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Ji W, Xu L, Sun X, Xu X, Zhang H, Luo H, Yao B, Zhang W, Su X, Huang H. Exploiting Systematic Engineering of the Expression Cassette as a Powerful Tool to Enhance Heterologous Gene Expression in Trichoderma reesei. J Agric Food Chem 2024; 72:5307-5317. [PMID: 38426871 DOI: 10.1021/acs.jafc.3c07988] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/02/2024]
Abstract
Many endeavors in expressing a heterologous gene in microbial hosts rely on simply placing the gene of interest between a selected pair of promoters and terminator. However, although the expression efficiency could be improved by engineering the host cell, how modifying the expression cassette itself systematically would affect heterologous gene expression remains largely unknown. As the promoter and terminator bear plentiful cis-elements, herein using the Aspergillus niger mannanase with high application value in animal feeds and the eukaryotic filamentous fungus workhorse Trichoderma reesei as a model gene/host, systematic engineering of an expression cassette was investigated to decipher the effect of its mutagenesis on heterologous gene expression. Modifying the promoter, signal peptide, the eukaryotic-specific Kozak sequence, and the 3'-UTR could stepwise improve extracellular mannanase production from 17 U/mL to an ultimate 471 U/mL, representing a 27.7-fold increase in expression. The strategies can be generally applied in improving the production of heterologous proteins in eukaryotic microbial hosts.
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Affiliation(s)
- Wangli Ji
- Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, No. 12 South Zhongguancun Street, Haidian District, Beijing 100081, China
| | - Li Xu
- State Key Laboratory of Animal Nutrition and Feeding, Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, No. 2 West Yuanmingyuan Road, Haidian District, Beijing 100193, China
| | - Xianhua Sun
- State Key Laboratory of Animal Nutrition and Feeding, Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, No. 2 West Yuanmingyuan Road, Haidian District, Beijing 100193, China
| | - Xinxin Xu
- Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, No. 12 South Zhongguancun Street, Haidian District, Beijing 100081, China
| | - Honglian Zhang
- State Key Laboratory of Animal Nutrition and Feeding, Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, No. 2 West Yuanmingyuan Road, Haidian District, Beijing 100193, China
| | - Huiying Luo
- State Key Laboratory of Animal Nutrition and Feeding, Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, No. 2 West Yuanmingyuan Road, Haidian District, Beijing 100193, China
| | - Bin Yao
- State Key Laboratory of Animal Nutrition and Feeding, Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, No. 2 West Yuanmingyuan Road, Haidian District, Beijing 100193, China
| | - Wei Zhang
- Biotechnology Research Institute, Chinese Academy of Agricultural Sciences, No. 12 South Zhongguancun Street, Haidian District, Beijing 100081, China
| | - Xiaoyun Su
- State Key Laboratory of Animal Nutrition and Feeding, Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, No. 2 West Yuanmingyuan Road, Haidian District, Beijing 100193, China
| | - Huoqing Huang
- State Key Laboratory of Animal Nutrition and Feeding, Institute of Animal Sciences, Chinese Academy of Agricultural Sciences, No. 2 West Yuanmingyuan Road, Haidian District, Beijing 100193, China
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Ito T, Kajita S, Fujii M, Shinohara Y. Plasmodium Parasite Malate-Quinone Oxidoreductase Functionally Complements a Yeast Deletion Mutant of Mitochondrial Malate Dehydrogenase. Microbiol Spectr 2023; 11:e0016823. [PMID: 37036365 PMCID: PMC10269487 DOI: 10.1128/spectrum.00168-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2023] [Accepted: 03/20/2023] [Indexed: 04/11/2023] Open
Abstract
The emergence of drug-resistant variants of malaria-causing Plasmodium parasites is a life-threatening problem worldwide. Investigation of the physiological function of individual parasite proteins is a prerequisite for a deeper understanding of the metabolic pathways required for parasite survival and therefore a requirement for the development of novel antimalarials. A Plasmodium membrane protein, malate-quinone oxidoreductase (MQO), is thought to contribute to the tricarboxylic acid (TCA) cycle and the electron transport chain (ETC) and is an antimalarial drug target. However, there is little information on its expression and function. Here, we investigated the function of Plasmodium falciparum MQO (PfMQO) in mitochondria using a yeast heterologous expression system. Using a yeast deletion mutant of mitochondrial malate dehydrogenase (MDH1), which is expected to be functionally similar to MQO, as a background strain, we successfully constructed PfMQO-expressing yeast. We confirmed that expression of PfMQO complemented the growth defect of the MDH1 deletion, indicating that PfMQO can adopt the metabolic role of MDH1 in energy transduction for growth in the recombinant yeast. Analysis of cell fractions confirmed that PfMQO was expressed and enriched in yeast mitochondria. By measuring MQO activity, we also confirmed that PfMQO expressed in yeast mitochondria was active. Measurement of oxygen consumption rates showed that mitochondrial respiration was driven by the TCA cycle through PfMQO. In addition, we found that MQO activity was enhanced when intact mitochondria were sonicated, indicating that the malate binding site of PfMQO is located facing the mitochondrial matrix. IMPORTANCE We constructed a model organism to study the physiological role and function of P. falciparum malate-quinone oxidoreductase (PfMQO) in a yeast expression system. PfMQO is actively expressed in yeast mitochondria and functions in place of yeast mitochondrial malate dehydrogenase, which catalyzes the oxidation of malate to oxaloacetate in the TCA cycle. The catalytic site for the oxidation of malate in PfMQO, which is a membrane-bound protein, faces into the mitochondrial matrix, not the mitochondrial inner membrane space. Our findings clearly show that PfMQO is a TCA cycle enzyme and is coupled with the ETC via ubiquinone reduction.
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Affiliation(s)
- Takeshi Ito
- Institute of Advanced Medical Sciences, Tokushima University, Tokushima, Japan
- Graduate School of Pharmaceutical Sciences, Tokushima University, Tokushima, Japan
| | - Sayaka Kajita
- Institute of Advanced Medical Sciences, Tokushima University, Tokushima, Japan
- Faculty of Pharmaceutical Sciences, Tokushima University, Tokushima, Japan
| | - Minori Fujii
- Institute of Advanced Medical Sciences, Tokushima University, Tokushima, Japan
- Faculty of Pharmaceutical Sciences, Tokushima University, Tokushima, Japan
| | - Yasuo Shinohara
- Institute of Advanced Medical Sciences, Tokushima University, Tokushima, Japan
- Graduate School of Pharmaceutical Sciences, Tokushima University, Tokushima, Japan
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Picard MAL, Leblay F, Cassan C, Willemsen A, Daron J, Bauffe F, Decourcelle M, Demange A, Bravo IG. Transcriptomic, proteomic, and functional consequences of codon usage bias in human cells during heterologous gene expression. Protein Sci 2023; 32:e4576. [PMID: 36692287 PMCID: PMC9926478 DOI: 10.1002/pro.4576] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2022] [Revised: 01/12/2023] [Accepted: 01/14/2023] [Indexed: 01/25/2023]
Abstract
Differences in codon frequency between genomes, genes, or positions along a gene, modulate transcription and translation efficiency, leading to phenotypic and functional differences. Here, we present a multiscale analysis of the effects of synonymous codon recoding during heterologous gene expression in human cells, quantifying the phenotypic consequences of codon usage bias at different molecular and cellular levels, with an emphasis on translation elongation. Six synonymous versions of an antibiotic resistance gene were generated, fused to a fluorescent reporter, and independently expressed in HEK293 cells. Multiscale phenotype was analyzed by means of quantitative transcriptome and proteome assessment, as proxies for gene expression; cellular fluorescence, as a proxy for single-cell level expression; and real-time cell proliferation in absence or presence of antibiotic, as a proxy for the cell fitness. We show that differences in codon usage bias strongly impact the molecular and cellular phenotype: (i) they result in large differences in mRNA levels and protein levels, leading to differences of over 15 times in translation efficiency; (ii) they introduce unpredicted splicing events; (iii) they lead to reproducible phenotypic heterogeneity; and (iv) they lead to a trade-off between the benefit of antibiotic resistance and the burden of heterologous expression. In human cells in culture, codon usage bias modulates gene expression by modifying mRNA availability and suitability for translation, leading to differences in protein levels and eventually eliciting functional phenotypic changes.
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Affiliation(s)
- Marion A. L. Picard
- French National Center for Scientific ResearchLaboratory MIVEGEC (CNRS, IRD, University of Montpellier)MontpellierFrance
| | - Fiona Leblay
- French National Center for Scientific ResearchLaboratory MIVEGEC (CNRS, IRD, University of Montpellier)MontpellierFrance
| | - Cécile Cassan
- French National Center for Scientific ResearchLaboratory MIVEGEC (CNRS, IRD, University of Montpellier)MontpellierFrance
| | - Anouk Willemsen
- French National Center for Scientific ResearchLaboratory MIVEGEC (CNRS, IRD, University of Montpellier)MontpellierFrance
| | - Josquin Daron
- French National Center for Scientific ResearchLaboratory MIVEGEC (CNRS, IRD, University of Montpellier)MontpellierFrance
| | - Frédérique Bauffe
- French National Center for Scientific ResearchLaboratory MIVEGEC (CNRS, IRD, University of Montpellier)MontpellierFrance
| | - Mathilde Decourcelle
- BioCampus Montpellier (University of Montpellier, CNRS, INSERM)MontpellierFrance
| | - Antonin Demange
- French National Center for Scientific ResearchLaboratory MIVEGEC (CNRS, IRD, University of Montpellier)MontpellierFrance
| | - Ignacio G. Bravo
- French National Center for Scientific ResearchLaboratory MIVEGEC (CNRS, IRD, University of Montpellier)MontpellierFrance
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Wright G, Rodriguez A, Li J, Milenkovic T, Emrich SJ, Clark PL. CHARMING: Harmonizing synonymous codon usage to replicate a desired codon usage pattern. Protein Sci 2022; 31:221-231. [PMID: 34738275 PMCID: PMC8740841 DOI: 10.1002/pro.4223] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2021] [Revised: 10/31/2021] [Accepted: 11/02/2021] [Indexed: 01/03/2023]
Abstract
There is a growing appreciation that synonymous codon usage, although historically regarded as phenotypically silent, can instead alter a wide range of mechanisms related to functional protein production, a term we use here to describe the net effect of transcription (mRNA synthesis), mRNA half-life, translation (protein synthesis) and the probability of a protein folding correctly to its active, functional structure. In particular, recent discoveries have highlighted the important role that sub-optimal codons can play in modifying co-translational protein folding. These results have drawn increased attention to the patterns of synonymous codon usage within coding sequences, particularly in light of the discovery that these patterns can be conserved across evolution for homologous proteins. Because synonymous codon usage differs between organisms, for heterologous gene expression it can be desirable to make synonymous codon substitutions to match the codon usage pattern from the original organism in the heterologous expression host. Here we present CHARMING (for Codon HARMonizING), a robust and versatile algorithm to design mRNA sequences for heterologous gene expression and other related codon harmonization tasks. CHARMING can be run as a downloadable Python script or via a web portal at http://www.codons.org.
