CPT1 encodes sn-1,2-diacylglycerol cholinephosphotransferase (EC 2.7.8.2) of Saccharomyces cerevisiae, a multi-pass membrane enzyme of the CDP-alcohol phosphatidyltransferase family. Using Mg2+, it transfers phosphocholine from CDP-choline to diacylglycerol to form phosphatidylcholine and CMP, the final step of the CDP-choline (Kennedy) pathway; it also accepts CDP-dimethylethanolamine. Cpt1 is relatively specific for CDP-choline, whereas its paralogue Ept1 uses CDP-ethanolamine and CDP-choline; Cpt1 provides most cellular cholinephosphotransferase activity. The CDP-choline pathway makes net PC when exogenous choline is supplied and otherwise recycles choline from PC turnover, helping to shape PC molecular species. Cpt1 is located in the ER membrane, with activity also detected in Golgi and mitochondrial outer membrane fractions; it is nonessential and its expression is repressed by inositol. A functional CPT1 is required for the inositol-dependent repression of phospholipid synthesis, including the inositol-dependent reduction of EPT1 transcript levels. In vivo labelling shows that Cpt1 converts CDP-dimethylethanolamine, whereas CDP-monomethylethanolamine is used preferentially by Ept1.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0004142 diacylglycerol cholinephosphotransferase activity | EXP PMID:1847919 sn-1,2-diacylglycerol choline- and ethanolaminephosphotransf... | ACCEPT | Summary: Mixed-micelle assays of membranes from ept1 strains showed the CPT1 product is a DAG cholinephosphotransferase with relative specificity for CDP-choline and CDP-dimethylethanolamine. Supporting Evidence: PMID:1847919 The Saccharomyces cerevisiae CPT1 and EPT1 genes are structural genes encoding distinct sn-1,2-diacylglycerol choline- and ethanolaminephosphotransferases. PMID:1847919 the CPT1 gene product manifested relative specificity for CDP-choline and -dimethylethanolamine |
| GO:0004142 diacylglycerol cholinephosphotransferase activity | IDA PMID:3029130 Mutants of Saccharomyces cerevisiae defective in sn-1,2-diac... | ACCEPT | Summary: Cloned CPT1 directed 5-fold overproduction of cholinephosphotransferase activity, identifying it as the structural gene. Supporting Evidence: PMID:3029130 In strains transformed with the CPT1-bearing plasmid, a 5-fold overproduction of cholinephosphotransferase activity with wild-type kinetic properties was observed. PMID:3029130 The data indicate that the cloned CPT1 gene represents the yeast cholinephosphotransferase structural gene |
| GO:0004142 diacylglycerol cholinephosphotransferase activity | IEA GO_REF:0000120 | ACCEPT | Summary: ARBA/RHEA:32939/EC 2.7.8.2 mapping; correct. Supporting Evidence: file:yeast/CPT1/CPT1-uniprot.txt FUNCTION: Catalyzes the final step in the CDP-choline route leading to |
| GO:0004142 diacylglycerol cholinephosphotransferase activity | IMP PMID:3029130 Mutants of Saccharomyces cerevisiae defective in sn-1,2-diac... | ACCEPT | Summary: cpt1 insertional mutant membranes had 5-fold reduced cholinephosphotransferase activity. Supporting Evidence: PMID:3029130 The cholinephosphotransferase activity in membranes prepared from the cpt1 insertional mutant was reduced 5-fold and exhibited CMP sensitivity. |
| GO:0004142 diacylglycerol cholinephosphotransferase activity | RCA GO_REF:0000123 | ACCEPT | Summary: YeastPathways RCA (PHOS-PWY) assigning EC 2.7.8.2 (CDP-choline + DAG -> PC + CMP) to Cpt1. Correct reaction assignment. Supporting Evidence: PMID:3029130 The data indicate that the cloned CPT1 gene represents the yeast cholinephosphotransferase structural gene |
| GO:0004142 diacylglycerol cholinephosphotransferase activity | RCA GO_REF:0000123 | ACCEPT | Summary: YeastPathways RCA (PWY3O-2) assigning EC 2.7.8.2 (CDP-choline + DAG -> PC + CMP) to Cpt1. Correct reaction assignment. Supporting Evidence: PMID:3029130 The data indicate that the cloned CPT1 gene represents the yeast cholinephosphotransferase structural gene |
| GO:0004142 diacylglycerol cholinephosphotransferase activity | RCA GO_REF:0000123 | ACCEPT | Summary: YeastPathways RCA (PWY3O-450, phosphatidylcholine biosynthesis I) assigning EC 2.7.8.2 (CDP-choline + DAG -> PC + CMP) to Cpt1. Correct reaction assignment. Supporting Evidence: PMID:3029130 The data indicate that the cloned CPT1 gene represents the yeast cholinephosphotransferase structural gene |
