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Wang Z, Hou X, Shang G, Deng G, Luo K, Peng M. Exploring Fatty Acid β-Oxidation Pathways in Bacteria: From General Mechanisms to DSF Signaling and Pathogenicity in Xanthomonas. Curr Microbiol 2024; 81:336. [PMID: 39223428 DOI: 10.1007/s00284-024-03866-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2024] [Accepted: 08/20/2024] [Indexed: 09/04/2024]
Abstract
Fatty acids (FAs) participate in extensive physiological activities such as energy metabolism, transcriptional control, and cell signaling. In bacteria, FAs are degraded and utilized through various metabolic pathways, including β-oxidation. Over the past ten years, significant progress has been made in studying FA oxidation in bacteria, particularly in E. coli, where the processes and roles of FA β-oxidation have been comprehensively elucidated. Here, we provide an update on the new research achievements in FAs β-oxidation in bacteria. Using Xanthomonas as an example, we introduce the oxidation process and regulation mechanism of the DSF-family quorum sensing signal. Based on current findings, we propose the specific enzymes required for β-oxidation of several specific FAs. Finally, we discuss the future outlook on scientific issues that remain to be addressed. This paper supplies theoretical guidance for further study of the FA β-oxidation pathway with particular emphasis on its connection to the pathogenicity mechanisms of bacteria.
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Affiliation(s)
- Zhiyong Wang
- Hubei Engineering Research Center of Selenium Food Nutrition and Health Intelligent Technology College of Biological and Food Engineering, Hubei Minzu University, Enshi, 445000, China
| | - Xue Hou
- Hubei Engineering Research Center of Selenium Food Nutrition and Health Intelligent Technology College of Biological and Food Engineering, Hubei Minzu University, Enshi, 445000, China
| | - Guohui Shang
- Department of Medical Genetics and Cell Biology, School of Basic Medical Sciences, Zhengzhou University, Zhengzhou, 450001, China
| | - Guangai Deng
- Hubei Engineering Research Center of Selenium Food Nutrition and Health Intelligent Technology College of Biological and Food Engineering, Hubei Minzu University, Enshi, 445000, China
| | - Kai Luo
- Hubei Engineering Research Center of Selenium Food Nutrition and Health Intelligent Technology College of Biological and Food Engineering, Hubei Minzu University, Enshi, 445000, China
| | - Mu Peng
- Hubei Engineering Research Center of Selenium Food Nutrition and Health Intelligent Technology College of Biological and Food Engineering, Hubei Minzu University, Enshi, 445000, China.
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2
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Schiaffi V, Barras F, Bouveret E. Matching the β-oxidation gene repertoire with the wide diversity of fatty acids. Curr Opin Microbiol 2024; 77:102402. [PMID: 37992547 DOI: 10.1016/j.mib.2023.102402] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2023] [Revised: 10/23/2023] [Accepted: 10/28/2023] [Indexed: 11/24/2023]
Abstract
Bacteria can use fatty acids (FAs) from their environment as carbon and energy source. This catabolism is performed by the enzymes of the well-known β-oxidation machinery, producing reducing power and releasing acetyl-CoA that can feed the tricarboxylic acid cycle. FAs are extremely diverse: they can be saturated or (poly)unsaturated and are found in different sizes. The need to degrade such a wide variety of compounds may explain why so many seemingly homologous enzymes are found for each step of the β-oxidation cycle. In addition, the degradation of unsaturated fatty acids requires specific auxiliary enzymes for isomerase and reductase reactions. Furthermore, the β-oxidation cycle can be blocked by dead-end products, which are taken care of by acyl-CoA thioesterases. Yet, the functional characterization of the enzymes required for the degradation of the full diversity of FAs remains to be documented in most bacteria.
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Affiliation(s)
- Veronica Schiaffi
- Institut Pasteur, Department of Microbiology, Université Paris-Cité, UMR CNRS 6047, SAMe Unit, France
| | - Frédéric Barras
- Institut Pasteur, Department of Microbiology, Université Paris-Cité, UMR CNRS 6047, SAMe Unit, France
| | - Emmanuelle Bouveret
- Institut Pasteur, Department of Microbiology, Université Paris-Cité, UMR CNRS 6047, SAMe Unit, France.
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3
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Nawaz MZ, Xu C, Qaria MA, Zeeshan Haider S, Rameez Khalid H, Ahmed Alghamdi H, Ahmad Khan I, Zhu D. Genomic and biotechnological potential of a novel oil-degrading strain Enterobacter kobei DH7 isolated from petroleum-contaminated soil. CHEMOSPHERE 2023; 340:139815. [PMID: 37586489 DOI: 10.1016/j.chemosphere.2023.139815] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/02/2023] [Revised: 07/02/2023] [Accepted: 08/12/2023] [Indexed: 08/18/2023]
Abstract
In this study, a novel oil-degrading strain Enterobacter kobei DH7 was isolated from petroleum-contaminated soil samples from the industrial park in Taolin Town, Lianyungang, China. The whole genome of the strain was sequenced and analyzed to reveal its genomic potential. The oil degradation and growth conditions including nitrogen, and phosphorus sources, degradation cycle, biological dosing, pH, and oil concentration were optimized to exploit its commercial application. The genome of the DH7 strain contains 4,705,032 bp with GC content of 54.95% and 4653 genes. The genome analysis revealed that there are several metabolic pathways and enzyme-encoding genes related to oil degradation in the DH7 genome, such as the paa gene cluster which is involved in the phenylacetic acid degradation pathway, and complete degradation pathways for fatty acid and benzoate, genes related to chlorinated alkanes and olefins degradation pathway including adhP, frmA, and adhE, etc. The strain DH7 under the optimized conditions has demonstrated a maximum degradation efficiency of 84.6% after 14 days of treatment using synthetic oil, which comparatively displays a higher oil degradation efficiency than any Enterobacter species known to date. To the best of our knowledge, this study presents the first-ever genomic studies related to the oil degradation potential of any Enterobacter species. As Enterobacter kobei DH7 has demonstrated significant oil degradation potential, it is one of the good candidates for application in the bioremediation of oil-contaminated environments.
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Affiliation(s)
- Muhammad Zohaib Nawaz
- Biofuels Institute, School of Emergency Management, School of the Environment and Safety Engineering, Jiangsu University, Zhenjiang, 212013, China
| | - Chunyan Xu
- Biofuels Institute, School of Emergency Management, School of the Environment and Safety Engineering, Jiangsu University, Zhenjiang, 212013, China
| | - Majjid A Qaria
- Biofuels Institute, School of Emergency Management, School of the Environment and Safety Engineering, Jiangsu University, Zhenjiang, 212013, China
| | - Syed Zeeshan Haider
- Biofuels Institute, School of Emergency Management, School of the Environment and Safety Engineering, Jiangsu University, Zhenjiang, 212013, China
| | - Hafiz Rameez Khalid
- Biofuels Institute, School of Emergency Management, School of the Environment and Safety Engineering, Jiangsu University, Zhenjiang, 212013, China
| | - Huda Ahmed Alghamdi
- Department of Biology, College of Sciences, King Khalid University, Abha, 61413, Saudi Arabia
| | - Iqrar Ahmad Khan
- Center for Advanced Studies in Agriculture and Food Security, University of Agriculture, Faisalabad, 38040, Pakistan
| | - Daochen Zhu
- Biofuels Institute, School of Emergency Management, School of the Environment and Safety Engineering, Jiangsu University, Zhenjiang, 212013, China.
