首页> 美国卫生研究院文献>The EMBO Journal >Point mutations change the thermal denaturation profile of a short DNA fragment containing the lactose control elements. Comparison between experiment and theory.
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Point mutations change the thermal denaturation profile of a short DNA fragment containing the lactose control elements. Comparison between experiment and theory.

机译:点突变改变了包含乳糖控制元件的短DNA片段的热变性特性。实验与理论之间的比较。

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摘要

To understand the denaturation process of short DNA segments we have chosen a 203-base pair (bp) restriction fragment containing the lactose control region. A steady decrease in GC content exists between its i proximal and z proximal ends. We confirm that this fragment melts at low salt in two subtransitions. A GC to AT mutation in the AT-rich region (mutation UV5) increases the number of denatured base pairs in the first subtransition and decreases the cooperativity of the melting process. A GC to AT mutation in the GC-rich region (mutation L8) decreases the number of denatured base pairs in the first subtransition and increases the cooperativity. These mutations induce the same shift in the temperature of half denaturation. The effects of both mutations are additive. A short deletion at the z end of the fragment affects only the first subtransition. When four GC pairs are added to both end, the fragment melts in one transition. Comparison with the results obtained with a larger 789-bp lac fragment reveals strong end effects on base pair stability and suggests that denaturation of the 203-bp fragment proceeds unidirectionally from the z end. Good agreement is shown with the predictions made with the "z ipper model" of Crothers et al. (1965).
机译:为了了解短DNA片段的变性过程,我们选择了一个包含乳糖控制区的203个碱基对(bp)的限制性片段。 GC含量在其i近端和z近端之间稳步下降。我们确认该片段在两个亚过渡中以低盐解链。在富含AT的区域中发生GC到AT突变(突变UV5)会增加第一个子过渡中变性碱基对的数量,并降低解链过程的协同性。 GC富集区域中的GC到AT突变(突变L8)减少了第一个子过渡中变性碱基对的数量,并提高了协同作用。这些突变引起半变性温度的相同变化。两种突变的作用是累加的。片段z端的短删除仅影响第一个子转换。当在两端添加四个GC对时,片段会在一个过渡中融化。与使用较大的789-bp lac片段获得的结果进行比较,发现对碱基对稳定性有很强的末端效应,并表明203-bp片段的变性是从z端单向进行的。用Crothers等人的“拉链模型”所做的预测显示出很好的一致性。 (1965)。

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