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Campbell RP, Whittington AC, Zorio DAR, Miller BG. Recruitment of a Middling Promiscuous Enzyme Drives Adaptive Metabolic Evolution in Escherichia coli. Mol Biol Evol 2023; 40:msad202. [PMID: 37708398 PMCID: PMC10519446 DOI: 10.1093/molbev/msad202] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2023] [Revised: 08/29/2023] [Accepted: 09/05/2023] [Indexed: 09/16/2023] Open
Abstract
A key step in metabolic pathway evolution is the recruitment of promiscuous enzymes to perform new functions. Despite the recognition that promiscuity is widespread in biology, factors dictating the preferential recruitment of one promiscuous enzyme over other candidates are unknown. Escherichia coli contains four sugar kinases that are candidates for recruitment when the native glucokinase machinery is deleted-allokinase (AlsK), manno(fructo)kinase (Mak), N-acetylmannosamine kinase (NanK), and N-acetylglucosamine kinase (NagK). The catalytic efficiencies of these enzymes are 103- to 105-fold lower than native glucokinases, ranging from 2,400 M-1 s-1 for the most active candidate, NagK, to 15 M-1 s-1 for the least active candidate, AlsK. To investigate the relationship between catalytic activities of promiscuous enzymes and their recruitment, we performed adaptive evolution of a glucokinase-deficient E. coli strain to restore glycolytic metabolism. We observed preferential recruitment of NanK via a trajectory involving early mutations that facilitate glucose uptake and amplify nanK transcription, followed by nonsynonymous substitutions in NanK that enhance the enzyme's promiscuous glucokinase activity. These substitutions reduced the native activity of NanK and reduced organismal fitness during growth on an N-acetylated carbon source, indicating that enzyme recruitment comes at a cost for growth on other substrates. Notably, the two most active candidates, NagK and Mak, were not recruited, suggesting that catalytic activity alone does not dictate evolutionary outcomes. The results highlight our lack of knowledge regarding biological drivers of enzyme recruitment and emphasize the need for a systems-wide approach to identify factors facilitating or constraining this important adaptive process.
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Affiliation(s)
- Ryan P Campbell
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL, USA
| | - A Carl Whittington
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL, USA
- Department of Biological Science, Florida State University, Tallahassee, FL, USA
| | - Diego A R Zorio
- Department of Biological Science, Florida State University, Tallahassee, FL, USA
| | - Brian G Miller
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL, USA
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2
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Vo TM, Park S. Metabolic engineering of Escherichia coli W3110 for efficient production of homoserine from glucose. Metab Eng 2022; 73:104-113. [PMID: 35803501 DOI: 10.1016/j.ymben.2022.07.001] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2022] [Revised: 06/12/2022] [Accepted: 07/01/2022] [Indexed: 10/17/2022]
Abstract
Efficient microbial cell factory for the production of homoserine from glucose has been developed by iterative and rational engineering of Escherichia coli W3110. The whole pathway from glucose to homoserine was divided into three groups, namely, glucose transport and glycolysis ('up-stream'), TCA and glyoxylate cycles ('mid-stream'), and homoserine module (conversion of aspartate to homoserine and its secretion; 'down-stream'), and the carbon flux in each group as well as between the groups were accelerated and balanced. Altogether, ∼18 genes were modified for active and consistent production of homoserine during both the actively-growing and non-growing stages of cultivation. Finally, fed-batch, two-stage bioreactor experiments, separating the growth from the production stage, were conducted for 61 h, which gave the high titer of 110.8 g/L, yield of 0.64 g/g glucose and volumetric productivity of 1.82 g/L/h, with an insignificant amount of acetate (<0.5 g/L) as the only noticeable byproduct. The metabolic engineering strategy employed in this study should be applicable for the biosynthesis of other amino acids or chemicals derived from aspartic acid.
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Affiliation(s)
- Toan Minh Vo
- School of Energy and Chemical Engineering, UNIST, Ulsan, 44919, South Korea
| | - Sunghoon Park
- School of Energy and Chemical Engineering, UNIST, Ulsan, 44919, South Korea.
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3
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A steady-state model of microbial acclimation to substrate limitation. PLoS Comput Biol 2020; 16:e1008140. [PMID: 32845915 PMCID: PMC7478835 DOI: 10.1371/journal.pcbi.1008140] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2020] [Revised: 09/08/2020] [Accepted: 07/09/2020] [Indexed: 11/19/2022] Open
Abstract
Microbes acclimate to changes in substrate availability by altering the number of transporters on the cell surface, however there is some disagreement on just how. We revisit the physics of substrate uptake and consider the steady-state scenario whereby cells have acclimated to maximize fitness. Flux balance analysis of a stoichiometric model of Escherichia coli was used in conjunction with quantitative proteomics data and molecular modeling of membrane transporters to reconcile these opposing views. An emergent feature of the proposed model is a critical substrate concentration S*, which delineates two rate limits. At concentrations above S*, transporter abundance can be regulated to maintain uptake rates as demanded by maximal growth rates, whereas below S*, uptake rates are strictly diffusion limited. In certain scenarios, the proposed model can take on a qualitatively different shape from the familiar hyperbolic kinetics curves, instead resembling the long-forgotten Blackman kinetics.
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Kim DG, Yoo SW, Kim M, Ko JK, Um Y, Oh MK. Improved 2,3-butanediol yield and productivity from lignocellulose biomass hydrolysate in metabolically engineered Enterobacter aerogenes. BIORESOURCE TECHNOLOGY 2020; 309:123386. [PMID: 32330805 DOI: 10.1016/j.biortech.2020.123386] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/27/2020] [Revised: 04/11/2020] [Accepted: 04/13/2020] [Indexed: 06/11/2023]
Abstract
We previously engineered Enterobacter aerogenesfor glucose and xylose co-utilization and 2,3-butanediol production. Here, strain EMY-22 was further engineered to improve the 2,3-butanediol titer, productivity, and yield by reducing the production of byproducts. To reduce succinate production, the budABC operon and galP gene were overexpressed, which increased 2,3-butanediol production. For further reduction of succinate and 2-ketogluconate production, maeA was selected and overexpressed in EMY-22. The optimally engineered strain produced 2,3-butanediol for a longer time and showed reduced byproduct formation from sugarcane bagasse hydrolysate under flask cultivation conditions. The engineered strain displayed 66.6, 13.4, and 16.8% improvements in titer, yield, productivity of 2,3-butanediol, respectively, compared to its parental strain under fed-batch fermentation conditions. The data demonstrate that the metabolic engineering to reduce byproduct formation is a promising strategy to improve 2,3-butanediol production from lignocellulosic biomass.