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RdmA Is a Key Regulator in Autoinduction of DSF Quorum Quenching in Pseudomonas nitroreducens HS-18. mBio 2023; 14:e0301022. [PMID: 36537811 PMCID: PMC9973270 DOI: 10.1128/mbio.03010-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Diffusible signal factor (DSF) represents a family of widely conserved quorum-sensing (QS) signals which regulate virulence factor production and pathogenicity in numerous Gram-negative bacterial pathogens. We recently reported the identification of a highly potent DSF-quenching bacterial isolate, Pseudomonas nitroreducens HS-18, which contains an operon with four DSF-inducible genes, digABCD, or digA-D, that are responsible for degradation of DSF signals. However, the regulatory mechanisms that govern the digA-D response to DSF induction have not yet been characterized. In this study, we identified a novel transcriptional regulator we designated RdmA (regulator of DSF metabolism) which negatively regulates the expression of digA-D and represses DSF degradation. In addition, we found that a gene cluster located adjacent to rdmA was also negatively regulated by RdmA and played a key role in DSF degradation; this cluster was hence named dmg (DSF metabolism genes). An electrophoretic mobility shift assay and genetic analysis showed that RdmA represses the transcriptional expression of the dmg genes in a direct manner. Further studies demonstrated that DSF acts as an antagonist and binds to RdmA, which abrogates RdmA binding to the target promoter and its suppression on transcriptional expression of the dmg genes. Taken together, the results from this study have unveiled a central regulator and a gene cluster associated with the autoinduction of DSF degradation in P. nitroreducens HS-18, and this will aid in the understanding of the genetic basis and regulatory mechanisms that govern the quorum-quenching activity of this potent biocontrol agent. IMPORTANCE DSF family quorum-sensing (QS) signals play important roles in regulation of bacterial physiology and virulence in a wide range of plant and human bacterial pathogens. Quorum quenching (QQ), which acts by either degrading QS signals or blocking QS communication, has proven to be a potent disease control strategy, but QQ mechanisms that target DSF family signals and associated regulatory mechanisms remain largely unknown. Recently, we identified four autoinduced DSF degradation genes (digABCD) in P. nitroreducens HS-18. By using a combination of transcriptome and genetic analysis, we identified a central regulator that plays a key role in autoinduction of dig expression, as well as a new gene cluster (dmgABCDEFGH) involved in DSF degradation. The significance of our study is in unveiling the autoinduction mechanism that governs DSF signal quorum quenching for the first time, to our knowledge, and in identification of new genes and enzymes responsible for DSF degradation. The findings from this study shed new light on our understanding of the DSF metabolism pathway and the regulatory mechanisms that modulate DSF quorum quenching and will provide useful clues for design and development of a new generation of highly potent QQ biocontrol agents against DSF-mediated bacterial infections.
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Degradation of Exogenous Fatty Acids in Escherichia coli. Biomolecules 2022; 12:biom12081019. [PMID: 35892328 PMCID: PMC9329746 DOI: 10.3390/biom12081019] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2022] [Revised: 07/19/2022] [Accepted: 07/19/2022] [Indexed: 12/10/2022] Open
Abstract
Many bacteria possess all the machineries required to grow on fatty acids (FA) as a unique source of carbon and energy. FA degradation proceeds through the β-oxidation cycle that produces acetyl-CoA and reduced NADH and FADH cofactors. In addition to all the enzymes required for β-oxidation, FA degradation also depends on sophisticated systems for its genetic regulation and for FA transport. The fact that these machineries are conserved in bacteria suggests a crucial role in environmental conditions, especially for enterobacteria. Bacteria also possess specific enzymes required for the degradation of FAs from their environment, again showing the importance of this metabolism for bacterial adaptation. In this review, we mainly describe FA degradation in the Escherichia coli model, and along the way, we highlight and discuss important aspects of this metabolism that are still unclear. We do not detail exhaustively the diversity of the machineries found in other bacteria, but we mention them if they bring additional information or enlightenment on specific aspects.
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Xu Y, Yang J, Li W, Song S, Shi Y, Wu L, Sun J, Hou M, Wang J, Jia X, Zhang H, Huang M, Lu T, Gan J, Feng Y. Three enigmatic BioH isoenzymes are programmed in the early stage of mycobacterial biotin synthesis, an attractive anti-TB drug target. PLoS Pathog 2022; 18:e1010615. [PMID: 35816546 PMCID: PMC9302846 DOI: 10.1371/journal.ppat.1010615] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2022] [Revised: 07/21/2022] [Accepted: 05/24/2022] [Indexed: 11/19/2022] Open
Abstract
Tuberculosis (TB) is one of the leading infectious diseases of global concern, and one quarter of the world’s population are TB carriers. Biotin metabolism appears to be an attractive anti-TB drug target. However, the first-stage of mycobacterial biotin synthesis is fragmentarily understood. Here we report that three evolutionarily-distinct BioH isoenzymes (BioH1 to BioH3) are programmed in biotin synthesis of Mycobacterium smegmatis. Expression of an individual bioH isoform is sufficient to allow the growth of an Escherichia coli ΔbioH mutant on the non-permissive condition lacking biotin. The enzymatic activity in vitro combined with biotin bioassay in vivo reveals that BioH2 and BioH3 are capable of removing methyl moiety from pimeloyl-ACP methyl ester to give pimeloyl-ACP, a cognate precursor for biotin synthesis. In particular, we determine the crystal structure of dimeric BioH3 at 2.27Å, featuring a unique lid domain. Apart from its catalytic triad, we also dissect the substrate recognition of BioH3 by pimeloyl-ACP methyl ester. The removal of triple bioH isoforms (ΔbioH1/2/3) renders M. smegmatis biotin auxotrophic. Along with the newly-identified Tam/BioC, the discovery of three unusual BioH isoforms defines an atypical ‘BioC-BioH(3)’ paradigm for the first-stage of mycobacterial biotin synthesis. This study solves a long-standing puzzle in mycobacterial nutritional immunity, providing an alternative anti-TB drug target.
