Fig. 1. Structure of E. coli lipid A compared with the previously published structure of R. etli CE3 lipid A.
The backbone carbons are numbered on the assumption that the proximal aminogluconate moiety of R. etli lipid A is derived from a lipid A precursor common to both systems, such as Kdo2-lipid IVA, in which the proximal unit is not an aminogluconate moiety but glucosamine. The molecular weight of E. coli lipid A is 1798.8, whereas that of the previously proposed (33, 34) R. etli CE3 lipid A species shown above is predicted to be 2313.31.