Analysis of Bacterial Glycoproteins

Abstract

Investigation of bacterial glycoproteins is a relatively new field. Although biochemical research of glycoproteins was and is being focused on mammalian systems, only a few protein-linked bacterial carbohydrates have been solved so far. Since the bacterial structures described are not related closely enough to established structures, every bacterial carbohydrate analysis presents an adventurous challenge per se. Nevertheless, the monosaccharide composition of bacterial glycoproteins is not different from that of mammalian glyocoproteins in principal, although a few rare sugars are found in addition, e.g., 3-O-methylgalactosuronic acid, 3-O-methylglucose, and furanosidic galactose (1–3). These monosaccharides together with the more common ones are composed to yield various types of oligosaccharides, which are linked to the core protein via O- and N-glycosyl linkages. In Fig. 1, our present knowledge of the structure of the cell-surface glycoprotein from halobacteria is summarized. So far, two novel types of N-glycosyl linkages have been discovered in this bacterial cell-surface glycoprotein. Here we would like to outline a few selected methods that have made bacterial glycoconjugate analysis easier in our laboratory, and also describe a more general way that has led us to uncover the novel linkage units between carbohydrate and protein.