Synchrotron Radiation Research Section, MCL, National Cancer Institute, Argonne National Laboratory, Argonne, IL 60439, USA.
Department of Crystallography, Faculty of Chemistry, A. Mickiewicz University, Poznan, Poland.
Acta Crystallogr D Struct Biol. 2017 Nov 1;73(Pt 11):940-951. doi: 10.1107/S2059798317014954. Epub 2017 Oct 30.
DNA oligomer duplexes containing alternating cytosines and guanines in their sequences tend to form left-handed helices of the Z-DNA type, with the sugar and phosphate backbone in a zigzag conformation and a helical repeat of two successive nucleotides. Z-DNA duplexes usually crystallize as hexagonally arranged parallel helical tubes, with various relative orientations and translation of neighboring duplexes. Four novel high-resolution crystal structures of d(CGCGCG) duplexes are described here. They are characterized by a high degree of pseudosymmetry and/or twinning, with three or four independent duplexes differently oriented in a monoclinic P2 lattice of hexagonal metric. The various twinning criteria give somewhat conflicting indications in these complicated cases of crystal pathology. The details of molecular packing in these crystal structures are compared with other known crystal forms of Z-DNA.
含有交替胞嘧啶和鸟嘌呤的 DNA 寡聚体双链倾向于形成左手螺旋的 Z-DNA 类型，其糖和磷酸骨架呈锯齿状构象，螺旋重复两个连续的核苷酸。Z-DNA 双链通常结晶为六方排列的平行螺旋管，具有各种相对取向和相邻双链的平移。本文描述了四个新的 d(CGCGCG)双链的高分辨率晶体结构。它们的特点是具有高度的拟对称性和/或孪晶，在六方度量的单斜 P2 晶格中，三个或四个独立的双链以不同的方向取向。在这些复杂的晶体病理学情况下，各种孪晶标准给出了有些矛盾的指示。这些晶体结构中分子堆积的细节与其他已知的 Z-DNA 晶体形式进行了比较。
