Figure 3.

Properties of active tRNA clones. (A) Colony growth of different tRNA clones in XAC-1. Newly transformed colonies were replated on M9 minimal medium with ampicillin (50 μg/ml), without arginine, and with or without X-Gal (20 μg/ml). Ala represents the plasmid containing the tRNA_su+^Ala gene; Phe, the tRNA^Phe suppressor gene; and “−,” the plasmid with no insert. The top image is the clone index; the middle shows colony growth in the presence of X-Gal with no added arginine; and the bottom shows growth in the absence of X-Gal and arginine. (B) Aminoacylation levels of various tRNA clones. Total RNA was isolated from different clones. One sample of each was treated with Tris (pH 9) and then analyzed with a second, untreated sample on a 6.5% polyacrylamide gel at pH 5.2 (see Materials and Methods). Lanes containing samples which were treated with Tris are indicated by “+,” and those which were untreated are indicated by “−.” Northern blot hybridization was carried out with a probe representing the anticodon part of the tRNA library and with a 5S probe. The percentage of aminoacylation was calculated by determining the intensity of the bands representing the aminoacylated and nonaminoacylated species. The levels of expression were determined in the same way and normalized to the level of the 5S RNA in each lane.