Ethidium binding to left-handed (Z) DNAs results in regions of right-handed DNA at the intercalation site.
Ethidium binding to left-handed (Z) DNAs results in regions of right-handed DNA at the intercalation site.
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乙锭与左手 (Z) DNA 结合会在嵌入位点产生右手 DNA 区域。
DOI：
10.1021/bi00346a065
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发表时间：
1985
期刊：
影响因子：
2.9
通讯作者：
Krugh,TR
中科院分区：
文献类型：
--
作者：
Walker,GT;Stone,MP;Krugh,TR
罗切斯特大学化学系，罗切斯特，纽约14627，1984年12月18日接收; 1985年5月20日接收修订的Mandarin pt摘要：通过光学和相分配技术研究了乙锭与聚（dG-dC）-聚（dG-dC）和聚（dG-m5 dC）-聚（dG-m5 dC）的右手（B）和左手（Z）形式的平衡结合。在B-型条件下，与Z-型条件下的高度合作结合形成鲜明对比的是，在非合作方式下，阿托溴铵与多核苷酸结合。结合等温线与圆二色性（CD）数据的相关性表明，Z-型条件下的合作结合的乙锭与聚合物从左手到右手构象的顺序转换。通过各种滴定技术和圆二色谱测定结合药物浓度，我们能够计算出每个结合药物的左旋DNA中采用右旋构象的碱基对的数目; 3-4个碱基对的左旋聚（dG-dC）> poly（dG-dC）在4.4M NaCl中对于每个结合的乙锭转换为右旋形式，而在40 µ [Co（NH3）6] Cl 3和聚（dG-m5 dC）-poly（dG-dC）的复合物中，每个结合的乙锭大约有25和7个碱基对转换构象。聚（dG-m5 dC）在2 mM MgCl 2中的溶液中。在4.4 M NaCl中的乙锭-聚（dG-dC）-聚（dG-dC）复合物在320 nm处的诱导椭圆率表明右手区域几乎被乙锭饱和，即使整体饱和水平非常低。圆二色性数据表明，即使在CD光谱显示大部分聚合物处于左手构象的低r值下，乙锭插入形成右手结合的药物区域。Wang等人，1979）清楚地说明了脱氧核糖核酸（DNA）1可以以多种构象存在，并且结构对DNA的功能具有显著影响[关于综述，参见Rich et al.（1984）和威尔斯埃塔尔。（1980），以及其中的参考文献]。聚（dG-dC）-聚（dG-dC）在4中呈现左手（Z-型）构象。4 M NaCl，直到乙锭浓度达到约20 µ时，乙锭才能有效结合（Pohl等人，1972年）。
Department of Chemistry, University of Rochester, Rochester, New York 14627 Received December 18, 1984; Revised Manuscript Received May 20, 1985 abstract: The equilibrium binding of ethidium to the right-handed (B) and left-handed (Z) forms of poly (dG-dC)-poly (dG-dC) and poly (dG-m5dC)-poly (dG-m5dC) was investigated by optical and phase partition techniques. Ethidium binds to the polynucleotides in a noncooperative manner under B-form conditions, in sharp contrast to highly cooperative binding under Z-form conditions. Correlation of binding isotherms with circular dichroism (CD) data indicates that the cooperative binding of ethidium under Z-form conditions is associated with a sequential conversion of the polymer from a left-handed to a right-handed conformation. Determination of bound drug concentrations by various titration techniques and the measurement of circular dichroism spectrahave enabled us to calculate the number of base pairs of left-handed DNA that adopt a right-handed conformation for each bound drug; 3-4 base pairs of left-handed poly (dG-dC> poly (dG-dC) in 4.4 M NaCl switch to the right-handedform for each bound ethidium, while approximately 25 and 7 base pairs switch conformationsfor each bound ethidium in complexes with poly (dG-dC)-poly (dG-dC) in 40 µ [Co (NH3) 6] Cl3 and poiy (dG-m5dC)-poly (dG-m5dC) in 2 mM MgCl2, respectively. The induced ellipticity at 320 nm for the ethidium-poly (dG-dC)-poly (dG-dC) complex in 4.4 M NaCl indicates that the right-handed regions are nearly saturated with ethidium even though the overall level of saturation is very low. The circular dichroism data indicate that ethidium intercalates to form a right-handed-bound drug region, even at low r values where the CD spectrashow that the majority of the polymer is in a left-handed conformation.The striking observation of the salt-induced cooperative conformational change of poly (dG-dC)-poly (dG-dC) from a right-handed helix to the left-handed (Z) helix (Pohl & Jovin, 1972; Wang et al., 1979) is a clear illustration that deoxy-ribonucleic acid (DNA) 1 can exist in a variety of conformations and that thestructure has a pronounced effect on the function of DNA [for reviews, see Rich et al.(1984) and Wells etal.(1980), and references therein]. Poly (dG-dC)-poly (dG-dC) assumes a left-handed (Z-form) conformation in4. 4 M NaCl, to whichethidium does not bindefficiently until the ethidium concentration reaches approximately 20 µ (Pohl et al., 1972).