Reinhart MP, Lewis JM, Leboy PS. A single tRNA (guanine)-methyltransferase from Tetrahymena with both mono- and di-methylating activity.
Nucleic Acids Res 1986;
14:1131-48. [PMID:
3081876 PMCID:
PMC339493 DOI:
10.1093/nar/14.3.1131]
[Citation(s) in RCA: 29] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
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.
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