A transcript (RNA I) from ColE1 inhibits initiation of replication of the plasmid DNA by binding to the precursor of the primer RNA (RNA II). The ability of RNA I to inhibit replication is altered by the presence of a plasmid-specified small protein, Rom. In vitro, RNA I binds to RNA II to form a very unstable complex, C*. Binding of a single molecule of Rom converts C* to a more stable complex, Cm*. Each of these complexes, C* or Cm*, transforms to a more stable complex, C** or Cm**, respectively. While formation of complex C* or Cm* is inferred from the inhibition of binding caused by a second RNA I species, that of complex C** or Cm** is detected by alteration of RNase sensitivity. Complex C* converts to complex Cm* very rapidly upon addition of Rom to the medium and complex Cm* converts to complex C* very rapidly by removal of Rom from the medium. On the other hand, complexes C** and Cm** do not rapidly interconvert, but can eventually transform to the same stable final product. Thus, Rom affects binding of RNA I to RNA II through conversion of a very unstable early intermediate to a more stable complex, creating a second pathway for their stable binding.

译文

:来自ColE1的转录本(RNA I)通过与引物RNA(RNA II)的前体结合,抑制质粒DNA复制的开始。质粒指定的小蛋白质Rom的存在改变了RNA I抑制复制的能力。在体外,RNA I与RNA II结合形成非常不稳定的复合物C *。 Rom单个分子的结合将C *转化为更稳定的复合物Cm *。这些复合物C *或Cm *分别转换为更稳定的复合物C **或Cm **。虽然可以通过抑制第二种RNA I物种的结合来推断复合物C *或Cm *的形成,但可以通过改变RNA酶的敏感性来检测复合物C **或Cm **的形成。在向培养基中添加Rom时,复合物C *非常迅速地转化为复合物Cm *,并且通过从培养基中去除Rom,复合物Cm *非常迅速地转化为复合物C *。另一方面,复合物C **和Cm **不会快速相互转换,但最终可以转换为相同的稳定最终产物。因此,Rom通过将非常不稳定的早期中间体转化为更稳定的复合物,从而影响RNA I与RNA II的结合,从而为它们的稳定结合创造了第二条途径。

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