title: Characterization of S-adenosylmethionine: ribosomal ribonucleic acid-adenine (N 6 -) methyltransferase of Escherichia coli strain B.
abstract: This study is concerned with the isolation and characterization of the enzyme, S-adenosylmethionine:ribosomal ribonucleic acid-adenine (N(6-)) methyl-transferase [rRNA-adenine (N(6)-) methylase] of Escherichia coli strain B, which is responsible for the formation of N(6)-methyladenine moieties in ribosomal ribonucleic acids (rRNA). A 1,500-fold purified preparation of the species-specific methyltransferase methylates a limited number of adenine moieties in heterologous rRNA (Micrococcus lysodeikticus and Bacillus subtilis) and methyl-deficient homologous rRNA. The site recognition mechanism does not require intact 16 or 23S rRNA. The enzyme does not utilize transfer ribonucleic acid as a methyl acceptor nor does it synthesize 2-methyladenine or N(6)-dimethyladenine moieties. Mg(2+), spermine, K(+), and Na(+) increase the reaction rate but not the extent of methylation; elevated concentrations of the cations inhibit markedly. The purified preparations utilize 9-beta-ribosyl-2,6-diaminopurine (DAPR) as a methyl acceptor with the synthesis of 9-beta-ribosyl-6-amino-2-methylaminopurine. A comparison of the two activities demonstrated that one methyltransferase is responsible for the methylation of both DAPR and rRNA. This property provides a sensitive assay procedure unaffected by ribonucleases and independent of any specificity exhibited by rRNA methyl acceptors.
mesh_terms: D000225:Adenine; D000227:Adenine Nucleotides; D001412:Bacillus subtilis; D001665:Binding Sites; D002130:Calcium Phosphates; D002247:Carbon Isotopes; D002852:Chromatography, Ion Exchange; D002854:Chromatography, Paper; D004790:Enzyme Induction; D004926:Escherichia coli / Q000166:cytology / Q000201:enzymology*; D005782:Gels; D008274:Magnesium; D008780:Methyltransferases / Q000037:antagonists & inhibitors / Q000302:isolation & purification; D008837:Micrococcus; D011188:Potassium; D012335:RNA, Ribosomal; D012343:RNA, Transfer; D012270:Ribosomes / Q000201:enzymology*; D012436:S-Adenosylmethionine; D012964:Sodium; D013096:Spermine; D014316:Tritium
chemical_list: D000227:Adenine Nucleotides; D002130:Calcium Phosphates; D002247:Carbon Isotopes; D005782:Gels; D012335:RNA, Ribosomal; D014316:Tritium; D013096:Spermine; D012436:S-Adenosylmethionine; D012343:RNA, Transfer; D012964:Sodium; D008780:Methyltransferases; D008274:Magnesium; D000225:Adenine; D011188:Potassium