The Enzyme Database

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EC 2.5.1.75     
Accepted name: tRNA dimethylallyltransferase
Reaction: prenyl diphosphate + adenosine37 in tRNA = diphosphate + N6-(3-methylbut-2-en-1-yl)-adenosine37 in tRNA
For diagram of N6-(Dimethylallyl)adenosine37 modified tRNA biosynthesis, click here
Glossary: N6-(3-methylbut-2-en-1-yl)-adenine37 in tRNA = N6-dimethylallyladenine37 in tRNA
Other name(s): tRNA prenyltransferase; MiaA; transfer ribonucleate isopentenyltransferase (incorrect); Δ2-isopentenyl pyrophosphate:tRNA-Δ2-isopentenyl transferase (incorrect); Δ2-isopentenyl pyrophosphate:transfer ribonucleic acid Δ2-isopentenyltransferase (incorrect); dimethylallyl-diphosphate: tRNA dimethylallyltransferase; dimethylallyl-diphosphate:adenine37 in tRNA dimethylallyltransferase
Systematic name: prenyl-diphosphate:adenine37 in tRNA prenyltransferase
Comments: Formerly known as tRNA isopentenyltransferase, but it is now known that prenyl diphosphate, rather than isopentenyl diphosphate, is the substrate.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc
References:
1.  Leung, H.C., Chen, Y. and Winkler, M.E. Regulation of substrate recognition by the MiaA tRNA prenyltransferase modification enzyme of Escherichia coli K-12. J. Biol. Chem. 272 (1997) 13073–13083. [DOI] [PMID: 9148919]
2.  Soderberg, T. and Poulter, C.D. Escherichia coli dimethylallyl diphosphate:tRNA dimethylallyltransferase: essential elements for recognition of tRNA substrates within the anticodon stem-loop. Biochemistry 39 (2000) 6546–6553. [DOI] [PMID: 10828971]
3.  Moore, J.A., Mathis, J.R. and Poulter, C.D. Escherichia coli dimethylallyl diphosphate:tRNA dimethylallyltransferase: pre-steady-state kinetic studies. Biochim. Biophys. Acta 1479 (2000) 166–174. [DOI] [PMID: 11004538]
[EC 2.5.1.75 created 1972 as EC 2.5.1.8, transferred 2009 to EC 2.5.1.75]
 
 
EC 2.8.4.3     
Accepted name: tRNA-2-methylthio-N6-dimethylallyladenosine synthase
Reaction: N6-(3-methylbut-2-en-1-yl)-adenine37 in tRNA + sulfur-(sulfur carrier) + 2 S-adenosyl-L-methionine + reduced electron acceptor = N6-(3-methylbut-2-en-1-yl)-2-(methylsulfanyl)adenine37 in tRNA + S-adenosyl-L-homocysteine + (sulfur carrier) + L-methionine + 5′-deoxyadenine + electron acceptor (overall reaction)
(1a) N6-(3-methylbut-2-en-1-yl)-adenine37 in tRNA + sulfur-(sulfur carrier) + S-adenosyl-L-methionine + reduced electron acceptor = N6-(3-methylbut-2-en-1-yl)-2-thioadenine37 in tRNA + (sulfur carrier) + L-methionine + 5′-deoxyadenine + electron acceptor
(1b) S-adenosyl-L-methionine + N6-(3-methylbut-2-en-1-yl)-2-thioadenine37 in tRNA = S-adenosyl-L-homocysteine + N6-(3-methylbut-2-en-1-yl)-2-(methylsulfanyl)adenine37 in tRNA
For diagram of N6-(dimethylallyl)adenosine37 modified tRNA biosynthesis, click here
Glossary: N6-(3-methylbut-2-en-1-yl)-adenine37 in tRNA = N6-dimethylallyladenine37 in tRNA
Other name(s): MiaB; 2-methylthio-N-6-isopentenyl adenosine synthase; tRNA-i6A37 methylthiotransferase; tRNA (N6-dimethylallyladenosine37):sulfur-(sulfur carrier),S-adenosyl-L-methionine C2-methylthiotransferase
Systematic name: tRNA N6-(3-methylbut-2-en-1-yl)-adenine37:sulfur-(sulfur carrier),S-adenosyl-L-methionine C2-(methylsulfanyl)transferase
Comments: This bacterial enzyme binds two [4Fe-4S] clusters as well as the transferred sulfur [3]. The enzyme is a member of the superfamily of S-adenosyl-L-methionine-dependent radical (radical AdoMet) enzymes. 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.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc
References:
1.  Pierrel, F., Bjork, G.R., Fontecave, M. and Atta, M. Enzymatic modification of tRNAs: MiaB is an iron-sulfur protein. J. Biol. Chem. 277 (2002) 13367–13370. [DOI] [PMID: 11882645]
2.  Pierrel, F., Hernandez, H.L., Johnson, M.K., Fontecave, M. and Atta, M. MiaB protein from Thermotoga maritima. Characterization of an extremely thermophilic tRNA-methylthiotransferase. J. Biol. Chem. 278 (2003) 29515–29524. [DOI] [PMID: 12766153]
3.  Pierrel, F., Douki, T., Fontecave, M. and Atta, M. MiaB protein is a bifunctional radical-S-adenosylmethionine enzyme involved in thiolation and methylation of tRNA. J. Biol. Chem. 279 (2004) 47555–47563. [DOI] [PMID: 15339930]
4.  Hernandez, H.L., Pierrel, F., Elleingand, E., Garcia-Serres, R., Huynh, B.H., Johnson, M.K., Fontecave, M. and Atta, M. MiaB, a bifunctional radical-S-adenosylmethionine enzyme involved in the thiolation and methylation of tRNA, contains two essential [4Fe-4S] clusters. Biochemistry 46 (2007) 5140–5147. [DOI] [PMID: 17407324]
5.  Landgraf, B.J., Arcinas, A.J., Lee, K.H. and Booker, S.J. Identification of an intermediate methyl carrier in the radical S-adenosylmethionine methylthiotransferases RimO and MiaB. J. Am. Chem. Soc. 135 (2013) 15404–15416. [DOI] [PMID: 23991893]
[EC 2.8.4.3 created 2014, modified 2015]
 
 


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