Identification and characterization of the mitochondrial membrane sorting signals in phosphatidylserine decarboxylase 1 from Saccharomyces cerevisiae
Wagner A, Di Bartolomeo F, Klein I, Hrastnik C, Doan KN, Becker T, Daum G.
Biochim Biophys Acta. online article
The lipid composition of the membranes is important for the functions of mitochondrial protein machineries. The biosynthesis of cardiolipin (CL) and phosphatidylethanolamine (PE) takes place in the inner mitochondrial membrane, while the majority of other phospholipids are generated in the endoplasmic reticulum. The phosphatidylserine decarboxylase (Psd1) converts phosphatidylserine into PE. The biogenesis of Psd1 into mitochondria is a complicated process that involves two processing steps by mitochondrial processing peptidases. Finally, an autocatalytic cleavage events separated the membrane-bound beta-subunit from the soluble alpha-subunit. This last processing step is essential for the activity of Psd1. The sorting pathway of Psd1 is less understood. A hydrophobic sequence is important for the integration of Psd1 into the inner membrane. Strikingly, we have identified a second hydrophobic stretch within Psd1. Biochemical characterization reveals that mutations and truncations of this hydrophobic segment affects topology, stability, import and enzymatic activity of Psd1. Thus, we have shown that the second hydrophobic segment is crucial for biogenesis and function of Psd1.
