GPT2 (also called GAT1) encodes one of the two redundant glycerol-3-phosphate O-acyltransferases (GPATs) of budding yeast. These are dual-substrate sn-1 acyltransferases that acylate sn-glycerol 3-phosphate to lysophosphatidic acid, or dihydroxyacetone phosphate to 1-acyl-DHAP, using acyl-CoA. This is the first and committed step of de novo glycerolipid synthesis, feeding phosphatidic acid into both membrane phospholipids (via CDP-diacylglycerol) and triacylglycerol. Gpt2 uses glycerol 3-phosphate and DHAP with similar efficiency and accepts a broad range of acyl-CoAs. It is a multi-pass membrane protein of the perinuclear and cortical ER and is also associated with lipid droplets. When cells are fed oleate, Gpt2 forms ER crescents closely apposed to lipid droplets and is required for oleate-induced droplet accumulation. Gpt2 is a phosphoprotein; phosphorylation at a conserved C-terminal motif restrains its activity and prevents a futile TAG synthesis/lipolysis cycle. GPT2 and SCT1/GAT2 are synthetically lethal.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0004366 glycerol-3-phosphate O-acyltransferase activity | IBA GO_REF:0000033 | ACCEPT | Summary: PAINT IBA for glycerol-3-phosphate O-acyltransferase activity at the fungal GPAT node (PTN000787962), grounded in Gpt2/Gat1 and Sct1/Gat2. Supporting Evidence: PMID:11544256 both Gat1p and Gat2p(Sct1p) are G-3-P/dihydroxyacetone phosphate dual substrate-specific sn-1 acyltransferases |
| GO:0004366 glycerol-3-phosphate O-acyltransferase activity | IDA PMID:11544256 The initial step of the glycerolipid pathway: identification... | ACCEPT | Summary: IDA from Zheng and Zou 2001; YKR067w (GAT1/GPT2) expressed in E. coli showed G3P acyltransferase activity. Supporting Evidence: PMID:11544256 Heterologous expression of YKR067w in Escherichia coli further confirmed its enzyme activity. PMID:11544256 both Gat1p and Gat2p(Sct1p) are G-3-P/dihydroxyacetone phosphate dual substrate-specific sn-1 acyltransferases |
| GO:0004366 glycerol-3-phosphate O-acyltransferase activity | IEA GO_REF:0000120 | ACCEPT | Summary: IEA from RHEA/EC 2.3.1.15 mapping derived from UniProt's GPAT reactions. Correct. Supporting Evidence: file:yeast/GPT2/GPT2-uniprot.txt Reaction=sn-glycerol 3-phosphate + an acyl-CoA = a 1-acyl-sn-glycero-3- |
| GO:0004366 glycerol-3-phosphate O-acyltransferase activity | IMP PMID:11544256 The initial step of the glycerolipid pathway: identification... | ACCEPT | Summary: IMP from Zheng and Zou 2001; gat1 disruption (and the TTA1 missense allele) sharply reduced cellular GPAT activity. Supporting Evidence: PMID:11544256 A yeast strain disrupted at the open reading frame YKR067w, which encodes a protein closely related to Sct1p, also exhibited a dramatic reduction in G-3-P acyltransferase activity. |
| GO:0004366 glycerol-3-phosphate O-acyltransferase activity | RCA GO_REF:0000123 | ACCEPT | Summary: YeastPathways RCA (PWY3O-6499, phosphatidate biosynthesis II, glycerol-3-phosphate pathway) assigning the G3P + acyl-CoA -> LPA step (EC 2.3.1.15) to Gpt2. Correct. Supporting Evidence: PMID:11544256 The initial step of phospholipid biosynthesis in yeast is carried out through the acylation of glycerol 3-phosphate (G-3-P) and dihydroxyacetone phosphate by stereospecific sn-1 acyltransferases. |
| GO:0004366 glycerol-3-phosphate O-acyltransferase activity | RCA GO_REF:0000123 | ACCEPT | Summary: YeastPathways RCA (superpathway of phosphatidate biosynthesis, PWY3O-6635) for the GPAT step. Correct. Supporting Evidence: PMID:11544256 The initial step of phospholipid biosynthesis in yeast is carried out through the acylation of glycerol 3-phosphate (G-3-P) and dihydroxyacetone phosphate by stereospecific sn-1 acyltransferases. |