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Affiliation(s)
- Yongchang Xu
- Departments of Microbiology, and General Intensive Care Unit of the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, The People’s Republic of China
| | - Jie Yang
- Shanghai Public Health Clinical Center, State Key Laboratory of Genetic Engineering, Collaborative Innovation Center of Genetics and Development, Department of Biochemistry and Biophysics, School of Life Science, Fudan University, Shanghai, The People’s Republic of China
| | - Weihui Li
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, College of Life Science and Technology, Guangxi University, Nanning, Guangxi, The People’s Republic of China
| | - Shuaijie Song
- Departments of Microbiology, and General Intensive Care Unit of the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, The People’s Republic of China
| | - Yu Shi
- Departments of Microbiology, and General Intensive Care Unit of the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, The People’s Republic of China
| | - Lihan Wu
- Departments of Microbiology, and General Intensive Care Unit of the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, The People’s Republic of China
| | - Jingdu Sun
- Departments of Microbiology, and General Intensive Care Unit of the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, The People’s Republic of China
- College of Animal Sciences, Zhejiang University, Hangzhou, Zhejiang, The People’s Republic of China
| | - Mengyun Hou
- Departments of Microbiology, and General Intensive Care Unit of the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, The People’s Republic of China
| | - Jinzi Wang
- Guangxi Key Laboratory of Utilization of Microbial and Botanical Resources & Guangxi Key Laboratory for Polysaccharide Materials and Modifications, School of Marine Sciences and Biotechnology, Guangxi Minzu University, Nanning, Guangxi, The People’s Republic of China
| | - Xu Jia
- Non-coding RNA and Drug Discovery Key Laboratory of Sichuan Province, Chengdu Medical College, Chengdu, Sichuan, The People’s Republic of China
| | - Huimin Zhang
- Cancer Center at Illinois, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America
| | - Man Huang
- Departments of Microbiology, and General Intensive Care Unit of the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, The People’s Republic of China
| | - Ting Lu
- Department of Bioengineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America
| | - Jianhua Gan
- Shanghai Public Health Clinical Center, State Key Laboratory of Genetic Engineering, Collaborative Innovation Center of Genetics and Development, Department of Biochemistry and Biophysics, School of Life Science, Fudan University, Shanghai, The People’s Republic of China
- * E-mail: (JG); (YF)
| | - Youjun Feng
- Departments of Microbiology, and General Intensive Care Unit of the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, The People’s Republic of China
- College of Animal Sciences, Zhejiang University, Hangzhou, Zhejiang, The People’s Republic of China
- Non-coding RNA and Drug Discovery Key Laboratory of Sichuan Province, Chengdu Medical College, Chengdu, Sichuan, The People’s Republic of China
- * E-mail: (JG); (YF)
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Jindal S, Iyer MS, Jyoti P, Masakapalli SK, Venkatesh KV. Mutants lacking global regulators, fis and arcA, in Escherichia coli enhanced growth fitness under acetate metabolism by pathway reprogramming. Appl Microbiol Biotechnol 2022; 106:3231-3243. [PMID: 35416487 DOI: 10.1007/s00253-022-11890-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2021] [Revised: 03/20/2022] [Accepted: 03/21/2022] [Indexed: 11/25/2022]
Abstract
Global regulatory transcription factors play a significant role in controlling microbial metabolism under genetic and environmental perturbations. A system-level effect of carbon sources such as acetate on microbial metabolism under disrupted global regulators has not been well established. Acetate is one of the major substrates available in various nutrient niches such as the mammalian gut and a keto diet. A substantial amount of acetate gets secreted in aerobic metabolism. Therefore, investigating the study on acetate metabolism is highly significant. It is known that the global regulators fis and arcA regulate acetate uptake genes in E. coli under glucose conditions. This study deciphered the growth and flux distribution of E. coli transcription regulatory knockouts Δfis, ΔarcA and double deletion mutant, ΔarcAΔfis under acetate using 13C-metabolic flux analysis (MFA), which has not been investigated before. We observed that the mutants exhibited an expeditious growth rate (~ 1.2-1.6-fold) with a proportionate increase in acetate uptake rates compared to the wild type. 13C-MFA displayed the distinct metabolic reprogramming of intracellular fluxes via the TCA cycle, anaplerotic pathway and gluconeogenesis, which conferred an advantage of a faster growth rate with better carbon usage in all the mutants. This resulted in higher metabolic fluxes through the TCA cycle (~ 18-90%), lower gluconeogenesis (~ 15-35%) and higher CO2 and ATP production with the proportional increase in growth rate. The study reveals a novel insight by stating the sub-optimality of the wild-type strain grown under acetate substrate aerobically. These mutant strains efficiently oxidize acetate, thus acting as potential candidates for the biosynthesis of isoprenoids, biofuels, vitamins and various pharmaceutical products.Key Points• Mutants exhibited a better balance between energy and precursor synthesis than WT.• Leveraged in the unravelling of regulatory control under various nutrient shifts.• Metabolic readjustment resulted in optimal biomass requirement and faster growth.
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Affiliation(s)
- Shikha Jindal
- Department of Chemical Engineering, Indian Institute of Technology Bombay, Powai, Mumbai, 400076, India
| | - Mahesh S Iyer
- Department of Chemical Engineering, Indian Institute of Technology Bombay, Powai, Mumbai, 400076, India
| | - Poonam Jyoti
- BioX Center, School of Basic Sciences, Indian Institute of Technology Mandi, Kamand, 175075, India
| | - Shyam Kumar Masakapalli
- BioX Center, School of Basic Sciences, Indian Institute of Technology Mandi, Kamand, 175075, India.
| | - K V Venkatesh
- Department of Chemical Engineering, Indian Institute of Technology Bombay, Powai, Mumbai, 400076, India.
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8
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Anzai T, Imamura S, Ishihama A, Shimada T. Expanded roles of pyruvate-sensing PdhR in transcription regulation of the Escherichia coli K-12 genome: fatty acid catabolism and cell motility. Microb Genom 2020; 6. [PMID: 32975502 PMCID: PMC7660256 DOI: 10.1099/mgen.0.000442] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
The transcription factor PdhR has been recognized as the master regulator of the pyruvate catabolism pathway in Escherichia coli, including both NAD-linked oxidative decarboxylation of pyruvate to acetyl-CoA by PDHc (pyruvate dehydrogenase complex) and respiratory electron transport of NADH to oxygen by Ndh-CyoABCD enzymes. To identify the whole set of regulatory targets under the control of pyruvate-sensing PdhR, we performed genomic SELEX (gSELEX) screening in vitro. A total of 35 PdhR-binding sites were identified along the E. coli K-12 genome, including previously identified targets. Possible involvement of PdhR in regulation of the newly identified target genes was analysed in detail by gel shift assay, RT-qPCR and Northern blot analysis. The results indicated the participation of PdhR in positive regulation of fatty acid degradation genes and negative regulation of cell mobility genes. In fact, GC analysis indicated an increase in free fatty acids in the mutant lacking PdhR. We propose that PdhR is a bifunctional global regulator for control of a total of 16–23 targets, including not only the genes involved in central carbon metabolism but also some genes for the surrounding pyruvate-sensing cellular pathways such as fatty acid degradation and flagella formation. The activity of PdhR is controlled by pyruvate, the key node between a wide variety of metabolic pathways, including generation of metabolic energy and cell building blocks.
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Affiliation(s)
- Takumi Anzai
- School of Agriculture, Meiji University, Kawasaki, Kanagawa, Japan
| | - Sousuke Imamura
- Laboratory for Chemistry and Life Science, Institute of Innovative Research, Tokyo Institute of Technology, Yokohama, Kanagawa, Japan
| | - Akira Ishihama
- Micro-Nanotechnology Research Center, Hosei University, Koganei, Tokyo, Japan
| | - Tomohiro Shimada
- School of Agriculture, Meiji University, Kawasaki, Kanagawa, Japan
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9
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Yang S, Xi D, Wang X, Li Y, Li Y, Yan J, Cao B. Vibrio cholerae VC1741 (PsrA) enhances the colonization of the pathogen in infant mice intestines in the presence of the long-chain fatty acid, oleic acid. Microb Pathog 2020; 147:104443. [PMID: 32777352 DOI: 10.1016/j.micpath.2020.104443] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2020] [Revised: 08/04/2020] [Accepted: 08/04/2020] [Indexed: 01/08/2023]
Abstract
Vibrio cholerae is a natural inhabitant of aquatic environments and causes the epidemic diarrheal disease known as cholera. Fatty acid metabolism is closely related to the pathogenicity of V. cholerae. The TetR family transcriptional repressor PsrA regulates the β-oxidation pathway in Pseudomonas aeruginosa; however, little is known about its regulation in V. cholerae. In this study, qRT-PCR revealed that the expression of vc1741 (psrA) increased 40-fold in the small intestines of infant mice compared with that grown in LB medium. The Δvc1741 mutant showed a significant defected in the ability to colonize the small intestines of infant mice with a competitive index (CI) of 0.53. EMSAs indicated that VC1741 could directly bind to the promoter regions of vc1741-fadE1, fadBA, and fadIJ operons, and these bindings were reversed upon addition of the long-chain fatty acid (LCFA), oleic acid. The expression levels of the fadB, fadA, fadI, and fadJ genes were all elevated by approximately 2-fold in the Δvc1741 mutant strain compared with that in the wild-type strain in LB medium, indicating that VC1741 is a repressor for these genes involved in fatty acid degradation. Moreover, ΔfadBA, ΔfadB, and ΔfadA isogenic mutants showed defective abilities to colonize the small intestines of infant mice, with CI values of 0.64, 0.73, and 0.74, respectively. These data provided a mechanistic model in which LCFAs affect the expression of VC1741 to control fatty acid degradation and virulence in V. cholerae.
