CHARACTERIZATION OF LIPID PARTICLES OF THE YEAST, SACCHAROMYCES-CEREVISIAE

Lipid particles of the yeast, Saccharomyces cerevisiae, were isolated to high purity and their components were analysed. The hydrophobic core of this organelle consists of triacylglycerols and steryl esters, which are almost exclusively located to that compartment. Lipid particles are stabilized by a surface membrane consisting of phospholipids and proteins. Electron microscopy confirmed the purity of the preparations and the proposed structure deduced from biochemical experiments. Major proteins of lipid particles have molecular weights of 72, 52, 43 and 34 kDa, respectively. The 43 kDa protein reacts with an antiserum against human apolipoprotein AII. In lipid particles of the yeast mutant strain S. cerevisiae erg6, which is deficient in sterol Delta(24)-methyltransferase, this protein is missing thereby identifying the protein and confirming our previous finding (Zinser et al., 1993) that sterol Delta(24)-methylation is associated with lipid particles. A possible involvement of surface proteins of lipid particles in the interaction with other organelles is discussed with respect to sterol translocation in yeast.