VOLTAGE-CLAMP STUDIES ON S-LAYER-SUPPORTED TETRAETHER LIPID-MEMBRANES

Isolated subunits from the cell surface proteins (S-layer) of Bacillus coagulans E38-66 have been recrystallized on a glycerol dialkyl nonit ol tetraether lipid (GDNT)-monolayer and the electrophysical features of this biomimetic membrane have been investigated in comparison to un supported GDNT-monolayers. The GDNT-monolayer, spread on a Langmuir-Bl odgett trough, was clamped with the tip of a glass patch pipette. In o rder to investigate the barrier function and potential to incorporate functional molecules, voltage-clamp examinations on plain and S-layer- supported GDNT-monolayers were performed. Our results indicate the for mation of a tight GDNT-monolayer sealing the tip of the glass pipette, and a decrease in conductance of the GDNT-monolayer upon recrystalliz ation of the S-layer protein. Thus, the S-layer protein, apparently, d id not penetrate or rupture the lipid monolayer. The valinomycin-media ted increase in conductance was less pronounced for the S-layer-suppor ted than for the plain GDNT-monolayer, indicating differences in the a ccessibility and/or in the fluidity of the lipid membranes. Furthermor e, in contrast to plain GDNT-monolayers, S-layer supported GDNT-monola yers with high valinomycin-mediated conductance persisted over long pe riods of time, indicating enhanced stability. These composite S-layer/ lipid films may constitute a new tool for electrophysical and electrop hysiological studies on membrane-associated and membrane-integrated bi omolecules. (C) 1998 Elsevier Science B.V.