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Flyckt KS, Roesler K, Haug Collet K, Jaureguy L, Booth R, Thatcher SR, Everard JD, Ripp KG, Liu ZB, Shen B, Wayne LL. A Novel Soybean Diacylglycerol Acyltransferase 1b Variant with Three Amino Acid Substitutions Increases Seed Oil Content. PLANT & CELL PHYSIOLOGY 2024; 65:872-884. [PMID: 37982755 PMCID: PMC11209548 DOI: 10.1093/pcp/pcad148] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2023] [Revised: 10/24/2023] [Accepted: 11/17/2023] [Indexed: 11/21/2023]
Abstract
Improving soybean (Glycine max) seed composition by increasing the protein and oil components will add significant value to the crop and enhance environmental sustainability. Diacylglycerol acyltransferase (DGAT) catalyzes the final rate-limiting step in triacylglycerol biosynthesis and has a major impact on seed oil accumulation. We previously identified a soybean DGAT1b variant modified with 14 amino acid substitutions (GmDGAT1b-MOD) that increases total oil content by 3 percentage points when overexpressed in soybean seeds. In the present study, additional GmDGAT1b variants were generated to further increase oil with a reduced number of substitutions. Variants with one to four amino acid substitutions were screened in the model systems Saccharomyces cerevisiae and transient Nicotiana benthamiana leaf. Promising GmDGAT1b variants resulting in high oil accumulation in the model systems were selected for overexpression in soybeans. One GmDGAT1b variant with three novel amino acid substitutions (GmDGAT1b-3aa) increased total soybean oil to levels near the previously discovered GmDGAT1b-MOD variant. In a multiple location field trial, GmDGAT1b-3aa transgenic events had significantly increased oil and protein by up to 2.3 and 0.6 percentage points, respectively. The modeling of the GmDGAT1b-3aa protein structure provided insights into the potential function of the three substitutions. These findings will guide efforts to improve soybean oil content and overall seed composition by CRISPR editing.
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Affiliation(s)
- Kayla S Flyckt
- Corteva Agriscience, 7300 NW 62nd Avenue, Johnston 50131, USA
| | - Keith Roesler
- Corteva Agriscience, 7300 NW 62nd Avenue, Johnston 50131, USA
| | | | | | - Russ Booth
- Corteva Agriscience, 7300 NW 62nd Avenue, Johnston 50131, USA
| | | | - John D Everard
- Corteva Agriscience, 7300 NW 62nd Avenue, Johnston 50131, USA
| | - Kevin G Ripp
- Corteva Agriscience, 7300 NW 62nd Avenue, Johnston 50131, USA
| | - Zhan-Bin Liu
- Corteva Agriscience, 7300 NW 62nd Avenue, Johnston 50131, USA
| | - Bo Shen
- Corteva Agriscience, 7300 NW 62nd Avenue, Johnston 50131, USA
| | - Laura L Wayne
- Corteva Agriscience, 7300 NW 62nd Avenue, Johnston 50131, USA
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2
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Lee KR, Yeo Y, Lee J, Kim S, Im C, Kim I, Lee J, Lee SK, Suh MC, Kim HU. Functional Characterization of the Effects of CsDGAT1 and CsDGAT2 on Fatty Acid Composition in Camelina sativa. Int J Mol Sci 2024; 25:6944. [PMID: 39000052 PMCID: PMC11240937 DOI: 10.3390/ijms25136944] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2024] [Revised: 06/21/2024] [Accepted: 06/21/2024] [Indexed: 07/14/2024] Open
Abstract
Triacylglycerols (TAGs) are the storage oils of plant seeds, and these lipids provide energy for seed germination and valuable oils for human consumption. Three diacylglycerol acyltransferases (DGAT1, DGAT2, and DGAT3) and phospholipid:diacylglycerol acyltransferases participate in the biosynthesis of TAGs. DGAT1 and DGAT2 participate in the biosynthesis of TAGs through the endoplasmic reticulum (ER) pathway. In this study, we functionally characterized CsDGAT1 and CsDGAT2 from camelina (Camelina sativa). Green fluorescent protein-fused CsDGAT1 and CsDGAT2 localized to the ER when transiently expressed in Nicotiana benthamiana leaves. To generate Csdgat1 and Csdgat2 mutants using the CRISPR/Cas9 system, camelina was transformed with a binary vector carrying Cas9 and the respective guide RNAs targeting CsDGAT1s and CsDGAT2s via the Agrobacterium-mediated floral dip method. The EDD1 lines had missense and nonsense mutations in the CsDGAT1 homoeologs, suggesting that they retained some CsDGAT1 function, and their seeds showed decreased eicosaenoic acid (C20:1) contents and increased C18:3 contents compared to the wild type (WT). The EDD2 lines had a complete knockout of all CsDGAT2 homoeologs and a slightly decreased C18:3 content compared to the WT. In conclusion, CsDGAT1 and CsDGAT2 have a small influence on the seed oil content and have an acyl preference for C20:1 and C18:3, respectively. This finding can be applied to develop oilseed plants containing high omega-3 fatty acids or high oleic acid.
