Prokaryotic glycosylation

With the advances of molecular biology and with improved analytical techniq ues a significant change of perception has taken place regarding prokaryoti c glycoproteins. Glycosylation of proteins from prokaryotes is no longer co nsidered a specific feature of certain organisms but has been demonstrated for many archaea and bacteria. Besides the occurrence of glycosylated enzym es, antigens and other cell envelope components, surface layer (S-layer) gl ycoproteins represent the best-studied examples of glycosylated prokaryotic proteins. They are widely distributed among archaeal wildtype strains, but among bacteria they have been mainly observed with Gram-positive organisms . There is, in general, an enormous increase of reports on the presence of glycosylated proteins among prokaryotes. For their isolation and characteri zation a great number of methods are available, aiming at the identificatio n of the covalent linkage between the carbohydrate and the polypeptide port ion. So far, several differences in structure and biosynthesis have been ob served in comparison to eukaryotic glycoproteins. In this review we introdu ce a protocol which has been successfully applied to the investigation of t he complex structures, linkage units, and polypeptide consensus sequences o f glycosylated bacterial S-layer proteins.