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首页> 外文期刊>Applied and Environmental Microbiology >The Centromere Site of the Segregation Cassette of Broad-Host-Range Plasmid RA3 Is Located at the Border of the Maintenance and Conjugative Transfer Modules
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The Centromere Site of the Segregation Cassette of Broad-Host-Range Plasmid RA3 Is Located at the Border of the Maintenance and Conjugative Transfer Modules

机译：广泛宿主范围的质粒RA3分离盒的着丝粒位点位于维护和共轭转移模块的边界。

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RA3 is a low-copy-number, broad-host-range (BHR) conjugative plasmid of the IncU incompatibility group isolated originally from Aeromonas spp. A 4.9-kb fragment of RA3 is sufficient to stabilize an otherwise unstable replicon in Escherichia coli. This fragment specifies the korA-incC-korB-orf11 operon coding for an active partition system related to the central control operon of IncP-1 plasmids and found also in BHR environmental plasmids recently classified as the PromA group. All four genes in the cassette are necessary for segregation. IncC and KorB of RA3 belong to the ParA and ParB families of partitioning proteins, respectively. In contrast with IncP-1 plasmids, neither KorB nor IncC are involved in transcriptional autoregulation. Instead, KorA exerts transcriptional control of the operon by binding to a palindromic sequence that overlaps the putative ?35 promoter motif of the cassette. The Orf11 protein is not required for regulation, but its absence decreases the stabilization potential of the segregation module. A region discontiguous from the cassette harbors a set of unrelated repeat motifs distributed over ～300 bp. Dissection of this region identified the centromere sequence that is vital for partitioning. The ～300-bp fragment also encompasses the origin of conjugative transfer, oriT, and the promoter that drives transcription of the conjugative transfer operon. A similar set of cis-acting motifs are evident in the PromA group of environmental plasmids, highlighting a common evolutionary origin of segregation and conjugative transfer modules in these plasmids and members of the IncU group.
机译：RA3是最初从 Aeromonas spp中分离的IncU不相容性组的低拷贝数，宽宿主范围（BHR）结合质粒。 RA3的4.9kb片段足以稳定大肠杆菌中原本不稳定的复制子。该片段指定了 korA-incC-korB-orf11 操纵子，该操纵子编码与IncP-1质粒的中央控制操纵子有关的活性分配系统，并且还在最近归类为PromA组的BHR环境质粒中发现。盒中的所有四个基因都是分离所必需的。 RA3的IncC和KorB分别属于分配蛋白的ParA和ParB家族。与IncP-1质粒相反，KorB和IncC都不参与转录自调控。取而代之的是，KorA通过与回文序列结合而对操纵子进行转录控制，回文序列与盒的假定的β35启动子基序重叠。 Orf11蛋白不是调节所必需的，但是它的缺失会降低分离模块的稳定潜力。与盒带不相邻的区域带有一组不相关的重复基序，分布在〜300 bp左右。对该区域的解剖确定了对分区至关重要的着丝粒序列。 〜300 bp的片段还包括共轭转移的起源， oriT ，以及驱动共轭转移操纵子转录的启动子。 PromA组环境质粒中有一组相似的 cis 作用基序，突显了这些质粒和IncU组成员中分离和共轭转移模块的共同进化起源。

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