An Escherichia coli ribonuclease which removes an extra nucleotide from a biosynthetic intermediate of bacteriophage T4 proline transfer RNA

Abstract
The biosynthesis of bacteriophage T4 tRNAPro, tRNASer and tRNAI1e requires enzymstic removal of extra nucleotides from the 3′ terminus of the respective precursor RNAs. A ribonuclease activity capable of catalyzing such reactions has been partially purified from uninfected Escherichia coli using an artificial precursor RNA as substrate. A number of ribonuclease activities were resolved during purification. Use of E. coli strain BN, a mutant known to be deficient in the relevant ribonuclease activity, permitted us to identify it in wild-type cells. This activity was designated the BN ribonuclease. BN ribonuclease had an apparent molecular weight of 35,000 as measured by Sephadex gel filtration. Mg2+ was required for activity, which was optimal at of [Mg2+] of 2mM. Activity did not require monovalent cations K+ or Na+. BN ribonuclease was less efficient at removing extra residues in the biosynthesis of tRNASer and RNAI1e than in the biosynthesis of RNAPro.