Surface Layer Glycoproteins of Bacteria and Archaea

Prior to the designation of the archaebacteria (archaea) as a second prokaryotic kingdom of life (Woese and Fox, 1977), glycoproteins were believed to be restricted to the eukaryotes (for reviews see, Montreuil, 1995; Johansen et al., 1958). The observation of glycosylated cell envelope proteins of halobacteria has changed this perception (Mescher and Strominger, 1976a). Since then, an increasing number of reports have indicated the presence of glycoproteins in the domain archaea (Kandler, 1993, 1994). As a consequence, the occurrence of covalently linked glycan chains of bacterial proteins was regarded as a specific feature of archaebacteria (Mescher, 1981), constituting a significant difference to eubacteria. In the last decade, the presence of glycoproteins was also established in the domain bacteria. Thus, the ability of prokaryotic organisms to produce glycosylated proteins is not different in principle from that of higher organisms (Messner, 1996, 1997; Moens and Vanderleyden, 1997; Sumper and Wieland, 1995; Erickson and Herzberg, 1993; Messner and Sleytr, 1991; Lechner and Wieland, 1989). Glycosylation as an important secondary modification of proteins therefore exists in all domains of life (for a review, see Lis and Sharon, 1993). While the surface layer (S-layer) (for reviews, see Sleytr et al., 1996, 1999)