Phylogeny of mRNA capping enzymes.

ABSTRACT: The m7GpppN 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 Chlorella 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-function analysis of the six motifs by targeted mutagenesis of Ceg1, the Saccharomyces cerevisiae guanyl

SUBMITTER: Wang SP 

PROVIDER: S-EPMC23221 | biostudies-literature | 1997 Sep

REPOSITORIES: biostudies-literature