OLIGORIBONUCLEASE IS DISTINCT FROM THE OTHER KNOWN EXORIBONUCLEASES OF ESCHERICHIA-COLI

Oligoribonuclease, an exoribonuclease specific for small oligoribonucl eotides, was initially characterized 20 years ago (S. K. Niyogi and A. K. Datta, J. Biol. Chem. 250:7307-7312, 1975) and shown to be differe nt from RNase II and polynucleotide phosphorylase. Here we demonstrate , using mutant strains and purified enzymes, that oligoribonuclease is not a manifestation of RNases D, BN, T, PH, and R, exoribonucleases d iscovered subsequently. Thus, oligoribonuclease is the eighth distinct exoribonuclease discovered in Escherichia coli. We also show that oli goribonuclease copurifies with polynucleotide phosphorylase.