S-layers: principles and applications

Abstract

Monomolecular arrays of protein or glycoprotein subunits forming surface layers (S-layers) are one of the most commonly observed prokaryotic cell envelope components. S-layers are generally the most abundantly expressed proteins, have been observed in species of nearly every taxonomical group of walled bacteria, and represent an almost universal feature of archaeal envelopes. The isoporous lattices completely covering the cell surface provide organisms with various selection advantages including functioning as protective coats, molecular sieves and ion traps, as structures involved in surface recognition and cell adhesion, and as antifouling layers. S-layers are also identified to contribute to virulence when present as a structural component of pathogens. In Archaea, most of which possess S-layers as exclusive wall component, they are involved in determining cell shape and cell division. Studies on structure, chemistry, genetics, assembly, function, and evolutionary relationship of S-layers revealed considerable application potential in (nano)biotechnology, biomimetics, biomedicine, and synthetic biology.

Harnessing the power of microbial nanowires

“…The geometric assembly of proteins leads, for example, to the formation of molecular nanomachines and hyperstructures such as the ATP synthase complex and the cytoskeletal microtubules respectively (Alfaro‐Aco and Petry, 2015; Ruhle and Leister, 2015). Proteins can also self‐assemble in planar geometric configurations to make the S‐layer lattices of some bacteria and archaea (Sleytr et al ., 2014) and into distinctive 3D geometries such as bacterial intracellular microcompartments and viral capsids (Uetrecht et al ., 2011; Sutter et al ., 2017). These natural designs have inspired the synthesis of novel nanomaterials and protocols for protein functionalization and controlled association that modulate the material's properties and enable new functions (Yang et al ., 2016).…”

Kinetics of Surface-Driven Self-Assembly and Fatigue-Induced Disassembly of a Virus-Based Nanocoating

“…However, only a few protein assemblies form lattices indefinitely extended along two dimensions (2D). Examples of natural self-assembling protein sheets include S-layers of archea and many bacteria (12) and hydrophobin coatings of many fungi (13,14). In addition, self-assembling 2D lattices have been created by engineering other proteins (15)(16)(17)(18).…”

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

“…At the same time, new methods have been used to improve the durability of lipid membranes, with shelf-lives now reaching the order of weeks. The capabilities of supported lipid membranes have opened the door to biotechnology applications in medicine, diagnostics, sensor systems, environmental monitoring and energy storage [3][4][5].…”

“…This review is focused on the biomimetic approach of applying the building principle of cell envelope structure for the generation of a versatile biological unit-a protein-supported lipid membrane. The used protein species, termed S-layers (S-is the abbreviation of 'surface'), are defined as 'two-dimensional arrays of proteinaceous subunits forming surface layers on prokaryotic cells' [5,7,8] and are found as the outermost structure in hundreds of different species of almost every taxonomic group of walled bacteria (figure 1) and are an almost universal feature of archaea [4,[9][10][11][12]. Interestingly, many bacterial and most archaeal S-layer proteins are glycosylated [13][14][15].…”

“…In Gram-negative bacteria (e) the S-layer is closely associated with the lipopolysaccharide of the outer membrane. (Adapted from [5].…”