The research report should be a detailed narrative explaining the function, biological processes, and localization of the gene product. Citations should be given for all claims.
You should prioritize authoritative reviews and primary scientific literature when conducting research. You can supplement
this with annotations you find in gene/protein databases, but these can be outdated or inaccurate.
We are specifically interested in the primary function of the gene - for enzymes, what reaction is catalyzed, and what is the substrate specificity? For transporters, what is the substrate? For structural proteins or adapters, what is the broader structural role? For signaling molecules, what is the role in the pathway.
We are interested in where in or outside the cell the gene product carries out its function.
We are also interested in the signaling or biochemical pathways in which the gene functions. We are less interested in broad pleiotropic effects, except where these elucidate the precise role.
Include evidence where possible. We are interested in both experimental evidence as well as inference from structure, evolution, or bioinformatic analysis. Precise studies should be prioritized over high-throughput, where available.
The gene symbol acn1 corresponds to the systematic ORF name SPBC3H7.05c in the fission yeast Schizosaccharomyces pombe (strain 972 / ATCC 24843), encoding UniProt accession O74380. UniProt describes this protein as "Uncharacterized membrane protein C3H7.05c." Extensive literature searches did not identify any primary research articles that have directly characterized the function, enzymatic activity, or biological role of acn1/SPBC3H7.05c. No gene symbol ambiguity was identified—there is no well-characterized gene with the symbol "acn1" in another organism that would cause confusion. The functional annotation presented below is therefore primarily inferred from domain architecture and homology to characterized members of the MBOAT (membrane-bound O-acyltransferase) superfamily.
| Property | Details |
|---|---|
| Gene Name | acn1 / SPBC3H7.05c; corresponds to the S. pombe ORF encoding an uncharacterized membrane protein in UniProt (holic2020metabolismofphospholipids pages 1-4) |
| Organism | Schizosaccharomyces pombe (fission yeast) (holic2020metabolismofphospholipids pages 1-4) |
| UniProt Accession | O74380 (user-supplied target identifier; direct literature characterization not found) |
| Protein Domains | Wax_synthase_dom (IPR032805) and MBOAT_2 (PF13813), consistent with a membrane-bound O-acyltransferase-type protein; MBOAT proteins are integral membrane acyltransferases with conserved catalytic features (pierce2023arisingtide pages 2-4, chang2011membraneboundoacyltransferases(mboats) pages 1-3, cheng2022heterologousexpressionand pages 1-2) |
| Predicted Function | Acyl-CoA-dependent acyltransferase, most likely involved in neutral lipid biosynthesis or lipid remodeling by analogy to MBOAT-family DGAT1/WS enzymes (pierce2023arisingtide pages 2-4, pierce2023arisingtide pages 1-2, chang2011membraneboundoacyltransferases(mboats) pages 1-3, cheng2022heterologousexpressionand pages 1-2) |
| Predicted Reaction | Likely transfer of an acyl group from acyl-CoA to a lipid or fatty alcohol acceptor; plausible activities include diacylglycerol acyltransferase-like or wax synthase-like reactions based on domain content and homologous enzyme chemistry (cheng2022heterologousexpressionand pages 1-2, turkish2009thegeneticsof pages 3-4, chang2011membraneboundoacyltransferases(mboats) pages 1-3, cheng2022heterologousexpressionand pages 13-15) |
| Predicted Localization | Most likely an integral membrane protein of the endoplasmic reticulum (ER); MBOAT/DGAT1 enzymes commonly localize to ER membranes, and neutral lipid synthesis in S. pombe is ER-linked (chang2011membraneboundoacyltransferases(mboats) pages 3-4, chang2011membraneboundoacyltransferases(mboats) pages 1-3, cheng2022heterologousexpressionand pages 9-11, meyers2017theproteinand pages 9-13) |
| Known Pathway Context | Best placed in neutral lipid biosynthesis context in S. pombe, where dga1 and plh1 catalyze terminal TAG synthesis and lipid droplets store TAG and sterol esters; acn1 may represent an additional uncharacterized acyltransferase in this broader lipid-metabolic network (zhang2003schizosaccharomycespombecells pages 2-4, holic2020metabolismofphospholipids pages 24-26, meyers2017theproteinand pages 9-13) |
| Evidence Type | Domain-based inference only; no direct primary literature function, localization, or biochemical characterization was identified for acn1/SPBC3H7.05c specifically (holic2020metabolismofphospholipids pages 1-4, holic2020metabolismofphospholipids pages 4-6) |
| Protein Family | MBOAT (membrane-bound O-acyltransferase) superfamily, whose members catalyze acyl transfer reactions on diverse lipid substrates and typically contain multiple transmembrane segments (pierce2023arisingtide pages 2-4, chang2011membraneboundoacyltransferases(mboats) pages 1-3, pierce2023arisingtide pages 1-2) |
Table: This table summarizes the verified identity, domain architecture, and evidence-based functional inferences for the uncharacterized S. pombe protein acn1/SPBC3H7.05c. It is useful because direct experimental studies are lacking, so the most reliable interpretation comes from domain composition and comparison with characterized MBOAT-family enzymes.
