1
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Doron L, Kerfeld CA. Bacterial microcompartments as a next-generation metabolic engineering tool: utilizing nature's solution for confining challenging catabolic pathways. Biochem Soc Trans 2024; 52:997-1010. [PMID: 38813858 DOI: 10.1042/bst20230229] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2024] [Revised: 05/17/2024] [Accepted: 05/20/2024] [Indexed: 05/31/2024]
Abstract
Advancements in synthetic biology have facilitated the incorporation of heterologous metabolic pathways into various bacterial chassis, leading to the synthesis of targeted bioproducts. However, total output from heterologous production pathways can suffer from low flux, enzyme promiscuity, formation of toxic intermediates, or intermediate loss to competing reactions, which ultimately hinder their full potential. The self-assembling, easy-to-modify, protein-based bacterial microcompartments (BMCs) offer a sophisticated way to overcome these obstacles by acting as an autonomous catalytic module decoupled from the cell's regulatory and metabolic networks. More than a decade of fundamental research on various types of BMCs, particularly structural studies of shells and their self-assembly, the recruitment of enzymes to BMC shell scaffolds, and the involvement of ancillary proteins such as transporters, regulators, and activating enzymes in the integration of BMCs into the cell's metabolism, has significantly moved the field forward. These advances have enabled bioengineers to design synthetic multi-enzyme BMCs to promote ethanol or hydrogen production, increase cellular polyphosphate levels, and convert glycerol to propanediol or formate to pyruvate. These pioneering efforts demonstrate the enormous potential of synthetic BMCs to encapsulate non-native multi-enzyme biochemical pathways for the synthesis of high-value products.
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Affiliation(s)
- Lior Doron
- MSU-DOE Plant Research Laboratory, Michigan State University, East Lansing, MI, U.S.A
| | - Cheryl A Kerfeld
- MSU-DOE Plant Research Laboratory, Michigan State University, East Lansing, MI, U.S.A
- Environmental Genomics and Systems Biology and Molecular Biophysics and Integrative Bioimaging Divisions, Lawrence Berkeley National Laboratory, Berkeley, CA, U.S.A
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI, U.S.A
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2
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Shinde YD, Chowdhury C. Potential utility of bacterial protein nanoreactor for sustainable in-situ biocatalysis in wide range of bioprocess conditions. Enzyme Microb Technol 2024; 173:110354. [PMID: 37988973 DOI: 10.1016/j.enzmictec.2023.110354] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2023] [Revised: 09/30/2023] [Accepted: 11/04/2023] [Indexed: 11/23/2023]
Abstract
Bacterial microcompartments (MCPs) are proteinaceous organelles that natively encapsulates the enzymes, substrates, and cofactors within a protein shell. They optimize the reaction rates by enriching the substrate in the vicinity of enzymes to increase the yields of the product and mitigate the outward diffusion of the toxic or volatile intermediates. The shell protein subunits of MCP shell are selectively permeable and have specialized pores for the selective inward diffusion of substrates and products release. Given their attributes, MCPs have been recently explored as potential candidates as subcellular nano-bioreactor for the enhanced production of industrially important molecules by exercising pathway encapsulation. In the current study, MCPs have been shown to sustain enzyme activity for extended periods, emphasizing their durability against a range of physical challenges such as temperature, pH and organic solvents. The significance of an intact shell in conferring maximum protection is highlighted by analyzing the differences in enzyme activities inside the intact and broken shell. Moreover, a minimal synthetic shell was designed with recruitment of a heterologous enzyme cargo to demonstrate the improved durability of the enzyme. The encapsulated enzyme was shown to be more stable than its free counterpart under the aforementioned conditions. Bacterial MCP-mediated encapsulation can serve as a potential strategy to shield the enzymes used under extreme conditions by maintaining the internal microenvironment and enhancing their cycle life, thereby opening new means for stabilizing, and reutilizing the enzymes in several bioprocess industries.
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Affiliation(s)
- Yashodhara D Shinde
- Biochemical Sciences Division, CSIR-National Chemical Laboratory, Pune, MH 411008, India
| | - Chiranjit Chowdhury
- Biochemical Sciences Division, CSIR-National Chemical Laboratory, Pune, MH 411008, India; Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, UP 201002, India.
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3
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Zakaszewski D, Koziej L, Pankowski J, Malolan VV, Gämperli N, Heddle JG, Hilvert D, Azuma Y. Complementary charge-driven encapsulation of functional protein by engineered protein cages in cellulo. J Mater Chem B 2023; 11:6540-6546. [PMID: 37427706 DOI: 10.1039/d3tb00754e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/11/2023]
Abstract
Charge-driven inclusion complex formation in live cells was examined using a degradation-prone fluorescent protein and a series of protein cages. The results show that sufficiently strong host-guest ionic interaction and an intact shell-like structure are crucial for the protective guest encapsulation.
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Affiliation(s)
- Daniel Zakaszewski
- Malopolska Centre of Biotechnology (MCB), Jagiellonian University, Gronostajowa 7A, 30387 Krakow, Poland.
- Doctoral School of Exact and Natural Sciences, Jagiellonian University, Prof. S. Łojasiewicza 11, 30348 Krakow, Poland
| | - Lukasz Koziej
- Malopolska Centre of Biotechnology (MCB), Jagiellonian University, Gronostajowa 7A, 30387 Krakow, Poland.
| | - Jędrzej Pankowski
- Malopolska Centre of Biotechnology (MCB), Jagiellonian University, Gronostajowa 7A, 30387 Krakow, Poland.
- Faculty of Biochemistry, Biophysics, sand Biotechnology, Jagiellonian University, Gronostajowa 7, 30387 Krakow, Poland
| | - V Vishal Malolan
- Malopolska Centre of Biotechnology (MCB), Jagiellonian University, Gronostajowa 7A, 30387 Krakow, Poland.
- Doctoral School of Exact and Natural Sciences, Jagiellonian University, Prof. S. Łojasiewicza 11, 30348 Krakow, Poland
| | - Nina Gämperli
- Laboratory of Organic Chemistry, ETH Zurich, 8093 Zurich, Switzerland
| | - Jonathan G Heddle
- Malopolska Centre of Biotechnology (MCB), Jagiellonian University, Gronostajowa 7A, 30387 Krakow, Poland.
| | - Donald Hilvert
- Laboratory of Organic Chemistry, ETH Zurich, 8093 Zurich, Switzerland
| | - Yusuke Azuma
- Malopolska Centre of Biotechnology (MCB), Jagiellonian University, Gronostajowa 7A, 30387 Krakow, Poland.
- Laboratory of Organic Chemistry, ETH Zurich, 8093 Zurich, Switzerland
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4
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Abrahamson CH, Palmero BJ, Kennedy NW, Tullman-Ercek D. Theoretical and Practical Aspects of Multienzyme Organization and Encapsulation. Annu Rev Biophys 2023; 52:553-572. [PMID: 36854212 DOI: 10.1146/annurev-biophys-092222-020832] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/02/2023]
Abstract
The advent of biotechnology has enabled metabolic engineers to assemble heterologous pathways in cells to produce a variety of products of industrial relevance, often in a sustainable way. However, many pathways face challenges of low product yield. These pathways often suffer from issues that are difficult to optimize, such as low pathway flux and off-target pathway consumption of intermediates. These issues are exacerbated by the need to balance pathway flux with the health of the cell, particularly when a toxic intermediate builds up. Nature faces similar challenges and has evolved spatial organization strategies to increase metabolic pathway flux and efficiency. Inspired by these strategies, bioengineers have developed clever strategies to mimic spatial organization in nature. This review explores the use of spatial organization strategies, including protein scaffolding and protein encapsulation inside of proteinaceous shells, toward overcoming bottlenecks in metabolic engineering efforts.
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Affiliation(s)
- Charlotte H Abrahamson
- Department of Chemical and Biological Engineering, Northwestern University, Evanston, Illinois, USA;
| | - Brett J Palmero
- Interdisciplinary Biological Sciences Graduate Program, Northwestern University, Evanston, Illinois, USA
| | - Nolan W Kennedy
- Interdisciplinary Biological Sciences Graduate Program, Northwestern University, Evanston, Illinois, USA
| | - Danielle Tullman-Ercek
- Department of Chemical and Biological Engineering, Northwestern University, Evanston, Illinois, USA;
- Center for Synthetic Biology, Northwestern University, Evanston, Illinois, USA
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5
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Wang R, Liu X, Lv B, Sun W, Li C. Designing Intracellular Compartments for Efficient Engineered Microbial Cell Factories. ACS Synth Biol 2023; 12:1378-1395. [PMID: 37083286 DOI: 10.1021/acssynbio.2c00671] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/22/2023]
Abstract
With the rapid development of synthetic biology, various kinds of microbial cell factories (MCFs) have been successfully constructed to produce high-value-added compounds. However, the complexity of metabolic regulation and pathway crosstalk always cause issues such as intermediate metabolite accumulation, byproduct generation, and metabolic burden in MCFs, resulting in low efficiencies and low yields of industrial biomanufacturing. Such issues could be solved by spatially rearranging the pathways using intracellular compartments. In this review, design strategies are summarized and discussed based on the types and characteristics of natural and artificial subcellular compartments. This review systematically presents information for the construction of efficient MCFs with intracellular compartments in terms of four aspects of design strategy goals: (1) improving local reactant concentration; (2) intercepting and isolating competing pathways; (3) providing specific reaction substances and environments; and (4) storing and accumulating products.
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Affiliation(s)
- Ruwen Wang
- Key Laboratory of Medical Molecule Science and Pharmaceutical Engineering, Ministry of Industry and Information Technology, Institute of Biochemical Engineering, School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing, 100081, PR China
| | - Xin Liu
- Key Lab for Industrial Biocatalysis, Ministry of Education, Department of Chemical Engineering, Tsinghua University, Beijing, 100084, PR China
| | - Bo Lv
- Key Laboratory of Medical Molecule Science and Pharmaceutical Engineering, Ministry of Industry and Information Technology, Institute of Biochemical Engineering, School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing, 100081, PR China
| | - Wentao Sun
- Key Lab for Industrial Biocatalysis, Ministry of Education, Department of Chemical Engineering, Tsinghua University, Beijing, 100084, PR China
| | - Chun Li
- Key Laboratory of Medical Molecule Science and Pharmaceutical Engineering, Ministry of Industry and Information Technology, Institute of Biochemical Engineering, School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing, 100081, PR China
- Key Lab for Industrial Biocatalysis, Ministry of Education, Department of Chemical Engineering, Tsinghua University, Beijing, 100084, PR China
- Center for Synthetic and System Biology, Tsinghua University, Beijing, 100084, PR China
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6
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Kalathil S, Miller M, Reisner E. Microbial Fermentation of Polyethylene Terephthalate (PET) Plastic Waste for the Production of Chemicals or Electricity. Angew Chem Int Ed Engl 2022; 61:e202211057. [PMID: 36103351 PMCID: PMC9828132 DOI: 10.1002/anie.202211057] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2022] [Indexed: 01/12/2023]
Abstract
Ideonella sakaiensis (I. sakaiensis) can grow on polyethylene terephthalate (PET) as the major carbon and energy source. Previous work has shown that PET conversion in the presence of oxygen released carbon dioxide and water while yielding adenosine triphosphate (ATP) through oxidative phosphorylation. This study demonstrates that I. sakaiensis is a facultative anaerobe that ferments PET to the feedstock chemicals acetate and ethanol in the absence of oxygen. In addition to PET, the pure monomer ethylene glycol (EG), the intermediate product ethanol, and the carbohydrate fermentation test substance maltose can also serve as fermenting substrates. Co-culturing of I. sakaiensis with the electrogenic and acetate-consuming Geobacter sulfurreducens produced electricity from PET or EG. This newly identified plastic fermentation process by I. sakaiensis provides thus a novel biosynthetic route to produce high-value chemicals or electricity from plastic waste streams.
