Crystal structures of the BsPif1 helicase reveal that a major movement of the 2B SH3 domain is required for DNA unwinding.
Crystal structures of the BsPif1 helicase reveal that a major movement of the 2B SH3 domain is required for DNA unwinding.
复制标题
BsPif1 解旋酶的晶体结构揭示 DNA 解旋需要 2B SH3 结构域的主要运动
DOI：
10.1093/nar/gkw033
复制
发表时间：
2016-04-07
影响因子：
14.9
通讯作者：
Xi XG
中科院分区：
文献类型：
--
作者：
Chen WF;Dai YX;Duan XL;Liu NN;Shi W;Li N;Li M;Dou SX;Dong YH;Rety S;Xi XG
Pif 1解旋酶是SF 1B家族中普遍存在的成员，对维持基因组稳定性至关重要。有人推测，Pif 1特异性的基序可能折叠在特定的结构，赋予不同的activityupon it. Here，我们报告的晶体结构的Pif 1解旋酶从拟杆菌属有和没有三磷酸腺苷（ATP）类似物/ssDNA。BsPif 1与RecD 2和Dda解旋酶具有结构相似性，但在1B和2B结构域中具有特定特征。高度保守的Pif 1家族特异性序列基序以精确的构象与结构域1B中假定的pin环相互作用并限制该pin环。更重要的是，我们发现含有特定延伸发夹的2B结构域在ATP和DNA结合时经历显著的旋转和/或运动，这是DNA解旋所必需的。因此，我们提出了一种机制，其中2B结构域发挥主导作用的DNA解旋。构象变化调节Pif 1活性的事实可能为以下令人困惑的观察提供见解：Pif 1在与Polδ相关的断裂诱导复制期间变得高度进行性，而分离的Pif 1具有低的进行性。
Pif1 helicases are ubiquitous members of the SF1B family and are essential for maintaining genome stability. It was speculated that Pif1-specific motifs may fold in specific structures, conferring distinct activities upon it. Here, we report the crystal structures of the Pif1 helicase from Bacteroides spp with and without adenosine triphosphate (ATP) analog/ssDNA. BsPif1 shares structural similarities with RecD2 and Dda helicases but has specific features in the 1B and 2B domains. The highly conserved Pif1 family specific sequence motif interacts with and constraints a putative pin-loop in domain 1B in a precise conformation. More importantly, we found that the 2B domain which contains a specific extended hairpin undergoes a significant rotation and/or movement upon ATP and DNA binding, which is absolutely required for DNA unwinding. We therefore propose a mechanism for DNA unwinding in which the 2B domain plays a predominant role. The fact that the conformational change regulates Pif1 activity may provide insight into the puzzling observation that Pif1 becomes highly processive during break-induced replication in association with Polδ, while the isolated Pif1 has low processivity.