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Affiliation(s)
- Kyeong-Ryeol Lee
- Department of Agricultural Biotechnology, National Institute of Agricultural Sciences, Rural Development Administration, Jeonju 54875, Republic of Korea
| | - Yumi Yeo
- Department of Agricultural Biotechnology, National Institute of Agricultural Sciences, Rural Development Administration, Jeonju 54875, Republic of Korea
| | - Jihyea Lee
- Department of Agricultural Biotechnology, National Institute of Agricultural Sciences, Rural Development Administration, Jeonju 54875, Republic of Korea
| | - Semi Kim
- Department of Life Science, Sogang University, Seoul 04107, Republic of Korea
| | - Chorong Im
- Department of Agricultural Biotechnology, National Institute of Agricultural Sciences, Rural Development Administration, Jeonju 54875, Republic of Korea
| | - Inyoung Kim
- Department of Bioindustry and Bioresource Engineering, Plant Engineering Research Institute, Sejong University, Seoul 05006, Republic of Korea
| | - Juho Lee
- Department of Agricultural Biotechnology, National Institute of Agricultural Sciences, Rural Development Administration, Jeonju 54875, Republic of Korea
| | - Seon-Kyeong Lee
- Department of Agricultural Biotechnology, National Institute of Agricultural Sciences, Rural Development Administration, Jeonju 54875, Republic of Korea
| | - Mi Chung Suh
- Department of Life Science, Sogang University, Seoul 04107, Republic of Korea
| | - Hyun Uk Kim
- Department of Bioindustry and Bioresource Engineering, Plant Engineering Research Institute, Sejong University, Seoul 05006, Republic of Korea
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3
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Schiaffarino O, Valdivieso González D, García-Pérez IM, Peñalva DA, Almendro-Vedia VG, Natale P, López-Montero I. Mitochondrial membrane models built from native lipid extracts: Interfacial and transport properties. Front Mol Biosci 2022; 9:910936. [PMID: 36213125 PMCID: PMC9538489 DOI: 10.3389/fmolb.2022.910936] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2022] [Accepted: 09/02/2022] [Indexed: 12/03/2022] Open
Abstract
The mitochondrion is an essential organelle enclosed by two membranes whose functionalities depend on their very specific protein and lipid compositions. Proteins from the outer mitochondrial membrane (OMM) are specialized in mitochondrial dynamics and mitophagy, whereas proteins of the inner mitochondrial membrane (IMM) have dedicated functions in cellular respiration and apoptosis. As for lipids, the OMM is enriched in glycerophosphatidyl choline but cardiolipin is exclusively found within the IMM. Though the lipid topology and distribution of the OMM and IMM are known since more than four decades, little is known about the interfacial and dynamic properties of the IMM and OMM lipid extracts. Here we build monolayers, supported bilayers and giant unilamellar vesicles (GUVs) of native OMM and IMM lipids extracts from porcine heart. Additionally, we perform a comparative analysis on the interfacial, phase immiscibility and mechanical properties of both types of extract. Our results show that IMM lipids form more expanded and softer membranes than OMM lipids, allowing a better understanding of the physicochemical and biophysical properties of mitochondrial membranes.
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Affiliation(s)
- Olivia Schiaffarino
- Departamento Química Física, Universidad Complutense de Madrid, Madrid, Spain
| | - David Valdivieso González
- Departamento Química Física, Universidad Complutense de Madrid, Madrid, Spain
- Instituto de Investigación Biomédica Hospital Doce de Octubre (imas12), Madrid, Spain
| | | | - Daniel A. Peñalva
- Instituto de Investigaciones Bioquímicas de Bahía Blanca (INIBIBB), ConsejoNacional de Investigaciones Científicas y Técnicas (CONICET), Universidad Nacional del Sur (UNS), Bahía Blanca, Argentina
- Departamento de Biología, Bioquímica y Farmacia, Universidad Nacional del Sur (UNS), Bahía Blanca, Argentina
| | - Víctor G. Almendro-Vedia
- Instituto de Investigación Biomédica Hospital Doce de Octubre (imas12), Madrid, Spain
- Departamento de Farmacia Galénica y Tecnología Alimentaria, Universidad Complutense de Madrid, Madrid, Spain
| | - Paolo Natale
- Departamento Química Física, Universidad Complutense de Madrid, Madrid, Spain
- Instituto de Investigación Biomédica Hospital Doce de Octubre (imas12), Madrid, Spain
- *Correspondence: Iván López-Montero, ; Paolo Natale,
| | - Iván López-Montero
- Departamento Química Física, Universidad Complutense de Madrid, Madrid, Spain
- Instituto de Investigación Biomédica Hospital Doce de Octubre (imas12), Madrid, Spain
- Instituto Pluridisciplinar, Universidad Complutense de Madrid, Madrid, Spain
- *Correspondence: Iván López-Montero, ; Paolo Natale,
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4
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Chen G, Harwood JL, Lemieux MJ, Stone SJ, Weselake RJ. Acyl-CoA:diacylglycerol acyltransferase: Properties, physiological roles, metabolic engineering and intentional control. Prog Lipid Res 2022; 88:101181. [PMID: 35820474 DOI: 10.1016/j.plipres.2022.101181] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2022] [Revised: 05/31/2022] [Accepted: 07/04/2022] [Indexed: 12/15/2022]
Abstract
Acyl-CoA:diacylglycerol acyltransferase (DGAT, EC 2.3.1.20) catalyzes the last reaction in the acyl-CoA-dependent biosynthesis of triacylglycerol (TAG). DGAT activity resides mainly in membrane-bound DGAT1 and DGAT2 in eukaryotes and bifunctional wax ester synthase-diacylglycerol acyltransferase (WSD) in bacteria, which are all membrane-bound proteins but exhibit no sequence homology to each other. Recent studies also identified other DGAT enzymes such as the soluble DGAT3 and diacylglycerol acetyltransferase (EaDAcT), as well as enzymes with DGAT activities including defective in cuticular ridges (DCR) and steryl and phytyl ester synthases (PESs). This review comprehensively discusses research advances on DGATs in prokaryotes and eukaryotes with a focus on their biochemical properties, physiological roles, and biotechnological and therapeutic applications. The review begins with a discussion of DGAT assay methods, followed by a systematic discussion of TAG biosynthesis and the properties and physiological role of DGATs. Thereafter, the review discusses the three-dimensional structure and insights into mechanism of action of human DGAT1, and the modeled DGAT1 from Brassica napus. The review then examines metabolic engineering strategies involving manipulation of DGAT, followed by a discussion of its therapeutic applications. DGAT in relation to improvement of livestock traits is also discussed along with DGATs in various other eukaryotic organisms.