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Affiliation(s)
- Shafeer Kalathil
- Yusuf Hamied Department of ChemistryUniversity of CambridgeCambridgeCB2 1EWUK
| | - Melanie Miller
- Yusuf Hamied Department of ChemistryUniversity of CambridgeCambridgeCB2 1EWUK
| | - Erwin Reisner
- Yusuf Hamied Department of ChemistryUniversity of CambridgeCambridgeCB2 1EWUK
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7
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Costa FG, Escalante-Semerena JC. Localization and interaction studies of the Salmonella enterica ethanolamine ammonia-lyase (EutBC), its reactivase (EutA), and the EutT corrinoid adenosyltransferase. Mol Microbiol 2022; 118:191-207. [PMID: 35785499 PMCID: PMC9481676 DOI: 10.1111/mmi.14962] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2022] [Revised: 06/29/2022] [Accepted: 06/30/2022] [Indexed: 11/28/2022]
Abstract
Some prokaryotes compartmentalize select metabolic capabilities. Salmonella enterica subspecies enterica serovar Typhimurium LT2 (hereafter S. Typhimurium) catabolizes ethanolamine (EA) within a proteinaceous compartment that we refer to as the ethanolamine utilization (Eut) metabolosome. EA catabolism is initiated by the adenosylcobalamin (AdoCbl)-dependent ethanolamine ammonia-lyase (EAL), which deaminates EA via an adenosyl radical mechanism to yield acetaldehyde plus ammonia. This adenosyl radical can be quenched, requiring the replacement of AdoCbl by the ATP-dependent EutA reactivase. During growth on ethanolamine, S. Typhimurium synthesizes AdoCbl from cobalamin (Cbl) using the ATP:Co(I)rrinoid adenosyltransferase (ACAT) EutT. It is known that EAL localizes to the metabolosome, however, prior to this work, it was unclear where EutA and EutT localized, and whether they interacted with EAL. Here, we provide evidence that EAL, EutA, and EutT localize to the Eut metabolosome, and that EutA interacts directly with EAL. We did not observe interactions between EutT and EAL nor between EutT and the EutA/EAL complex. However, growth phenotypes of a ΔeutT mutant strain show that EutT is critical for efficient ethanolamine catabolism. This work provides a preliminary understanding of the dynamics of AdoCbl synthesis and its uses within the Eut metabolosome.
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Affiliation(s)
- Flavia G. Costa
- Department of Microbiology, University of Georgia, Athens, GA, USA 30602
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8
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Trettel DS, Resager W, Ueberheide BM, Jenkins CC, Winkler WC. Chemical probing provides insight into the native assembly state of a bacterial microcompartment. Structure 2022; 30:537-550.e5. [PMID: 35216657 PMCID: PMC8995372 DOI: 10.1016/j.str.2022.02.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2021] [Revised: 12/08/2021] [Accepted: 01/28/2022] [Indexed: 11/28/2022]
Abstract
Bacterial microcompartments (BMCs) are widespread in bacteria and are used for a variety of metabolic purposes, including catabolism of host metabolites. A suite of proteins self-assembles into the shell and cargo layers of BMCs. However, the native assembly state of these large complexes remains to be elucidated. Herein, chemical probes were used to observe structural features of a native BMC. While the exterior could be demarcated with fluorophores, the interior was unexpectedly permeable, suggesting that the shell layer may be more dynamic than previously thought. This allowed access to cross-linking chemical probes, which were analyzed to uncover the protein interactome. These cross-links revealed a complex multivalent network among cargo proteins that contained encapsulation peptides and demonstrated that the shell layer follows discrete rules in its assembly. These results are consistent overall with a model in which biomolecular condensation drives interactions of cargo proteins before envelopment by shell layer proteins.
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Affiliation(s)
- Daniel S Trettel
- Department of Chemistry and Biochemistry, University of Maryland, College Park, MD 20742, USA
| | - William Resager
- New York University Grossman School of Health, NYU Langone Health, New York, NY 10016, USA
| | - Beatrix M Ueberheide
- New York University Grossman School of Health, NYU Langone Health, New York, NY 10016, USA; Department of Biochemistry and Molecular Pharmacology, New York University Grossman School of Medicine, New York, NY 10016, USA; Department of Neurology, New York University Grossman School of Medicine, New York, NY 10016, USA
| | - Conor C Jenkins
- Department of Chemistry and Biochemistry, University of Maryland, College Park, MD 20742, USA
| | - Wade C Winkler
- Department of Chemistry and Biochemistry, University of Maryland, College Park, MD 20742, USA; Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, MD 20742, USA.
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9
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Kennedy NW, Mills CE, Nichols TM, Abrahamson CH, Tullman-Ercek D. Bacterial microcompartments: tiny organelles with big potential. Curr Opin Microbiol 2021; 63:36-42. [PMID: 34126434 DOI: 10.1016/j.mib.2021.05.010] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2020] [Revised: 04/13/2021] [Accepted: 05/17/2021] [Indexed: 11/28/2022]
Abstract
Organization of metabolic processes within the space of a cell is critical for the survival of many organisms. In bacteria, spatial organization is achieved via proteinaceous organelles called bacterial microcompartments, which encapsulate pathway enzymes, substrates, and co-factors to drive the safe and efficient metabolism of niche carbon sources. Microcompartments are self-assembled from shell proteins that encapsulate a core comprising various enzymes. This review discusses how recent advances in understanding microcompartment structure and assembly have informed engineering efforts to repurpose compartments and compartment-based structures for non-native functions. These advances, both in understanding of the native structure and function of compartments, as well as in the engineering of new functions, will pave the way for the use of these structures in bacterial cell factories.
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Affiliation(s)
- Nolan W Kennedy
- Interdisciplinary Biological Sciences Graduate Program, Northwestern University, 2205 Tech Drive, 2-100 Hogan Hall, Evanston, IL, 60208, USA
| | - Carolyn E Mills
- Department of Chemical and Biological Engineering, Northwestern University, 2145 Sheridan Road, Technological Institute E136, Evanston, IL, 60208, USA
| | - Taylor M Nichols
- Department of Chemical and Biological Engineering, Northwestern University, 2145 Sheridan Road, Technological Institute E136, Evanston, IL, 60208, USA
| | - Charlotte H Abrahamson
- Department of Chemical and Biological Engineering, Northwestern University, 2145 Sheridan Road, Technological Institute E136, Evanston, IL, 60208, USA
| | - Danielle Tullman-Ercek
- Department of Chemical and Biological Engineering, Northwestern University, 2145 Sheridan Road, Technological Institute E136, Evanston, IL, 60208, USA; Center for Synthetic Biology, Northwestern University, 2145 Sheridan Road, Technological Institute B486, Evanston, IL, 60208, USA.
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10
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Sun H, Cui N, Han SJ, Chen ZP, Xia LY, Chen Y, Jiang YL, Zhou CZ. Complex structure reveals CcmM and CcmN form a heterotrimeric adaptor in β-carboxysome. Protein Sci 2021; 30:1566-1576. [PMID: 33928692 DOI: 10.1002/pro.4090] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2021] [Revised: 04/14/2021] [Accepted: 04/22/2021] [Indexed: 11/09/2022]
Abstract
Carboxysome is an icosahedral self-assembled microcompartment that sequesters RuBisCO and carbonic anhydrases within a selectively permeable protein shell. The scaffolding proteins, CcmM, and CcmN were proposed to act as adaptors that crosslink the enzymatic core to shell facets. However, the details of interaction pattern remain unknown. Here we obtained a stable heterotrimeric complex of CcmM γ-carbonic anhydrase domain (termed CcmMNT ) and CcmN, with a 1:2 stoichiometry, which interacts with the shell proteins CcmO and CcmL in vitro. The 2.9 Å crystal structure of this heterotrimer revealed an asymmetric bundle composed of one CcmMNT and two CcmN subunits, all of which adopt a triangular left-handed β-helical barrel structure. The central CcmN subunit packs against CcmMNT and another CcmN subunit via a wall-to-edge or wall-to-wall pattern, respectively. Together with previous findings, we propose CcmMNT -CcmN functions as an adaptor to facilitate the recruitment of shell proteins and the assembly of intact β-carboxysome.
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Affiliation(s)
- Hui Sun
- Hefei National Laboratory for Physical Sciences at the Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, China
| | - Ning Cui
- Hefei National Laboratory for Physical Sciences at the Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, China
| | - Shu-Jing Han
- Hefei National Laboratory for Physical Sciences at the Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, China
| | - Zhi-Peng Chen
- Hefei National Laboratory for Physical Sciences at the Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, China
| | - Ling-Yun Xia
- Hefei National Laboratory for Physical Sciences at the Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, China
| | - Yuxing Chen
- Hefei National Laboratory for Physical Sciences at the Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, China
| | - Yong-Liang Jiang
- Hefei National Laboratory for Physical Sciences at the Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, China
| | - Cong-Zhao Zhou
- Hefei National Laboratory for Physical Sciences at the Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, China
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11
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Wilson JW. Manipulating microcompartment operons to study mechanism and function. Curr Opin Microbiol 2021; 60:66-72. [PMID: 33611144 DOI: 10.1016/j.mib.2021.01.014] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2020] [Revised: 01/21/2021] [Accepted: 01/27/2021] [Indexed: 12/26/2022]
Abstract
The gene systems that encode functional bacterial microcompartments (BMCs) are typically comprised of between 10-23 genes, often in a contiguous operon. BMC genes can be studied as whole native operons or as subsets of genes that form structures for specific applications. Recent examples of such studies highlight the flexible modular nature of BMC operons/genes and the options that exist to harness their functions via manipulation at the DNA level. This work also demonstrates the transfer and functional expression of BMC operons/genes across bacterial species. Recombineering, DNA synthesis technology, and advanced cloning techniques have all been applied in creative ways to study the nature of BMC mechanism and function.
