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Current Opinion in Structural Biology Jun 2023The membrane-bound O-acyltransferase (MBOAT) superfamily catalyses the transfer of acyl chains to substrates implicated in essential cellular functions. Aberrant... (Review)
Review
The membrane-bound O-acyltransferase (MBOAT) superfamily catalyses the transfer of acyl chains to substrates implicated in essential cellular functions. Aberrant function of MBOATs is associated with various diseases and MBOATs are promising drug targets. There has been recent progress in structural characterisation of MBOATs, advancing our understanding of their functional mechanism. Integrating information across the MBOAT family, we characterise a common MBOAT fold and provide a blueprint for substrate and inhibitor engagement. This work provides context for the diverse substrates, mechanisms, and evolutionary relationships of protein and small-molecule MBOATs. Further work should aim to characterise MBOATs, as inherently lipid-associated proteins, within their membrane environment.
Topics: Acyltransferases
PubMed: 37040671
DOI: 10.1016/j.sbi.2023.102589 -
JCI Insight May 2023In eutherians, the placenta plays a critical role in the uptake, storage, and metabolism of lipids. These processes govern the availability of fatty acids to the...
In eutherians, the placenta plays a critical role in the uptake, storage, and metabolism of lipids. These processes govern the availability of fatty acids to the developing fetus, where inadequate supply has been associated with substandard fetal growth. Whereas lipid droplets are essential for the storage of neutral lipids in the placenta and many other tissues, the processes that regulate placental lipid droplet lipolysis remain largely unknown. To assess the role of triglyceride lipases and their cofactors in determining placental lipid droplet and lipid accumulation, we assessed the role of patatin like phospholipase domain containing 2 (PNPLA2) and comparative gene identification-58 (CGI58) in lipid droplet dynamics in the human and mouse placenta. While both proteins are expressed in the placenta, the absence of CGI58, not PNPLA2, markedly increased placental lipid and lipid droplet accumulation. These changes were reversed upon restoration of CGI58 levels selectively in the CGI58-deficient mouse placenta. Using co-immunoprecipitation, we found that, in addition to PNPLA2, PNPLA9 interacts with CGI58. PNPLA9 was dispensable for lipolysis in the mouse placenta yet contributed to lipolysis in human placental trophoblasts. Our findings establish a crucial role for CGI58 in placental lipid droplet dynamics and, by extension, in nutrient supply to the developing fetus.
Topics: Lipase; Lipolysis; Humans; Animals; Mice; Placenta; 1-Acylglycerol-3-Phosphate O-Acyltransferase; Acyltransferases; Trophoblasts; Female; Lipid Droplets
PubMed: 37212279
DOI: 10.1172/jci.insight.168717 -
Journal of the Royal Society, Interface Aug 2013Polyketide natural products act as a broad range of therapeutics, including antibiotics, immunosuppressants and anti-cancer agents. This therapeutic diversity stems from... (Review)
Review
Polyketide natural products act as a broad range of therapeutics, including antibiotics, immunosuppressants and anti-cancer agents. This therapeutic diversity stems from the structural diversity of these small molecules, many of which are produced in an assembly line manner by modular polyketide synthases. The acyltransferase (AT) domains of these megasynthases are responsible for selection and incorporation of simple monomeric building blocks, and are thus responsible for a large amount of the resulting polyketide structural diversity. The substrate specificity of these domains is often targeted for engineering in the generation of novel, therapeutically active natural products. This review outlines recent developments that can be used in the successful engineering of these domains, including AT sequence and structural data, mechanistic insights and the production of a diverse pool of extender units. It also provides an overview of previous AT domain engineering attempts, and concludes with proposed engineering approaches that take advantage of current knowledge. These approaches may lead to successful production of biologically active 'unnatural' natural products.
Topics: Acyltransferases; Polyketide Synthases; Protein Engineering; Substrate Specificity
PubMed: 23720536
DOI: 10.1098/rsif.2013.0297 -
Scientific Reports Jan 2020Lipoproteins are important components of the cell envelope and are responsible for many essential cellular functions. They are produced by the post-translational...
Lipoproteins are important components of the cell envelope and are responsible for many essential cellular functions. They are produced by the post-translational covalent attachment of lipids that occurs via a sequential 3-step process controlled by three integral membrane enzymes. The last step of this process, unique to Gram-negative bacteria, is the N-acylation of the terminal cysteine by Apolipoprotein N-acyltransferase (Lnt) to form the final mature lipoprotein. Here we report 2 crystal forms of Lnt from Escherichia coli. In one form we observe a highly dynamic arm that is able to restrict access to the active site as well as a covalent modification to the active site cysteine consistent with the thioester acyl-intermediate. In the second form, the enzyme crystallized in an open conformation exposing the active site to the environment. In total we observe 3 unique Lnt molecules that when taken together suggest the movement of essential loops and residues are triggered by substrate binding that could control the interaction between Lnt and the incoming substrate apolipoprotein. The results provide a dynamic context for residues shown to be central for Lnt function and provide further insights into its mechanism.
