Characterization and Chemical Modification of Small Anion Specific Channels formed in Lipid Bilayer Membranes by Outer Membrane Protein P or Pseudomonas aeruginosa.

The movement of small molecules and ions across the outer membrane of gram-negative bacteria is mediated by a class of major proteins named porins (1). The porins form generally large water-filled pores with a diameter of 1.3-2.3 nm in the outer membrane (1) and in lipid bilayer membranes (2). These pores have a defined exclusion limit for hydrophilic solutes (3). A new outer membrane protein has been found to be induced in P. aeruginosa grown low-phosphate media. Studies with mutants have suggested that this protein, named protein P, is part of the phosphate uptake system (4). Lipid bilayer experiments suggested that the diameter of the protein-P pore is much smaller than that of the other porins(4).