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Affiliation(s)
- James W Wilson
- Department of Biology, Mendel Hall, Villanova University, 800 Lancaster Avenue, Villanova, PA 19085, USA.
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12
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Kennedy NW, Ikonomova SP, Slininger Lee M, Raeder HW, Tullman-Ercek D. Self-assembling Shell Proteins PduA and PduJ have Essential and Redundant Roles in Bacterial Microcompartment Assembly. J Mol Biol 2020; 433:166721. [PMID: 33227310 DOI: 10.1016/j.jmb.2020.11.020] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2020] [Revised: 11/17/2020] [Accepted: 11/17/2020] [Indexed: 01/21/2023]
Abstract
Protein self-assembly is a common and essential biological phenomenon, and bacterial microcompartments present a promising model system to study this process. Bacterial microcompartments are large, protein-based organelles which natively carry out processes important for carbon fixation in cyanobacteria and the survival of enteric bacteria. These structures are increasingly popular with biological engineers due to their potential utility as nanobioreactors or drug delivery vehicles. However, the limited understanding of the assembly mechanism of these bacterial microcompartments hinders efforts to repurpose them for non-native functions. Here, we comprehensively investigate proteins involved in the assembly of the 1,2-propanediol utilization bacterial microcompartment from Salmonella enterica serovar Typhimurium LT2, one of the most widely studied microcompartment systems. We first demonstrate that two shell proteins, PduA and PduJ, have a high propensity for self-assembly upon overexpression, and we provide a novel method for self-assembly quantification. Using genomic knock-outs and knock-ins, we systematically show that these two proteins play an essential and redundant role in bacterial microcompartment assembly that cannot be compensated by other shell proteins. At least one of the two proteins PduA and PduJ must be present for the bacterial microcompartment shell to assemble. We also demonstrate that assembly-deficient variants of these proteins are unable to rescue microcompartment formation, highlighting the importance of this assembly property. Our work provides insight into the assembly mechanism of these bacterial organelles and will aid downstream engineering efforts.
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Affiliation(s)
- Nolan W Kennedy
- Interdisciplinary Biological Sciences Graduate Program, Northwestern University, Evanston, IL, United States
| | - Svetlana P Ikonomova
- Department of Chemical and Biological Engineering, Northwestern University, Evanston, IL, United States
| | - Marilyn Slininger Lee
- Department of Chemical and Biological Engineering, Northwestern University, Evanston, IL, United States; US Army Combat Capabilities Development Command Chemical Biological Center, Edgewood, MD, United States
| | - Henry W Raeder
- Molecular Biosciences Program, Weinberg College of Arts and Sciences, Northwestern University, Evanston, IL, United States
| | - Danielle Tullman-Ercek
- Department of Chemical and Biological Engineering, Northwestern University, Evanston, IL, United States; Center for Synthetic Biology, Northwestern University, Evanston, IL, United States.
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13
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Groaz A, Moghimianavval H, Tavella F, Giessen TW, Vecchiarelli AG, Yang Q, Liu AP. Engineering spatiotemporal organization and dynamics in synthetic cells. WILEY INTERDISCIPLINARY REVIEWS-NANOMEDICINE AND NANOBIOTECHNOLOGY 2020; 13:e1685. [PMID: 33219745 DOI: 10.1002/wnan.1685] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/27/2020] [Revised: 10/13/2020] [Accepted: 10/30/2020] [Indexed: 12/28/2022]
Abstract
Constructing synthetic cells has recently become an appealing area of research. Decades of research in biochemistry and cell biology have amassed detailed part lists of components involved in various cellular processes. Nevertheless, recreating any cellular process in vitro in cell-sized compartments remains ambitious and challenging. Two broad features or principles are key to the development of synthetic cells-compartmentalization and self-organization/spatiotemporal dynamics. In this review article, we discuss the current state of the art and research trends in the engineering of synthetic cell membranes, development of internal compartmentalization, reconstitution of self-organizing dynamics, and integration of activities across scales of space and time. We also identify some research areas that could play a major role in advancing the impact and utility of engineered synthetic cells. This article is categorized under: Biology-Inspired Nanomaterials > Lipid-Based Structures Biology-Inspired Nanomaterials > Protein and Virus-Based Structures.
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Affiliation(s)
| | | | | | | | | | - Qiong Yang
- University of Michigan, Ann Arbor, Michigan, USA
| | - Allen P Liu
- University of Michigan, Ann Arbor, Michigan, USA
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14
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Stewart KL, Stewart AM, Bobik TA. Prokaryotic Organelles: Bacterial Microcompartments in E. coli and Salmonella. EcoSal Plus 2020; 9:10.1128/ecosalplus.ESP-0025-2019. [PMID: 33030141 PMCID: PMC7552817 DOI: 10.1128/ecosalplus.esp-0025-2019] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2020] [Indexed: 02/07/2023]
Abstract
Bacterial microcompartments (MCPs) are proteinaceous organelles consisting of a metabolic pathway encapsulated within a selectively permeable protein shell. Hundreds of species of bacteria produce MCPs of at least nine different types, and MCP metabolism is associated with enteric pathogenesis, cancer, and heart disease. This review focuses chiefly on the four types of catabolic MCPs (metabolosomes) found in Escherichia coli and Salmonella: the propanediol utilization (pdu), ethanolamine utilization (eut), choline utilization (cut), and glycyl radical propanediol (grp) MCPs. Although the great majority of work done on catabolic MCPs has been carried out with Salmonella and E. coli, research outside the group is mentioned where necessary for a comprehensive understanding. Salient characteristics found across MCPs are discussed, including enzymatic reactions and shell composition, with particular attention paid to key differences between classes of MCPs. We also highlight relevant research on the dynamic processes of MCP assembly, protein targeting, and the mechanisms that underlie selective permeability. Lastly, we discuss emerging biotechnology applications based on MCP principles and point out challenges, unanswered questions, and future directions.
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Affiliation(s)
- Katie L. Stewart
- The Roy J. Carver Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames, IA, USA 50011
| | - Andrew M. Stewart
- The Roy J. Carver Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames, IA, USA 50011
| | - Thomas A. Bobik
- The Roy J. Carver Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames, IA, USA 50011
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15
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Kerfeld CA, Sutter M. Engineered bacterial microcompartments: apps for programming metabolism. Curr Opin Biotechnol 2020; 65:225-232. [PMID: 32554213 PMCID: PMC7719235 DOI: 10.1016/j.copbio.2020.05.001] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2020] [Revised: 05/04/2020] [Accepted: 05/06/2020] [Indexed: 12/12/2022]
Abstract
Bacterial Microcompartments (BMCs) are used by diverse bacteria to compartmentalize enzymatic reactions, functioning analogously to the organelles of eukaryotes. The bounding membrane and encapsulated components are composed entirely of protein, which makes them ideal targets for modification by genetic engineering. In contrast to viruses, in which generally only one protein forms the capsid, the shells of BMCs consist of a variety of shell proteins, each a potential unit of selection. Despite their differences in permeability, the shell proteins are surprisingly interchangeable. Recent developments have shown that they are also highly amenable to engineered modifications which poise them for a variety of biotechnological applications. Given their modular structure, with a module defined as a semi-autonomous functional unit, BMCs can be considered apps for programming metabolism that can be de-bugged by adaptive evolution.
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Affiliation(s)
- Cheryl A Kerfeld
- MSU-DOE Plant Research Laboratory and Department of Biochemistry & Molecular Biology, Michigan State University, East Lansing, MI, USA; Environmental Genomics and Systems Biology and Molecular Biophysics and Integrated Bioimaging Divisions, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, USA.
| | - Markus Sutter
- MSU-DOE Plant Research Laboratory and Department of Biochemistry & Molecular Biology, Michigan State University, East Lansing, MI, USA; Environmental Genomics and Systems Biology and Molecular Biophysics and Integrated Bioimaging Divisions, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, USA
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16
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Nichols TM, Kennedy NW, Tullman-Ercek D. A genomic integration platform for heterologous cargo encapsulation in 1,2-propanediol utilization bacterial microcompartments. Biochem Eng J 2020. [DOI: 10.1016/j.bej.2020.107496] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
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17
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Lv X, Cui S, Gu Y, Li J, Du G, Liu L. Enzyme Assembly for Compartmentalized Metabolic Flux Control. Metabolites 2020; 10:E125. [PMID: 32224973 PMCID: PMC7241084 DOI: 10.3390/metabo10040125] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2020] [Revised: 03/25/2020] [Accepted: 03/25/2020] [Indexed: 11/16/2022] Open
Abstract
Enzyme assembly by ligand binding or physically sequestrating enzymes, substrates, or metabolites into isolated compartments can bring key molecules closer to enhance the flux of a metabolic pathway. The emergence of enzyme assembly has provided both opportunities and challenges for metabolic engineering. At present, with the development of synthetic biology and systems biology, a variety of enzyme assembly strategies have been proposed, from the initial direct enzyme fusion to scaffold-free assembly, as well as artificial scaffolds, such as nucleic acid/protein scaffolds, and even some more complex physical compartments. These assembly strategies have been explored and applied to the synthesis of various important bio-based products, and have achieved different degrees of success. Despite some achievements, enzyme assembly, especially in vivo, still has many problems that have attracted significant attention from researchers. Here, we focus on some selected examples to review recent research on scaffold-free strategies, synthetic artificial scaffolds, and physical compartments for enzyme assembly or pathway sequestration, and we discuss their notable advances. In addition, the potential applications and challenges in the applications are highlighted.
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Affiliation(s)
- Xueqin Lv
- Key Laboratory of Carbohydrate Chemistry and Biotechnology, Ministry of Education, Jiangnan University, Wuxi 214122, China; (X.L.); (S.C.); (Y.G.); (J.L.); (G.D.)
- Key Laboratory of Industrial Biotechnology, Ministry of Education, Jiangnan University, Wuxi 214122, China
| | - Shixiu Cui
- Key Laboratory of Carbohydrate Chemistry and Biotechnology, Ministry of Education, Jiangnan University, Wuxi 214122, China; (X.L.); (S.C.); (Y.G.); (J.L.); (G.D.)
- Key Laboratory of Industrial Biotechnology, Ministry of Education, Jiangnan University, Wuxi 214122, China
| | - Yang Gu
- Key Laboratory of Carbohydrate Chemistry and Biotechnology, Ministry of Education, Jiangnan University, Wuxi 214122, China; (X.L.); (S.C.); (Y.G.); (J.L.); (G.D.)
