Active site of the mRNA-capping enzyme guanylyltransferase from Saccharomyces cerevisiae: similarity to the nucleotidyl attachment motif of DNA and RNA ligases.
Nascent mRNA chains are capped at the 5' end by the addition of a guanylyl residue to form a G(5')ppp(5')N ... structure. During the capping reaction, the guanylyltransferase (GTP:mRNA guanylyltransferase, EC 2.7.7.50) is reversibly and covalently guanylylated. In this enzyme-GMP (E-GMP) intermediate, GMP is linked to the epsilon-amino group of a lysine residue via a phosphoamide bond. Lys-70 was identified as the GMP attachment site of the Saccharomyces cerevisiae guanylyltransferase (encoded by the CEG1 gene) by guanylylpeptide sequencing. CEG1 genes with substitutions at Lys-70 were unable to support viability in yeast and produced proteins that were not guanylylated in vitro. The CEG1 active site exhibits sequence similarity to the active sites of viral guanylyltransferases and polynucleotide ligases, suggesting similarity in the mechanisms of nucleotidyl transfer catalyzed by these enzymes.
Fresco
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LD
Whitehead Institute for Biomedical Research, Cambridge, MA 02142.
Buratowski
S
S
D000595:Amino Acid Sequence; D001419:Bacteria / Q000201:enzymology; D001483:Base Sequence; D001665:Binding Sites; D011088:DNA Ligases / Q000096:biosynthesis / Q000737:chemistry*; D017931:DNA Primers; D005800:Genes, Fungal; D008969:Molecular Sequence Data; D009713:Nucleotidyltransferases / Q000096:biosynthesis / Q000737:chemistry* / Q000378:metabolism; D016133:Polymerase Chain Reaction; D011130:RNA Ligase (ATP) / Q000096:biosynthesis / Q000737:chemistry*; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000235:genetics*; D017386:Sequence Homology, Amino Acid; D014780:Viruses / Q000201:enzymology; D000098556:mRNA Guanylyltransferases
D017931:DNA Primers; D011994:Recombinant Proteins; D009713:Nucleotidyltransferases; D000098556:mRNA Guanylyltransferases; D011088:DNA Ligases; D011130:RNA Ligase (ATP)