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Affiliation(s)
- Duck Gyun Kim
- Department of Chemical & Biological Engineering, Korea University, Seoul 02841, Republic of Korea
| | - Seok Woo Yoo
- Department of Chemical & Biological Engineering, Korea University, Seoul 02841, Republic of Korea
| | - Minsun Kim
- Department of Chemical & Biological Engineering, Korea University, Seoul 02841, Republic of Korea
| | - Ja Kyong Ko
- Clean Energy Research Center, Korea Institute of Science and Technology (KIST), Seoul 02792, Republic of Korea
| | - Youngsoon Um
- Clean Energy Research Center, Korea Institute of Science and Technology (KIST), Seoul 02792, Republic of Korea; Division of Energy and Environment Technology, University of Science and Technology (UST), Daejeon 34113, Republic of Korea; KU-KIST GreenSchool, Graduate School of Energy and Environment, Korea University, Seoul 02841, Republic of Korea
| | - Min-Kyu Oh
- Department of Chemical & Biological Engineering, Korea University, Seoul 02841, Republic of Korea.
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5
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Onyeabor M, Martinez R, Kurgan G, Wang X. Engineering transport systems for microbial production. ADVANCES IN APPLIED MICROBIOLOGY 2020; 111:33-87. [PMID: 32446412 DOI: 10.1016/bs.aambs.2020.01.002] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
The rapid development in the field of metabolic engineering has enabled complex modifications of metabolic pathways to generate a diverse product portfolio. Manipulating substrate uptake and product export is an important research area in metabolic engineering. Optimization of transport systems has the potential to enhance microbial production of renewable fuels and chemicals. This chapter comprehensively reviews the transport systems critical for microbial production as well as current genetic engineering strategies to improve transport functions and thus production metrics. In addition, this chapter highlights recent advancements in engineering microbial efflux systems to enhance cellular tolerance to industrially relevant chemical stress. Lastly, future directions to address current technological gaps are discussed.
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Affiliation(s)
- Moses Onyeabor
- School of Life Sciences, Arizona State University, Tempe, AZ, United States
| | - Rodrigo Martinez
- School of Life Sciences, Arizona State University, Tempe, AZ, United States
| | - Gavin Kurgan
- School of Life Sciences, Arizona State University, Tempe, AZ, United States
| | - Xuan Wang
- School of Life Sciences, Arizona State University, Tempe, AZ, United States.
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Kurgan G, Sievert C, Flores A, Schneider A, Billings T, Panyon L, Morris C, Taylor E, Kurgan L, Cartwright R, Wang X. Parallel experimental evolution reveals a novel repressive control of GalP on xylose fermentation in Escherichia coli. Biotechnol Bioeng 2019; 116:2074-2086. [PMID: 31038200 PMCID: PMC11161036 DOI: 10.1002/bit.27004] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2019] [Revised: 03/28/2019] [Accepted: 04/25/2019] [Indexed: 12/25/2022]
Abstract
Efficient xylose utilization will facilitate microbial conversion of lignocellulosic sugar mixtures into valuable products. In Escherichia coli, xylose catabolism is controlled by carbon catabolite repression (CCR). However, in E. coli such as the succinate-producing strain KJ122 with disrupted CCR, xylose utilization is still inhibited under fermentative conditions. To probe the underlying genetic mechanisms inhibiting xylose utilization, we evolved KJ122 to enhance its xylose fermentation abilities in parallel and characterized the potential convergent genetic changes shared by multiple independently evolved strains. Whole-genome sequencing revealed that convergent mutations occurred in the galactose regulon during adaptive laboratory evolution potentially decreasing the transcriptional level or the activity of GalP, a galactose permease. We showed that deletion of galP increased xylose utilization in both KJ122 and wild-type E. coli, demonstrating a common repressive role of GalP for xylose fermentation. Concomitantly, induced expression of galP from a plasmid repressed xylose fermentation. Transcriptome analysis using RNA sequencing indicates that galP inactivation increases transcription levels of many catabolic genes for secondary sugars including xylose and arabinose. The repressive role of GalP for fermenting secondary sugars in E. coli suggests that utilization of GalP as a substitute glucose transporter is undesirable for conversion of lignocellulosic sugar mixtures.