The acn1 gene product contains two key domains: the MBOAT_2 domain (Pfam PF13813) and the Wax_synthase_dom (InterPro IPR032805). Both domains place this protein firmly within the membrane-bound O-acyltransferase (MBOAT) superfamily, first identified by Hofmann in 2000. The MBOAT superfamily encompasses a diverse group of integral membrane enzymes that share conserved features including multiple transmembrane domains and catalytically essential histidine and asparagine residues in the active site (pierce2023arisingtide pages 2-4, chang2011membraneboundoacyltransferases(mboats) pages 1-3). These enzymes catalyze acylation reactions on diverse substrates—including cholesterol, diacylglycerol, phospholipids, peptides, and proteins—using acyl-CoA thioesters as acyl donors (pierce2023arisingtide pages 1-2).
The MBOAT family is divided into three functional subgroups based on substrate specificity: (1) enzymes that acylate the hydroxyl groups of cholesterol or diacylglycerol (including ACAT/SOAT and DGAT1); (2) enzymes that acylate amino acid residues in proteins or peptide hormones (including PORCN, HHAT, and GOAT); and (3) enzymes that acylate lysophospholipids to reform phospholipids (including LPCAT, LPIAT/MBOAT7) (chang2011membraneboundoacyltransferases(mboats) pages 1-3, chang2011membraneboundoacyltransferases(mboats) pages 3-4).
The presence of the wax synthase domain (IPR032805) is particularly informative. Wax synthase (WS) enzymes are a class of MBOAT-type proteins that catalyze the formation of wax esters through the acylation of fatty alcohols with fatty acyl-CoA substrates (cheng2022heterologousexpressionand pages 1-2). Characterized plant WS enzymes are relatively small integral membrane proteins of 333–351 amino acid residues with seven or eight predicted transmembrane spanning domains and approximately 50% sequence identity with the well-characterized jojoba WS (cheng2022heterologousexpressionand pages 2-3). These enzymes exhibit broad substrate specificity, capable of assembling not only wax esters but also ethyl and benzyl esters (cheng2022heterologousexpressionand pages 17-19, cheng2022heterologousexpressionand pages 13-15).
DGAT1, a closely related MBOAT member, catalyzes the transfer of acyl groups from acyl-CoA to diacylglycerol to form triacylglycerols (TAG) and shares 15–25% amino acid sequence identity with ACATs (liu2011functionalandtopological pages 30-36). DGAT1 belongs to the same MBOAT superfamily and contains multiple transmembrane domains with a conserved histidine residue essential for catalytic function (pierce2023arisingtide pages 1-2, chang2011membraneboundoacyltransferases(mboats) pages 1-3). The combination of the MBOAT_2 and Wax_synthase_dom domains in acn1 strongly suggests that this protein functions as an acyl-CoA-dependent acyltransferase, most likely catalyzing the transfer of acyl chains from acyl-CoA to lipid or fatty alcohol acceptor substrates. The predicted reaction is most consistent with wax ester synthase and/or diacylglycerol acyltransferase activity.
To contextualize acn1, it is essential to consider the known enzymes of neutral lipid biosynthesis in S. pombe. Zhang et al. (2003) demonstrated that two gene products, Plh1p (a phospholipid:diacylglycerol acyltransferase homologous to S. cerevisiae LRO1) and Dga1p (an acyl-CoA:diacylglycerol acyltransferase homologous to human DGAT2), are responsible for the terminal step of triacylglycerol (TAG) synthesis in S. pombe (zhang2003schizosaccharomycespombecells pages 2-4). Deletion of plh1 alone reduces TAG synthesis by approximately 50%, and double deletion of both plh1 and dga1 results in near-total loss of TAG synthesis. Additionally, S. pombe contains two proteins homologous to S. cerevisiae Are1p and Are2p that catalyze sterol esterification (zhang2003schizosaccharomycespombecells pages 2-4).
Notably, dga1 is a DGAT2-family member, which is structurally unrelated to DGAT1/MBOAT-type enzymes. The acn1 gene product, with its MBOAT_2 and wax synthase domains, represents a distinct class of acyltransferase from the known Dga1p and Plh1p enzymes. It may therefore represent an additional, as-yet-uncharacterized acyltransferase in the S. pombe neutral lipid biosynthetic network—potentially functioning as a DGAT1-type enzyme or wax ester synthase.
