Figure 1.

Biosynthetic reactions targeted during the construction of E. coli strains KPM318 and KPM404. The late acyltransferases LpxL and LpxM of the constitutive pathway transfer laurate and myristate, respectively, to Kdo₂-lipid IV_A to form the characteristic acyloxyacyl units of hexaacylated Kdo₂-lipid A. In contrast, LpxP, PagP and EptA are regulated in response to certain stimuli such as incorporation of palmitoleate in place of laurate by LpxP at low growth temperatures or PagP-catalyzed palmitoylation of lipid A upon phospholipid translocation to the outer leaflet of the outer membrane, for example, in strains defective in LPS biosynthesis. The acyl-acyl carrier protein (ACP) serves as the preferred acyl donor for various lipid A-acyltransferases.