Relationship between lipid saturation and lipid-protein interaction in liver mitochondria modified by catalytic hydrogenation with reference to cardiolipin molecular species.
Lipid acyl double bonds in isolated mitochondrial membranes were gradually reduced by palladium-complex-catalysed hydrogenation, and the resulting saturation was monitored by fatty acid analysis of phosphatidylcholine, phosphatidylethanolamine and cardiolipin. The courses of hydrogenation of these phospholipids suggested that cardiolipin is in a membrane compartment which is less accessible to the applied catalyst. Native cardiolipin and its hydrogenation products were further characterized by analysis of their molecular diacylglycerol species. A decrease in the double bond content was accompanied by an increased amount of motionally restricted lipids at the hydrophobic interface of proteins as measured by two different spin-labelled lipids (C-14 positional isomers of spin-labelled stearic acid and phosphatidylcholine analogues). The protein-immobilized fraction of spin-labelled stearic acid increased in parallel with the hydrogenation of cardiolipin rather than of phosphatidylcholine or phosphatidylethanolamine. These data are interpreted in terms of a tight association of cardiolipin with membrane proteins, which becomes looser upon double bond reduction leading to the replacement of cardiolipin by spin-labelled stearic acid in the solvation shell. Thus the hydrophobic moiety of cardiolipin, characterized by double-unsaturated C18-C18 diacylglycerol species, seems to be an important structural requirement for the high protein affinity of this compound.
Schlame
M
M
Institute of Biochemistry, Biological Research Center, Szeged, Hungary.
Horvàth
L
L
Vìgh
L
L
D000818:Animals; D002308:Cardiolipins / Q000378:metabolism*; D002384:Catalysis; D002851:Chromatography, High Pressure Liquid; D004075:Diglycerides / Q000032:analysis; D004578:Electron Spin Resonance Spectroscopy; D006865:Hydrogenation; D050356:Lipid Metabolism; D008930:Mitochondria, Liver / Q000378:metabolism*; D010713:Phosphatidylcholines / Q000378:metabolism; D011506:Proteins / Q000378:metabolism*; D051381:Rats; D013056:Spectrophotometry, Ultraviolet; D013229:Stearic Acids / Q000378:metabolism
D002308:Cardiolipins; D004075:Diglycerides; D010713:Phosphatidylcholines; D011506:Proteins; D013229:Stearic Acids; C031183:stearic acid