Cowan S W, Garavito R M, Jansonius J N, Jenkins J A, Karlsson R, König N, Pai E F, Pauptit R A, Rizkallah P J, Rosenbusch J P, Rummel G, Schirmer T
Department of Structural Biology, University of Basel, Switzerland.
Department of Microbiology, University of Basel, Switzerland.
Structure. 1995 Oct 15;3(10):1041-50. doi: 10.1016/s0969-2126(01)00240-4.
OmpF porin is a trimeric integral membrane protein responsible for the passive transport of small hydrophilic molecules, such as nutrients and waste products, across the outer membrane of Escherichia coli. Very few membrane proteins have been crystallized in three dimensions, yet this stable protein can be obtained in several crystal forms. Comparison of the structures of the same membrane protein in two different packing environments is of major interest, because it allows us to explore the integrity of the structure outside the natural membrane environment.
The structure of OmpF porin in a tetragonal crystal form with two trimers per asymmetric unit has been determined at 3.2 A resolution and compared with that obtained previously in a trigonal crystal form. The lattice contacts involve only polar atoms, whereas extensive hydrophobic protein-protein interactions were found in the trigonal lattice. The trimer structure is virtually identical in both.
Our comparison reveals that the overall structure of OmpF is not influenced by crystal lattice constraints and, thus, presumably bears close resemblance to the in vivo structure. The tetragonal crystal structure has provided the starting model for the phasing of neutron diffraction data obtained from this crystal form, as described in an accompanying article.
外膜孔蛋白F（OmpF）是一种三聚体整合膜蛋白，负责诸如营养物质和代谢废物等小的亲水分子在大肠杆菌外膜上的被动运输。很少有膜蛋白能够被三维结晶，然而这种稳定的蛋白能够以几种晶体形式获得。对处于两种不同堆积环境下的同一膜蛋白结构进行比较具有重要意义，因为这使我们能够在天然膜环境之外探究该结构的完整性。
已确定了四方晶型的OmpF孔蛋白结构，每个不对称单元中有两个三聚体，分辨率为3.2埃，并与之前获得的三角晶型结构进行了比较。晶格接触仅涉及极性原子，而在三角晶格中发现了广泛的疏水蛋白-蛋白相互作用。两种晶型中的三聚体结构实际上是相同的。
我们的比较表明，OmpF的整体结构不受晶格限制的影响，因此，推测与体内结构非常相似。如随附文章中所述，四方晶体结构为从该晶型获得的中子衍射数据的相位分析提供了起始模型。
Zotero 插件