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Affiliation(s)
- Shuang Yang
- TEDA Institute of Biological Sciences and Biotechnology, Nankai University, Tianjin, 300457, China; Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, Nankai University, Tianjin, 300457, China; Tianjin Key Laboratory of Microbial Functional Genomics, TEDA College, Nankai University, Tianjin, 300457, China
| | - Daoyi Xi
- TEDA Institute of Biological Sciences and Biotechnology, Nankai University, Tianjin, 300457, China; Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, Nankai University, Tianjin, 300457, China; Tianjin Key Laboratory of Microbial Functional Genomics, TEDA College, Nankai University, Tianjin, 300457, China
| | - Xiaochen Wang
- TEDA Institute of Biological Sciences and Biotechnology, Nankai University, Tianjin, 300457, China; Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, Nankai University, Tianjin, 300457, China; Tianjin Key Laboratory of Microbial Functional Genomics, TEDA College, Nankai University, Tianjin, 300457, China
| | - Yuehua Li
- TEDA Institute of Biological Sciences and Biotechnology, Nankai University, Tianjin, 300457, China; Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, Nankai University, Tianjin, 300457, China; Tianjin Key Laboratory of Microbial Functional Genomics, TEDA College, Nankai University, Tianjin, 300457, China
| | - Yujia Li
- TEDA Institute of Biological Sciences and Biotechnology, Nankai University, Tianjin, 300457, China; Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, Nankai University, Tianjin, 300457, China; Tianjin Key Laboratory of Microbial Functional Genomics, TEDA College, Nankai University, Tianjin, 300457, China
| | - Junxiang Yan
- TEDA Institute of Biological Sciences and Biotechnology, Nankai University, Tianjin, 300457, China; Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, Nankai University, Tianjin, 300457, China; Tianjin Key Laboratory of Microbial Functional Genomics, TEDA College, Nankai University, Tianjin, 300457, China
| | - Boyang Cao
- TEDA Institute of Biological Sciences and Biotechnology, Nankai University, Tianjin, 300457, China; Key Laboratory of Molecular Microbiology and Technology of the Ministry of Education, Nankai University, Tianjin, 300457, China; Tianjin Key Laboratory of Microbial Functional Genomics, TEDA College, Nankai University, Tianjin, 300457, China.
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10
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Sah-Teli SK, Hynönen MJ, Sulu R, Dalwani S, Schmitz W, Wierenga RK, Venkatesan R. Insights into the stability and substrate specificity of the E. coli aerobic β-oxidation trifunctional enzyme complex. J Struct Biol 2020; 210:107494. [DOI: 10.1016/j.jsb.2020.107494] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2020] [Revised: 03/09/2020] [Accepted: 03/10/2020] [Indexed: 11/17/2022]
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11
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Gao R, Wei W, Hassan BH, Li J, Deng J, Feng Y. A single regulator NrtR controls bacterial NAD + homeostasis via its acetylation. eLife 2019; 8:51603. [PMID: 31596237 PMCID: PMC6800001 DOI: 10.7554/elife.51603] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2019] [Accepted: 10/04/2019] [Indexed: 12/27/2022] Open
Abstract
Nicotinamide adenine dinucleotide (NAD+) is an indispensable cofactor in all domains of life, and its homeostasis must be regulated tightly. Here we report that a Nudix-related transcriptional factor, designated MsNrtR (MSMEG_3198), controls the de novo pathway of NAD+biosynthesis in M. smegmatis, a non-tuberculosis Mycobacterium. The integrated evidence in vitro and in vivo confirms that MsNrtR is an auto-repressor, which negatively controls the de novo NAD+biosynthetic pathway. Binding of MsNrtR cognate DNA is finely mapped, and can be disrupted by an ADP-ribose intermediate. Unexpectedly, we discover that the acetylation of MsNrtR at Lysine 134 participates in the homeostasis of intra-cellular NAD+ level in M. smegmatis. Furthermore, we demonstrate that NrtR acetylation proceeds via the non-enzymatic acetyl-phosphate (AcP) route rather than by the enzymatic Pat/CobB pathway. In addition, the acetylation also occurs on the paralogs of NrtR in the Gram-positive bacterium Streptococcus and the Gram-negative bacterium Vibrio, suggesting that these proteins have a common mechanism of post-translational modification in the context of NAD+ homeostasis. Together, these findings provide a first paradigm for the recruitment of acetylated NrtR to regulate bacterial central NAD+ metabolism.
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Affiliation(s)
- Rongsui Gao
- Department of Pathogen Biology & Microbiology, and Department General Intensive Care Unit of the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, China
| | - Wenhui Wei
- Department of Pathogen Biology & Microbiology, and Department General Intensive Care Unit of the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, China
| | | | - Jun Li
- Key Laboratory of Bioorganic Synthesis of Zhejiang Province, College of Biotechnology and Bioengineering, Zhejiang University of Technology, Hangzhou, China
| | - Jiaoyu Deng
- Key Laboratory of Agricultural and Environmental Microbiology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China
| | - Youjun Feng
- Department of Pathogen Biology & Microbiology, and Department General Intensive Care Unit of the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, China.,College of Animal Sciences, Zhejiang University, Hangzhou, China
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12
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Wang Q, Hassan BH, Lou N, Merritt J, Feng Y. Functional definition of NrtR, a remnant regulator of NAD + homeostasis in the zoonotic pathogen Streptococcus suis. FASEB J 2019; 33:6055-6068. [PMID: 30759348 PMCID: PMC8793812 DOI: 10.1096/fj.201802179rr] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2018] [Accepted: 01/15/2019] [Indexed: 12/16/2022]
Abstract
NAD+ is an enzyme cofactor required for the 3 domains of life. However, little is known about the NAD+ biosynthesis and salvage pathways in the opportunistic pathogen Streptococcus suis. A genome-wide search allows us to identify the NAD+ salvage pathway encoded by an operon of nadR-pnuC-nrtR (from SSU05_1973 to SSU05_1971 on the reverse strand) in the S. suis 05ZYH33 that causes streptococcal toxin shock-like syndrome. The regulator of this pathway is Nudix-related transcriptional regulator (NrtR), a transcription regulator of the Nudix family comprising an N-terminal Nudix-like effector domain, and a C-terminal DNA-binding winged helix-turn-helix-like domain. Intriguingly, the S. suis NrtR naturally contains a single amino acid substitution (K92E) in the catalytic site of its Nudix domain that renders it catalytically inactive but does not influence its ability to bind DNA. Despite its lack of enzymatic activity, DNA-binding activity of NrtR is antagonized by the effector ADP-ribose. Furthermore, nrtR knockout in S. suis serotype 2 reduces its capacity to form biofilms and attenuates its virulence in a mouse infection model. Genome mining indicates that nrtR appears in a strain-specific manner whose occupancy is correlated to bacterial infectivity. Unlike the paradigmatic member of NrtR family having 2 unrelated functions (Nudix hydrolase and DNA binding), S. suis 2 retains a single regulatory role in the modulation of NAD+ salvage. This control of NAD+ homeostasis contributes to S. suis virulence.-Wang, Q., Hassan, B. H., Lou, N., Merritt, J., Feng, Y. Functional definition of NrtR, a remnant regulator of NAD+ homeostasis in the zoonotic pathogen Streptococcus suis.
