Staff Members of the Institute of Biochemistry, TU - Institut für ...

To study the general role of PE in yeast and effects of an unbalanced PE level, genome wide
effects of a ∆psd1 deletion were analyzed in a DNA microarray study. In the deletion mutant
54 genes were up-regulated compared to wild type. Three of these genes, GPH1, RSB1 and
GPM2 were analyzed in more detail during the present study. To study possible physiological
functions of the gene products, yeast strains lacking and overexpressing the respective genes
were investigated for growth phenotype on different carbon sources and phospholipid
patterns. Additionally, the localization of the GFP-tagged gene products was studied by
fluorescence microscopy, and the role of Gph1p on cell structure was analyzed by electron
microscopy. Furthermore, the influence of the genetic wild type background on the
phospholipid composition was part of this study. GPH1 which encodes a glycogen
phosphorylase seems to be essential for osmotic stability, resistance to SDS, formation of
lipid particles and a balanced phospholipid metabolism. The predicted role in osmotic stability
and resistance to SDS is linked to the genetic background. The two wild type strains BY4741
and BY4742 resulted in a different phospholipid composition of the plasma membrane. The
higher PE level of BY4741 combined with a GPH1 deletion caused osmotic instability and
strong sensitivity to SDS. Lipid analyses showed that Gph1p may be involved in synthesis
and transport of phosphatidylcholine (PC) and play also a role in neutral lipid storage. All
these findings confirmed that Gph1p is a global player in lipid metabolism, but its specific
function remained unclear. The second gene of interest, RSB1, does not play a special role in
phospholipid metabolism. Fluorescence microscopic analysis showed that Rsb1p is enriched
in PAM (plasma membrane associated membranes of the ER) where it may be involved in
LCB (sphingoid long chain base) transport and topology in bilayer membranes. These
functions seem to be important for maintaining membrane integrity, for example during
depletion of PE. A connection of GPM2 to lipid metabolism was not observed. Gpm2p is
predicted to be a non-functional homologue of Gpm1p which acts as phosphoglycerate
mutase during glycolysis and gluconeogenesis.
International cooperations
N. Pfanner, Institute of Biochemistry and Molecular Biology, ZBMZ, University of Freiburg,
Germany
R. Erdmann, Institute of Physiological Chemistry, Ruhr-University Bochum, Germany
M. Karas, Institute of Pharmaceutical Chemistry, Johann Wolfgang Goethe University,
Frankfurt, Germany
C. F. Clarke, Department of Chemistry and Biochemistry, University of California, Los
Angeles, CA, USA
S. Moye-Rowley, Molecular Physiology and Biophysics, University of Iowa, Iowa City, IA,
USA
Research projects
FWF P21429: Phosphatidylserine decarboxylase
FWF P23029 Lipases of the yeast Saccharomyces cerevisiae
FWF TRP 009 Pichia Lipidomics (Translational Research)
FWF PhD Program: Molecular Enzymology
Austrian Center of Industrial Biotechnology (ACIB): Pichia pastoris Cell Factory and Protein
Production
Invited Lectures
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