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Garcia DC, Cheng X, Land ML, Standaert RF, Morrell-Falvey JL, Doktycz MJ. Computationally Guided Discovery and Experimental Validation of Indole-3-acetic Acid Synthesis Pathways. ACS Chem Biol 2019; 14:2867-2875. [PMID: 31693336 DOI: 10.1021/acschembio.9b00725] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Elucidating the interaction networks associated with secondary metabolite production in microorganisms is an ongoing challenge made all the more daunting by the rate at which DNA sequencing technology reveals new genes and potential pathways. Developing the culturing methods, expression conditions, and genetic systems needed for validating pathways in newly discovered microorganisms is often not possible. Therefore, new tools and techniques are needed for defining complex metabolic pathways. Here, we describe an in vitro computationally assisted pathway description approach that employs bioinformatic searches of genome databases, protein structural modeling, and protein-ligand-docking simulations to predict the gene products most likely to be involved in a particular secondary metabolite production pathway. This information is then used to direct in vitro reconstructions of the pathway and subsequent confirmation of pathway activity using crude enzyme preparations. As a test system, we elucidated the pathway for biosynthesis of indole-3-acetic acid (IAA) in the plant-associated microbe Pantoea sp. YR343. This organism is capable of metabolizing tryptophan into the plant phytohormone IAA. BLAST analyses identified a likely three-step pathway involving an amino transferase, an indole pyruvate decarboxylase, and a dehydrogenase. However, multiple candidate enzymes were identified at each step, resulting in a large number of potential pathway reconstructions (32 different enzyme combinations). Our approach shows the effectiveness of crude extracts to rapidly elucidate enzymes leading to functional pathways. Results are compared to affinity purified enzymes for select combinations and found to yield similar relative activities. Further, in vitro testing of the pathway reconstructions revealed the "underground" nature of IAA metabolism in Pantoea sp. YR343 and the various mechanisms used to produce IAA. Importantly, our experiments illustrate the scalable integration of computational tools and cell-free enzymatic reactions to identify and validate metabolic pathways in a broadly applicable manner.
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Affiliation(s)
- David C. Garcia
- Biological and Nanoscale Systems Group, Biosciences Division Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
- Bredesen Center for Interdisciplinary Research and Graduate Education, University of Tennessee, Knoxville, Tennessee 37996-4519, United States
| | - Xiaolin Cheng
- College of Pharmacy, The Ohio State University, Columbus, Ohio 43210, United States
| | - Miriam L. Land
- Computational Biology and Bioinformatics Group, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Robert F. Standaert
- Biological and Nanoscale Systems Group, Biosciences Division Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
- Department of Chemistry, East Tennessee State University, Johnson City, Tennessee 37604, United States
| | - Jennifer L. Morrell-Falvey
- Biological and Nanoscale Systems Group, Biosciences Division Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
| | - Mitchel J. Doktycz
- Biological and Nanoscale Systems Group, Biosciences Division Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
- Bredesen Center for Interdisciplinary Research and Graduate Education, University of Tennessee, Knoxville, Tennessee 37996-4519, United States
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Estrada P, Morita M, Hao Y, Schmidt EW, Nair SK. A Single Amino Acid Switch Alters the Isoprene Donor Specificity in Ribosomally Synthesized and Post-Translationally Modified Peptide Prenyltransferases. J Am Chem Soc 2018; 140:8124-8127. [PMID: 29924593 DOI: 10.1021/jacs.8b05187] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Mutation at a single amino acid alters the isoprene donor specificity of prenyltransferases involved in the modification of ribosomally synthesized and post-translationally modified peptides (RiPPs). Though most characterized RiPP prenyltransferases carry out the regiospecific transfer of C5 dimethylallyl donor to the side chain atoms on macrocyclic acceptor substrates, the elucidation of the cyanobactin natural product piricyclamide 70005E1 identifies an O-geranyl modification on Tyr, a reaction with little prior biochemical precedence. Reconstitution and kinetic studies of the presumptive geranyltransferase PirF shows that the enzyme utilizes a C10 donor, with no C5 transferase activity. The crystal structure of PirF reveals a single amino acid difference in the vicinity of the isoprene-binding pocket, relative to the C5 utilizing enzymes. Remarkably, only a single amino acid mutation is necessary to completely switch the donor specificity from a C5 to a C10 prenyltransferase, and vice versa. Lastly, we demonstrate that these enzymes may be used for the chemospecific attachment of C5 or C10 lipid groups on lanthipeptides, an unrelated class of RiPP natural products. These studies represent a rare example where prenyl donor specificity can be discretely altered, which expands the arsenal of synthetic biology tools for tuning biological activities of peptide natural products.
