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首页> 外文期刊>Journal of Molecular Biology >ALTERNATING AND NON-ALTERNATING DG-DC HEXANUCLEOTIDES CRYSTALLIZE AS CANONICAL A-DNA
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ALTERNATING AND NON-ALTERNATING DG-DC HEXANUCLEOTIDES CRYSTALLIZE AS CANONICAL A-DNA

机译：交替和非交替的DG-DC六核苷酸结晶为规范A-DNA

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We have solved the-single-crystal X-ray structures of two different hexanucleotides: the alternating sequence d(Gm(5)CGm(5)CGC), and the non-alternating sequence d(Gm(5)CCGGC). Both of these hexamers crystallize readily as A-DNA in the orthorhombic space group C222(1). Although hexanucleotides have been previously crystallized as Z-DNA, and in one case as B-DNA, this is the first time hexanucleotides have been crystallized as A-DNA. Both hexamers adopt a typical A-conformation, which is surprisingly more similar to the structure of A-DNA fibers than to other A-DNA single crystals. The structure of d(Gm(5)CGm(5)CGC) was solved to a resolution of 2.1 Angstrom (R-factor = 19.6%). This structure has all of the features characteristic of canonical A-DNA, including it's helical repeat (11.2 bp/ turn), helical. rise (2.6 Angstrom/bp), base-pair displacement (-4.7 Angstrom), base inclination angle (16.9 degrees), and sugar puckers that are predominantly 3'-endo. The lower resolution, non-alternating structure has similar overall average values for these parameters. We observed several sequence-dependent correlations in these parameters, especially in the d(CG) base step. These steps have lower twist and rise values, coupled with high roll angles as compared to d(GC) steps. The molecular interactions involved in crystal packing and the detailed structure of the bound water in the crystals, however, are similar to those of longer 8 and 10 bp A-DNA crystal structures. Although the structural effect of cytosine methylation on A-DNA appears to be minimal, this modification significantly affects the ability of these sequences to crystallize as A-DNA. In conclusion, we present the A-DNA forming class of hexanucleotides, a new crystallographic system for studying DNA structure at near atomic resolution. [References: 36]
机译：我们已经解决了两个不同六核苷酸的单晶X射线结构：交替序列d（Gm（5）CGm（5）CGC）和非交替序列d（Gm（5）CCGGC）。这两种六聚体都容易在正交空间组C222（1）中作为A-DNA结晶。尽管六核苷酸先前已结晶为Z-DNA，在一种情况下为B-DNA，但这是六核苷酸首次结晶为A-DNA。两种六聚体均具有典型的A构象，这与A-DNA纤维的结构相比，与其他A-DNA单晶的结构更令人惊讶。 d（Gm（5）CGm（5）CGC）的结构解析为2.1埃的分辨率（R因子= 19.6％）。这种结构具有典型A-DNA的所有特征，包括螺旋重复（11.2 bp /匝），螺旋。上升（2.6埃/ bp），碱基对位移（-4.7埃），碱基倾斜角（16.9度）和主要是3'-endo的糖折叠。对于这些参数，较低分辨率的非交替结构具有相似的总体平均值。我们在这些参数中观察到了几个依赖序列的相关性，尤其是在d（CG）基本步骤中。与d（GC）步骤相比，这些步骤具有较低的扭曲和上升值，并具有高侧倾角。然而，参与晶体堆积的分子相互作用和晶体中结合水的详细结构与较长的8和10 bp A-DNA晶体结构相似。尽管胞嘧啶甲基化对A-DNA的结构作用似乎很小，但这种修饰显着影响了这些序列结晶为A-DNA的能力。总之，我们提出了六核苷酸的A-DNA形成类，这是一种用于研究接近原子分辨率的DNA结构的新型晶体学系统。 [参考：36]

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