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Affiliation(s)
- Gabriel Wright
- Department of Computer Science & EngineeringUniversity of Notre DameNotre DameIndianaUSA,Present address:
Department of Electrical Engineering and Computer ScienceMilwaukee School of EngineeringMilwaukeeWIUSA
| | - Anabel Rodriguez
- Department of Chemistry & BiochemistryUniversity of Notre DameNotre DameIndianaUSA
| | - Jun Li
- Department of Applied and Computational Mathematics & StatisticsUniversity of Notre DameNotre DameIndianaUSA
| | - Tijana Milenkovic
- Department of Computer Science & EngineeringUniversity of Notre DameNotre DameIndianaUSA
| | - Scott J. Emrich
- Department of Electrical Engineering & Computer ScienceUniversity of TennesseeKnoxvilleTennesseeUSA
| | - Patricia L. Clark
- Department of Chemistry & BiochemistryUniversity of Notre DameNotre DameIndianaUSA
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Böhringer N, Green R, Liu Y, Mettal U, Marner M, Modaresi SM, Jakob RP, Wuisan ZG, Maier T, Iinishi A, Hiller S, Lewis K, Schäberle TF. Mutasynthetic Production and Antimicrobial Characterization of Darobactin Analogs. Microbiol Spectr 2021; 9:e0153521. [PMID: 34937193 PMCID: PMC8694152 DOI: 10.1128/spectrum.01535-21] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2021] [Accepted: 11/15/2021] [Indexed: 12/15/2022] Open
Abstract
There is great need for therapeutics against multidrug-resistant, Gram-negative bacterial pathogens. Recently, darobactin A, a novel bicyclic heptapeptide that selectively kills Gram-negative bacteria by targeting the outer membrane protein BamA, was discovered. Its efficacy was proven in animal infection models of Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa, thus promoting darobactin A as a promising lead compound. Originally discovered from members of the nematode-symbiotic genus Photorhabdus, the biosynthetic gene cluster (BGC) encoding the synthesis of darobactin A can also be found in other members of the class Gammaproteobacteria. Therein, the precursor peptides DarB to -F, which differ in their core sequence from darobactin A, were identified in silico. Even though production of these analogs was not observed in the putative producer strains, we were able to generate them by mutasynthetic derivatization of a heterologous expression system. The analogs generated were isolated and tested for their bioactivity. The most potent compound, darobactin B, was used for cocrystallization with the target BamA, revealing a binding site identical to that of darobactin A. Despite its potency, darobactin B did not exhibit cytotoxicity, and it was slightly more active against Acinetobacter baumannii isolates than darobactin A. Furthermore, we evaluated the plasma protein binding of darobactin A and B, indicating their different pharmacokinetic properties. This is the first report on new members of this new antibiotic class, which is likely to expand to several promising therapeutic candidates. IMPORTANCE Therapeutic options to combat Gram-negative bacterial pathogens are dwindling with increasing antibiotic resistance. This study presents a proof of concept for the heterologous-expression approach to expand on the novel antibiotic class of darobactins and to generate analogs with different activities and pharmacokinetic properties. In combination with the structural data of the target BamA, this approach may contribute to structure-activity relationship (SAR) data to optimize inhibitors of this essential outer membrane protein of Gram-negative pathogens.
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Affiliation(s)
- Nils Böhringer
- Justus-Liebig-University Gießen, Gießen, Germany
- German Center of Infection Research (DZIF), Partner Site Gießen-Marburg-Langen, Gießen, Germany
| | - Robert Green
- Antimicrobial Discovery Center, Department of Biology, Northeastern University, Boston, Massachusetts, USA
| | - Yang Liu
- Justus-Liebig-University Gießen, Gießen, Germany
| | - Ute Mettal
- Justus-Liebig-University Gießen, Gießen, Germany
| | - Michael Marner
- Fraunhofer Institute for Molecular Biology and Applied Ecology, Branch for Bioresources, Gießen, Germany
| | | | | | | | - Timm Maier
- Biozentrum, University of Basel, Basel, Switzerland
| | - Akira Iinishi
- Antimicrobial Discovery Center, Department of Biology, Northeastern University, Boston, Massachusetts, USA
| | | | - Kim Lewis
- Antimicrobial Discovery Center, Department of Biology, Northeastern University, Boston, Massachusetts, USA
| | - Till F. Schäberle
- Justus-Liebig-University Gießen, Gießen, Germany
- German Center of Infection Research (DZIF), Partner Site Gießen-Marburg-Langen, Gießen, Germany
- Fraunhofer Institute for Molecular Biology and Applied Ecology, Branch for Bioresources, Gießen, Germany
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Akinyemi TS, Shao N, Lyu Z, Drake IJ, Liu Y, Whitman WB. Tuning Gene Expression by Phosphate in the Methanogenic Archaeon Methanococcus maripaludis. ACS Synth Biol 2021; 10:3028-3039. [PMID: 34665610 DOI: 10.1021/acssynbio.1c00322] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Methanococcus maripaludis is a rapidly growing, hydrogenotrophic, and genetically tractable methanogen with unique capabilities to convert formate and CO2 to CH4. The existence of genome-scale metabolic models and an established, robust system for both large-scale and continuous cultivation make it amenable for industrial applications. However, the lack of molecular tools for differential gene expression has hindered its application as a microbial cell factory to produce biocatalysts and biochemicals. In this study, a library of differentially regulated promoters was designed and characterized based on the pst promoter, which responds to the inorganic phosphate concentration in the growth medium. Gene expression increases by 4- to 6-fold when the medium phosphate drops to growth-limiting concentrations. Hence, this regulated system decouples growth from heterologous gene expression without the need for adding an inducer. The minimal pst promoter is identified and contains a conserved AT-rich region, a factor B recognition element, and a TATA box for phosphate-dependent regulation. Rational changes to the factor B recognition element and start codon had no significant impact on expression; however, changes to the transcription start site and the 5' untranslated region resulted in the differential protein production with regulation remaining intact. Compared to a previous expression system based upon the histone promoter, this regulated expression system resulted in significant improvements in the expression of a key methanogenic enzyme complex, methyl-coenzyme M reductase, and the potentially toxic arginine methyltransferase MmpX.
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Affiliation(s)
- Taiwo S. Akinyemi
- Department of Microbiology, University of Georgia, Athens, Georgia 30602, United States
| | - Nana Shao
- Department of Microbiology, University of Georgia, Athens, Georgia 30602, United States
| | - Zhe Lyu
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas 77030, United States
| | - Ian J. Drake
- Corporate Strategic Research, ExxonMobil Research & Engineering Company, Annandale, New Jersey 08801, United States
| | - Yuchen Liu
- Corporate Strategic Research, ExxonMobil Research & Engineering Company, Annandale, New Jersey 08801, United States
| | - William B. Whitman
- Department of Microbiology, University of Georgia, Athens, Georgia 30602, United States
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7
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Nezhdanova AV, Slugina MA, Dyachenko EA, Kamionskaya AM, Kochieva EZ, Shchennikova AV. Analysis of the structure and function of the tomato Solanum lycopersicum L. MADS-box gene SlMADS5. Vavilovskii Zhurnal Genet Selektsii 2021; 25:492-501. [PMID: 34595372 PMCID: PMC8453369 DOI: 10.18699/vj21.056] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2021] [Revised: 05/12/2021] [Accepted: 05/18/2021] [Indexed: 12/01/2022] Open
Abstract
At all stages of f lowering, a decisive role is played by the family of MADS-domain transcription factors,
the combinatorial action of which is described by the ABCDE-model of f lower development. The current volume of
data suggests a high conservatism of ABCDE genes in angiosperms. The E-proteins SEPALLATA are the central hub of
the MADS-complexes, which determine the identity of the f loral organs. The only representative of the SEPALLATA3
clade in tomato Solanum lycopersicum L., SlMADS5, is involved in determining the identity of petals, stamens, and
carpels; however, data on the functions of the gene are limited. The study was focused on the SlMADS5 functional
characterization. Structural and phylogenetic analyses of SlMADS5 conf irmed its belonging to the SEP3 clade. An
in silico expression analysis revealed the absence of gene transcripts in roots, leaves, and shoot apical meristem,
and their presence in f lowers, fruits, and seeds at different stages of development. Two-hybrid analysis showed
the ability of SlMADS5 to activate transcription of the target gene and interact with TAGL1. Transgenic plants Nicotiana
tabacum L. with constitutive overexpression of SlMADS5 cDNA f lowered 2.2 times later than the control; plants
formed thickened leaves, 2.5–3.0 times thicker stems, 1.5–2.7 times shortened internodes, and 1.9 times fewer
f lowers and capsules than non-transgenic plants. The f lower structure did not differ from the control; however, the
corolla petals changed color from light pink to magenta. Analysis of the expression of SlMADS5 and the tobacco
genes NtLFY, NtAP1, NtWUS, NtAG, NtPLE, NtSEP1, NtSEP2, and NtSEP3 in leaves and apexes of transgenic and control
plants showed that SlMADS5 mRNA is present only in tissues of transgenic lines. The other genes analyzed were
highly expressed in the reproductive meristem of control plants. Gene transcripts were absent or were imperceptibly
present in the leaves and vegetative apex of the control, as well as in the leaves and apexes of transgenic lines.
The results obtained indicate the possible involvement of SlMADS5 in the regulation of f lower meristem development
and the pathway of anthocyanin biosynthesis in petals.
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Affiliation(s)
- A V Nezhdanova
- Institute of Bioengineering, Federal Research Centre "Fundamentals of Biotechnology" of the Russian Academy of Sciences, Moscow, Russia
| | - M A Slugina
- Institute of Bioengineering, Federal Research Centre "Fundamentals of Biotechnology" of the Russian Academy of Sciences, Moscow, Russia
| | - E A Dyachenko
- Institute of Bioengineering, Federal Research Centre "Fundamentals of Biotechnology" of the Russian Academy of Sciences, Moscow, Russia
| | - A M Kamionskaya
- Institute of Bioengineering, Federal Research Centre "Fundamentals of Biotechnology" of the Russian Academy of Sciences, Moscow, Russia
| | - E Z Kochieva
- Institute of Bioengineering, Federal Research Centre "Fundamentals of Biotechnology" of the Russian Academy of Sciences, Moscow, Russia
| | - A V Shchennikova
- Institute of Bioengineering, Federal Research Centre "Fundamentals of Biotechnology" of the Russian Academy of Sciences, Moscow, Russia
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8
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Hu L, Guo S, Yan X, Zhang T, Xiang J, Fei Q. Exploration of an Efficient Electroporation System for Heterologous Gene Expression in the Genome of Methanotroph. Front Microbiol 2021; 12:717033. [PMID: 34421878 PMCID: PMC8373458 DOI: 10.3389/fmicb.2021.717033] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2021] [Accepted: 07/07/2021] [Indexed: 11/20/2022] Open
Abstract
One-carbon (C1) substrates such as methane and methanol have been considered as the next-generation carbon source in industrial biotechnology with the characteristics of low cost, availability, and bioconvertibility. Recently, methanotrophic bacteria naturally capable of converting C1 substrates have drawn attractive attention for their promising applications in C1-based biomanufacturing for the production of chemicals or fuels. Although genetic tools have been explored for metabolically engineered methanotroph construction, there is still a lack of efficient methods for heterologous gene expression in methanotrophs. Here, a rapid and efficient electroporation method with a high transformation efficiency was developed for a robust methanotroph of Methylomicrobium buryatense 5GB1. Based on the homologous recombination and high transformation efficiency, gene deletion and heterologous gene expression can be simultaneously achieved by direct electroporation of PCR-generated linear DNA fragments. In this study, the influence of several key parameters (competent cell preparation, electroporation condition, recovery time, and antibiotic concentration) on the transformation efficiency was investigated for optimum conditions. The maximum electroporation efficiency of 719 ± 22.5 CFU/μg DNA was reached, which presents a 10-fold improvement. By employing this method, an engineered M. buryatense 5GB1 was constructed to biosynthesize isobutyraldehyde by replacing an endogenous fadE gene in the genome with a heterologous kivd gene. This study provides a potential and efficient strategy and method to facilitate the cell factory construction of methanotrophs.
