Shi Ke, Pan Baocheng, Sundaralingam Muttaiya
Department of Chemistry, The Ohio State University, 200 Johnston Laboratory, Columbus, OH 43210, USA.
Nucleic Acids Res. 2003 Mar 1;31(5):1392-7. doi: 10.1093/nar/gkg226.
The crystal structure of an alternating RNA heptamer r(GUAUACA) has been determined to 2.0 A resolution and refined to an R(work) of 17.1% and R(free) of 18.5% using 2797 reflections. The heptamer crystallized in the space group C222 with a unit cell of a = 25.74, b = 106.58, c = 30.26 A and two independent strands in the asymmetric unit. Each heptamer forms a duplex with its symmetry-related strand and each duplex contains six Watson-Crick base pairs and 3'-end adenosine overhangs. Therefore, two kinds of duplex (duplex 1 and duplex 2) are formed. Duplexes 1 stack on each other forming a pseudo-continuous column, which is typical of the RNA packing mode, while duplex 2 is typical of A-DNA packing with its termini in abutting interactions. Overhang adenine residues stack within the duplexes with C3'-endo sugar pucker and C2'-endo sugar pucker in duplexes 1 and 2, respectively. A Na+ ion in the crystal lattice is water bridged to two N1 atoms of symmetry-related A7 bases.
已确定交替RNA七聚体r(GUAUACA)的晶体结构分辨率为2.0 Å,并使用2797个反射将其精修至工作R因子为17.1%,自由R因子为18.5%。该七聚体在空间群C222中结晶,晶胞参数为a = 25.74、b = 106.58、c = 30.26 Å,不对称单元中有两条独立链。每个七聚体与其对称相关链形成一个双链体,每个双链体包含六个沃森-克里克碱基对和3'-端腺苷突出端。因此,形成了两种双链体(双链体1和双链体2)。双链体1相互堆叠形成一个假连续柱,这是RNA堆积模式的典型特征,而双链体2是A-DNA堆积的典型特征,其末端以邻接相互作用存在。突出的腺嘌呤残基分别在双链体1和双链体2中以C3'-内向糖构象和C2'-内向糖构象堆积在双链体内。晶格中的一个Na+离子通过水桥连接到对称相关A7碱基的两个N1原子上。