Lipoproteins/lipopeptides

New insights into the analysis of hydrophobically post-translational modified proteins could be achieved by the construction of lipidated proteins in a combination of bioorganic synthesis of activated lipopeptides and bacterial expression of the protein backbone (Fig. 19). The physico-chemical properties of such artificial lipoproteins differ substantially from those of the corresponding lipopeptides. The pronounced dominance of the hydrophilic protein moiety (e.g., for the Ras protein 181 amino acids) over a short lipopeptide with one or two hydrophobic modifications provides solubility up to 10 4 mol/1, while the biotinylated or fluorescence labeled lipopeptides exhibit low solubility in aqueous solutions and can be applied in the biophysical experiments only in vesicle integrated form or dissolved in organic solvent. 

To better understand the structural properties of the lipoproteins involved in intracellular signaling pathways, synthetic lipopeptides are required as model compounds. In this context, to bypass the enzyme-catalyzed lipidation occurring in nature, optimized synthetic procedures have been elaborated for the more simple lipo-derivatives (for comprehensive reviews see ref[1]). However, similar efficient synthetic procedures for the glycosylphosphatidylinositol anchor are still lacked. 

Schromm, A.B., Reding, N., Howe, J., Wiesmuller, K.H., Roessle, M., Brandenburg, K. Influence of serum on the immune recognition of a synthetic lipopeptide mimetic of the 19-kDa lipoprotein from Mycobacterium tuberculosis. Innate Immun (2010) (in press). 

TLR 2 Gram positive bacterial cell wall component lipoteichoic acid. Host cell heat shock protein HSP70. Fungal zymosan (Beta-glucan). Multiple bacterial glycolipids, lipopeptides and lipoproteins. 

A wide variety of microorganisms also produce many kinds of surface-active lipoproteins or lipopeptides [63]. Mostly they exhibit the typical amphiphilic character and are generally extracellular. Representative of such surface-active lipopeptides is surfactin produced by Bacillus subtilis. It is composed of a heptapeptide cycle closed by a C14.15 P-hydroxy fatty acid that forms a lactone ring system (Fig. 15) [64]. This structure resembles those of iturins, another class of lipopeptides also produced by Bacillus subtilis [65]. 

Bessler, W. G., M. Cox, et al. (1998). "Synthetic lipopeptide analogs of bacterial lipoprotein are potent polyclonal activators for murine B lymphocytes." Journal of Immunology 135 1900-1905. 

Hoffmann, P., S. Heinle, et al. (1998). "timulation of human and murine adherent cells by bacterial lipoprotein and synthetic lipopeptide analogues." Immunobiology V7J 158-170. 

Biosurfactants are classified based on their chemical composition and microbial origin. The chemical structure of biosurfactants contains hydrophilic and hydrophobic groups. Amino acids, peptides and polysaccharides can be present as hydrophilic moieties and saturated or unsaturated fatty acids can be present as hydrophobic moieties in the structure. Structure based classification has following major classes of biosurfactants (Guerra-Santos et al., 1987 Kooper and Goldenberg, 1987) (i) Glycolipids (Rhamnolipids, Trehalolipids and Sophorolipids) (ii) Lipopeptide and lipoprotein (iii) Fatty acids, phospholipids and neutral lipids (iv) Pol5mieric biosurfactants, and (v) Particulate biosurfactants. 

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