title: Lipopolysaccharide interaction with S2 subunit of pertussis toxin.
abstract: Using radioiodinated, photoactivable, reducible cross-linker conjugated bacterial endotoxic lipopolysaccharide (125I-ASD-LPS), we have demonstrated that LPS selectively binds to the S2 subunit of pertussis toxin (PT). Since LPS also interacts with the S2 subunit of the B-oligomer of the toxin, the binding of LPS to PT is not A-protomer (S1 subunit) dependent. The binding can be inhibited with native underivatized LPS and with purified lipid A, suggesting that the binding is mediated through the lipid A moiety of the LPS molecule. The binding of PT to LPS can be inhibited by bovine fetuin glycoprotein. Since PT has been demonstrated to interact specifically with N-linked oligosaccharide side chains of fetuin, the interaction of LPS with the S2 subunit of PT may involve carbohydrate-dependent interactions of the disaccharide backbone of lipid A with S2. Additional studies have documented that LPS binding to PT may be competitively inhibited by lysozyme but not by polymyxin B. Sequence analysis has allowed identification of a high degree of amino acid sequence similarity between the S2 subunit of PT and hen egg white lysozyme at the N-terminal 80-residue regions. Shared N-terminal sequence similarity between lysozyme, PT-S2, and a third LPS-binding protein alpha-lactalbumin allows tentative identification of a second family of LPS binding proteins.
authors.affiliation: Department of Microbiology, Molecular Genetics, and Immunology, University of Kansas Medical Center, Kansas City 66160.
authors.forename: M G
authors.initials: MG
authors.lastname: Lei
authors.forename: D C
authors.initials: DC
authors.lastname: Morrison
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002645:Chickens; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000378:metabolism; D006801:Humans; D007457:Iodine Radioisotopes; D007768:Lactalbumin / Q000378:metabolism; D008050:Lipid A / Q000302:isolation & purification / Q000378:metabolism; D008070:Lipopolysaccharides / Q000302:isolation & purification / Q000378:metabolism*; D046911:Macromolecular Substances; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009113:Muramidase / Q000378:metabolism; D037342:Pertussis Toxin; D012475:Salmonella / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D010566:Virulence Factors, Bordetella / Q000302:isolation & purification / Q000378:metabolism*
chemical_list: D007457:Iodine Radioisotopes; D008050:Lipid A; D008070:Lipopolysaccharides; D046911:Macromolecular Substances; D010566:Virulence Factors, Bordetella; D007768:Lactalbumin; D037342:Pertussis Toxin; D009113:Muramidase