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Affiliation(s)
- Lizhen Hu
- School of Chemical Engineering and Technology, Xi'an Jiaotong University, Xi'an, China
| | - Shuqi Guo
- School of Chemical Engineering and Technology, Xi'an Jiaotong University, Xi'an, China
| | - Xin Yan
- Key Laboratory of Agricultural Environmental Microbiology, Ministry of Agriculture, College of Life Sciences, Nanjing Agricultural University, Nanjing, China
| | - Tianqing Zhang
- School of Chemical Engineering and Technology, Xi'an Jiaotong University, Xi'an, China
| | - Jing Xiang
- School of Chemical Engineering and Technology, Xi'an Jiaotong University, Xi'an, China
| | - Qiang Fei
- School of Chemical Engineering and Technology, Xi'an Jiaotong University, Xi'an, China.,Shaanxi Key Laboratory of Energy Chemical Process Intensification, Xi'an Jiaotong University, Xi'an, China
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Ökmen B, Schwammbach D, Bakkeren G, Neumann U, Doehlemann G. The Ustilago hordei-Barley Interaction Is a Versatile System for Characterization of Fungal Effectors. J Fungi (Basel) 2021; 7:86. [PMID: 33513785 PMCID: PMC7912019 DOI: 10.3390/jof7020086] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2020] [Revised: 01/19/2021] [Accepted: 01/22/2021] [Indexed: 12/02/2022] Open
Abstract
Obligate biotrophic fungal pathogens, such as Blumeria graminis and Puccinia graminis, are amongst the most devastating plant pathogens, causing dramatic yield losses in many economically important crops worldwide. However, a lack of reliable tools for the efficient genetic transformation has hampered studies into the molecular basis of their virulence or pathogenicity. In this study, we present the Ustilago hordei-barley pathosystem as a model to characterize effectors from different plant pathogenic fungi. We generate U. hordei solopathogenic strains, which form infectious filaments without the presence of a compatible mating partner. Solopathogenic strains are suitable for heterologous expression system for fungal virulence factors. A highly efficient Crispr/Cas9 gene editing system is made available for U. hordei. In addition, U. hordei infection structures during barley colonization are analyzed using transmission electron microscopy, showing that U. hordei forms intracellular infection structures sharing high similarity to haustoria formed by obligate rust and powdery mildew fungi. Thus, U. hordei has high potential as a fungal expression platform for functional studies of heterologous effector proteins in barley.
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Affiliation(s)
- Bilal Ökmen
- BioCenter, Institute for Plant Sciences, University of Cologne, Zülpicher Straße 47a, 50674 Cologne, Germany
| | - Daniela Schwammbach
- Max Planck Institute for Terrestrial Microbiology, Karl von Frisch Straße, 35043 Marburg, Germany;
| | - Guus Bakkeren
- Summerland Research and Development Centre, Agriculture and Agri-Food Canada, Summerland, BC V0H 1Z0, Canada;
| | - Ulla Neumann
- Central Microscopy, Max Planck Institute for Plant Breeding Research, Carl-von-Linné-Weg 10, 50829 Cologne, Germany;
| | - Gunther Doehlemann
- BioCenter, Institute for Plant Sciences, University of Cologne, Zülpicher Straße 47a, 50674 Cologne, Germany
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10
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Nakajima KI, Guevara-Plunkett S, Chuang F, Wang KH, Lyu Y, Kumar A, Luxardi G, Izumiya C, Soulika A, Campbell M, Izumiya Y. Rainbow Kaposi's Sarcoma-Associated Herpesvirus Revealed Heterogenic Replication with Dynamic Gene Expression. J Virol 2020; 94:e01565-19. [PMID: 31969436 DOI: 10.1128/JVI.01565-19] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2019] [Accepted: 01/02/2020] [Indexed: 12/25/2022] Open
Abstract
Molecular mechanisms of Kaposi's sarcoma-associated herpesvirus (KSHV) reactivation have been studied primarily by measuring the total or average activity of an infected cell population, which often consists of a mixture of both nonresponding and reactivating cells that in turn contain KSHVs at various stages of replication. Studies on KSHV gene regulation at the individual cell level would allow us to better understand the basis for this heterogeneity, and new preventive measures could be developed based on findings from nonresponding cells exposed to reactivation stimuli. Here, we generated a recombinant reporter virus, which we named "Rainbow-KSHV," that encodes three fluorescence-tagged KSHV proteins (mBFP2-ORF6, mCardinal-ORF52, and mCherry-LANA). Rainbow-KSHV replicated similarly to a prototype reporter-KSHV, KSHVr.219, and wild-type BAC16 virus. Live imaging revealed unsynchronized initiation of reactivation and KSHV replication with diverse kinetics between individual cells. Cell fractionation revealed temporal gene regulation, in which early lytic gene expression was terminated in late protein-expressing cells. Finally, isolation of fluorescence-positive cells from nonresponders increased dynamic ranges of downstream experiments 10-fold. Thus, this study demonstrates a tool to examine heterogenic responses of KSHV reactivation for a deeper understanding of KSHV replication.IMPORTANCE Sensitivity and resolution of molecular analysis are often compromised by the use of techniques that measure the ensemble average of large cell populations. Having a research tool to nondestructively identify the KSHV replication stage in an infected cell would not only allow us to effectively isolate cells of interest from cell populations but also enable more precise sample selection for advanced single-cell analysis. We prepared a recombinant KSHV that can report on its replication stage in host cells by differential fluorescence emission. Consistent with previous host gene expression studies, our experiments reveal the highly heterogenic nature of KSHV replication/gene expression at individual cell levels. The utilization of a newly developed reporter-KSHV and initial characterization of KSHV replication in single cells are presented.
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Brady JR, Whittaker CA, Tan MC, Kristensen DL, Ma D, Dalvie NC, Love KR, Love JC. Comparative genome-scale analysis of Pichia pastoris variants informs selection of an optimal base strain. Biotechnol Bioeng 2020; 117:543-555. [PMID: 31654411 PMCID: PMC7003935 DOI: 10.1002/bit.27209] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2019] [Revised: 10/04/2019] [Accepted: 10/22/2019] [Indexed: 01/08/2023]
Abstract
Komagataella phaffii, also known as Pichia pastoris, is a common host for the production of biologics and enzymes, due to fast growth, high productivity, and advancements in host engineering. Several K. phaffii variants are commonly used as interchangeable base strains, which confounds efforts to improve this host. In this study, genomic and transcriptomic analyses of Y-11430 (CBS7435), GS115, X-33, and eight other variants enabled a comparative assessment of the relative fitness of these hosts for recombinant protein expression. Cell wall integrity explained the majority of the variation among strains, impacting transformation efficiency, growth, methanol metabolism, and secretion of heterologous proteins. Y-11430 exhibited the highest activity of genes involved in methanol utilization, up to two-fold higher transcription of heterologous genes, and robust growth. With a more permeable cell wall, X-33 displayed a six-fold higher transformation efficiency and up to 1.2-fold higher titers than Y-11430. X-33 also shared nearly all mutations, and a defective variant of HIS4, with GS115, precluding robust growth. Transferring two beneficial mutations identified in X-33 into Y-11430 resulted in an optimized base strain that provided up to four-fold higher transformation efficiency and three-fold higher protein titers, while retaining robust growth. The approach employed here to assess unique banked variants in a species and then transfer key beneficial variants into a base strain should also facilitate rational assessment of a broad set of other recombinant hosts.
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Affiliation(s)
- Joseph R. Brady
- Koch Institute for Integrative Cancer ResearchMassachusetts Institute of TechnologyCambridgeMassachusetts
- Department of Chemical EngineeringMassachusetts Institute of TechnologyCambridgeMassachusetts
| | - Charles A. Whittaker
- Koch Institute for Integrative Cancer ResearchMassachusetts Institute of TechnologyCambridgeMassachusetts
| | - Melody C. Tan
- Koch Institute for Integrative Cancer ResearchMassachusetts Institute of TechnologyCambridgeMassachusetts
| | - D. Lee Kristensen
- Koch Institute for Integrative Cancer ResearchMassachusetts Institute of TechnologyCambridgeMassachusetts
| | - Duanduan Ma
- Koch Institute for Integrative Cancer ResearchMassachusetts Institute of TechnologyCambridgeMassachusetts
| | - Neil C. Dalvie
- Koch Institute for Integrative Cancer ResearchMassachusetts Institute of TechnologyCambridgeMassachusetts
- Department of Chemical EngineeringMassachusetts Institute of TechnologyCambridgeMassachusetts
| | - Kerry Routenberg Love
- Koch Institute for Integrative Cancer ResearchMassachusetts Institute of TechnologyCambridgeMassachusetts
| | - J. Christopher Love
- Koch Institute for Integrative Cancer ResearchMassachusetts Institute of TechnologyCambridgeMassachusetts
- Department of Chemical EngineeringMassachusetts Institute of TechnologyCambridgeMassachusetts
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Volkova E, Tsetsarkin KA, Sippert E, Assis F, Liu G, Rios M, Pletnev AG. Novel Approach for Insertion of Heterologous Sequences into Full-Length ZIKV Genome Results in Superior Level of Gene Expression and Insert Stability. Viruses 2020; 12:E61. [PMID: 31947825 DOI: 10.3390/v12010061] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2019] [Revised: 12/27/2019] [Accepted: 12/31/2019] [Indexed: 12/15/2022] Open
Abstract
Zika virus (ZIKV) emerged in the Americas in 2015, presenting unique challenges to public health. Unlike other arboviruses of the Flaviviridae family, it is transmissible by sexual contact, which facilitates the spread of the virus into new geographic areas. Additionally, ZIKV can be transmitted from mother to fetus, causing microcephaly and other severe developmental abnormalities. Reliable and easy-to-work-with clones of ZIKV expressing heterologous genes will significantly facilitate studies aimed at understanding the virus pathogenesis and tissue tropism. Here, we developed and characterized two novel approaches for expression of heterologous genes of interest in the context of full-length ZIKV genome and compared them to two previously published strategies for ZIKV-mediated gene expression. We demonstrated that among the four tested viruses expressing nLuc gene, the virus constructed using a newly developed approach of partial capsid gene duplication (PCGD) attained the highest titer in Vero cells and resulted in the highest level of nLuc expression. Suitability of the PCGD approach for expression of different genes of interest was validated by replacing nLuc sequence with that of eGFP gene. The generated constructs were further characterized in cell culture. Potential applications of ZIKV clones stably expressing heterologous genes include development of detection assays, antivirals, therapeutics, live imaging systems, and vaccines.
