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The zinc finger protein Ynr046w is plurifunctional and a component of the eRF1 methyltransferase in yeast

French National Centre for Scientific Research, Lutetia Parisorum, Île-de-France, France
Journal of Biological Chemistry (Impact Factor: 4.57). 12/2006; 281(47):36140-8. DOI: 10.1074/jbc.M608571200
Source: PubMed

ABSTRACT Protein release factor eRF1 in Saccharomyces cerevisiae, in complex with eRF3 and GTP, is methylated on a functionally crucial Gln residue by the S-adenosylmethionine-dependent methyltransferase Ydr140w. Here we show that eRF1 methylation, in addition to these previously characterized components, requires a 15-kDa zinc-binding protein, Ynr046w. Co-expression in Escherichia coli of Ynr046w and Ydr140w allows the latter to be recovered in soluble form rather than as inclusion bodies, and the two proteins co-purify on nickel-nitrilotriacetic acid chromatography when Ydr140w alone carries a His tag. The crystal structure of Ynr046w has been determined to 1.7 A resolution. It comprises a zinc-binding domain built from both the N- and C-terminal sequences and an inserted domain, absent from bacterial and archaeal orthologs of the protein, composed of three alpha-helices. The active methyltransferase is the heterodimer Ydr140w.Ynr046w, but when alone, both in solution and in crystals, Ynr046w appears to be a homodimer. The Ynr046w eRF1 methyltransferase subunit is shared by the tRNA methyltransferase Trm11p and probably by two other enzymes containing a Rossman fold.

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    • "In both bacteria and eukarya, this motif is post-translationally modified by methylation, one of the most common modifications after phosphorylation. The Gln side chain of this motif is converted into N 5 methyl-glutamine by specific protein methyltransferases (MTases): PrmC in Escherichia coli or the Mtq2-Trm112 complex in Saccharomyces cerevisiae [5] [6]. "
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    • "The enzyme itself is an heterodimer made of two subunits: Mtq2p carrying the catalytic and AdoMet binding sites, and Trm112p (Ynr046wp), a small zinc finger protein, necessary for the solubility and activity of the catalytic subunit [7]. Mammalian genomes encode proteins sharing homology with Mtq2p, the function of which is unknown although they are annotated as N6-adenine MTases. "
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