Defining the molecular requirements for phosphatidylserine decarboxylase activation (757.3)

Abstract

Phosphatidylethanolamine (PE) is a major membrane phospholipid that is critical for a multitude of biological processes and essential for life. One pathway of PE production occurs in the mitochondrion. Psd1p, the responsible enzyme, decarboxylates phosphatidylserine (PS) to PE. Psd1p is encoded in the nucleus and imported into the mitochondrion post‐translationally. The final active enzyme is produced by autocatalytic processing. Autocatalysis occurs at a conserved LGST motif. The result is a membrane anchored β‐subunit that remains associated with a small α‐subunit, which contains a catalytically essential pyruvoyl group on its N terminus. The goal of the present study was to further characterize Psd1p autocatalysis at the molecular level and define additional requirements for this process. Here, we demonstrate that neither mitochondrial lipids nor proteins are critical for Psd1p autocatalysis. Further, an autocatalytic mutant Psd1p assembles normally, indicating that Psd1p folding precedes autocatalysis. Finally, a temperature sensitive (ts) allele has perturbed autocatalysis at non‐permissive temperature, thus establishing the thermosensitive loss‐of‐function mechanism. Understanding the molecular requirements for Psd1p autocatalysis may uncover potential regulatory steps in Psd1p activity, which may be exploited to modulate cellular PE content.Grant Funding Source: R01 HL108882‐01A1