Fig. 1.

Lipoprotein maturation and trafficking in E. coli. Steps 1–8 show a generic lipoprotein (LP) undergoing maturation and transport to the bacterial outer membrane (OM). Immature lipoprotein is secreted by the Sec system and integrated in the inner membrane (IM) (1). Lgt adds diacylglycerol to the lipobox cysteine residue (2). Lsp removes the transmembrane signal peptide (3). Lnt acylates the lipoprotein N terminus amino group (4). LolCDE transfers the mature (triacylated) lipoprotein to the LolA chaperone (5). Lipoprotein is passed from LolA to LolB by a mouth-to-mouth mechanism (6). LolA is recycled, leaving lipoprotein bound to LolB (7). LolB releases lipoprotein to the outer membrane (8).