Characterization of lipopolysaccharide fractions and their interactions with cells and model membranes.
The role of the length of the O-antigen polysaccharide side chain of bacterial lipopolysaccharide (LPS) in biological and model membrane systems was investigated. LPS from Salmonella typhimurium ATCC 14028 was chromatographed on a Sephadex G-200 column in the presence of sodium deoxycholate and separated into three fractions on the basis of molecular size. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis, Western blot (immunoblot), and chemical analyses indicated that these fractions differed from each other primarily in the number of repeating units in the O-antigen polysaccharide side chain. In a biological system fractions 2 and 3 had the same effects to induce mitogenesis in murine lymphocytes, but fraction 1 was less effective than the other two fractions. In a model membrane system, LPS induced changes in small unilamellar vesicles (SUVs) which were measured by changes in the behavior of a fluorescent probe, 1,6-diphenylhexa-1,3,5-triene (DPH), and interaction of increasing amounts of all LPS fractions with SUVs gradually increased DPH anisotropy. Fractions 2 and 3 had similar effects on the SUVs as detected by changes in DPH anisotropy, while fraction 1 had almost twice as much activity as the other two fractions. These results suggest that the polysaccharide side chain of LPS may modulate the ability of biologically active lipid A to interact with cells and model membranes. In addition, factors other than changes in membrane fluidity may play a role in mediating LPS-induced cell activation.
Department of Microbiology, School of Medicine and Biomedical Sciences, State University of New York, Buffalo 14214.
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D000818:Animals; D016880:Anisotropy; D000942:Antigens, Bacterial / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism; D005456:Fluorescent Dyes; D008070:Lipopolysaccharides / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism; D008213:Lymphocyte Activation / Q000502:physiology; D008567:Membranes, Artificial; D051379:Mice; D008934:Mitogens / Q000302:isolation & purification / Q000378:metabolism; D019081:O Antigens; D012486:Salmonella typhimurium / Q000737:chemistry*
D000942:Antigens, Bacterial; D005456:Fluorescent Dyes; D008070:Lipopolysaccharides; D008567:Membranes, Artificial; D008934:Mitogens; D019081:O Antigens