YAT1 encodes one of the three carnitine O-acetyltransferases (EC 2.3.1.7) of Saccharomyces cerevisiae, together with CAT2 and YAT2. These enzymes reversibly transfer acetyl groups between acetyl-CoA and L-carnitine, producing acetylcarnitine that can cross organellar membranes as part of the carnitine shuttle. Yat1p is a 78 kDa mitochondrial protein without a cleavable presequence. It was proposed to sit at the outer mitochondrial membrane, while UniProt lists it as peripheral to the inner membrane (intermembrane-space side). Expression is low on glucose and strongly induced by ethanol or acetate. Deleting YAT1 alone has little effect, but in a strain lacking the glyoxylate-cycle citrate synthase CIT2, all three carnitine acetyltransferases and L-carnitine become essential for growth on non-fermentable carbon sources. This points to a non-redundant role for Yat1p in moving acetyl units into mitochondria.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0004092 carnitine O-acetyltransferase activity | IBA GO_REF:0000033 | ACCEPT | Summary: IBA from PTN001097079 (carnitine acetyltransferase clade, PTHR22589), with SGD YAT2 as an experimental descendant. Yat1p has carnitine acetyltransferase activity (mitochondrial CAT activity is reduced in yat1 deletion) and complements a CAT-deficient mutant. Correct. Supporting Evidence: file:yeast/YAT1/YAT1-uniprot.txt Reaction=(R)-carnitine + acetyl-CoA = O-acetyl-(R)-carnitine + CoA; PMID:8262985 Carnitine acetyltransferase activities of intact mitochondria from a YAT1 deletion mutant are slightly lower than wild type PMID:11329169 YAT1, coding for the carnitine acetyltransferase, which is presumably associated with the outer mitochondrial membrane, and YER024w (YAT2), which encodes a third, previously unidentified carnitine acetyltransferase |
| GO:0004092 carnitine O-acetyltransferase activity | IEA GO_REF:0000120 | ACCEPT | Summary: Combined IEA from RHEA:21136 and EC 2.3.1.7. This is the correct acetyl-specific carnitine acyltransferase reaction. Supporting Evidence: file:yeast/YAT1/YAT1-uniprot.txt Reaction=(R)-carnitine + acetyl-CoA = O-acetyl-(R)-carnitine + CoA; |
| GO:0004092 carnitine O-acetyltransferase activity | RCA GO_REF:0000123 | ACCEPT | Summary: YeastPathways RCA from PWY3O-4 (carnitine shuttle) for L-carnitine + acetyl-CoA <-> O-acetyl-L-carnitine + CoA. This is the Yat1p reaction, supported by genetic and enzymatic data. Supporting Evidence: file:yeast/YAT1/YAT1-uniprot.txt Reaction=(R)-carnitine + acetyl-CoA = O-acetyl-(R)-carnitine + CoA; PMID:11329169 YAT1, coding for the carnitine acetyltransferase, which is presumably associated with the outer mitochondrial membrane, and YER024w (YAT2), which encodes a third, previously unidentified carnitine acetyltransferase PMID:8262985 Carnitine acetyltransferase activities of intact mitochondria from a YAT1 deletion mutant are slightly lower than wild type |
| GO:0004095 carnitine O-palmitoyltransferase activity | ISS PMID:8262985 The ethanol-inducible YAT1 gene from yeast encodes a presump... | MODIFY | Summary: ISS to rat CPT2 (P18886), citing Schmalix and Bandlow, who noted similarity to vertebrate carnitine acyltransferases. Sequence similarity across the carnitine/choline acyltransferase family does not establish palmitoyl (long-chain) specificity. The activity actually measured for Yat1p is carnitine acetyltransferase, and the yeast carnitine shuttle is described for acetyl units only. The essence (carnitine acyltransferase) is right but the acyl-chain specificity is wrong, so this is replaced with carnitine O-acetyltransferase activity. Proposed replacements: carnitine O-acetyltransferase activity Supporting Evidence: PMID:8262985 displays significant sequence similarity to vertebrate L-carnitine acyltransferases and yeast inner mitochondrial L-carnitine acetyltransferase PMID:8262985 Carnitine acetyltransferase activities of intact mitochondria from a YAT1 deletion mutant are slightly lower than wild type PMID:11329169 In a reversible reaction catalysed by carnitine acetyltransferases (CATs), activated acetyl groups are transferred to carnitine to form acetylcarnitine which can be shuttled across membranes. |
