酵母的Shu蛋白复合物，是由Shu1、Shu2、Psy3和Csm2几种蛋白组成，它通过偶联复制后修复与同源重组，维持了基因组的稳定性。
然而，由于缺乏对Shu蛋白的生化及结构信息，它们在该通路中精确的作用还不明确。近日，中国科学技术大学滕脉坤课题组解析了Psy3-Csm2复合体在1.9 埃分辨率的晶体结构。
晶体结构表明，Psy3与Csm2主要通过一个疏水核心形成了一个异二聚体。出乎预料的是，Psy3和Csm2都有一个相似的非常类似于Rad51的ATPase核心结构域。
Psy3和Csm2的L2环与Rad51的结构非常类似，它赋予了Shu复合体DNA结合活性。与Rad51一样，Shu复合体似乎通过非特异性的结合到DNA上，形成了一个核蛋白纤丝 。
基于结构突变研究表明了Shu复合体的DNA结合活性，而且这对修复甲磺酸甲酯引起的DNA损伤是必须的。该发现对研究Shu复合体介导的Srs2的调节奠定了很好的基础。相关论文发表在3月30日的The journal of Biological Chemistry。
滕脉坤教授是中国科学技术大学生命科学学院党总支书记兼副院长。多年从事生物大分子晶体学和结构生物学研究，曾从事DNA寡聚核苷酸及其DNA-药物复合物的晶体学；病毒晶体学；T-细胞受体及其复合物的晶体学；葡萄糖异构酶蛋白质工程等研究工作。目前主要进行真核生物转录调控、基因损伤修复、囊泡形成相关蛋白质及其复合物的结构与功能关系研究，同时关注天然蛇毒毒素蛋白对各类离子通道的调控机理研究。（生物谷Deepblue编译）
doi: 10.1074/jbc.M111.334698
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Structural analysis of Shu proteins reveals a DNA-binding role essential for resisting damage
Yuyong Tao, Xu Li, Yiwei Liu, Jianbin Ruan, Shali Qi, Liwen Niu and Maikun Teng.
The yeast Shu complex, consisting of the proteins Shu1, Shu2, Psy3 and Csm2, maintains genomic stability by coupling post-replication repair to homologous recombination.However, a lack of biochemical and structural information on the Shu proteins precludes revealing their precise roles within the pathway. Here we report the 1.9 A crystal structure of the Psy3-Csm2 complex.The crystal structure shows that Psy3 forms a heterodimer with Csm2 mainly through a hydrophobic core. Unexpectedly, Psy3 and Csm2 share a similar architecture which closely resembles the ATPase core domain of Rad51.The L2 loop present in Psy3 and Csm2 is similar to that of Rad51, and confers the DNA-binding activity of the Shu complex. As with Rad51, the Shu complex appears to form a nucleoprotein filament by binding non-specifically to DNA.Structure-based mutagenesis studies have demonstrated that the DNA-binding activity of the Shu complex is essential for repair of the methyl methanesulfonate-induced DNA damage. Our findings provide good foundations for the understanding of the Srs2 regulation by the Shu complex.
