Fig. 1. Comparison of E. coli lipid A, L. interrogans lipid A, and 1-phosphomethyl-lipid A from E. coli expressing LmtA.

Four key differences in the structures of E. coli (A) and L. interrogans (B) lipid A are the presence in the latter of four N-linked acyl chains instead of two, two unsaturated secondary acyl chains, a methylated 1-phosphate group, and the absence of the 4′-phosphate moiety. The structure of 1-phosphomethyl-lipid A from E. coli expressing LmtA is shown in C.