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Affiliation(s)
- Qingjing Wang
- Department of Pathogen Biology and MicrobiologyDepartment of General Intensive Care Unit of Second Affiliated HospitalZhejiang University School of MedicineHangzhouChina
| | - Bachar H. Hassan
- Stony Brook Cancer CenterStony Brook UniversityStony BrookNew YorkUSA
| | - Ningjie Lou
- Department of Pathogen Biology and MicrobiologyDepartment of General Intensive Care Unit of Second Affiliated HospitalZhejiang University School of MedicineHangzhouChina
| | - Justin Merritt
- Department of Restorative DentistryOregon Health and Science UniversityPortlandOregonUSA
| | - Youjun Feng
- Department of Pathogen Biology and MicrobiologyDepartment of General Intensive Care Unit of Second Affiliated HospitalZhejiang University School of MedicineHangzhouChina
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13
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Yang J, Fang Y, Wang J, Wang C, Zhao L, Wang X. Deletion of regulator-encoding genes fadR, fabR and iclR to increase L-threonine production in Escherichia coli. Appl Microbiol Biotechnol 2019; 103:4549-4564. [DOI: 10.1007/s00253-019-09818-8] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2019] [Revised: 03/19/2019] [Accepted: 03/31/2019] [Indexed: 12/25/2022]
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An Iterative, Synthetic Approach To Engineer a High-Performance PhoB-Specific Reporter. Appl Environ Microbiol 2018; 84:AEM.00603-18. [PMID: 29752265 DOI: 10.1128/aem.00603-18] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2018] [Accepted: 05/03/2018] [Indexed: 11/20/2022] Open
Abstract
Transcriptional reporters are common tools for analyzing either the transcription of a gene of interest or the activity of a specific transcriptional regulator. Unfortunately, the latter application has the shortcoming that native promoters did not evolve as optimal readouts for the activity of a particular regulator. We sought to synthesize an optimized transcriptional reporter for assessing PhoB activity, aiming for maximal "on" expression when PhoB is active, minimal background in the "off" state, and no control elements for other regulators. We designed specific sequences for promoter elements with appropriately spaced PhoB-binding sites, and at 19 additional intervening nucleotide positions for which we did not predict sequence-specific effects, the bases were randomized. Eighty-three such constructs were screened in Vibrio fischeri, enabling us to identify bases at particular randomized positions that significantly correlated with high-level "on" or low-level "off" expression. A second round of promoter design rationally constrained 13 additional positions, leading to a reporter with high-level PhoB-dependent expression, essentially no background, and no other known regulatory elements. As expressed reporters, we used both stable and destabilized variants of green fluorescent protein (GFP), the latter of which has a half-life of 81 min in V. fischeri In culture, PhoB induced the reporter when phosphate was depleted to a concentration below 10 μM. During symbiotic colonization of its host squid, Euprymna scolopes, the reporter indicated heterogeneous phosphate availability in different light-organ microenvironments. Finally, testing this construct in other members of the Proteobacteria demonstrated its broader utility. The results illustrate how a limited ability to predict synthetic promoter-reporter performance can be overcome through iterative screening and reengineering.IMPORTANCE Transcriptional reporters can be powerful tools for assessing when a particular regulator is active; however, native promoters may not be ideal for this purpose. Optimal reporters should be specific to the regulator being examined and should maximize the difference between the "on" and "off" states; however, these properties are distinct from the selective pressures driving the evolution of natural promoters. Synthetic promoters offer a promising alternative, but our understanding often does not enable fully predictive promoter design, and the large number of alternative sequence possibilities can be intractable. In a synthetic promoter region with over 34 billion sequence variants, we identified bases correlated with favorable performance by screening only 83 candidates, allowing us to rationally constrain our design. We thereby generated an optimized reporter that is induced by PhoB and used it to explore the low-phosphate response of V. fischeri This promoter design strategy will facilitate the engineering of other regulator-specific reporters.
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15
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Kawai Y, Matsumoto S, Ling Y, Okuda S, Tsuneda S. AldB controls persister formation in Escherichia coli depending on environmental stress. Microbiol Immunol 2018; 62:299-309. [PMID: 29577369 DOI: 10.1111/1348-0421.12587] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2018] [Revised: 03/06/2018] [Accepted: 03/15/2018] [Indexed: 12/14/2022]
Abstract
Persisters are multidrug-tolerant cells that are present within antibiotic-sensitive populations. Persister formation is not induced by genetic mutations, but rather by changes in the degree of expression of some genes. High redundancy has been observed among the pathways that have been hypothesized to respond to specific stresses. In this study, we conducted RNA sequencing of Escherichia coli persisters under various stress conditions to identify common mechanisms. We induced stresses such as glucose or amino acid exhaustion, acid stress and anaerobic conditions, all of which are encountered during bacterial pathogenesis. We found that most genes are differentially expressed depending on the specific stress condition; however, some genes were commonly expressed in persisters in most stress conditions. Commonly expressed genes are expected to be promising therapeutic targets for combating persistent infections. We found that knockdown of aldehyde dehydrogenase (aldB), which was expressed in every condition except for acid stress, decreased persisters in the non-stressed condition. However, the same strain unexpectedly showed an increased number of persisters in the amino acid-limited condition. Because the increase in persister number is glycolytic metabolite-dependent, metabolic flow may play a crucial role in aldB-mediated persister formation. These data suggest that environmental stresses alter persister mechanisms. Identification of environmental influences on persister formation during pathogenesis is therefore necessary to enabling persister eradication.
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Affiliation(s)
- Yuto Kawai
- Department of Life Science and Medical Bioscience, Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo 162-8480, Japan
| | - Shinya Matsumoto
- Department of Life Science and Medical Bioscience, Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo 162-8480, Japan
| | - Yiwei Ling
- Graduate School of Medical and Dental Sciences, Niigata University, 1-757 Asahimachi-dori, Chuo-ku, Niigata 951-8510, Japan
| | - Shujiro Okuda
- Graduate School of Medical and Dental Sciences, Niigata University, 1-757 Asahimachi-dori, Chuo-ku, Niigata 951-8510, Japan
| | - Satoshi Tsuneda
- Department of Life Science and Medical Bioscience, Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo 162-8480, Japan
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16
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Wang Q, Li Z, Lin J, Wang X, Deng X, Feng Y. Complex dissemination of the diversified mcr-1-harbouring plasmids in Escherichia coli of different sequence types. Oncotarget 2018; 7:82112-82122. [PMID: 27741523 PMCID: PMC5347679 DOI: 10.18632/oncotarget.12621] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2016] [Accepted: 10/07/2016] [Indexed: 01/03/2023] Open
Abstract
The emergence of the mobilized colistin resistance gene, representing a novel mechanism for bacterial drug resistance, challenges the last resort against the severe infections by Gram-negative bacteria with multi-drug resistances. Very recently, we showed the diversity in the mcr-1-carrying plasmid reservoirs from the gut microbiota. Here, we reported that a similar but more complex scenario is present in the healthy swine populations, Southern China, 2016. Amongst the 1026 pieces of Escherichia coli isolates from 3 different pig farms, 302 E. coli isolates were determined to be positive for the mcr-1 gene (30%, 302/1026). Multi-locus sequence typing assigned no less than 11 kinds of sequence types including one novel Sequence Type to these mcr-1-positive strains. PCR analyses combined with the direct DNA sequencing revealed unexpected complexity of the mcr-1-harbouring plasmids whose backbones are at least grouped into 6 types four of which are new. Transcriptional analyses showed that the mcr-1 promoter of different origins exhibits similar activity. It seems likely that complex dissemination of the diversified mcr-1-bearing plasmids occurs amongst the various ST E. coli inhabiting the healthy swine populations, in Southern China.
