Microcin E492 forms ion channels in phospholipid bilayer membrane.
Microcin E492, a polypeptide antibiotic, has been shown to have an M(r) of 6,000 by urea-SDS-polyacrylamide gel electrophoresis of the fluorescently labelled compound. It is known that the bactericidal action of microcin involves a loss of the transmembrane potential. In this study we show that microcin forms cation-selective channels in planar phospholipid bilayers. The channels have two main conductance states the current-voltage curves of which rectify. The reversal potentials measured under biionic conditions indicate a permeability sequence of NH4+ > K+ = Rb+ = Cs+ > Na+ = Na+ = Li+ > Tris+. The results suggest that membrane potential dissipation induced by microcin is a consequence of the formation of pores in the bacterial membrane.
Lagos
R
R
Departamento de Biología, Facultad de Ciencias, Universidad de Chile, Santiago.
Wilkens
M
M
Vergara
C
C
Cecchi
X
X
Monasterio
O
O
D000900:Anti-Bacterial Agents / Q000737:chemistry*; D001430:Bacteriocins / Q000737:chemistry*; D004553:Electric Conductivity; D007473:Ion Channels / Q000502:physiology*; D008051:Lipid Bilayers; D008564:Membrane Potentials; D008954:Models, Biological; D010713:Phosphatidylcholines; D010714:Phosphatidylethanolamines
D000900:Anti-Bacterial Agents; D001430:Bacteriocins; D007473:Ion Channels; D008051:Lipid Bilayers; D010713:Phosphatidylcholines; D010714:Phosphatidylethanolamines; C057561:1-palmitoyl-2-oleoylphosphatidylethanolamine; C020411:microcin