Effect of rat serum albumin-cholesterol on the physical properties of biomembranes.
Affinity chromatography, using Cibacron blue F3GA bound to Sepharose 4B, and Sephadex G-150 column chromatography, permit the isolation of large quantities of non-esterified cholesterol loaded albumin from rat serum. Unlabeled cholesterol and cholesterol oxides displaced 14C-cholesterol bound to albumin in a dose-dependent manner. Binding of 14C-cholesterol to rat serum albumin in vitro follows a sigmoid curve. Ca2+ ions (up to 10 mM) inhibited the cholesterol binding to albumin in vitro. Fluorescence anisotropy of diphenyl-hexatriene (DPH) embedded in the lipid core of rat brain synaptosomal plasma membranes (SPM) increased with albumin-cholesterol incorporation and decreased in parallel to cholesterol removal. The allosteric properties of the SPM-bound (Na+ + K+)ATPase by fluoride (F-) (as reflected by changes in the Hill coefficient) were modulated by albumin-cholesterol, suggesting that the physical state of the (Na+ + K+)ATPase lipid microenvironment changed from a liquid-crystalline to gel phase. The present studies concerning albumin-cholesterol complex, its behavior and its role in the structure of biomembranes, provide important new clues to the role of this fascinating molecule in normal and pathological states.
Deliconstantinos
G
G
Department of Experimental Physiology, University of Athens Medical School, Greece.
D000418:Albumins / Q000302:isolation & purification / Q000378:metabolism*; D000818:Animals; D001667:Binding, Competitive; D001921:Brain / Q000378:metabolism; D002118:Calcium; D002462:Cell Membrane / Q000378:metabolism; D002784:Cholesterol / Q000097:blood* / Q000302:isolation & purification / Q000378:metabolism*; D005454:Fluorescence Polarization; D007700:Kinetics; D051381:Rats; D012709:Serum Albumin / Q000378:metabolism*; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism; D013574:Synaptosomes / Q000378:metabolism*
D000418:Albumins; D012709:Serum Albumin; C050323:cholesterol-albumin complex; D002784:Cholesterol; D000254:Sodium-Potassium-Exchanging ATPase; D002118:Calcium