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) 的前体结合来抑制质粒DNA的复制启动。RNA I抑制复制的能力因质粒指定的小蛋白Rom的存在而改变。在体外,RNA I与RNA II结合形成非常不稳定的复合物C *。单个Rom分子的结合将C * 转化为更稳定的复合物Cm *。这些配合物C * 或Cm * 中的每一个分别转换为更稳定的配合物C ** 或Cm **。虽然从第二种RNA I物种引起的结合抑制推断出复合物C * 或Cm * 的形成,但通过RNase敏感性的改变来检测复合物C ** 或Cm ** 的形成。将Rom添加到介质中时,复杂C * 非常迅速地转换为复杂Cm *,而通过从介质中删除Rom,复杂Cm * 非常迅速地转换为复杂C *。另一方面,络合物C ** 和Cm ** 不会快速互转,但最终可以转化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来影响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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