scholarly journals Bacterial Peptidoglycan-associated Lipoprotein Is Released into the Bloodstream in Gram-negative Sepsis and Causes Inflammation and Death in Mice

2002 ◽  
Vol 277 (16) ◽  
pp. 14274-14280 ◽  
Author(s):  
Judith Hellman ◽  
Jesse D. Roberts ◽  
Megan M. Tehan ◽  
Jennifer E. Allaire ◽  
H. Shaw Warren
Keyword(s):  
Gram Negative ◽  
Bacterial Peptidoglycan

scholarly journals Cleavage of Braun’s lipoprotein Lpp from the bacterial peptidoglycan by a paralog of l,d-transpeptidases, LdtF

2021 ◽  
Vol 118 (19) ◽  
pp. e2101989118
Author(s):  
Raj Bahadur ◽  
Pavan Kumar Chodisetti ◽  
Manjula Reddy
Keyword(s):  
Bacterial Cell ◽  
Structural Integrity ◽  
Cell Envelope ◽  
Hydrolytic Enzyme ◽  
Gram Negative ◽  
E Coli ◽  
Bacterial Cell Envelope ◽  
Cross Links ◽  
Bacterial Peptidoglycan ◽  
Elastic Polymer

The gram‐negative bacterial cell envelope is made up of an outer membrane (OM), an inner membrane (IM) that surrounds the cytoplasm, and a periplasmic space between the two membranes containing peptidoglycan (PG or murein). PG is an elastic polymer that forms a mesh-like sacculus around the IM, protecting cells from turgor and environmental stress conditions. In several bacteria, including Escherichia coli, the OM is tethered to PG by an abundant OM lipoprotein, Lpp (or Braun’s lipoprotein), that functions to maintain the structural and functional integrity of the cell envelope. Since its discovery, Lpp has been studied extensively, and although l,d-transpeptidases, the enzymes that catalyze the formation of PG−Lpp linkages, have been earlier identified, it is not known how these linkages are modulated. Here, using genetic and biochemical approaches, we show that LdtF (formerly yafK), a newly identified paralog of l,d-transpeptidases in E. coli, is a murein hydrolytic enzyme that catalyzes cleavage of Lpp from the PG sacculus. LdtF also exhibits glycine-specific carboxypeptidase activity on muropeptides containing a terminal glycine residue. LdtF was earlier presumed to be an l,d-transpeptidase; however, our results show that it is indeed an l,d-endopeptidase that hydrolyzes the products generated by the l,d-transpeptidases. To summarize, this study describes the discovery of a murein endopeptidase with a hitherto unknown catalytic specificity that removes the PG−Lpp cross-links, suggesting a role for LdtF in the regulation of PG–OM linkages to maintain the structural integrity of the bacterial cell envelope.

scholarly journals The Frameshift Mutation in Nod2 Results in Unresponsiveness Not Only to Nod2- but Also Nod1-activating Peptidoglycan Agonists

2005 ◽  
Vol 280 (43) ◽  
pp. 35859-35867 ◽  
Author(s):  
Mihai G. Netea ◽  
Gerben Ferwerda ◽  
Dirk J. de Jong ◽  
Catherine Werts ◽  
Ivo G. Boneca ◽  
...  
Keyword(s):  
Crohn Disease ◽  
Frameshift Mutation ◽  
Susceptibility Gene ◽  
Muramyl Dipeptide ◽  
Protein S ◽  
Diaminopimelic Acid ◽  
Gram Negative ◽  
Peptidoglycan Recognition Protein ◽  
Recognition Protein ◽  
Bacterial Peptidoglycan

NOD2/CARD15 is the first characterized susceptibility gene in Crohn disease. The Nod2 1007fs (Nod2fs) frameshift mutation is the most prevalent in Crohn disease patients. Muramyl dipeptide from bacterial peptidoglycan is the minimal motif detected by Nod2 but not by Nod2fs. Here we investigated the response of human peripheral blood mononuclear cells (PBMCs) from Crohn disease patients not only to muramyl dipeptide but also to several other muramyl peptides. Most unexpectedly, we observed that patients homozygous for the Nod2fs mutation were totally unresponsive to MurNAc-l-Ala-d-Glu-meso-diaminopimelic acid (DAP) (M-TriDAP), the specific agonist of Nod1, and to Gram-negative bacterial peptidoglycan. In contrast, PBMCs from a patient homozygous for the Nod2 R702W mutation, also associated with Crohn disease, displayed normal response to Gram-negative bacterial peptidoglycan. In addition, the blockage of the Nod1/M-TriDAP pathway could be partially overcome by co-stimulation with the Toll-like receptors agonists lipoteichoic acid or lipopolysaccharide. Investigation into the mechanism of this finding revealed that Nod2fs did not act as a dominant-negative molecule for the Nod1/M-TriDAP pathway, implying that the blockage is dependent upon the expression or activity of other factors. We demonstrated that PBMCs from Nod2fs patients express high levels of the peptidoglycan recognition protein S, a secreted protein known to interact with muramyl peptides. We proposed that through a scavenger function, peptidoglycan recognition protein S may dampen M-TriDAP-dependent responses in Nod2fs patients. Together, our results identified a cross-talk between the Nod1 and Nod2 pathways and suggested that down-regulation of Nod1/M-TriDAP pathway may be associated with Crohn disease.

scholarly journals Characterization of a Monoclonal Antibody That Binds to an Epitope on Soluble Bacterial Peptidoglycan Fragments

2001 ◽  
Vol 8 (3) ◽  
pp. 647-651 ◽  
Author(s):  
Glenn J. Merkel ◽  
Barbara A. Scofield
Keyword(s):  
Staphylococcus Aureus ◽  
Monoclonal Antibody ◽  
Immunosorbent Assay ◽  
Enzymatic Digestion ◽  
Immunoglobulin M ◽  
Enzyme Linked Immunosorbent Assay ◽  
Gram Negative Bacteria ◽  
Gram Negative ◽  
Bacterial Peptidoglycan

ABSTRACT We employed an inhibition-type enzyme-linked immunosorbent assay (ELISA) to characterize a murine immunoglobulin M monoclonal antibody (MAb) that bound soluble macromolecular peptidoglycan (PG). With this ELISA, the MAb was capable of detecting soluble PG concentrations of less than 10 ng/ml. Enzymatic digestion of PG reduced binding by more than 100-fold, implying that the epitope recognized by this antibody depended on repeating subunits within the glycan backbone. Additionally, the MAb bound to epitopes on both O-acetylated and non-O-acetylated PG fragments from gram-negative bacteria, as well as PG fragments from Staphylococcus aureus and PG fragments released into the medium by a number of gram-positive and gram-negative bacteria.

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