The structure of bacterial S-layer proteins.

S-layers are self-assembled paracrystalline protein lattices that cover many bacteria and almost all archaea. As an important component of the bacterial cell envelope, S-layers can fulfill various biological functions and are usually the most abundantly expressed protein species in a cell. Here we review the structures of the best characterized S-layer proteins from Gram-positive and Gram-negative bacteria, as well as methods to determine their molecular architecture.