Kostrewa Dirk, Kuhn Claus-D, Engel Christoph, Cramer Patrick
Gene Center Munich and Department of Biochemistry, Ludwig-Maximilians-Universität München, Feodor-Lynen-Strasse 25, 81377 Munich, Germany.
Elite Network of Bavaria, BIOmac Research Center, University of Bayreuth, 95440 Bayreuth, Germany.
Acta Crystallogr D Biol Crystallogr. 2015 Sep;71(Pt 9):1850-5. doi: 10.1107/S1399004715012651. Epub 2015 Aug 25.
RNA polymerase I (Pol I) is the central, 14-subunit enzyme that synthesizes the ribosomal RNA (rRNA) precursor in eukaryotic cells. The recent crystal structure of Pol I at 2.8 Å resolution revealed two novel elements: the expander' in the active-centre cleft and the connector' that mediates Pol I dimerization [Engel et al. (2013), Nature (London), 502, 650-655]. Here, a Pol I structure in an alternative crystal form that was solved by molecular replacement using the original atomic Pol I structure is reported. The resulting alternative structure lacks the expander but still shows an expanded active-centre cleft. The neighbouring Pol I monomers form a homodimer with a relative orientation distinct from that observed previously, establishing the connector as a hinge between Pol I monomers.
RNA聚合酶I（Pol I）是一种核心的、由14个亚基组成的酶，它在真核细胞中合成核糖体RNA（rRNA）前体。最近解析出的分辨率为2.8 Å的Pol I晶体结构揭示了两个新元件：活性中心裂隙中的“扩展器”和介导Pol I二聚化的“连接器”[恩格尔等人（2013年），《自然》（伦敦），502, 650 - 655]。在此，报道了一种通过使用原始原子Pol I结构进行分子置换解析得到的另一种晶体形式的Pol I结构。所得的替代结构缺少扩展器，但仍显示出一个扩展的活性中心裂隙。相邻的Pol I单体形成一个同型二聚体，其相对取向与之前观察到的不同，从而确定连接器为Pol I单体之间的铰链。
