0000000000654024
AUTHOR
Liliya N. Yuldasheva
Pore formation by Vibrio cholerae cytolysin requires cholesterol in both monolayers of the target membrane
Vibrio cholerae cytolysin (VCC) forms oligomeric transmembrane pores in cholesterol-rich membranes. To better understand this process, we used planar bilayer membranes. In symmetric membranes, the rate of the channel formation by VCC has a superlinear dependency on the cholesterol membrane fraction. Thus, more than one cholesterol molecule can facilitate VCC-pore formation. In asymmetric membranes, the rate of pore formation is limited by the leaflet with the lower cholesterol content. Methyl-beta-cyclodextrin, which removes cholesterol from membranes, rapidly inhibits VCC pore formation, even when it is added to the side opposite that of VCC addition. The results suggest that cholesterol i…
Electrophysiological evidence for heptameric stoichiometry of ion channels formed by Staphylococcus aureus alpha-toxin in planar lipid bilayers.
Staphylococcal alpha-toxin forms homo-oligomeric channels in lipid bilayers and cell membranes. Here, we report that electrophysiological monitoring of single-channel function using a derivatized cysteine substitution mutant allows accurate determination of the subunit stoichiometry of the oligomer in situ. The electrophysiological phenotype of channels formed in planar lipid bilayers with the cysteine replacement mutant I7C is equal to that of the wild type. When pores were formed with I7C, alterations of several channel properties were observed upon modification with SH reagents. Decreases in conductance then occurred that were seen only as negative voltage was applied. At the level of si…