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Affiliation(s)
- Gavin Kurgan
- School of Life Sciences, Arizona State University, Tempe, Arizona
| | - Christian Sievert
- School of Life Sciences, Arizona State University, Tempe, Arizona
- The Biodesign Institute, Arizona State University, Tempe, Arizona
| | - Andrew Flores
- Chemical Engineering Program, School for Engineering of Matter, Transport, and Energy, Arizona State University, Tempe, Arizona
| | - Aidan Schneider
- School of Life Sciences, Arizona State University, Tempe, Arizona
| | - Thomas Billings
- School of Life Sciences, Arizona State University, Tempe, Arizona
| | - Larry Panyon
- School of Life Sciences, Arizona State University, Tempe, Arizona
| | - Chandler Morris
- School of Life Sciences, Arizona State University, Tempe, Arizona
| | - Eric Taylor
- School of Life Sciences, Arizona State University, Tempe, Arizona
| | - Logan Kurgan
- School of Life Sciences, Arizona State University, Tempe, Arizona
| | - Reed Cartwright
- School of Life Sciences, Arizona State University, Tempe, Arizona
- The Biodesign Institute, Arizona State University, Tempe, Arizona
| | - Xuan Wang
- School of Life Sciences, Arizona State University, Tempe, Arizona
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7
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Flores AD, Ayla EZ, Nielsen DR, Wang X. Engineering a Synthetic, Catabolically Orthogonal Coculture System for Enhanced Conversion of Lignocellulose-Derived Sugars to Ethanol. ACS Synth Biol 2019; 8:1089-1099. [PMID: 30979337 DOI: 10.1021/acssynbio.9b00007] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Fermentation of lignocellulosic sugar mixtures is often suboptimal due to inefficient xylose catabolism and sequential sugar utilization caused by carbon catabolite repression. Unlike in conventional applications employing a single engineered strain, the alternative development of synthetic microbial communities facilitates the execution of complex metabolic tasks by exploiting the unique community features, including modularity, division of labor, and facile tunability. A series of synthetic, catabolically orthogonal coculture systems were systematically engineered, as derived from either wild-type Escherichia coli W or ethanologenic LY180. Net catabolic activities were effectively balanced by simple tuning of the inoculum ratio between specialist strains, which enabled coutilization (98% of 100 g L-1 total sugars) of glucose-xylose mixtures (2:1 by mass) for both culture systems in simple batch fermentations. The engineered ethanologenic cocultures achieved ethanol titer (46 g L-1), productivity (488 mg L-1 h-1), and yield (∼90% of theoretical maximum), which were all significantly increased compared to LY180 monocultures.
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Affiliation(s)
- Andrew D. Flores
- Chemical Engineering, School for Engineering of Matter, Transport, and Energy, Arizona State University, ECG 301, 501 E. Tyler Mall, Tempe, Arizona 85287, United States
| | - E. Zeynep Ayla
- Chemical Engineering, School for Engineering of Matter, Transport, and Energy, Arizona State University, ECG 301, 501 E. Tyler Mall, Tempe, Arizona 85287, United States
| | - David R. Nielsen
- Chemical Engineering, School for Engineering of Matter, Transport, and Energy, Arizona State University, ECG 301, 501 E. Tyler Mall, Tempe, Arizona 85287, United States
| | - Xuan Wang
- School of Life Sciences, Arizona State University, 427 E. Tyler Mall, Tempe, Arizona 85287, United States
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8
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Stebegg R, Schmetterer G, Rompel A. Transport of organic substances through the cytoplasmic membrane of cyanobacteria. PHYTOCHEMISTRY 2019; 157:206-218. [PMID: 30447471 DOI: 10.1016/j.phytochem.2018.08.013] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/06/2018] [Revised: 07/25/2018] [Accepted: 08/17/2018] [Indexed: 06/09/2023]
Abstract
Cyanobacteria are mainly known to incorporate inorganic molecules like carbon dioxide and ammonia from the environment into organic material within the cell. Nevertheless cyanobacteria do import and export organic substances through the cytoplasmic membrane and these processes are essential for all cyanobacteria. In addition understanding the mechanisms of transport of organic molecules through the cytoplasmic membrane might become very important. Genetically modified strains of cyanobacteria could serve as producers and exporters of commercially important substances. In this review we attempt to present all data of transport of organic molecules through the cytoplasmic membrane of cyanobacteria that are currently available with the transported molecules ordered according to their chemical classes.
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Affiliation(s)
- Ronald Stebegg
- Universität Wien, Fakultät für Chemie, Institut für Biophysikalische Chemie, Althanstraße 14, 1090 Wien, Austria(1).
| | - Georg Schmetterer
- Universität Wien, Fakultät für Chemie, Institut für Biophysikalische Chemie, Althanstraße 14, 1090 Wien, Austria(1).
| | - Annette Rompel
- Universität Wien, Fakultät für Chemie, Institut für Biophysikalische Chemie, Althanstraße 14, 1090 Wien, Austria(1).
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9
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Kyselova L, Kreitmayer D, Kremling A, Bettenbrock K. Type and capacity of glucose transport influences succinate yield in two-stage cultivations. Microb Cell Fact 2018; 17:132. [PMID: 30153840 PMCID: PMC6112142 DOI: 10.1186/s12934-018-0980-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2018] [Accepted: 08/22/2018] [Indexed: 12/03/2022] Open
Abstract
Background Glucose is the main carbon source of E. coli and a typical substrate in production processes. The main glucose uptake system is the glucose specific phosphotransferase system (Glc-PTS). The PTS couples glucose uptake with its phosphorylation. This is achieved by the concomitant conversion of phosphoenolpyruvate (PEP) to pyruvate. The Glc-PTS is hence unfavorable for the production of succinate as this product is derived from PEP. Results We studied, in a systematic manner, the effect of knocking out the Glc-PTS and of replacing it with the glucose facilitator (Glf) of Zymomonas mobilis on succinate yield and productivity. For this study a set of strains derived from MG1655, carrying deletions of ackA-pta, adhE and ldhA that prevent the synthesis of competing fermentation products, were constructed and tested in two-stage cultivations. The data show that inactivation of the Glc-PTS achieved a considerable increase in succinate yield and productivity. On the other hand, aerobic growth of this strain on glucose was strongly decreased. Expression of the alternative glucose transporter, Glf, in this strain enhanced aerobic growth but productivity and yield under anaerobic conditions were slightly decreased. This decrease in succinate yield was accompanied by pyruvate production. Yield could be increased in both Glc-PTS mutants by overexpressing phosphoenolpyruvate carboxykinase (Pck). Productivity on the other hand, was decreased in the strain without alternative glucose transporter but strongly increased in the strain expressing Glf. The experiments were complemented by flux balance analysis in order to check the observed yields against the maximal theoretical yields. Furthermore, the phosphorylation state of EIIAGlc was determined. The data indicate that the ratio of PEP to pyruvate is correlating with pyruvate excretion. This ratio is affected by the PTS reaction as well as by further reactions at the PEP/pyruvate node. Conclusions The results show that for optimization of succinate yield and productivity it is not sufficient to knock out or introduce single reactions. Rather, balancing of the fluxes of central metabolism most important at the PEP/pyruvate node is important. Electronic supplementary material The online version of this article (10.1186/s12934-018-0980-1) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- L Kyselova
- Team Experimental Systems Biology, Max Planck Institute for Dynamics of Complex Technical Systems, Sandtorstr.1, 39106, Magdeburg, Germany
| | - D Kreitmayer
- Systembiotechnologie, Technische Universität München, Bolzmannstr. 15, 85748, Garching, Germany
| | - A Kremling
- Systembiotechnologie, Technische Universität München, Bolzmannstr. 15, 85748, Garching, Germany
| | - K Bettenbrock
- Team Experimental Systems Biology, Max Planck Institute for Dynamics of Complex Technical Systems, Sandtorstr.1, 39106, Magdeburg, Germany.
