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Biophys J, December 1998, p. 2868-2876, Vol. 75, No. 6

Dehydration of Model Membranes Induced by Lectins from Ricinus communis and Viscum album

Peter Pohl, Sapar M. Saparov, Elena E. Pohl, Veronika Y. Evtodienko, Igor I. Agapov, and Alexander G. Tonevitsky

Medizinische Fakultät, Institut für Medizinische Physik und Biophysik, Martin Luther Universität, 06097 Halle, Germany

The effects of ribosome-inactivating proteins (RIPs) from Ricinus communis and from Viscum album on the water permeability, Pf, and the surface dielectric constant, varepsilon , of model membranes were studied. Pf was calculated from microelectrode measurements of the ion concentration distribution in the immediate vicinity of a planar membrane, and varepsilon  was obtained from the fluorescence of dansyl phosphatidylethanolamine incorporated into unilamellar vesicles. Pf and varepsilon  of fully saturated phosphatidylcholine membranes were affected only in the presence of a lectin receptor (monosialoganglioside, GM1) in the bilayer. It is suggested that the membrane area occupied by clustered lectin-receptor complexes is markedly less permeable to water. Protein binding to the receptor was not a prelude for hydrophobic lipid-protein interactions when the membranes were formed from a mixture of natural phospholipids with a high content of unsaturated fatty acids. These membranes, characterized by a high initial water permeability, were found to interact with the RIPs unspecifically. From a decrease of both Pf and varepsilon  it was concluded that not only water partitioning but also protein adsorption correlates with looser packing of polyunsaturated lipids at the lipid-water interface.

Biophys J, December 1998, p. 2868-2876, Vol. 75, No. 6
© 1998 by the Biophysical Society   0006-3495/98/12/2868/09  $2.00




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Copyright © 1998 by the Biophysical Society.