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Affiliation(s)
- Guanqun Chen
- Department of Agricultural, Food, and Nutritional Science, University of Alberta, Edmonton, Alberta T6H 2P5, Canada.
| | - John L Harwood
- School of Biosciences, Cardiff University, Cardiff CF10 3AX, UK
| | - M Joanne Lemieux
- Department of Biochemistry, University of Alberta, Membrane Protein Disease Research Group, Edmonton T6G 2H7, Canada
| | - Scot J Stone
- Department of Biochemistry, Microbiology and Immunology, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E5, Canada.
| | - Randall J Weselake
- Department of Agricultural, Food, and Nutritional Science, University of Alberta, Edmonton, Alberta T6H 2P5, Canada
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5
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Carro MDLM, Gonorazky G, Soto D, Mamone L, Bagnato C, Pagnussat LA, Beligni MV. Expression of Chlamydomonas reinhardtii chloroplast diacylglycerol acyltransferase 3 is induced by light in concert with triacylglycerol accumulation. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2022; 110:262-276. [PMID: 35043497 DOI: 10.1111/tpj.15671] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/19/2021] [Revised: 12/15/2021] [Accepted: 01/09/2022] [Indexed: 06/14/2023]
Abstract
Considerable progress has been made towards the understanding of triacylglycerol (TAG) accumulation in algae. One key aspect is finding conditions that trigger TAG production without reducing cell division. Previously, we identified a soluble diacylglycerol acyltransferase (DGAT), related to plant DGAT3, with heterologous DGAT activity. In this work, we demonstrate that Chlamydomonas reinhardtii DGAT3 localizes to the chloroplast and that its expression is induced by light, in correspondence with TAG accumulation. Dgat3 mRNAs and TAGs increase in both wild-type and starch-deficient cells grown with acetate upon transferring them from dark or low light to higher light levels, albeit affected by the particularities of each strain. The response of dgat3 mRNAs and TAGs to light depends on the pre-existing levels of TAGs, suggesting the existence of a negative regulatory loop in the synthesis pathway, although an effect of TAG turnover cannot be ruled out. Altogether, these results hint towards a possible role of DGAT3 in light-dependent TAG accumulation in C. reinhardtii.
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Affiliation(s)
- María de Las Mercedes Carro
- Instituto de Investigaciones Biológicas (IIB-CONICET-UNMdP), Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Mar del Plata, B7608FBY, Mar del Plata, Argentina
| | - Gabriela Gonorazky
- Instituto de Investigaciones Biológicas (IIB-CONICET-UNMdP), Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Mar del Plata, B7608FBY, Mar del Plata, Argentina
| | - Débora Soto
- Instituto de Investigaciones Biológicas (IIB-CONICET-UNMdP), Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Mar del Plata, B7608FBY, Mar del Plata, Argentina
| | - Leandro Mamone
- Instituto de Investigaciones Biológicas (IIB-CONICET-UNMdP), Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Mar del Plata, B7608FBY, Mar del Plata, Argentina
| | - Carolina Bagnato
- Instituto de Energía y Desarrollo Sustentable (IEDS), Comisión Nacional de Energía Atómica, Centro Atómico Bariloche, 8400, San Carlos de Bariloche, Argentina
| | - Luciana A Pagnussat
- Facultad de Ciencias Agrarias, Universidad Nacional de Mar del Plata, B7620EMA, Balcarce, Argentina
| | - María Verónica Beligni
- Instituto de Investigaciones Biológicas (IIB-CONICET-UNMdP), Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Mar del Plata, B7608FBY, Mar del Plata, Argentina
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6
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Caldo KMP, Shen W, Xu Y, Hanley-Bowdoin L, Chen G, Weselake RJ, Lemieux MJ. Diacylglycerol acyltransferase 1 is activated by phosphatidate and inhibited by SnRK1-catalyzed phosphorylation. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2018; 96:287-299. [PMID: 30003607 DOI: 10.1111/tpj.14029] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/07/2018] [Revised: 05/23/2018] [Accepted: 06/26/2018] [Indexed: 05/06/2023]
Abstract
Diacylglycerol acyltransferase 1 (DGAT1) catalyzes the final and committed step in the Kennedy pathway for triacylglycerol (TAG) biosynthesis and, as such, elucidating its mode of regulation is critical to understand the fundamental aspects of carbon metabolism in oleaginous crops. In this study, purified Brassica napus diacylglycerol acyltransferase 1 (BnaDGAT1) in n-dodecyl-β-d-maltopyranoside micelles was lipidated to form mixed micelles and subjected to detailed biochemical analysis. The degree of mixed micelle fluidity appeared to influence acyltransferase activity. BnaDGAT1 exhibited a sigmoidal response and eventual substrate inhibition with respect to increasing concentrations of oleoyl-CoA. Phosphatidate (PA) was identified as a feed-forward activator of BnaDGAT1, enabling the final enzyme in the Kennedy pathway to adjust to the incoming flow of carbon leading to TAG. In the presence of PA, the oleoyl-CoA saturation plot became more hyperbolic and desensitized to substrate inhibition indicating that PA facilitates the transition of the enzyme into the more active state. PA may also relieve possible autoinhibition of BnaDGAT1 brought about by the N-terminal regulatory domain, which was shown to interact with PA. Indeed, PA is a key effector modulating lipid homeostasis, in addition to its well recognized role in lipid signaling. BnaDGAT1 was also shown to be a substrate of the sucrose non-fermenting-1-related kinase 1 (SnRK1), which catalyzed phosphorylation of the enzyme and converted it to a less active form. Thus, this known regulator of carbon metabolism directly influences TAG biosynthesis.
