Large-scale reconstitution of crystalline bacterial surface layer proteins at the air-water interface and on lipid films

Abstract

Isolated subunits from the crystalline cell surface (S layer) proteins of Bacillus sphaericus CCM2177 could be recrystallized into large coherent double layers at the air-water interface and as monolayers on dipalmitoylpho-phatidylcholine and dipalmitoylphosphatidylethanolamine (DPPE) monolayer films spread on a Langmuir-Blodgett (LB) though. The recrystallized S layer proteins and the S layer/DPPE layers could be chemically cross-linked from the subphase with glutaraldehyde. This cross-linking step enhanced the stability of the recrystallized S layer protein films and the composite S layer/DPPE layers considerably for subsequent handling procedures. By transferring a second phospholipid film onto the S layer/DPPE layers it was possible to mimic the structural principle of those archaeobacterial cell envelopes which are exclusively composed of a plasma membrane and a closely associated S layer. The high stability of S layer supported lipid membranes and the possibility for producing this composite structure on a large scale by standard LB techniques open new ways for exploiting structural and functional principles of membrane associated and integrated molecules.