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MetaCyc Reaction:

Superclasses: Reactions Classified By Conversion TypeSimple ReactionsChemical Reactions
Reactions Classified By SubstrateMacromolecule ReactionsPolynucleotide-ReactionsRNA-ReactionstRNA-Reactions

EC Number:

Enzymes and Genes:

Saccharomyces cerevisiae: tRNAHis guanylyltransferaseInferred from experiment: THG1

The direction shown, i.e. which substrates are on the left and right sides, is in accordance with the Enzyme Commission system.

Mass balance status: Balance undetermined; a substrate lacks a chemical formula

Enzyme Commission Primary Name: tRNAHis guanylyltransferase

Enzyme Commission Synonyms: histidine tRNA guanylyltransferase, Thg1p (ambiguous), Thg1 (ambiguous)

Taxonomic Range: Viridiplantae, Metazoa, Fungi

Enzyme Commission Summary:
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, histidyl-tRNA ligase. The enzyme requires a divalent cation for activity [Pande91]. ATP activation is not required when the substrate contains a 5-triphosphate (ppp-tRNAHis) [Gu03].

The enzyme catalyzes two successive reactions.

The overall reaction is:

p-tRNAHis + ATP + GTP = pppGp-tRNAHis + AMP + diphosphate.

Citations: [Jahn91, Placido10, Jackman08, Hyde10]

Gene-Reaction Schematic

Gene-Reaction Schematic

Relationship Links: BRENDA:EC:, ENZYME:EC:, IUBMB-ExplorEnz:EC:

Created 30-Jun-2011 by Kothari A, SRI International


Gu03: Gu W, Jackman JE, Lohan AJ, Gray MW, Phizicky EM (2003). "tRNAHis maturation: an essential yeast protein catalyzes addition of a guanine nucleotide to the 5' end of tRNAHis." Genes Dev 17(23);2889-901. PMID: 14633974

Hyde10: Hyde SJ, Eckenroth BE, Smith BA, Eberley WA, Heintz NH, Jackman JE, Doublie S (2010). "tRNA(His) guanylyltransferase (THG1), a unique 3'-5' nucleotidyl transferase, shares unexpected structural homology with canonical 5'-3' DNA polymerases." Proc Natl Acad Sci U S A 107(47);20305-10. PMID: 21059936

Jackman08: Jackman JE, Phizicky EM (2008). "Identification of critical residues for G-1 addition and substrate recognition by tRNA(His) guanylyltransferase." Biochemistry 47(16);4817-25. PMID: 18366186

Jahn91: Jahn D, Pande S (1991). "Histidine tRNA guanylyltransferase from Saccharomyces cerevisiae. II. Catalytic mechanism." J Biol Chem 266(34);22832-6. PMID: 1660462

Pande91: Pande S, Jahn D, Soll D (1991). "Histidine tRNA guanylyltransferase from Saccharomyces cerevisiae. I. Purification and physical properties." J Biol Chem 266(34);22826-31. PMID: 1660461

Placido10: Placido A, Sieber F, Gobert A, Gallerani R, Giege P, Marechal-Drouard L (2010). "Plant mitochondria use two pathways for the biogenesis of tRNAHis." Nucleic Acids Res 38(21);7711-7. PMID: 20660484

Report Errors or Provide Feedback
Please cite the following article in publications resulting from the use of MetaCyc: Caspi et al, Nucleic Acids Research 42:D459-D471 2014
Page generated by Pathway Tools version 19.5 (software by SRI International) on Sun May 1, 2016, biocyc14.