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Updated: Jun 2, 2026

Gramicidin-based Fluorescence Assay; for Determining Small Molecules Potential for Modifying Lipid Bilayer Properties
Published on: October 13, 2010
Membrane phosphate headgroups' modulation of permeation of alkaline cations in gramicidin channels
Carlos Marcelo G de Godoy1, Samuel Cukierman
1Department of Cell and Molecular Physiology, Loyola University Medical Center, 2160 South First Avenue, Maywood, Illinois 60153, USA. gurjao.godoy@unifesp.br
Abstract:
The function of membrane proteins is modulated by lipid bilayers. The permeation of ions in gramicidin A channels (gA) is markedly distinct in monoglyceride and phospholipid membranes. It was previously demonstrated that membrane phosphate headgroups accelerate the rate of proton transfer in gA. However, the permeation of alkalines in gA channels is considerably slower in phospholipid than in monoglyceride membranes. In this study, gA channels were reconstituted in various membranes of ceramides, monoglycerides, phospholipids, or sphingolipids. It is demonstrated that single channel conductances to alkalines are similar among bilayers consisting of phospholipids and sphingolipids, and ceramides and monoglycerides. The presence of phosphate headgroups in membranes (and not the double acyl chains in lipids) attenuates alkaline permeation and enhances the proton transfer permeation in gA channels. In ceramide membranes in low ionic strength (<250 mM) solutions, gA channels become dysfunctional. The experimental results are discussed in regard to membrane/solution and membrane/protein interfaces.
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