FIGURE 1.
Lipoprotein modification pathway in E. coli. An unmodified prolipoprotein with a hydrophobic signal peptide (SP) containing the conserved lipobox sequence is first modified by the enzymes phosphatidylglycerol:prolipoprotein diacylglyceryl transferase (Lgt) and prolipoprotein signal peptidase (Lsp). This apolipoprotein is further modified by apolipoprotein N-acyltransferase (Lnt), which attacks the sn-1 acyl chain of a phospholipid, forms a thioester acyl-enzyme intermediate, and transfers the acyl group to the α-amino group of the diacylglyceryl-cysteine, leading to a mature triacylated lipoprotein. The acyl donor indicated is based on one of the major E. coli phospholipids, 1-palmitoyl-2-vaccenoyl-sn-glycero-3-phosphoethanolamine (16:0, cis-Δ11,12-18:1).