Ezraty Benjamin, Dahlgren Brian, Deutscher Murray P
Department of Biochemistry and Molecular Biology, University of Miami School of Medicine, Miami, Florida 33101, USA.
J Biol Chem. 2005 Apr 29;280(17):16542-5. doi: 10.1074/jbc.C500098200. Epub 2005 Mar 10.
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 RNase BN mutation has now been identified, we propose that the elaC gene be renamed rbn.
在真核生物、古细菌以及某些真细菌中,tRNA成熟过程中3'前体序列的去除由一种内切核糖核酸酶催化,该酶称为核糖核酸酶Z(RNase Z)。相比之下,在大肠杆菌中,多种外切核糖核酸酶负责最终的3'端成熟。然而,大肠杆菌保留了一种核糖核酸酶Z同源物ElaC,其功能正在积极研究中。我们已经对带有His标签的ElaC进行了过表达并纯化至同质状态,在此表明它实际上就是先前描述的酶核糖核酸酶BN(RNase BN)。因此,纯化后的ElaC展现出与核糖核酸酶BN相同的结构和催化特性。此外,一个elaC突变菌株的行为与已知的核糖核酸酶BN缺失菌株CAN相同。最后,我们表明野生型elaC可以弥补CAN菌株中的突变,并且CAN菌株中的elaC基因携带一个无义突变,导致核糖核酸酶BN活性丧失。这些数据纠正了先前对编码核糖核酸酶BN基因的错误认定。基于现在已经鉴定出原始核糖核酸酶BN突变这一事实,我们提议将elaC基因重新命名为rbn。