Figure 1
Predicted NOD ligands generated from processing/recycling of Wolbachia lipid II.
Cytoplasmatic enzymes necessary to produce the peptidoglycan (PG) precursor lipid II are conserved in Wolbachia (green ellipses). A2pm is the only amino acid synthesized de novo61 and it is expected that A2pm is at position three of the peptide chain. MurD and MurE synthesize the NOD ligands UDP-MurNAc-Dipeptide and UDP-MurNAc-Tripeptide, respectively63. In the periplasm, Wolbachia possess only two penicillin binding proteins (PBPs), a monofunctional transpeptidase and a D-alanyl-D-alanine carboxypeptidase (Wolbachia of Drosophila melanogaster also encode a monofunctional transpeptidase) that could process the pentapeptide chain61,64. Transglycosylases and endopeptidases (red X) are absent; therefore “classical” PG with crosslinked glycan chains is not predicted. NOD ligands (blue and orange circles) could arise during recycling or processing (question marks) of lipid II in the periplasmic space. Lightning bolts indicate canonical sites of cleavage in lipid II. MurNAc: N-acetyl-muramic acid, GlcNAc: N-acetyl-glucosamine, C55-P: undecaprenyl phosphate, L-Ala: L-Alanine, D-Glu: D-Glutamic acid, A2pm: diaminopimelic acid, D-Ala: D-Alanine, PBP: Penicillin-binding-protein. Adapted from33,36.
