Identification and characterization of major lipid particle proteins of the yeast Saccharomyces cerevisiae

Lipid particles of the yeast Saccharomyces cerevisiae were isolated at high purity, and their proteins were separated by sodium dodecyl sulfate-polyac rylamide gel electrophoresis, Major lipid particle proteins were identified by mass spectrometric analysis, and the corresponding open reading frames (ORFs) were deduced. In silicio analysis revealed that all lipid particle p roteins contain several hydrophobic domains but none or only few (hypotheti cal) transmembrane spanning regions. All lipid particle proteins identified by function so far, such as Erg1p, Erg6p, and Erg7p (ergosterol biosynthes is) and Faa1p, Faa4p, and Fat1p (fatty acid metabolism), are involved in li pid metabolism. Based on sequence homology, another group of three lipid pa rticle proteins may be involved in lipid degradation. To examine whether li pid particle proteins of unknown function are also involved in lipid synthe sis, mutants with deletions of the respective ORFs were constructed and sub jected to systematic lipid analysis. Deletion of YDL193w resulted in a leth al phenotype which could not be suppressed by supplementation with ergoster ol or fatty acids. Other deletion mutants were viable under standard condit ions, Strains with YBR177c, YMR313c, and YKL140w deleted exhibited phosphol ipid and/or neutral lipid patterns that were different from the wild-type s train and thus may be further candidate ORFs involved in yeast lipid metabo lism.