title: The structure of Lactobacillus brevis surface layer reassembled on liposomes differs from native structure as revealed by SAXS.
abstract: The reassembly of the S-layer protein SlpA of Lactobacillus brevis ATCC 8287 on positively charged liposomes was studied by small angle X-ray scattering (SAXS) and zeta potential measurements. SlpA was reassembled on unilamellar liposomes consisting of 1-palmitoyl-2-oleyl-sn-glycero-3-phosphocholine and 1,2-dioleoyl-3-trimethylammonium-propane, prepared by extrusion through membranes with pore sizes of 50nm and 100nm. Similarly extruded samples without SlpA were used as a reference. The SlpA-containing samples showed clear diffraction peaks in their SAXS intensities. The lattice constants were calculated from the diffraction pattern and compared to those determined for SlpA on native cell wall fragments. Lattice constants for SlpA reassembled on liposomes (a=9.29nm, b=8.03nm, and γ=84.9°) showed a marked change in the lattice constants b and γ when compared to those determined for SlpA on native cell wall fragments (a=9.41nm, b=6.48nm, and γ=77.0°). The latter are in good agreement with values previously determined by electron microscopy. This indicates that the structure formed by SlpA is stable on the bacterial cell wall, but SlpA reassembles into a different structure on cationic liposomes. From the (10) reflection, the lower limit of crystallite size of SlpA on liposomes was determined to be 92nm, corresponding to approximately ten aligned lattice planes.
authors.affiliation: Department of Physics, P.O.B. 64, 00014 University of Helsinki, Finland. Electronic address: inkeri.kontro@helsinki.fi.
authors.forename: Inkeri
authors.initials: I
authors.lastname: Kontro
authors.affiliation: Department of Chemistry, P.O.B. 55, 00014 University of Helsinki, Finland.
authors.forename: Susanne K
authors.initials: SK
authors.lastname: Wiedmer
authors.affiliation: Department of Veterinary Biosciences, P.O.B. 66, 00014 University of Helsinki, Finland.
authors.forename: Ulla
authors.initials: U
authors.lastname: Hynönen
authors.affiliation: Department of Physics, P.O.B. 64, 00014 University of Helsinki, Finland.
authors.forename: Paavo A
authors.initials: PA
authors.lastname: Penttilä
authors.affiliation: Department of Veterinary Biosciences, P.O.B. 66, 00014 University of Helsinki, Finland.
authors.forename: Airi
authors.initials: A
authors.lastname: Palva
authors.affiliation: Department of Physics, P.O.B. 64, 00014 University of Helsinki, Finland.
authors.forename: Ritva
authors.initials: R
authors.lastname: Serimaa
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry*; D002473:Cell Wall / Q000378:metabolism*; D052196:Levilactobacillus brevis / Q000378:metabolism*; D008081:Liposomes; D053838:Scattering, Small Angle; D013499:Surface Properties; D014961:X-Ray Diffraction
chemical_list: D001426:Bacterial Proteins; D008081:Liposomes; C070683:surface layer protein A, Bacteria
keywords: Lactobacillus brevis; Liposomes; S-layer; SAXS