Premium
Electrophysiological evidence for heptameric stoichiometry of ion channels formed by Staphylococcus aureus alpha‐toxin in planar lipid bilayers
Author(s) -
Krasilnikov Oleg V.,
Merzlyak Petr G.,
Yuldasheva Liliya N.,
Rodrigues Cláudio G.,
Bhakdi Sucharit,
Valeva Angela
Publication year - 2000
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1046/j.1365-2958.2000.02080.x
Subject(s) - biology , staphylococcus aureus , electrophysiology , ion channel , toxin , lipid bilayer , biophysics , microbiology and biotechnology , biochemistry , membrane , genetics , bacteria , receptor , neuroscience
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 single channels, these were manifest as stepwise changes in conductance, each step most probably reflecting modification of a single SH group within the oligomer. Because seven steps were observed, the functional channel formed by alpha‐toxin in planar lipid membranes is a heptamer.