Figure 6.

Modifications to the structure of lipid A. Shown are modifications made to lipid A described in the text, alongside the enzymes that mediate them in corresponding colors. (A) Modifications made to the glucosamine phosphates. While shown in their preferred positions, it is possible for either phosphate to be modified with either substituent. (B) Modifications made to the acyl groups. The X indicated for LpxO is a hydroxyl (-OH) when LpxO is active, and a hydrogen (-H) when it is not. When acyl chains are removed, the cleaved bond is shown as a dotted line. It is important to note that LpxP is part of the conserved Raetz pathway but only active at low temperatures, at which LpxP substitutes for LpxL to add a C16:1 palmitoleoyl group instead of a lauroyl group.