- Key Laboratory of Industrial Biotechnology, Ministry of Education, Jiangnan University, Wuxi 214122, China
| | - Jianghua Li
- Key Laboratory of Carbohydrate Chemistry and Biotechnology, Ministry of Education, Jiangnan University, Wuxi 214122, China; (X.L.); (S.C.); (Y.G.); (J.L.); (G.D.)
- Key Laboratory of Industrial Biotechnology, Ministry of Education, Jiangnan University, Wuxi 214122, China
| | - Guocheng Du
- Key Laboratory of Carbohydrate Chemistry and Biotechnology, Ministry of Education, Jiangnan University, Wuxi 214122, China; (X.L.); (S.C.); (Y.G.); (J.L.); (G.D.)
- Key Laboratory of Industrial Biotechnology, Ministry of Education, Jiangnan University, Wuxi 214122, China
| | - Long Liu
- Key Laboratory of Carbohydrate Chemistry and Biotechnology, Ministry of Education, Jiangnan University, Wuxi 214122, China; (X.L.); (S.C.); (Y.G.); (J.L.); (G.D.)
- Key Laboratory of Industrial Biotechnology, Ministry of Education, Jiangnan University, Wuxi 214122, China
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18
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Apparent size and morphology of bacterial microcompartments varies with technique. PLoS One 2020; 15:e0226395. [PMID: 32150579 PMCID: PMC7062276 DOI: 10.1371/journal.pone.0226395] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2019] [Accepted: 02/25/2020] [Indexed: 12/30/2022] Open
Abstract
Bacterial microcompartments (MCPs) are protein-based organelles that encapsulate metabolic pathways. Metabolic engineers have recently sought to repurpose MCPs to encapsulate heterologous pathways to increase flux through pathways of interest. As MCP engineering becomes more common, standardized methods for analyzing changes to MCPs and interpreting results across studies will become increasingly important. In this study, we demonstrate that different imaging techniques yield variations in the apparent size of purified MCPs from Salmonella enterica serovar Typhimurium LT2, likely due to variations in sample preparation methods. We provide guidelines for preparing samples for MCP imaging and outline expected variations in apparent size and morphology between methods. With this report we aim to establish an aid for comparing results across studies.
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Chowdhury C, Bobik TA. Engineering the PduT shell protein to modify the permeability of the 1,2-propanediol microcompartment of Salmonella. MICROBIOLOGY-SGM 2020; 165:1355-1364. [PMID: 31674899 DOI: 10.1099/mic.0.000872] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Bacterial microcompartments (MCPs) are protein-based organelles that consist of metabolic enzymes encapsulated within a protein shell. The function of MCPs is to optimize metabolic pathways by increasing reaction rates and sequestering toxic pathway intermediates. A substantial amount of effort has been directed toward engineering synthetic MCPs as intracellular nanoreactors for the improved production of renewable chemicals. A key challenge in this area is engineering protein shells that allow the entry of desired substrates. In this study, we used site-directed mutagenesis of the PduT shell protein to remove its central iron-sulfur cluster and create openings (pores) in the shell of the Pdu MCP that have varied chemical properties. Subsequently, in vivo and in vitro studies were used to show that PduT-C38S and PduT-C38A variants increased the diffusion of 1,2-propanediol, propionaldehyde, NAD+ and NADH across the shell of the MCP. In contrast, PduT-C38I and PduT-C38W eliminated the iron-sulfur cluster without altering the permeability of the Pdu MCP, suggesting that the side-chains of C38I and C38W occluded the opening formed by removal of the iron-sulfur cluster. Thus, genetic modification offers an approach to engineering the movement of larger molecules (such as NAD/H) across MCP shells, as well as a method for blocking transport through trimeric bacterial microcompartment (BMC) domain shell proteins.
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Affiliation(s)
- Chiranjit Chowdhury
- Present address: Amity Institute of Molecular Medicine and Stem Cell Research, Amity University Campus, Sector-125, Noida, UP-201313, India.,Roy J. Carver Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames, IA, 50011, USA
| | - Thomas A Bobik
- Roy J. Carver Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames, IA, 50011, USA
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20
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Zeng Z, Smid EJ, Boeren S, Notebaart RA, Abee T. Bacterial Microcompartment-Dependent 1,2-Propanediol Utilization Stimulates Anaerobic Growth of Listeria monocytogenes EGDe. Front Microbiol 2019; 10:2660. [PMID: 31803170 PMCID: PMC6873790 DOI: 10.3389/fmicb.2019.02660] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2019] [Accepted: 10/31/2019] [Indexed: 12/22/2022] Open
Abstract
Bacterial microcompartments (BMCs) are proteinaceous organelles that optimize specific metabolic pathways referred to as metabolosomes involving transient production of toxic volatile metabolites such as aldehydes. Previous bioinformatics analysis predicted the presence of BMCs in 23 bacterial phyla including foodborne pathogens and a link with gene clusters for the utilization of host-derived substrates such as 1,2-propanediol utilization, i.e., the Pdu cluster. Although, transcriptional regulation of the Pdu cluster and its role in Listeria monocytogenes virulence in animal models have recently been reported, the experimental identification and the physiological role of BMCs in L. monocytogenes is still unexplored. Here, we ask whether BMCs could enable utilization of 1,2-propanediol (Pd) in L. monocytogenes under anaerobic conditions. Using L. monocytogenes EGDe as a model strain, we could demonstrate efficient utilization of Pd with concomitant production of 1-propanol and propionate after 24 h of anaerobic growth, while the utilization was significantly reduced in aerobic conditions. In line with this, expression of genes encoding predicted shell proteins and the signature enzyme propanediol dehydratase is upregulated more than 20-fold in cells anaerobically grown in Pdu-induced versus non-induced control conditions. Additional proteomics analysis confirmed the presence of BMC shell proteins and Pdu enzymes in cells that show active degradation of Pd. Furthermore, using transmission electron microscopy, BMC structures have been detected in these cells linking gene expression, protein composition, and BMCs to activation of the Pdu cluster in anaerobic growth of L. monocytogenes. Studies in defined minimal medium with Pd as an energy source showed a significant increase in cell numbers, indicating that Pdu and the predicted generation of ATP in the conversion of propionyl-phosphate to the end product propionate can support anaerobic growth of L. monocytogenes. Our findings may suggest a role for BMC-dependent utilization of Pd in L. monocytogenes growth, transmission, and interaction with the human host.
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Affiliation(s)
- Zhe Zeng
- Laboratory of Food Microbiology, Wageningen University and Research, Wageningen, Netherlands
| | - Eddy J Smid
- Laboratory of Food Microbiology, Wageningen University and Research, Wageningen, Netherlands
| | - Sjef Boeren
- Laboratory of Biochemistry, Wageningen University and Research, Wageningen, Netherlands
| | - Richard A Notebaart
- Laboratory of Food Microbiology, Wageningen University and Research, Wageningen, Netherlands
| | - Tjakko Abee
- Laboratory of Food Microbiology, Wageningen University and Research, Wageningen, Netherlands
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21
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Ferlez B, Sutter M, Kerfeld CA. A designed bacterial microcompartment shell with tunable composition and precision cargo loading. Metab Eng 2019; 54:286-291. [PMID: 31075444 PMCID: PMC6884132 DOI: 10.1016/j.ymben.2019.04.011] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2019] [Revised: 04/09/2019] [Accepted: 04/24/2019] [Indexed: 12/31/2022]
Abstract
Microbes often augment their metabolism by conditionally constructing proteinaceous organelles, known as bacterial microcompartments (BMCs), that encapsulate enzymes to degrade organic compounds or assimilate CO2. BMCs self-assemble and are spatially delimited by a semi-permeable shell made up of hexameric, trimeric, and pentameric shell proteins. Bioengineers aim to recapitulate the organization and efficiency of these complex biological architectures by redesigning the shell to incorporate non-native enzymes from biotechnologically relevant pathways. To meet this challenge, a diverse set of synthetic biology tools are required, including methods to manipulate the properties of the shell as well as target and organize cargo encapsulation. We designed and determined the crystal structure of a synthetic shell protein building block with an inverted sidedness of its N- and C-terminal residues relative to its natural counterpart; the inversion targets genetically fused protein cargo to the lumen of the shell. Moreover, the titer of fluorescent protein cargo encapsulated using this strategy is controllable using an inducible tetracycline promoter. These results expand the available set of building blocks for precision engineering of BMC-based nanoreactors and are compatible with orthogonal methods which will facilitate the installation and organization of multi-enzyme pathways.
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Affiliation(s)
- Bryan Ferlez
- MSU-DOE Plant Research Laboratory, Michigan State University, 612 Wilson Road, East Lansing, MI 48824, USA; Department of Biochemistry and Molecular Biology, Michigan State University, 603 Wilson Road, East Lansing, MI 48824, USA
| | - Markus Sutter
- MSU-DOE Plant Research Laboratory, Michigan State University, 612 Wilson Road, East Lansing, MI 48824, USA; Department of Biochemistry and Molecular Biology, Michigan State University, 603 Wilson Road, East Lansing, MI 48824, USA; Environmental Genomics and Systems Biology and Molecular Biophysics and Integrated Bioimaging Divisions, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, USA
| | - Cheryl A Kerfeld
- MSU-DOE Plant Research Laboratory, Michigan State University, 612 Wilson Road, East Lansing, MI 48824, USA; Department of Biochemistry and Molecular Biology, Michigan State University, 603 Wilson Road, East Lansing, MI 48824, USA; Environmental Genomics and Systems Biology and Molecular Biophysics and Integrated Bioimaging Divisions, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, USA.
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22
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Bio-engineering of bacterial microcompartments: a mini review. Biochem Soc Trans 2019; 47:765-777. [DOI: 10.1042/bst20170564] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2019] [Revised: 05/09/2019] [Accepted: 05/22/2019] [Indexed: 12/30/2022]
Abstract
AbstractBacterial microcompartments (BMCs) are protein-bound prokaryotic organelles, discovered in cyanobacteria more than 60 years ago. Functionally similar to eukaryotic cellular organelles, BMCs compartment metabolic activities in the cytoplasm, foremost to increase local enzyme concentration and prevent toxic intermediates from damaging the cytosolic content. Advanced knowledge of the functional and structural properties of multiple types of BMCs, particularly over the last 10 years, have highlighted design principles of microcompartments. This has prompted new research into their potential to function as programmable synthetic nano-bioreactors and novel bio-materials with biotechnological and medical applications. Moreover, due to the involvement of microcompartments in bacterial pathogenesis and human health, BMCs have begun to gain attention as potential novel drug targets. This mini-review gives an overview of important synthetic biology developments in the bioengineering of BMCs and a perspective on future directions in the field.