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Affiliation(s)
- Kristian Mark P Caldo
- Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, Alberta, T6G 2P5, Canada
- Department of Biochemistry, University of Alberta, Edmonton, Alberta, T6G 2H7, Canada
| | - Wei Shen
- Department of Plant and Microbial Biology, North Carolina State University, Raleigh, NC, 27695, USA
| | - Yang Xu
- Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, Alberta, T6G 2P5, Canada
| | - Linda Hanley-Bowdoin
- Department of Plant and Microbial Biology, North Carolina State University, Raleigh, NC, 27695, USA
| | - Guanqun Chen
- Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, Alberta, T6G 2P5, Canada
| | - Randall J Weselake
- Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, Alberta, T6G 2P5, Canada
| | - M Joanne Lemieux
- Department of Biochemistry, University of Alberta, Edmonton, Alberta, T6G 2H7, Canada
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7
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Rosli R, Chan PL, Chan KL, Amiruddin N, Low ETL, Singh R, Harwood JL, Murphy DJ. In silico characterization and expression profiling of the diacylglycerol acyltransferase gene family (DGAT1, DGAT2, DGAT3 and WS/DGAT) from oil palm, Elaeis guineensis. PLANT SCIENCE : AN INTERNATIONAL JOURNAL OF EXPERIMENTAL PLANT BIOLOGY 2018; 275:84-96. [PMID: 30107884 DOI: 10.1016/j.plantsci.2018.07.011] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/12/2018] [Revised: 07/05/2018] [Accepted: 07/25/2018] [Indexed: 05/14/2023]
Abstract
The diacylglycerol acyltransferases (DGAT) (diacylglycerol:acyl-CoA acyltransferase, EC 2.3.1.20) are a key group of enzymes that catalyse the final and usually the most important rate-limiting step of triacylglycerol biosynthesis in plants and other organisms. Genes encoding four distinct functional families of DGAT enzymes have been characterised in the genome of the African oil palm, Elaeis guineensis. The contrasting features of the various isoforms within the four families of DGAT genes, namely DGAT1, DGAT2, DGAT3 and WS/DGAT are presented both in the oil palm itself and, for comparative purposes, in 12 other oil crop or model/related plants, namely Arabidopsis thaliana, Brachypodium distachyon, Brassica napus, Elaeis oleifera, Glycine max, Gossypium hirsutum, Helianthus annuus, Musa acuminata, Oryza sativa, Phoenix dactylifera, Sorghum bicolor, and Zea mays. The oil palm genome contains respectively three, two, two and two distinctly expressed functional copies of the DGAT1, DGAT2, DGAT3 and WS/DGAT genes. Phylogenetic analyses of the four DGAT families showed that the E. guineensis genes tend to cluster with sequences from P. dactylifera and M. acuminata rather than with other members of the Commelinid monocots group, such as the Poales which include the major cereal crops such as rice and maize. Comparison of the predicted DGAT protein sequences with other animal and plant DGATs was consistent with the E. guineensis DGAT1 being ER located with its active site facing the lumen while DGAT2, although also ER located, had a predicted cytosol-facing active site. In contrast, DGAT3 and some (but not all) WS/DGAT in E. guineensis are predicted to be soluble, cytosolic enzymes. Evaluation of E. guineensis DGAT gene expression in different tissues and developmental stages suggests that the four DGAT groups have distinctive physiological roles and are particularly prominent in developmental processes relating to reproduction, such as flowering, and in fruit/seed formation especially in the mesocarp and endosperm tissues.
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Affiliation(s)
- Rozana Rosli
- Genomics and Computational Biology Research Group, University of South Wales, Pontypridd, CF37 1DL, United Kingdom; Advanced Biotechnology and Breeding Centre, Malaysian Palm Oil Board, No 6, Persiaran Institusi, Bandar Baru Bangi, 43000 Kajang, Selangor, Malaysia
| | - Pek-Lan Chan
- Advanced Biotechnology and Breeding Centre, Malaysian Palm Oil Board, No 6, Persiaran Institusi, Bandar Baru Bangi, 43000 Kajang, Selangor, Malaysia
| | - Kuang-Lim Chan
- Advanced Biotechnology and Breeding Centre, Malaysian Palm Oil Board, No 6, Persiaran Institusi, Bandar Baru Bangi, 43000 Kajang, Selangor, Malaysia
| | - Nadzirah Amiruddin
- Advanced Biotechnology and Breeding Centre, Malaysian Palm Oil Board, No 6, Persiaran Institusi, Bandar Baru Bangi, 43000 Kajang, Selangor, Malaysia
| | - Eng-Ti Leslie Low
- Advanced Biotechnology and Breeding Centre, Malaysian Palm Oil Board, No 6, Persiaran Institusi, Bandar Baru Bangi, 43000 Kajang, Selangor, Malaysia
| | - Rajinder Singh
- Advanced Biotechnology and Breeding Centre, Malaysian Palm Oil Board, No 6, Persiaran Institusi, Bandar Baru Bangi, 43000 Kajang, Selangor, Malaysia
| | - John L Harwood
- School of Biosciences, University of Cardiff, Cardiff, CF10 3AX, United Kingdom
| | - Denis J Murphy
- Genomics and Computational Biology Research Group, University of South Wales, Pontypridd, CF37 1DL, United Kingdom.
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8
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Xu Y, Caldo KMP, Pal-Nath D, Ozga J, Lemieux MJ, Weselake RJ, Chen G. Properties and Biotechnological Applications of Acyl-CoA:diacylglycerol Acyltransferase and Phospholipid:diacylglycerol Acyltransferase from Terrestrial Plants and Microalgae. Lipids 2018; 53:663-688. [PMID: 30252128 DOI: 10.1002/lipd.12081] [Citation(s) in RCA: 60] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2018] [Revised: 07/23/2018] [Accepted: 07/24/2018] [Indexed: 12/14/2022]
Abstract
Triacylglycerol (TAG) is the major storage lipid in most terrestrial plants and microalgae, and has great nutritional and industrial value. Since the demand for vegetable oil is consistently increasing, numerous studies have been focused on improving the TAG content and modifying the fatty-acid compositions of plant seed oils. In addition, there is a strong research interest in establishing plant vegetative tissues and microalgae as platforms for lipid production. In higher plants and microalgae, TAG biosynthesis occurs via acyl-CoA-dependent or acyl-CoA-independent pathways. Diacylglycerol acyltransferase (DGAT) catalyzes the last and committed step in the acyl-CoA-dependent biosynthesis of TAG, which appears to represent a bottleneck in oil accumulation in some oilseed species. Membrane-bound and soluble forms of DGAT have been identified with very different amino-acid sequences and biochemical properties. Alternatively, TAG can be formed through acyl-CoA-independent pathways via the catalytic action of membrane-bound phospholipid:diacylglycerol acyltransferase (PDAT). As the enzymes catalyzing the terminal steps of TAG formation, DGAT and PDAT play crucial roles in determining the flux of carbon into seed TAG and thus have been considered as the key targets for engineering oil production. Here, we summarize the most recent knowledge on DGAT and PDAT in higher plants and microalgae, with the emphasis on their physiological roles, structural features, and regulation. The development of various metabolic engineering strategies to enhance the TAG content and alter the fatty-acid composition of TAG is also discussed.