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Martínez-Espinosa RM. Heterologous and Homologous Expression of Proteins from Haloarchaea: Denitrification as Case of Study. Int J Mol Sci 2019; 21:E82. [PMID: 31877629 PMCID: PMC6981372 DOI: 10.3390/ijms21010082] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2019] [Revised: 12/05/2019] [Accepted: 12/18/2019] [Indexed: 12/23/2022] Open
Abstract
Haloarchaea (halophilic microbes belonging to the Archaea domain) are microorganisms requiring mid or even high salt concentrations to be alive. The molecular machinery of these organisms is adapted to such conditions, which are stressful for most life forms. Among their molecular adaptations, halophilic proteins are characterized by their high content of acidic amino acids (Aspartate (Asp) and glumate (Glu)), being only stable in solutions containing high salt concentration (between 1 and 4 M total salt concentration). Recent knowledge about haloarchaeal peptides, proteins, and enzymes have revealed that many haloarchaeal species produce proteins of interest due to their potential applications in biotechnology-based industries. Although proteins of interest are usually overproduced in recombinant prokaryotic or eukaryotic expression systems, these procedures do not accurately work for halophilic proteins, mainly if such proteins contain metallocofactors in their structures. This work summarizes the main challenges of heterologous and homologous expression of enzymes from haloarchaea, paying special attention to the metalloenzymes involved in the pathway of denitrification (anaerobic reduction of nitrate to dinitrogen), a pathway with significant implications in wastewater treatment, climate change, and biosensor design.
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Affiliation(s)
- Rosa María Martínez-Espinosa
- Biochemistry and Molecular Biology Division, Agrochemistry and Biochemistry Department, Faculty of Sciences and Multidisciplinary Institute for Environmental Studies (IMEM), University of Alicante, Ap. 99, E-03080 Alicante, Spain
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Candelori A, Yamamoto TG, Iwamoto M, Montani M, Amici A, Vallesi A. Subcellular Targeting of the Euplotes raikovi Kinase Er-MAPK1, as Revealed by Expression in Different Cell Systems. Front Cell Dev Biol 2019; 7:244. [PMID: 31681773 PMCID: PMC6811501 DOI: 10.3389/fcell.2019.00244] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2019] [Accepted: 10/04/2019] [Indexed: 11/13/2022] Open
Abstract
In the ciliate Euplotes raikovi, a 631-amino acid Er-MAPK1 protein kinase was found to localize in nucleoli of the transcriptionally active nucleus (macronucleus) and act as a key component of an autocrine, cell-growth promoting self-signaling mechanism. While its 283-amino acid N-terminal domain includes all the structural specificities of the mitogen-activated protein kinases required for a catalytic function, the 348-amino acid C-terminal domain is structurally unique with undetermined functions. By expressing the two Er-MAPK1 domains tagged with the green fluorescent protein in mammalian fibroblasts, the yeast Schizosaccharomyces pombe and the ciliate Tetrahymena thermophila, evidence was obtained that the C-terminal domain contains all the sequence information responsible for the Er-MAPK1 subcellular localization. However, in fibroblasts and S. pombe this information determined a nucleolar localization of the GFP-tagged C-terminal domain, and a ciliary localization in T. thermophila. In the light of these findings, the Er-MAPK1 localization in E. raikovi was re-examined via immunoreactions and shown to be ciliary besides that nuclear, as is the case for the mammalian intestinal cell kinase with which the Er-MAPK1 N-terminal domain shares a strong sequence identity and a catalytic function.
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Affiliation(s)
- Annalisa Candelori
- School of Biosciences and Veterinary Medicine, University of Camerino, Camerino, Italy
| | - Takaharu G Yamamoto
- Advanced ICT Research Institute, National Institute of Information and Communications Technology, Kobe, Japan
| | - Masaaki Iwamoto
- Advanced ICT Research Institute, National Institute of Information and Communications Technology, Kobe, Japan
| | - Maura Montani
- School of Biosciences and Veterinary Medicine, University of Camerino, Camerino, Italy
| | - Augusto Amici
- School of Biosciences and Veterinary Medicine, University of Camerino, Camerino, Italy
| | - Adriana Vallesi
- School of Biosciences and Veterinary Medicine, University of Camerino, Camerino, Italy
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15
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Zalis EA, Nuxoll AS, Manuse S, Clair G, Radlinski LC, Conlon BP, Adkins J, Lewis K. Stochastic Variation in Expression of the Tricarboxylic Acid Cycle Produces Persister Cells. mBio 2019; 10:e01930-19. [PMID: 31530676 PMCID: PMC6751062 DOI: 10.1128/mbio.01930-19] [Citation(s) in RCA: 69] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2019] [Accepted: 08/05/2019] [Indexed: 02/07/2023] Open
Abstract
Chronic bacterial infections are difficult to eradicate, though they are caused primarily by drug-susceptible pathogens. Antibiotic-tolerant persisters largely account for this paradox. In spite of their significance in the recalcitrance of chronic infections, the mechanism of persister formation is poorly understood. We previously reported that a decrease in ATP levels leads to drug tolerance in Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus We reasoned that stochastic fluctuation in the expression of tricarboxylic acid (TCA) cycle enzymes can produce cells with low energy levels. S. aureus knockouts in glutamate dehydrogenase, 2-oxoketoglutarate dehydrogenase, succinyl coenzyme A (CoA) synthetase, and fumarase have low ATP levels and exhibit increased tolerance of fluoroquinolone, aminoglycoside, and β-lactam antibiotics. Fluorescence-activated cell sorter (FACS) analysis of TCA genes shows a broad Gaussian distribution in a population, with differences of over 3 orders of magnitude in the levels of expression between individual cells. Sorted cells with low levels of TCA enzyme expression have an increased tolerance of antibiotic treatment. These findings suggest that fluctuations in the levels of expression of energy-generating components serve as a mechanism of persister formation.IMPORTANCE Persister cells are rare phenotypic variants that are able to survive antibiotic treatment. Unlike resistant bacteria, which have specific mechanisms to prevent antibiotics from binding to their targets, persisters evade antibiotic killing by entering a tolerant nongrowing state. Persisters have been implicated in chronic infections in multiple species, and growing evidence suggests that persister cells are responsible for many cases of antibiotic treatment failure. New antibiotic treatment strategies aim to kill tolerant persister cells more effectively, but the mechanism of tolerance has remained unclear until now.
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Affiliation(s)
- Eliza A Zalis
- Department of Biology, Antimicrobial Discovery Center, Northeastern University, Boston, Massachusetts, USA
| | - Austin S Nuxoll
- Department of Biology, Antimicrobial Discovery Center, Northeastern University, Boston, Massachusetts, USA
| | - Sylvie Manuse
- Department of Biology, Antimicrobial Discovery Center, Northeastern University, Boston, Massachusetts, USA
| | - Geremy Clair
- Biological Sciences, Pacific Northwest National Laboratory, Richland, Washington, USA
| | - Lauren C Radlinski
- Department of Microbiology and Immunology, University of North Carolina School of Medicine, Chapel Hill, North Carolina, USA
| | - Brian P Conlon
- Department of Microbiology and Immunology, University of North Carolina School of Medicine, Chapel Hill, North Carolina, USA
| | - Joshua Adkins
- Biological Sciences, Pacific Northwest National Laboratory, Richland, Washington, USA
| | - Kim Lewis
- Department of Biology, Antimicrobial Discovery Center, Northeastern University, Boston, Massachusetts, USA
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16
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Abstract
Microbiologists often express foreign proteins in bacteria in order study them or to use bacteria as a microbial factory. Usually, this requires controlling the number of foreign proteins expressed in each cell, but for many common protein expression systems, it is difficult to “tune” protein expression without large cell-to-cell variation in expression levels (called “noise” in protein expression). This work describes two protein expression systems that can be combined in the same cell, with tunable expression levels and very low protein expression noise. One new system was used to detect single mRNA molecules by fluorescence microscopy, and the two systems were shown to be independent of each other. These protein expression systems may be useful in any experiment or biotechnology application that can be improved with low protein expression noise. Some microbiology experiments and biotechnology applications can be improved if it is possible to tune the expression of two different genes at the same time with cell-to-cell variation at or below the level of genes constitutively expressed from the chromosome (the “extrinsic noise limit”). This was recently achieved for a single gene by exploiting negative autoregulation by the tetracycline repressor (TetR) and bicistronic gene expression to reduce gene expression noise. We report new plasmids that use the same principles to achieve simultaneous, low-noise expression for two genes in Escherichia coli. The TetR system was moved to a compatible plasmid backbone, and a system based on the lac repressor (LacI) was found to also exhibit gene expression noise below the extrinsic noise limit. We characterized gene expression mean and noise across the range of induction levels for these plasmids, applied the LacI system to tune expression for single-molecule mRNA detection under two different growth conditions, and showed that two plasmids can be cotransformed to independently tune expression of two different genes. IMPORTANCE Microbiologists often express foreign proteins in bacteria in order study them or to use bacteria as a microbial factory. Usually, this requires controlling the number of foreign proteins expressed in each cell, but for many common protein expression systems, it is difficult to “tune” protein expression without large cell-to-cell variation in expression levels (called “noise” in protein expression). This work describes two protein expression systems that can be combined in the same cell, with tunable expression levels and very low protein expression noise. One new system was used to detect single mRNA molecules by fluorescence microscopy, and the two systems were shown to be independent of each other. These protein expression systems may be useful in any experiment or biotechnology application that can be improved with low protein expression noise.
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17
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Thinbanmai T, Lulitanond V, Mayo B, Lulitanond A, Panya M. Cloning and expression of enterovirus 71 capsid protein 1 in a probiotic Bifidobacterium pseudocatenulatum. Lett Appl Microbiol 2018; 68:9-16. [PMID: 30357884 DOI: 10.1111/lam.13089] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2018] [Revised: 10/03/2018] [Accepted: 10/03/2018] [Indexed: 12/19/2022]
Abstract
This study investigated cloning and expression of enterovirus 71 viral capsid protein 1 (EV71-VP1) in Bifidobacterium pseudocatenulatum (B. pseudocatenulatum) M115. To achieve this, a codon-optimized gene coding for EV71-VP1 was analysed, designed, synthesized and cloned into a plasmid vector flanked by a transcriptional promoter and terminator sequences. The promoter was based on that of P919, a constitutive promoter of the gene encoding the large ribosomal protein of B. bifidum BGN4, while the terminator was based on that of the peptidase N gene of Lactococcus lactis. The construct was amplified in Escherichia coli XL1-blue and then transferred into B. pseudocatenulatum M115 by electrotransformation. Western blot analysis revealed that the EV71-VP1 was intracellularly expressed in B. pseudocatenulatum M115 under the control of the selected heterologous promoter. In addition, plasmid stability analysis showed the construct was maintained stably for more than 160 generations, enough for most future applications. The results derived from this study open the possibility to utilize the bacterium carrying a specific expression plasmid as cell factory for the production of proteins with high commercial and health-promoting value. SIGNIFICANCE AND IMPACT OF THE STUDY: This study demonstrated the first successful expression of a codon-optimized gene coding for enterovirus 71 viral capsid protein 1 (EV71-VP1) in Bifidobacterium pseudocatenulatum M115, a novel probiotic strain isolated from human intestines. The EV71-VP1 was constitutively expressed under the control of P919 promoter derived from B. bifidum BGN4 in the cytoplasm of bacterial cells supporting the use of heterologous promoter and terminator sequences for viral gene expression in Bifidobacterium species.