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Gu Y, Deng J, Liu Y, Li J, Shin H, Du G, Chen J, Liu L. Rewiring the Glucose Transportation and Central Metabolic Pathways for Overproduction of
N
‐Acetylglucosamine in
Bacillus subtilis. Biotechnol J 2017; 12. [DOI: 10.1002/biot.201700020] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2017] [Revised: 06/22/2017] [Indexed: 01/21/2023]
Affiliation(s)
- Yang Gu
- Key Laboratory of Carbohydrate Chemistry and Biotechnology, Ministry of EducationJiangnan UniversityWuxi214122China
- Key Laboratory of Industrial Biotechnology, Ministry of EducationJiangnan UniversityWuxi214122China
| | - Jieying Deng
- Key Laboratory of Carbohydrate Chemistry and Biotechnology, Ministry of EducationJiangnan UniversityWuxi214122China
- Key Laboratory of Industrial Biotechnology, Ministry of EducationJiangnan UniversityWuxi214122China
| | - Yanfeng Liu
- Key Laboratory of Carbohydrate Chemistry and Biotechnology, Ministry of EducationJiangnan UniversityWuxi214122China
- Key Laboratory of Industrial Biotechnology, Ministry of EducationJiangnan UniversityWuxi214122China
| | - Jianghua Li
- Key Laboratory of Carbohydrate Chemistry and Biotechnology, Ministry of EducationJiangnan UniversityWuxi214122China
- Key Laboratory of Industrial Biotechnology, Ministry of EducationJiangnan UniversityWuxi214122China
| | - Hyun‐dong Shin
- School of Chemical and Biomolecular EngineeringGeorgia Institute of TechnologyAtlantaGA30332USA
| | - Guocheng Du
- Key Laboratory of Carbohydrate Chemistry and Biotechnology, Ministry of EducationJiangnan UniversityWuxi214122China
- Key Laboratory of Industrial Biotechnology, Ministry of EducationJiangnan UniversityWuxi214122China
| | - Jian Chen
- Key Laboratory of Carbohydrate Chemistry and Biotechnology, Ministry of EducationJiangnan UniversityWuxi214122China
- Key Laboratory of Industrial Biotechnology, Ministry of EducationJiangnan UniversityWuxi214122China
| | - Long Liu
- Key Laboratory of Carbohydrate Chemistry and Biotechnology, Ministry of EducationJiangnan UniversityWuxi214122China
- Key Laboratory of Industrial Biotechnology, Ministry of EducationJiangnan UniversityWuxi214122China
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11
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Engineering Corynebacterium glutamicum for fast production of l-lysine and l-pipecolic acid. Appl Microbiol Biotechnol 2016; 100:8075-90. [DOI: 10.1007/s00253-016-7682-6] [Citation(s) in RCA: 69] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2016] [Revised: 06/07/2016] [Accepted: 06/13/2016] [Indexed: 11/25/2022]
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12
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Mechanism of inhibition of human glucose transporter GLUT1 is conserved between cytochalasin B and phenylalanine amides. Proc Natl Acad Sci U S A 2016; 113:4711-6. [PMID: 27078104 PMCID: PMC4855560 DOI: 10.1073/pnas.1603735113] [Citation(s) in RCA: 143] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Cancerous cells have an acutely increased demand for energy, leading to increased levels of human glucose transporter 1 (hGLUT1). This up-regulation suggests hGLUT1 as a target for therapeutic inhibitors addressing a multitude of cancer types. Here, we present three inhibitor-bound, inward-open structures of WT-hGLUT1 crystallized with three different inhibitors: cytochalasin B, a nine-membered bicyclic ring fused to a 14-membered macrocycle, which has been described extensively in the literature of hGLUTs, and two previously undescribed Phe amide-derived inhibitors. Despite very different chemical backbones, all three compounds bind in the central cavity of the inward-open state of hGLUT1, and all binding sites overlap the glucose-binding site. The inhibitory action of the compounds was determined for hGLUT family members, hGLUT1-4, using cell-based assays, and compared with homology models for these hGLUT members. This comparison uncovered a probable basis for the observed differences in inhibition between family members. We pinpoint regions of the hGLUT proteins that can be targeted to achieve isoform selectivity, and show that these same regions are used for inhibitors with very distinct structural backbones. The inhibitor cocomplex structures of hGLUT1 provide an important structural insight for the design of more selective inhibitors for hGLUTs and hGLUT1 in particular.
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13
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Liu SP, Zhang L, Mao J, Ding ZY, Shi GY. Metabolic engineering of Escherichia coli for the production of phenylpyruvate derivatives. Metab Eng 2015; 32:55-65. [DOI: 10.1016/j.ymben.2015.09.007] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2015] [Revised: 09/08/2015] [Accepted: 09/09/2015] [Indexed: 12/18/2022]
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14
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Accumulation of d-glucose from pentoses by metabolically engineered Escherichia coli. Appl Environ Microbiol 2015; 81:3387-94. [PMID: 25746993 DOI: 10.1128/aem.04058-14] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2014] [Accepted: 03/02/2015] [Indexed: 12/30/2022] Open
Abstract
Escherichia coli that is unable to metabolize d-glucose (with knockouts in ptsG, manZ, and glk) accumulates a small amount of d-glucose (yield of about 0.01 g/g) during growth on the pentoses d-xylose or l-arabinose as a sole carbon source. Additional knockouts in the zwf and pfkA genes, encoding, respectively, d-glucose-6-phosphate 1-dehydrogenase and 6-phosphofructokinase I (E. coli MEC143), increased accumulation to greater than 1 g/liter d-glucose and 100 mg/liter d-mannose from 5 g/liter d-xylose or l-arabinose. Knockouts of other genes associated with interconversions of d-glucose-phosphates demonstrate that d-glucose is formed primarily by the dephosphorylation of d-glucose-6-phosphate. Under controlled batch conditions with 20 g/liter d-xylose, MEC143 generated 4.4 g/liter d-glucose and 0.6 g/liter d-mannose. The results establish a direct link between pentoses and hexoses and provide a novel strategy to increase carbon backbone length from five to six carbons by directing flux through the pentose phosphate pathway.
