S-Layer Reconstitution at Phospholipid Monolayers

Abstract

The recrystallization of the S-layer protein from Bacillus coagulans E38-66 at different lipid surface monolayer films has been observed to depend on (i) the nature of the lipid headgroup, (ii) the phase state of the surface monolayer, (iii) the ionic content, and (iv) the pH of the subphase. S-layer lattices formed at such interfaces were studied by electron microscopy and their orientation with respect to the lipid films was determined from the handedness of the base vectors defining the oblique crystal lattice. Recrystallization of S-layer lattices that cover the entire sample area was generally observed at lipids with zwitterionic headgroups in the presence of Ca2+ if the lipid chains possessed a high degree of order, i.e., if the lipid film was in the liquid condensed phase. Under such conditions, the S-layer was found to be attached to the lipid with its net negatively charged inner face. In contrast, the S-layer protein recrystallized poorly under most lipids with negatively charged headgroups and under lipids with unsaturated chains. At monolayers of cationic lipids, reconstituted S-layers were observed in which the protein was attached to the lipid with its outer face.

Heterologous expression of the surface-layer-like protein SllB induces the formation of long filaments of Escherichia coli consisting of protein-stabilized outer membrane

“…In addition, TEM images have revealed an extremely bloated periplasm containing layers, possibly of membranous origin, to which the S-layer proteins were attached. There are several reports describing the interaction of Slayer proteins with lipid membranes (Schuster et al, 2008;Wetzer et al, 1998;Weygand et al, 1999) and lipidic vesicles can be stabilized by coating with S-layer proteins (Schuster et al, 2008). In the context of the high resistance of the tubes against SDS, guanidine hydrochloride, urea and ultrasonic treatment, the above-mentioned work supports the theory that the S-layer protein has a stabilizing effect on the excessively produced outermembrane-like structures in the filaments of the sllBexpressing E. coli strain formed in the early growth phase.…”

Biomimetic interfaces based on S-layer proteins, lipid membranes and functional biomolecules

“…Formation of S-layer lattices covering the entire area of lipid films has been observed on zwitterionic phospholipids like PCs and in particular PEs [122]. S-layer proteins did not form crystalline lattices on negatively charged phospholipids.…”

“…Electrostatic interaction is thought to exist between exposed carboxyl groups on the S-layer lattice and zwitterionic lipid head groups. At least two or three contact points between the S-layer protein and the attached lipid film have been identified [122]. Hence, less than 5% of the lipid molecules of the adjacent monolayer are anchored to these contact points (protein domains) on the S-layer protein whereas the remaining 95% or more of lipid molecules may diffuse freely within the membrane between the pillars consisting of anchored lipid molecules [120,187].…”

Biomimetic S-Layer Supported Lipid Membranes

“…[36], Copyright (2004), with permission from Wiley-VCH. One of the most important properties of S-layer proteins lies in their capability to reassemble into crystalline arrays in suspension [22,50], at interfaces such as porous or solid supports [51][52][53], the air-water interface [40,54], planar lipid films [40,[54][55][56][57][58] (Fig. (3)), on liposomes [59][60][61], and on nanocapsules composed of polyelectrolytes [62].…”

“…From this observation it has been concluded that electrostatic interactions between exposed carboxyl groups on the inner face of the S-layer lattice and the zwitterionic lipid head groups are primarily responsible for the defined orientation of the subunits. For such an alignment, it has been suggested that there are at least two to three contact points between the lipid film and the attached S-layer protein [55]. Thus, less than 5% of the lipid molecules of the adjacent monolayer are anchored to functional domains on the S-layer protein whereas the remaining ≥ 95% lipid molecules diffuse freely in the membrane between the pillars consisting of anchored lipid molecules (Fig.…”