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Affiliation(s)
- T Thinbanmai
- Department of Microbiology and Research and Diagnostic Center for Emerging Infectious Diseases, Faculty of Medicine, Khon Kaen University, Khon Kaen, Thailand
| | - V Lulitanond
- Department of Microbiology and Research and Diagnostic Center for Emerging Infectious Diseases, Faculty of Medicine, Khon Kaen University, Khon Kaen, Thailand
| | - B Mayo
- Departamento de Microbiología y Bioquímica, Instituto de Productos Lácteos de Asturias (IPLA-CSIC), Villaviciosa, Spain
| | - A Lulitanond
- Department of Clinical Microbiology, Faculty of Associated Medical Sciences, Khon Kaen University, Khon Kaen, Thailand
| | - M Panya
- College of Medicine and Public Health, Ubon Ratchathani University, Ubon Ratchathani, Thailand
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McCarl V, Somerville MV, Ly MA, Henry R, Liew EF, Wilson NL, Holmes AJ, Coleman NV. Heterologous Expression of Mycobacterium Alkene Monooxygenases in Gram-Positive and Gram-Negative Bacterial Hosts. Appl Environ Microbiol 2018; 84:e00397-18. [PMID: 29802186 PMCID: PMC6052275 DOI: 10.1128/aem.00397-18] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2018] [Accepted: 05/15/2018] [Indexed: 01/01/2023] Open
Abstract
Alkene monooxygenases (MOs) are soluble di-iron-containing enzymes found in bacteria that grow on alkenes. Here, we report improved heterologous expression systems for the propene MO (PmoABCD) and ethene MO (EtnABCD) from Mycobacterium chubuense strain NBB4. Strong functional expression of PmoABCD and EtnABCD was achieved in Mycobacterium smegmatis mc2155, yielding epoxidation activities (62 and 27 nmol/min/mg protein, respectively) higher than any reported to date for heterologous expression of a di-iron MO system. Both PmoABCD and EtnABCD were specialized for the oxidation of gaseous alkenes (C2 to C4), and their activity was much lower on liquid alkenes (C5 to C8). Despite intensive efforts to express the complete EtnABCD enzyme in Escherichia coli, this was not achieved, although recombinant EtnB and EtnD proteins could be purified individually in soluble form. The biochemical function of EtnD as an oxidoreductase was confirmed (1.36 μmol cytochrome c reduced/min/mg protein). Cloning the EtnABCD gene cluster into Pseudomonas putida KT2440 yielded detectable epoxidation of ethene (0.5 nmol/min/mg protein), and this could be stimulated (up to 1.1 nmol/min/mg protein) by the coexpression of cpn60 chaperonins from either Mycobacterium spp. or E. coli Successful expression of the ethene MO in a Gram-negative host was validated by both whole-cell activity assays and peptide mass spectrometry of induced proteins seen on SDS-PAGE gels.IMPORTANCE Alkene MOs are of interest for their potential roles in industrial biocatalysis, most notably for the stereoselective synthesis of epoxides. Wild-type bacteria that grow on alkenes have high activities for alkene oxidation but are problematic for biocatalysis, since they tend to consume the epoxide products. Using recombinant biocatalysts is the obvious alternative, but a major bottleneck is the low activities of recombinant alkene MOs. Here, we provide new high-activity recombinant biocatalysts for alkene oxidation, and we provide insights into how to further improve these systems.
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Affiliation(s)
- Victoria McCarl
- School of Life and Environmental Sciences, University of Sydney, NSW, Australia
| | - Mark V Somerville
- School of Life and Environmental Sciences, University of Sydney, NSW, Australia
| | - Mai-Anh Ly
- School of Life and Environmental Sciences, University of Sydney, NSW, Australia
| | - Rebecca Henry
- School of Life and Environmental Sciences, University of Sydney, NSW, Australia
| | - Elissa F Liew
- School of Life and Environmental Sciences, University of Sydney, NSW, Australia
| | - Neil L Wilson
- School of Life and Environmental Sciences, University of Sydney, NSW, Australia
| | - Andrew J Holmes
- School of Life and Environmental Sciences, University of Sydney, NSW, Australia
| | - Nicholas V Coleman
- School of Life and Environmental Sciences, University of Sydney, NSW, Australia
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Salinas F, Rojas V, Delgado V, López J, Agosin E, Larrondo LF. Fungal Light-Oxygen-Voltage Domains for Optogenetic Control of Gene Expression and Flocculation in Yeast. mBio 2018; 9:e00626-18. [PMID: 30065085 DOI: 10.1128/mBio.00626-18] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Optogenetic switches permit accurate control of gene expression upon light stimulation. These synthetic switches have become a powerful tool for gene regulation, allowing modulation of customized phenotypes, overcoming the obstacles of chemical inducers, and replacing their use by an inexpensive resource: light. In this work, we implemented FUN-LOV, an optogenetic switch based on the photon-regulated interaction of WC-1 and VVD, two LOV (light-oxygen-voltage) blue-light photoreceptors from the fungus Neurospora crassa. When tested in yeast, FUN-LOV yields light-controlled gene expression with exquisite temporal resolution and a broad dynamic range of over 1,300-fold, as measured by a luciferase reporter. We also tested the FUN-LOV switch for heterologous protein expression in Saccharomyces cerevisiae, where Western blot analysis confirmed strong induction upon light stimulation, surpassing by 2.5 times the levels achieved with a classic GAL4/galactose chemical-inducible system. Additionally, we utilized FUN-LOV to control the ability of yeast cells to flocculate. Light-controlled expression of the flocculin-encoding gene FLO1, by the FUN-LOV switch, yielded flocculation in light (FIL), whereas the light-controlled expression of the corepressor TUP1 provided flocculation in darkness (FID). Altogether, the results reveal the potential of the FUN-LOV optogenetic switch to control two biotechnologically relevant phenotypes such as heterologous protein expression and flocculation, paving the road for the engineering of new yeast strains for industrial applications. Importantly, FUN-LOV’s ability to accurately manipulate gene expression, with a high temporal dynamic range, can be exploited in the analysis of diverse biological processes in various organisms. Optogenetic switches are molecular devices which allow the control of different cellular processes by light, such as gene expression, providing a versatile alternative to chemical inducers. Here, we report a novel optogenetic switch (FUN-LOV) based on the LOV domain interaction of two blue-light photoreceptors (WC-1 and VVD) from the fungus N. crassa. In yeast cells, FUN-LOV allowed tight regulation of gene expression, with low background in darkness and a highly dynamic and potent control by light. We used FUN-LOV to optogenetically manipulate, in yeast, two biotechnologically relevant phenotypes, heterologous protein expression and flocculation, resulting in strains with potential industrial applications. Importantly, FUN-LOV can be implemented in diverse biological platforms to orthogonally control a multitude of cellular processes.
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Hodge-Hanson KM, Zoino A, Downs DM. Expression of Pyridoxal 5'-Phosphate-Independent Racemases Can Reduce 2-Aminoacrylate Stress in Salmonella enterica. J Bacteriol 2018; 200:e00751-17. [PMID: 29440254 DOI: 10.1128/JB.00751-17] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2017] [Accepted: 02/09/2018] [Indexed: 11/20/2022] Open
Abstract
The RidA protein (PF01042) from Salmonella enterica is a deaminase that quenches 2-aminoacrylate (2AA) and other reactive metabolites. In the absence of RidA, 2AA accumulates, damages cellular enzymes, and compromises the metabolic network. In vitro, RidA homologs from all domains of life deaminate 2AA, and RidA proteins from plants, bacteria, yeast, and humans complement the mutant phenotype of a ridA mutant strain of S. enterica In the present study, a methanogenic archaeon, Methanococcus maripaludis S2, was used to probe alternative mechanisms to restore metabolic balance. M. maripaludis MMP0739, which is annotated as an aspartate/glutamate racemase, complemented a ridA mutant strain and reduced the intracellular 2AA burden. The aspartate/glutamate racemase YgeA from Escherichia coli or S. enterica, when provided in trans, similarly restored wild-type growth to a ridA mutant. These results uncovered a new mechanism to ameliorate metabolic stress, and they suggest that direct quenching by RidA is not the only strategy to quench 2AA.IMPORTANCE 2-Aminoacrylate is an endogenously generated reactive metabolite that can damage cellular enzymes if not directly quenched by the conserved deaminase RidA. This study used an archaeon to identify a RidA-independent mechanism to prevent metabolic stress caused by 2AA. The data suggest that a gene product annotated as an aspartate/glutamate racemase (MMP0739) produces a metabolite that can quench 2AA, expanding our understanding of strategies available to quench reactive metabolites.
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Richard S, Almeida JMGCF, Cissé OH, Luraschi A, Nielsen O, Pagni M, Hauser PM. Functional and Expression Analyses of the Pneumocystis MAT Genes Suggest Obligate Sexuality through Primary Homothallism within Host Lungs. mBio 2018; 9:e02201-17. [PMID: 29463658 DOI: 10.1128/mBio.02201-17] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Fungi of the genus Pneumocystis are obligate parasites that colonize mammals’ lungs and are host species specific. Pneumocystis jirovecii and Pneumocystis carinii infect, respectively, humans and rats. They can turn into opportunistic pathogens in immunosuppressed hosts, causing severe pneumonia. Their cell cycle is poorly known, mainly because of the absence of an established method of culture in vitro. It is thought to include both asexual and sexual phases. Comparative genomic analysis suggested that their mode of sexual reproduction is primary homothallism involving a single mating type (MAT) locus encompassing plus and minus genes (matMc, matMi, and matPi; Almeida et al., mBio 6:e02250-14, 2015). Thus, each strain would be capable of sexual reproduction alone (self-fertility). However, this is a working hypothesis derived from computational analyses that is, in addition, based on the genome sequences of single isolates. Here, we tested this hypothesis in the wet laboratory. The function of the P. jirovecii and P. carinii matMc genes was ascertained by restoration of sporulation in the corresponding mutant of fission yeast. Using PCR, we found the same single MAT locus in all P. jirovecii isolates and showed that all three MAT genes are often concomitantly expressed during pneumonia. Extensive homology searches did not identify other types of MAT transcription factors in the genomes or cis-acting motifs flanking the MAT locus that could have been involved in MAT switching or silencing. Our observations suggest that Pneumocystis sexuality through primary homothallism is obligate within host lungs to complete the cell cycle, i.e., produce asci necessary for airborne transmission to new hosts. Fungi of the genus Pneumocystis colonize the lungs of mammals. In immunosuppressed human hosts, Pneumocystis jirovecii may cause severe pneumonia that can be fatal. This disease is one of the most frequent life-threatening invasive fungal infections in humans. The analysis of the genome sequences of these uncultivable pathogens suggested that their sexual reproduction involves a single partner (self-fertilization). Here, we report laboratory experiments that support this hypothesis. The function of the three genes responsible for sexual differentiation was ascertained by the restoration of sexual reproduction in the corresponding mutant of another fungus. As predicted by self-fertilization, all P. jirovecii isolates harbored the same three genes that were often concomitantly expressed within human lungs during infection. Our observations suggest that the sexuality of these pathogens relies on the self-fertility of each isolate and is obligate within host lungs to complete the cell cycle and allow dissemination of the fungus to new hosts.
