FIGURE 3.

Maturation of tRNA^PheV precursor by RNase BN. A, shown is the structure of the E. coli tRNA^Phe precursor. The discriminator nucleotide is shown in boldface. B, the tRNA^Phe precursor (0.05 μm) with 6 extra 3′-residues after the CCA sequence was treated with RNase BN (0.14 μm), and the cleavage products were analyzed by 6% denaturing PAGE, followed by Northern blotting with a 5′-probe. C, the conditions were the same as described for B except that the precursor has 3 extra 3′-nt. D, the conditions were the same as described for B except that the substrate was mature (M) tRNA^Phe. E and F, tRNA^Phe labeled with [³²P]pC at its 3′-end (48 nm) was treated with RNase BN (0.14 μm) in the presence of either Co²⁺ at pH 6.5 (E) or Mg²⁺ at pH 7.5 (F). The cleavage products were analyzed by 20% denaturing PAGE. Quantitation of the data from experiments similar to those in E and F is shown below the gels. Disappearance of the precursor (P) (■) and generation of CMP (▴) and 7-nt oligomer (○) products are presented as a percentage of the initial amount of precursor.