Jap B K, Downing K H, Walian P J
Cell and Molecular Biology Division, Lawrence Berkeley Laboratory, University of California, Berkeley 94720.
J Struct Biol. 1990 Mar;103(1):57-63. doi: 10.1016/1047-8477(90)90086-r.
The structure of PhoE porin in projection normal to the membrane plane has been determined to a resolution of about 3.5 A by electron crystallographic techniques. The purified protein was reconstituted with lipid to form two-dimensional crystals. High resolution images and electron diffraction patterns of these specimens embedded in trehalose were recorded to obtain respectively the structure factor phase information and the more accurate values of the amplitude. The projection map shows interesting features that are not seen in the earlier map at 6.5 A. Details of the trimeric ring-like structures in our earlier map are now resolved. Each ring-like structure consists of "beads" with interbead spacings of about 4-6 A. These beads are interpreted as the projections of beta-strands along the strands' axes. At the center of the trimeric structure, there is a low density region that we proposed previously to be the location of lipopolysaccharide. Within each ring-like structure, there are complicated features which may play an important role in the size, selectivity, and stability of the channel.
通过电子晶体学技术，已确定 PhoE 孔蛋白在垂直于膜平面方向上投影的结构，分辨率约为 3.5 Å。纯化后的蛋白与脂质重构形成二维晶体。记录了嵌入海藻糖中的这些标本的高分辨率图像和电子衍射图谱，分别获得结构因子相位信息和更精确的振幅值。投影图显示出一些在早期 6.5 Å 图谱中未见到的有趣特征。我们早期图谱中三聚体环状结构的细节现在已得到解析。每个环状结构由“珠子”组成，珠子间间距约为 4 - 6 Å。这些珠子被解释为β - 链沿链轴的投影。在三聚体结构的中心，有一个低密度区域，我们之前认为这是脂多糖的位置。在每个环状结构内，存在一些复杂的特征，这些特征可能在通道的大小、选择性和稳定性方面发挥重要作用。