| GO:0004366 glycerol-3-phosphate O-acyltransferase activity | RCA GO_REF:0000123 | ACCEPT | Summary: YeastPathways RCA (TRIGLSYN-PWY) for the GPAT step that begins de novo DAG/TAG synthesis. Correct. Supporting Evidence: PMID:11544256 both Gat1p and Gat2p(Sct1p) are G-3-P/dihydroxyacetone phosphate dual substrate-specific sn-1 acyltransferases PMID:22267742 We propose a model where Gat1p and Gat2p contribute differentially to channel fatty acids into TAG |
| GO:0005737 cytoplasm | HDA PMID:11914276 Subcellular localization of the yeast proteome. | KEEP AS NON CORE | Summary: HDA from the Kumar et al. 2002 immunolocalization survey scoring Gpt2 as cytoplasmic. Reason: Coarse; the ER is part of the cytoplasm, but ER membrane and lipid droplet are the informative locations. Supporting Evidence: PMID:11914276 By high-throughput immunolocalization of tagged gene products, we have determined the subcellular localization of 2744 yeast proteins. |
| GO:0005783 endoplasmic reticulum | HDA PMID:11914276 Subcellular localization of the yeast proteome. | ACCEPT | Summary: HDA from the Kumar et al. 2002 immunolocalization survey placing Gpt2 in the ER. Supporting Evidence: PMID:11914276 By high-throughput immunolocalization of tagged gene products, we have determined the subcellular localization of 2744 yeast proteins. PMID:19525420 Our results indicate Gat1p and Gat2p overlap mostly in their localization and are in fact microsomal GPATs, localized to both perinuclear and cortical endoplasmic reticula in actively proliferating cells. |
| GO:0005783 endoplasmic reticulum | HDA PMID:14562095 Global analysis of protein localization in budding yeast. | ACCEPT | Summary: HDA from the Huh et al. 2003 GFP survey (ER category). Supporting Evidence: PMID:14562095 expressing full-length, chromosomally tagged green fluorescent protein fusion proteins PMID:19525420 Our results indicate Gat1p and Gat2p overlap mostly in their localization and are in fact microsomal GPATs, localized to both perinuclear and cortical endoplasmic reticula in actively proliferating cells. |
| GO:0005783 endoplasmic reticulum | HDA PMID:26928762 One library to make them all: streamlining the creation of y... | ACCEPT | Summary: HDA from the SWAT N-terminal GFP endomembrane library (Yofe et al. 2016) (ER). Supporting Evidence: PMID:26928762 carrying SWAT-GFP modules at the amino termini of endomembrane proteins PMID:19525420 Our results indicate Gat1p and Gat2p overlap mostly in their localization and are in fact microsomal GPATs, localized to both perinuclear and cortical endoplasmic reticula in actively proliferating cells. |
| GO:0005783 endoplasmic reticulum | IBA GO_REF:0000033 | ACCEPT | Summary: PAINT IBA (is_active_in ER) for the fungal GPAT clade. Correct. Supporting Evidence: PMID:19525420 Our results indicate Gat1p and Gat2p overlap mostly in their localization and are in fact microsomal GPATs, localized to both perinuclear and cortical endoplasmic reticula in actively proliferating cells. |
| GO:0005783 endoplasmic reticulum | IDA PMID:19525420 Glycerol-3-phosphate acyltransferases gat1p and gat2p are mi... | ACCEPT | Summary: IDA from Bratschi et al. 2009; fluorescence microscopy and density-gradient fractionation show Gat1p in perinuclear and cortical ER. Supporting Evidence: PMID:19525420 Our results indicate Gat1p and Gat2p overlap mostly in their localization and are in fact microsomal GPATs, localized to both perinuclear and cortical endoplasmic reticula in actively proliferating cells. |
