S‐Layers, Microbial, Biotechnological Applications

Abstract

Crystalline bacterial cell surface layers (S‐layers), a unique self‐assembly system optimized during billions of years of biological evolution, are one of the most commonly observed cell, envelope structures of prokaryotes. Although self‐assembly of molecules is an ubiquitous strategy of morphogenesis in nature, research in the area of molecular nanotechnology, nanobiotechnology, and biomimetics are only beginning to exploit its potential for the functionalization of surfaces and interfaces as well as for the production of biomimetic membranes and encapsulation systems. In this context, S‐layers fulfill key requirements for controlled assembly of supramolecular materials. As S‐layers are periodic structures, they exhibit identical physicochemical properties for each molecular unit down to the subnanometer level and possess pores of identical size and morphology. Many applications in nanobiotechnology depend on the ability of isolated native S‐layer proteins and S‐layer fusion proteins incorporating functional sequences to self‐assemble into monomolecular crystalline arrays in suspension, on a great variety of solid substrates, and on various lipid structures, including planar membranes and liposomes. S‐Layers have proven to be particularly suited as building blocks and patterning elements in a biomolecular construction kit involving all major classes of biological molecules enabling innovative approaches for the controlled ‘bottom‐up’ assembly of functional supramolecular structures and devices as required for life‐ and nonlife science applications.

S-layers: principles and applications

“…Most important, properties of S‐layer proteins can be changed by chemical modifications and genetic engineering. It is now evident that S‐layers also represent a unique structural basis and pattering element for generating complex supramolecular assemblies involving all relevant ‘building blocks’ such as proteins, lipids, glycans, and nucleic acids (Egelseer et al ., ; Schuster & Sleytr, ; Egelseer et al ., ; Sleytr et al ., ; Ilk et al ., ; Sleytr et al ., , ).…”

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

“…Studies on a great variety of S-layer proteins from Bacillaceae revealed the existence of specific binding domains on the N-terminal part for sugar polymers, the so-called SCWPs, which are covalently linked to the peptidoglycan of the cell wall [135]. These SCWPs mediate the oriented binding of S-layer proteins to the underlying cell wall.…”

The high‐molecular‐mass amylase (HMMA) of Geobacillus stearothermophilus ATCC 12980 interacts with the cell wall components by virtue of three specific binding regions

“…Even after isolation from the cell wall, S‐layer proteins frequently maintain the ability to self‐assemble in suspension or to re‐crystallize on peptidoglycan‐containing sacculi (PGS), at the air–water interface or on artificial solid supports and lipid films. Thus, S‐layers represent unique self‐assembly systems which can be used as a patterning element for many nanobiotechnological applications (Sleytr et al ., 2002; 2005; 2007a,b; 2009; Egelseer et al ., 2009).…”