Lipid-mediated inactivation of colicin E1 channels by calcium ions |
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Authors: | A. A. Sobko E. A. Kotova S. D. Zakharov W. A. Cramer Y. N. Antonenko |
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Affiliation: | (1) Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 119992 Moscow, Russia;(2) Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907, USA;(3) Institute of Basic Problems of Biology, Russian Academy of Sciences, 142290 Pushchino, Moscow Region, Russia |
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Abstract: | Based on the model of a toroidal protein-lipid pore, the effect of calcium ions on colicin E1 channel was predicted. In electrophysiological experiments Ca2+ suppressed the activity of colicin E1 channels in membranes formed of diphytanoylphosphatidylglycerol, whereas no desorption of the protein occurred from the membrane surface. The effect of Ca2+ was not observed on membranes formed of diphytanoylphosphatidylcholine. Single-channel measurements revealed that Ca2+-induced reduction of the colicin-induced current across the negatively charged membrane was due to a decrease in the number of open colicin channels and not changes in their properties. In line with the toroidal model, the effect of Ca2+ on the colicin E1 channel-forming activity is explained by alteration of the membrane lipid curvature caused by electrostatic interaction of Ca2+ with negatively charged lipid head groups. |
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Keywords: | bilayer lipid membrane spontaneous curvature ionic channels colicin El calcium |
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