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FEBS Lett. 1992 Jun 15;304(2-3):216-20.

Membrane-derived oligosaccharides (MDO's) promote closing of an E. coli porin channel.

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Department of Biochemistry and Genetics, University of Wisconsin-Madison 53706.


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.

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