In vitro O2′-methylation of sugars in E. coli RNA. II. Methylation of ribosomal and transfer RNA by homologous methylases in crude cell-free extracts and particulate suspensions from a relaxed mutant of E. coli

(1) The ribosomal and transfer ribonucleates (rRNA and tRNA) from a relaxed strain of E. coli have been methylated in vivo, by growing the organism in a medium containing methyl- 14 C-methionine, and in vitro, by incubating cell-free preparations from both methionine-sufficient and methionine-deprived cultures with methyl- 14 C-S-adenosyl methionine.(2) Six base-methylated derivatives that were labeled in vivo were also found to be methylated in vitro. Three base-methylated components known to be present in E. coli RNA were not included in the present survey.(3) Seven sugar-methylated derivatives were labeled in vivo but only three of these were efficiently methylated, in vitro.(4) Ribose residues in "undermethylated" rRNA and tRNA can be O 2 ′-methylated under the influence of homologous methylases when cell-free preparations are supplemented with S-adenosyl methionine.