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The Zinc Finger Protein Ynr046w Is Plurifunctional and a Component of the eRF1 Methyltransferase in Yeast

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Heurgué-Hamard, Valérie | Graille, Marc | Scrima, Nathalie | Ulryck, Nathalie | Champ, Stéphanie | van Tilbeurgh, Herman | Buckingham, Richard, H

Edité par CCSD ; American Society for Biochemistry and Molecular Biology -

International audience. 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 Å 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 ␣-helices. The active methyltransferase is the heterodimer Ydr140w⅐Ynr046w, 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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