| GO:0005783 endoplasmic reticulum | IDA PMID:22267742 Controlling lipid fluxes at glycerol-3-phosphate acyltransfe... | ACCEPT | Summary: IDA from Marr et al. 2012; Gat1p localises to ER, forming oleate-induced crescents continuous with the ER. Supporting Evidence: PMID:22267742 These structures are connected with the endoplasmic reticulum and are intimately associated with LPs. |
| GO:0005783 endoplasmic reticulum | IDA PMID:9401016 Biosynthesis of phosphatidic acid in lipid particles and end... | ACCEPT | Summary: IDA from Athenstaedt and Daum 1997, who found GPAT activity in both lipid particles and ER, with the Gat1 (TTA1) mutation affecting it. Supporting Evidence: PMID:9401016 which harbors a point mutation in the GAT gene, are essentially devoid of glycerol-3-phosphate acyltransferase activity in vitro PMID:9401016 the first step, acylation of glycerol-3-phosphate, is catalyzed by a putative Gat1p |
| GO:0005789 endoplasmic reticulum membrane | EXP PMID:19525420 Glycerol-3-phosphate acyltransferases gat1p and gat2p are mi... | ACCEPT | Summary: SGD EXP from Bratschi et al. 2009 (ER membrane). Supporting Evidence: PMID:19525420 Our results indicate Gat1p and Gat2p overlap mostly in their localization and are in fact microsomal GPATs, localized to both perinuclear and cortical endoplasmic reticula in actively proliferating cells. |
| GO:0005789 endoplasmic reticulum membrane | EXP PMID:31421179 Phosphorylation of the lipid droplet localized glycerol‑3‑ph... | ACCEPT | Summary: SGD EXP from Kiegerl et al. 2019 (ER membrane, alongside lipid droplets). Supporting Evidence: PMID:31421179 the lipid droplet associated GPAT Gpt2 requires phosphorylation at a conserved motif to prevent a futile TAG cycle |
| GO:0005789 endoplasmic reticulum membrane | IEA GO_REF:0000044 | ACCEPT | Summary: IEA from UniProt subcellular location (SL-0097 ER membrane). Correct. Supporting Evidence: PMID:19525420 Our results indicate Gat1p and Gat2p overlap mostly in their localization and are in fact microsomal GPATs, localized to both perinuclear and cortical endoplasmic reticula in actively proliferating cells. |
| GO:0005811 lipid droplet | EXP PMID:31421179 Phosphorylation of the lipid droplet localized glycerol‑3‑ph... | ACCEPT | Summary: SGD EXP from Kiegerl et al. 2019, describing Gpt2 as a lipid droplet-associated GPAT. Supporting Evidence: PMID:31421179 the lipid droplet associated GPAT Gpt2 requires phosphorylation at a conserved motif to prevent a futile TAG cycle |
| GO:0005811 lipid droplet | IDA PMID:22267742 Controlling lipid fluxes at glycerol-3-phosphate acyltransfe... | ACCEPT | Summary: IDA from Marr et al. 2012; oleate-induced Gat1p crescents are intimately associated with lipid particles. Supporting Evidence: PMID:22267742 These structures are connected with the endoplasmic reticulum and are intimately associated with LPs. |
| GO:0005811 lipid droplet | IDA PMID:9401016 Biosynthesis of phosphatidic acid in lipid particles and end... | ACCEPT | Summary: IDA from Athenstaedt and Daum 1997; lipid particles of the GAT-mutant TTA1 strain lack GPAT activity, implying Gat1 acts in lipid particles. Supporting Evidence: PMID:9401016 which harbors a point mutation in the GAT gene, are essentially devoid of glycerol-3-phosphate acyltransferase activity in vitro PMID:9401016 the first step, acylation of glycerol-3-phosphate, is catalyzed by a putative Gat1p |
| GO:0005811 lipid droplet | IEA GO_REF:0000044 | ACCEPT | Summary: IEA from UniProt subcellular location (SL-0154 lipid droplet). Correct. Supporting Evidence: PMID:31421179 the lipid droplet associated GPAT Gpt2 requires phosphorylation at a conserved motif to prevent a futile TAG cycle |
