{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,9]],"date-time":"2026-04-09T05:48:44Z","timestamp":1775713724378,"version":"3.50.1"},"reference-count":36,"publisher":"Proceedings of the National Academy of Sciences","issue":"18","content-domain":{"domain":["www.pnas.org"],"crossmark-restriction":true},"short-container-title":["Proc. Natl. Acad. Sci. U.S.A."],"published-print":{"date-parts":[[1997,9,2]]},"abstract":"<jats:p>\n            The m\n            <jats:sup>7<\/jats:sup>\n            GpppN cap structure of eukaryotic mRNA is formed cotranscriptionally by the sequential action of three enzymes: RNA triphosphatase, RNA guanylyltransferase, and RNA (guanine-7)-methyltransferase. A multifunctional polypeptide containing all three active sites is encoded by vaccinia virus. In contrast, fungi and\n            <jats:italic>Chlorella<\/jats:italic>\n            virus encode monofunctional guanylyltransferase polypeptides that lack triphosphatase and methyltransferase activities. Transguanylylation is a two-stage reaction involving a covalent enzyme-GMP intermediate. The active site is composed of six protein motifs that are conserved in order and spacing among yeast and DNA virus capping enzymes. We performed a structure\u2013function analysis of the six motifs by targeted mutagenesis of Ceg1, the\n            <jats:italic>Saccharomyces cerevisiae<\/jats:italic>\n            guanylyltransferase. Essential acidic, basic, and aromatic functional groups were identified. The structural basis for covalent catalysis was illuminated by comparing the mutational results with the crystal structure of the\n            <jats:italic>Chlorella<\/jats:italic>\n            virus capping enzyme. The results also allowed us to identify the capping enzyme of\n            <jats:italic>Caenorhabditis elegans<\/jats:italic>\n            . The 573-amino acid nematode protein consists of a C-terminal guanylyltransferase domain, which is homologous to Ceg1 and is strictly conserved with respect to all 16 amino acids that are essential for Ceg1 function, and an N-terminal phosphatase domain that bears no resemblance to the vaccinia triphosphatase domain but, instead, has strong similarity to the superfamily of protein phosphatases that act via a covalent phosphocysteine intermediate.\n          <\/jats:p>","DOI":"10.1073\/pnas.94.18.9573","type":"journal-article","created":{"date-parts":[[2002,7,26]],"date-time":"2002-07-26T14:31:44Z","timestamp":1027693904000},"page":"9573-9578","update-policy":"https:\/\/doi.org\/10.1073\/pnas.cm10313","source":"Crossref","is-referenced-by-count":100,"title":["Phylogeny of mRNA capping\u2009enzymes"],"prefix":"10.1073","volume":"94","author":[{"given":"Shuang Ping","family":"Wang","sequence":"first","affiliation":[{"name":"Molecular Biology Program, Sloan\u2013Kettering Institute, New York, NY 10021"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Liang","family":"Deng","sequence":"additional","affiliation":[{"name":"Molecular Biology Program, Sloan\u2013Kettering Institute, New York, NY 10021"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"C. 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