期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1981
卷号：78
期号：1
页码：172-176
DOI：10.1073/pnas.78.1.172
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：When exposed to a lipid bilayer, diphtheria toxin binds to it and forms transmembrane, voltage-dependent, anion-selective channels. The mean (+/- SD) conductance of these channels in asolectin membranes is 6.2 +/- 0.7 pmho (pS) in 0.2 M NaCl and 20 +/- 2 pmho in 1.0 M NaCl. The rate of channel formation depends on the pH in the toxin-containing compartment; it is very low at pH greater than 5.0 and increases abruptly as the pH decreases from 4.9 to 4.0. Binding of toxin to the membrane is also pH dependent, being unmeasurable at pH 7 and increasing monotonically with decreasing pH. The rate of channel formation depends upon membrane potential as well; channels form only at negative potentials. These channels are permanent in the time scale of the experiments (about 1 hr). The membrane conductance caused by the channels is also voltage dependent, being constant at positive potentials and decreasing at negative potentials. Hence, the current-voltage curve is linear at positive potentials and sublinear at negative potentials. The conditions necessary for insertion of toxin into the bilayer and formation of channels are similar to those that prevail inside the lysosome. Thus, these results lend credence to the idea that toxin enters the cytoplasm from the lysosomal compartment.
