Jeanteur D, Lakey J H, Pattus F
European Molecular Biology Laboratory, Heidelberg, Germany.
Mol Microbiol. 1991 Sep;5(9):2153-64. doi: 10.1111/j.1365-2958.1991.tb02145.x.
The porins of Gram-negative bacteria are responsible for the 'molecular sieve' properties of the outer membrane. They form large water-filled channels which allow the diffusion of hydrophilic molecules into the periplasmic space. Owing to the strong hydrophilicity of their amino acid sequence and the nature of their secondary structure (beta strands), conventional hydropathy methods for predicting membrane topology are useless for this class of protein. The large number of available porin amino acid sequences was exploited to improve the accuracy of the prediction in combination with tools detecting amphipathicity of secondary structure. Using the constraints of beta-sheet structure these porins are predicted to contain 16 membrane-spanning strands, 14 of which are common to the two (enteric and the neisserial) porin subfamilies.
革兰氏阴性菌的孔蛋白负责外膜的“分子筛”特性。它们形成大型的充满水的通道，允许亲水分子扩散到周质空间。由于其氨基酸序列的强亲水性及其二级结构（β链）的性质，传统的预测膜拓扑结构的亲水性方法对这类蛋白质毫无用处。利用大量可用的孔蛋白氨基酸序列，结合检测二级结构两亲性的工具提高预测准确性。根据β折叠结构的限制，预计这些孔蛋白含有16条跨膜链，其中14条是两个（肠道和奈瑟氏）孔蛋白亚家族共有的。
