
The modified nucleoside 1-methyladenosine (m(1)A) is found in the T-loop of many tRNAs from organisms belonging to the three domains of life (Eukaryota, Bacteria, Archaea). In the T-loop of eukaryotic and bacterial tRNAs, m(1)A is present at position 58, whereas in archaeal tRNAs it is present at position(s) 58 and/or 57, m(1)A57 being the obligatory intermediate in the biosynthesis of 1-methylinosine (m(1)I57). In yeast, the formation of m(1)A58 is catalysed by the essential tRNA (m(1)A58) methyltransferase (MTase), a tetrameric enzyme that is composed of two types of subunits (Gcd14p and Gcd10p), whereas in the bacterium Thermus thermophilus the enzyme is a homotetramer of the TrmI polypeptide. Here, we report that the TrmI enzyme from the archaeon Pyrococcus abyssi is also a homotetramer. However, unlike the bacterial site-specific TrmI MTase, the P.abyssi enzyme is region-specific and catalyses the formation of m(1)A at two adjacent positions (57 and 58) in the T-loop of certain tRNAs. The stabilisation of P.abyssi TrmI at extreme temperatures involves intersubunit disulphide bridges that reinforce the tetrameric oligomerisation, as revealed by biochemical and crystallographic evidences. The origin and evolution of m(1)A MTases is discussed in the context of different hypotheses of the tree of life.
Models, Molecular, Disulfides -- metabolism, Protein Structure, Pyrococcus abyssi, Hot Temperature, Evolution, tRNA Methyltransferases -- metabolism, Molecular Sequence Data, Pyrococcus abyssi -- genetics, Protein Subunits -- metabolism, Crystallography, X-Ray, Catalysis, Substrate Specificity, Quaternary, Evolution, Molecular, Open Reading Frames, RNA, Transfer, Models, Catalytic Domain, Enzyme Stability, Amino Acid Sequence, Disulfides, Protein Structure, Quaternary, tRNA Methyltransferases -- chemistry, tRNA Methyltransferases, Crystallography, Pyrococcus abyssi -- enzymology, Disulfides -- chemistry, Open Reading Frames -- genetics, Transfer -- metabolism, Molecular, Sciences bio-médicales et agricoles, Protein Subunits -- genetics, Protein Subunits -- chemistry, Protein Subunits, X-Ray, RNA, tRNA Methyltransferases -- genetics
Models, Molecular, Disulfides -- metabolism, Protein Structure, Pyrococcus abyssi, Hot Temperature, Evolution, tRNA Methyltransferases -- metabolism, Molecular Sequence Data, Pyrococcus abyssi -- genetics, Protein Subunits -- metabolism, Crystallography, X-Ray, Catalysis, Substrate Specificity, Quaternary, Evolution, Molecular, Open Reading Frames, RNA, Transfer, Models, Catalytic Domain, Enzyme Stability, Amino Acid Sequence, Disulfides, Protein Structure, Quaternary, tRNA Methyltransferases -- chemistry, tRNA Methyltransferases, Crystallography, Pyrococcus abyssi -- enzymology, Disulfides -- chemistry, Open Reading Frames -- genetics, Transfer -- metabolism, Molecular, Sciences bio-médicales et agricoles, Protein Subunits -- genetics, Protein Subunits -- chemistry, Protein Subunits, X-Ray, RNA, tRNA Methyltransferases -- genetics
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