Reconstitution of an ordered structure from major outer membrane constituents and the lipoprotein-bearing peptidoglycan sacculus of Escherichia coli

Abstract

An ordered hexagonal lattice structure with a lattice constant of about 7 nm was reconstituted on the entire surface of the lipoprotein-bearing peptidoglycan from outer membrane protein O-8 and lipopolysaccharide. The lattice structure resembled that observed in the cell envelope which had been treated with sodium dodecyl sulfate (Steven et al., J. Cell Biol. 72:292-301, 1977). The omission of either O-8 or lipopolysaccharide resulted in the failure of formation of the lattice structure. No ordered lattice was formed on the peptidoglycan lacking the bound form of the lipoprotein. In the absence of the lipoprotein-bearing peptidoglycan, O-8 and lipopolysaccharide assembled into vesicles with an ordered hexagonal lattice, the lattice constant of which was also about 7 nm. A preliminary experiment indicated that protein O-9 gave the same result as did O-8. These results strongly indicate that O-8 and/or O-9 and lipopolysaccharide provide the ordered framework of the outer membrane and that the bound form of the lipoprotein plays a role in the holding of the framework on the peptidoglycan layer.