EC 2.3.1.234     
Accepted name: N6-L-threonylcarbamoyladenine synthase
Reaction: L-threonylcarbamoyladenylate + adenine37 in tRNA = AMP + N6-L-threonylcarbamoyladenine37 in tRNA
Glossary: N6-L-threonylcarbamoyladenine37 = t6A37
Other name(s): t6A synthase; Kae1; ygjD (gene name); Qri7
Systematic name: L-threonylcarbamoyladenylate:adenine37 in tRNA N6-L-threonylcarbamoyltransferase
Comments: The enzyme is involved in the synthesis of N6-threonylcarbamoyladenosine37 in tRNAs, which is found in tRNAs with the anticodon NNU, i.e. tRNAIle, tRNAThr, tRNAAsn, tRNALys, tRNASer and tRNAArg [3].
References:
1.  Lauhon, C.T. Mechanism of N6-threonylcarbamoyladenonsine (t6A) biosynthesis: isolation and characterization of the intermediate threonylcarbamoyl-AMP. Biochemistry 51 (2012) 8950–8963. [PMID: 23072323]
2.  Deutsch, C., El Yacoubi, B., de Crecy-Lagard, V. and Iwata-Reuyl, D. Biosynthesis of threonylcarbamoyl adenosine (t6A), a universal tRNA nucleoside. J. Biol. Chem. 287 (2012) 13666–13673. [PMID: 22378793]
3.  Perrochia, L., Crozat, E., Hecker, A., Zhang, W., Bareille, J., Collinet, B., van Tilbeurgh, H., Forterre, P. and Basta, T. In vitro biosynthesis of a universal t6A tRNA modification in Archaea and Eukarya. Nucleic Acids Res. 41 (2013) 1953–1964. [PMID: 23258706]
4.  Wan, L.C.K., Mao, D.Y.L., Neculai, D., Strecker, J., Chiovitti, D., Kurinov, I., Poda, G., Thevakumaran, N., Yuan, F., Szilard, R.K., Lissina, E., Nislow, C., Caudy, A.A., Durocher, D. and Sicheri, F. Reconstitution and characterization of eukaryotic N6-threonylcarbamoylation of tRNA using a minimal enzyme system. Nucleic Acids Res. 41 (2013) 6332–6346. [PMID: 23620299]
[EC 2.3.1.234 created 2014 as EC 2.6.99.4, transferred 2014 to EC 2.3.1.234]
 
 
EC 2.6.99.4      
Transferred entry: N6-L-threonylcarbamoyladenine synthase. Now EC 2.3.1.234, N6-L-threonylcarbamoyladenine synthase.
[EC 2.6.99.4 created 2014, deleted 2014]
 
 
EC 2.8.4.5     
Accepted name: tRNA (N6-L-threonylcarbamoyladenosine37-C2)-methylthiotransferase
Reaction: N6-L-threonylcarbamoyladenine37 in tRNA + sulfur-(sulfur carrier) + 2 S-adenosyl-L-methionine + reduced electron acceptor = 2-(methylsulfanyl)-N6-L-threonylcarbamoyladenine37 in tRNA + S-adenosyl-L-homocysteine + (sulfur carrier) + L-methionine + 5′-deoxyadenosine + electron acceptor (overall reaction)
(1a) N6-L-threonylcarbamoyladenine37 in tRNA + sulfur-(sulfur carrier) + S-adenosyl-L-methionine + reduced electron acceptor = 2-sulfanyl-N6-L-threonylcarbamoyladenine37 in tRNA + (sulfur carrier) + L-methionine + 5′-deoxyadenosine + electron acceptor
(1b) S-adenosyl-L-methionine + 2-sulfanyl-N6-L-threonylcarbamoyladenine37 in tRNA = S-adenosyl-L-homocysteine + 2-(methylsulfanyl)-N6-L-threonylcarbamoyladenine37 in tRNA
Glossary: N6-L-threonylcarbamoyladenine37 = t6A37
2-sulfanyl-N6-L-threonylcarbamoyladenine37 = ms2t6A37
Other name(s): MtaB; methylthio-threonylcarbamoyl-adenosine transferase B; CDKAL1 (gene name); tRNA (N6-L-threonylcarbamoyladenosine37):sulfur-(sulfur carrier),S-adenosyl-L-methionine C2-methylthiotransferase
Systematic name: tRNA (N6-L-threonylcarbamoyladenosine37):sulfur-(sulfur carrier),S-adenosyl-L-methionine C2-(methylsulfanyl)transferase
Comments: The enzyme, which is a member of the S-adenosyl-L-methionine-dependent radical (radical AdoMet) enzymes superfamily, binds two [4Fe-4S] clusters as well as the transferred sulfur. The sulfur donor is believed to be one of the [4Fe-4S] clusters, which is sacrificed in the process, so that in vitro the reaction is a single turnover. The identity of the electron donor is not known.
References:
1.  Arragain, S., Handelman, S.K., Forouhar, F., Wei, F.Y., Tomizawa, K., Hunt, J.F., Douki, T., Fontecave, M., Mulliez, E. and Atta, M. Identification of eukaryotic and prokaryotic methylthiotransferase for biosynthesis of 2-methylthio-N6-threonylcarbamoyladenosine in tRNA. J. Biol. Chem. 285 (2010) 28425–28433. [PMID: 20584901]
[EC 2.8.4.5 created 2014, modified 2015]
 
 


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