title: Crystal structures of the tRNA:m2G6 methyltransferase Trm14/TrmN from two domains of life.
abstract: Methyltransferases (MTases) form a major class of tRNA-modifying enzymes needed for the proper functioning of tRNA. Recently, RNA MTases from the TrmN/Trm14 family that are present in Archaea, Bacteria and Eukaryota have been shown to specifically modify tRNA(Phe) at guanosine 6 in the tRNA acceptor stem. Here, we report the first X-ray crystal structures of the tRNA m(2)G6 (N(2)-methylguanosine) MTase (TTC)TrmN from Thermus thermophilus and its ortholog (Pf)Trm14 from Pyrococcus furiosus. Structures of (Pf)Trm14 were solved in complex with the methyl donor S-adenosyl-l-methionine (SAM or AdoMet), as well as the reaction product S-adenosyl-homocysteine (SAH or AdoHcy) and the inhibitor sinefungin. (TTC)TrmN and (Pf)Trm14 consist of an N-terminal THUMP domain fused to a catalytic Rossmann-fold MTase (RFM) domain. These results represent the first crystallographic structure analysis of proteins containing both THUMP and RFM domain, and hence provide further insight in the contribution of the THUMP domain in tRNA recognition and catalysis. Electrostatics and conservation calculations suggest a main tRNA binding surface in a groove between the THUMP domain and the MTase domain. This is further supported by a docking model of TrmN in complex with tRNA(Phe) of T. thermophilus and via site-directed mutagenesis.
authors.affiliation: VIB Department of Structural Biology, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussel, Belgium.
authors.forename: Marcus
authors.initials: M
authors.lastname: Fislage
authors.forename: Martine
authors.initials: M
authors.lastname: Roovers
authors.forename: Irina
authors.initials: I
authors.lastname: Tuszynska
authors.forename: Janusz M
authors.initials: JM
authors.lastname: Bujnicki
authors.forename: Louis
authors.initials: L
authors.lastname: Droogmans
authors.forename: Wim
authors.initials: W
authors.lastname: Versées
mesh_terms: D000595:Amino Acid Sequence; D019843:Archaeal Proteins / Q000737:chemistry* / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism; D001665:Binding Sites; D018360:Crystallography, X-Ray; D006151:Guanosine / Q000737:chemistry; D008024:Ligands; D008958:Models, Molecular; D008969:Molecular Sequence Data; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D020027:Pyrococcus furiosus / Q000201:enzymology; D016415:Sequence Alignment; D016963:Thermus thermophilus / Q000201:enzymology; D012359:tRNA Methyltransferases / Q000737:chemistry* / Q000378:metabolism
chemical_list: D019843:Archaeal Proteins; D001426:Bacterial Proteins; D008024:Ligands; D006151:Guanosine; D012359:tRNA Methyltransferases