Interaction of bacterial surface layer proteins with lipid membranes: Synergysm between surface charge density and chain packing

HOLLMANN, AXEL; DELFEDERICO, LUCRECIA; DE ANTONI, GRACIELA; SEMORILE, LILIANA; DISALVO, ANIBAL

COLLOIDS AND SURFACES B-BIOINTERFACES

ELSEVIER SCIENCE BV

Año: 2010 vol. 79 p. 191 - 197

0927-7765

In this work we study the interactions of S-layer proteins from Lactobacillus kefir and Lactobacillus brevis with lipid membranes, first we show by freeze-fracture TEM micrographs that S-layer proteins from both lactobacilli are able to adsorb on whole surface of positively charged liposomes prepared with Soybean lecithin, cholesterol and stearylamine. The attachment of S-layer proteins produces an increase in the rigidity of liposome bilayer, measured by means of the DPH anisotropy < r > and Laurdan generalized polarization (GP). This effect on membrane phase state can be explained by the counteracting of the electrostatic charge repulsion between stearylamine molecules by the interaction with  negative groups of the protein in the membrane surface. Also we show by means of the dequenching rate of octadecyl-rhodamine that S-layer proteins from Lactobacillus kefir and Lactobacillus brevis are able to stabilize liposomes. The results indicate that S-layer coated-liposomes do not show spontaneous dequenching in comparison with control liposomes without S-layer proteins, suggesting that S-layer protein avoid spontaneous liposomal fusion. It is concluded that the increase in stability of liposomes coated with S-layers proteins is due to the higher rigidity induced by the S-layer attachment by electrostatic forces.