CNRS UPR 9073 (affiliated with Université Paris Diderot, Sorbonne Paris Cité), Institut de Biologie Physico-Chimique, 13 rue Pierre et Marie Curie, 75005 Paris, France.
Structure. 2012 Oct 10;20(10):1769-77. doi: 10.1016/j.str.2012.08.002. Epub 2012 Aug 30.
Ribonuclease (RNase) Z is involved in the maturation of the 3' ends of transfer RNAs (tRNAs) in all three kingdoms of life. To prevent futile cycles of CCA addition and removal, eukaryotic RNase Z discriminates against mature tRNAs bearing a CCA motif, with the first cytosine residue (C74) being the key antideterminant. Here, we show that, remarkably, the B. subtilis enzyme does not discriminate against cytosine in position 74, but rather is highly stimulated by uracil in this location. Consistent with this observation, the vast majority of B. subtilis tRNA precursor substrates of RNase Z naturally contain U74. Those tRNA precursors with a uracil further downstream are also substrates for RNase Z, but are matured in a two-step endo/exonuclease reaction. We solved the first crystal structure of B. subtilis RNase Z bound to a tRNA(Thr) precursor with U74 and show that the enzyme has a specific binding pocket for this nucleotide.
核糖核酸酶 Z 参与所有三个生命领域的转移 RNA（tRNA）3'端的成熟。为了防止 CCA 添加和去除的无效循环，真核生物 RNase Z 区分带有 CCA 基序的成熟 tRNA，其中第一个胞嘧啶残基（C74）是关键的反决定因素。在这里，我们表明，令人惊讶的是，枯草芽孢杆菌酶不会区分位置 74 处的胞嘧啶，而是在此位置受到尿嘧啶的高度刺激。与这一观察结果一致的是，枯草芽孢杆菌 RNase Z 的绝大多数 tRNA 前体底物天然含有 U74。那些在下游还有尿嘧啶的 tRNA 前体也是 RNase Z 的底物，但通过内切/外切核酸酶反应两步成熟。我们解决了第一个枯草芽孢杆菌 RNase Z 与 U74 的 tRNA（Thr）前体结合的晶体结构，并表明该酶具有该核苷酸的特定结合口袋。
