title: Isolation and characterization of a tRNA(guanine-7-)-methyltransferase from Salmonella typhimurium.
abstract: 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.
mesh_terms: D002850:Chromatography, Gel; D007700:Kinetics; D008274:Magnesium / Q000378:metabolism; D015636:Magnesium Chloride; D008970:Molecular Weight; D012343:RNA, Transfer / Q000378:metabolism; D012436:S-Adenosylmethionine / Q000378:metabolism; D012486:Salmonella typhimurium / Q000201:enzymology*; D013095:Spermidine / Q000378:metabolism; D013096:Spermine / Q000378:metabolism; D012359:tRNA Methyltransferases / Q000302:isolation & purification* / Q000378:metabolism
chemical_list: D015636:Magnesium Chloride; D013096:Spermine; D012436:S-Adenosylmethionine; D012343:RNA, Transfer; D012359:tRNA Methyltransferases; C036814:tRNA (guanine-N7-)-methyltransferase; D008274:Magnesium; D013095:Spermidine