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23
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Nichols TM, Kennedy NW, Tullman-Ercek D. Cargo encapsulation in bacterial microcompartments: Methods and analysis. Methods Enzymol 2019; 617:155-186. [PMID: 30784401 PMCID: PMC6590060 DOI: 10.1016/bs.mie.2018.12.009] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Metabolic engineers seek to produce high-value products from inexpensive starting materials in a sustainable and cost-effective manner by using microbes as cellular factories. However, pathway development and optimization can be arduous tasks, complicated by pathway bottlenecks and toxicity. Pathway organization has emerged as a potential solution to these issues, and the use of protein- or DNA-based scaffolds has successfully increased the production of several industrially relevant compounds. These efforts demonstrate the usefulness of pathway colocalization and spatial organization for metabolic engineering applications. In particular, scaffolding within an enclosed, subcellular compartment shows great promise for pathway optimization, offering benefits such as increased local enzyme and substrate concentrations, sequestration of toxic or volatile intermediates, and alleviation of cofactor and resource competition with the host. Here, we describe the 1,2-propanediol utilization (Pdu) bacterial microcompartment (MCP) as an enclosed scaffold for pathway sequestration and organization. We first describe methods for controlling Pdu MCP formation, expressing and encapsulating heterologous cargo, and tuning cargo loading levels. We further describe assays for analyzing Pdu MCPs and assessing encapsulation levels. These methods will enable the repurposing of MCPs as tunable nanobioreactors for heterologous pathway encapsulation.
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Affiliation(s)
- Taylor M Nichols
- Department of Chemical and Biological Engineering, Northwestern University, Technological Institute, Evanston, IL, United States
| | - Nolan W Kennedy
- Interdisciplinary Biological Sciences Graduate Program, Northwestern University, Evanston, IL, United States
| | - Danielle Tullman-Ercek
- Department of Chemical and Biological Engineering, Northwestern University, Technological Institute, Evanston, IL, United States; Center for Synthetic Biology, Northwestern University, Technological Institute, Evanston, IL, United States.
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24
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Liu Y, He X, Lim W, Mueller J, Lawrie J, Kramer L, Guo J, Niu W. Deciphering molecular details in the assembly of alpha-type carboxysome. Sci Rep 2018; 8:15062. [PMID: 30305640 PMCID: PMC6180065 DOI: 10.1038/s41598-018-33074-x] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2018] [Accepted: 09/12/2018] [Indexed: 01/25/2023] Open
Abstract
Bacterial microcompartments (BMCs) are promising natural protein structures for applications that require the segregation of certain metabolic functions or molecular species in a defined microenvironment. To understand how endogenous cargos are packaged inside the protein shell is key for using BMCs as nano-scale reactors or delivery vesicles. In this report, we studied the encapsulation of RuBisCO into the α-type carboxysome from Halothiobacillus neapolitan. Our experimental data revealed that the CsoS2 scaffold proteins engage RuBisCO enzyme through an interaction with the small subunit (CbbS). In addition, the N domain of the large subunit (CbbL) of RuBisCO interacts with all shell proteins that can form the hexamers. The binding affinity between the N domain of CbbL and one of the major shell proteins, CsoS1C, is within the submicromolar range. The absence of the N domain also prevented the encapsulation of the rest of the RuBisCO subunits. Our findings complete the picture of how RuBisCOs are encapsulated into the α-type carboxysome and provide insights for future studies and engineering of carboxysome as a protein shell.
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Affiliation(s)
- Yilan Liu
- Department of Chemical & Biomolecular Engineering, University of Nebraska-Lincoln, Lincoln, Nebraska, 68588, United States
| | - Xinyuan He
- Department of Chemical & Biomolecular Engineering, University of Nebraska-Lincoln, Lincoln, Nebraska, 68588, United States
| | - Weiping Lim
- Department of Chemical & Biomolecular Engineering, University of Nebraska-Lincoln, Lincoln, Nebraska, 68588, United States
| | - Joshua Mueller
- Department of Chemical & Biomolecular Engineering, University of Nebraska-Lincoln, Lincoln, Nebraska, 68588, United States
| | - Justin Lawrie
- Department of Chemistry, University of Nebraska-Lincoln, Lincoln, Nebraska, 68588, United States
| | - Levi Kramer
- Department of Chemical & Biomolecular Engineering, University of Nebraska-Lincoln, Lincoln, Nebraska, 68588, United States
| | - Jiantao Guo
- Department of Chemistry, University of Nebraska-Lincoln, Lincoln, Nebraska, 68588, United States
| | - Wei Niu
- Department of Chemical & Biomolecular Engineering, University of Nebraska-Lincoln, Lincoln, Nebraska, 68588, United States.
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25
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Biotechnological Advances in Bacterial Microcompartment Technology. Trends Biotechnol 2018; 37:325-336. [PMID: 30236905 DOI: 10.1016/j.tibtech.2018.08.006] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2018] [Revised: 08/22/2018] [Accepted: 08/23/2018] [Indexed: 12/22/2022]
Abstract
Bacterial microcompartments (BMCs) represent proteinaceous macromolecular nanobioreactors that are found in a broad range of bacteria, and which are associated with either anabolic or catabolic processes. They consist of a semipermeable outer shell that packages a central metabolic enzyme or pathway, providing both enhanced flux and protection against toxic intermediates. Recombinant production of BMCs has led to their repurposing with the incorporation of altogether new pathways. Deconstructing BMCs into their component parts has shown that some individual shell proteins self-associate into filaments that can be further modified into a cytoplasmic scaffold, or cytoscaffold, to which enzymes/proteins can be targeted. BMCs therefore represent a modular system that is highly suited for engineering biological systems for useful purposes.
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26
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Metcalf KJ, Slininger Lee MF, Jakobson CM, Tullman-Ercek D. An estimate is worth about a thousand experiments: using order-of-magnitude estimates to identify cellular engineering targets. Microb Cell Fact 2018; 17:135. [PMID: 30165868 PMCID: PMC6117934 DOI: 10.1186/s12934-018-0979-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2018] [Accepted: 08/21/2018] [Indexed: 11/10/2022] Open
Abstract
Biotechnological processes use microbes to convert abundant molecules, such as glucose, into high-value products, such as pharmaceuticals, commodity and fine chemicals, and energy. However, from the outset of the development of a new bioprocess, it is difficult to determine the feasibility, expected yields, and targets for engineering. In this review, we describe a methodology that uses rough estimates to assess the feasibility of a process, approximate the expected product titer of a biological system, and identify variables to manipulate in order to achieve the desired performance. This methodology uses estimates from literature and biological intuition, and can be applied in the early stages of a project to help plan future engineering. We highlight recent literature examples, as well as two case studies from our own work, to demonstrate the use and power of rough estimates. Describing and predicting biological function using estimates guides the research and development phase of new bioprocesses and is a useful first step to understand and build a new microbial factory.
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Affiliation(s)
- Kevin James Metcalf
- Department of Chemical and Biomolecular Engineering, University of California, Berkeley, CA, 94720, USA. .,Department of Biomedical Engineering, Northwestern University, Evanston, IL, 60208, USA.
| | - Marilyn F Slininger Lee
- Department of Chemical and Biomolecular Engineering, University of California, Berkeley, CA, 94720, USA.,U.S. Army Edgewood Chemical Biological Center, Gunpowder, MD, 21010, USA
| | - Christopher Matthew Jakobson
- Department of Chemical and Biomolecular Engineering, University of California, Berkeley, CA, 94720, USA.,Department of Chemical and Systems Biology, Stanford University School of Medicine, Stanford, CA, 94305, USA
| | - Danielle Tullman-Ercek
- Department of Chemical and Biological Engineering, Northwestern University, Evanston, IL, 60208, USA
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27
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Lee MJ, Mantell J, Brown IR, Fletcher JM, Verkade P, Pickersgill RW, Woolfson DN, Frank S, Warren MJ. De novo targeting to the cytoplasmic and luminal side of bacterial microcompartments. Nat Commun 2018; 9:3413. [PMID: 30143644 PMCID: PMC6109187 DOI: 10.1038/s41467-018-05922-x] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2018] [Accepted: 07/31/2018] [Indexed: 01/05/2023] Open
Abstract
Bacterial microcompartments, BMCs, are proteinaceous organelles that encase a specific metabolic pathway within a semi-permeable protein shell. Short encapsulation peptides can direct cargo proteins to the lumen of the compartments. However, the fusion of such peptides to non-native proteins does not guarantee encapsulation and often causes aggregation. Here, we report an approach for targeting recombinant proteins to BMCs that utilizes specific de novo coiled-coil protein–protein interactions. Attachment of one coiled-coil module to PduA (a component of the BMC shell) allows targeting of a fluorescent protein fused to a cognate coiled-coil partner. This interaction takes place on the outer surface of the BMC. The redesign of PduA to generate an N-terminus on the luminal side of the BMC results in intact compartments to which proteins can still be targeted via the designed coiled-coil system. This study provides a strategy to display proteins on the surface or within the lumen of the BMCs. Bacterial microcompartments (BMCs) are protein-bound organelles encapsulating segments of metabolic pathways. Here the authors utilize specific de novo coiled-coil protein-protein interactions to display proteins on the outer or inner surface of BMCs.
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Affiliation(s)
- Matthew J Lee
- Industrial Biotechnology Centre, School of Biosciences, University of Kent, Canterbury, CT2 7NJ, UK
| | - Judith Mantell
- School of Biochemistry, University of Bristol, Medical Sciences Building, University Walk, Bristol, BS8 1TD, UK.,Wolfson Bioimaging Facility, Medical Sciences Building, University Walk, Bristol, BS8 1TD, UK
| | - Ian R Brown
- Industrial Biotechnology Centre, School of Biosciences, University of Kent, Canterbury, CT2 7NJ, UK
| | - Jordan M Fletcher
- School of Chemistry, University of Bristol, Cantock's Close, Bristol, BS8 1TS, UK
| | - Paul Verkade
- School of Biochemistry, University of Bristol, Medical Sciences Building, University Walk, Bristol, BS8 1TD, UK.,Wolfson Bioimaging Facility, Medical Sciences Building, University Walk, Bristol, BS8 1TD, UK.,BrisSynBio, Life Sciences Building, Tyndall Avenue, Bristol, BS8 1TQ, UK
| | - Richard W Pickersgill
- School of Biological and Chemical Sciences, Queen Mary University of London, Mile End Road, London, E1 4NS, UK
| | - Derek N Woolfson
- School of Biochemistry, University of Bristol, Medical Sciences Building, University Walk, Bristol, BS8 1TD, UK.,School of Chemistry, University of Bristol, Cantock's Close, Bristol, BS8 1TS, UK.,BrisSynBio, Life Sciences Building, Tyndall Avenue, Bristol, BS8 1TQ, UK
| | - Stefanie Frank
- Department of Biochemical Engineering, University College London, Bernard Katz Building, Gordon Street, London, WC1E 6BT, UK.
| | - Martin J Warren
- Industrial Biotechnology Centre, School of Biosciences, University of Kent, Canterbury, CT2 7NJ, UK.