| GO:0005515 protein binding | IPI PMID:18467557 An in vivo map of the yeast protein interactome. | REMOVE | Summary: IPI with the paralogue Ept1 (P22140) from the Tarassov et al. 2008 PCA interactome. Bare protein binding carries no functional information; removal does not dispute the Cpt1-Ept1 association. Reason: Generic protein binding is uninformative. |
| GO:0005515 protein binding | IPI PMID:31454312 The role of structural pleiotropy and regulatory evolution i... | REMOVE | Summary: IPI with Ept1 (P22140) from a paralogue-retention study (Marchant et al. 2019) using PCA. Bare protein binding is uninformative; the Cpt1-Ept1 heteromeric interaction is noted but does not define a molecular function. Reason: Generic protein binding is uninformative. |
| GO:0005515 protein binding | IPI PMID:37968396 The social and structural architecture of the yeast protein ... | REMOVE | Summary: IPI with Ept1 (P22140) from the 2023 yeast protein interactome (Michaelis et al.). Bare protein binding is uninformative. Reason: Generic protein binding is uninformative. |
| GO:0005741 mitochondrial outer membrane | IDA PMID:3005242 Subcellular and submitochondrial localization of phospholipi... | KEEP AS NON CORE | Summary: Kuchler et al. (1986) detected cholinephosphotransferase activity in purified outer mitochondrial membrane. This predates gene assignment (activity could include Ept1) and may partly reflect ER contamination, but the curator's IDA is retained as a secondary location. Reason: Experimental fractionation; principal location is ER. Supporting Evidence: PMID:3005242 Cholinephosphotransferase was apparently located at the inner aspect or within the outer mitochondrial membrane. |
| GO:0005741 mitochondrial outer membrane | IEA GO_REF:0000044 | KEEP AS NON CORE | Summary: UniProt subcellular location (SL-0172, mitochondrion outer membrane) derived from fractionation studies. Secondary location. Reason: Secondary location. Supporting Evidence: PMID:3005242 Cholinephosphotransferase was apparently located at the inner aspect or within the outer mitochondrial membrane. |
| GO:0005783 endoplasmic reticulum | HDA PMID:26928762 One library to make them all: streamlining the creation of y... | ACCEPT | Summary: SWAp-Tag high-throughput localisation placed Cpt1 in the ER; consistent with microsomal activity. Supporting Evidence: PMID:26928762 we only assigned localizations that could be easily discriminated by eye: ER, nuclear periphery, cytosol, cell periphery |
| GO:0005789 endoplasmic reticulum membrane | IEA GO_REF:0000044 | ACCEPT | Summary: UniProt subcellular location (SL-0097, ER membrane). Main site of Cpt1 activity. Supporting Evidence: file:yeast/CPT1/CPT1-uniprot.txt Endoplasmic reticulum membrane; Multi-pass membrane protein. |
| GO:0005794 Golgi apparatus | IDA PMID:8543066 Phospholipid-synthesizing enzymes in Golgi membranes of the ... | KEEP AS NON CORE | Summary: Leber et al. detected DAG cholinephosphotransferase activity in purified Golgi membranes at a specific activity exceeding the ER. Experimental evidence for a Golgi pool; Golgi PC synthesis has been linked to Sec14 function. Retained as a secondary location. Reason: Secondary location; enzyme activity in subcellular fraction. Supporting Evidence: PMID:8543066 Two phospholipid-synthesizing enzymes, namely phosphatidylinositol synthase and sn-1,2-diacylglycerol cholinephosphotransferase, are detected in the Golgi at a specific activity which exceeds that of the endoplasmic reticulum. |
| GO:0005829 cytosol | RCA GO_REF:0000123 | MODIFY | Summary: YeastPathways RCA (PHOS-PWY) places the cholinephosphotransferase reaction in the cytosol by pathway default. Cpt1 is a multi-pass ER membrane enzyme acting on membrane DAG; the activity is not cytosolic. Reason: Wrong compartment from pathway default. Proposed replacements: endoplasmic reticulum membrane Supporting Evidence: file:yeast/CPT1/CPT1-uniprot.txt Endoplasmic reticulum membrane; Multi-pass membrane protein. |
| GO:0005829 cytosol | RCA GO_REF:0000123 | MODIFY | Summary: YeastPathways RCA (PWY3O-2) places the cholinephosphotransferase reaction in the cytosol by pathway default. Cpt1 is a multi-pass ER membrane enzyme acting on membrane DAG; the activity is not cytosolic. Reason: Wrong compartment from pathway default. Proposed replacements: endoplasmic reticulum membrane Supporting Evidence: file:yeast/CPT1/CPT1-uniprot.txt Endoplasmic reticulum membrane; Multi-pass membrane protein. |