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22
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Rodriguez A, Wright G, Emrich S, Clark PL. %MinMax: A versatile tool for calculating and comparing synonymous codon usage and its impact on protein folding. Protein Sci 2017; 27:356-362. [PMID: 29090506 DOI: 10.1002/pro.3336] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2017] [Revised: 10/27/2017] [Accepted: 10/30/2017] [Indexed: 11/09/2022]
Abstract
Most amino acids can be encoded by more than one synonymous codon, but these are rarely used with equal frequency. In many coding sequences the usage patterns of rare versus common synonymous codons is nonrandom and under selection. Moreover, synonymous substitutions that alter these patterns can have a substantial impact on the folding efficiency of the encoded protein. This has ignited broad interest in exploring synonymous codon usage patterns. For many protein chemists, biophysicists and structural biologists, the primary motivation for codon analysis is identifying and preserving usage patterns most likely to impact high-yield production of functional proteins. Here we describe the core functions and new features of %MinMax, a codon usage calculator freely available as a web-based portal and downloadable script (http://www.codons.org). %MinMax evaluates the relative usage frequencies of the synonymous codons used to encode a protein sequence of interest and compares these results to a rigorous null model. Crucially, for analyzing codon usage in common host organisms %MinMax requires only the coding sequence as input; with a user-input codon frequency table, %MinMax can be used to evaluate synonymous codon usage patterns for any coding sequence from any fully sequenced genome. %MinMax makes no assumptions regarding the impact of transfer ribonucleic acid concentrations or other molecular-level interactions on translation rates, yet its output is sufficient to predict the effects of synonymous codon substitutions on cotranslational folding mechanisms. A simple calculation included within %MinMax can be used to harmonize codon usage frequencies for heterologous gene expression.
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Affiliation(s)
- Anabel Rodriguez
- Department of Chemistry & Biochemistry, University of Notre Dame, Notre Dame, Indiana, 46556
| | - Gabriel Wright
- Department of Computer Science & Engineering, University of Notre Dame, Notre Dame, Indiana, 46556
| | - Scott Emrich
- Department of Computer Science & Engineering, University of Notre Dame, Notre Dame, Indiana, 46556
| | - Patricia L Clark
- Department of Chemistry & Biochemistry, University of Notre Dame, Notre Dame, Indiana, 46556.,Department of Chemical & Biomolecular Engineering, University of Notre Dame, Notre Dame, Indiana, 46556
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23
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Abstract
Peptides that are synthesized independently of the ribosome in plants, fungi, and bacteria can have clinically relevant anticancer, antihemochromatosis, and antiviral activities, among many other. Despite their natural origin, discovering new natural products is challenging, and there is a need to expand the chemical diversity that is accessible. In this work, we created a novel, compressed synthetic pathway for the heterologous expression and diversification of nonribosomal peptides (NRPs) based on homologs of siderophore pathways from Escherichia coli and Vibrio cholerae To enhance the likelihood of successful molecule production, we established a selective pressure via the iron-chelating properties of siderophores. By supplementing cells containing our synthetic pathway with different precursors that are incorporated into the pathway independently of NRP enzymes, we generated over 20 predesigned, novel, and structurally diverse NRPs. This engineering approach, where phylogenetically related genes from different organisms are integrated and supplemented with novel precursors, should enable heterologous expression and molecular diversification of NRPs.IMPORTANCE Nonribosomal peptides (NRPs) constitute a source of bioactive molecules with potential therapeutic applications. However, discovering novel NRPs by rational engineering of biosynthetic pathways remains challenging. Here, we show that a synthetic compressed pathway in which we replaced biosynthetic genes with their ancestral homologs and orthologs enabled successful heterologous NRP expression. Polyamines added exogenously were incorporated into nascent NRPs, and molecular production was pressured by growing the host under conditions that make such NRPs beneficial for survival. This multilayered approach resulted in the assembly of over 20 distinct and novel molecules. We envision this strategy being used to enable the production of NRPs from heterologous pathways.
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Affiliation(s)
- Sara Cleto
- Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
- Synthetic Biology Center, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
| | - Timothy K Lu
- Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
- Synthetic Biology Center, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
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24
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Böhnke S, Perner M. Unraveling RubisCO Form I and Form II Regulation in an Uncultured Organism from a Deep-Sea Hydrothermal Vent via Metagenomic and Mutagenesis Studies. Front Microbiol 2017; 8:1303. [PMID: 28747908 PMCID: PMC5506194 DOI: 10.3389/fmicb.2017.01303] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2017] [Accepted: 06/28/2017] [Indexed: 12/04/2022] Open
Abstract
Ribulose-1,5-bisphosphate carboxylase/oxygenase (RubisCO) catalyzes the first major step of carbon fixation in the Calvin-Benson-Bassham (CBB) cycle. This autotrophic CO2 fixation cycle accounts for almost all the assimilated carbon on Earth. Due to the primary role that RubisCO plays in autotrophic carbon fixation, it is important to understand how its gene expression is regulated and the enzyme is activated. Since the majority of all microorganisms are currently not culturable, we used a metagenomic approach to identify genes and enzymes associated with RubisCO expression. The investigated metagenomic DNA fragment originates from the deep-sea hydrothermal vent field Nibelungen at 8°18′ S along the Mid-Atlantic Ridge. It is 13,046 bp and resembles genes from Thiomicrospira crunogena. The fragment encodes nine open reading frames (ORFs) which include two types of RubisCO, form I (CbbL/S) and form II (CbbM), two LysR transcriptional regulators (LysR1 and LysR2), two von Willebrand factor type A (CbbO-m and CbbO-1), and two AAA+ ATPases (CbbQ-m and CbbQ-1), expected to function as RubisCO activating enzymes. In silico analyses uncovered several putative LysR binding sites and promoter structures. Functions of some of these DNA motifs were experimentally confirmed. For example, according to mobility shift assays LysR1’s binding ability to the intergenic region of lysR1 and cbbL appears to be intensified when CbbL or LysR2 are present. Binding of LysR2 upstream of cbbM appears to be intensified if CbbM is present. Our study suggests that CbbQ-m and CbbO-m activate CbbL and that LysR1 and LysR2 proteins promote CbbQ-m/CbbO-m expression. CbbO-1 seems to activate CbbM and CbbM itself appears to contribute to intensifying LysR’s binding ability and thus its own transcriptional regulation. CbbM furthermore appears to impair cbbL expression. A model summarizes the findings and predicts putative interactions of the different proteins influencing RubisCO gene regulation and expression.
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Affiliation(s)
- Stefanie Böhnke
- Molecular Biology of Microbial Consortia, Biocenter Klein Flottbek, University of HamburgHamburg, Germany
| | - Mirjam Perner
- Molecular Biology of Microbial Consortia, Biocenter Klein Flottbek, University of HamburgHamburg, Germany
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25
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Szatraj K, Szczepankowska AK, Chmielewska-Jeznach M. Lactic acid bacteria - promising vaccine vectors: possibilities, limitations, doubts. J Appl Microbiol 2017; 123:325-339. [PMID: 28295939 PMCID: PMC7166332 DOI: 10.1111/jam.13446] [Citation(s) in RCA: 61] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2016] [Revised: 02/16/2017] [Accepted: 03/03/2017] [Indexed: 01/18/2023]
Abstract
Gram‐positive, nonpathogenic lactic acid bacteria (LAB) are considered to be promising candidates for the development of novel, safe production and delivery systems of heterologous proteins. Recombinant LAB strains were shown to elicit specific systemic and mucosal immune responses against selected antigens. For this reason, this group of bacteria is considered as a potential replacement of classical, often pathogenic, attenuated microbial carriers. Mucosal administration of recombinant LAB, especially via the best explored and universal oral route, offers many advantages in comparison to systemic inoculation, and is attractive from the immunological and practical point of view. Research aimed at designing efficient, mucosally applied vaccines in combination with improved immunization efficiency, monitoring of in vivo antigen production, determination of optimal dose for vaccination, strain selection and characterization is a priority in modern vaccinology. This paper summarizes and organizes the available knowledge on the application of LAB as live oral vaccine vectors. It constitutes a valuable source of general information for researchers interested in mucosal vaccine development and constructing LAB strains with vaccine potential.
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Affiliation(s)
- K Szatraj
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warsaw, Poland
| | - A K Szczepankowska
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warsaw, Poland
| | - M Chmielewska-Jeznach
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Warsaw, Poland
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26
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Zhang W, Tang J, Li B, Yuan Y. [Effect of integration loci of genome on heterologous gene expression in Saccharomyces cerevisiae]. Sheng Wu Gong Cheng Xue Bao 2016; 32:901-911. [PMID: 29019212 DOI: 10.13345/j.cjb.150442] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Chromosomal integration of heterologous genes or pathways is preferred over the use of episomal plasmids for its inherently stability and thus more desirable in the industrial setting. However, the position of integration of heterologous genes in the genome influences the expression levels. In combination of high throughput transformation of the Yeast Knock-out Collection (YKO) and FACS analysis, the position effect on heterologous reporter gene gfp was identified across the whole genome in yeast. In total 428 high-expressed sites and 444 low-expressed sites were spotted, providing massive data to analyze patterns and reasons for region dependency of gene expression on the genome-wide scale.
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Affiliation(s)
- Wenzheng Zhang
- Key Laboratory of Systems Bioengineering (Ministry of Education), Tianjin University, Tianjin 300072, China.,SynBio Research Platform, Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China
| | - Jijun Tang
- SynBio Research Platform, Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China.,School of Computer Science and Technology, Tianjin University, Tianjin 300072, China
| | - Bingzhi Li
- Key Laboratory of Systems Bioengineering (Ministry of Education), Tianjin University, Tianjin 300072, China.,SynBio Research Platform, Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China
| | - Yingjin Yuan
- Key Laboratory of Systems Bioengineering (Ministry of Education), Tianjin University, Tianjin 300072, China.,SynBio Research Platform, Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), School of Chemical Engineering and Technology, Tianjin University, Tianjin 300072, China
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27
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Weninger A, Glieder A, Vogl T. A toolbox of endogenous and heterologous nuclear localization sequences for the methylotrophic yeast Pichia pastoris. FEMS Yeast Res 2015; 15:fov082. [PMID: 26347503 PMCID: PMC4629791 DOI: 10.1093/femsyr/fov082] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2015] [Accepted: 09/02/2015] [Indexed: 12/16/2022] Open
Abstract
Nuclear localization sequences (NLSs) are required for the import of proteins in the nucleus of eukaryotes. However many proteins from bacteria or bacteriophages are used for basic studies in molecular biology, to generate synthetic genetic circuits or for genome editing applications. Prokaryotic recombinases, CRISPR-associated proteins such as Cas9 or bacterial and viral polymerases require efficient NLSs to function in eukaryotes. The yeast Pichia pastoris is a widely used expression platform for heterologous protein production, but molecular tools such as NLSs are limited. Here we have characterized a set of 10 NLSs for P. pastoris, including the first endogenous NLSs (derived from P. pastoris proteins) and commonly used heterologous NLSs. The NLSs were evaluated by fusing them in N- and C-terminal position to an enhanced green fluorescent protein showing pronounced differences in fluorescence levels and nuclear targeting. Thereby we provide a set of different NLSs that can be applied to optimize the nuclear import of heterologous proteins in P. pastoris, paving the way for the establishment of intricate synthetic biology applications.
