the G-1 addition reaction is a key feature of hThg1 for maintaining a normal 5'-terminus of mtRNAHis in human mitochondria
additional information
molecular basis for tRNA recognition, and catalytic mechanism, overview. Molecular basis for non-Watson-Crick G-1 addition: tRNA activation, nucleotidyl transfer, diphosphate removal, and maintenance of tRNAHis fidelity. The superposition of Thg1 with the aforementioned polymerases displays similar positioning of the three conserved carboxylate residues in the polymerase active site to the pol I family, HsThg1 carboxylates D29, D76, and E77 correspond to T7 DNA polymerases D475, D654, and E655. The Thg1 mechanism of reverse polymerization may share features with the forward polymerization of the pol I family. Structure-function analyses of Thg1 and TLP enzymes, overview
additional information
-
requirement for two critical tRNA-interacting residues, His152 and Lys187, in the context of human Thg1, reaction mechanism, overview. Eukaryotic Thg1 enzymes are strictly specific for tRNAHis, and this specificity is accomplished by recognition of the tRNAHis GUG anticodon. His152 and Lys187 play critical roles in activation of tRNAHis for non-WC addition. Once the 5'-end activation step is completed, the need for His152 and Lys187 is no longer as critical
UNIPROT
ENTRY NAME
ORGANISM
NO. OF AA
NO. OF TRANSM. HELICES
MOLECULAR WEIGHT[Da]
SOURCE
SEQUENCE
LOCALIZATION PREDICTION
The reliability class of the localization prediction ranges from 1 (very reliable) to 5 (not reliable).
The reliability class of the localization prediction ranges from 1 (very reliable) to 5 (not reliable). THG1_HUMAN
298
0
34831
Swiss-Prot
Mitochondrion (Reliability: 3)
PDB
SCOP
CATH
UNIPROT
ORGANISM
MOLECULAR WEIGHT
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
SUBUNIT
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
tetramer
4 * 32000, SDS-PAGE, a dimer-of-dimers is the active tetrameric form
additional information
eukaryotic Thg1 enzymes show monomeric Thg1 that is composed of a six-strand antiparallel beta-sheet flanked by three or four alpha-helices on each side, along with a protruding long arm composed of two antiparallel beta-strands
CRYSTALLIZATION (Commentary)
ORGANISM
UNIPROT
LITERATURE
2.3 A crystal structure of human THG1 shares structural homology with canonical 5'-3' DNA polymerases and adenylyl/guanylyl cyclases, two enzyme families known to use a two-metal-ion mechanism for catalysis
PROTEIN VARIANTS
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
V55A
homozygous mutation identified in three siblings who presented with cerebellar signs, developmental delay, dysarthria, and pyramidal signs and had cerebellar atrophy on brain MRI. A defect in the protein tRNAHis guanylyltransferase activity is excluded in vitro
additional information
-
the emergence of dual function residues such as His152 and Lys187 would enable a single alteration to affect both catalytic activity and tRNA specificity of the enzyme
PURIFICATION (Commentary)
ORGANISM
UNIPROT
LITERATURE
recombinant C-terminally His6-tagged enzyme from Escherichia coli strain BL21(DE3) by nickel affinity chromatography and dialysis
recombinant C-terminally His6-tagged wild-type and mutant enzymes from Escherichia coli strain BL21(DE3) by nickel affinity chromatography and dialysis
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CLONED (Commentary)
ORGANISM
UNIPROT
LITERATURE
gene thg1, recombinant expression of C-terminally His6-tagged enzyme in Escherichia coli strain BL21(DE3)
gene thg1, recombinant expression of C-terminally His6-tagged wild-type and mutant enzymes in Escherichia coli strain BL21(DE3)
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APPLICATION
ORGANISM
UNIPROT
COMMENTARY
LITERATURE
medicine
homozygosity for the V55A mutation in THG1L is the cause of an abnormal mitochondrial network in the patient fibroblasts, likely by interfering with THG1L activity towards MFN2
REF.
AUTHORS
TITLE
JOURNAL
VOL.
PAGES
YEAR
ORGANISM (UNIPROT)
PUBMED ID
SOURCE
Hyde, S.J.; Eckenroth, B.E.; Smith, B.A.; Eberley, W.A.; Heintz, N.H.; Jackman, J.E.; Doubli, S.
tRNA(His) guanylyltransferase (THG1), a unique 3'-5' nucleotidyl transferase, shares unexpected structural homology with canonical 5'-3' DNA polymerases
Proc. Natl. Acad. Sci. USA
107
20305-20310
2010
Homo sapiens (Q9NWX6), Homo sapiens
Edvardson, S.; Elbaz-Alon, Y.; Jalas, C.; Matlock, A.; Patel, K.; Labbe, K.; Shaag, A.; Jackman, J.E.; Elpeleg, O.
A mutation in the THG1L gene in a family with cerebellar ataxia and developmental delay
Neurogenetics
17
219-225
2016
Homo sapiens (Q9NWX6), Homo sapiens
Nakamura, A.; Wang, D.; Komatsu, Y.
Biochemical analysis of human tRNAHis guanylyltransferase in mitochondrial tRNAHis maturation
Biochem. Biophys. Res. Commun.
503
2015-2021
2018
Homo sapiens (Q9NWX6), Homo sapiens
Chen, A.; Jayasinghe, M.; Chung, C.; Rao, B.; Kenana, R.; Heinemann, I.; Jackman, J.
The role of 3' to 5' reverse RNA polymerization in tRNA fidelity and repair
Genes (Basel)
10
250
2019
Bacillus thuringiensis (A0A2A8WD07), Bacillus thuringiensis T01-328 (A0A2A8WD07), Candida albicans (A0A1D8PQL3), Candida albicans ATCC MYA-2876 (A0A1D8PQL3), Dictyostelium discoideum (Q54E29), Dictyostelium discoideum (Q54HW0), Dictyostelium discoideum (Q54WD4), Dictyostelium discoideum (Q86IE7), Homo sapiens (Q9NWX6), Ignicoccus hospitalis (A8A9R6), Ignicoccus hospitalis DSM 18386 (A8A9R6), Ignicoccus hospitalis JCM 14125 (A8A9R6), Ignicoccus hospitalis KIN4/I (A8A9R6), Methanopyrus kandleri (Q8TZ46), Methanopyrus kandleri DSM 6324 (Q8TZ46), Methanopyrus kandleri JCM 9639 (Q8TZ46), Methanopyrus kandleri NBRC 100938 (Q8TZ46), Methanosarcina acetivorans (A0A1C7D1G9), Methanosarcina barkeri (Q46BQ4), Methanosarcina barkeri DSM 804 (Q46BQ4), Methanosarcina barkeri Fusaro (Q46BQ4), Methanothermobacter thermautotrophicus, Myxococcus xanthus (Q1CZS0), Myxococcus xanthus DK 1622 (Q1CZS0), no activity in Acanthamoeba castellanii, no activity in Trypanosoma brucei, Pyrobaculum aerophilum (Q8ZY97), Pyrobaculum aerophilum ATCC 51768 (Q8ZY97), Saccharomyces cerevisiae (P53215), Saccharomyces cerevisiae ATCC 204508 (P53215)
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