Pauptit R A, Schirmer T, Jansonius J N, Rosenbusch J P, Parker M W, Tucker A D, Tsernoglou D, Weiss M S, Schultz G E
Biocenter, University of Basel, Switzerland.
J Struct Biol. 1991 Oct;107(2):136-45. doi: 10.1016/1047-8477(91)90017-q.
Four new crystal packings of Escherichia coli porins are presented (phosphoporin, maltoporin, and two crystal forms of matrix porin). These were determined by molecular replacement methods using a polyalanine trial model acquired from the refined coordinates of porin from Rhodobacter capsulatus. The successful molecular replacement shows that the dominant motif found in R. capsulatus porin (a 16-stranded antiparallel beta-barrel) also applies to the E. coli porins, despite the lack of significant amino acid sequence homology. A 30 degrees-40 degrees tilt of the beta-strands with respect to the membrane normal was derived from the intensity distributions in the X-ray diffraction patterns for each porin studied, stressing their similarity. In view of the evolutionary distance between enteric and photosynthetic bacteria, the antiparallel beta-barrel may have significance as a basic structural motif for the formation of bacterial membrane channel structures.
本文介绍了大肠杆菌孔蛋白的四种新晶体结构（磷酸孔蛋白、麦芽孔蛋白以及基质孔蛋白的两种晶体形式）。这些结构是通过分子置换法确定的，使用的是从荚膜红细菌孔蛋白的精细坐标中获取的聚丙氨酸试验模型。成功的分子置换表明，尽管缺乏显著的氨基酸序列同源性，但在荚膜红细菌孔蛋白中发现的主要基序（一个16股反平行β桶）也适用于大肠杆菌孔蛋白。通过对所研究的每种孔蛋白的X射线衍射图谱中的强度分布得出，β链相对于膜法线倾斜30度至40度，强调了它们的相似性。鉴于肠道细菌和光合细菌之间的进化距离，反平行β桶作为形成细菌膜通道结构的基本结构基序可能具有重要意义。
