References: Lecithin
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Perfringolysin O (theta-toxin) is a cholesterol-binding and pore-forming toxin that shares with other thiol-activated cytolysins a highly conserved sequence, ECTGLAWEWWR (residues 430-440), near the C-terminus. To understand the membrane-insertion and pore-forming mechanisms of the toxin, we evaluated the contribution of each Trp to the toxin conformation during its interaction with liposomal membranes. Circular dichroism (CD) spectra of Trp mutant toxins indicated that only Trp436 has a significant effect on the secondary structure, and that Trp436, Trp438, and Trp439 make large contributions to near-UV CD spectra. Quenching the intrinsic Trp fluorescence of the wild-type and mutant toxins with brominated lecithin/cholesterol liposomes revealed that Trp438 and probably Trp436, but not Trp439, contributes to toxin insertion into the liposomal membrane. Near-UV CD spectra of the membrane-associated mutant toxins indicated that both Trp438 and Trp439 are required for the CD peak shift from 292 to 300 nm, a signal related to theta-toxin oligomerization and/or pore formation, suggesting a conformational change around Trp438 and Trp439 in these processes.
Laxative online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9604004&dopt=Abstract lecithin
Tokai J Exp Clin Med. 1993 Dec;18(3-6):81-6.
Effects of pravastatin on lipid transfer protein and lecithin cholesterol acyltransferase in heterozygous familial hypercholesterolemia.
Fusegawa Y, Tada H, Oguma T, Shiina Y, Moriguchi EH, Tanabe T, Tamachi H, Tomoda H, Goto Y.
First Department of Internal Medicine, Tokai University School of Medicine, Japan.
The effects of HMG CoA reductase inhibitor PRAVASTATIN on plasma lipoprotein levels, lipid transfer protein (LTP) activity and lecithin cholesterol acyltransferase (LCAT) activity were investigated in 20 patients with heterozygous familial hypercholesterolemia. Plasma total cholesterol decreased from 299.2 +/- 45.2 to 245.9 +/- 45.1 (mean +/- SD in mg/dl) (p < 0.0001), low density lipoprotein (LDL) cholesterol from 221.1 +/- 47.6 to 164.9 +/- 48.1 (p < 0.0001) and LDL-triglycerides from 38.0 +/- 10.2 to 30.2 +/- 8.8 (p < 0.0001). High density lipoprotein (HDL) cholesterol increased from 60.1 +/- 13.9 to 63.1 +/- 17.0 (p = 0.0264). The HDL-cholesterol: HDL-triglycerides ratio increased from 3.91 +/- 1.14 to 4.91 +/- 1.65 (p = 0.0029). Lipid transfer protein (LTP) activity (as % of transferred cholesteryl ester (CE)) decreased from 4.68 +/- 2.47 to 3.70 +/- 2.31 (p = 0.0024) and LCAT activity decreased from 113.1 +/- 29.9 (U/L) to 97.0 +/- 22.7. There was a negative correlation between LTP/LCAT ratio and HDL-C levels. These results suggested that the changes in plasma HDL-cholesterol concentrations during treatment with pravastatin may be related to the decreases in LTP and LCAT activity due to this drug.
Laxative online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=7701533&dopt=Abstract lecithin
Biochimie. 1989 Jan;71(1):89-98.
Lateral order in mixed lipid bilayers and its influence on ion translocation by gramicidin: a model for the structure-function relationship in membranes.
Henkel T, Mittler S, Pfeiffer W, Rotzer H, Apell HJ, Knoll W.
Technische Universitat Munchen, Physik-Department, Garching, FRG.
The temperature-composition phase diagram of dimyristoylphosphatidylcholine and dipentadecylphosphatidylglycerol (DiC15PG) was determined by mass densitometry. For a mixture containing 30 mol% DiC15PG, the homogeneous distribution of the 2 components is demonstrated in the fluid state at T = 35 degrees C by small-angle neutron scattering in combination with the inverse contrast variation method. By the same technique, the coexistence of fluid and condensed phases at T = 23.3 degrees C could be shown in agreement with the densitometric data. Furthermore, it is demonstrated that Ca++ induces, even at T = 35 degrees C, separation into 2 fluid phases. A corresponding phase separation is found in bimolecular lipid membranes ("black films") by analysis of the single-channel conductance fluctuations of gramicidin A incorporated into an equimolarly mixed membrane of neutral lecithin and charged phosphatidic acid. The results are discussed as primary examples on the model-membrane level for the important structure-function relationship of biomembranes.
Laxative online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=2470421&dopt=Abstract lecithin
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