Peptidoglycan and lipopolysaccharide bind to the same binding site on lymphocytes

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Abstract

Bacterial cell wall peptidoglycan (PGN) and lipopolysaccharide (LPS), which are both macrophage activators and polyclonal B cell mitogens, were shown to bind to the same dominant 70-kDa 6.5 pI protein on the surface of mouse B lymphocytes. This conclusion was supported by the following results: (a) the PGN-and LPS-binding proteins co-migrated following photoaffinity cross-linking and two-dimensional polyacrylamide gel electrophoresis; (b) cross-linking of PGN to this 70-kDa protein was competitively inhibited by LPS (IC50 = 7.3 μM), LPS from a deep rough mutant (IC50 = 6.9 μM), and lipid A (IC50 = 18-72 μM); (c) cross-linking of LPS to this 70-kDa protein was competitively inhibited by polymeric soluble PGN (IC50 = 0.09 μM) and sonicated high Mr PGN (IC50 = 0.6 μM); (d) cross-linking of both PGN and LPS to this 70-kDa protein was also competitively inhibited by dextran sulfate (IC50 = 115-124 μM); (e) cross-linking of both PGN and LPS to this 70-kDa protein was inhibited by a (GlcNAc)2-specific lectin; and (f) peptide maps of the 70-kDa proteins digested with chymotrypsin, subtilisin, staphylococcal protease V, or papain were identical for PGN- and LPS-binding proteins and unique for each enzyme. Based on competitive inhibition experiments, binding of PGN to the 70-kDa protein was 20-1200 times stronger than the binding of LPS or lipid A on a per mol basis. However, when aggregated micellar structures of LPS or lipid A were considered, the avidities of LPS and PGN binding were similar. These results demonstrate binding of PGN and LPS to the same 70-kDa protein on lymphocytes and suggest that the binding is specific for the (GlcNAc-MurNAc)n backbone of PGN and the (GlcNAc)2 part of lipid A.

Original languageEnglish (US)
Pages (from-to)4719-4725
Number of pages7
JournalJournal of Biological Chemistry
Volume266
Issue number8
StatePublished - Jul 11 1991

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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