| GO:0005515 protein binding | IPI PMID:18719252 High-quality binary protein interaction map of the yeast int... | REMOVE | Summary: Yu et al. binary Y2H with YAT2 (P40017). The YAT1-YAT2 association was found again independently by AP-MS (PMID:37968396), which suggests the two CATs could form a hetero-complex, but this is untested. 'protein binding' is uninformative and no specific MF term is supported, so the row is removed; removal does not mean the interaction is false. Supporting Evidence: PMID:18719252 high-throughput yeast two-hybrid (Y2H) screening provides high-quality binary interaction information file:yeast/YAT1/YAT1-uniprot.txt P80235; P40017: YAT2; NbExp=2; IntAct=EBI-3928, EBI-2345299; |
| GO:0005515 protein binding | IPI PMID:37968396 The social and structural architecture of the yeast protein ... | REMOVE | Summary: Michaelis et al. proteome-wide affinity-enrichment MS with YAT2 (P40017). This is reproducible with the Y2H data, but its functional significance is unknown. Removed as an uninformative protein-binding row; the interaction itself is not disputed. Supporting Evidence: PMID:37968396 high-throughput method using highly reproducible affinity enrichment coupled to file:yeast/YAT1/YAT1-uniprot.txt P80235; P40017: YAT2; NbExp=2; IntAct=EBI-3928, EBI-2345299; |
| GO:0005739 mitochondrion | HDA PMID:11914276 Subcellular localization of the yeast proteome. | ACCEPT | Summary: Kumar et al. genome-wide immunolocalisation placed Yat1p in mitochondria. This is consistent with targeted fractionation (PMID:8262985, PMID:18427809). Supporting Evidence: PMID:11914276 By high-throughput immunolocalization of tagged gene products, we have determined the subcellular localization of 2744 yeast proteins. PMID:8262985 recognizes a protein of 78-kDa molecular mass in the mitochondrial fraction from yeast |
| GO:0005739 mitochondrion | HDA PMID:14576278 The proteome of Saccharomyces cerevisiae mitochondria. | ACCEPT | Summary: Sickmann et al. MS proteome of highly purified mitochondria detected Yat1p. This is consistent with its known mitochondrial location. Supporting Evidence: PMID:14576278 We performed a comprehensive approach to determine the proteome of Saccharomyces cerevisiae mitochondria. PMID:8262985 recognizes a protein of 78-kDa molecular mass in the mitochondrial fraction from yeast |
| GO:0005739 mitochondrion | HDA PMID:16823961 Toward the complete yeast mitochondrial proteome: multidimen... | ACCEPT | Summary: Reinders et al. PROMITO mitochondrial proteome detected Yat1p. This is consistent with targeted studies. Supporting Evidence: PMID:16823961 A total of 851 different proteins (PROMITO dataset) were identified PMID:8262985 recognizes a protein of 78-kDa molecular mass in the mitochondrial fraction from yeast |
| GO:0005739 mitochondrion | IBA GO_REF:0000033 | ACCEPT | Summary: IBA (PTN001097079), with CAT2 as a donor. A mitochondrial location is experimentally confirmed for Yat1p. Supporting Evidence: PMID:8262985 recognizes a protein of 78-kDa molecular mass in the mitochondrial fraction from yeast |
| GO:0005739 mitochondrion | IDA PMID:18427809 Carnitine and carnitine acetyltransferases in the yeast Sacc... | ACCEPT | Summary: Franken et al. localised the three yeast CATs. Yat1p is mitochondrial (abstract-only cache; the curator's IDA is consistent with the earlier fractionation data). Supporting Evidence: PMID:18427809 In yeast, the shuttle transfers peroxisomal activated acetyl-residues to the mitochondria. PMID:8262985 recognizes a protein of 78-kDa molecular mass in the mitochondrial fraction from yeast |
| GO:0005743 mitochondrial inner membrane | IEA GO_REF:0000044 | UNDECIDED | Summary: UniProt SubCell mapping (inner membrane, peripheral, intermembrane side). Schmalix and Bandlow instead concluded that Yat1p is a presumptive outer-membrane CAT: it lacks a presequence and binds mitochondria in a protease-sensitive location. Its sub-mitochondrial location is therefore unresolved. Mitochondrion is secure, but which membrane it is on cannot be decided from the available evidence. Supporting Evidence: file:yeast/YAT1/YAT1-uniprot.txt SUBCELLULAR LOCATION: Mitochondrion inner membrane; Peripheral membrane PMID:8262985 likely to code for a minor mitochondrial outer carnitine acetyltransferase |
