Fig. 2. Structure of Kdo2-lipid A in E. coli K-12 compared to phosphatidylethanolamine, the major membrane phospholipid. Lipid A is much more complex in structure than phosphatidylethanolamine. Lipid A is glucosamine-based, and contains no glycerol. The acyl chains are shorter, fully saturated and hydroxylated if attached to glucosamine. Both Kdo and lipid A are required for growth, possibly because they are required for outer membrane protein folding. An x-ray structure of LPS bound to the outer membrane protein FhuA has recently been solved (80). You need to select RasMol (under Viewer:) and All Atom Model (under Complexity: ) and then follow “more information” instructions to download the Chime Plug-In. Try to locate the LPS and its lipid A moiety.