Effect of the removal of the Y base on the conformation of yeast tRNA.

The effect of removing the Y base from the anticodon loop of yeast tRNA(Phe) has been examined by high-resolution proton nuclear magnetic resonance spectroscopy and optical melting. Analysis of the changes in the nuclear magnetic resonance spectra indicate that the removal of the Y base produces a small conformational change in the anticodon stem in which all the interbase separations are increased by approximately 0.2 A. The temperature dependence of the nuclear magnetic resonance spectra and the optical melting measurements indicate that the high temperature stability of tRNA(Phe) is decreased by removal of the Y base. With the exception of the anticodon stem, the secondary structure of the other helical stems of the molecule appear to be unaltered when the Y base is excised.