Dargent B, Hofmann W, Pattus F, Rosenbusch J P
EMBO J. 1986 Apr;5(4):773-8. doi: 10.1002/j.1460-2075.1986.tb04280.x.
Phosphoporin, an Escherichia coli outer membrane-spanning protein re-incorporated in phospholipid planar bilayers generates aqueous channels similar to those of matrix porin. One phosphoporin trimer contains three pores which are induced simultaneously but fluctuate separately between open and closed states. Membrane potential shifts this two-state equilibrium in favour of closed channels. This negative resistance occurs at lower potentials than with matrix porin channels. The phosphoporin channel is poorly anion selective for small solutes. Polyphosphates and other phosphorylated molecules specifically inhibit phosphoporin pore conductance to small ions, a property which is specific to phosphoporin. There is an excellent correlation between the effect of such solutes measured in planar bilayers and their inhibitory effect on beta-lactam antibiotic uptake in vivo by phosphoporin. It is concluded that the phosphoporin channel contains a selectivity filter which is only efficient for larger molecules, most probably through basic residues.
磷孔蛋白是一种重新整合到磷脂平面双分子层中的大肠杆菌外膜跨膜蛋白，它能产生类似于基质孔蛋白的水通道。一个磷孔蛋白三聚体包含三个孔，这些孔同时被诱导形成，但在开放和关闭状态之间分别波动。膜电位会使这种双态平衡向有利于关闭通道的方向移动。这种负电阻出现在比基质孔蛋白通道更低的电位下。磷孔蛋白通道对小溶质的阴离子选择性很差。多磷酸盐和其他磷酸化分子能特异性抑制磷孔蛋白对小离子的孔道电导，这是磷孔蛋白特有的性质。在平面双分子层中测量的此类溶质的效应与其对磷孔蛋白在体内摄取β-内酰胺抗生素的抑制效应之间存在极好的相关性。得出的结论是，磷孔蛋白通道含有一个选择性过滤器，该过滤器可能仅通过碱性残基对较大分子有效。
