Microbial Surface Proteins: S-layers
S-layer functions appear to be diverse. In order to judge the functional significance of S-layers, it is helpful to distinguish between primary and secondary functions. One of the basic functions is to protect cells against mechanical and osmotic stress.
In archaea, S-layers are often the only cell wall structure and typically interact with the cell membrane via stalks that are inserted in the lipid (bi)layer. The S-layer imparts the cell mechanical stability and protects it against turgor and hypoosmotic impact. The stabilising effect can only be understood if the membrane-S-layer system is regarded as an integrated structure. Theoretical analyses suggest that small membrane bulges of S-layer unit cell size are formed upon internal osmotic pressure. These bulged membrane patches are much more stable than the naked membrane of (hypothetic) S-layer-less cells that will be dilated until leakages occur. It becomes evident and can be described in a simple formula that the S-layer geometry, i.e. the lattice constant and symmetry, is of functional significance.
rss
Top
Print