Structure of a Eukaryotic Cholinephosphotransferase-1 Reveals Mechanisms of Substrate Recognition and Catalysis

Authors

Lie Wang
Ming Zhou

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

Published Open-Access

yes

Keywords

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

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.

Comments

Associated Data