Harper A, Brannigan J A, Buck M, Hewitt L, Lewis R J, Moore M H, Schneider B
Department of Chemistry, University of York, Heslington, York YO1 5DD, England.
Acta Crystallogr D Biol Crystallogr. 1998 Nov 1;54(Pt 6 Pt 2):1273-84. doi: 10.1107/s0907444998002807.
The X-ray crystal structure of d(TGCGCA)2 has been determined at 120 K to a resolution of 1.3 A. Hexamer duplexes, in the Z-DNA conformation, pack in an arrangement similar to the 'pure spermine form' [Egli et al. (1991). Biochemistry, 30, 11388-11402] but with significantly different cell dimensions. The phosphate backbone exists in two equally populated discrete conformations at one nucleotide step, around phosphate 11. The structure contains two ordered cobalt hexammine molecules which have roles in stabilization of both the Z-DNA conformation of the duplex and in crystal packing. A comparison of d(TGCGCA)2 with other Z-DNA hexamer structures available in the Nucleic Acid Database illustrates the elusive nature of crystal packing. A review of the interactions with the metal cations Na+, Mg2+ and Co3+ reveals a relatively small proportion of phosphate binding and that close contacts between metal ions are common. A prediction of the water structure is compared with the observed pattern in the reported structure.
已在120 K下测定了d(TGCGCA)2的X射线晶体结构，分辨率为1.3 Å。呈Z-DNA构象的六聚体双链体以类似于“纯精胺形式”[埃格利等人（1991年）。《生物化学》，30，11388 - 11402]的排列方式堆积，但晶胞尺寸有显著差异。在一个核苷酸步长处，围绕磷酸11，磷酸主链存在两种数量相等的离散构象。该结构包含两个有序的六氨合钴分子，它们在双链体的Z-DNA构象稳定以及晶体堆积中都发挥作用。将d(TGCGCA)2与核酸数据库中其他可用的Z-DNA六聚体结构进行比较，说明了晶体堆积难以捉摸的性质。对与金属阳离子Na+、Mg2+和Co3+的相互作用进行的综述表明，磷酸盐结合的比例相对较小，并且金属离子之间的紧密接触很常见。将水结构的预测与报道结构中观察到的模式进行了比较。
