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首页> 外文期刊>Plasmid: An International Journal Devoted to Extrachromosomal Gene Systems >Conservation of the genetic switch between replication and transfer genes of IncP plasmids but divergence of the replication functions which are major host-range determinants.
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Conservation of the genetic switch between replication and transfer genes of IncP plasmids but divergence of the replication functions which are major host-range determinants.

机译：IncP质粒的复制和转移基因之间的遗传切换得以保留，但复制功能的差异是主要的宿主范围决定因素。

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The trfA operon of broad-host-range IncP plasmids is essential to activate the origin of vegetative replication in diverse species. The trb operon encodes most of the apparatus for mating pair formation, the first step in conjugative transfer. Comparison of the nucleotide sequence of the IncP beta plasmid R751 presented here with the equivalent IncP alpha sequence identifies conserved features of the organization and regulation of the trfA operon and the region controlling expression of the trb operon. As in IncP alpha plasmids, these operons are transcribed from a bidirectional promoter region consisting of trfAp for the trfA operon and trbAp and trbBp for the trb operon. The KorA-dependent switch between the trfA and trbA promoters is conserved as is the trbA gene encoding the third IncP global regulator. The intergenic region between trbA and trbB shows very little sequence identity between the two plasmids but the spacing, the KorB operator, the trbB promoter, and the existence of a hairpin loop (albeit of different actual sequence) which sequesters the trbB ribosome binding site are all conserved. The trfA operon encodes two ORFs. The first ORF is highly conserved and encodes a putative single-stranded DNA binding protein (Ssb). The second, trfA, contains two translational starts as in the IncP alpha plasmids, generating related polypeptides of 406 (TrfA1) and 282 (TrfA2) amino acids. TrfA2 is very similar to the IncP alpha product, whereas the N-terminal region of TrfA1 shows very little similarity to the equivalent region of IncP alpha TrfA1. This region has been implicated in the ability of IncP alpha plasmids to replicate efficiently in Pseudomonas aeruginosa. A TcR derivative of R751 was constructed and shown not to establish itself efficiently in P. aeruginosa at 37 degrees C, although it did establish itself inefficiently at lower temperatures, underlining the importance of this region in the adaptation of the plasmid to the host.
机译：广泛宿主范围的IncP质粒的trfA操纵子对于激活各种物种中的营养复制起点至关重要。 trb操纵子编码大多数用于配对形成的设备，这是共轭转移的第一步。此处介绍的IncPβ质粒R751的核苷酸序列与等效的IncPα序列的比较确定了trfA操纵子的组织和调控以及控制trb操纵子表达的区域的保守特征。如在IncPα质粒中一样，这些操纵子从双向启动子区域转录而成，该双向启动子区域由trfAp（对于trfA操纵子）和trbAp（对于trb操纵子）的trbBp组成。 trfA和trbA启动子之间的KorA依赖性开关与编码第三个IncP全局调节子的trbA基因一样，均被保守。 trbA和trbB之间的基因间区域显示两个质粒之间的序列同一性很小，但是间隔，KorB操纵子，trbB启动子和存在发夹环（尽管实际序列不同）可以隔离trbB核糖体结合位点。全部保守。 trfA操纵子编码两个ORF。第一个ORF是高度保守的，并编码一个推定的单链DNA结合蛋白（Ssb）。第二个是trfA，与IncP alpha质粒中的一样，包含两个翻译起点，产生了406个（TrfA1）和282个（TrfA2）氨基酸的相关多肽。 TrfA2与IncP alpha产品非常相似，而TrfA1的N端区域与IncP alpha TrfA1的等效区域几乎没有相似性。该区域与IncPα质粒在铜绿假单胞菌中有效复制的能力有关。构建了R751的TcR衍生物，尽管在较低的温度下它并不能有效地建立其自身，但它并未在37℃的铜绿假单胞菌中有效地建立其自身，这突显了该区域在质粒对宿主的适应中的重要性。

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