This paper proposes a method for sensing affinity interactions by triggering disruption of self-assembly of ion channel-forming peptides in planar lipid bilayers. It shows that the binding of a derivative of alamethicin carrying a covalently attached sulfonamide ligand to carbonic anhydrase II (CA II) resulted in the inhibition of ion channel conductance through the bilayer. We propose that the...

Synthetic peptides designed using criteria derived from statistical analyses of beta-barrel membrane proteins form channels in synthetic membranes at very low peptide:lipid ratios.

NC-1059, a synthetic channel-forming peptide, transiently increases transepithelial electrical conductance (g(TE)) and ion transport (as indicated by short-circuit current) across Madin-Darby canine kidney (MDCK) cell monolayers in a time- and concentration-dependent manner when apically exposed. g(TE) increases from <2 to >40 mS/cm(2) over the low to middle micromolar range. Dextran polymer (9...

Here we review the mechanisms that bacterial cells use to protect themselves against channel-forming colicins. Four mechanisms are examined: immunity, resistance, tolerance and PacB character. Immunity confers protection to colicinogenic cells against the colicin they produce, since the colicinogenic plasmid bears the genetic determinant for such immunity protein. Resistance is provided by modi...

To intoxicate cells, pore-forming bacterial toxins are evolved to allow for the transmembrane traffic of different substrates, ranging from small inorganic ions to cell-specific polypeptides. Recent developments in single-channel electrical recordings, X-ray crystallography, protein engineering, and computational methods have generated a large body of knowledge about the basic principles of cha...

Detergent extracts of cell envelopes of the gliding bacterium Herpetosiphon aurantiacus formed channels in lipid bilayers. Fast protein liquid chromatography across a HiTrap-Q cation-exchange column demonstrated that a 45-kDa protein forms the channel. The observation of a channel-forming protein suggests that Herpetosiphon aurantiacus Hp a2 has a permeability barrier on its surface.

Different routes of assembly are probed for the transmembrane domain (TMD) of the bitopic membrane protein Vpu from HIV-1. Vpu is responsible for the amplification of viral release from the host cell. The mode of action includes (i) heteroassembly with host factors and (ii) the formation of homo-oligomers, which are able to conduct ions across the lipid membrane. Two different routes of assembl...

The D enantiomers of three naturally occurring antibiotics--cecropin A, magainin 2 amide, and melittin--were synthesized. In addition, the D enantiomers of two synthetic chimeric cecropin-melittin hybrid peptides were prepared. Each D isomer was shown by circular dichroism to be a mirror image of the corresponding L isomer in several solvent mixtures. In 20% hexafluoro-2-propanol the peptides c...

The outer membrane of the thermophilic bacterium Thermus thermophilus was isolated using sucrose step gradient centrifugation. Its detergent extracts contained an ion-permeable channel with an extremely high single-channel conductance of 20 nS in 1 M KCl. The channel protein was purified by preparative sodium dodecyl sulfate (SDS)-polyacylamide gel electrophoresis. It has a high molecular mass ...