Figure 1.

Bacterial lipoproteins. (A) Structure of bacterial lipoproteins according to Braun and Wu (1994). The structure of synthetic lipopeptide Pam₃CSK₄ is also indicated. Triacylated bacterial lipoproteins and Pam₃CSK₄ have the same lipid moiety (green). R₁, R₂, and R₃ are fatty acyl chains. Adapted from Braun and Wu (1994) and Chambaud et al. (1999). (B) Biosynthesis of lipoproteins in Gram-negative and Gram-positive bacteria. After crossing the cytoplasmic membrane Lgt (prolipoprotein diacylglyceryl transferase) transfers a diacylglyceride to the polypeptide chain and Lsp (lipoprotein signal peptidase) cleaves the signal peptide. In Gram-negative bacteria Lnt (lipoprotein N-acyl transferase) adds a third fatty acyl chain as indicated in the text. Although triacylated lipoproteins have been described in S. aureus, the mechanism of lipoprotein N-acylation is not known. Furthermore, in Gram-negative bacteria, acylated lipoproteins are translocated to the outer membrane by the Lol system [Reviewed in Okuda and Tokuda (2011)].