Schultz P, Célia H, Riva M, Sentenac A, Oudet P
Laboratoire de Génétique Moléculaire des Eucaryotes, France.
EMBO J. 1993 Jul;12(7):2601-7. doi: 10.1002/j.1460-2075.1993.tb05920.x.
Two-dimensional crystals of yeast RNA polymerase I dimers were obtained upon interaction with positively charged lipid layers. A three-dimensional surface model of the enzyme was determined by analyzing tilted crystalline areas and by taking advantage of the non-crystallographic internal symmetry of the dimer to correct for the missing viewing directions. The structure shows, at approximately 3 nm resolution, an irregularly shaped molecule 11 nm x 11 nm x 15 nm in size characterized by a 3 nm wide and 10 nm long groove which constitutes a putative DNA binding site. The overall structure is similar to the Escherichia coli holo enzyme and the yeast RNA polymerase II delta 4/7 structures. The most remarkable structural feature is a finger-shaped stalk which partially occludes the entrance of the groove and forms a 2.5 nm wide channel. We discuss the possible location of the catalytic centre and of the carboxy-terminal region of the beta-like subunit in the channel. The interference of different DNA fragments with RNA polymerase dimerization and crystallization indicates the orientation of the template in the putative DNA binding groove.
酵母RNA聚合酶I二聚体与带正电荷的脂质层相互作用后可形成二维晶体。通过分析倾斜的晶体区域，并利用二聚体的非晶体学内部对称性来校正缺失的观察方向，确定了该酶的三维表面模型。该结构以约3纳米的分辨率显示出一个大小为11纳米×11纳米×15纳米的不规则形状分子，其特征是有一个3纳米宽、10纳米长的凹槽，构成一个假定的DNA结合位点。整体结构与大肠杆菌全酶和酵母RNA聚合酶II δ4/7结构相似。最显著的结构特征是一个手指状的柄，它部分地封闭了凹槽的入口并形成一个2.5纳米宽的通道。我们讨论了通道中催化中心和β样亚基羧基末端区域的可能位置。不同DNA片段对RNA聚合酶二聚化和结晶的干扰表明了模板在假定DNA结合凹槽中的取向。
