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Structural basis of transposon end recognition explains central features of Tn7 transposition systems
Molecular Cell ( IF 16.0 ) Pub Date : 2022-06-01 , DOI: 10.1016/j.molcel.2022.05.005
Zuzanna Kaczmarska 1 , Mariusz Czarnocki-Cieciura 1 , Karolina M Górecka-Minakowska 1 , Robert J Wingo 2 , Justyna Jackiewicz 1 , Weronika Zajko 1 , Jarosław T Poznański 3 , Michał Rawski 4 , Timothy Grant 5 , Joseph E Peters 2 , Marcin Nowotny 1
Affiliation  

Tn7 is a bacterial transposon with relatives containing element-encoded CRISPR-Cas systems mediating RNA-guided transposon insertion. Here, we present the 2.7 Å cryoelectron microscopy structure of prototypic Tn7 transposase TnsB interacting with the transposon end DNA. When TnsB interacts across repeating binding sites, it adopts a beads-on-a-string architecture, where the DNA-binding and catalytic domains are arranged in a tiled and intertwined fashion. The DNA-binding domains form few base-specific contacts leading to a binding preference that requires multiple weakly conserved sites at the appropriate spacing to achieve DNA sequence specificity. TnsB binding imparts differences in the global structure of the protein-bound DNA ends dictated by the spacing or overlap of binding sites explaining functional differences in the left and right ends of the element. We propose a model of the strand-transfer complex in which the terminal TnsB molecule is rearranged so that its catalytic domain is in a position conducive to transposition.



中文翻译:

转座子末端识别的结构基础解释了 Tn7 转座系统的中心特征

Tn7 是一种细菌转座子,其亲属包含介导 RNA 引导的转座子插入的元素编码的 CRISPR-Cas 系统。在这里,我们展示了原型 Tn7 转座酶 TnsB 与转座子末端 DNA 相互作用的 2.7 Å 低温电子显微镜结构。当 TnsB 跨重复结合位点相互作用时,它采用串珠结构,其中 DNA 结合和催化结构域以平铺和交织的方式排列。DNA 结合结构域形成很少的碱基特异性接触,导致结合偏好,需要以适当间距存在多个弱保守位点,以实现 DNA 序列特异性。TnsB 结合赋予蛋白质结合 DNA 末端的整体结构差异,该差异由结合位点的间距或重叠决定,解释了元件左右末端的功能差异。我们提出了一种链转移复合物模型,其中末端 TnsB 分子重新排列,使其催化结构域处于有利于转座的位置。

更新日期:2022-06-01
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