From Emerald Bio, Bainbridge Island, Washington 98110.
J Biol Chem. 2014 Jan 24;289(4):2139-47. doi: 10.1074/jbc.M113.525683. Epub 2013 Dec 4.
Ribonucleases (RNases) maintain the cellular RNA pool by RNA processing and degradation. In many bacteria, including the human pathogen Mycobacterium tuberculosis (Mtb), the enzymes mediating several central RNA processing functions are still unknown. Here, we identify the hypothetical Mtb protein Rv2179c as a highly divergent exoribonuclease. Although the primary sequence of Rv2179c has no detectable similarity to any known RNase, the Rv2179c crystal structure reveals an RNase fold. Active site residues are equivalent to those in the DEDD family of RNases, and Rv2179c has close structural homology to Escherichia coli RNase T. Consistent with the DEDD fold, Rv2179c has exoribonuclease activity, cleaving the 3' single-strand overhangs of duplex RNA. Functional orthologs of Rv2179c are prevalent in actinobacteria and found in bacteria as phylogenetically distant as proteobacteria. Thus, Rv2179c is the founding member of a new, large RNase family with hundreds of members across the bacterial kingdom.
核糖核酸酶（RNases）通过 RNA 加工和降解来维持细胞内的 RNA 池。在许多细菌中，包括人类病原体结核分枝杆菌（Mtb），介导几种中心 RNA 加工功能的酶仍然未知。在这里，我们将假定的 Mtb 蛋白 Rv2179c 鉴定为一种高度分化的外切核糖核酸酶。尽管 Rv2179c 的一级序列与任何已知的 RNase 都没有可检测的相似性，但 Rv2179c 的晶体结构揭示了一种 RNase 折叠。活性位点残基与 DEDD 家族的 RNases 相同，并且 Rv2179c 与大肠杆菌 RNase T 具有密切的结构同源性。与 DEDD 折叠一致，Rv2179c 具有外切核糖核酸酶活性，可切割双链 RNA 的 3'单链突出端。Rv2179c 的功能同源物在放线菌中普遍存在，并且在与 Proteobacteria 等远缘细菌中也存在。因此，Rv2179c 是一个新的大型 RNase 家族的创始成员，在整个细菌王国中拥有数百个成员。
