The structures of core regions from enterobacterial lipopolysaccharides - an update.

To the major virulence factors of Gram-negative bacteria belong the lipopolysaccharides (endotoxins), which are very well characterized for their immunological, pharmacological and pathophysiological effects displayed in eucaryotic cells and organisms. In general, these amphiphilic lipopolysaccharides comprise three regions, which can be differentiated by their structures, function, genetics and biosynthesis: lipid A, the core region and a polysaccharide portion, which may be the O-specific polysaccharide, Enterobacterial Common Antigen (ECA) or a capsular polysaccharide. In the past, much emphasis has been laid on the elucidation of the structure-function relation. The lipid A was proven to represent the toxic principle of endotoxic active lipopolysaccharides, however, its toxicity depends not only on its structure but also on that of the core region, which is covalently linked to lipid A. Thus, and since the core region possesses immunogenic properties, complete structural analyses of lipopolysaccharides core regions and of structure-function relation are highly important for a better understanding of lipopolysaccharides action. To date, quite a number of core structures from lipopolysaccharides of various Gram-negative bacteria have been published and summarized in several overviews. This short review adds to this knowledge those structures of enterobacterial lipopolysaccharides that were published between January 2002 and October 2006.