title: 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 tRNAIle requires enzymatic 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 [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 tRNAIle than in the biosynthesis of tRNAPro.
mesh_terms: D001483:Base Sequence; D003090:Coliphages; D004926:Escherichia coli / Q000201:enzymology*; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology; D009843:Oligoribonucleotides / Q000032:analysis; D011392:Proline; D012343:RNA, Transfer; D012260:Ribonucleases / Q000302:isolation & purification / Q000378:metabolism*
chemical_list: D009843:Oligoribonucleotides; D012343:RNA, Transfer; D011392:Proline; D012260:Ribonucleases; D008274:Magnesium