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Plegaria JS, Kerfeld CA. Engineering nanoreactors using bacterial microcompartment architectures. Curr Opin Biotechnol 2018; 51:1-7. [PMID: 29035760 PMCID: PMC5899066 DOI: 10.1016/j.copbio.2017.09.005] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2017] [Accepted: 09/19/2017] [Indexed: 12/30/2022]
Abstract
Bacterial microcompartments (BMCs) are organelles that encapsulate enzymes involved in CO2 fixation or carbon catabolism in a selectively permeable protein shell. Here, we highlight recent advances in the bioengineering of these protein-based nanoreactors in heterologous systems, including transfer and expression of BMC gene clusters, the production of template empty shells, and the encapsulation of non-native enzymes.
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Affiliation(s)
- Jefferson S Plegaria
- MSU-DOE Plant Research Laboratory, Michigan State University, East Lansing, MI 48824, USA
| | - Cheryl A Kerfeld
- MSU-DOE Plant Research Laboratory, Michigan State University, East Lansing, MI 48824, USA; Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA; Department of Biochemistry & Molecular Biology, Michigan State University, East Lansing, MI 48824, USA; Berkeley Synthetic Biology Institute, Berkeley, CA 94720, USA.
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Jakobson CM, Tullman-Ercek D, Mangan NM. Spatially organizing biochemistry: choosing a strategy to translate synthetic biology to the factory. Sci Rep 2018; 8:8196. [PMID: 29844460 PMCID: PMC5974357 DOI: 10.1038/s41598-018-26399-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2017] [Accepted: 05/09/2018] [Indexed: 12/20/2022] Open
Abstract
Natural biochemical systems are ubiquitously organized both in space and time. Engineering the spatial organization of biochemistry has emerged as a key theme of synthetic biology, with numerous technologies promising improved biosynthetic pathway performance. One strategy, however, may produce disparate results for different biosynthetic pathways. We use a spatially resolved kinetic model to explore this fundamental design choice in systems and synthetic biology. We predict that two example biosynthetic pathways have distinct optimal organization strategies that vary based on pathway-dependent and cell-extrinsic factors. Moreover, we demonstrate that the optimal design varies as a function of kinetic and biophysical properties, as well as culture conditions. Our results suggest that organizing biosynthesis has the potential to substantially improve performance, but that choosing the appropriate strategy is key. The flexible design-space analysis we propose can be adapted to diverse biosynthetic pathways, and lays a foundation to rationally choose organization strategies for biosynthesis.
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Affiliation(s)
- Christopher M Jakobson
- Department of Chemical and Systems Biology, Stanford University School of Medicine, Stanford, CA, 94305, USA
| | - Danielle Tullman-Ercek
- Department of Chemical and Biological Engineering, Northwestern University, Evanston, IL, 60208, USA
| | - Niall M Mangan
- Department of Engineering Science and Applied Mathematics, Northwestern University, Evanston, IL, 60208, USA.
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Abstract
Bacterial microcompartments (BMCs) are self-assembling organelles that consist of an enzymatic core that is encapsulated by a selectively permeable protein shell. The potential to form BMCs is widespread and found across the kingdom Bacteria. BMCs have crucial roles in carbon dioxide fixation in autotrophs and the catabolism of organic substrates in heterotrophs. They contribute to the metabolic versatility of bacteria, providing a competitive advantage in specific environmental niches. Although BMCs were first visualized more than 60 years ago, it is mainly in the past decade that progress has been made in understanding their metabolic diversity and the structural basis of their assembly and function. This progress has not only heightened our understanding of their role in microbial metabolism but is also beginning to enable their use in a variety of applications in synthetic biology. In this Review, we focus on recent insights into the structure, assembly, diversity and function of BMCs.
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Affiliation(s)
- Cheryl A. Kerfeld
- MSU-DOE Plant Research Laboratory, Michigan State University, East Lansing, MI 48824, USA
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824, USA
| | - Clement Aussignargues
- MSU-DOE Plant Research Laboratory, Michigan State University, East Lansing, MI 48824, USA
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824, USA
| | - Jan Zarzycki
- Max-Planck-Institute for Terrestrial Microbiology, D-35043, Marburg, Germany
| | - Fei Cai
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Markus Sutter
- MSU-DOE Plant Research Laboratory, Michigan State University, East Lansing, MI 48824, USA
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824, USA
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31
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Slininger Lee MF, Jakobson CM, Tullman-Ercek D. Evidence for Improved Encapsulated Pathway Behavior in a Bacterial Microcompartment through Shell Protein Engineering. ACS Synth Biol 2017; 6:1880-1891. [PMID: 28585808 DOI: 10.1021/acssynbio.7b00042] [Citation(s) in RCA: 64] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Bacterial microcompartments are a class of proteinaceous organelles comprising a characteristic protein shell enclosing a set of enzymes. Compartmentalization can prevent escape of volatile or toxic intermediates, prevent off-pathway reactions, and create private cofactor pools. Encapsulation in synthetic microcompartment organelles will enhance the function of heterologous pathways, but to do so, it is critical to understand how to control diffusion in and out of the microcompartment organelle. To this end, we explored how small differences in the shell protein structure result in changes in the diffusion of metabolites through the shell. We found that the ethanolamine utilization (Eut) protein EutM properly incorporates into the 1,2-propanediol utilization (Pdu) microcompartment, altering native metabolite accumulation and the resulting growth on 1,2-propanediol as the sole carbon source. Further, we identified a single pore-lining residue mutation that confers the same phenotype as substitution of the full EutM protein, indicating that small molecule diffusion through the shell is the cause of growth enhancement. Finally, we show that the hydropathy index and charge of pore amino acids are important indicators to predict how pore mutations will affect growth on 1,2-propanediol, likely by controlling diffusion of one or more metabolites. This study highlights the use of two strategies to engineer microcompartments to control metabolite transport: altering the existing shell protein pore via mutation of the pore-lining residues, and generating chimeras using shell proteins with the desired pores.
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Affiliation(s)
- Marilyn F. Slininger Lee
- Department
of Chemical and Biomolecular Engineering, University of California, Berkeley, California 94720, United States
| | - Christopher M. Jakobson
- Department
of Chemical and Biomolecular Engineering, University of California, Berkeley, California 94720, United States
- Department
of Chemical and Systems Biology, Stanford University, Stanford, California, 94305, United States
| | - Danielle Tullman-Ercek
- Department
of Chemical and Biological Engineering, Northwestern University, 2145 Sheridan Road, Technological Institute E136, Evanston, Illinois 60208-3120, United States
- Chemistry
of Life Processes Institute, Northwestern University, 2170 Campus
Drive, Evanston, Illinois 60208-3120, United States
- Center
for Synthetic Biology, Northwestern University, 2145 Sheridan Road, Technological Institute B486, Evanston, Illinois 60208-3120, United States
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32
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Slininger Lee M, Tullman-Ercek D. Practical considerations for the encapsulation of multi-enzyme cargos within the bacterial microcompartment for metabolic engineering. ACTA ACUST UNITED AC 2017. [DOI: 10.1016/j.coisb.2017.05.017] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
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33
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Young EJ, Burton R, Mahalik JP, Sumpter BG, Fuentes-Cabrera M, Kerfeld CA, Ducat DC. Engineering the Bacterial Microcompartment Domain for Molecular Scaffolding Applications. Front Microbiol 2017; 8:1441. [PMID: 28824573 PMCID: PMC5534457 DOI: 10.3389/fmicb.2017.01441] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2017] [Accepted: 07/17/2017] [Indexed: 01/03/2023] Open
Abstract
As synthetic biology advances the intricacy of engineered biological systems, the importance of spatial organization within the cellular environment must not be marginalized. Increasingly, biological engineers are investigating means to control spatial organization within the cell, mimicking strategies used by natural pathways to increase flux and reduce cross-talk. A modular platform for constructing a diverse set of defined, programmable architectures would greatly assist in improving yields from introduced metabolic pathways and increasing insulation of other heterologous systems. Here, we review recent research on the shell proteins of bacterial microcompartments and discuss their potential application as "building blocks" for a range of customized intracellular scaffolds. We summarize the state of knowledge on the self-assembly of BMC shell proteins and discuss future avenues of research that will be important to realize the potential of BMC shell proteins as predictively assembling and programmable biological materials for bioengineering.
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Affiliation(s)
- Eric J. Young
- Biochemistry and Molecular Biology, Michigan State University, East LansingMI, United States
- MSU-DOE Plant Research Laboratory, East LansingMI, United States
| | - Rodney Burton
- MSU-DOE Plant Research Laboratory, East LansingMI, United States
| | - Jyoti P. Mahalik
- Computational Sciences and Engineering, Oak Ridge National Laboratory, Oak RidgeTN, United States
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak RidgeTN, United States
| | - Bobby G. Sumpter
- Computational Sciences and Engineering, Oak Ridge National Laboratory, Oak RidgeTN, United States
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak RidgeTN, United States
| | - Miguel Fuentes-Cabrera
- Computational Sciences and Engineering, Oak Ridge National Laboratory, Oak RidgeTN, United States
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak RidgeTN, United States
| | - Cheryl A. Kerfeld
- Biochemistry and Molecular Biology, Michigan State University, East LansingMI, United States
- MSU-DOE Plant Research Laboratory, East LansingMI, United States
- Molecular Biophysics and Integrated Bioimaging Division, Berkeley National Laboratory, BerkeleyCA, United States
| | - Daniel C. Ducat
- Biochemistry and Molecular Biology, Michigan State University, East LansingMI, United States
- MSU-DOE Plant Research Laboratory, East LansingMI, United States
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34
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Azuma Y, Zschoche R, Hilvert D. The C-terminal peptide of Aquifex aeolicus riboflavin synthase directs encapsulation of native and foreign guests by a cage-forming lumazine synthase. J Biol Chem 2017; 292:10321-10327. [PMID: 28515315 PMCID: PMC5481547 DOI: 10.1074/jbc.c117.790311] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2017] [Revised: 05/12/2017] [Indexed: 12/31/2022] Open
Abstract
Encapsulation of specific enzymes in self-assembling protein cages is a hallmark of bacterial compartments that function as counterparts to eukaryotic organelles. The cage-forming enzyme lumazine synthase (LS) from Bacillus subtilis (BsLS), for example, encapsulates riboflavin synthase (BsRS), enabling channeling of lumazine from the site of its generation to the site of its conversion to vitamin B2 Elucidating the molecular mechanisms underlying the assembly of these supramolecular complexes could help inform new approaches for metabolic engineering, nanotechnology, and drug delivery. To that end, we investigated a thermostable LS from Aquifex aeolicus (AaLS) and found that it also forms cage complexes with the cognate riboflavin synthase (AaRS) when both proteins are co-produced in the cytosol of Escherichia coli A 12-amino acid-long peptide at the C terminus of AaRS serves as a specific localization sequence responsible for targeting the guest to the protein compartment. Sequence comparisons suggested that analogous peptide segments likely direct RS complexation by LS cages in other bacterial species. Covalent fusion of this peptide tag to heterologous guest molecules led to their internalization into AaLS assemblies both in vivo and in vitro, providing a firm foundation for creating tailored biomimetic nanocompartments for medical and biotechnological applications.
