Kiss János, Szabó Mónika, Hegyi Anna, Douard Gregory, Praud Karine, Nagy István, Olasz Ferenc, Cloeckaert Axel, Doublet Benoît
National Agricultural Research and Innovation Centre, Agricultural Biotechnology Institute, Gödöllõ, Hungary.
ISP, Institut National de la Recherche Agronomique, Université de Tours, UMR 1282, Nouzilly, France.
Front Microbiol. 2019 Mar 6;10:457. doi: 10.3389/fmicb.2019.00457. eCollection 2019.
The integrative mobilizable elements of SGI1-family considerably contribute to the spread of resistance to critically important antibiotics among enteric bacteria. Even though many aspects of SGI1 mobilization by IncA and IncC plasmids have been explored, the basic transfer elements such as and self-encoded mobilization proteins remain undiscovered. Here we describe the mobilization region of SGI1 that is well conserved throughout the family and carries the and two genes, and (originally annotated as S020 and S019, respectively) that are essential for the conjugative transfer of SGI1. , which is located in the vicinity of the two mobilization genes proved to be a 125-bp GC-rich sequence with several important inverted repeat motifs. The mobilization proteins MpsA and MpsB are expressed from a bicistronic mRNA, although MpsB can be produced from its own mRNA as well. The protein structure predictions imply that MpsA belongs to the lambda tyrosine recombinase family, while MpsB resembles the N-terminal core DNA binding domains of these enzymes. The results suggest that MpsA may act as an atypical relaxase, which needs MpsB for SGI1 transfer. Although the helper plasmid-encoded relaxase proved not to be essential for SGI1 transfer, it appeared to be important to achieve the high transfer rate of the island observed with the IncA/IncC-SGI1 system.
SGI1家族的整合可移动元件在肠道细菌中对极其重要的抗生素耐药性传播起到了相当大的作用。尽管已经对IncA和IncC质粒介导的SGI1移动的许多方面进行了探索，但诸如 以及自我编码的移动蛋白等基本转移元件仍未被发现。在此，我们描述了SGI1的移动区域，该区域在整个家族中高度保守，并携带了 和两个基因，即 和 （最初分别注释为S020和S019），它们对于SGI1的接合转移至关重要。 位于两个移动基因附近，被证明是一个富含GC的125碱基对序列，具有几个重要的反向重复基序。移动蛋白MpsA和MpsB由一个双顺反子mRNA表达，不过MpsB也可以从其自身的mRNA产生。蛋白质结构预测表明，MpsA属于λ酪氨酸重组酶家族，而MpsB类似于这些酶的N端核心DNA结合结构域。结果表明，MpsA可能作为一种非典型松弛酶，其SGI1转移需要MpsB。尽管辅助质粒编码的松弛酶被证明对SGI1转移不是必需的，但它对于实现IncA/IncC-SGI1系统所观察到的该岛的高转移率似乎很重要。
