Low-temperature crystallographic analyses of the binding of Hoechst 33258 to the double-helical DNA dodecamer C-G-C-G-A-A-T-T-C-G-C-G.
Low-temperature crystallographic analyses of the binding of Hoechst 33258 to the double-helical DNA dodecamer C-G-C-G-A-A-T-T-C-G-C-G.
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DOI：
10.1021/bi00106a030
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发表时间：
1991-10
期刊：
影响因子：
2.9
通讯作者：
J. Quintana;A. Lipanov;Richard E. Dickerson
中科院分区：
文献类型：
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作者：
J. Quintana;A. Lipanov;Richard E. Dickerson
从三种不同低温(0、-25和-100℃)下收集的X射线数据解析了Hoechst 33258与十二聚体C-G-C-G-A-A-T-T-C-G-C-G的晶体结构。这样的温度使得收集比以前对同一复合体的X射线研究更高的分辨率数据(分别为2.0、1.9和2.0安培)成为可能。在所有三种情况下，药物都位于小沟中央狭窄的A-A-T-T区域。在-25摄氏度和-100摄氏度(每种结晶溶液中药物/DNA的比例为1：1)下进行的数据分析表明，药物具有独特的取向。相反，当药物/DNA在溶液中的比例为2：1时，在0摄氏度下，药物的两种取向都是同样可能的。Hoechst 33258环之间的二面角似乎以依赖于温度的方式改变。药物/DNA复合物是通过Hoechst和腺嘌呤N3的苯并咪唑环上的两个N-H氢键给体与小凹槽中的胸腺嘧啶O2受体之间的单一或分叉氢键来稳定的。对AT区的一般偏好是由静电势和沟槽壁变窄所赋予的。局部逐点AT的特异性来自Hoechst 33258中的环氢原子和腺嘌呤的C2氢之间的紧密范德华接触。在Hoechst 33258的较长链类似物中用嘌呤取代一个苯并咪唑环可以使该特定位置的GC具有耐受性，就像在咪唑取代来昔洛辛中的吡咯时观察到的那样。
The crystal structure of the complex of Hoechst 33258 and the DNA dodecamer C-G-C-G-A-A-T-T-C-G-C-G has been solved from X-ray data collected at three different low temperatures (0, -25, and -100 degrees C). Such temperatures have permitted collection of higher resolution data (2.0, 1.9, and 2.0 A, respectively) than with previous X-ray studies of the same complex. In all three cases, the drug is located in the narrow central A-A-T-T region of the minor groove. Data analyses at -25 and -100 degrees C (each with a 1:1 drug/DNA ratio in the crystallizing solution) suggest a unique orientation for the drug. In contrast, two orientations of the drug were found equally possible at 0 degrees C with a 2:1 drug/DNA ratio in solution. Dihedral angles between the rings of Hoechst 33258 appear to change in a temperature-dependent manner. The drug/DNA complex is stabilized by single or bifurcated hydrogen bonds between the two N-H hydrogen-bond donors in the benzimidazole rings of Hoechst and adenine N3 and thymine O2 acceptors in the minor groove. A general preference for AT regions is conferred by electrostatic potential and by narrowing of the walls of the groove. Local point-by-point AT specificity follows from close van der Waals contacts between ring hydrogen atoms in Hoechst 33258 and the C2 hydrogens of adenines. Replacement of one benzimidazole ring by purine in a longer chain analogue of Hoechst 33258 could make that particular site GC tolerant in the manner observed at imidazole substitution for pyrrole in lexitropsins.