title: Eukaryotic mRNA capping enzyme-guanylate covalent intermediate.
abstract: Incubation of HeLa cell mRNA guanylyltransferase (GTP:mRNA guanylyltransferase, EC 2.7.7.50) with [alpha-32P]GTP and a divalent cation in the absence of an RNA acceptor results in the formation of a covalent enzyme-guanylate complex. The complex, after purification by phosphocellulose chromatography, can transfer its bound GMP moiety to pyrophosphate, regenerating GTP, or to the 5'-diphosphate end of poly(A), forming a cap structure G(5')pppA(pA)n. The GMP-polypeptide has a molecular weight of 65,000 and is stable to heating in the presence of sodium dodecyl sulfate. On the basis of the alkali-stable and acid-labile nature of the bond and its susceptibility to nucleophilic attack by hydroxylamine at low pH, the GMP-polypeptide linkage appears to be a phosphoamine bond. After digestion with trypsin, a single GMP-peptide was resolved by two dimensional electrophoresis and chromatography.
mesh_terms: D006150:Guanine Nucleotides / Q000378:metabolism*; D006157:Guanosine Monophosphate / Q000378:metabolism*; D006367:HeLa Cells / Q000201:enzymology*; D006801:Humans; D009713:Nucleotidyltransferases / Q000378:metabolism*; D010446:Peptide Fragments / Q000032:analysis; D012315:RNA Caps / Q000096:biosynthesis*; D013379:Substrate Specificity; D000098556:mRNA Guanylyltransferases
chemical_list: D006150:Guanine Nucleotides; D010446:Peptide Fragments; D012315:RNA Caps; D006157:Guanosine Monophosphate; D009713:Nucleotidyltransferases; D000098556:mRNA Guanylyltransferases