Topics: Acylation; Acyltransferases; Apolipoproteins; Catalytic Domain; Crystallization; Cysteine; Escherichia coli; Protein Conformation
PubMed: 31959792
DOI: 10.1038/s41598-020-57419-7 -
Journal of Lipid Research Apr 2009Cells of all organisms are enclosed by a plasma membrane containing bipolar lipids, cholesterol, and proteins. Cellular membranes contain several classes of... (Review)
Review
Cells of all organisms are enclosed by a plasma membrane containing bipolar lipids, cholesterol, and proteins. Cellular membranes contain several classes of glycerophospholipids, which have numerous structural and functional roles in cells. Polyunsaturated fatty acids including arachidonic acid and eicosapentaenoic acid are usually located at the sn-2 position, but not the sn-1 position, of glycerophospholipids in an asymmetrical manner. Glycerophospholipids are first formed by the de novo pathway (Kennedy pathway) using acyl-CoAs as donors. Subsequently, in the remodeling pathway (Lands' cycle), cycles of deacylation and reacylation of glycerophospholipids modify the fatty acid composition to generate mature membrane with asymmetry and diversity. Both pathways were proposed in the 1950s. Whereas the enzymes involved in the Kennedy pathway have been well characterized, little is known about the enzymes involved in the Lands' cycle. Recently, several laboratories, including ours, have identified enzymes working in the Lands' cycle from the 1-acylglycerol-3-phosphate O-acyltransferase (AGPAT) family, and also from the membrane bound O-acyltransferases (MBOAT) family. These discoveries have prompted a robust surge of research in this field. In this review, we focus on the cloning and characterization of lysophospholipid acyltransferases (LPLATs), which contribute to membrane asymmetry and diversity.
Topics: 1-Acylglycerol-3-Phosphate O-Acyltransferase; 1-Acylglycerophosphocholine O-Acyltransferase; Acyl Coenzyme A; Acyltransferases; Animals; Humans; Phosphatidic Acids; Phosphatidylcholines
PubMed: 18931347
DOI: 10.1194/jlr.R800035-JLR200 -
Nutrients Oct 2016The ability to store and distribute vitamin A inside the body is the main evolutionary adaptation that allows vertebrates to maintain retinoid functions during... (Review)
Review
The ability to store and distribute vitamin A inside the body is the main evolutionary adaptation that allows vertebrates to maintain retinoid functions during nutritional deficiencies and to acquire new metabolic pathways enabling light-independent production of 11- retinoids. These processes greatly depend on enzymes that esterify vitamin A as well as associated retinoid binding proteins. Although the significance of retinyl esters for vitamin A homeostasis is well established, until recently, the molecular basis for the retinol esterification enzymatic activity was unknown. In this review, we will look at retinoid absorption through the prism of current biochemical and structural studies on vitamin A esterifying enzymes. We describe molecular adaptations that enable retinoid storage and delineate mechanisms in which mutations found in selective proteins might influence vitamin A homeostasis in affected patients.
Topics: Acyltransferases; Animals; Biocatalysis; Biological Transport; Biological Transport, Active; Carboxylic Ester Hydrolases; Esterification; Evolution, Molecular; Humans; Intestinal Absorption; Intestinal Mucosa; Liver; Models, Biological; Mutation; Protein Conformation; Vertebrates; Visual Pathways; Vitamin A
PubMed: 27792183
DOI: 10.3390/nu8110676 -
Journal of Lipid Research Apr 2017
Topics: Acyltransferases; Color Vision; Diacylglycerol O-Acyltransferase; Substrate Specificity
PubMed: 28232616
DOI: 10.1194/jlr.C075838 -
The Journal of Biological Chemistry Oct 2014Acyl CoA:1,2-diacylglycerol acyltransferase (DGAT)-2 is an integral membrane protein that catalyzes triacylglycerol (TG) synthesis using diacylglycerol and fatty acyl...
Acyl CoA:1,2-diacylglycerol acyltransferase (DGAT)-2 is an integral membrane protein that catalyzes triacylglycerol (TG) synthesis using diacylglycerol and fatty acyl CoA as substrates. DGAT2 resides in the endoplasmic reticulum (ER), but when cells are incubated with fatty acids, DGAT2 interacts with lipid droplets presumably to catalyze localized TG synthesis for lipid droplet expansion. Previous studies have shown that DGAT2 interacts with proteins that synthesize its fatty acyl CoA substrates. In this study, we provide additional evidence that DGAT2 is present in a protein complex. Using a chemical cross-linker, disuccinimidyl suberate (DSS), we demonstrated that DGAT2 formed a dimer and was also part of a protein complex of ∼ 650 kDa, both in membranes and on lipid droplets. Using co-immunoprecipitation experiments and an in situ proximity ligation assay, we found that DGAT2 interacted with monoacylglycerol acyltransferase (MGAT)-2, an enzyme that catalyzes the synthesis of diacylglycerol. Deletion mutagenesis showed that the interaction with MGAT2 was dependent on the two transmembrane domains of DGAT2. No significant interaction of DGAT2 with lipin1, another enzyme that synthesizes diacylglycerol, could be detected. When co-expressed in cells, DGAT2 and MGAT2 co-localized in the ER and on lipid droplets. Co-expression also resulted in increased TG storage compared with expression of DGAT2 or MGAT2 alone. Incubating McArdle rat hepatoma RH7777 cells with 2-monoacylglycerol caused DGAT2 to translocate to lipid droplets. This also led to the formation of large cytosolic lipid droplets, characteristic of DGAT2, but not DGAT1, and indicated that DGAT2 can utilize monoacylglycerol-derived diacylglycerol. These findings suggest that the interaction of DGAT2 and MGAT2 serves to channel lipid substrates efficiently for TG biosynthesis.
