title: Membrane phosphate headgroups' modulation of permeation of alkaline cations in gramicidin channels.
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.
authors.affiliation: Department of Cell and Molecular Physiology, Loyola University Medical Center, 2160 South First Avenue, Maywood, Illinois 60153, USA. gurjao.godoy@unifesp.br
authors.forename: Carlos Marcelo G
authors.initials: CM
authors.lastname: de Godoy
authors.forename: Samuel
authors.initials: S
authors.lastname: Cukierman
mesh_terms: D002412:Cations / Q000737:chemistry; D006096:Gramicidin / Q000737:chemistry*; D007473:Ion Channels / Q000737:chemistry*; D008563:Membrane Lipids / Q000737:chemistry*; D008672:Metals, Alkali / Q000737:chemistry*; D050178:Monoglycerides / Q000737:chemistry; D010710:Phosphates / Q000737:chemistry*; D010743:Phospholipids / Q000737:chemistry
chemical_list: D002412:Cations; D007473:Ion Channels; D008563:Membrane Lipids; D008672:Metals, Alkali; D050178:Monoglycerides; D010710:Phosphates; D010743:Phospholipids; D006096:Gramicidin