The selectivity filter of voltage‐dependent channels formed by phosphoporin (PhoE protein) from E. coli

• Published in: The EMBO journal 1986-04, Vol.5 (4), p.773-778
• Main Authors: Dargent, B., Hofmann, W., Pattus, F., Rosenbusch, J.P.
• Format: Article
• Language: English
• Subjects: Adenosine Triphosphate - pharmacology; Bacterial Outer Membrane Proteins - metabolism; Bacteriology; Biological and medical sciences; Electric Conductivity; electron transport; Escherichia coli; Escherichia coli - metabolism; Fundamental and applied biological sciences. Psychology; Ion Channels - drug effects; Ion Channels - physiology; Membrane Potentials; Microbiology; outer membranes; Permeability, membrane transport, intracellular transport; Phosphorylation; Porins; proteins
• ISSN: 0261-4189; 1460-2075
• 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.