Hirano T, Kinoshita N, Morikawa K, Yanagida M
Department of Biophysics, Faculty of Science, Kyoto University, Japan.
Cell. 1990 Jan 26;60(2):319-28. doi: 10.1016/0092-8674(90)90746-2.
The S. pombe nuc2+ gene is required for mitotic chromosome disjunction. Its mutation arrests mitosis at the metaphase. The gene product is present in the nuclear scaffold-like fraction. The nuc2+ protein contains a domain, separated from ten 34 amino acid repeat segments, that is capable of binding AT-rich DNA in vitro. The ts mutation resides in one of the 34 amino acid repeats. Circular dichroism, limited proteolysis of the repeats, and model fitting indicate the presence of helical segments connected by protease-sensitive hinges. We propose that these repeats form a novel secondary structure (snap helix) having "knob and hole" helix-associating motifs. The packing of the snap helices would be stabilized by the bonding between the hydrophobic amino acids surrounding the knobs and holes. The nuc2+ protein may in one way bind to DNA and in another way mutually associate to form a part of the chromosome scaffold.
粟酒裂殖酵母的nuc2+基因对于有丝分裂染色体分离是必需的。其突变会使有丝分裂停滞在中期。该基因产物存在于核支架样组分中。nuc2+蛋白包含一个与十个34个氨基酸的重复片段分开的结构域，该结构域在体外能够结合富含AT的DNA。温度敏感突变位于其中一个34个氨基酸的重复片段中。圆二色性、对重复片段的有限蛋白酶解以及模型拟合表明存在由蛋白酶敏感铰链连接的螺旋片段。我们提出这些重复片段形成一种具有“旋钮和孔洞”螺旋缔合基序的新型二级结构（快速螺旋）。快速螺旋的堆积将通过旋钮和孔洞周围疏水氨基酸之间的结合而得以稳定。nuc2+蛋白可能以一种方式与DNA结合，以另一种方式相互缔合形成染色体支架的一部分。