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Affiliation(s)
- Yusuke Azuma
- From the Laboratory of Organic Chemistry, ETH Zurich, 8093 Zürich, Switzerland
| | - Reinhard Zschoche
- From the Laboratory of Organic Chemistry, ETH Zurich, 8093 Zürich, Switzerland
| | - Donald Hilvert
- From the Laboratory of Organic Chemistry, ETH Zurich, 8093 Zürich, Switzerland
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35
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Jakobson CM, Slininger Lee MF, Tullman‐Ercek D. De novo design of signal sequences to localize cargo to the 1,2-propanediol utilization microcompartment. Protein Sci 2017; 26:1086-1092. [PMID: 28241402 PMCID: PMC5405430 DOI: 10.1002/pro.3144] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2016] [Revised: 02/16/2017] [Accepted: 02/17/2017] [Indexed: 12/24/2022]
Abstract
Organizing heterologous biosyntheses inside bacterial cells can alleviate common problems owing to toxicity, poor kinetic performance, and cofactor imbalances. A subcellular organelle known as a bacterial microcompartment, such as the 1,2-propanediol utilization microcompartment of Salmonella, is a promising chassis for this strategy. Here we demonstrate de novo design of the N-terminal signal sequences used to direct cargo to these microcompartment organelles. We expand the native repertoire of signal sequences using rational and library-based approaches and show that a canonical leucine-zipper motif can function as a signal sequence for microcompartment localization. Our strategy can be applied to generate new signal sequences localizing arbitrary cargo proteins to the 1,2-propanediol utilization microcompartments.
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Affiliation(s)
- Christopher M. Jakobson
- Department of Chemical and Biological EngineeringNorthwestern UniversityEvanstonIllinois60208
- Present address: Department of Chemical and Systems BiologyStanford UniversityStanfordCA94305
| | - Marilyn F. Slininger Lee
- Department of Chemical and Biological EngineeringNorthwestern UniversityEvanstonIllinois60208
- Department of Chemical and Biomolecular EngineeringUniversity of California BerkeleyBerkeleyCalifornia94720
| | - Danielle Tullman‐Ercek
- Department of Chemical and Biological EngineeringNorthwestern UniversityEvanstonIllinois60208
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36
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Yung MC, Bourguet FA, Carpenter TS, Coleman MA. Re-directing bacterial microcompartment systems to enhance recombinant expression of lysis protein E from bacteriophage ϕX174 in Escherichia coli. Microb Cell Fact 2017; 16:71. [PMID: 28446197 PMCID: PMC5405515 DOI: 10.1186/s12934-017-0685-x] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2017] [Accepted: 04/21/2017] [Indexed: 02/06/2023] Open
Abstract
Background Recombinant expression of toxic proteins remains a challenging problem. One potential method to shield toxicity and thus improve expression of these proteins is to encapsulate them within protein compartments to sequester them away from their targets. Many bacteria naturally produce so-called bacterial microcompartments (BMCs) in which enzymes comprising a biosynthetic pathway are encapsulated in a proteinaeous shell, which is in part thought to shield the cells from the toxicity of reaction intermediates. As a proof-of-concept, we attempted to encapsulate toxic, lysis protein E (E) from bacteriophage ϕX174 inside recombinant BMCs to enhance its expression and achieve higher yields during downstream purification. Results E was fused with various N-terminal BMC targeting tags (PduP-, PduD-, and EutC-tags, 18–20 amino acids) and co-expressed with appropriate BMC shell proteins that associate with the tags and are required to form BMCs. Only BMC targeted E fusions, but not non-tagged E, could be successfully cloned, suggesting that the BMC tags reduce the toxicity of E. A PduP-tagged E system appeared to achieve the highest expression of E. Co-expression of Pdu BMC shell proteins with PduP-E increased its expression by 20–50%. Affinity purification of PduP-E via Ni–NTA in the presence of Empigen BB detergent yielded 270 µg of PduP-E per L of induced culture. Removal of the PduP-tag via proteolysis resulted in a final yield of 200 µg of E per L of induced culture, a nearly order of magnitude (~sevenfold) improvement compared to prior reports. Conclusions These results demonstrate improved expression of ϕX174 lysis protein E via re-directed BMC systems and ultimately higher E purification yields. Similar strategies can be used to enhance expression of other toxic proteins in recombinant Escherichia coli systems. Electronic supplementary material The online version of this article (doi:10.1186/s12934-017-0685-x) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Mimi C Yung
- Biosciences and Biotechnology Division, Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, 7000 East Avenue, L-452, Livermore, CA, 94550, USA.
| | - Feliza A Bourguet
- Biosciences and Biotechnology Division, Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, 7000 East Avenue, L-452, Livermore, CA, 94550, USA
| | - Timothy S Carpenter
- Biosciences and Biotechnology Division, Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, 7000 East Avenue, L-452, Livermore, CA, 94550, USA
| | - Matthew A Coleman
- Biosciences and Biotechnology Division, Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, 7000 East Avenue, L-452, Livermore, CA, 94550, USA
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37
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The N Terminus of the PduB Protein Binds the Protein Shell of the Pdu Microcompartment to Its Enzymatic Core. J Bacteriol 2017; 199:JB.00785-16. [PMID: 28138097 DOI: 10.1128/jb.00785-16] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2016] [Accepted: 01/20/2017] [Indexed: 12/12/2022] Open
Abstract
Bacterial microcompartments (MCPs) are extremely large proteinaceous organelles that consist of an enzymatic core encapsulated within a complex protein shell. A key question in MCP biology is the nature of the interactions that guide the assembly of thousands of protein subunits into a well-ordered metabolic compartment. In this report, we show that the N-terminal 37 amino acids of the PduB protein have a critical role in binding the shell of the 1,2-propanediol utilization (Pdu) microcompartment to its enzymatic core. Several mutations were constructed that deleted short regions of the N terminus of PduB. Growth tests indicated that three of these deletions were impaired MCP assembly. Attempts to purify MCPs from these mutants, followed by gel electrophoresis and enzyme assays, indicated that the protein complexes isolated consisted of MCP shells depleted of core enzymes. Electron microscopy substantiated these findings by identifying apparently empty MCP shells but not intact MCPs. Analyses of 13 site-directed mutants indicated that the key region of the N terminus of PduB required for MCP assembly is a putative helix spanning residues 6 to 18. Considering the findings presented here together with prior work, we propose a new model for MCP assembly.IMPORTANCE Bacterial microcompartments consist of metabolic enzymes encapsulated within a protein shell and are widely used to optimize metabolic process. Here, we show that the N-terminal 37 amino acids of the PduB shell protein are essential for assembly of the 1,2-propanediol utilization microcompartment. The results indicate that it plays a key role in binding the outer shell to the enzymatic core. We propose that this interaction might be used to define the relative orientation of the shell with respect to the core. This finding is of fundamental importance to our understanding of microcompartment assembly and may have application to engineering microcompartments as nanobioreactors for chemical production.
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38
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Lee SQE, Tan TS, Kawamukai M, Chen ES. Cellular factories for coenzyme Q 10 production. Microb Cell Fact 2017; 16:39. [PMID: 28253886 PMCID: PMC5335738 DOI: 10.1186/s12934-017-0646-4] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2016] [Accepted: 02/10/2017] [Indexed: 04/20/2023] Open
Abstract
Coenzyme Q10 (CoQ10), a benzoquinone present in most organisms, plays an important role in the electron-transport chain, and its deficiency is associated with various neuropathies and muscular disorders. CoQ10 is the only lipid-soluble antioxidant found in humans, and for this, it is gaining popularity in the cosmetic and healthcare industries. To meet the growing demand for CoQ10, there has been considerable interest in ways to enhance its production, the most effective of which remains microbial fermentation. Previous attempts to increase CoQ10 production to an industrial scale have thus far conformed to the strategies used in typical metabolic engineering endeavors. However, the emergence of new tools in the expanding field of synthetic biology has provided a suite of possibilities that extend beyond the traditional modes of metabolic engineering. In this review, we cover the various strategies currently undertaken to upscale CoQ10 production, and discuss some of the potential novel areas for future research.
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Affiliation(s)
- Sean Qiu En Lee
- Department of Biochemistry, National University of Singapore, Singapore, Singapore
| | - Tsu Soo Tan
- School of Chemical & Life Sciences, Nanyang Polytechnic, Singapore, Singapore
| | - Makoto Kawamukai
- Faculty of Life and Environmental Science, Shimane University, Matsue, 690-8504, Japan
| | - Ee Sin Chen
- Department of Biochemistry, National University of Singapore, Singapore, Singapore. .,National University Health System (NUHS), Singapore, Singapore. .,NUS Synthetic Biology for Clinical and Technological Innovation (SynCTI), Life Sciences Institute, National University of Singapore, Singapore, Singapore. .,NUS Graduate School for Integrative Sciences and Engineering, National University of Singapore, Singapore, Singapore.
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39
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Wagner HJ, Capitain CC, Richter K, Nessling M, Mampel J. Engineering bacterial microcompartments with heterologous enzyme cargos. Eng Life Sci 2016; 17:36-46. [PMID: 32624727 DOI: 10.1002/elsc.201600107] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2016] [Revised: 06/16/2016] [Accepted: 07/12/2016] [Indexed: 01/01/2023] Open
Abstract
Bacterial microcompartments (BMCs) are intracellular proteinaceous organelles devoid of a lipid membrane that encapsulates enzymes of metabolic pathways. Salmonella enterica synthesizes propanediol-utilization BMCs containing enzymes involved in the degradation of 1,2-propanediol. BMCs can be designed to enclose heterologous proteins, paving the way to engineered catalytic microreactors. Here, we investigate broader applicability of this design principle by directing three different enzymes to the BMC. We demonstrate that β-galactosidase, esterase Est5, and cofactor-dependent glycerol dehydrogenase can be directed to the BMC and copurified with the microcompartment shell in a catalytically active form. We show that the BMC shell protects enzymes from pH-dependent but not from temperature stress. Moreover, we provide evidence that the heterologously expressed BMCs act as a moderately selective diffusion barrier for lipophilic small molecules.
