Role of ribothymidine in mammalian tRNAPhe.

Publisher Website
Google Scholar
Abstract
Mammalian tRNAPhe from various tissues contain different amounts of ribothymidine; a uridine methylase from Escherichia coli can quantitatively convert these tRNA to species that contain their full complement of ribothymidine at position 23 from the 3'' terminus. The role of ribothymidine in mammalian tRNA was investigated by studying the ability of several highly purified mammalian tRNAPhe [rat and beef liver, human placenta], differing only in their ribothymidine content, to support poly(U)-directed poly(Phe) synthesis under various conditions. The results indicate that the ribothymidine content of mammalian tRNAPhe can be correlated with the ability of these tRNA to function in vitro in a low-Mg (6 mM), ribosome wash factor-dependent, poly(U)-directed poly(Phe) synthesis system from rat liver. Specifically, the effect of increasing the ribothymidine content in a class C mammalian tRNA becomes manifest in an increased apparent Vmax for the overall synthesis of poly(Phe), while the apparent Km remains essentially unchanged. It is postulated that the modified nucleoside ribothymidine might be involved in the regulation of protein synthesis at the level of translation in mammalian liver.