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Affiliation(s)
- Astrid Weninger
- Institute for Molecular Biotechnology, Graz University of Technology, Petersgasse 14/2, 8010 Graz, Austria
| | - Anton Glieder
- Institute for Molecular Biotechnology, Graz University of Technology, Petersgasse 14/2, 8010 Graz, Austria
| | - Thomas Vogl
- Institute for Molecular Biotechnology, Graz University of Technology, Petersgasse 14/2, 8010 Graz, Austria Queensland University of Technology, 2 George St., Brisbane QLD 4000, Australia
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28
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Ouyang S, Beecher CN, Wang K, Larive CK, Borkovich KA. Metabolic Impacts of Using Nitrogen and Copper-Regulated Promoters to Regulate Gene Expression in Neurospora crassa. G3 (Bethesda) 2015; 5:1899-908. [PMID: 26194204 DOI: 10.1534/g3.115.020073] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The filamentous fungus Neurospora crassa is a long-studied eukaryotic microbial system amenable to heterologous expression of native and foreign proteins. However, relatively few highly tunable promoters have been developed for this species. In this study, we compare the tcu-1 and nit-6 promoters for controlled expression of a GFP reporter gene in N. crassa. Although the copper-regulated tcu-1 has been previously characterized, this is the first investigation exploring nitrogen-controlled nit-6 for expression of heterologous genes in N. crassa. We determined that fragments corresponding to 1.5-kb fragments upstream of the tcu-1 and nit-6 open reading frames are needed for optimal repression and expression of GFP mRNA and protein. nit-6 was repressed using concentrations of glutamine from 2 to 20 mM and induced in medium containing 0.5–20 mM nitrate as the nitrogen source. Highest levels of expression were achieved within 3 hr of induction for each promoter and GFP mRNA could not be detected within 1 hr after transfer to repressing conditions using the nit-6 promoter. We also performed metabolic profiling experiments using proton NMR to identify changes in metabolite levels under inducing and repressing conditions for each promoter. The results demonstrate that conditions used to regulate tcu-1 do not significantly change the primary metabolome and that the differences between inducing and repressing conditions for nit-6 can be accounted for by growth under nitrate or glutamine as a nitrogen source. Our findings demonstrate that nit-6 is a tunable promoter that joins tcu-1 as a choice for regulation of gene expression in N. crassa.
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29
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Curran KA, Morse NJ, Markham KA, Wagman AM, Gupta A, Alper HS. Short Synthetic Terminators for Improved Heterologous Gene Expression in Yeast. ACS Synth Biol 2015; 4:824-32. [PMID: 25686303 DOI: 10.1021/sb5003357] [Citation(s) in RCA: 145] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Terminators play an important role both in completing the transcription process and impacting mRNA half-life. As such, terminators are an important synthetic component considered in applications such as heterologous gene expression and metabolic engineering. Here, we describe a panel of short (35-70 bp) synthetic terminators that can be used for modulating gene expression in yeast. The best of these synthetic terminator resulted in 3.7-fold more fluorescent protein output and 4.4-fold increase in transcript level compared to that with the commonly used CYC1 terminator. These synthetic terminators offer several advantages over native sequences, including an easily synthesized short length, minimal sequence homology to native sequences, and similar or better performance characteristics than those of commonly used longer terminators. Furthermore, the synthetic terminators are highly functional in both Saccharomyces cerevisiae and an alternative yeast, Yarrowia lipolytica, demonstrating that these synthetic designs are transferrable between diverse yeast species.
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Affiliation(s)
- Kathleen A. Curran
- Department
of Chemical Engineering, The University of Texas at Austin, 200
East Dean Keeton Street, Stop C0400, Austin, Texas 78712, United States
| | - Nicholas J. Morse
- Department
of Chemical Engineering, The University of Texas at Austin, 200
East Dean Keeton Street, Stop C0400, Austin, Texas 78712, United States
| | - Kelly A. Markham
- Department
of Chemical Engineering, The University of Texas at Austin, 200
East Dean Keeton Street, Stop C0400, Austin, Texas 78712, United States
| | - Allison M. Wagman
- Department
of Chemical Engineering, The University of Texas at Austin, 200
East Dean Keeton Street, Stop C0400, Austin, Texas 78712, United States
| | - Akash Gupta
- Department
of Chemical Engineering, The University of Texas at Austin, 200
East Dean Keeton Street, Stop C0400, Austin, Texas 78712, United States
| | - Hal S. Alper
- Department
of Chemical Engineering, The University of Texas at Austin, 200
East Dean Keeton Street, Stop C0400, Austin, Texas 78712, United States
- Institute
for Cellular and Molecular Biology, The University of Texas at Austin, 2500 Speedway Avenue, Austin, Texas 78712, United States
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30
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Ben-Yehezkel T, Atar S, Zur H, Diament A, Goz E, Marx T, Cohen R, Dana A, Feldman A, Shapiro E, Tuller T. Rationally designed, heterologous S. cerevisiae transcripts expose novel expression determinants. RNA Biol 2015; 12:972-84. [PMID: 26176266 PMCID: PMC4615757 DOI: 10.1080/15476286.2015.1071762] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2015] [Revised: 06/30/2015] [Accepted: 07/07/2015] [Indexed: 01/23/2023] Open
Abstract
Deducing generic causal relations between RNA transcript features and protein expression profiles from endogenous gene expression data remains a major unsolved problem in biology. The analysis of gene expression from heterologous genes contributes significantly to solving this problem, but has been heavily biased toward the study of the effect of 5' transcript regions and to prokaryotes. Here, we employ a synthetic biology driven approach that systematically differentiates the effect of different regions of the transcript on gene expression up to 240 nucleotides into the ORF. This enabled us to discover new causal effects between features in previously unexplored regions of transcripts, and gene expression in natural regimes. We rationally designed, constructed, and analyzed 383 gene variants of the viral HRSVgp04 gene ORF, with multiple synonymous mutations at key positions along the transcript in the eukaryote S. cerevisiae. Our results show that a few silent mutations at the 5'UTR can have a dramatic effect of up to 15 fold change on protein levels, and that even synonymous mutations in positions more than 120 nucleotides downstream from the ORF 5'end can modulate protein levels up to 160%-300%. We demonstrate that the correlation between protein levels and folding energy increases with the significance of the level of selection of the latter in endogenous genes, reinforcing the notion that selection for folding strength in different parts of the ORF is related to translation regulation. Our measured protein abundance correlates notably(correlation up to r = 0.62 (p=0.0013)) with mean relative codon decoding times, based on ribosomal densities (Ribo-Seq) in endogenous genes, supporting the conjecture that translation elongation and adaptation to the tRNA pool can modify protein levels in a causal/direct manner. This report provides an improved understanding of transcript evolution, design principles of gene expression regulation, and suggests simple rules for engineering synthetic gene expression in eukaryotes.
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Affiliation(s)
- Tuval Ben-Yehezkel
- Department of Biomedical Engineering; Tel-Aviv University; Tel-Aviv, Israel
- Department of Biological Chemistry; Weizmann Institute of Science; Rehovot, Israel
- Department of Applied Mathematics and Computer Science; Weizmann Institute of Science; Rehovot, Israel
- These authors equally contributed to this work.
| | - Shimshi Atar
- Department of Biomedical Engineering; Tel-Aviv University; Tel-Aviv, Israel
- These authors equally contributed to this work.
| | - Hadas Zur
- Department of Biomedical Engineering; Tel-Aviv University; Tel-Aviv, Israel
| | - Alon Diament
- Department of Biomedical Engineering; Tel-Aviv University; Tel-Aviv, Israel
| | - Eli Goz
- Department of Biomedical Engineering; Tel-Aviv University; Tel-Aviv, Israel
| | - Tzipy Marx
- Department of Biological Chemistry; Weizmann Institute of Science; Rehovot, Israel
| | - Rafael Cohen
- Department of Biological Chemistry; Weizmann Institute of Science; Rehovot, Israel
| | - Alexandra Dana
- Department of Biomedical Engineering; Tel-Aviv University; Tel-Aviv, Israel
| | - Anna Feldman
- Department of Biomedical Engineering; Tel-Aviv University; Tel-Aviv, Israel
| | - Ehud Shapiro
- Department of Biological Chemistry; Weizmann Institute of Science; Rehovot, Israel
- Department of Applied Mathematics and Computer Science; Weizmann Institute of Science; Rehovot, Israel
| | - Tamir Tuller
- Department of Biomedical Engineering; Tel-Aviv University; Tel-Aviv, Israel
- Sagol School of Neuroscience; Tel-Aviv University; Tel-Aviv, Israel
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31
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Abstract
Recent studies have shown that proximal arrangement of multiple genes can have complex effects on gene expression. For example, in the case of heterologous gene expression modules, certain arrangements of the selection marker and the gene expression cassette may have unintended consequences that limit the predictability and interpretability of module behaviors. The relationship between arrangement and expression has not been systematically characterized within heterologous modules to date. In this study, we quantitatively measured gene expression patterns of the selection marker (KlURA3 driven by the promoter, pKlURA) and the gene expression cassette (GFP driven by the galactose-inducible GAL1 promoter, pGAL1) in all their possible relative arrangements in Saccharomyces cerevisiae. First, we observed that pKlURA activity depends strongly on the relative arrangement and the activity of pGAL1. Most notably, we observed transcriptional suppression in the case of divergent arrangements: pKlURA activity was reduced when pGAL1 was inactive. Based on our nucleosome occupancy data, we attribute the observed transcriptional reduction to nucleosome repositioning. Second, we observed that pGAL1 activity also depends on the relative arrangement of pKlURA. In particular, strains with divergent promoters showed significantly different pGAL1 activation patterns from other strains, but only when their growth was compromised by lack of uracil. We reasoned that this difference in pGAL1 activation patterns arises from arrangement-dependent pKlURA activity that can affect the overall cell physiology (i.e., cell growth and survival in the uracil-depleted condition). Our results underscore the necessity to consider ramifications of promoter arrangement when using synthetic gene expression modules.
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Abstract
Tools for strain engineering with predictable outcome are of crucial importance for the nascent field of synthetic biology. The success of combining different DNA biological parts is often restricted by poorly understood factors deriving from the complexity of the systems. We have previously identified variants for different regulatory elements of the expression cassette XylS/Pm. When such elements are combined they act in a manner consistent with their individual behavior, as long as they affect different functions, such as transcription and translation. Interestingly, sequence context does not seem to influence the final outcome significantly. Expression of reporter gene bla could be increased up to 75 times at the protein level by combining three variants in one cassette. For other tested reporter genes similar results were obtained, except that the stimulatory effect was quantitatively less. Combination of individually characterized DNA parts thus stands as suitable method to achieve a desired phenotype.