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Xia T, Altman E, Eiteman MA. Succinate production from xylose-glucose mixtures using a consortium of engineeredEscherichia coli. Eng Life Sci 2014. [DOI: 10.1002/elsc.201400113] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Affiliation(s)
- Tian Xia
- BioChemical Engineering, College of Engineering; University of Georgia; Athens GA USA
| | - Elliot Altman
- Department of Biology; Middle Tennessee State University; Murfreesboro TN USA
| | - Mark A. Eiteman
- BioChemical Engineering, College of Engineering; University of Georgia; Athens GA USA
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16
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The transport and mediation mechanisms of the common sugars in Escherichia coli. Biotechnol Adv 2014; 32:905-19. [DOI: 10.1016/j.biotechadv.2014.04.009] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2013] [Revised: 03/23/2014] [Accepted: 04/18/2014] [Indexed: 11/17/2022]
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17
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Andreeva IG, Golubeva LI, Katashkina JI. Putative GalP, XylE, and FucP H+ symporters from Pantoea ananatis are capable of transporting glucose into Escherichia coli cells. APPL BIOCHEM MICRO+ 2013. [DOI: 10.1134/s0003683813070016] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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18
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Fuentes LG, Lara AR, Martínez LM, Ramírez OT, Martínez A, Bolívar F, Gosset G. Modification of glucose import capacity in Escherichia coli: physiologic consequences and utility for improving DNA vaccine production. Microb Cell Fact 2013; 12:42. [PMID: 23638701 PMCID: PMC3655049 DOI: 10.1186/1475-2859-12-42] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2013] [Accepted: 04/26/2013] [Indexed: 01/21/2023] Open
Abstract
Background The bacterium Escherichia coli can be grown employing various carbohydrates as sole carbon and energy source. Among them, glucose affords the highest growth rate. This sugar is nowadays widely employed as raw material in industrial fermentations. When E. coli grows in a medium containing non-limiting concentrations of glucose, a metabolic imbalance occurs whose main consequence is acetate secretion. The production of this toxic organic acid reduces strain productivity and viability. Solutions to this problem include reducing glucose concentration by substrate feeding strategies or the generation of mutant strains with impaired glucose import capacity. In this work, a collection of E. coli strains with inactive genes encoding proteins involved in glucose transport where generated to determine the effects of reduced glucose import capacity on growth rate, biomass yield, acetate and production of an experimental plasmid DNA vaccine (pHN). Results A group of 15 isogenic derivatives of E. coli W3110 were generated with single and multiple deletions of genes encoding glucose, mannose, beta-glucoside, maltose and N-acetylglucosamine components of the phosphoenolpyruvate:sugar phosphotransferase system (PTS), as well as the galactose symporter and the Mgl galactose/glucose ABC transporter. These strains were characterized by growing them in mineral salts medium supplemented with 2.5 g/L glucose. Maximum specific rates of glucose consumption (qs) spanning from 1.33 to 0.32 g/g h were displayed by the group of mutants and W3110, which resulted in specific growth rates ranging from 0.65-0.18 h-1. Acetate accumulation was reduced or abolished in cultures with all mutant strains. W3110 and five selected mutant derivatives were transformed with pHN. A 3.2-fold increase in pHN yield on biomass was observed in cultures of a mutant strain with deletion of genes encoding the glucose and mannose PTS components, as well as Mgl. Conclusions The group of E. coli mutants generated in this study displayed a reduction or elimination of overflow metabolism and a linear correlation between qs and the maximum specific growth rate as well as the acetate production rate. By comparing DNA vaccine production parameters among some of these mutants, it was possible to identify a near-optimal glucose import rate value for this particular application. The strains employed in this study should be a useful resource for studying the effects of different predefined qs values on production capacity for various biotechnological products.
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Affiliation(s)
- Laura G Fuentes
- Departamento de Ingeniería Celular y Biocatálisis, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, Mexico
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Morzhakova AA, Skorokhodova AY, Gulevich AY, Debabov VG. Recombinant Escherichia coli strains deficient in mixed acid fermentation pathways and capable of rapid aerobic growth on glucose with a reduced crabtree effect. APPL BIOCHEM MICRO+ 2013. [DOI: 10.1134/s0003683813020105] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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20
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Glucose transport in Escherichia coli mutant strains with defects in sugar transport systems. J Bacteriol 2012; 194:5897-908. [PMID: 22923596 DOI: 10.1128/jb.01502-12] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
In Escherichia coli, several systems are known to transport glucose into the cytoplasm. The main glucose uptake system under batch conditions is the glucose phosphoenolpyruvate:carbohydrate phosphotransferase system (glucose PTS), but the mannose PTS and the galactose and maltose transporters also can translocate glucose. Mutant strains which lack the enzyme IIBC (EIIBC) protein of the glucose PTS have been investigated previously because their lower rate of acetate formation offers advantages in industrial applications. Nevertheless, a systematic study to analyze the impact of the different glucose uptake systems has not been undertaken. Specifically, how the bacteria cope with the deletion of the major glucose uptake system and which alternative transporters react to compensate for this deficit have not been studied in detail. Therefore, a series of mutant strains were analyzed in aerobic and anaerobic batch cultures, as well as glucose-limited continuous cultivations. Deletion of EIIBC disturbs glucose transport severely in batch cultures; cyclic AMP (cAMP)-cAMP receptor protein (CRP) levels rise, and induction of the mgl operon occurs. Nevertheless, Mgl activity is not essential for growth of these mutants, since deletion of this transporter did not affect the growth rate; the activities of the remaining transporters seem to be sufficient. Under conditions of glucose limitation, mgl is upregulated 23-fold compared to levels for growth under glucose excess. Despite the strong induction of mgl upon glucose limitation, deletion of this transport system did not lead to further changes. Although the galactose transporters are often regarded as important for glucose uptake at micromolar concentrations, the glucose as well as mannose PTS might be sufficient for growth at this relatively low dilution rate.