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Affiliation(s)
- Hanna J Wagner
- BRAIN AG (Biotechnology Research and Information Network) Zwingenberg Germany.,Faculty of Biology and Spemann Graduate School of Biology and Medicine (SGBM) University of Freiburg Freiburg Germany
| | - Charlotte C Capitain
- BRAIN AG (Biotechnology Research and Information Network) Zwingenberg Germany.,Department of Biotechnology Mannheim University of Applied Sciences Mannheim Germany
| | - Karsten Richter
- German Cancer Research Centre (DKFZ) Core Facility Electron Microscopy (W230) Heidelberg Germany
| | - Michelle Nessling
- German Cancer Research Centre (DKFZ) Core Facility Electron Microscopy (W230) Heidelberg Germany
| | - Jörg Mampel
- BRAIN AG (Biotechnology Research and Information Network) Zwingenberg Germany
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40
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Encapsulation of multiple cargo proteins within recombinant Eut nanocompartments. Appl Microbiol Biotechnol 2016; 100:9187-9200. [PMID: 27450681 DOI: 10.1007/s00253-016-7737-8] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2016] [Revised: 07/07/2016] [Accepted: 07/10/2016] [Indexed: 01/08/2023]
Abstract
Spatial organization via encapsulation of enzymes within recombinant nanocompartments may increase efficiency in multienzyme cascades. Previously, we reported the encapsulation of single cargo proteins within nanocompartments in the heterologous host Escherichia coli. This was achieved by coexpression of the Salmonella enterica LT2 ethanolamine utilization bacterial microcompartment shell proteins EutS or EutSMNLK, with a signal sequence EutC1-19 cargo protein fusion. Optimization of this system, leading to the targeting of more than one cargo protein, requires an understanding of the encapsulation mechanism. In this work, we report that the signal sequence EutC1-19 targets cargo to the interior of nanocompartments via a hydrophobic interaction with a helix on shell protein EutS. We confirm that EutC1-19 does not interact with other Eut BMC shell proteins, EutMNLK. Furthermore, we show that a second signal sequence EutE1-21 interacts specifically with the same helix on EutS. Both signal sequences appear to compete for the same EutS helix to simultaneously colocalize two cargo proteins to the interior of recombinant nanocompartments. This work offers the first insights into signal sequence-shell protein interactions required for cargo sequestration within Eut BMCs. It also provides a basis for the future engineering of Eut nanocompartments as a platform for the potential colocalization of multienzyme cascades for synthetic biology applications.
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41
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Jakobson CM, Chen Y, Slininger MF, Valdivia E, Kim EY, Tullman-Ercek D. Tuning the Catalytic Activity of Subcellular Nanoreactors. J Mol Biol 2016; 428:2989-96. [PMID: 27427532 DOI: 10.1016/j.jmb.2016.07.006] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2016] [Revised: 06/29/2016] [Accepted: 07/06/2016] [Indexed: 11/25/2022]
Abstract
Bacterial microcompartments are naturally occurring subcellular organelles of bacteria and serve as a promising scaffold for the organization of heterologous biosynthetic pathways. A critical element in the design of custom biosynthetic organelles is quantitative control over the loading of heterologous enzymes to the interior of the organelles. We demonstrate that the loading of heterologous proteins to the 1,2-propanediol utilization microcompartment of Salmonella enterica can be controlled using two strategies: by modulating the transcriptional activation of the microcompartment container and by coordinating the expression of the microcompartment container and the heterologous cargo. These strategies allow general control over the loading of heterologous proteins localized by two different N-terminal targeting peptides and represent an important step toward tuning the catalytic activity of bacterial microcompartments for increased biosynthetic productivity.
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Affiliation(s)
- Christopher M Jakobson
- Department of Chemical and Biomolecular Engineering, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Yiqun Chen
- Department of Chemistry, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Marilyn F Slininger
- Department of Chemical and Biomolecular Engineering, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Elias Valdivia
- Department of Plant and Microbial Biology, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Edward Y Kim
- Department of Chemical and Biomolecular Engineering, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Danielle Tullman-Ercek
- Department of Chemical and Biological Engineering, Northwestern University, Evanston, IL, USA.
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42
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Gonzalez-Esquer CR, Newnham SE, Kerfeld CA. Bacterial microcompartments as metabolic modules for plant synthetic biology. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2016; 87:66-75. [PMID: 26991644 DOI: 10.1111/tpj.13166] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/21/2016] [Revised: 03/04/2016] [Accepted: 03/08/2016] [Indexed: 05/28/2023]
Abstract
Bacterial microcompartments (BMCs) are megadalton-sized protein assemblies that enclose segments of metabolic pathways within cells. They increase the catalytic efficiency of the encapsulated enzymes while sequestering volatile or toxic intermediates from the bulk cytosol. The first BMCs discovered were the carboxysomes of cyanobacteria. Carboxysomes compartmentalize the enzyme ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) with carbonic anhydrase. They enhance the carboxylase activity of RuBisCO by increasing the local concentration of CO2 in the vicinity of the enzyme's active site. As a metabolic module for carbon fixation, carboxysomes could be transferred to eukaryotic organisms (e.g. plants) to increase photosynthetic efficiency. Within the scope of synthetic biology, carboxysomes and other BMCs hold even greater potential when considered a source of building blocks for the development of nanoreactors or three-dimensional scaffolds to increase the efficiency of either native or heterologously expressed enzymes. The carboxysome serves as an ideal model system for testing approaches to engineering BMCs because their expression in cyanobacteria provides a sensitive screen for form (appearance of polyhedral bodies) and function (ability to grow on air). We recount recent progress in the re-engineering of the carboxysome shell and core to offer a conceptual framework for the development of BMC-based architectures for applications in plant synthetic biology.
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Affiliation(s)
| | - Sarah E Newnham
- MSU-DOE Plant Research Laboratory, Michigan State University, East Lansing, MI, USA
| | - Cheryl A Kerfeld
- MSU-DOE Plant Research Laboratory, Michigan State University, East Lansing, MI, USA
- Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI, USA
- Berkeley Synthetic Biology Institute, UC Berkeley, Berkeley, CA, USA
- Department of Plant and Microbial Biology, UC Berkeley, Berkeley, CA, USA
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Held M, Kolb A, Perdue S, Hsu SY, Bloch SE, Quin MB, Schmidt-Dannert C. Engineering formation of multiple recombinant Eut protein nanocompartments in E. coli. Sci Rep 2016; 6:24359. [PMID: 27063436 PMCID: PMC4827028 DOI: 10.1038/srep24359] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2015] [Accepted: 03/29/2016] [Indexed: 01/17/2023] Open
Abstract
Compartmentalization of designed metabolic pathways within protein based nanocompartments has the potential to increase reaction efficiency in multi-step biosynthetic reactions. We previously demonstrated proof-of-concept of this aim by targeting a functional enzyme to single cellular protein nanocompartments, which were formed upon recombinant expression of the Salmonella enterica LT2 ethanolamine utilization bacterial microcompartment shell proteins EutS or EutSMNLK in Escherichia coli. To optimize this system, increasing overall encapsulated enzyme reaction efficiency, factor(s) required for the production of more than one nanocompartment per cell must be identified. In this work we report that the cupin domain protein EutQ is required for assembly of more than one nanocompartment per cell. Overexpression of EutQ results in multiple nanocompartment assembly in our recombinant system. EutQ specifically interacts with the shell protein EutM in vitro via electrostatic interactions with the putative cytosolic face of EutM. These findings lead to the theory that EutQ could facilitate multiple nanocompartment biogenesis by serving as an assembly hub for shell proteins. This work offers insights into the biogenesis of Eut bacterial microcompartments, and also provides an improved platform for the production of protein based nanocompartments for targeted encapsulation of enzyme pathways.
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Affiliation(s)
- Mark Held
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, St. Paul, MN 55108, USA
| | - Alexander Kolb
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, St. Paul, MN 55108, USA
| | - Sarah Perdue
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, St. Paul, MN 55108, USA
| | - Szu-Yi Hsu
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, St. Paul, MN 55108, USA
| | - Sarah E Bloch
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, St. Paul, MN 55108, USA
| | - Maureen B Quin
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, St. Paul, MN 55108, USA
| | - Claudia Schmidt-Dannert
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, St. Paul, MN 55108, USA
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Cai F, Bernstein SL, Wilson SC, Kerfeld CA. Production and Characterization of Synthetic Carboxysome Shells with Incorporated Luminal Proteins. PLANT PHYSIOLOGY 2016; 170:1868-77. [PMID: 26792123 PMCID: PMC4775138 DOI: 10.1104/pp.15.01822] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Received: 11/20/2015] [Accepted: 01/16/2016] [Indexed: 05/19/2023]
Abstract
Spatial segregation of metabolism, such as cellular-localized CO2 fixation in C4 plants or in the cyanobacterial carboxysome, enhances the activity of inefficient enzymes by selectively concentrating them with their substrates. The carboxysome and other bacterial microcompartments (BMCs) have drawn particular attention for bioengineering of nanoreactors because they are self-assembling proteinaceous organelles. All BMCs share an architecturally similar, selectively permeable shell that encapsulates enzymes. Fundamental to engineering carboxysomes and other BMCs for applications in plant synthetic biology and metabolic engineering is understanding the structural determinants of cargo packaging and shell permeability. Here we describe the expression of a synthetic operon in Escherichia coli that produces carboxysome shells. Protein domains native to the carboxysome core were used to encapsulate foreign cargo into the synthetic shells. These synthetic shells can be purified to homogeneity with or without luminal proteins. Our results not only further the understanding of protein-protein interactions governing carboxysome assembly, but also establish a platform to study shell permeability and the structural basis of the function of intact BMC shells both in vivo and in vitro. This system will be especially useful for developing synthetic carboxysomes for plant engineering.
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Affiliation(s)
- Fei Cai
- Department of Plant and Microbial Biology, University of California, Berkeley, California 94720 (F.C., S.L.B., S.C.W., C.A.K.); Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (F.C., S.L.B., S.C.W., C.A.K.); and MSU-DOE Plant Research Laboratory and Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan 48824 (C.A.K.)
| | - Susan L Bernstein
- Department of Plant and Microbial Biology, University of California, Berkeley, California 94720 (F.C., S.L.B., S.C.W., C.A.K.); Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (F.C., S.L.B., S.C.W., C.A.K.); and MSU-DOE Plant Research Laboratory and Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan 48824 (C.A.K.)
| | - Steven C Wilson
- Department of Plant and Microbial Biology, University of California, Berkeley, California 94720 (F.C., S.L.B., S.C.W., C.A.K.); Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (F.C., S.L.B., S.C.W., C.A.K.); and MSU-DOE Plant Research Laboratory and Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan 48824 (C.A.K.)
| | - Cheryl A Kerfeld
- Department of Plant and Microbial Biology, University of California, Berkeley, California 94720 (F.C., S.L.B., S.C.W., C.A.K.); Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (F.C., S.L.B., S.C.W., C.A.K.); and MSU-DOE Plant Research Laboratory and Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan 48824 (C.A.K.)
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