FLOTATION OF LIPID-PROTEIN PARTICLES CONTAINING TRIACYLGLYCEROL AND PHOSPHOLIPID FROM THE CYTOSOL OF CARNATION PETALS

Lipid-protein particles ranging from 20 to 250 nm in diameter have bee n isolated from the cytosol of carnation petals by Rotation centrifuga tion and also by ultrafiltration. The cytosolic lipid-protein particle s resemble oil bodies, lipid-protein particles found in oil-bearing se eds, in that they contain triacylglycerol, are circumscribed by phosph olipid that is not organized in a bilayer, appear to be derived from m embranes and can be isolated by flotation. However, the cytosolic part icles are distinguishable from oil bodies in that triacylglycerol is n ot the dominant lipid. Indeed, they contain a spectrum of lipids in ad dition to phospholipids and triacylglycerol including free fatty acids , sterol and wax esters, phosphatidic acid and diacylglycerol. These s ame lipids are present in corresponding microsomal membranes as well, but in much smaller proportions relative to phospholipid. The lipid-pr otein particles from carnation petals contain a 17-kDa protein that is of similar size to oil body oleosin, but does not cross-react with an ti-oleosin antibodies. The data indicate that these cytosolic particle s are structurally and chemically similar to oil bodies and are consis tent with the notion that their genesis may be a means of removing des tabilizing lipids from membrane bilayers.