ExplorEnz: EC 2.8.4.3

Your query returned 1 entry. Printable version

2.8.4.3

Accepted name:

tRNA-2-methylthio-N⁶-dimethylallyladenosine synthase

Reaction:

N⁶-(3-methylbut-2-en-1-yl)-adenine³⁷ in tRNA + a [3Fe-4S] iron-sulfur cluster + 2 S-adenosyl-L-methionine + reduced electron acceptor = N⁶-(3-methylbut-2-en-1-yl)-2-(methylsulfanyl)adenine³⁷ in tRNA + S-adenosyl-L-homocysteine + a [3Fe-3S] iron-sulfur cluster + L-methionine + 5′-deoxyadenine + electron acceptor

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

Systematic name:

tRNA N⁶-(3-methylbut-2-en-1-yl)-adenine³⁷:[3Fe-4S] iron-sulfur cluster,S-adenosyl-L-methionine C²-(methylsulfanyl)transferase

Comments:

The enzyme is a member of the AdoMet radical (radical SAM) family. It contains one [4Fe-4S] cluster (the main cluster) and one [3Fe-4S] cluster (the auxiliary cluster). The reaction is thought to take place in two steps. In the first step, one molecule of SAM is used to methylate a bridging μ-sulfido ion of the auxiliary cluster, forming a thio-methyl group. In the second step, a second SAM molecule is cleaved to a 5′-deoxyadenosyl 5′-radical, which abstracts the C₂ hydrogen of the substrate, and the thio-methyl group is transferred from the auxiliary cluster to the radical-activated carbon in the tRNA substrate. The auxiliary cluster is left in an inactive [3Fe-3S] state and must be repaired or replaced before the enzyme could catalyse the next round.

Links to other databases:

BRENDA, EXPASY, Gene, 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.	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]
4.	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]
5.	Zhang, B., Arcinas, A.J., Radle, M.I., Silakov, A., Booker, S.J. and Krebs, C. First step in catalysis of the radical S-adenosylmethionine methylthiotransferase MiaB yields an intermediate with a [3Fe-4S]⁰-like auxiliary cluster. J. Am. Chem. Soc. 142 (2020) 1911–1924. [DOI] [PMID: 31899624]
6.	Esakova, O.A., Grove, T.L., Yennawar, N.H., Arcinas, A.J., Wang, B., Krebs, C., Almo, S.C. and Booker, S.J. Structural basis for tRNA methylthiolation by the radical SAM enzyme MiaB. Nature 597 (2021) 566–570. [DOI] [PMID: 34526715]

[EC 2.8.4.3 created 2014, modified 2015, modified 2026]