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21
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Recruiting alternative glucose utilization pathways for improving succinate production. Appl Microbiol Biotechnol 2012; 97:2513-20. [PMID: 22895848 DOI: 10.1007/s00253-012-4344-1] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2012] [Revised: 07/28/2012] [Accepted: 07/30/2012] [Indexed: 01/14/2023]
Abstract
The phosphoenolpyruvate (PEP): carbohydrate phosphotransferase system (PTS) of Escherichia coli was usually inactivated to increase PEP supply for succinate production. However, cell growth and glucose utilization rate decreased significantly with PTS inactivation. In this work, two glucose transport proteins and two glucokinases (Glk) from E. coli and Zymomonas mobilis were recruited in PTS(-) strains, and their impacts on glucose utilization and succinate production were compared. All PTS(-) strains recruiting Z. mobilis glucose facilitator Glf had higher glucose utilization rates than PTS(-) strains using E. coli galactose permease (GalP), which was suggested to be caused by higher glucose transport velocity and lower energetic cost of Glf. The highest rate obtained by combinatorial modulation of glf and glk E. coli (2.13 g/L•h) was 81 % higher than the wild-type E. coli and 30 % higher than the highest rate obtained by combinatorial modulation of galP and glk E. coli . On the other hand, although glucokinase activities increased after replacing E. coli Glk with isoenzyme of Z. mobilis, glucose utilization rate decreased to 0.58 g/L•h, which was assumed due to tight regulation of Z. mobilis Glk by energy status of the cells. For succinate production, using GalP led to a 20 % increase in succinate productivity, while recruiting Glf led to a 41 % increase. These efficient alternative glucose utilization pathways obtained in this work can also be used for production of many other PEP-derived chemicals, such as malate, fumarate, and aromatic compounds.
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22
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Jones LN, Baldwin SA, Henderson PJF, Ashcroft AE. Defining topological features of membrane proteins by nanoelectrospray ionisation mass spectrometry. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2010; 24:276-284. [PMID: 20058234 DOI: 10.1002/rcm.4387] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
The D-galactose-H(+) symport protein, GalP, of Escherichia coli is the bacterial homologue of the human glucose transport protein, GLUT1. Here we demonstrate that mass spectrometry can be used to map modification by covalently bound reagents, and also to detect structural changes in the GalP protein that occur upon substrate binding. The small thiol-group-specific reagent N-ethylmaleimide (NEM) was used to modify the cysteine residues in GalP(His)(6) both alone and in the presence of D-glucose, a known substrate. Employing a mixture of proteolysis and thermal degradation methods, the three cysteine residues were found to undergo sequential reactions with NEM, with Cys374 being modified first, followed by Cys389 and finally Cys19, thus indicating their different accessibilities within the three-dimensional structure of the protein. Prior binding of the substrate D-glucose to the protein protected Cys19 and Cys374 against NEM modification, but not Cys389. Cys374 had been expected to be shielded by D-glucose binding while Cys389 had been expected to be unaffected, consistent with their proposed respective locations in the vicinity of, and distant from, the sugar binding site. However, the inaccessibility of Cys19 was unexpected and suggests a structural change in the protein promoted by D-glucose binding which changes the proximity of Cys19 with respect to the D-glucose-binding site.
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Affiliation(s)
- Lynsey N Jones
- Astbury Centre for Structural Molecular Biology, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, UK
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23
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Patching SG, Psakis G, Baldwin SA, Baldwin J, Henderson PJF, Middleton DA. Relative substrate affinities of wild-type and mutant forms of the Escherichia coli sugar transporter GalP determined by solid-state NMR. Mol Membr Biol 2009; 25:474-84. [PMID: 18798051 DOI: 10.1080/09687680802371963] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
Solid-state nuclear magnetic resonance (SSNMR) spectroscopy is used for the first time to examine the relative substrate-binding affinities of mutant forms of the Escherichia coli sugar transporter GalP in membrane preparations. The SSNMR method of (13)C cross-polarization magic-angle spinning (CP-MAS) is applied to five site-specific mutants (W56F, W239F, R316W, T336Y and W434F), which have a range of different sugar-transport activities compared to the wild-type protein. It is shown that binding of the substrate D-glucose can be detected independently of sugar transport activity using SSNMR, and that the NMR peak intensities for uniformly (13)C-labelled glucose are consistent with wild-type GalP and the mutants having different affinities for the substrate. The W239F and W434F mutants showed binding affinities similar to that of the wild-type protein, whereas the affinity of glucose-binding to the W56F mutant was reduced. The R316W mutant showed no detectable binding; this position corresponds to the second basic residue in the highly conserved (R/K)XGR(R/K) motif in the major facilitator superfamily of transport proteins and to a mutation in human GLUT1 found in individuals with GLUT1-deficiency syndrome. The T336Y mutant also showed no detectable binding; this mutation is likely to have perturbed helix structure or packing to an extent that conformational changes in the protein are hindered. The effects of the mutations on substrate-binding are discussed with reference to the putative positions of the residues in a 3D homology model of GalP based on the X-ray crystal structure of the E. coli glycerol-3-phosphate transporter GlpT.
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Affiliation(s)
- Simon G Patching
- Astbury Centre for Structural Molecular Biology and Institute of Membrane and Systems Biology, University of Leeds, Leeds, UK.