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Affiliation(s)
- Qingjing Wang
- Department of Medical Microbiology and Parasitology, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China
| | - Zhencui Li
- Department of Medical Microbiology and Parasitology, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China
| | - Jingxia Lin
- Department of Medical Microbiology and Parasitology, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China
| | - Xiuna Wang
- Department of Medical Microbiology and Parasitology, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China.,Fujian Agriculture and Forestry University, Fuzhou, Fujian, China
| | - Xianbo Deng
- College of Veterinary Medicine, South China Agricultural University, Guangzhou, Guangdong, China
| | - Youjun Feng
- Department of Medical Microbiology and Parasitology, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China
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Gao R, Li D, Lin Y, Lin J, Xia X, Wang H, Bi L, Zhu J, Hassan B, Wang S, Feng Y. Structural and Functional Characterization of the FadR Regulatory Protein from Vibrio alginolyticus. Front Cell Infect Microbiol 2017; 7:513. [PMID: 29312893 PMCID: PMC5733061 DOI: 10.3389/fcimb.2017.00513] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2017] [Accepted: 11/29/2017] [Indexed: 02/03/2023] Open
Abstract
The structure of Vibrio cholerae FadR (VcFadR) complexed with the ligand oleoyl-CoA suggests an additional ligand-binding site. However, the fatty acid metabolism and its regulation is poorly addressed in Vibrio alginolyticus, a species closely-related to V. cholerae. Here, we show crystal structures of V. alginolyticus FadR (ValFadR) alone and its complex with the palmitoyl-CoA, a long-chain fatty acyl ligand different from the oleoyl-CoA occupied by VcFadR. Structural comparison indicates that both VcFadR and ValFadR consistently have an additional ligand-binding site (called site 2), which leads to more dramatic conformational-change of DNA-binding domain than that of the E. coli FadR (EcFadR). Isothermal titration calorimetry (ITC) analyses defines that the ligand-binding pattern of ValFadR (2:1) is distinct from that of EcFadR (1:1). Together with surface plasmon resonance (SPR), electrophoresis mobility shift assay (EMSA) demonstrates that ValFadR binds fabA, an important gene of unsaturated fatty acid (UFA) synthesis. The removal of fadR from V. cholerae attenuates fabA transcription and results in the unbalance of UFA/SFA incorporated into membrane phospholipids. Genetic complementation of the mutant version of fadR (Δ42, 136-177) lacking site 2 cannot restore the defective phenotypes of ΔfadR while the wild-type fadR gene and addition of exogenous oleate can restore them. Mice experiments reveals that VcFadR and its site 2 have roles in bacterial colonizing. Together, the results might represent an additional example that illustrates the Vibrio FadR-mediated lipid regulation and its role in pathogenesis.
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Affiliation(s)
- Rongsui Gao
- Department of Medical Microbiology and Parasitology, Zhejiang University School of Medicine, Hangzhou, China
| | - Defeng Li
- Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
| | - Yuan Lin
- School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Jingxia Lin
- Department of Medical Microbiology and Parasitology, Zhejiang University School of Medicine, Hangzhou, China
| | - Xiaoyun Xia
- Department of Microbiology, Nanjing Agricultural University, Nanjing, China
| | - Hui Wang
- Department of Microbiology, Nanjing Agricultural University, Nanjing, China
| | - Lijun Bi
- Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
| | - Jun Zhu
- Department of Microbiology, Nanjing Agricultural University, Nanjing, China.,Department of Microbiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, United States
| | - Bachar Hassan
- Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC, United States
| | - Shihua Wang
- School of Life Sciences, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Youjun Feng
- Department of Medical Microbiology and Parasitology, Zhejiang University School of Medicine, Hangzhou, China
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18
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Shen X, Mahajani M, Wang J, Yang Y, Yuan Q, Yan Y, Lin Y. Elevating 4-hydroxycoumarin production through alleviating thioesterase-mediated salicoyl-CoA degradation. Metab Eng 2017; 42:59-65. [PMID: 28587908 DOI: 10.1016/j.ymben.2017.05.006] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2017] [Revised: 05/15/2017] [Accepted: 05/31/2017] [Indexed: 12/23/2022]
Abstract
Acyl-CoAs are essential intermediates in the biosynthetic pathways of a number of industrially and pharmaceutically important molecules. When these pathways are reconstituted in a heterologous microbial host for metabolic engineering purposes, the acyl-CoAs may be subject to undesirable hydrolysis by the host's native thioesterases, resulting in a waste of cellular energy and decreased intermediate availability, thus impairing bioconversion efficiency. 4-hydroxycoumarin (4HC) is a direct synthetic precursor to the commonly used oral anticoagulants (e.g. warfarin) and rodenticides. In our previous study, we have established an artificial pathway for 4HC biosynthesis in Escherichia coli, which involves the thioester intermediate salicoyl-CoA. Here, we utilized the 4HC pathway as a demonstration to examine the negative effect of salicoyl-CoA degradaton, identify and inactivate the responsible thioesterase, and eventually improve the 4HC production. We screened a total of 16 E. coli thioesterases and tested their hydrolytic activity towards salicoyl-CoA in vitro. Among all the tested candidate enzymes, YdiI was found to be the dominant contributor to the salicoyl-CoA degradation in E. coli. Remarkably, the ydiI knockout strain carrying the 4HC pathway exhibited an up to 300% increase in 4HC production. An optimized 4HC pathway construct introduced in the ydiI knockout strain led to the accumulation of 935mg/L of 4HC in shake flasks, which is about 1.5 folds higher than the wild-type strain. This study demonstrates a systematic strategy to alleviate the undesirable hydrolysis of thioester intermediates, allowing production enhancement for other biosynthetic pathways with similar issues.
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Affiliation(s)
- Xiaolin Shen
- State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing 100029, China; Beijing Advanced Innovation Center for Soft Matter Science and Engineering, Beijing University of Chemical Technology, Beijing 100029, China
| | | | - Jia Wang
- State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing 100029, China; Beijing Advanced Innovation Center for Soft Matter Science and Engineering, Beijing University of Chemical Technology, Beijing 100029, China
| | - Yaping Yang
- College of Engineering, The University of Georgia, Athens, GA 30602, USA
| | - Qipeng Yuan
- State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing 100029, China; Beijing Advanced Innovation Center for Soft Matter Science and Engineering, Beijing University of Chemical Technology, Beijing 100029, China
| | - Yajun Yan
- College of Engineering, The University of Georgia, Athens, GA 30602, USA.
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Abstract
Antibiotic resistance is a prevalent problem in public health worldwide. In general, the carbapenem β-lactam antibiotics are considered a final resort against lethal infections by multidrug-resistant bacteria. Colistin is a cationic polypeptide antibiotic and acts as the last line of defense for treatment of carbapenem-resistant bacteria. Very recently, a new plasmid-borne colistin resistance gene, mcr-2, was revealed soon after the discovery of the paradigm gene mcr-1, which has disseminated globally. However, the molecular mechanisms for MCR-2 colistin resistance are poorly understood. Here we show a unique transposon unit that facilitates the acquisition and transfer of mcr-2 Evolutionary analyses suggested that both MCR-2 and MCR-1 might be traced to their cousin phosphoethanolamine (PEA) lipid A transferase from a known polymyxin producer, Paenibacillus Transcriptional analyses showed that the level of mcr-2 transcripts is relatively higher than that of mcr-1 Genetic deletions revealed that the transmembrane regions (TM1 and TM2) of both MCR-1 and MCR-2 are critical for their location and function in bacterial periplasm, and domain swapping indicated that the TM2 is more efficient than TM1. Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) confirmed that all four MCR proteins (MCR-1, MCR-2, and two chimeric versions [TM1-MCR-2 and TM2-MCR-1]) can catalyze chemical modification of lipid A moiety anchored on lipopolysaccharide (LPS) with the addition of phosphoethanolamine to the phosphate group at the 4' position of the sugar. Structure-guided site-directed mutagenesis defined an essential 6-residue-requiring zinc-binding/catalytic motif for MCR-2 colistin resistance. The results further our mechanistic understanding of transferable colistin resistance, providing clues to improve clinical therapeutics targeting severe infections by MCR-2-containing pathogens.IMPORTANCE Carbapenem and colistin are the last line of refuge in fighting multidrug-resistant Gram-negative pathogens. MCR-2 is a newly emerging variant of the mobilized colistin resistance protein MCR-1, posing a potential challenge to public health. Here we report transfer of the mcr-2 gene by a unique transposal event and its possible origin. Distribution of MCR-2 in bacterial periplasm is proposed to be a prerequisite for its role in the context of biochemistry and the colistin resistance. We also define the genetic requirement of a zinc-binding/catalytic motif for MCR-2 colistin resistance. This represents a glimpse of transferable colistin resistance by MCR-2.
