title: Physicochemical characterization of the endotoxins from Coxiella burnetii strain Priscilla in relation to their bioactivities.
abstract: BACKGROUND
  Coxiella burnetii is the etiological agent of Q fever found worldwide. The microorganism has like other Gram-negative bacteria a lipopolysaccharide (LPS, endotoxin) in its outer membrane, which is important for the pathogenicity of the bacteria. In order to understand the biological activity of LPS, a detailed physico-chemical analysis of LPS is of utmost importance.
  
  
  RESULTS
  The lipid A moiety of LPS is tetraacylated and has longer (C-16) acyl chains than most other lipid A from enterobacterial strains. The two ester-linked 3-OH fatty acids found in the latter are lacking. The acyl chains of the C. burnetii endotoxins exhibit a broad melting range between 5 and 25 degrees C for LPS and 10 and 40 degrees C for lipid A. The lipid A moiety has a cubic inverted aggregate structure, and the inclination angle of the D-glucosamine disaccharide backbone plane of the lipid A part with respect to the membrane normal is around 40 degrees. Furthermore, the endotoxins readily intercalate into phospholipid liposomes mediated by the lipopolysaccharide-binding protein (LBP). The endotoxin-induced tumor necrosis factor alpha (TNFalpha) production in human mononuclear cells is one order of magnitude lower than that found for endotoxins from enterobacterial strains, whereas the same activity as in the latter compounds is found in the clotting reaction of the Limulus amebocyte lysate assay.
  
  
  CONCLUSIONS
  Despite a considerably different chemical primary structure of the C. burnetii lipid A in comparison with enterobacterial lipid A, the data can be well understood by applying the previously presented conformational concept of endotoxicity, a conical shape of the lipid A moiety of LPS and a sufficiently high inclination of the sugar backbone plane with respect to the membrane plane. Importantly, the role of the acyl chain fluidity in modulating endotoxicity now becomes more evident.
authors.affiliation: Institute of Virology, Slovak Academy of Sciences, Dubravska cesta 9, 84245 Bratislava, Slovak Republic. virutoma@savba.sk
authors.forename: Rudolf
authors.initials: R
authors.lastname: Toman
authors.forename: Patrick
authors.initials: P
authors.lastname: Garidel
authors.forename: Jörg
authors.initials: J
authors.lastname: Andrä
authors.forename: Katarina
authors.initials: K
authors.lastname: Slaba
authors.forename: Ahmed
authors.initials: A
authors.lastname: Hussein
authors.forename: Michel H J
authors.initials: MH
authors.lastname: Koch
authors.forename: Klaus
authors.initials: K
authors.lastname: Brandenburg
mesh_terms: D002849:Chromatography, Gas; D003381:Coxiella / Q000737:chemistry*; D004187:Disaccharides / Q000737:chemistry; D004305:Dose-Response Relationship, Drug; D004731:Endotoxins / Q000737:chemistry* / Q000494:pharmacology; D005227:Fatty Acids / Q000032:analysis; D008401:Gas Chromatography-Mass Spectrometry; D005944:Glucosamine / Q000737:chemistry; D006801:Humans; D007963:Leukocytes, Mononuclear / Q000187:drug effects / Q000378:metabolism; D008050:Lipid A / Q000737:chemistry / Q000494:pharmacology; D008070:Lipopolysaccharides / Q000737:chemistry / Q000494:pharmacology; D008081:Liposomes / Q000737:chemistry; D008968:Molecular Conformation; D044367:Phase Transition; D012475:Salmonella / Q000737:chemistry; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013329:Structure-Activity Relationship; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis; D014961:X-Ray Diffraction
chemical_list: D004187:Disaccharides; D004731:Endotoxins; D005227:Fatty Acids; D008050:Lipid A; D008070:Lipopolysaccharides; D008081:Liposomes; D014409:Tumor Necrosis Factor-alpha; D005944:Glucosamine