In S. pombe, neutral lipids are stored in lipid droplets composed primarily of sterol esters (SEs) and triacylglycerols (TAGs), with SE:TAG ratios varying from 36:64 to 56:44 depending on growth conditions (meyers2017theproteinand pages 9-13). Key lipid droplet-associated proteins include Erg6p (delta-sterol C-methyltransferase), Erg1p (squalene monooxygenase), and Lcf1p (fatty acid-CoA ligase), along with the TAG lipases Ptl1p, Ptl2p, and Ptl3p (meyers2017theproteinand pages 13-17). The acn1 gene product, if it indeed functions as an acyltransferase in neutral lipid synthesis, would likely contribute to the production of these storage lipids.
S. pombe phospholipid metabolism uses pathways similar to those in S. cerevisiae, with three gene products—Ale1 (SPBC16A3.10), Slc1 (SPAC1851.02), and Vps66 (SPAC1783.02c)—predicted to possess acylglycerol acyltransferase activities based on homology (holic2020metabolismofphospholipids pages 13-15). The acn1 protein is distinct from these enzymes in its domain architecture but may participate in related acyl-CoA-dependent lipid modification pathways.
No direct experimental evidence exists for the subcellular localization of the acn1 gene product. However, inference from characterized MBOAT family members provides strong predictions. DGAT1 is an ER-resident enzyme (chang2011membraneboundoacyltransferases(mboats) pages 3-4), and ACAT1 functions to protect against excess cholesterol accumulation in ER membranes (chang2011membraneboundoacyltransferases(mboats) pages 1-3). The Arabidopsis wax synthase MBOAT enzymes localize to extra-plastidial membrane systems including the endoplasmic reticulum and plasma membrane (cheng2022heterologousexpressionand pages 9-11, cheng2022heterologousexpressionand pages 2-3). In S. pombe, neutral lipid synthesis occurs at the ER, with lipid droplets budding from ER membranes. Based on these considerations, acn1 is predicted to be an integral membrane protein of the endoplasmic reticulum (ER), consistent with its multiple predicted transmembrane domains and MBOAT family membership.
The MBOAT superfamily has been extensively characterized at the structural level in recent years. All MBOAT members share a central core fold containing a catalytically essential histidine residue embedded within transmembrane domains, and a conserved asparagine residue in a hydrophilic region (chang2011membraneboundoacyltransferases(mboats) pages 1-3, pierce2023arisingtide pages 7-8). The first experimentally determined MBOAT structure (DltB from bacteria) revealed conserved structural features including ring-shaped or funnel-like transmembrane arrangements and channels connecting the lumen to the cytoplasm, which were subsequently confirmed in other family members (pierce2023arisingtide pages 7-8). These structural features are expected to be conserved in acn1.
The co-occurrence of the wax synthase domain with the MBOAT_2 domain is characteristic of proteins involved in neutral lipid ester biosynthesis. Prokaryotic WS/DGAT enzymes are structurally unrelated to the eukaryotic MBOAT-type wax synthases (waltermann2007keyenzymesfor pages 1-2), indicating that acn1 represents the eukaryotic MBOAT-type lineage of acyltransferases rather than the bacterial WS/DGAT family.
The gene symbol acn1 / SPBC3H7.05c encodes an uncharacterized membrane protein for which no direct functional studies have been published. The protein has not been the subject of targeted biochemical characterization, localization studies, or mutant phenotype analysis in the primary literature. All functional predictions described herein are based on domain-based inference from the Wax_synthase_dom (IPR032805) and MBOAT_2 (PF13813) domains, and from the well-characterized properties of the broader MBOAT superfamily (pierce2023arisingtide pages 2-4, chang2011membraneboundoacyltransferases(mboats) pages 1-3, pierce2023arisingtide pages 1-2).
Based on the available evidence, the most parsimonious interpretation is that acn1 encodes an acyl-CoA-dependent membrane-bound acyltransferase, likely involved in neutral lipid biosynthesis (TAG and/or wax ester synthesis) or lipid remodeling. The protein is predicted to function as an integral membrane enzyme of the endoplasmic reticulum, catalyzing the transfer of acyl groups from acyl-CoA to lipid or fatty alcohol acceptor substrates. In S. pombe, where TAG synthesis is known to depend on Plh1p and Dga1p (zhang2003schizosaccharomycespombecells pages 2-4), acn1 may represent an additional or accessory acyltransferase with a potentially distinct substrate specificity. Biochemical characterization—including heterologous expression, enzymatic assays with defined substrates, and localization studies—will be necessary to definitively establish the function of this protein.
References
(holic2020metabolismofphospholipids pages 1-4): Roman Holič, Lucia Pokorná, and Peter Griač. Metabolism of phospholipids in the yeast schizosaccharomyces pombe. Dec 2020. URL: https://doi.org/10.1002/yea.3451, doi:10.1002/yea.3451. This article has 9 citations and is from a peer-reviewed journal.
