FIGURE 11.

Topography of the active sites of LpxE and other lipid A modification enzymes in R. etli and R. leguminosarum. The structure of the conserved intermediate Kdo₂-lipid IV_A is shown in Fig. 2. The evidence for the existence and orientation of these enzymes and transporters is reviewed elsewhere (2). The color scheme is as follows: glucosamine, blue; Kdo, white; galacturonic acid, cyan; aminogluconate, magenta; phosphate groups, red; fatty acyl chains, green; enzymes, red letters; proposed transport proteins, black letters. The active sites of both LpxE (the 1-phosphatase) and LpxF (the 4′-phosphatase) face the periplasm, preventing premature dephosphorylation of key precursors such as lipid IV_A.