Delcour A H, Adler J, Kung C, Martinac B
Department of Biochemistry and Genetics, University of Wisconsin-Madison 53706.
FEBS Lett. 1992 Jun 15;304(2-3):216-20. doi: 10.1016/0014-5793(92)80622-n.
The outer membrane of Escherichia coli is a diffusion barrier for macromolecules, but allows the passage of small hydrophilic solutes through non-specific channels, the porins. Some electrophysiological studies find reconstituted porins in a mostly open state, while those done with the patch-clamp technique performed on live cells suggest that the vast majority of the native channels are closed. We present here current measurements through porins from reconstituted outer membrane, which demonstrate that bacterial metabolites, the MDO's, which bathe the periplasmic side of the outer membrane, induce the channels to close. These findings illustrate that the degree of openness of porins can be regulated by compounds naturally found in bacteria.
大肠杆菌的外膜是大分子的扩散屏障，但允许小的亲水性溶质通过非特异性通道——孔蛋白。一些电生理研究发现重组孔蛋白大多处于开放状态，而在活细胞上进行的膜片钳技术研究表明，绝大多数天然通道是关闭的。我们在此展示了通过重组外膜孔蛋白进行的电流测量，结果表明，存在于外膜周质侧的细菌代谢产物——膜衍生寡糖（MDO）会诱导通道关闭。这些发现表明，孔蛋白的开放程度可由细菌中天然存在的化合物调节。
