Editing S-layer (section)

== Location of S-layers ==
[[File:TEM FE Sinense.png|thumb|upright=1.25|TEM micrograph of a freeze-etched and metal shadowed preparation of the archaeum ''Methanocorpusculum sinense''. The S-layer exhibits hexagonal (p6) lattice symmetry with a center-to-center spacing of approx. 16 nm. The rope like structure is a flagellum that has collapsed on the cell surface during cell centrifugation <ref name= "Pum1991" >{{cite journal | vauthors = Pum D, Messner P, Sleytr UB | date = 1991 | title = Role of the S layer in morphogenesis and cell division of the Archaebacterium ''Methanocorpusculum sinense'' | journal = J. Bacteriol. | volume = 173 | issue = 21 | pages = 6865–6873 | doi=10.1128/jb.173.21.6865-6873.1991| pmid = 1938891 | pmc = 209039 }}</ref> [https://creativecommons.org/licenses/by/4.0/ Creative Commons Attribution 4.0 International (CC BY 4.0) licence] [[File:CC-BY icon.svg|50px]].]]
[[File:CW-Architecture_2.png|thumb|upright=1.25|Schematic illustration of the supramolecular architecture of the major classes of prokaryotic cell envelopes containing surface (S) layers. S-layers in archaea with glycoprotein lattices as exclusive wall component are composed either of mushroom-like subunits with pillar-like, hydrophobic trans-membrane domains (a), or lipid-modified glycoprotein subunits (b). Individual S-layers can be composed of glycoproteins possessing both types of membrane anchoring mechanisms. Few archaea possess a rigid wall layer (e.g. pseudomurein in methanogenic organisms) as intermediate layer between the plasma membrane and the S-layer (c). In Gram-positive bacteria (d) the S-layer (glyco)proteins are bound to the rigid peptidoglycan-containing layer via secondary cell wall polymers. In Gram-negative bacteria (e) the S-layer is closely associated with the lipopolysaccharide of the outer membrane. Figure and figure legend were copied from Sleytr ''et al.'' 2025,<ref name="Sleytr2025" /> which is available under a [https://creativecommons.org/licenses/by/4.0/ Creative Commons Attribution 4.0 International (CC BY 4.0) licence] [[File:CC-BY icon.svg|50px]].]]
[[File: LatticeTypes natural 2.png|thumb| upright=1.25|Schematic drawing of the different S-layer lattice types. The proteins of one morphological unit are shown in red. For a more detailed description of the symmetry properties of S-layers see.<ref name= "Pum2021" >{{cite journal | vauthors = Pum D, Breitwieser A, Sleytr UB | date = 2021 | title = Patterns in Nature - S-Layer Lattices of Bacterial and Archaeal Cells | journal = Crystals | volume = 11 | issue = 8 | page = 869 | doi=10.3390/cryst11080869 |doi-access=free| bibcode = 2021Cryst..11..869P }}</ref> [https://creativecommons.org/licenses/by/4.0/ Creative Commons Attribution 4.0 International (CC BY 4.0) licence] [[File:CC-BY icon.svg|50px]].]]
* In [[Gram-negative]] [[bacteria]], S-layers are associated to the [[lipopolysaccharides]] via protein–carbohydrate interactions.<ref name="Sleytr2014" /><ref name="Sleytr2025" />
* In [[Gram-positive]] [[bacteria]] whose S-layers often contain surface layer homology (SLH) domains, the binding occurs to the [[peptidoglycan]] and to a secondary [[cell wall]] polymer (e.g., teichoic acids). In the absence of SLH domains, the binding occurs via electrostatic interactions between the positively charged N-terminus of the S-layer protein and a negatively charged secondary [[cell wall]] polymer. In Lactobacilli the binding domain may be located at the C-terminus.<ref name="Sleytr2014" />
* In [[Gram-negative]] [[archaea]], S-layer proteins possess a hydrophobic anchor that is associated with the underlying lipid membrane.<ref name="Albers2011" /><ref name="Sleytr2014" />
* In [[Gram-positive]] [[archaea]], the S-layer proteins bind to pseudomurein or to methanochondroitin.<ref name="Albers2011" /><ref name="Sleytr2014" />