An asymmetric SMC-kleisin bridge in prokaryotic condensin
An asymmetric SMC-kleisin bridge in prokaryotic condensin
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DOI：
10.1038/nsmb.2488
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发表时间：
2013-03-01
影响因子：
16.8
通讯作者：
Gruber, Stephan
中科院分区：
文献类型：
--
作者：
Buermann, Frank;Shin, Ho-Chul;Gruber, Stephan
真核染色体结构维持 (SMC)-kleisin 复合物形成大型环形组件，促进染色体精确分离。它们的不对称结构核心包含与 kleisin 亚基两端相连的 SMC 异二聚体。然而，原核凝聚蛋白Smc-ScpAB是由与kleisin ScpA以假定的对称方式相关的对称Smc同二聚体组成的。在这里，我们证明 Smc 分子具有两个不同的 ScpA 结合位点。 ScpA 的 N 末端结合 Smc 卷曲螺旋，而 C 末端结合 Smc ATPase 结构域。我们发现，在芽孢杆菌亚填充细胞中，Smc 二聚体由单个 ScpAB 桥接，生成类似于真核 SMC 复合物的不对称三联环。我们定义了一种确保不对称组装的分子机制，并得出结论：SMC-kleisin 环的基本结构在真核生物出现之前就已进化。
Eukaryotic structural maintenance of chromosomes (SMC)-kleisin complexes form large, ring-shaped assemblies that promote accurate chromosome segregation. Their asymmetric structural core comprises SMC heterodimers that associate with both ends of a kleisin subunit. However, prokaryotic condensin Smc-ScpAB is composed of symmetric Smc homodimers associated with the kleisin ScpA in a postulated symmetrical manner. Here, we demonstrate that Smc molecules have two distinct binding sites for ScpA. The N terminus of ScpA binds the Smc coiled coil, whereas the C terminus binds the Smc ATPase domain. We show that in Bacillus sub fills cells, an Smc dimer is bridged by a single ScpAB to generate asymmetric tripartite rings analogous to eukaryotic SMC complexes. We define a molecular mechanism that ensures asymmetric assembly, and we conclude that the basic architecture of SMC-kleisin rings evolved before the emergence of eukaryotes.