1. Maturation of the malarial phosphatidylserine decarboxylase is mediated by high affinity binding to anionic phospholipids.
- Author
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Choi JY, Lopes L, Ben Mamoun C, and Voelker DR
- Subjects
- Amino Acid Motifs, Calcium metabolism, Calcium pharmacology, Enzyme Precursors metabolism, Liposomes, Phosphatidic Acids metabolism, Phosphatidic Acids pharmacology, Phosphatidylcholines metabolism, Phosphatidylcholines pharmacology, Phosphatidylethanolamines metabolism, Phosphatidylethanolamines pharmacology, Phosphatidylglycerols metabolism, Phosphatidylglycerols pharmacology, Phosphatidylinositols metabolism, Phosphatidylinositols pharmacology, Phosphatidylserines metabolism, Phosphatidylserines pharmacology, Protein Binding, Proteolysis drug effects, Surface Plasmon Resonance, Carboxy-Lyases antagonists & inhibitors, Carboxy-Lyases chemistry, Carboxy-Lyases metabolism, Phospholipids chemistry, Phospholipids metabolism, Phospholipids pharmacology, Malaria parasitology, Plasmodium enzymology
- Abstract
Decarboxylation of phosphatidylserine (PS) to form phosphatidylethanolamine by PS decarboxylases (PSDs) is an essential process in most eukaryotes. Processing of a malarial PSD proenzyme into its active alpha and beta subunits is by an autoendoproteolytic mechanism regulated by anionic phospholipids, with PS serving as an activator and phosphatidylglycerol (PG), phosphatidylinositol, and phosphatidic acid acting as inhibitors. The biophysical mechanism underlying this regulation remains unknown. We used solid phase lipid binding, liposome-binding assays, and surface plasmon resonance to examine the binding specificity of a processing-deficient Plasmodium PSD (PkPSDS308A) mutant enzyme and demonstrated that the PSD proenzyme binds strongly to PS and PG but not to phosphatidylethanolamine and phosphatidylcholine. The equilibrium dissociation constants (K
d ) of PkPSD with PS and PG were 80.4 nM and 66.4 nM, respectively. The interaction of PSD with PS is inhibited by calcium, suggesting that the binding mechanism involves ionic interactions. In vitro processing of WT PkPSD proenzyme was also inhibited by calcium, consistent with the conclusion that PS binding to PkPSD through ionic interactions is required for the proenzyme processing. Peptide mapping identified polybasic amino acid motifs in the proenzyme responsible for binding to PS. Altogether, the data demonstrate that malarial PSD maturation is regulated through a strong physical association between PkPSD proenzyme and anionic lipids. Inhibition of the specific interaction between the proenzyme and the lipids can provide a novel mechanism to disrupt PSD enzyme activity, which has been suggested as a target for antimicrobials, and anticancer therapies., Competing Interests: Conflict of interest The authors declare that they have no conflicts of interest with the contents of this article., (Copyright © 2023 The Authors. Published by Elsevier Inc. All rights reserved.)- Published
- 2023
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