Open AccessStructural characterization of B. subtilis m1A22 tRNA methyltransferase TrmK: insights into tRNA recognition
Author(s) -
Clément Dégut,
Martine Roovers,
Pierre Barraud,
Franck Brachet,
André Feller,
Valéry Larue,
Abdalla Al Refaii,
J. Caillet,
Louis Droogmans,
Carine Tisné
Publication year - 2019
Publication title -
nucleic acids research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 9.008
H-Index - 537
eISSN - 1362-4954
pISSN - 0305-1048
DOI - 10.1093/nar/gkz230
Subject(s) - transfer rna , biology , methyltransferase , bacillus subtilis , biochemistry , wobble base pair , methylation , base pair , pseudouridine , stereochemistry , dna , rna , genetics , gene , chemistry , bacteria
1-Methyladenosine (m1A) is a modified nucleoside found at positions 9, 14, 22 and 58 of tRNAs, which arises from the transfer of a methyl group onto the N1-atom of adenosine. The yqfN gene of Bacillus subtilis encodes the methyltransferase TrmK (BsTrmK) responsible for the formation of m1A22 in tRNA. Here, we show that BsTrmK displays a broad substrate specificity, and methylates seven out of eight tRNA isoacceptor families of B. subtilis bearing an A22. In addition to a non-Watson-Crick base-pair between the target A22 and a purine at position 13, the formation of m1A22 by BsTrmK requires a full-length tRNA with intact tRNA elbow and anticodon stem. We solved the crystal structure of BsTrmK showing an N-terminal catalytic domain harbouring the typical Rossmann-like fold of Class-I methyltransferases and a C-terminal coiled-coil domain. We used NMR chemical shift mapping to drive the docking of BstRNASer to BsTrmK in complex with its methyl-donor cofactor S-adenosyl-L-methionine (SAM). In this model, validated by methyltransferase activity assays on BsTrmK mutants, both domains of BsTrmK participate in tRNA binding. BsTrmK recognises tRNA with very few structural changes in both partner, the non-Watson-Crick R13-A22 base-pair positioning the A22 N1-atom close to the SAM methyl group.