| GO:0005829 cytosol | RCA GO_REF:0000123 | MODIFY | Summary: YeastPathways RCA (PWY3O-450) places the cholinephosphotransferase reaction in the cytosol by pathway default. Cpt1 is a multi-pass ER membrane enzyme acting on membrane DAG; the activity is not cytosolic. Reason: Wrong compartment from pathway default. Proposed replacements: endoplasmic reticulum membrane Supporting Evidence: file:yeast/CPT1/CPT1-uniprot.txt Endoplasmic reticulum membrane; Multi-pass membrane protein. |
| GO:0006656 phosphatidylcholine biosynthetic process | IEA GO_REF:0000120 | ACCEPT | Summary: ARBA/UniPathway UPA00753 (PC from phosphocholine, step 2/2) mapping. Correct; Cpt1 makes PC. Supporting Evidence: file:yeast/CPT1/CPT1-uniprot.txt FUNCTION: Catalyzes the final step in the CDP-choline route leading to |
| GO:0006657 CDP-choline pathway | IDA PMID:3029130 Mutants of Saccharomyces cerevisiae defective in sn-1,2-diac... | ACCEPT | Summary: Cholinephosphotransferase activity of the CPT1 product, the final step of the CDP-choline pathway. Supporting Evidence: PMID:3029130 The data indicate that the cloned CPT1 gene represents the yeast cholinephosphotransferase structural gene |
| GO:0006657 CDP-choline pathway | IMP PMID:3029130 Mutants of Saccharomyces cerevisiae defective in sn-1,2-diac... | ACCEPT | Summary: cpt1 mutants have reduced cholinephosphotransferase activity, placing Cpt1 in the CDP-choline pathway. Supporting Evidence: PMID:3029130 The cholinephosphotransferase activity in membranes prepared from the cpt1 insertional mutant was reduced 5-fold and exhibited CMP sensitivity. |
| GO:0006657 CDP-choline pathway | RCA GO_REF:0000123 | ACCEPT | Summary: YeastPathways RCA (PWY3O-450) to CDP-choline pathway; correct and precise. Supporting Evidence: PMID:3029130 The data indicate that the cloned CPT1 gene represents the yeast cholinephosphotransferase structural gene |
| GO:0008654 phospholipid biosynthetic process | IEA GO_REF:0000002 | ACCEPT | Summary: InterPro IPR000462 mapping to phospholipid biosynthetic process. Correct general process. Supporting Evidence: file:yeast/CPT1/CPT1-uniprot.txt FUNCTION: Catalyzes the final step in the CDP-choline route leading to |
| GO:0008654 phospholipid biosynthetic process | RCA GO_REF:0000123 | ACCEPT | Summary: YeastPathways RCA (PHOS-PWY) to phospholipid biosynthetic process. Correct general process. Supporting Evidence: PMID:3029130 The data indicate that the cloned CPT1 gene represents the yeast cholinephosphotransferase structural gene |
| GO:0008654 phospholipid biosynthetic process | RCA GO_REF:0000123 | ACCEPT | Summary: YeastPathways RCA (PWY3O-2) to phospholipid biosynthetic process. Correct general process. Supporting Evidence: PMID:3029130 The data indicate that the cloned CPT1 gene represents the yeast cholinephosphotransferase structural gene |
| GO:0016020 membrane | IEA GO_REF:0000002 | TOO GENERAL | Summary: InterPro-based membrane annotation; correct but general. Supporting Evidence: file:yeast/CPT1/CPT1-uniprot.txt SUBCELLULAR LOCATION: Microsome membrane; Multi-pass membrane protein. |
| GO:0016780 phosphotransferase activity, for other substituted phosphate groups | IEA GO_REF:0000002 | ACCEPT | Summary: InterPro IPR000462 mapping to phosphotransferase activity, for other substituted phosphate groups. Correct parent of the cholinephosphotransferase activity. Supporting Evidence: file:yeast/CPT1/CPT1-uniprot.txt FUNCTION: Catalyzes the final step in the CDP-choline route leading to |
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Download this section (compressed HTML)Q: What is the functional significance of the Cpt1-Ept1 interaction detected in several interactome screens: do they form heteromers that alter substrate selectivity or localisation?
Q: Is the Golgi-localised cholinephosphotransferase activity due to Cpt1 itself, and does it supply the PC pool relevant to Sec14-dependent secretion?
Experiment: Localise endogenously tagged Cpt1 relative to Golgi and ER markers by super-resolution microscopy, and measure Golgi PC synthesis in cpt1 and ept1 mutants.
Cholinephosphotransferase; required for phosphatidylcholine biosynthesis and for inositol-dependent regulation of EPT1 transcription; CPT1 has a paralog, EPT1, that arose from the whole genome duplication
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