The RNase Z homologue encoded by Escherichia coli elaC gene is RNase BN

Abstract

In eukaryotes, archaea, and in some eubacteria, removal of 3′ precursor sequences during maturation of tRNA is catalyzed by an endoribonuclease, termed RNase Z. In contrast, in Escherichia, coli, a variety of exoribonucleases carry out final 3′ maturation. Yet, E. coli retains an. RNase Z homologue, ElaC, whose function is under active study. We have overexpressed and purified to homogeneity His-tagged ElaC and show here that it is, in fact, the previously described enzyme, RNase BN. Thus, purified ElaC displays structural and catalytic properties identical to those ascribed to RNase BN. In addition, an elaC mutant strain behaves identically to a known RNase BN- strain, CAN. Finally, we show that wild type elaC can complement the mutation, in strain CAN and that the elaC gene in strain CAN carries a nonsense mutation that results in loss of RNase BN activity. These data correct a previous misassignment for the gene encoding RNase BN. Based on the fact that the original MNase BN imitation has now been identified, we propose that the elaC gene be renamed rbn. © 2005 by The American Society for Biochemistry and Molecular Biology, Inc.