ROLE OF RIBOTHYMIDINE IN THE THERMAL-STABILITY OF TRANSFER-RNA AS MONITORED BY PROTON MAGNETIC-RESONANCE

In order to elucidate the functional role of the modified uridines at position 54 of tRNA, the 270 MHz high-field proton NMR spectra of methionine tRNAs from E.coli, from a mutant thereof, and from T. thermophilus, containing ribothymidine, uridine and 2-thioribothymidine, respectively, have been measured as a function of temperature. A comparison of the NMR melting profiles of the minor nucleosides from these tRNAs shows that the melting temperature of the uridine containing tRNA is 6°C lower than that of the wild type tRNA whereas that of the 2-thioribothymidine tRNA 1s 7°C higher than that of the wild type tRNA. These results, therefore, demonstrate that these modifications serve for stabilization of the tertiary structure of tRNA. © 1979 Information Retrieval Limited.