desmosterol and fucosterol

Higher sterols are universally present in large amounts (20-30%) in the plasma membranes of all eukaryotes whereas they are universally absent in prokaryotes. It is remarkable that each kingdom of the eukaryotes has chosen, during the course of evolution, its preferred sterol: cholesterol in animals, ergosterol in fungi and yeast, phytosterols in higher plants, and e.g., fucosterol and desmosterol in algae. The question arises as to which specific properties do sterols impart to membranes and to which extent do these properties differ among the different sterols. Using a range of biophysical techniques, including calorimetry, fluorescence microscopy, vesicle-fluctuation analysis, and atomic force microscopy, we have found that fucosterol and desmosterol, found in red and brown macroalgae (seaweeds), similar to cholesterol support liquid-ordered membrane phases and induce coexistence between liquid-ordered and liquid-disordered domains in lipid bilayers. Fucosterol and desmosterol induce acyl-chain order in liquid membranes, but less effectively than cholesterol and ergosterol in the order: cholesterol>ergosterol>desmosterol>fucosterol, possibly reflecting the different molecular structure of the sterols at the hydrocarbon tail.

Topics: Calorimetry, Differential Scanning; Cell Membrane; Desmosterol; Lipid Bilayers; Mechanical Phenomena; Microscopy, Atomic Force; Microscopy, Fluorescence; Molecular Structure; Seaweed; Stigmasterol

The thermotropic behavior of multilamellar vesicles (MLV) composed of different mole fractions of various marine sterols and 1-stearoyl-2-oleoyl phosphatidylcholine (SOPC) was examined by differential scanning calorimetry (DSC), and was compared to pure SOPC as well as their mixtures with cholesterol. The marine sterols investigated were capable of interacting with the phospholipid bilayers. Upon addition of marine sterols, the apparent transition temperature (Tm) of SOPC decreased significantly. Desmosterol (cholesta-5,24-dien-3 beta-ol) had the least interaction with SOPC, as reflected by the larger delta H values of its mixtures with the phospholipid. Fucosterol (24-ethylcholesta-5,24(28)-dien-3 beta-ol) showed a non-linear trend as the mole percent of the sterol increased. Mixtures of sutinasterol (24R-24-ethyl-26,26-dimethylcholesta-7,25(27)-dien-3 beta-ol) with SOPC had similar enthalpy values to cholesterol. The shape of the SOPC/marine sterol endotherm and their delta H values were not identical when liposomes prepared by dialysis were compared to MLV.

Topics: Calorimetry, Differential Scanning; Cholestadienols; Desmosterol; Eukaryota; Lipid Bilayers; Liposomes; Membrane Fluidity; Phosphatidylcholines; Sterols; Stigmasterol

Anaerobically grown Saccharomyces cerevisiae retained the ability to transfer a C1-group to the C-24 position of a delta 24(25)-sterol and to reduce the delta 25(28)-bond of a 24-methylenesterol. Both desmosterol and 24-methylenecholesterol yielded 24 beta-methylcholesterol. However, when the substituent at C-24 was enlarged to a 24-ethylidene group (fucosterol), reduction of the delta 24(28)-bond did not occur. In no cases was a delta 7- or a delta 22-bond introduced. Because the delta 24(28)-bond was reduced in the absence of the delta 22-bond, the delta 22-bond is not an obligatory requirement for reduction.

Topics: Anaerobiosis; Cholesterol; Desmosterol; Models, Biological; Oxidation-Reduction; Saccharomyces cerevisiae; Stigmasterol