title: A single tRNA (guanine)-methyltransferase from Tetrahymena with both mono- and di-methylating activity.
abstract: A tRNA (guanine-2) methyltransferase has been purified to homogeneity from the protozoan Tetrahymena pyriformis. The enzyme methylates purified E. coli tRNAs which have a guanine residue at position 26 from the 5' end; it also methylates tRNA prepared from the m22G- yeast mutant trm 1. This methyltransferase is therefore equivalent to the guanine methyltransferase 2mGII found in mammalian extracts. The purified 2mGII from Tetrahymena is capable of forming both N2-methylguanine and N22-dimethylguanine on a single tRNA isoaccepting species; under conditions of limiting tRNA or long reaction times the predominant product is dimethylguanine. Analysis of the products formed under varying reaction conditions suggests that dimethylguanine formation is a two step process requiring dissociation of the enzyme-monomethylated tRNA intermediate.
authors.forename: M P
authors.initials: MP
authors.lastname: Reinhart
authors.forename: J M
authors.initials: JM
authors.lastname: Lewis
authors.forename: P S
authors.initials: PS
authors.lastname: Leboy
mesh_terms: D000818:Animals; D002848:Chromatography, DEAE-Cellulose; D004789:Enzyme Activation; D008274:Magnesium / Q000378:metabolism; D008745:Methylation; D012343:RNA, Transfer / Q000378:metabolism; D013379:Substrate Specificity; D013769:Tetrahymena pyriformis / Q000201:enzymology*; D012359:tRNA Methyltransferases / Q000302:isolation & purification* / Q000378:metabolism
chemical_list: D012343:RNA, Transfer; D012359:tRNA Methyltransferases; C023196:tRNA (guanine(10)-N(2))-dimethyltransferase; D008274:Magnesium