Isolation and characterization of a tRNA(guanine-7-)-methyltransferase fromSalmonella typhimurium

✍ Scribed by Alfredo Colonna; Gennaro Ciliberto; Rita Santamaria; Filiberto Cimino; Francesco Salvatore

• Book ID: 104671406
• Publisher: Springer
• Year: 1983
• Tongue: English
• Weight: 671 KB
• Volume: 52
• Category: Article
• ISSN: 0300-8177
• DOI: 10.1007/bf00224919

✦ Synopsis

The tRNA modifying enzyme, S-adenosylmethionine:tRNA(guanine-7-)-methyltransferase, has been extensively purified from Salmonella typhimurium. A rapid and efficient purification method using phosphocellulose chromatography followed by ammonium sulfate precipitation and Sephadex G-100 gel filtration is described. The enzyme appears to be a single polypeptide chain with a molecular weight of approximately 25 000--30 000 daltons. The Km for S-adenosylmethionine and for undermethylated tRNA is 53 microM and 3.4 microM, respectively. The methylation reaction is dependent on added monovalent or divalent cations; 5 mM spermidine, 3 mM MgCl2 and 1 mM spermine are the most effective. The enzyme, though not homogeneous, is free from contaminating ribonucleases and other tRNA methyltransferases.