Bacterial and archaeal S-layers as a subject of nanobiotechnology

Many bacteria and archaea have a crystalline surface layer (S-layer), which overlies the cell envelope. S-layers each consist of one protein or glycoprotein species. Protein subunits of the S-layer noncovalently interact with each other and with the underlying cell-envelope component. On average, the S-layer lattice has pores of 2-6 nm and is 5-10 nm high. Isolated S-layer proteins recrystallize to form two-dimensional crystalline structures in solution, on a solid support, and on planar lipid membranes. Owing to this unique property, S-layers; have a broad range of applications. This review focuses on the structural features and applications of S-layers; and their proteins, with special emphasis on their use in nanobiotechnology.