Institute for Integrative Biology of the Cell (I2BC), Université Paris Saclay, CEA, CNRS, Université Paris Sud, 1 avenue de la Terrasse, 91198 Gif sur Yvette, France.
Microbiol Spectr. 2014 Dec;2(6). doi: 10.1128/microbiolspec.MDNA3-0056-2014.
Two related tyrosine recombinases, XerC and XerD, are encoded in the genome of most bacteria where they serve to resolve dimers of circular chromosomes by the addition of a crossover at a specific site, dif. From a structural and biochemical point of view they belong to the Cre resolvase family of tyrosine recombinases. Correspondingly, they are exploited for the resolution of multimers of numerous plasmids. In addition, they are exploited by mobile DNA elements to integrate into the genome of their host. Exploitation of Xer is likely to be advantageous to mobile elements because the conservation of the Xer recombinases and of the sequence of their chromosomal target should permit a quite easy extension of their host range. However, it requires means to overcome the cellular mechanisms that normally restrict recombination to dif sites harbored by a chromosome dimer and, in the case of integrative mobile elements, to convert dedicated tyrosine resolvases into integrases.
两种相关的酪氨酸重组酶 XerC 和 XerD 编码在大多数细菌的基因组中，它们通过在特定位点添加交叉来解决环状染色体的二聚体，即 dif。从结构和生化角度来看，它们属于 Cre 解旋酶家族的酪氨酸重组酶。相应地，它们被用于解决许多质粒的多聚体。此外，它们被移动 DNA 元件利用来整合到宿主的基因组中。Xer 的利用可能对移动元件有利，因为 Xer 重组酶及其染色体靶序列的保守性应该允许它们的宿主范围相当容易地扩展。然而，这需要克服通常将重组限制在染色体二聚体所携带的 dif 位点的细胞机制，并且在整合性移动元件的情况下，需要将专用的酪氨酸解旋酶转化为整合酶。
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