Novel bacterial lipoprotein structures conserved in low-GC content gram-positive bacteria are recognized by Toll-like receptor 2

J Biol Chem. 2012 Apr 13;287(16):13170-81. doi: 10.1074/jbc.M111.292235. Epub 2012 Feb 2.


Bacterial lipoproteins/lipopeptides inducing host innate immune responses are sensed by mammalian Toll-like receptor 2 (TLR2). These bacterial lipoproteins are structurally divided into two groups, diacylated or triacylated lipoproteins, by the absence or presence of an amide-linked fatty acid. The presence of diacylated lipoproteins has been predicted in low-GC content gram-positive bacteria and mycoplasmas based on the absence of one modification enzyme in their genomes; however, we recently determined triacylated structures in low-GC gram-positive Staphylococcus aureus, raising questions about the actual lipoprotein structure in other low-GC content gram-positive bacteria. Here, through intensive MS analyses, we identified a novel and unique bacterial lipoprotein structure containing an N-acyl-S-monoacyl-glyceryl-cysteine (named the lyso structure) from low-GC gram-positive Enterococcus faecalis, Bacillus cereus, Streptococcus sanguinis, and Lactobacillus bulgaricus. Two of the purified native lyso-form lipoproteins induced proinflammatory cytokine production from mice macrophages in a TLR2-dependent and TLR1-independent manner but with a different dependence on TLR6. Additionally, two other new lipoprotein structures were identified. One is the "N-acetyl" lipoprotein structure containing N-acetyl-S-diacyl-glyceryl-cysteine, which was found in five gram-positive bacteria, including Bacillus subtilis. The N-acetyl lipoproteins induced the proinflammatory cytokines through the TLR2/6 heterodimer. The other was identified in a mycoplasma strain and is an unusual diacyl lipoprotein structure containing two amino acids before the lipid-modified cysteine residue. Taken together, our results suggest the existence of novel TLR2-stimulating lyso and N-acetyl forms of lipoproteins that are conserved in low-GC content gram-positive bacteria and provide clear evidence for the presence of yet to be identified key enzymes involved in the bacterial lipoprotein biosynthesis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Bacillus cereus / immunology
  • Bacillus cereus / metabolism
  • Bacillus subtilis / immunology
  • Bacillus subtilis / metabolism
  • Enterococcus faecalis / immunology
  • Enterococcus faecalis / metabolism
  • Geobacillus / immunology
  • Geobacillus / metabolism
  • Gram-Positive Bacteria / immunology*
  • Gram-Positive Bacteria / metabolism
  • Lactobacillus / immunology
  • Lactobacillus / metabolism
  • Macrophages, Peritoneal / immunology*
  • Macrophages, Peritoneal / microbiology*
  • Mice
  • Mice, Inbred C57BL
  • Pneumonia, Mycoplasma / immunology
  • Pneumonia, Mycoplasma / metabolism
  • Streptococcus sanguis / immunology
  • Streptococcus sanguis / metabolism
  • Toll-Like Receptor 1 / genetics
  • Toll-Like Receptor 1 / immunology
  • Toll-Like Receptor 1 / metabolism
  • Toll-Like Receptor 2 / genetics
  • Toll-Like Receptor 2 / immunology*
  • Toll-Like Receptor 2 / metabolism*
  • Toll-Like Receptor 6 / genetics
  • Toll-Like Receptor 6 / immunology
  • Toll-Like Receptor 6 / metabolism


  • Tlr2 protein, mouse
  • Tlr6 protein, mouse
  • Toll-Like Receptor 1
  • Toll-Like Receptor 2
  • Toll-Like Receptor 6