The site‐specific recombinase Tn3 resolvase initiates DNA strand exchange when two res recombination sites and six resolvase dimers interact to form a synapse. The detailed architecture of this intricate recombination machine remains unclear. We have clarified which of the potential dimer–dimer interactions are required for synapsis and recombination, using a novel complementation strategy that exploits a previously uncharacterized resolvase from Bartonella bacilliformis (“Bart”). Tn3 and Bart resolvases recognize different DNA motifs, via diverged C‐terminal domains (CTDs). They also differ substantially at N‐terminal domain (NTD) surfaces involved in dimerization and synapse assembly. We designed NTD‐CTD hybrid proteins, and hybrid res sites containing both Tn3 and Bart dimer binding sites. Using these components in in vivo assays, we demonstrate that productive synapsis requires a specific “R” interface involving resolvase NTDs at all three dimer‐binding sites in res. Synapses containing mixtures of wild‐type Tn3 and Bart resolvase NTD dimers are recombination‐defective, but activity can be restored by replacing patches of Tn3 resolvase R interface residues with Bart residues, or vice versa. We conclude that the Tn3/Bart family synapse is assembled exclusively by R interactions between resolvase dimers, except for the one special dimer–dimer interaction required for catalysis.

中文翻译：

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组装 Tn3 解析突触所需的蛋白质-蛋白质相互作用

当两个res重组位点和六个解析酶二聚体相互作用形成突触时，位点特异性重组酶 Tn 3解析酶启动 DNA 链交换。这种复杂的重组机器的详细架构仍不清楚。我们已经阐明了突触和重组需要哪些潜在的二聚体-二聚体相互作用，使用一种新的互补策略，该策略利用了以前未表征的杆状巴尔通体（“Bart”）分解酶。TN 3Bart 分解酶通过不同的 C 端结构域 (CTD) 识别不同的 DNA 基序。它们在涉及二聚化和突触组装的 N 端结构域 (NTD) 表面也有很大不同。我们设计了 NTD-CTD 杂合蛋白，以及包含 Tn 3和 Bart 二聚体结合位点的杂合res位点。在体内试验使用这些组件，我们证明了生产联会需要一个特定的“ [R ”界面在所有三个二聚体结合位点解离涉及NTDs的资源。含有野生型 Tn 3和 Bart 分解酶 NTD 二聚体混合物的突触存在重组缺陷，但可以通过更换 Tn 3分解酶R 的补丁来恢复活性Bart 残基的界面残基，反之亦然。我们得出结论，除了催化所需的一种特殊的二聚体-二聚体相互作用外，Tn 3 /Bart 家族突触完全由分解酶二聚体之间的R相互作用组装而成。