Cowan S W, Schirmer T, Rummel G, Steiert M, Ghosh R, Pauptit R A, Jansonius J N, Rosenbusch J P
Department of Structural Biology, University of Basel, Switzerland.
Nature. 1992 Aug 27;358(6389):727-33. doi: 10.1038/358727a0.
Porins form aqueous channels that aid the diffusion of small hydrophilic molecules across the outer membrane of Gram-negative bacteria. The crystal structures of matrix porin and phosphoporin both reveal trimers of identical subunits, each subunit consisting of a 16-stranded anti-parallel beta-barrel containing a pore. A long loop inside the barrel contributes to a constriction of the channel where the charge distribution affects ion selectivity. The structures explain at the molecular level functional characteristics and their alterations by known mutations.
孔蛋白形成水通道，有助于小的亲水分子在革兰氏阴性菌的外膜上扩散。基质孔蛋白和磷酸孔蛋白的晶体结构均显示为由相同亚基组成的三聚体，每个亚基由一个含有孔道的16股反平行β桶组成。桶内部的一个长环导致通道变窄，此处的电荷分布影响离子选择性。这些结构在分子水平上解释了功能特征及其因已知突变而发生的改变。