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Affiliation(s)
- Yang Xu
- Department of Agricultural, Food and Nutritional Science, University of Alberta, 116 Street and 85 Avenue, Edmonton, Alberta, T6G 2P5, Canada
| | - Kristian Mark P Caldo
- Department of Agricultural, Food and Nutritional Science, University of Alberta, 116 Street and 85 Avenue, Edmonton, Alberta, T6G 2P5, Canada
- Department of Biochemistry, University of Alberta, 116 Street and 85 Avenue, Edmonton, Alberta, T6G 2H7, Canada
| | - Dipasmita Pal-Nath
- French Associates Institute for Agriculture and Biotechnology of Drylands, The Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Sede Boqer Campus, Midreshet Ben-Gurion, 8499000, Israel
| | - Jocelyn Ozga
- Department of Agricultural, Food and Nutritional Science, University of Alberta, 116 Street and 85 Avenue, Edmonton, Alberta, T6G 2P5, Canada
| | - M Joanne Lemieux
- Department of Biochemistry, University of Alberta, 116 Street and 85 Avenue, Edmonton, Alberta, T6G 2H7, Canada
| | - Randall J Weselake
- Department of Agricultural, Food and Nutritional Science, University of Alberta, 116 Street and 85 Avenue, Edmonton, Alberta, T6G 2P5, Canada
| | - Guanqun Chen
- Department of Agricultural, Food and Nutritional Science, University of Alberta, 116 Street and 85 Avenue, Edmonton, Alberta, T6G 2P5, Canada
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9
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Bhatt-Wessel B, Jordan TW, Miller JH, Peng L. Role of DGAT enzymes in triacylglycerol metabolism. Arch Biochem Biophys 2018; 655:1-11. [PMID: 30077544 DOI: 10.1016/j.abb.2018.08.001] [Citation(s) in RCA: 107] [Impact Index Per Article: 17.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2018] [Revised: 07/25/2018] [Accepted: 08/02/2018] [Indexed: 01/22/2023]
Abstract
The esterification of a fatty acyl moiety to diacylglycerol to form triacylglycerol (TAG) is catalysed by two diacylglycerol O-acyltransferases (DGATs) encoded by genes belonging to two distinct gene families. The enzymes are referred to as DGAT1 and DGAT2 in order of their identification. Both proteins are transmembrane proteins localized in the endoplasmic reticulum. Their membrane topologies are however significantly different. This difference is hypothesized to give the two isozymes different abilities to interact with other proteins and organelles and access to different pools of fatty acids, thereby creating a distinction between the enzymes in terms of their role and contribution to lipid metabolism. DGAT1 is proposed to have dual topology contributing to TAG synthesis on both sides of the ER membrane and esterifying only the pre-formed fatty acids. There is evidence to suggest that DGAT2 translocates to the lipid droplet (LD), associates with other proteins, and synthesizes cytosolic and luminal apolipoprotein B associated LD-TAG from both endogenous and exogenous fatty acids. The aim of this review is to differentiate between the two DGAT enzymes by comparing the genes that encode them, their proposed topologies, the proteins they interact with, and their roles in lipid metabolism.
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Affiliation(s)
- Bhumika Bhatt-Wessel
- Centre for Biodiscovery and School of Biological Sciences, Victoria University of Wellington, New Zealand
| | - T William Jordan
- Centre for Biodiscovery and School of Biological Sciences, Victoria University of Wellington, New Zealand
| | - John H Miller
- Centre for Biodiscovery and School of Biological Sciences, Victoria University of Wellington, New Zealand
| | - Lifeng Peng
- Centre for Biodiscovery and School of Biological Sciences, Victoria University of Wellington, New Zealand.
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10
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Chen G, Xu Y, Siloto RMP, Caldo KMP, Vanhercke T, Tahchy AE, Niesner N, Chen Y, Mietkiewska E, Weselake RJ. High-performance variants of plant diacylglycerol acyltransferase 1 generated by directed evolution provide insights into structure function. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2017; 92:167-177. [PMID: 28755522 DOI: 10.1111/tpj.13652] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/23/2017] [Revised: 06/27/2017] [Accepted: 07/24/2017] [Indexed: 05/08/2023]
Abstract
Diacylglycerol acyltransferase 1 (DGAT1) catalyzes the acyl-CoA-dependent biosynthesis of triacylglycerol, the predominant component of seed oil. In some oil crops, including Brassica napus, the level of DGAT1 activity can have a substantial effect on triacylglycerol production. Structure-function insights into DGAT1, however, remain limited because of the lack of a three-dimensional detailed structure for this membrane-bound enzyme. In this study, the amino acid residues governing B. napus DGAT1 (BnaDGAT1) activity were investigated via directed evolution, targeted mutagenesis, in vitro enzymatic assay, topological analysis, and transient expression of cDNA encoding selected enzyme variants in Nicotiana benthamiana. Directed evolution revealed that numerous amino acid residues were associated with increased BnaDGAT1 activity, and 67% of these residues were conserved among plant DGAT1s. The identified amino acid residue substitution sites occur throughout the BnaDGAT1 polypeptide, with 89% of the substitutions located outside the putative substrate binding or active sites. In addition, cDNAs encoding variants I447F or L441P were transiently overexpressed in N. benthamiana leaves, resulting in 33.2 or 70.5% higher triacylglycerol content, respectively, compared with native BnaDGAT1. Overall, the results provide novel insights into amino acid residues underlying plant DGAT1 function and performance-enhanced BnaDGAT1 variants for increasing vegetable oil production.
