The mycocidal, membrane-active complex of Cryptococcus humicola is a new type of cellobiose lipid with detergent features

AbstractThe chemical composition of the mycocidal complex (formerly known as microcin) secreted by Cryptococcus humicola was investigated by chemical, mass spectrometric and nuclear magnetic resonance methods. The results indicate that the mycocidal complex is composed of glycolipids with a highly acetylated (up to five acetyl groups) cellobiose backbone [β-D-Glcp-(1′→4)-β-D-Glcp] linked to the ω-hydroxyl group of α,ω-dihydroxy palmitate [16:0-α,ω-di-OH] with an unsubstituted carboxyl group. The acyl chain forming aglycon can be replaced by [18:0-(α,ω-di-OH)], [18:0-(α,ω-1,ω-tri-OH)], and [18:0-(α,ω-2,ω-tri-OH)]. The complex has a comparatively high surface activity; 0.5 mg/ml of it reduced the surface tension of 0.1 M NaHCO3 from 71 mN/m to 37 mN/m and interfacial tension against n-hexadecane from 39 mN/m to 10 mN/m. The critical micelle concentration of the complex at pH 4.0, determined by the fluorometric method with N-phenyl-1-naphthylamine as fluorescent probe and by the De Nouy ring method, was 2×10−5 M (taking the average molecular mass of the complex to be 750); it did not depend on the presence of 100 mM KCl and was an order of magnitude higher at pH 7.0. By fluorescence resonance energy transfer spectroscopy with N-(7-nitro-2,1,3-benzoxadiazol-4-yl)-phosphatidylethanolamine as energy donor and N-(rhodamine B sulfonyl)-phosphatidylethanolamine as energy acceptor the complex was shown to intercalate into the liposomal lipid matrix. Primary lesions caused by the complex in planar lipid bilayers were revealed as short-living current fluctuations of a broad spectrum of amplitudes. The mycocidal effect of the complex is suggested to be associated with its detergent-like properties

The Lipopolysaccharide from Capnocytophaga canimorsus Reveals an Unexpected Role of the Core-Oligosaccharide in MD-2 Binding

Capnocytophaga canimorsus is a usual member of dog's mouths flora that causes rare but dramatic human infections after dog bites. We determined the structure of C. canimorsus lipid A. The main features are that it is penta-acylated and composed of a “hybrid backbone” lacking the 4′ phosphate and having a 1 phosphoethanolamine (P-Etn) at 2-amino-2-deoxy-d-glucose (GlcN). C. canimorsus LPS was 100 fold less endotoxic than Escherichia coli LPS. Surprisingly, C. canimorsus lipid A was 20,000 fold less endotoxic than the C. canimorsus lipid A-core. This represents the first example in which the core-oligosaccharide dramatically increases endotoxicity of a low endotoxic lipid A. The binding to human myeloid differentiation factor 2 (MD-2) was dramatically increased upon presence of the LPS core on the lipid A, explaining the difference in endotoxicity. Interaction of MD-2, cluster of differentiation antigen 14 (CD14) or LPS-binding protein (LBP) with the negative charge in the 3-deoxy-d-manno-oct-2-ulosonic acid (Kdo) of the core might be needed to form the MD-2 – lipid A complex in case the 4′ phosphate is not present

Synthesis of the lipoteichoic acid of the streptococcus species DSM 8747

The lipoteichoic acid (LTA) of the Streptococcus species DSM 8747 consists of a Beta-D-galactofuranosyl diacylglycerol moiety (with different acyl groups) that is linked via 6-0 to a poly(glycerophosphate) backbone; about 30% of the glycerophosphate moieties carry at 2-0 hydrolytically labile o-alanyl residues. As typical LTA for this array of compounds LTA la was synthesized. To this end, from o-galactose the required galactofuranosyl building block 5 was obtained. The anomeric stereocontrol in the glycosylation step with 1,2-0-cyclohexylidene-sn-glycerol (4) was based on anchimeric assistance, thus finally leading to the unprotected core glycolipid 16. Regioselective protection and de protection procedures permitted the defined attachment of the pentameric glycerophosphate 3 to the 6-hydroxy group of the galactose residue. Introduction of four D-alanyl residues led after global deprotection and purification to target molecule la possessing on average about two D-alanyl residues at 2-0 of the pentameric glycerophosphate backbone, thus being in close accordance with the structure of the natural material

Lipid A components fromPseudomonas aeruginosa PAO1(serotype O5) and mutant strains investigated by electrospray ionization ion-trap mass spectrometry

International audienc