Conformational variability of poly(dA-dT).poly(dA-dT) and some other deoxyribonucleic acids includes a novel type of double helix.
Conformational variability of poly(dA-dT).poly(dA-dT) and some other deoxyribonucleic acids includes a novel type of double helix.
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聚(dA-dT).聚(dA-dT)和一些其他脱氧核糖核酸的构象变异包括新型双螺旋。
DOI：
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发表时间：
1985
影响因子：
4.4
通讯作者：
J. Kypr
中科院分区：
文献类型：
--
作者：
M. Vorlíčková;J. Kypr
本文综述了poly（dA-dT）.poly（dA-dT）在溶液中能呈现三种不同的双螺旋结构，其中只有A型符合经典概念。其他两种结构具有作为双螺旋重复的二核苷酸。在低盐浓度下，poly（dA-dT）呈现异常多变的B型交替构象。它的结构可以逐渐移动到由具有反转的长波长CD带的CD谱和具有非常低的两个共振的0.6ppm分离的31 P NMR谱所划分的极限中。与Z-DNA相反，poly（dA-dT）.poly（dA-dT）的极限交替B构象的31 P NMR谱的特征在于一个共振的高场位移。我们将交替B构象的特殊构象灵活性归因于dA-dT和dT-dA步骤中碱基堆叠的不平等趋势。然而，通过假设有限的交替B构象，合成DNA的可变性并没有被耗尽。特异性试剂通过快速的双态机制使其异构化为另一种构象，这反映在负长波长CD带的进一步加深和poly（dA-dT）的31 P NMR共振的低场位移，poly（dA-dT）在交替的B构象逐渐改变的过程中是恒定的。然而，这些变化与poly（dG-dC）在B-Z异构化过程中的行为方式有质的不同。Poly（dG-dC）.poly（dG-dC）在特征低场位置显示嘌呤-嘧啶（dGpdC）共振，而poly（dA-dT）.poly（dA-dT）的低场共振属于嘧啶-嘌呤（dTpdA）磷酸二酯键。因此，嘌呤-嘧啶步骤中的磷酸二酯键在聚（dA-dT）异构化过程中，在嘧啶-嘌呤磷酸二酯的Z形式出现方面起着类似的作用。这排除了poly（dA-dT）·poly（dA-dT）和poly（dG-dC）·poly（dG-dC）的高盐结构是相同构象家族的成员。我们把这种高盐构象称为poly（dA-dT）X-DNA。此外，根据综述，具有交替的嘌呤-嘧啶碱基序列的DNA合成分子可以采用Z形式或X形式，甚至两者兼而有之，这取决于环境条件。这将一个新的维度引入到DNA双螺旋构象变异性中。用天然DNA的线性分子进行的实验表明，X形式可能具有生物学意义。（400字处删节）
The article reviews data indicating that poly(dA-dT).poly(dA-dT) is able of adopting three distinct double helical structures in solution, of which only the A form conforms to classical notions. The other two structures have dinucleotides as double helical repeats. At low salt concentrations poly(dA-dT).poly(dA-dT) adopts a B-type alternating conformation which is exceptionally variable. Its architecture can gradually move in the limits demarcated by the CD spectra with inverted long wavelength CD bands and the 31P NMR spectra with a very low and a 0.6 ppm separation of two resonances. Contrary to Z-DNA, the 31P NMR spectrum of the limiting alternating B conformation of poly(dA-dT).poly(dA-dT) is characterized by an upfield shift of one resonance. We attribute the exceptional conformational flexibility of the alternating B conformation to the unequal tendency of bases in the dA-dT and dT-dA steps to stack. However, by assuming the limiting alternating B conformation, the variability of the synthetic DNA is not exhausted. Specific agents make it isomerize into another conformation by a fast, two-state mechanism, which is reflected by a further deepening of the negative long wavelength CD band and a downfield shift of the 31P NMR resonance of poly(dA-dT).poly(dA-dT) that was constant in the course of the gradual alterations of the alternating B conformation. These changes are, however, qualitatively different from the way poly(dG-dC).poly(dG-dC) behaves in the course of the B-Z isomerization. Poly(dG-dC).poly(dG-dC) displays purine-pyrimidine (dGpdC) resonance in the characteristic downfield position, while the downfield resonance of poly(dA-dT).poly(dA-dT) belongs to the pyrimidine-purine (dTpdA) phosphodiester linkages. Consequently, phosphodiester linkages in the purine-pyrimidine steps play a similar role in the appearance of the Z form to the pyrimidine-purine phosphodiesters in the course of the isomerization of poly(dA-dT).poly(dA-dT). This excludes that the high-salt structures of poly(dA-dT).poly(dA-dT) and poly(dG-dC).poly(dG-dC) are members of the same conformational family. We call the high-salt conformation of poly(dA-dT).poly(dA-dT) X-DNA. It furthermore follows from the review that synthetic molecules of DNA with alternating purine-pyrimidine sequences of bases can adopt either the Z form or the X form, or even both, depending on the environmental conditions. This introduces a new dimension into the DNA double helix conformational variability. The possible biological relevance of the X form is suggested by experiments with linear molecules of natural DNA.(ABSTRACT TRUNCATED AT 400 WORDS)
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影响因子：
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影响因子：
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作者：
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影响因子：
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作者：
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