(pierce2023arisingtide pages 2-4): Mariah R. Pierce and James L. Hougland. A rising tide lifts all mboats: recent progress in structural and functional understanding of membrane bound o-acyltransferases. Frontiers in Physiology, May 2023. URL: https://doi.org/10.3389/fphys.2023.1167873, doi:10.3389/fphys.2023.1167873. This article has 23 citations.
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(cheng2022heterologousexpressionand pages 1-2): Daolin Cheng, Ling Li, Ludmila Rizhsky, Priyanka Bhandary, and Basil J. Nikolau. Heterologous expression and characterization of plant wax ester producing enzymes. Metabolites, 12:577, Jun 2022. URL: https://doi.org/10.3390/metabo12070577, doi:10.3390/metabo12070577. This article has 11 citations.
(pierce2023arisingtide pages 1-2): Mariah R. Pierce and James L. Hougland. A rising tide lifts all mboats: recent progress in structural and functional understanding of membrane bound o-acyltransferases. Frontiers in Physiology, May 2023. URL: https://doi.org/10.3389/fphys.2023.1167873, doi:10.3389/fphys.2023.1167873. This article has 23 citations.
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(cheng2022heterologousexpressionand pages 13-15): Daolin Cheng, Ling Li, Ludmila Rizhsky, Priyanka Bhandary, and Basil J. Nikolau. Heterologous expression and characterization of plant wax ester producing enzymes. Metabolites, 12:577, Jun 2022. URL: https://doi.org/10.3390/metabo12070577, doi:10.3390/metabo12070577. This article has 11 citations.
(chang2011membraneboundoacyltransferases(mboats) pages 3-4): Catherine C. Y. Chang, Jie Sun, and Ta-Yuan Chang. Membrane-bound o-acyltransferases (mboats). Frontiers in Biology, 6:177-182, Jun 2011. URL: https://doi.org/10.1007/s11515-011-1149-z, doi:10.1007/s11515-011-1149-z. This article has 82 citations.
(cheng2022heterologousexpressionand pages 9-11): Daolin Cheng, Ling Li, Ludmila Rizhsky, Priyanka Bhandary, and Basil J. Nikolau. Heterologous expression and characterization of plant wax ester producing enzymes. Metabolites, 12:577, Jun 2022. URL: https://doi.org/10.3390/metabo12070577, doi:10.3390/metabo12070577. This article has 11 citations.
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(holic2020metabolismofphospholipids pages 4-6): Roman Holič, Lucia Pokorná, and Peter Griač. Metabolism of phospholipids in the yeast schizosaccharomyces pombe. Dec 2020. URL: https://doi.org/10.1002/yea.3451, doi:10.1002/yea.3451. This article has 9 citations and is from a peer-reviewed journal.
(cheng2022heterologousexpressionand pages 2-3): Daolin Cheng, Ling Li, Ludmila Rizhsky, Priyanka Bhandary, and Basil J. Nikolau. Heterologous expression and characterization of plant wax ester producing enzymes. Metabolites, 12:577, Jun 2022. URL: https://doi.org/10.3390/metabo12070577, doi:10.3390/metabo12070577. This article has 11 citations.
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(meyers2017theproteinand pages 13-17): Alex Meyers, Karuna Chourey, Taylor M. Weiskittel, Susan Pfiffner, John R. Dunlap, Robert L. Hettich, and Paul Dalhaimer. The protein and neutral lipid composition of lipid droplets isolated from the fission yeast, schizosaccharomyces pombe. Journal of Microbiology, 55:112-122, Jan 2017. URL: https://doi.org/10.1007/s12275-017-6205-1, doi:10.1007/s12275-017-6205-1. This article has 22 citations and is from a peer-reviewed journal.
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(pierce2023arisingtide pages 7-8): Mariah R. Pierce and James L. Hougland. A rising tide lifts all mboats: recent progress in structural and functional understanding of membrane bound o-acyltransferases. Frontiers in Physiology, May 2023. URL: https://doi.org/10.3389/fphys.2023.1167873, doi:10.3389/fphys.2023.1167873. This article has 23 citations.
(waltermann2007keyenzymesfor pages 1-2): Marc Wältermann, Tim Stöveken, and Alexander Steinbüchel. Key enzymes for biosynthesis of neutral lipid storage compounds in prokaryotes: properties, function and occurrence of wax ester synthases/acyl-coa:diacylglycerol acyltransferases. Biochimie, 89(2):230-242, Feb 2007. URL: https://doi.org/10.1016/j.biochi.2006.07.013, doi:10.1016/j.biochi.2006.07.013. This article has 156 citations and is from a peer-reviewed journal.