Minor conformational changes of yeast tRNAPhe anticodon loop occur upon aminoacylation as indicated by Y base fluorescence.

The Y base fluorescence of highly purified yeast tRNAPhe was measured in order to detect possible conformational changes of the anticodon loop, which were induced as a consequence of aminoacylation. A small enhancement of Y base fluorescence intensity in the order of 5% was observed in situ during aminoacylation. The rotational mobility of the Y base of Phe-tRNAPhe and tRNAPhe was determined by measuring the fluorescence polarization at various temperatures between 5 degrees C and 35 degrees C. Differences in the fluorescence polarization of the Y base between these tRNAs were however not observed. These results confirm that minor changes in the microenvironment of the Y base occur upon aminoacylation, whereas significant conformational changes of the anticodon loop can be excluded.