Yeast Pah1 PA phosphatase contains a novel domain within its N‐terminal intrinsically disordered region

Abstract

Pah1 PA phosphatase catalyzes the dephosphorylation of PA to produce diacylglycerol. In yeast and higher eukaryotes, the diacylglycerol produced in the reaction is used for the synthesis of triacylglycerol or the membrane phospholipids phosphatidylcholine and phosphatidylethanolamine. Pah1 is inactive as a phosphorylated enzyme in the cytosol and becomes active after its recruitment and dephosphorylation by the ER‐associated Nem1‐Spo7 protein phosphatase complex. Conserved N‐LIP and HAD‐like domains are required for PA phosphatase activity and a conserved tryptophan within the WRDPLVDID domain is required for its in vivo function in lipid metabolism. Intrinsically disordered regions, which are located between the conserved catalytic domains and at the C terminus, contain multiple sites for phosphorylation and regulation of Pah1 location and function. Prediction of Pah1 structure by AlphaFold identifies a novel domain contained within the N‐terminal intrinsically disordered region for which its function is unknown. A truncation mutant that lacks amino acid residues 186‐266 have been constructed and expressed in a pah1D and pah1D nem1D mutants to assess the function of the novel domain for regulating Pah1 phosphorylation, recruitment and dephosphorylation by the Nem1‐Spo7 protein phosphatase complex, and function in lipid metabolism.