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24
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Castro R, Neves AR, Fonseca LL, Pool WA, Kok J, Kuipers OP, Santos H. Characterization of the individual glucose uptake systems of Lactococcus lactis: mannose-PTS, cellobiose-PTS and the novel GlcU permease. Mol Microbiol 2008; 71:795-806. [PMID: 19054326 DOI: 10.1111/j.1365-2958.2008.06564.x] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
According to previous reports, Lactococcus lactis imports glucose via two distinct phosphoenolpyruvate:phosphotransferase systems (mannose-PTS and cellobiose-PTS) and one or more unknown non-PTS permease(s). GlcU was identified as the sole non-PTS permease involved in the transport of glucose. Additionally, the biochemical properties of PTS(Man), PTS(Cel) and GlcU were characterized in double knockout mutants with glucose uptake restricted to a single system. Transport susceptibility to protonophores indicated that glucose uptake via GlcU is proton-motive force dependent. Competition assays revealed a high specificity of GlcU for glucose. Furthermore, the permease has low affinity for glucose and displays strong preference for the beta-anomer as shown by the profiles of consumption of the two glucose anomers studied by (13)C-NMR. Similar kinetic properties were found for PTS(Cel), while PTS(Man) is a high-affinity system recognizing equally well the two anomeric forms of glucose. Transcripts of the genes encoding the three transporters are present simultaneously in the parent strain NZ9000 as shown by reverse transcription-PCR. Investigation of the distribution of GlcU homologues among bacteria showed that these proteins are restricted to the low-GC Gram-positive Firmicutes. This work completes the identification of the glucose transport systems in L. lactis MG1363.
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Affiliation(s)
- Rute Castro
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Rua da Quinta Grande 6, Oeiras, Portugal
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Gosset G. Improvement of Escherichia coli production strains by modification of the phosphoenolpyruvate:sugar phosphotransferase system. Microb Cell Fact 2005; 4:14. [PMID: 15904518 PMCID: PMC1156936 DOI: 10.1186/1475-2859-4-14] [Citation(s) in RCA: 195] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2005] [Accepted: 05/16/2005] [Indexed: 12/22/2022] Open
Abstract
The application of metabolic engineering in Escherichia coli has resulted in the generation of strains with the capacity to produce metabolites of commercial interest. Biotechnological processes with these engineered strains frequently employ culture media containing glucose as the carbon and energy source. In E. coli, the phosphoenolpyruvate:sugar phosphotransferase system (PTS) transports glucose when this sugar is present at concentrations like those used in production fermentations. This protein system is involved in phosphoenolpyruvate-dependent sugar transport, therefore, its activity has an important impact on carbon flux distribution in the phosphoenolpyruvate and pyruvate nodes. Furthermore, PTS has a very important role in carbon catabolite repression. The properties of PTS impose metabolic and regulatory constraints that can hinder strain productivity. For this reason, PTS has been a target for modification with the purpose of strain improvement. In this review, PTS characteristics most relevant to strain performance and the different strategies of PTS modification for strain improvement are discussed. Functional replacement of PTS by alternative phosphoenolpyruvate-independent uptake and phosphorylation activities has resulted in significant improvements in product yield from glucose and productivity for several classes of metabolites. In addition, inactivation of PTS components has been applied successfully as a strategy to abolish carbon catabolite repression, resulting in E. coli strains that use more efficiently sugar mixtures, such as those obtained from lignocellulosic hydrolysates.
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Affiliation(s)
- Guillermo Gosset
- Departamento de Ingeniería Celular y Biocatálisis, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apdo, Postal 510-3, Cuernavaca, Mor, 62250, México.
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Venter H, Ashcroft AE, Keen JN, Henderson PJF, Herbert RB. Molecular dissection of membrane-transport proteins: mass spectrometry and sequence determination of the galactose-H+ symport protein, GalP, of Escherichia coli and quantitative assay of the incorporation of [ring-2-13C]histidine and (15)NH(3). Biochem J 2002; 363:243-52. [PMID: 11931651 PMCID: PMC1222472 DOI: 10.1042/0264-6021:3630243] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The molecular mass of the galactose-H(+) symport protein GalP, as its histidine-tagged derivative GalP(His)(6), has been determined by electrospray MS (ESI-MS) with an error of <0.02%. One methionine residue, predicted to be present from the DNA sequence, was deduced to be absent. This is a significant advance on the estimation of the molecular masses of membrane-transport proteins by SDS/PAGE, where there is a consistent under-estimation of the true molecular mass due to anomalous electrophoretic migration. Addition of a size-exclusion chromatography step after Ni(2+)-nitrilotriacetate affinity purification was essential to obtain GalP(His)(6) suitable for ESI-MS. Controlled trypsin, trypsin+chymotrypsin and CNBr digestion of the protein yielded peptide fragments suitable for ESI-MS and tandem MS analysis, and accurate mass determination of the derived fragments resulted in identification of 82% of the GalP(His)(6) protein. Tandem MS analysis of selected peptides then afforded 49% of the actual amino acid sequence of the protein; the absence of the N-terminal methionine was confirmed. Matrix-assisted laser-desorption ionization MS allowed identification of one peptide that was not detected by ESI-MS. All the protein/peptide mass and sequence determinations were in accord with the predictions of amino acid sequence deduced from the DNA sequence of the galP gene. [ring-2-(13)C]Histidine was incorporated into GalP(His)(6) in vivo, and ESI-MS analysis enabled the measurement of a high (80%) and specific incorporation of label into the histidine residues in the protein. MS could also be used to confirm the labelling of the protein by (15)NH(3) (93% enrichment) and [(19)F]tryptophan (83% enrichment). Such MS measurements will serve in the future analysis of the structures of membrane-transport proteins by NMR, and of their topology by indirect techniques.