| GO:0005829 cytosol | RCA GO_REF:0000123 | REMOVE | Summary: YeastPathways RCA from PWY3O-4 assigns the CAT reaction of all three CATs to the cytosol. The cytosolic CAT is Yat2p; Yat1p is a mitochondrial protein (fractionation, proteomics, IDA). This compartment, inherited from the pathway, is wrong for Yat1p. Supporting Evidence: PMID:8262985 recognizes a protein of 78-kDa molecular mass in the mitochondrial fraction from yeast PMID:11329169 YAT1, coding for the carnitine acetyltransferase, which is presumably associated with the outer mitochondrial membrane, and YER024w (YAT2), which encodes a third, previously unidentified carnitine acetyltransferase |
| GO:0006853 carnitine shuttle | RCA GO_REF:0000123 | ACCEPT | Summary: YeastPathways RCA from PWY3O-4 (carnitine shuttle). Yat1p catalyses the acetyl transfer step of the shuttle, and together with CAT2 and YAT2 it is required for carnitine-dependent growth in a cit2 background. It does part of the work of the process. Supporting Evidence: PMID:11329169 In a reversible reaction catalysed by carnitine acetyltransferases (CATs), activated acetyl groups are transferred to carnitine to form acetylcarnitine which can be shuttled across membranes. PMID:11329169 L-carnitine and all three CATs are essential for growth on non-fermentable carbon sources in a strain with a disrupted CIT2 gene file:yeast/YAT1/YAT1-uniprot.txt FUNCTION: Involved in the transfer of acetyl-CoA into mitochondria. May |
| GO:0009437 carnitine metabolic process | IBA GO_REF:0000033 | ACCEPT | Summary: IBA (PTN001097079) carnitine metabolic process. Yat1p acetylates and deacetylates carnitine, which is carnitine metabolism. Correct, though the carnitine shuttle is the more functionally specific process. Supporting Evidence: file:yeast/YAT1/YAT1-uniprot.txt Reaction=(R)-carnitine + acetyl-CoA = O-acetyl-(R)-carnitine + CoA; |
| GO:0009437 carnitine metabolic process | IMP PMID:11329169 Carnitine-dependent metabolic activities in Saccharomyces ce... | ACCEPT | Summary: Swiegers et al.: yat1 mutants were recovered in a selection for loss of carnitine-dependent metabolic activities, and YAT1 is essential for carnitine-dependent growth in a cit2 strain. Yat1p performs the carnitine acetylation step. Supporting Evidence: PMID:11329169 L-carnitine and all three CATs are essential for growth on non-fermentable carbon sources in a strain with a disrupted CIT2 gene PMID:11329169 YAT1, coding for the carnitine acetyltransferase, which is presumably associated with the outer mitochondrial membrane, and YER024w (YAT2), which encodes a third, previously unidentified carnitine acetyltransferase |
| GO:0016746 acyltransferase activity | IEA GO_REF:0000002 | MODIFY | Summary: InterPro IPR000542 (carnitine/choline acyltransferase) mapping to the generic acyltransferase term. The specific activity is carnitine O-acetyltransferase. Proposed replacements: carnitine O-acetyltransferase activity Supporting Evidence: file:yeast/YAT1/YAT1-uniprot.txt Reaction=(R)-carnitine + acetyl-CoA = O-acetyl-(R)-carnitine + CoA; |
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Download this section (compressed HTML)Q: Is Yat1p associated with the outer mitochondrial membrane (as proposed by Schmalix and Bandlow) or peripheral to the inner membrane on the IMS side (as annotated in UniProt)?
Q: Do Yat1p and Yat2p form a functional hetero-complex, as suggested by reproducible Y2H and AP-MS interactions?
Experiment: Protease protection and carbonate extraction of isolated mitochondria and mitoplasts with epitope-tagged Yat1p, with Tom70/Tim44/Cyb2 as compartment markers.
Hypothesis: Yat1p is anchored on the cytosolic face of the outer mitochondrial membrane
Type: biochemical fractionation
Outer mitochondrial carnitine acetyltransferase; minor ethanol-inducible enzyme involved in transport of activated acyl groups from the cytoplasm into the mitochondrial matrix; phosphorylated
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