THE PARDE OPERON OF THE BROAD-HOST-RANGE PLASMID RK2 SPECIFIES GROWTH-INHIBITION ASSOCIATED WITH PLASMID LOSS
THE PARDE OPERON OF THE BROAD-HOST-RANGE PLASMID RK2 SPECIFIES GROWTH-INHIBITION ASSOCIATED WITH PLASMID LOSS
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DOI：
10.1006/jmbi.1994.1207
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发表时间：
1994-03-18
影响因子：
5.6
通讯作者：
HELINSKI, DR
中科院分区：
文献类型：
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作者：
ROBERTS, RC;STROM, AR;HELINSKI, DR
最近，广宿主质粒RK2的0.8kb区域已被证明在某些但不是所有的生长条件下足以以非载体、宽宿主范围的方式稳定质粒(Roberts，R.C.&Helinski，D.R.(1992).J.Bacteriol.174,8119-8132)。这一区域包含parDE操纵子，它编码小蛋白pard和pare，这两种蛋白都是质粒稳定所必需的。本文证明了0.8kb区域编码了抑制大肠杆菌细胞生长的能力，这可能是那些丢失了携带该稳定区域的质粒的细菌的能力，这种抑制似乎与细胞杀伤和细菌细胞丝状化有关。在特定的培养条件下，野生型和突变的0.8kb区在促进温度敏感型RK2复制子质粒的稳定维持和抑制细菌细胞分裂的能力之间存在很好的相关性。野生型和突变型0.8kb区域的特性进一步表明，PARE蛋白是抑制生长的原因，PARD蛋白中和了PARE蛋白的毒力。这与parDgenin的存在破坏了温度敏感的RK2复制子携带0.8kb功能性区域副本的发现是一致的。这种不稳定似乎是PARD蛋白介导的抑制生长抑制的结果，从而允许失去温度敏感质粒的细胞存活。这些观察结果表明，RK2的0.8kb序列编码了一种生长抑制功能，这可能在质粒的稳定中发挥作用。
Recently, a 0·8 kb region of the broad-host-range plasmid RK2 has been shown to be sufficient to stabilize plasmids in a vector-independent, broad-host-range manner under some but not all growth conditions (Roberts, R. C. & Helinski, D. R.(1992).J. Bacteriol.174, 8119-8132). This region encompasses theparDEoperon, which encodes the small proteins ParD and ParE, both of which are required for the plasmid stabilization. This paper demonstrates that the 0·8 kb region encodes the capacity to inhibit cell growth ofEscherichia coli, presumably of those bacteria that have lost plasmids carrying this stabilization region, and this inhibition appears to be associated with cell killing and bacterial cell filamentation. A good correlation was observed between the capacity of wild-type and mutated 0·8 kb regions to promote stable maintenance of a temperature-sensitive RK2 replicon plasmid and to inhibit bacterial cell division under specified medium conditions. The properties of the wild-type and mutant 0·8 kb region further indicate that the ParE protein is responsible for the growth inhibition and the ParD protein neutralizes the toxic activity of the ParE protein. This is consistent with the finding that the presence of theparDgenein transdestabilizes a temperature-sensitive RK2 replicon carrying a copy of the functional 0·8 kb region. This destabilization appears to be the result of ParD protein-mediated suppression of growth inhibition, thus allowing survival of cells that have lost the temperature-sensitive plasmid. These observations indicate that the 0·8 kb sequence of RK2 encodes a growth inhibition function that is likely to play a role in the plasmid stabilization.