%0 Journal Article
%T The S-Layer Glycome¡ªAdding to the Sugar Coat of Bacteria
%A Robin Ristl
%A Kerstin Steiner
%A Kristof Zarschler
%A Sonja Zayni
%A Paul Messner
%A Christina Sch£¿ffer
%J International Journal of Microbiology
%D 2011
%I Hindawi Publishing Corporation
%R 10.1155/2011/127870
%X The amazing repertoire of glycoconjugates present on bacterial cell surfaces includes lipopolysaccharides, capsular polysaccharides, lipooligosaccharides, exopolysaccharides, and glycoproteins. While the former are constituents of Gram-negative cells, we review here the cell surface S-layer glycoproteins of Gram-positive bacteria. S-layer glycoproteins have the unique feature of self-assembling into 2D lattices providing a display matrix for glycans with periodicity at the nanometer scale. Typically, bacterial S-layer glycans are O-glycosidically linked to serine, threonine, or tyrosine residues, and they rely on a much wider variety of constituents, glycosidic linkage types, and structures than their eukaryotic counterparts. As the S-layer glycome of several bacteria is unravelling, a picture of how S-layer glycoproteins are biosynthesized is evolving. X-ray crystallography experiments allowed first insights into the catalysis mechanism of selected enzymes. In the future, it will be exciting to fully exploit the S-layer glycome for glycoengineering purposes and to link it to the bacterial interactome. 1. Introduction 1.1. The Sweet Cell Surface of Bacteria at a Glance Nature has equipped prokaryotic organisms from almost all phylogenetic branches with an amazing repertoire of components from its glycodiversification tool box, adding to the ¡°sweetness¡± of their cell surface. The ¡°sweetness¡± is derived from different kinds of polysaccharides, such as capsules or exopolysaccharides as well as glycoconjugates, such as lipopolysaccharides, lipooligosaccharides, and glycoproteins, all of which may additionally carry noncarbohydrate modifications. The complex type of biosynthesis of these prokaryotic carbohydrate components is truly amazing, and despite the tremendous progress in molecular biology it is still very difficult to see at present how the sequence of enzymatic reactions involved in the controlled biosynthesis of carbohydrate chains is regulated. Thus, it is reasonable to believe that the cellular sugar coat serves an important biological function. Prokaryotic glycoconjugates derive most of their structural diversity from the identities of their unusual sugar moieties. The addition of sugars to a nonglycosylated biomolecule changes its size and shape and this is likely to affect the access of proteolytic enzymes. Further, it will influence factors such as solubility, heat stability as well as many physical and chemical properties. Based on these properties, cell surface glycosylation may protect the prokaryotic cell from desiccation and other
%U http://www.hindawi.com/journals/ijmicro/2011/127870/