TRNA methylation from another

The uncertainty probably has its origin in the fact that the only readily available undermethylated tRNA (which is about 50% methylated) for in vitro studies is that obtained from an E. coli RC" methionine auxotroph following methionine starvation. It is known that tRNA from one organism can usually be hypermethylated by tRNA methylases from another this use of heterologous tRNA, therefore, may... 

Two types of rRNA methylases have been purified, one with catalytic properties restricted to rRNA, and another that acts on both rRNA and tRNA. A bacterial preparation capable of methylating either adenine or cytosine of DNA has been purified. But although it is most likely that the enzyme methylating adenine (N-C bond) is different from that methylating cytosine (C-C bond), successful separation has not been accomplished. Almost nothing is known of the enzymes catalyzing 0 methyl riboside formation. 

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