Lipid-Mediated Inactivation of Colicin E1 Channels by Calcium Ions

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A. A. Sobko¹, E. A. Kotova¹, S. D. Zakharov^2,3, W. A. Cramer², and Y. N. Antonenko^1*

¹Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 119992 Moscow, Russia; fax: (7-495) 939-3181; E-mail: antonen@genebee.msu.su

²Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907, USA; fax: (765) 494-4956; E-mail: wac@bilbo.bio.purdue.edu

³Institute of Basic Problems of Biology, Russian Academy of Sciences, 142290 Pushchino, Moscow Region, Russia; fax: (7-496) 779-0532; E-mail: zakharos@purdue.edu

^* To whom correspondence should be addressed.

Received June 23, 2005; Revision received September 2, 2005

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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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KEY WORDS: bilayer lipid membrane, spontaneous curvature, ionic channels, colicin E1, calcium

DOI: 10.1134/S0006297906010159

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