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首页> 外文OA文献 >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：宽宿主范围质粒RA3分离盒的着丝粒位点位于维持和结合转移模块的边界处†

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摘要

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。该片段规定了编码与IncP-1质粒的中央控制操纵子有关的活性分配系统的korA-incC-korB-orf11操纵子，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对于分离都是必需的。 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均不参与转录自调控。取而代之的是，KorA通过与回文序列结合而施加操纵子的转录控制，回文序列与盒的推定的-35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。与暗盒不连续的区域带有一组不相关的重复基序，分布在约300 bp以上。对该区域的解剖确定了对分割至关重要的着丝粒序列。约300 bp的片段还包括偶联转移的起源oriT，以及驱动偶联转移操纵子转录的启动子。 PromA组环境质粒中有一组相似的顺式作用基序，这突显了这些质粒和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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