Are S-layer glycoproteins and lipopolysaccharides related?

Several glycan structures of S-layer glycoproteins of gram-positive eubacteria were compared with the principal structural organization of O-antigens of lipopolysaccharides of gram-negative eubacteria. Further, activated intermediates of the biosynthetic pathway of S-layer glycans were compared with activated intermediates of the route of assembly of lipopolysaccharide O-antigens. As a result, at least structural similarities between both types of molecules have been clearly observed. More detailed studies of the assembly of S-layer glycans are required to unambiguously demonstrate the extent to which the biosynthetic pathways of both molecules are related.