Crystalline Bacterial Cell-Surface Layers

Abstract

Publisher Summary Prokaryotic cells have developed different ways to present their surfaces to the environment. One of the most remarkable features of many Gram-positive and Gram-negative eubacteria and archaebacteria is the presence of a regularly ordered protein or glycoprotein layer as the outermost component of the cell envelope, called the surface layer (S-layer). They are composed of a single molecular species, protein or glycoprotein in nature, and are endowed with the ability to assemble into 2D crystalline arrays by an entropy-driven process. S-layers possess a high degree of structural regularity, and thus they are the most abundant of all bacterial cellular proteins, they are ideal model systems for studying the dynamic process of assembly of a supramolecular structure during cell growth. S-Layers are the simplest biological protein membranes developed during evolution. The information encoded in a single S-layer protein species guarantees maintenance of a closed, highly ordered porous protein meshwork on a growing cell surface. Surface layers are an integral part of the cell envelope of a great variety of archaebacteria and eubacteria. Because of their surface location, it is evident that functions have evolved as the result of specific interactions with particular environmental and ecological conditions. Due to the increased knowledge of the structure, assembly, chemistry, biosynthesis, pathogenicity and permeability properties of S-layers, a considerable potential for various biotechnological and non-biological applications for 2D crystals have become evident in few years.