| GO:0005829 cytosol | RCA GO_REF:0000123 | REMOVE | Summary: YeastPathways RCA rows (PWY3O-6407, PWY3O-6499, PWY3O-6635, TRIGLSYN-PWY) placing the GPAT/DHAPAT step in the cytosol. Gpt2 is a multi-pass ER membrane protein that also associates with lipid droplets. Reason: The cytosol location is a pathway default that contradicts the established ER/lipid droplet localisation of this membrane enzyme. Supporting Evidence: PMID:19525420 Our results indicate Gat1p and Gat2p overlap mostly in their localization and are in fact microsomal GPATs, localized to both perinuclear and cortical endoplasmic reticula in actively proliferating cells. |
| GO:0005829 cytosol | RCA GO_REF:0000123 | REMOVE | Summary: YeastPathways RCA rows (PWY3O-6407, PWY3O-6499, PWY3O-6635, TRIGLSYN-PWY) placing the GPAT/DHAPAT step in the cytosol. Gpt2 is a multi-pass ER membrane protein that also associates with lipid droplets. Reason: The cytosol location is a pathway default that contradicts the established ER/lipid droplet localisation of this membrane enzyme. Supporting Evidence: PMID:19525420 Our results indicate Gat1p and Gat2p overlap mostly in their localization and are in fact microsomal GPATs, localized to both perinuclear and cortical endoplasmic reticula in actively proliferating cells. |
| GO:0005829 cytosol | RCA GO_REF:0000123 | REMOVE | Summary: YeastPathways RCA rows (PWY3O-6407, PWY3O-6499, PWY3O-6635, TRIGLSYN-PWY) placing the GPAT/DHAPAT step in the cytosol. Gpt2 is a multi-pass ER membrane protein that also associates with lipid droplets. Reason: The cytosol location is a pathway default that contradicts the established ER/lipid droplet localisation of this membrane enzyme. Supporting Evidence: PMID:19525420 Our results indicate Gat1p and Gat2p overlap mostly in their localization and are in fact microsomal GPATs, localized to both perinuclear and cortical endoplasmic reticula in actively proliferating cells. |
| GO:0005829 cytosol | RCA GO_REF:0000123 | REMOVE | Summary: YeastPathways RCA rows (PWY3O-6407, PWY3O-6499, PWY3O-6635, TRIGLSYN-PWY) placing the GPAT/DHAPAT step in the cytosol. Gpt2 is a multi-pass ER membrane protein that also associates with lipid droplets. Reason: The cytosol location is a pathway default that contradicts the established ER/lipid droplet localisation of this membrane enzyme. Supporting Evidence: PMID:19525420 Our results indicate Gat1p and Gat2p overlap mostly in their localization and are in fact microsomal GPATs, localized to both perinuclear and cortical endoplasmic reticula in actively proliferating cells. |
| GO:0006644 phospholipid metabolic process | IEA GO_REF:0000117 | TOO GENERAL | Summary: IEA from ARBA rule ARBA00028721 for phospholipid metabolic process. Correct but general. Supporting Evidence: PMID:11544256 The initial step of phospholipid biosynthesis in yeast is carried out through the acylation of glycerol 3-phosphate (G-3-P) and dihydroxyacetone phosphate by stereospecific sn-1 acyltransferases. |
| GO:0006654 phosphatidic acid biosynthetic process | RCA GO_REF:0000123 | ACCEPT | Summary: YeastPathways RCA (PWY3O-6635) for phosphatidic acid biosynthetic process. Gpt2 makes LPA, the direct precursor of PA, and gat1 cells have a reduced PA pool. Supporting Evidence: PMID:11544256 The initial step of phospholipid biosynthesis in yeast is carried out through the acylation of glycerol 3-phosphate (G-3-P) and dihydroxyacetone phosphate by stereospecific sn-1 acyltransferases. PMID:11544256 The most notable of the altered phospholipid compositions of the gat1Delta and gat2(sct1)Delta strains are a decreased phosphatidic acid pool |
