Enzymatic synthesis of chimeric tRNAs with unusual numbers of base pairs in the anticodon stem; their structure and properties.

Chimeric tRNATyr molecules have been constructed by enzymatic procedures in vitro from the 5'-half fragment of T. utilis tRNATyr and the 3'-half fragment of yeast tRNATyr, and vice versa. These chimeric tRNAs contain base-mismatching(s) in the anticodon stem and, therefore, have only 3 or 4 base pairs in the stem. Although the Tm of these chimeras are largely decreased, there seems to be no gross difference between the structure of native and chimeric tRNATyrs at physiological temperatures in the presence of 10 mM MgCl2. Aminoacylation assays also revealed that the tyrosine-acceptance of the chimeras are fully comparable to that of native tRNATyrs. However, the possibility remains that the properties of the chimeras are considerably different from those of native ones at lower Mg++ concentrations.