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Affiliation(s)
| | - Maho Morita
- Department of Medicinal Chemistry , University of Utah , Salt Lake City , Utah 84112 , United States
| | | | - Eric W Schmidt
- Department of Medicinal Chemistry , University of Utah , Salt Lake City , Utah 84112 , United States
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Liu X, Ding W, Jiang H. Engineering microbial cell factories for the production of plant natural products: from design principles to industrial-scale production. Microb Cell Fact 2017; 16:125. [PMID: 28724386 PMCID: PMC5518134 DOI: 10.1186/s12934-017-0732-7] [Citation(s) in RCA: 65] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2017] [Accepted: 07/05/2017] [Indexed: 11/13/2022] Open
Abstract
Plant natural products (PNPs) are widely used as pharmaceuticals, nutraceuticals, seasonings, pigments, etc., with a huge commercial value on the global market. However, most of these PNPs are still being extracted from plants. A resource-conserving and environment-friendly synthesis route for PNPs that utilizes microbial cell factories has attracted increasing attention since the 1940s. However, at the present only a handful of PNPs are being produced by microbial cell factories at an industrial scale, and there are still many challenges in their large-scale application. One of the challenges is that most biosynthetic pathways of PNPs are still unknown, which largely limits the number of candidate PNPs for heterologous microbial production. Another challenge is that the metabolic fluxes toward the target products in microbial hosts are often hindered by poor precursor supply, low catalytic activity of enzymes and obstructed product transport. Consequently, despite intensive studies on the metabolic engineering of microbial hosts, the fermentation costs of most heterologously produced PNPs are still too high for industrial-scale production. In this paper, we review several aspects of PNP production in microbial cell factories, including important design principles and recent progress in pathway mining and metabolic engineering. In addition, implemented cases of industrial-scale production of PNPs in microbial cell factories are also highlighted.
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Affiliation(s)
- Xiaonan Liu
- Key Laboratory of Systems Microbial Biotechnology, Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, China.,University of Chinese Academy of Sciences, Beijing, China
| | - Wentao Ding
- Key Laboratory of Systems Microbial Biotechnology, Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, China
| | - Huifeng Jiang
- Key Laboratory of Systems Microbial Biotechnology, Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, China.
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In vitro reconstitution guide for targeted synthetic metabolism of chemicals, nutraceuticals and drug precursors. Synth Syst Biotechnol 2016; 1:25-33. [PMID: 29062924 PMCID: PMC5640587 DOI: 10.1016/j.synbio.2016.02.003] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2015] [Revised: 01/27/2016] [Accepted: 02/12/2016] [Indexed: 11/24/2022] Open
Abstract
With the developments in metabolic engineering and the emergence of synthetic biology, many breakthroughs in medicinal, biological and chemical products as well as biofuels have been achieved in recent decades. As an important barrier to traditional metabolic engineering, however, the identification of rate-limiting step(s) for the improvement of specific cellular functions is often difficult. Meanwhile, in the case of synthetic biology, more and more BioBricks could be constructed for targeted purposes, but the optimized assembly or engineering of these components for high-efficiency cell factories is still a challenge. Owing to the lack of steady-state kinetic data for overall flux, balancing many multistep biosynthetic pathways is time-consuming and needs vast resources of labor and materials. A strategy called targeted engineering is proposed in an effort to solve this problem. Briefly, a targeted biosynthetic pathway is to be reconstituted in vitro and then the contribution of cofactors, substrates and each enzyme will be analyzed systematically. Next is in vivo engineering or de novo pathway assembly with the guidance of information gained from in vitro assays. To demonstrate its practical application, biosynthesis pathways for the production of important products, e.g. chemicals, nutraceuticals and drug precursors, have been engineered in Escherichia coli and Saccharomyces cerevisiae. These cases can be regarded as concept proofs indicating targeted engineering might help to create high-efficiency cell factories based upon constructed biological components.
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