Figure 3.

Northern blot showing the presence in the cytosol and the level of aminoacylation of some suppressor tRNAs. For each clone the – and + lanes correspond to the samples not treated and treated with Tris. In the – lanes the aminoacylated and deacylated forms of the suppressor tRNA move as individual bands, while in the + lanes the total tRNA is deacylated and the suppressor tRNA moves as one band. In all – lanes the bands corresponding to the aminoacylated form of the tRNA are much larger than those corresponding to the deacylated form and are comparable to the bands in the + lanes, representing the total amount of the suppressor tRNA. This indicates that in all clones most of the tRNA is present in the aminoacylated form. A smaller size of the bands of the suppressor tRNAs compared to tRNA^Ala_su+ indicates a notably lower presence of the selected tRNAs in the cytosol. 5S rRNA was visualized to monitor the amount of total RNA in each sample. Because the signal from 5S rRNA was much stronger than that from suppressor tRNAs, the upper and lower parts of the same membrane have been exposed, respectively, for 4 h and overnight. The nucleotide sequence of clone K8, due to its low β-galactosidase activity, is not included in Table 1, but is available upon request.