POLY(DA).POLY(DT) IS A B-TYPE DOUBLE HELIX WITH A DISTINCTIVELY NARROW MINOR GROOVE
POLY(DA).POLY(DT) IS A B-TYPE DOUBLE HELIX WITH A DISTINCTIVELY NARROW MINOR GROOVE
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DOI：
10.1038/325821a0
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发表时间：
1987-02-26
期刊：
影响因子：
64.8
通讯作者：
SKURATOVSKII, IY
中科院分区：
文献类型：
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作者：
ALEXEEV, DG;LIPANOV, AA;SKURATOVSKII, IY
poly（dA）→ poly（dT）的结构目前引起了极大的兴趣，主要是因为dAn → dTn延伸与相当大的DNA弯曲相关1，2。直到最近，Arnottet等人3所描述的异序DNA（poly（dA）和poly（dT）链分别处于A和B构象）是这种结构的唯一详细模型。在我们早期对DNA和单价离子相互作用的研究4 -6之后，我们检查了聚（dA）-聚（dT）的二价Ca 2+盐（Ca-聚（dA）-聚（dT））的X射线衍射，没有发现异质结构的迹象：纤维中的Ca-聚（dA）-聚（dT）显示出完全等效的相反糖-磷酸链的B型构象。基于这一结果，对钠盐结构的修正，Na-聚（dA）.聚（dT），只产生了一个轻微的异规结构，每个链都处于B型构象，这与原始异规模型的实验数据更好地吻合。两种结构，Ca-和Na-聚（dA）-聚（dT），具有比B形式更窄的小沟：这种特性似乎对聚（dA）-聚（dT）和生物学上重要的分子（包括蛋白质和抗生素）的相互作用非常重要。poly（dA）→ poly（dT）中的特定碱基对位置可以解释邻近dAn-dIntracts的DNA弯曲。
The structure of poly(dA)ṁpoly(dT) currently arouses great interest, mainly because dAnṁdTnstretches are associated with considerable DNA bending1,2. Until recently the heteronomous DNA described by Arnottet al.3, with the poly(dA) and poly(dT) chains in A and B conformations respectively, was the only detailed model of this structure. Following our earlier studies of the interaction of DNA and monovalent ions4–6, we examined the X-ray diffraction of the bivalent Ca2+salt of poly(dA)-poly(dT) (Ca-poly(d A)ṁpoly(dT)) and found no sign of a heteronomous structure: Ca-poly(dA)ṁpoly(dT) in fibres shows fully equivalent B-type conformations of the opposite sugar–phosphate chains. A revision of the structure of the sodium salt, Na-poly(dA).poly(dT), based on this result, yields only a slightly heteronomous structure with each chain in a B-type conformation, which is in much better agreement with the experimental data underlying the original heteronomous model3. Both structures, Ca- and Na-poly(dA)ṁpoly(dT), have a minor groove narrower than that of the B form: this peculiarity seems to be very important for the interaction of poly(d A)ṁpoly(dT) and biologically significant molecules (including proteins and antibiotics). The specific base-pair positions in poly(dA)ṁpoly(dT) may account for the DNA bending adjacent to dAn-dTntracts.