Conformational changes of yeast tRNAPhe and E. coli tRNA2Glu as indicated by different nuclease digestion patterns.

The susceptibility of yeast tRNAPhe and Escherichia coli tRNA2Glu to digestion by nucleases Tl and Sl are examined in a variety of environments, and the results are interpreted in view of the available three-dimensional structural information. Significant differences are found in the digestion pattern of the two tRNAs using the guanosine-specific Tl nuclease. In particular, differences are seen due to varying the type of salts in the environment. However, the Sl nuclease results on the two tRNAs do not differ greatly. E. coli tRNA2Glu is known to exist in two different conformations. Nuclease digestion results are presented revealing differences which make it possible to draw some inferences about the structural differences in these two conformations. In carrying out these analyses, the tRNA molecules are labeled either by putting 32P at the 5'-end of the molecular or by adding 32P-labeled pCp at the 3'-end. It is found that both yeast tRNAPhe and E. coli tRNA2Glu have modified Tl nuclease digestion patterns when pCp is added at the 3'-end of the molecule.