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9.B.324.  The Pore-forming S-layer protein (S-layer) Family 

Crystalline bacterial and archaeal cell surface layers (S-layers) represent the outermost cell envelope component in a broad range of bacteria and archaea (Pum and Sleytr 2014). They are monomolecular arrays composed of a single protein or glycoprotein species and represent the simplest proteinaceous biological membranes. They are highly porous protein mesh works with unit cell sizes in the range of 3 to 30 nm, and pore sizes of 2 to 8 nm. S-layers are usually 5 to 20 nm thick in bacteria but up to 70 nmthick in archaea. S-layer proteins are one of the most abundant biopolymers on earth. One of their key features,  is the intrinsic capability of isolated native and recombinant S-layer proteins to form self-assembled mono- or double layers in suspension, at solid supports, the air-water interface, planar lipid films, liposomes, nanocapsules, and nanoparticles. Reassembly is entropy-driven as an example of matrix assembly following a multistage pathway in which the process of S-layer protein folding is directly linked with assembly into extended clusters. Basic research on the structure, synthesis, genetics, assembly, and function of S-layer proteins laid the foundation for their application in novel approaches in biotechnology, biomimetics, synthetic biology, and nanotechnology (Pum and Sleytr 2014).

References associated with 9.B.324 family:

Konrad, Z. and J. Eichler. (2002). Lipid modification of proteins in Archaea: attachment of a mevalonic acid-based lipid moiety to the surface-layer glycoprotein of Haloferax volcanii follows protein translocation. Biochem. J. 366: 959-964. 12069685
Kontro, I., S.K. Wiedmer, U. Hynönen, P.A. Penttilä, A. Palva, and R. Serimaa. (2014). The structure of Lactobacillus brevis surface layer reassembled on liposomes differs from native structure as revealed by SAXS. Biochim. Biophys. Acta. 1838: 2099-2104. 24796504
Pum, D. and U.B. Sleytr. (2014). Reassembly of S-layer proteins. Nanotechnology 25: 312001. 25030207
Shalev, Y., I. Turgeman-Grott, A. Tamir, J. Eichler, and U. Gophna. (2017). Cell Surface Glycosylation Is Required for Efficient Mating of. Front Microbiol 8: 1253. 28725221
Trachtenberg, S., B. Pinnick, and M. Kessel. (2000). The cell surface glycoprotein layer of the extreme halophile Halobacterium salinarum and its relation to Haloferax volcanii: cryo-electron tomography of freeze-substituted cells and projection studies of negatively stained envelopes. J Struct Biol 130: 10-26. 10806087