| GO:0008654 phospholipid biosynthetic process | IBA GO_REF:0000033 | ACCEPT | Summary: PAINT IBA for phospholipid biosynthetic process at the fungal GPAT node. Correct. Supporting Evidence: PMID:11544256 The initial step of phospholipid biosynthesis in yeast is carried out through the acylation of glycerol 3-phosphate (G-3-P) and dihydroxyacetone phosphate by stereospecific sn-1 acyltransferases. |
| GO:0008654 phospholipid biosynthetic process | IDA PMID:11544256 The initial step of the glycerolipid pathway: identification... | ACCEPT | Summary: IDA from Zheng and Zou 2001 for phospholipid biosynthesis (in vitro acylation of G3P and DHAP by Gat1). Supporting Evidence: PMID:11544256 both Gat1p and Gat2p(Sct1p) are G-3-P/dihydroxyacetone phosphate dual substrate-specific sn-1 acyltransferases |
| GO:0008654 phospholipid biosynthetic process | IMP PMID:11544256 The initial step of the glycerolipid pathway: identification... | ACCEPT | Summary: IMP from Zheng and Zou 2001; gat1 deletion altered phospholipid composition, with a smaller PA pool. Supporting Evidence: PMID:11544256 The most notable of the altered phospholipid compositions of the gat1Delta and gat2(sct1)Delta strains are a decreased phosphatidic acid pool |
| GO:0008654 phospholipid biosynthetic process | RCA GO_REF:0000123 | ACCEPT | Summary: YeastPathways RCA (PWY3O-6407 DHAP pathway; PWY3O-6499 G3P pathway) for phospholipid biosynthetic process; Gpt2 catalyses the first acylation in both routes. Supporting Evidence: PMID:11544256 The initial step of phospholipid biosynthesis in yeast is carried out through the acylation of glycerol 3-phosphate (G-3-P) and dihydroxyacetone phosphate by stereospecific sn-1 acyltransferases. |
| GO:0008654 phospholipid biosynthetic process | RCA GO_REF:0000123 | ACCEPT | Summary: YeastPathways RCA (PWY3O-6407 DHAP pathway; PWY3O-6499 G3P pathway) for phospholipid biosynthetic process; Gpt2 catalyses the first acylation in both routes. Supporting Evidence: PMID:11544256 The initial step of phospholipid biosynthesis in yeast is carried out through the acylation of glycerol 3-phosphate (G-3-P) and dihydroxyacetone phosphate by stereospecific sn-1 acyltransferases. |
| GO:0016024 CDP-diacylglycerol biosynthetic process | IEA GO_REF:0000041 | ACCEPT | Summary: IEA from UniPathway UPA00557 (CDP-diacylglycerol from sn-glycerol 3-phosphate, step 1/3). Gpt2 catalyses that first step. Supporting Evidence: file:yeast/GPT2/GPT2-uniprot.txt PATHWAY: Phospholipid metabolism; CDP-diacylglycerol biosynthesis; CDP- |
| GO:0016287 glycerone-phosphate O-acyltransferase activity | IBA GO_REF:0000033 | ACCEPT | Summary: PAINT IBA for glycerone-phosphate O-acyltransferase activity at the fungal GPAT node. Correct; both yeast GPATs are dual-substrate. Supporting Evidence: PMID:11544256 both Gat1p and Gat2p(Sct1p) are G-3-P/dihydroxyacetone phosphate dual substrate-specific sn-1 acyltransferases |
| GO:0016287 glycerone-phosphate O-acyltransferase activity | IDA PMID:11544256 The initial step of the glycerolipid pathway: identification... | ACCEPT | Summary: IDA from Zheng and Zou 2001; Gat1p acylates DHAP as well as G3P. Supporting Evidence: PMID:11544256 both Gat1p and Gat2p(Sct1p) are G-3-P/dihydroxyacetone phosphate dual substrate-specific sn-1 acyltransferases |
| GO:0016287 glycerone-phosphate O-acyltransferase activity | IEA GO_REF:0000120 | ACCEPT | Summary: IEA from RHEA/EC 2.3.1.42 mapping derived from UniProt's DHAP acyltransferase reaction. Correct. Supporting Evidence: file:yeast/GPT2/GPT2-uniprot.txt Reaction=dihydroxyacetone phosphate + an acyl-CoA = a 1-acylglycerone |