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Affiliation(s)
- Guanqun Chen
- Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton Alberta, Canada, T6G 2P5
| | - Yang Xu
- Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton Alberta, Canada, T6G 2P5
| | - Rodrigo M P Siloto
- Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton Alberta, Canada, T6G 2P5
| | - Kristian Mark P Caldo
- Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton Alberta, Canada, T6G 2P5
| | | | | | | | - Yongyan Chen
- Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton Alberta, Canada, T6G 2P5
| | - Elzbieta Mietkiewska
- Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton Alberta, Canada, T6G 2P5
| | - Randall J Weselake
- Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton Alberta, Canada, T6G 2P5
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11
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Xu Y, Chen G, Greer MS, Caldo KMP, Ramakrishnan G, Shah S, Wu L, Lemieux MJ, Ozga J, Weselake RJ. Multiple mechanisms contribute to increased neutral lipid accumulation in yeast producing recombinant variants of plant diacylglycerol acyltransferase 1. J Biol Chem 2017; 292:17819-17831. [PMID: 28900030 DOI: 10.1074/jbc.m117.811489] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2017] [Revised: 09/07/2017] [Indexed: 11/06/2022] Open
Abstract
The apparent bottleneck in the accumulation of oil during seed development in some oleaginous plant species is the formation of triacylglycerol (TAG) by the acyl-CoA-dependent acylation of sn-1,2-diacylglycerol catalyzed by diacylglycerol acyltransferase (DGAT, EC 2.3.1.20). Improving DGAT activity using protein engineering could lead to improvements in seed oil yield (e.g. in canola-type Brassica napus). Directed evolution of B. napus DGAT1 (BnaDGAT1) previously revealed that one of the regions where amino acid residue substitutions lead to higher performance in BnaDGAT1 is in the ninth predicted transmembrane domain (PTMD9). In this study, several BnaDGAT1 variants with amino acid residue substitutions in PTMD9 were characterized. Among these enzyme variants, the extent of yeast TAG production was affected by different mechanisms, including increased enzyme activity, increased polypeptide accumulation, and possibly reduced substrate inhibition. The kinetic properties of the BnaDGAT1 variants were affected by the amino acid residue substitutions, and a new kinetic model based on substrate inhibition and sigmoidicity was generated. Based on sequence alignment and further biochemical analysis, the amino acid residue substitutions that conferred increased TAG accumulation were shown to be present in the DGAT1-PTMD9 region of other higher plant species. When amino acid residue substitutions that increased BnaDGAT1 enzyme activity were introduced into recombinant Camelina sativa DGAT1, they also improved enzyme performance. Thus, the knowledge generated from directed evolution of DGAT1 in one plant species can be transferred to other plant species and has potentially broad applications in genetic engineering of oleaginous crops and microorganisms.
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Affiliation(s)
- Yang Xu
- From the Department of Agricultural, Food, and Nutritional Science, University of Alberta, Edmonton, Alberta T6G 2P5
| | - Guanqun Chen
- From the Department of Agricultural, Food, and Nutritional Science, University of Alberta, Edmonton, Alberta T6G 2P5
| | - Michael S Greer
- From the Department of Agricultural, Food, and Nutritional Science, University of Alberta, Edmonton, Alberta T6G 2P5
| | - Kristian Mark P Caldo
- From the Department of Agricultural, Food, and Nutritional Science, University of Alberta, Edmonton, Alberta T6G 2P5.,the Department of Biochemistry, University of Alberta, Edmonton, Alberta T6G 2H7, and
| | - Geetha Ramakrishnan
- From the Department of Agricultural, Food, and Nutritional Science, University of Alberta, Edmonton, Alberta T6G 2P5
| | - Saleh Shah
- From the Department of Agricultural, Food, and Nutritional Science, University of Alberta, Edmonton, Alberta T6G 2P5
| | - Limin Wu
- Crop Pathology and Biotechnology, InnoTech Alberta, Vegreville, Alberta T9C 1T4, Canada
| | - M Joanne Lemieux
- the Department of Biochemistry, University of Alberta, Edmonton, Alberta T6G 2H7, and
| | - Jocelyn Ozga
- From the Department of Agricultural, Food, and Nutritional Science, University of Alberta, Edmonton, Alberta T6G 2P5
| | - Randall J Weselake
- From the Department of Agricultural, Food, and Nutritional Science, University of Alberta, Edmonton, Alberta T6G 2P5,
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12
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Kumagai PS, Araujo APU, Lopes JLS. Going deep into protein secondary structure with synchrotron radiation circular dichroism spectroscopy. Biophys Rev 2017; 9:517-527. [PMID: 28825203 DOI: 10.1007/s12551-017-0314-2] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2017] [Accepted: 08/03/2017] [Indexed: 10/25/2022] Open
Abstract
Circular dichroism (CD) spectroscopy is a fast, powerful, well-established, and widely used analytical technique in the biophysical and structural biology community to study protein secondary structure and to track changes in protein conformation in different environments. The use of the intense light of a synchrotron beam as the light source for collecting CD measurements has emerged as an enhanced method, known as synchrotron radiation circular dichroism (SRCD) spectroscopy, that has several advantages over the conventional CD method, including a significant spectral range extension for data collection, deeper access to the lower limit (cut-off) of conventional CD spectroscopy, an improved signal-to-noise ratio to increase accuracy in the measurements, and the possibility to collect measurements in highly absorbing solutions. In this review, we discuss different applications of the SRCD technique by researchers from Latin America. In this context, we specifically look at the use of this method for examining the secondary structure and conformational behavior of proteins belonging to the four main classes of the hierarchical protein domain classification CATH (Class, Architecture, Topology, Homology) database, focusing on the advantages and improvements associated with SRCD spectroscopy in terms of characterizing proteins composed of different structural elements.
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Affiliation(s)
- Patricia S Kumagai
- Instituto de Física de São Carlos, Universidade de São Paulo, São Paulo, SP, Brazil
| | - Ana P U Araujo
- Instituto de Física de São Carlos, Universidade de São Paulo, São Paulo, SP, Brazil
| | - Jose L S Lopes
- Departamento Física Aplicada, Instituto de Física,, Universidade de São Paulo, Rua do Matão 1371, Cidade Universitária, São Paulo, SP, 05508-090, Brazil.