Topics: Acyltransferases; Animals; COS Cells; Cell Line, Tumor; Chlorocebus aethiops; Cross-Linking Reagents; Diacylglycerol O-Acyltransferase; Endoplasmic Reticulum; Gene Expression Regulation; HEK293 Cells; Hepatocytes; Humans; Lipid Droplets; Monoglycerides; Protein Binding; Protein Multimerization; Rats; Signal Transduction; Succinimides; Triglycerides
PubMed: 25164810
DOI: 10.1074/jbc.M114.571190 -
International Journal of Molecular... Jan 2023Triacylglycerol (TG) biosynthesis is an important metabolic process for intracellular storage of surplus energy, intestinal dietary fat absorption, attenuation of...
Triacylglycerol (TG) biosynthesis is an important metabolic process for intracellular storage of surplus energy, intestinal dietary fat absorption, attenuation of lipotoxicity, lipid transportation, lactation and signal transduction in mammals. Transmembrane protein 68 (TMEM68) is an endoplasmic reticulum (ER)-anchored acyltransferase family member of unknown function. In the current study we show that overexpression of TMEM68 promotes TG accumulation and lipid droplet (LD) formation in a conserved active sites-dependent manner. Quantitative targeted lipidomic analysis showed that diacylglycerol (DG), free fatty acid (FFA) and TG levels were increased by TMEM68 expression. In addition, TMEM68 overexpression affected the levels of several glycerophospholipids, such as phosphatidylcholine, phosphatidylethanolamine and phosphatidylinositol, as well as sterol ester contents. TMEM68 exhibited monoacylglycerol acyltransferase (MGAT) and diacylglycerol acyltransferase (DGAT) activities dependent on the conserved active sites in an in vitro assay. The expression of lipogenesis genes, including DGATs, fatty acid synthesis-related genes and peroxisome proliferator-activated receptor γ was upregulated in TMEM68-overexpressing cells. These results together demonstrate for the first time that TMEM68 functions as an acyltransferase and affects lipogenic gene expression, glycerolipid metabolism and TG storage in mammalian cells.
Topics: Animals; Female; Humans; Acyltransferases; Diacylglycerol O-Acyltransferase; Lipogenesis; Mammals; Triglycerides; Membrane Proteins
PubMed: 36768334
DOI: 10.3390/ijms24032012 -
Plant Physiology May 2023Glycerolipids are the most abundant lipids in microalgae, and glycerol-3-phosphate:acyl-CoA acyltransferase (GPAT) plays an important role in their biosynthesis....
Glycerolipids are the most abundant lipids in microalgae, and glycerol-3-phosphate:acyl-CoA acyltransferase (GPAT) plays an important role in their biosynthesis. However, the biochemical and biological functions of algal GPAT remain poorly characterized. Here, we characterized the endoplasmic reticulum (ER)-associated GPAT of the model unicellular green alga Chlamydomonas reinhardtii (CrGPATer). Enzymatic assays indicated that CrGPATer is an sn-1 acyltransferase using a variety of acyl-CoAs as the acyl donor. Subcellular localization revealed that CrGPATer was associated with ER membranes and lipid droplets. We constructed overexpression (OE) and knockdown (KD) transgenic C. reinhardtii lines to investigate the in vivo function of CrGPATer. Lipidomic analysis indicated that CrGPATer OE enhanced the cellular content of galactolipids, especially monogalactosyldiacylglycerol, under nitrogen deficiency stress. Correspondingly, CrGPATer KD lines contained lower contents of galactolipids than the control. Feeding experiments with labeled phosphatidic acid revealed that the intermediate of the eukaryotic Kennedy pathway could be used for galactolipid biosynthesis in the chloroplasts. These results provided multiple lines of evidence that the eukaryotic Kennedy pathway mediated by CrGPATer may be involved in galactolipid biosynthesis in C. reinhardtii. OE of CrGPATer significantly increased the content of triacylglycerol and the yield of biomass. Moreover, the content and yield of 1, 3-olein-2-palmitin, a high-value lipid that can be used as an alternative for human milk fat in infant formula, were significantly enhanced in the OE transgenic lines. Taken together, this study provided insights into the biochemical and biological functions of CrGPATer and its potential as a genetic engineering target in functional lipid manufacturing.
Topics: Humans; Acyltransferases; Galactolipids; Glycerol; Glycerol-3-Phosphate O-Acyltransferase; Microalgae; Phosphates; Plants; Triglycerides; Lipid Metabolism
PubMed: 36805986
DOI: 10.1093/plphys/kiad091