Structure of the cooperative Xis-DNA complex reveals a micronucleoprotein filament that regulates phage lambda intasome assembly
Structure of the cooperative Xis-DNA complex reveals a micronucleoprotein filament that regulates phage lambda intasome assembly
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DOI：
10.1073/pnas.0607820104
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发表时间：
2007-02-13
影响因子：
11.1
通讯作者：
Clubb, Robert T.
中科院分区：
文献类型：
--
作者：
Abbani, Mohamad A.;Papagiannis, Christie V.;Clubb, Robert T.
DNA结构蛋白Xis调节高阶核蛋白整合体的构建，该整合体整合并切除来自大肠杆菌染色体的λ噬菌体基因组。Xis通过刺激噬菌体切除10（6）倍来调节位点特异性重组的方向性，同时抑制噬菌体重组。控制是通过协同组装到大约35-bp的DNA调节元件上来实现的，它会扭曲该元件以优先稳定切除的整合体。在这里，我们报告的2.6埃晶体结构的三个合作绑定Xis蛋白和33 bp的DNA含有调控元件之间的复合物。Xis以头对尾的方向结合DNA以产生微核蛋白丝。虽然每个原聚体通过一组相似的非碱基特异性接触锚定到双链体上，但可延展的蛋白质-DNA相互作用使其能够结合到核粒序列不同的位点上。双链体序列末端的蛋白质特异性识别相似的结合位点，并通过蛋白质-蛋白质相互作用与以较低特异性方式结合的桥接Xis原聚体参与协同结合。这种聚合物的形成将大约72度的曲率引入到DNA中，并具有轻微的正扭曲，其功能是连接切除的整合体内由整合酶桥接的DNA的不同片段。
The DNA architectural protein Xis regulates the construction of higher-order nucleoprotein intasomes that integrate and excise the genome of phage lambda from the Escherichia coli chromosome. Xis modulates the directionality of site-specific recombination by stimulating phage excision 10(6)-fold, while simultaneously inhibiting phage reintegration. Control is exerted by cooperatively assembling onto a approximate to 35-bp DNA regulatory element, which it distorts to preferentially stabilize an excisive intasome. Here, we report the 2.6-angstrom crystal structure of the complex between three cooperatively bound Xis proteins and a 33-bp DNA containing the regulatory element. Xis binds DNA in a head-to-tail orientation to generate a micronucleoprotein filament. Although each protomer is anchored to the duplex by a similar set of nonbase specific contacts, malleable protein-DNA interactions enable binding to sites that differ in nucleoticle sequence. Proteins at the ends of the duplex sequence specifically recognize similar binding sites and participate in cooperative binding via protein-protein interactions with a bridging Xis protomer that is bound in a less specific manner. Formation of this polymer introduces approximate to 72 degrees of curvature into the DNA with slight positive writhe, which functions to connect disparate segments of DNA bridged by integrase within the excisive intasome.