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Affiliation(s)
- Henrietta Venter
- Astbury Centre for Structural Molecular Biology, School of Biochemistry and Molecular Biology, University of Leeds, Leeds LS2 9JT, U.K
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27
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Flores S, Gosset G, Flores N, de Graaf AA, Bolívar F. Analysis of carbon metabolism in Escherichia coli strains with an inactive phosphotransferase system by (13)C labeling and NMR spectroscopy. Metab Eng 2002; 4:124-37. [PMID: 12009792 DOI: 10.1006/mben.2001.0209] [Citation(s) in RCA: 121] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
We have developed Escherichia coli strains that internalize glucose utilizing the GalP permease instead of the phosphoenolpyruvate:carbohydrate phosphotransferase system. It has been demonstrated that a strain with these modifications (PTS(-)Glc(+)) can direct more carbon flux into the aromatic pathway than the wild-type parental strain (N. Flores et al., 1996, Nat. Biotechnol. 14, 620-623; G. Gosset et al., 1996, J. Ind. Microbiol. 17, 47-52; J. L. Baéz et al., 2001, Biotechnol. Bioeng. 73, 530-535). In this study, we have determined and compared the carbon fluxes of a wild-type strain (JM101), a PTS(-)Glc(-) strain, and two isogenic PTS(-)Glc(+) derivatives named PB12 and PB13 by combining genetic, biochemical, and NMR approaches. It was determined that in these strains a functional glk gene in the chromosome is required for rapid glucose consumption; furthermore, glucokinase-specific activities were higher than in the wild-type strain. (13)C labeling and NMR analysis allowed the determination of differences in vivo which include higher glycolytic fluxes of 93.1 and 89.2% compared with the 76.6% obtained for the wild-type E. coli. In PB12 and PB13 we found a flux through the malic enzymes of 4 and 10%, respectively, compared to zero in the wild-type strain. While flux through the Pck enzyme was absent in PB12 and PB13, in the wild type it was 7.7%. Finally, it was found that in the JM101 and PB12 strains both the oxidative and the nonoxidative branches of the pentose phosphate pathway contributed to ribose 5-phosphate synthesis, whereas in PB13 this pentose was synthesized almost exclusively through the oxidative branch. The determined carbon fluxes correlate with biochemical and genetic characterizations.
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Affiliation(s)
- S Flores
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, 62250 Cuernavaca, México
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28
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Báez JL, Bolívar F, Gosset G. Determination of 3-deoxy-D-arabino-heptulosonate 7-phosphate productivity and yield from glucose in Escherichia coli devoid of the glucose phosphotransferase transport system. Biotechnol Bioeng 2001; 73:530-5. [PMID: 11344458 DOI: 10.1002/bit.1088] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The effect of inactivation of the glucose phosphotransferase transport system (PTS) on 3-deoxy-D-arabino-heptulosonate 7-phosphate (DAHP) productivity and yield from glucose in Escherichia coli is reported. Strains used in this study were the PTS(+) PB103 and its PTS(-) glucose(+) derivative NF9. Their aroB(-) derivatives PB103B and NF9B were constructed to allow accurate measurement of total carbon flow into the aromatic pathway. The measured specific rates of DAHP synthesis were 0.55 and 0.94 mmol/g-dcw. h and the DAHP molar yields from glucose were 0.43 and 0.71 mol/mol for the PTS(+) aroB(-)and the PTS(-) glucose(+) aroB(-)strains, respectively. For the latter strain, this value represents 83% of the maximum theoretical yield for DAHP synthesis from glucose.
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Affiliation(s)
- J L Báez
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apdo. Postal 510-3. Cuernavaca, Morelos 62250, México
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McDonald TP, Henderson PJ. Cysteine residues in the D-galactose-H+ symport protein of Escherichia coli: effects of mutagenesis on transport, reaction with N-ethylmaleimide and antibiotic binding. Biochem J 2001; 353:709-17. [PMID: 11171069 PMCID: PMC1221618 DOI: 10.1042/0264-6021:3530709] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The galactose-H(+) membrane-transport protein, GalP, of Escherichia coli is similar in substrate specificity and susceptibility to cytochalasin B and forskolin, to the human GLUT1 sugar-transport protein; furthermore, they are about 30% identical in amino acid sequence. Transport activities of both GalP and GLUT1 are inhibited by the thiol-group-specific reagent, N-ethylmaleimide. GalP contains only three cysteine residues at positions 19, 374 and 389, each of which we have mutated, singly and in combination, to serine. Each single change of Cys-->Ser has only a minor effect on transport activity, whereas alteration of all three simultaneously profoundly diminishes V(max) for transport. The high level of expression of the GalP protein facilitates measurements of the reactivity of each mutant with N-ethylmaleimide or eosin 5-maleimide, which conclusively demonstrate that Cys(374) is the site of covalent modification by the reagents. By comparing the reactivity of Cys(374) in right-side-out and inside-out vesicles it appears that Cys(374) is located on the cytoplasmic face of the GalP protein. Although impaired in transport activity, the 'Cys-free' mutant, with all three cysteine residues mutated into serine, binds cytochalasin B and forskolin with wild-type affinities. All these results are interpreted in terms of a 12-helix model of the folding of the protein, in which the relative orientations of helix 10, containing the reactive Cys(374) residue, and helix 11, containing the unreactive Cys(389) residue, can now be defined.
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Affiliation(s)
- T P McDonald
- School of Biochemistry and Molecular Biology, University of Leeds, Leeds LS2 9JT, UK
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Metzler DE, Metzler CM, Sauke DJ. Lipids, Membranes, and Cell Coats. Biochemistry 2001. [DOI: 10.1016/b978-012492543-4/50011-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Abstract
Sugar transporters from one group of the major facilitator superfamily of membrane transporters. A conserved common central pore structure lies at the heart of these transporters and diverse functionality is brought about by alterations to this pore or regions associated with it. Recent mutagenesis studies of sugar transporters within the framework of tenable models for the distantly related lactose permease argue that this model is a good paradigm for other members of the major facilitator superfamily.
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Affiliation(s)
- M P Barrett
- Divisions of Infection and Immunity, Institute of Biomedical and Life Sciences, University of Glasgow, Glasgow, G12 8QQ, UK.
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