ExplorEnz: EC 2.8.4.3

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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, PDB

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]