Language

English

Publication Date

5-13-2023

Journal

Nature Communications

DOI

10.1038/s41467-023-38003-9

PMID

37179328

PMCID

PMC10182977

PubMedCentral® Posted Date

5-13-2023

PubMedCentral® Full Text Version

Post-print

Abstract

Phosphatidylcholine (PC) is the most abundant phospholipid in eukaryotic cell membranes. In eukaryotes, two highly homologous enzymes, cholinephosphotransferase-1 (CHPT1) and choline/ethanolamine phosphotransferase-1 (CEPT1) catalyze the final step of de novo PC synthesis. CHPT1/CEPT1 joins two substrates, cytidine diphosphate-choline (CDP-choline) and diacylglycerol (DAG), to produce PC, and Mg2+ is required for the reaction. However, mechanisms of substrate recognition and catalysis remain unresolved. Here we report structures of a CHPT1 from Xenopus laevis (xlCHPT1) determined by cryo-electron microscopy to an overall resolution of ~3.2 Å. xlCHPT1 forms a homodimer, and each protomer has 10 transmembrane helices (TMs). The first 6 TMs carve out a cone-shaped enclosure in the membrane in which the catalysis occurs. The enclosure opens to the cytosolic side, where a CDP-choline and two Mg2+ are coordinated. The structures identify a catalytic site unique to eukaryotic CHPT1/CEPT1 and suggest an entryway for DAG. The structures also reveal an internal pseudo two-fold symmetry between TM3-6 and TM7-10, and suggest that CHPT1/CEPT1 may have evolved from their distant prokaryotic ancestors through gene duplication.

Keywords

Diacylglycerol Cholinephosphotransferase, Eukaryotic Cells, Cryoelectron Microscopy, Phosphotransferases, Cytidine Diphosphate Choline, Phosphatidylcholines, Saccharomyces cerevisiae, Catalysis

Published Open-Access

yes

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