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13
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Martin P, Palhière I, Maroteau C, Bardou P, Canale-Tabet K, Sarry J, Woloszyn F, Bertrand-Michel J, Racke I, Besir H, Rupp R, Tosser-Klopp G. A genome scan for milk production traits in dairy goats reveals two new mutations in Dgat1 reducing milk fat content. Sci Rep 2017; 7:1872. [PMID: 28500343 PMCID: PMC5431851 DOI: 10.1038/s41598-017-02052-0] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2016] [Accepted: 04/05/2017] [Indexed: 11/21/2022] Open
Abstract
The quantity of milk and milk fat and proteins are particularly important traits in dairy livestock. However, little is known about the regions of the genome that influence these traits in goats. We conducted a genome wide association study in French goats and identified 109 regions associated with dairy traits. For a major region on chromosome 14 closely associated with fat content, the Diacylglycerol O-Acyltransferase 1 (DGAT1) gene turned out to be a functional and positional candidate gene. The caprine reference sequence of this gene was completed and 29 polymorphisms were found in the gene sequence, including two novel exonic mutations: R251L and R396W, leading to substitutions in the protein sequence. The R251L mutation was found in the Saanen breed at a frequency of 3.5% and the R396W mutation both in the Saanen and Alpine breeds at a frequencies of 13% and 7% respectively. The R396W mutation explained 46% of the genetic variance of the trait, and the R251L mutation 6%. Both mutations were associated with a notable decrease in milk fat content. Their causality was then demonstrated by a functional test. These results provide new knowledge on the genetic basis of milk synthesis and will help improve the management of the French dairy goat breeding program.
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Affiliation(s)
- Pauline Martin
- GenPhySE, Université de Toulouse, INRA, INPT, ENVT, Castanet Tolosan, France
| | - Isabelle Palhière
- GenPhySE, Université de Toulouse, INRA, INPT, ENVT, Castanet Tolosan, France
| | - Cyrielle Maroteau
- GenPhySE, Université de Toulouse, INRA, INPT, ENVT, Castanet Tolosan, France
- Division of Molecular and Clinical Medecine, School of Medecine, University of Dundee, Ninewells Hospital and Medical School, Dundee, UK
| | - Philippe Bardou
- GenPhySE, Université de Toulouse, INRA, INPT, ENVT, Castanet Tolosan, France
- INRA, Sigenae, Castanet-Tolosan, France
| | - Kamila Canale-Tabet
- GenPhySE, Université de Toulouse, INRA, INPT, ENVT, Castanet Tolosan, France
| | - Julien Sarry
- GenPhySE, Université de Toulouse, INRA, INPT, ENVT, Castanet Tolosan, France
| | - Florent Woloszyn
- GenPhySE, Université de Toulouse, INRA, INPT, ENVT, Castanet Tolosan, France
| | | | - Ines Racke
- Protein Expression and Purification Core Facility, EMBL Heidelberg, Heidelberg, Germany
| | - Hüseyin Besir
- Protein Expression and Purification Core Facility, EMBL Heidelberg, Heidelberg, Germany
| | - Rachel Rupp
- GenPhySE, Université de Toulouse, INRA, INPT, ENVT, Castanet Tolosan, France
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14
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Aymé L, Jolivet P, Nicaud JM, Chardot T. Molecular Characterization of the Elaeis guineensis Medium-Chain Fatty Acid Diacylglycerol Acyltransferase DGAT1-1 by Heterologous Expression in Yarrowia lipolytica. PLoS One 2015; 10:e0143113. [PMID: 26581109 PMCID: PMC4651311 DOI: 10.1371/journal.pone.0143113] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2015] [Accepted: 11/01/2015] [Indexed: 12/22/2022] Open
Abstract
Diacylglycerol acyltransferases (DGAT) are involved in the acylation of sn-1,2-diacylglycerol. Palm kernel oil, extracted from Elaeis guineensis (oil palm) seeds, has a high content of medium-chain fatty acids mainly lauric acid (C12:0). A putative E. guineensis diacylglycerol acyltransferase gene (EgDGAT1-1) is expressed at the onset of lauric acid accumulation in the seed endosperm suggesting that it is a determinant of medium-chain triacylglycerol storage. To test this hypothesis, we thoroughly characterized EgDGAT1-1 activity through functional complementation of a Yarrowia lipolytica mutant strain devoid of neutral lipids. EgDGAT1-1 expression is sufficient to restore triacylglycerol accumulation in neosynthesized lipid droplets. A comparative functional study with Arabidopsis thaliana DGAT1 highlighted contrasting substrate specificities when the recombinant yeast was cultured in lauric acid supplemented medium. The EgDGAT1-1 expressing strain preferentially accumulated medium-chain triacylglycerols whereas AtDGAT1 expression induced long-chain triacylglycerol storage in Y. lipolytica. EgDGAT1-1 localized to the endoplasmic reticulum where TAG biosynthesis takes place. Reestablishing neutral lipid accumulation in the Y. lipolytica mutant strain did not induce major reorganization of the yeast microsomal proteome. Overall, our findings demonstrate that EgDGAT1-1 is an endoplasmic reticulum DGAT with preference for medium-chain fatty acid substrates, in line with its physiological role in palm kernel. The characterized EgDGAT1-1 could be used to promote medium-chain triacylglycerol accumulation in microbial-produced oil for industrial chemicals and cosmetics.
