* Nas arqueas [[Gram-positiva]]s, as proteínas da capa S únense á [[pseudomureína]] ou á metanocondroitina.
Biological functions of the S -layer ==
For many bacteria, the S-layer represents the outermost interaction zone with their respective environment. Its functions are very diverse and vary from species to species.
In Archaea the S-layer is the only cell wall component and, therefore, is important for mechanical stabilization. Additional functions associated with S-layers include:
protection against [[ bacteriophages]], [[Bdellovibrio]]s, and [[ phagocytosis]]
resistance against low [[pH]]
* barrier against high-molecular-weight substances (e.g., lytic [[enzymes]])
* adhesion (for [[glycosylated]] S-layers)
* stabilisation of the membrane
* provision of adhesion sites for exoproteins
* provision of a periplasmic compartment in Gram-positive prokaryotes together with the peptidoglycan and the cytoplasmic membranes