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Affiliation(s)
- Friederike Zwick
- Department of Biotechnology; Norwegian University of Science and Technology; Trondheim, Norway
| | - Rahmi Lale
- Department of Biotechnology; Norwegian University of Science and Technology; Trondheim, Norway
| | - Svein Valla
- Department of Biotechnology; Norwegian University of Science and Technology; Trondheim, Norway
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33
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Fukiya S, Hirayama Y, Sakanaka M, Kano Y, Yokota A. Technological advances in bifidobacterial molecular genetics: application to functional genomics and medical treatments. Biosci Microbiota Food Health 2012; 31:15-25. [PMID: 24936345 PMCID: PMC4034290 DOI: 10.12938/bmfh.31.15] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/21/2011] [Accepted: 01/17/2012] [Indexed: 11/29/2022]
Abstract
Bifidobacteria are well known as beneficial intestinal bacteria that exert
health-promoting effects in humans. In addition to physiological and immunological
investigations, molecular genetic technologies have been developed and have recently
started to be applied to clarify the molecular bases of
host-Bifidobacterium interactions. These technologies include
transformation technologies and Escherichia coli-Bifidobacterium shuttle
vectors that enable heterologous gene expression. In this context, a plasmid artificial
modification method that protects the introduced plasmid from the restriction system in
host bifidobacteria has recently been developed to increase transformation efficiency. On
the other hand, targeted gene inactivation systems, which are vital for functional
genomics, seemed far from being practically applicable in bifidobacteria. However,
remarkable progress in this technology has recently been achieved, enabling functional
genomics in bifidobacteria. Integrated use of these molecular genetic technologies with
omics-based analyses will surely boost characterization of the molecular basis underlying
beneficial effects of bifidobacteria. Applications of recombinant bifidobacteria to
medical treatments have also progressed.
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Affiliation(s)
- Satoru Fukiya
- Laboratory of Microbial Physiology, Research Faculty of Agriculture, Hokkaido University, Kita 9 Nishi 9, Kita-ku, Sapporo, Hokkaido 060-8589, Japan
| | - Yosuke Hirayama
- Laboratory of Microbial Physiology, Research Faculty of Agriculture, Hokkaido University, Kita 9 Nishi 9, Kita-ku, Sapporo, Hokkaido 060-8589, Japan
| | - Mikiyasu Sakanaka
- Laboratory of Microbial Physiology, Research Faculty of Agriculture, Hokkaido University, Kita 9 Nishi 9, Kita-ku, Sapporo, Hokkaido 060-8589, Japan
| | - Yasunobu Kano
- Department of Molecular Genetics, Kyoto Pharmaceutical University, 5 Nakauchi-cho, Misasagi, Yamashina-ku, Kyoto 607-8414, Japan
| | - Atsushi Yokota
- Laboratory of Microbial Physiology, Research Faculty of Agriculture, Hokkaido University, Kita 9 Nishi 9, Kita-ku, Sapporo, Hokkaido 060-8589, Japan
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34
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Abstract
The sexually transmitted pathogen, Neisseria gonorrhoeae, undergoes natural transformation at high frequency. This property has led to the rapid dissemination of antibiotic resistance markers and to the panmictic structure of the gonococcal population. However, high-frequency transformation also makes N. gonorrhoeae one of the easiest bacterial species to manipulate genetically in the laboratory. Techniques have been developed that result in transformation frequencies >50%, allowing the identification of mutants by screening and without selection. Constructs have been created to take advantage of this high-frequency transformation, facilitating genetic mutation, complementation, and heterologous gene expression. Techniques are described for genetic manipulation of N. gonorrhoeae, as well as for growth of this fastidious organism.
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Affiliation(s)
- Joseph P Dillard
- Medical Microbiology and Immunology, University of Wisconsin-Madison, Madison, Wisconsin, USA
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35
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Mileni M, MacMillan F, Tziatzios C, Zwicker K, Haas A, Mäntele W, Simon J, Lancaster C. Heterologous production in Wolinella succinogenes and characterization of the quinol:fumarate reductase enzymes from Helicobacter pylori and Campylobacter jejuni. Biochem J 2006; 395:191-201. [PMID: 16367742 PMCID: PMC1409705 DOI: 10.1042/bj20051675] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2005] [Revised: 12/15/2005] [Accepted: 12/21/2005] [Indexed: 11/17/2022]
Abstract
The epsilon-proteobacteria Helicobacter pylori and Campylobacter jejuni are both human pathogens. They colonize mucosal surfaces causing severe diseases. The membrane protein complex QFR (quinol:fumarate reductase) from H. pylori has previously been established as a potential drug target, and the same is likely for the QFR from C. jejuni. In the present paper, we describe the cloning of the QFR operons from the two pathogenic bacteria H. pylori and C. jejuni and their expression in Wolinella succinogenes, a non-pathogenic -proteobacterium. To our knowledge, this is the first documentation of heterologous membrane protein production in W. succinogenes. We demonstrate that the replacement of the homologous enzyme from W. succinogenes with the heterologous enzymes yields mutants where fumarate respiration is fully functional. We have isolated and characterized the heterologous QFR enzymes. The high quality of the enzyme preparation enabled us to determine unequivocally by analytical ultracentrifugation the homodimeric state of the three detergent-solubilized heterotrimeric QFR enzymes, to accurately determine the different oxidation-reduction ('redox') midpoint potentials of the six prosthetic groups, the Michaelis constants for the quinol substrate, maximal enzymatic activities and the characterization of three different anti-helminths previously suggested to be inhibitors of the QFR enzymes from H. pylori and C. jejuni. This characterization allows, for the first time, a detailed comparison of the QFR enzymes from C. jejuni and H. pylori with that of W. succinogenes.
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Key Words
- campylobacter jejuni
- helicobacter pylori
- heterologous gene expression
- membrane protein purification
- quinol:fumarate reductase
- wolinella succinogenes
- bv, benzyl viologen
- cat, chloramphenicol acetyltransferase
- cw-epr, continuous-wave epr
- dmn, 2,3-dimethyl-1,4-naphthoquinone
- dmnh2, 2,3-dimethyl-1,4-naphthoquinol
- malt, mucosa-associated lymphoid tissue
- mb, methylene blue
- mk, menaquinone
- qfr, quinol:fumarate reductase
- sqor, succinate:quinone oxidoreductase
- sqr, succinate:quinone reductase
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Affiliation(s)
- Mauro Mileni
- *Department of Molecular Membrane Biology, Max Planck Institute of Biophysics, Max-von-Laue-Str. 3, 60438 Frankfurt am Main, Germany
| | - Fraser MacMillan
- †Institute of Physical and Theoretical Chemistry, J.W. Goethe University, Marie-Curie-Str. 11, 60439 Frankfurt am Main, Germany
| | - Christos Tziatzios
- ‡Institute of Biophysics, J.W. Goethe University, Max-von-Laue-Str. 1, 60438 Frankfurt am Main, Germany
| | - Klaus Zwicker
- §Department of Medicine, Institute of Molecular Bioenergetics, Gustav Embden Centre of Biological Chemistry, J.W. Goethe University, Theodor-Stern-Kai 7, Haus 25B, 60590 Frankfurt am Main, Germany
| | - Alexander H. Haas
- *Department of Molecular Membrane Biology, Max Planck Institute of Biophysics, Max-von-Laue-Str. 3, 60438 Frankfurt am Main, Germany
| | - Werner Mäntele
- ‡Institute of Biophysics, J.W. Goethe University, Max-von-Laue-Str. 1, 60438 Frankfurt am Main, Germany
| | - Jörg Simon
- ∥Institute of Molecular Biosciences, J.W. Goethe University, Marie-Curie-Str. 9, 60439 Frankfurt am Main, Germany
| | - C. Roy D. Lancaster
- *Department of Molecular Membrane Biology, Max Planck Institute of Biophysics, Max-von-Laue-Str. 3, 60438 Frankfurt am Main, Germany
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36
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Szafranski P, Mello CM, Sano T, Smith CL, Kaplan DL, Cantor CR. A new approach for containment of microorganisms: dual control of streptavidin expression by antisense RNA and the T7 transcription system. Proc Natl Acad Sci U S A 1997; 94:1059-63. [PMID: 9037005 PMCID: PMC19743 DOI: 10.1073/pnas.94.4.1059] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
The use of microorganisms in the open environment would be of less concern if they were endowed with programmed self-destruction mechanisms. Here, we propose a new genetic design to increase the effectiveness of cell suicide systems. It ensures very tight control of the derepression of cell death by the combination of the bacteriophage T7 RNA polymerase-lysozyme system and an inducible synthesis of antisense RNA and the Escherichia coli LacI repressor. Functionality of this regulatory concept was tested by applying it to containment of Gram-negative bacteria, based on the conditional expression of the lethal Streptomyces avidinii streptavidin gene. Toxicity of streptavidin is derived from its exceptionally high binding affinity for an essential prosthetic group, D-biotin. The entire construct was designed to allow the soil bacterium Pseudomonas putida to survive only in the presence of aromatic hydrocarbons and their derivatives which it can degrade. Under favorable growth conditions, clones escaping killing appeared at frequencies of only 10(-7)-10(-8) per cell per generation. The general requirement for biotin through the living world should make streptavidin-based conditional lethal designs applicable to a broad range of containment strategies.
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Affiliation(s)
- P Szafranski
- Department of Biomedical Engineering, Boston University, MA 02215, USA
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van Dinten LC, den Boon JA, Wassenaar AL, Spaan WJ, Snijder EJ. An infectious arterivirus cDNA clone: identification of a replicase point mutation that abolishes discontinuous mRNA transcription. Proc Natl Acad Sci U S A 1997; 94:991-6. [PMID: 9023370 PMCID: PMC19627 DOI: 10.1073/pnas.94.3.991] [Citation(s) in RCA: 169] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Equine arteritis virus (EAV) is a positive-strand RNA virus that uses a discontinuous transcription mechanism to generate a nested set of six subgenomic mRNAs from which its structural genes are expressed. A stable bacterial plasmid (pEAV030) containing a full-length cDNA copy of the 12.7-kb EAV genome was constructed. After removal of a single point mutation in the replicase gene, RNA transcripts generated in vitro from pEAV030 were shown to be infectious upon electroporation into BHK-21 cells. A genetic marker mutation was introduced at the cDNA level and recovered from the genome of the progeny virus. The potential of pEAV030 as a tool to express foreign genes was demonstrated by the efficient expression of the chloramphenicol acetyltransferase (CAT) reporter gene from two different subgenomic mRNAs. The point mutation that initially rendered the full-length clone noninfectious was found to result in a particularly intriguing phenotype: RNA carrying this mutation can replicate efficiently but does not produce the subgenomic mRNAs required for structural protein expression. To our knowledge, this mutant provides the first evidence that the requirements for arterivirus genome replication and discontinuous mRNA synthesis are, at least partially, different and that these processes may be separated experimentally.
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Affiliation(s)
- L C van Dinten
- Department of Virology, Institute of Medical Microbiology, Leiden University, The Netherlands
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