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20
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Functional definition of BirA suggests a biotin utilization pathway in the zoonotic pathogen Streptococcus suis. Sci Rep 2016; 6:26479. [PMID: 27217336 PMCID: PMC4877710 DOI: 10.1038/srep26479] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2016] [Accepted: 05/04/2016] [Indexed: 11/30/2022] Open
Abstract
Biotin protein ligase is universal in three domains of life. The paradigm version of BPL is the Escherichia coli BirA that is also a repressor for the biotin biosynthesis pathway. Streptococcus suis, a leading bacterial agent for swine diseases, seems to be an increasingly-important opportunistic human pathogen. Unlike the scenario in E. coli, S. suis lacks the de novo biotin biosynthesis pathway. In contrast, it retains a bioY, a biotin transporter-encoding gene, indicating an alternative survival strategy for S. suis to scavenge biotin from its inhabiting niche. Here we report functional definition of S. suis birA homologue. The in vivo functions of the birA paralogue with only 23.6% identity to the counterpart of E. coli, was judged by its ability to complement the conditional lethal mutants of E. coli birA. The recombinant BirA protein of S. suis was overexpressed in E. coli, purified to homogeneity and verified with MS. Both cellulose TLC and MALDI-TOFF-MS assays demonstrated that the S. suis BirA protein catalyzed the biotinylation reaction of its acceptor biotin carboxyl carrier protein. EMSA assays confirmed binding of the bioY gene to the S. suis BirA. The data defined the first example of the bifunctional BirA ligase/repressor in Streptococcus.
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21
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Zhang H, Wang Q, Fisher DJ, Cai M, Chakravartty V, Ye H, Li P, Solbiati JO, Feng Y. Deciphering a unique biotin scavenging pathway with redundant genes in the probiotic bacterium Lactococcus lactis. Sci Rep 2016; 6:25680. [PMID: 27161258 PMCID: PMC4861984 DOI: 10.1038/srep25680] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2016] [Accepted: 04/13/2016] [Indexed: 11/12/2022] Open
Abstract
Biotin protein ligase (BPL) is widespread in the three domains of the life. The paradigm BPL is the Escherichia coli BirA protein, which also functions as a repressor for the biotin biosynthesis pathway. Here we report that Lactococcus lactis possesses two different orthologues of birA (birA1_LL and birA2_LL). Unlike the scenario in E. coli, L. lactis appears to be auxotrophic for biotin in that it lacks a full biotin biosynthesis pathway. In contrast, it retains two biotin transporter-encoding genes (bioY1_LL and bioY2_LL), suggesting the use of a scavenging strategy to obtain biotin from the environment. The in vivo function of the two L. lactis birA genes was judged by their abilities to complement the conditional lethal E. coli birA mutant. Thin-layer chromatography and mass spectroscopy assays demonstrated that these two recombinant BirA proteins catalyze the biotinylation reaction of the acceptor biotin carboxyl carrier protein (BCCP), through the expected biotinoyl-AMP intermediate. Gel shift assays were used to characterize bioY1_LL and BirA1_LL. We also determined the ability to uptake 3H-biotin by L. lactis. Taken together, our results deciphered a unique biotin scavenging pathway with redundant genes present in the probiotic bacterium L. lactis.
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Affiliation(s)
- Huimin Zhang
- Department of Medical Microbiology and Parasitology, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310058, PR China.,Institute for Genomic Biology, University of Illinois, Urbana, Illinois 61801, USA
| | - Qingjing Wang
- Department of Medical Microbiology and Parasitology, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310058, PR China
| | - Derek J Fisher
- Department of Microbiology, Southern Illinois University, Carbondale, IL 62901, USA
| | - Mingzhu Cai
- Department of Medical Microbiology and Parasitology, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310058, PR China
| | | | - Huiyan Ye
- Department of Medical Microbiology and Parasitology, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310058, PR China
| | - Ping Li
- Department of Medical Microbiology and Parasitology, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310058, PR China
| | - Jose O Solbiati
- Institute for Genomic Biology, University of Illinois, Urbana, Illinois 61801, USA
| | - Youjun Feng
- Department of Medical Microbiology and Parasitology, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310058, PR China
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Transcriptional Repression of the VC2105 Protein by Vibrio FadR Suggests that It Is a New Auxiliary Member of the fad Regulon. Appl Environ Microbiol 2016; 82:2819-2832. [PMID: 26944841 DOI: 10.1128/aem.00293-16] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2016] [Accepted: 02/25/2016] [Indexed: 02/03/2023] Open
Abstract
UNLABELLED Recently, our group along with others reported that the Vibrio FadR regulatory protein is unusual in that, unlike the prototypical fadR product of Escherichia coli, which has only one ligand-binding site, Vibrio FadR has two ligand-binding sites and represents a new mechanism for fatty acid sensing. The promoter region of the vc2105 gene, encoding a putative thioesterase, was mapped, and a putative FadR-binding site (AA CTG GTA AGA GCA CTT) was proposed. Different versions of the FadR regulatory proteins were prepared and purified to homogeneity. Both electrophoretic mobility shift assay (EMSA) and surface plasmon resonance (SPR) determined the direct interaction of the vc2105 gene with FadR proteins of various origins. Further, EMSAs illustrated that the addition of long-chain acyl-coenzyme A (CoA) species efficiently dissociates the vc2105 promoter from the FadR regulator. The expression level of the Vibrio cholerae vc2105 gene was elevated 2- to 3-fold in a fadR null mutant strain, validating that FadR is a repressor for the vc2105 gene. The β-galactosidase activity of a vc2105-lacZ transcriptional fusion was increased over 2-fold upon supplementation of growth medium with oleic acid. Unlike the fadD gene, a member of the Vibrio fad regulon, the VC2105 protein played no role in bacterial growth and virulence-associated gene expression of ctxAB (cholera toxin A/B) and tcpA (toxin coregulated pilus A). Given that the transcriptional regulation of vc2105 fits the criteria for fatty acid degradation (fad) genes, we suggested that it is a new member of the Vibrio fad regulon. IMPORTANCE The Vibrio FadR regulator is unusual in that it has two ligand-binding sites. Different versions of the FadR regulatory proteins were prepared and characterized in vitro and in vivo. An auxiliary fad gene (vc2105) from Vibrio was proposed that encodes a putative thioesterase and has a predicted FadR-binding site (AAC TGG TA A GAG CAC TT). The function of this putative binding site was proved using both EMSA and SPR. Further in vitro and in vivo experiments revealed that the Vibrio FadR is a repressor for the vc2105 gene. Unlike fadD, a member of the Vibrio fad regulon, VC2105 played no role in bacterial growth and expression of the two virulence-associated genes (ctxAB and tcpA). Therefore, since transcriptional regulation of vc2105 fits the criteria for fad genes, it seems likely that vc2105 acts as a new auxiliary member of the Vibrio fad regulon.
