Effect of in vitro methylation on the chromatographic and coding properties of methyl-deficient leucine transfer RNA

Abstract

Whereas normal Escherichia coli leucyl-tRNA § § Abbreviations used: tRNA, transfer RNA; tRNA Leu the species of tRNA specific for leucine; leucyl-tRNA, tRNA to which leucine is bound; poly UG, a random copolymer of uridylic acid and guanylic acid; poly UC, B random copolymer of uridylic acid and cytidylic acid; RPC, reversephase chromatography; AMe, S-adenosylmethionine; MAK, methylated albumin-kieselguhr. , which contains several subspecies, responds equally efficiently in codon recognition studies with poly UG or poly UC, leucyl-tRNA preparations containing methyl-deficient tRNA Leu react more efficiently with poly UC than poly UG ( Capra & Peterkofsky, 1966). The increased reactivity with poly UC in these preparations is primarily associated with a chromatographic species of tRNA Leu singular to methyl-deficient tRNA ( Peterkofsky, 1964). The interpretation of these observations has, until now, been ambiguous. They could indicate that methyl-deficient tRNA preparations are enriched with those subspecies of tRNA Leu which normally interact with poly UC. Alternatively, it might be suggested that species of tRNA Leu which normally recognize poly UG exhibit a changed codon response to poly UC when they are methyl-deficient. The studies herein support the latter hypothesis. Whereas in vitro methylation of the subspecies of tRNA Leu corresponding to those found in normally methylated preparations has no effect on their properties, such a treatment of subspecies of tRNA Leu restricted to methyl-deficient tRNA leads to a change in their Chromatographic and coding properties.