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Affiliation(s)
- Laure Aymé
- INRA, UMR1318, Institut Jean-Pierre Bourgin Saclay Plant Sciences, Versailles, France
- AgroParisTech, UMR1318, Institut Jean-Pierre Bourgin, Versailles, France
| | - Pascale Jolivet
- INRA, UMR1318, Institut Jean-Pierre Bourgin Saclay Plant Sciences, Versailles, France
- AgroParisTech, UMR1318, Institut Jean-Pierre Bourgin, Versailles, France
| | | | - Thierry Chardot
- INRA, UMR1318, Institut Jean-Pierre Bourgin Saclay Plant Sciences, Versailles, France
- AgroParisTech, UMR1318, Institut Jean-Pierre Bourgin, Versailles, France
- * E-mail:
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15
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Aznar-Moreno J, Denolf P, Van Audenhove K, De Bodt S, Engelen S, Fahy D, Wallis JG, Browse J. Type 1 diacylglycerol acyltransferases of Brassica napus preferentially incorporate oleic acid into triacylglycerol. JOURNAL OF EXPERIMENTAL BOTANY 2015; 66. [PMID: 26195728 PMCID: PMC4588894 DOI: 10.1093/jxb/erv363] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
DGAT1 enzymes (acyl-CoA:diacylglycerol acyltransferase 1, EC 2.3.1.20) catalyse the formation of triacylglycerols (TAGs), the most abundant lipids in vegetable oils. Thorough understanding of the enzymology of oil accumulation is critical to the goal of modifying oilseeds for improved vegetable oil production. Four isoforms of BnDGAT1, the final and rate-limiting step in triacylglycerol synthesis, were characterized from Brassica napus, one of the world's most important oilseed crops. Transcriptional profiling of developing B. napus seeds indicated two genes, BnDGAT1-1 and BnDGAT1-2, with high expression and two, BnDGAT1-3 and BnDGAT1-4, with low expression. The activities of each BnDGAT1 isozyme were characterized following expression in a strain of yeast deficient in TAG synthesis. TAG from B. napus seeds contain only 10% palmitic acid (16:0) at the sn-3 position, so it was surprising that all four BnDGAT1 isozymes exhibited strong (4- to 7-fold) specificity for 16:0 over oleic acid (18:1) as the acyl-CoA substrate. However, the ratio of 18:1-CoA to 16:0-CoA in B. napus seeds during the peak period of TAG synthesis is 3:1. When substrate selectivity assays were conducted with 18:1-CoA and 16:0-CoA in a 3:1 ratio, the four isozymes incorporated 18:1 in amounts 2- to 5-fold higher than 16:0. This strong sensitivity of the BnDGAT1 isozymes to the relative concentrations of acyl-CoA substrates substantially explains the observed fatty acid composition of B. napus seed oil. Understanding these enzymes that are critical for triacylglycerol synthesis will facilitate genetic and biotechnological manipulations to improve this oilseed crop.
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Affiliation(s)
- Jose Aznar-Moreno
- Institute of Biological Chemistry, Washington State University, Pullman, WA 99164-6340, USA
| | - Peter Denolf
- Bayer CropScience N.V., Technologiepark 38, B-9052 Ghent, Belgium
| | | | - Stefanie De Bodt
- Bayer CropScience N.V., Technologiepark 38, B-9052 Ghent, Belgium
| | - Steven Engelen
- Bayer CropScience N.V., Technologiepark 38, B-9052 Ghent, Belgium
| | - Deirdre Fahy
- Institute of Biological Chemistry, Washington State University, Pullman, WA 99164-6340, USA
| | - James G Wallis
- Institute of Biological Chemistry, Washington State University, Pullman, WA 99164-6340, USA
| | - John Browse
- Institute of Biological Chemistry, Washington State University, Pullman, WA 99164-6340, USA
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16
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Lopes JLS, Araujo APU, Jameson DM. Investigation of the conformational flexibility of DGAT1 peptides using tryptophan fluorescence. Methods Appl Fluoresc 2015; 3:025003. [PMID: 29148488 DOI: 10.1088/2050-6120/3/2/025003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The conformational behavior of synthetic peptides corresponding to the putative binding sites of the diacylglycerol acyltransferase 1 enzyme (a polytopic integral membrane protein) was investigated using steady-state and time-resolved fluorescence spectroscopies. Three small linear peptides with 13, 15 and 22 amino acid residues, containing one, two and three Trp residues, respectively, were studied in aqueous solution, in the absence and presence of model membranes. The high flexibility and unordered conformation of the peptides in solution were confirmed by the low Trp polarization values, the high accessibility to water-soluble quencher, and the fast rotational correlation times of the Trp residues. However, upon binding to the lipid systems, the Trp residues were incorporated within the acyl hydrophobic core and their lifetimes and rotational correlation times increased. Phasor plots were employed to analyze intensity decay of peptide-lipid binding and provided a trajectory, in phasor space, that lies along a line connecting the points of the free and bound peptide. This trajectory was analyzed to determine the association constant of the peptide to the model membrane.
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Affiliation(s)
- Jose L S Lopes
- Institute of Physics of Sao Carlos, University of Sao Paulo, Sao Carlos, SP, Brazil. Department of Cell and Molecular Biology, University of Hawaii at Manoa, Honolulu, HI, USA
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17
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Lopes JLS, Beltramini LM, Wallace BA, Araujo APU. Deconstructing the DGAT1 enzyme: membrane interactions at substrate binding sites. PLoS One 2015; 10:e0118407. [PMID: 25719207 PMCID: PMC4342243 DOI: 10.1371/journal.pone.0118407] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2014] [Accepted: 01/16/2015] [Indexed: 12/02/2022] Open
Abstract
Diacylglycerol acyltransferase 1 (DGAT1) is a key enzyme in the triacylglyceride synthesis pathway. Bovine DGAT1 is an endoplasmic reticulum membrane-bound protein associated with the regulation of fat content in milk and meat. The aim of this study was to evaluate the interaction of DGAT1 peptides corresponding to putative substrate binding sites with different types of model membranes. Whilst these peptides are predicted to be located in an extramembranous loop of the membrane-bound protein, their hydrophobic substrates are membrane-bound molecules. In this study, peptides corresponding to the binding sites of the two substrates involved in the reaction were examined in the presence of model membranes in order to probe potential interactions between them that might influence the subsequent binding of the substrates. Whilst the conformation of one of the peptides changed upon binding several types of micelles regardless of their surface charge, suggesting binding to hydrophobic domains, the other peptide bound strongly to negatively-charged model membranes. This binding was accompanied by a change in conformation, and produced leakage of the liposome-entrapped dye calcein. The different hydrophobic and electrostatic interactions observed suggest the peptides may be involved in the interactions of the enzyme with membrane surfaces, facilitating access of the catalytic histidine to the triacylglycerol substrates.
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Affiliation(s)
| | | | - Bonnie A. Wallace
- Institute of Structural and Molecular Biology, Birkbeck College, University of London, London, United Kingdom
- * E-mail: (APUA); (BAW)
| | - Ana P. U. Araujo
- Instituto de Física de São Carlos, USP, São Carlos, Brazil
- * E-mail: (APUA); (BAW)
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