LARGE-SCALE RECONSTITUTION OF CRYSTALLINE BACTERIAL SURFACE-LAYER PROTEINS AT THE AIR-WATER-INTERFACE AND ON LIPID FILMS

Isolated subunits from the crystalline cell surface (S layer) proteins of Bacillus sphaericus CCM2177 could be recrystallized into large coh erent double layers at the air-water interface and as monolayers on di palmitoylphosphatidylcholine and dipalmitoylphosphatidylethanolamine ( DPPE) monolayer films spread on a Langmuir-Blodgett (LB) trough. The r ecrystallized S layer proteins and the S layer/DPPE layers could be ch emically cross-linked from the subphase with glutaraldehyde. This cros s-linking step enhanced the stability of the recrystallized S layer pr otein films and the composite S layer/DPPE layers considerably for sub sequent handling procedures. By transferring a second phospholipid fil m onto the S layer/DPPE layers it was possible to mimic the structural principle of those archaeobacterial cell envelopes which are exclusiv ely composed of a plasma membrane and a closely associated S layer. Th e high stability of S layer supported lipid membranes and the possibil ity for producing this composite structure on a large scale by standar d LB techniques open new ways for exploiting structural and functional principles of membrane associated and integrated molecules.