title: A primordial RNA modification enzyme: the case of tRNA (m1A) methyltransferase.
abstract: 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.
authors.affiliation: Laboratoire de Microbiologie, Université Libre de Bruxelles, Belgium.
authors.forename: Martine
authors.initials: M
authors.lastname: Roovers
authors.forename: Johan
authors.initials: J
authors.lastname: Wouters
authors.forename: Janusz M
authors.initials: JM
authors.lastname: Bujnicki
authors.forename: Catherine
authors.initials: C
authors.lastname: Tricot
authors.forename: Victor
authors.initials: V
authors.lastname: Stalon
authors.forename: Henri
authors.initials: H
authors.lastname: Grosjean
authors.forename: Louis
authors.initials: L
authors.lastname: Droogmans
mesh_terms: D000595:Amino Acid Sequence; D002384:Catalysis; D020134:Catalytic Domain; D003461:Crystallography; D018360:Crystallography, X-Ray; D004220:Disulfides / Q000737:chemistry / Q000378:metabolism; D004795:Enzyme Stability; D019143:Evolution, Molecular; D006358:Hot Temperature; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016366:Open Reading Frames / Q000235:genetics; D020836:Protein Structure, Quaternary; D021122:Protein Subunits / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D043903:Pyrococcus abyssi / Q000201:enzymology* / Q000235:genetics; D012343:RNA, Transfer / Q000378:metabolism*; D013379:Substrate Specificity; D012359:tRNA Methyltransferases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*
chemical_list: D004220:Disulfides; D021122:Protein Subunits; D012343:RNA, Transfer; D012359:tRNA Methyltransferases; C023194:tRNA (adenine(58)-N(1))-methyltransferase