Diacyglycerol pyrophosphate (DGPP) an uncommon membrane lipid found in plants, and yeast, but never in mammals is formed from phosphatidic acid. The function of DGPP during stress signaling is unclear. Therefore, the physiochemical properties, specifically the ionization of the head group, were analyzed to elucidate the function of DGPP. The presence of the trans-membrane peptide KALP23, to mimic the interaction with DGPP binding proteins, caused an increase in the ionization of DGPP. This increase in negative charge might be due to the decrease in interfacial pH by the cationic lysine residues of KALP23, or might be due to direct hydrogen bond interaction between KALP23 and DGPP. We investigated the effect of positive charge on the negative charge of DGPP to delineate these separate effects. Next, we investigated the interaction of PA with DGPP and the resultant effect on the charge of both of these signaling lipids. The results are discussed in terms of the electrostatic-hydrogen bond switch model previously described for the ionization and protein interaction of PA.
Dr. Edgar Kooijman