| GO:0016287 glycerone-phosphate O-acyltransferase activity | RCA GO_REF:0000123 | ACCEPT | Summary: YeastPathways RCA (PWY3O-6407 DHAP pathway; PWY3O-6635 superpathway) assigning the DHAP + acyl-CoA -> 1-acyl-DHAP step (EC 2.3.1.42) to Gpt2. Supported by the dual-substrate activity. Supporting Evidence: PMID:11544256 both Gat1p and Gat2p(Sct1p) are G-3-P/dihydroxyacetone phosphate dual substrate-specific sn-1 acyltransferases |
| GO:0016287 glycerone-phosphate O-acyltransferase activity | RCA GO_REF:0000123 | ACCEPT | Summary: YeastPathways RCA (PWY3O-6407 DHAP pathway; PWY3O-6635 superpathway) assigning the DHAP + acyl-CoA -> 1-acyl-DHAP step (EC 2.3.1.42) to Gpt2. Supported by the dual-substrate activity. Supporting Evidence: PMID:11544256 both Gat1p and Gat2p(Sct1p) are G-3-P/dihydroxyacetone phosphate dual substrate-specific sn-1 acyltransferases |
| GO:0016746 acyltransferase activity | IEA GO_REF:0000002 | TOO GENERAL | Summary: IEA from InterPro IPR002123 (phospholipid/glycerol acyltransferase domain) for acyltransferase activity. Correct but general. Supporting Evidence: file:yeast/GPT2/GPT2-uniprot.txt SIMILARITY: Belongs to the GPAT/DAPAT family. |
| GO:0019432 triglyceride biosynthetic process | RCA GO_REF:0000123 | ACCEPT | Summary: YeastPathways RCA (TRIGLSYN-PWY) for triglyceride biosynthetic process. GPAT makes the first intermediate of de novo TAG synthesis, and Gat1 is required to channel oleate into TAG and lipid particles. Supporting Evidence: PMID:22267742 Yeast lacking Gat1p (but not Gat2p) were sensitive to oleate and failed to accumulate LPs induced by this unsaturated fatty acid. PMID:22267742 We propose a model where Gat1p and Gat2p contribute differentially to channel fatty acids into TAG |
| GO:0090207 regulation of triglyceride metabolic process | IMP PMID:31421179 Phosphorylation of the lipid droplet localized glycerol‑3‑ph... | MARK AS OVER ANNOTATED | Summary: IMP from Kiegerl et al. 2019 for regulation of triglyceride metabolic process. Mutating the phosphorylation motif of Gpt2 raised its activity and sustained TAG synthesis during lipolysis. Reason: The paper shows that Gpt2 itself is regulated (by phosphorylation); it does not show Gpt2 regulating TAG metabolism other than through its own GPAT activity. The effect on TAG levels is already captured by the GPAT MF and the TAG/phospholipid biosynthesis BPs. Being a regulated enzyme is not the same as regulating a process. Supporting Evidence: PMID:31421179 Phosphorylation deficiency at the conserved motif increases the enzyme activity of Gpt2 and consequently enhances TAG synthesis. PMID:31421179 These data strongly indicate that phosphorylation of Gpt2 at a conserved motif plays a critical role in coordinating the synthesis and degradation of TAGs. |
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Download this section (compressed HTML)Q: Which kinase(s) phosphorylate the conserved C-terminal motif of Gpt2, and how is this coordinated with TAG lipolysis by Tgl3/Tgl4?
Q: What determines the different fatty-acid channelling of Gpt2 (oleate, broad acyl-CoA use) and Sct1 (C16 preference, de novo fatty acids) into TAG versus phospholipids?
Experiment: Phosphoproteomics of Gpt2 after kinase deletions (e.g. Ypk1/Ypk2, Pho85) during lipolysis, combined with TAG turnover assays in phospho-site mutants.
Hypothesis: A specific lipolysis-activated kinase phosphorylates Gpt2 to prevent futile TAG cycling.
Type: phosphoproteomics/genetics
Glycerol-3-phosphate/dihydroxyacetone phosphate sn-1 acyltransferase; located in lipid particles and the ER; involved in the stepwise acylation of glycerol-3-phosphate and dihydroxyacetone in lipid biosynthesis; the most conserved motifs and functionally relevant residues are oriented towards the ER lumen
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