Lorentzen Esben, Basquin Jerome, Tomecki Rafal, Dziembowski Andrzej, Conti Elena
European Molecular Biology Laboratory, Meyerhofstrasse 1, D-69117 Heidelberg, Germany.
Mol Cell. 2008 Mar 28;29(6):717-28. doi: 10.1016/j.molcel.2008.02.018.
The eukaryotic exosome is a macromolecular complex essential for RNA processing and decay. It has recently been shown that the RNase activity of the yeast exosome core can be mapped to a single subunit, Rrp44, which processively degrades single-stranded RNAs as well as RNAs containing secondary structures. Here we present the 2.3 A resolution crystal structure of S. cerevisiae Rrp44 in complex with single-stranded RNA. Although Rrp44 has a linear domain organization similar to bacterial RNase II, in three dimensions the domains have a different arrangement. The three domains of the classical nucleic-acid-binding OB fold are positioned on the catalytic domain such that the RNA-binding path observed in RNase II is occluded. Instead, RNA is threaded to the catalytic site via an alternative route suggesting a mechanism for RNA-duplex unwinding. The structure provides a molecular rationale for the observed biochemical properties of the RNase R family of nucleases.
真核外切体是一种对RNA加工和降解至关重要的大分子复合物。最近有研究表明，酵母外切体核心的核糖核酸酶活性可定位到单个亚基Rrp44上，该亚基可连续降解单链RNA以及含有二级结构的RNA。在此，我们展示了酿酒酵母Rrp44与单链RNA复合物的2.3埃分辨率晶体结构。尽管Rrp44具有与细菌核糖核酸酶II相似的线性结构域组织，但在三维空间中，这些结构域的排列方式不同。经典核酸结合OB折叠的三个结构域位于催化结构域上，使得在核糖核酸酶II中观察到的RNA结合路径被阻断。相反，RNA通过另一条途径进入催化位点，这提示了一种RNA双链解旋的机制。该结构为核糖核酸酶R家族核酸酶所观察到的生化特性提供了分子理论依据。
