TRNA(His) guanylyltransferase explained

tRNA(His) guanylyltransferase
Ec Number:	2.7.7.79

tRNA(His) guanylyltransferase (histidine tRNA guanylyltransferase, Thg1p, Thg1) is an enzyme with systematic name p-tRNA(His):GTP guanylyltransferase (ATP-hydrolysing).^{[1] [2] [3] [4] [5] [6]} This enzyme catalyses the following chemical reaction

p-tRNA(His) + ATP + GTP

\rightleftharpoons pppGp-tRNA(His) + AMP + diphosphate (overall reaction)

(1a) p-tRNA(His) + ATP

\rightleftharpoons App-tRNA(His) + diphosphate

(1b) App-tRNA(His) + GTP

\rightleftharpoons pppGp-tRNA(His) + AMP

The enzyme requires a divalent cation for activity.

Notes and References

1. Jahn D, Pande S . Histidine tRNA guanylyltransferase from Saccharomyces cerevisiae. II. Catalytic mechanism . The Journal of Biological Chemistry . 266 . 34 . 22832–6 . December 1991 . 10.1016/S0021-9258(18)54429-X . 1660462 . free .
2. Pande S, Jahn D, Söll D . Histidine tRNA guanylyltransferase from Saccharomyces cerevisiae. I. Purification and physical properties . The Journal of Biological Chemistry . 266 . 34 . 22826–31 . December 1991 . 10.1016/S0021-9258(18)54428-8 . 1660461 . free .
3. Gu W, Jackman JE, Lohan AJ, Gray MW, Phizicky EM . tRNAHis maturation: an essential yeast protein catalyzes addition of a guanine nucleotide to the 5' end of tRNAHis . Genes & Development . 17 . 23 . 2889–901 . December 2003 . 14633974 . 289149 . 10.1101/gad.1148603 .
4. Placido A, Sieber F, Gobert A, Gallerani R, Giegé P, Maréchal-Drouard L . Plant mitochondria use two pathways for the biogenesis of tRNAHis . Nucleic Acids Research . 38 . 21 . 7711–7 . November 2010 . 20660484 . 2995067 . 10.1093/nar/gkq646 .
5. Jackman JE, Phizicky EM . Identification of critical residues for G-1 addition and substrate recognition by tRNA(His) guanylyltransferase . Biochemistry . 47 . 16 . 4817–25 . April 2008 . 18366186 . 10.1021/bi702517q .
6. Hyde SJ, Eckenroth BE, Smith BA, Eberley WA, Heintz NH, Jackman JE, Doublié S . tRNA(His) guanylyltransferase (THG1), a unique 3'-5' nucleotidyl transferase, shares unexpected structural homology with canonical 5'-3' DNA polymerases . Proceedings of the National Academy of Sciences of the United States of America . 107 . 47 . 20305–10 . November 2010 . 21059936 . 2996709 . 10.1073/pnas.1010436107 . free .