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Zhang H, Ravcheev DA, Hu D, Zhang F, Gong X, Hao L, Cao M, Rodionov DA, Wang C, Feng Y. Two novel regulators of N-acetyl-galactosamine utilization pathway and distinct roles in bacterial infections. Microbiologyopen 2015; 4:983-1000. [PMID: 26540018 PMCID: PMC4694137 DOI: 10.1002/mbo3.307] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2015] [Revised: 09/21/2015] [Accepted: 09/28/2015] [Indexed: 12/19/2022] Open
Abstract
Bacterial pathogens can exploit metabolic pathways to facilitate their successful infection cycles, but little is known about roles of d‐galactosamine (GalN)/N‐acetyl‐d‐galactosamine (GalNAc) catabolism pathway in bacterial pathogenesis. Here, we report the genomic reconstruction of GalN/GalNAc utilization pathway in Streptococci and the diversified aga regulons. We delineated two new paralogous AgaR regulators for the GalN/GalNAc catabolism pathway. The electrophoretic mobility shift assays experiment demonstrated that AgaR2 (AgaR1) binds the predicted palindromes, and the combined in vivo data from reverse transcription quantitative polymerase chain reaction and RNA‐seq suggested that AgaR2 (not AgaR1) can effectively repress the transcription of the target genes. Removal of agaR2 (not agaR1) from Streptococcus suis 05ZYH33 augments significantly the abilities of both adherence to Hep‐2 cells and anti‐phagocytosis against RAW264.7 macrophage. As anticipated, the dysfunction in AgaR2‐mediated regulation of S. suis impairs its pathogenicity in experimental models of both mice and piglets. Our finding discovered two novel regulators specific for GalN/GalNAc catabolism and assigned them distinct roles into bacterial infections. To the best of our knowledge, it might represent a first paradigm that links the GalN/GalNAc catabolism pathway to bacterial pathogenesis.
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Affiliation(s)
- Huimin Zhang
- Department of Medical Microbiology and Parasitology, Zhejiang University School of Medicine, Hangzhou, Zhejiang, 310058, China
| | - Dmitry A Ravcheev
- Luxembourg Centre for Systems Biomedicine, University of Luxembourg, Esch-sur-Alzette, L-4360, Luxembourg
| | - Dan Hu
- Department of Epidemiology, Research Institute for Medicine of Nanjing Command, Nanjing, 210002, China
| | - Fengyu Zhang
- Department of Epidemiology, Research Institute for Medicine of Nanjing Command, Nanjing, 210002, China
| | - Xiufang Gong
- Department of Epidemiology, Research Institute for Medicine of Nanjing Command, Nanjing, 210002, China
| | - Lina Hao
- Department of Epidemiology, Research Institute for Medicine of Nanjing Command, Nanjing, 210002, China
| | - Min Cao
- Department of Epidemiology, Research Institute for Medicine of Nanjing Command, Nanjing, 210002, China
| | - Dmitry A Rodionov
- A.A. Kharkevich Institute for Information Transmission Problems, Russian Academy of Sciences, Moscow, 127994, Russia
| | - Changjun Wang
- Department of Epidemiology, Research Institute for Medicine of Nanjing Command, Nanjing, 210002, China
| | - Youjun Feng
- Department of Medical Microbiology and Parasitology, Zhejiang University School of Medicine, Hangzhou, Zhejiang, 310058, China
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Zhang H, Zheng B, Gao R, Feng Y. Binding of Shewanella FadR to the fabA fatty acid biosynthetic gene: implications for contraction of the fad regulon. Protein Cell 2015; 6:667-679. [PMID: 26050090 PMCID: PMC4537474 DOI: 10.1007/s13238-015-0172-2] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2015] [Accepted: 05/06/2015] [Indexed: 11/25/2022] Open
Abstract
The Escherichia coli fadR protein product, a paradigm/prototypical FadR regulator, positively regulates fabA and fabB, the two critical genes for unsaturated fatty acid (UFA) biosynthesis. However the scenario in the other Ɣ-proteobacteria, such as Shewanella with the marine origin, is unusual in that Rodionov and coworkers predicted that only fabA (not fabB) has a binding site for FadR protein. It raised the possibility of fad regulon contraction. Here we report that this is the case. Sequence alignment of the FadR homologs revealed that the N-terminal DNA-binding domain exhibited remarkable similarity, whereas the ligand-accepting motif at C-terminus is relatively-less conserved. The FadR homologue of S. oneidensis (referred to FadR_she) was over-expressed and purified to homogeneity. Integrative evidence obtained by FPLC (fast protein liquid chromatography) and chemical cross-linking analyses elucidated that FadR_she protein can dimerize in solution, whose identity was determined by MALDI-TOF-MS. In vitro data from electrophoretic mobility shift assays suggested that FadR_she is almost functionally-exchangeable/equivalent to E. coli FadR (FadR_ec) in the ability of binding the E. coli fabA (and fabB) promoters. In an agreement with that of E. coli fabA, S. oneidensis fabA promoter bound both FadR_she and FadR_ec, and was disassociated specifically with the FadR regulatory protein upon the addition of long-chain acyl-CoA thioesters. To monitor in vivo effect exerted by FadR on Shewanella fabA expression, the native promoter of S. oneidensis fabA was fused to a LacZ reporter gene to engineer a chromosome fabA-lacZ transcriptional fusion in E. coli. As anticipated, the removal of fadR gene gave about 2-fold decrement of Shewanella fabA expression by β-gal activity, which is almost identical to the inhibitory level by the addition of oleate. Therefore, we concluded that fabA is contracted to be the only one member of fad regulon in the context of fatty acid synthesis in the marine bacteria Shewanella genus.
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Affiliation(s)
- Huimin Zhang
- Department of Medical Microbiology & Parasitology, Zhejiang University School of Medicine, Hangzhou, 310058 China
| | - Beiwen Zheng
- Department of Medical Microbiology & Parasitology, Zhejiang University School of Medicine, Hangzhou, 310058 China.,State Key Laboratory for Diagnosis and Treatment of Infectious Diseases, Zhejiang University School of Medicine, Hangzhou, 310058 China
| | - Rongsui Gao
- Department of Medical Microbiology & Parasitology, Zhejiang University School of Medicine, Hangzhou, 310058 China
| | - Youjun Feng
- Department of Medical Microbiology & Parasitology, Zhejiang University School of Medicine, Hangzhou, 310058 China.,State Key Laboratory for Diagnosis and Treatment of Infectious Diseases, Zhejiang University School of Medicine, Hangzhou, 310058 China
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Feng Y, Kumar R, Ravcheev DA, Zhang H. Paracoccus denitrificans possesses two BioR homologs having a role in regulation of biotin metabolism. Microbiologyopen 2015; 4:644-59. [PMID: 26037461 PMCID: PMC4554459 DOI: 10.1002/mbo3.270] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2015] [Revised: 05/04/2015] [Accepted: 05/12/2015] [Indexed: 11/05/2022] Open
Abstract
Recently, we determined that BioR, the GntR family of transcription factor, acts as a repressor for biotin metabolism exclusively distributed in certain species of α-proteobacteria, including the zoonotic agent Brucella melitensis and the plant pathogen Agrobacterium tumefaciens. However, the scenario is unusual in Paracoccus denitrificans, another closely related member of the same phylum α-proteobacteria featuring with denitrification. Not only does it encode two BioR homologs Pden_1431 and Pden_2922 (designated as BioR1 and BioR2, respectively), but also has six predictive BioR-recognizable sites (the two bioR homolog each has one site, whereas the two bio operons (bioBFDAGC and bioYB) each contains two tandem BioR boxes). It raised the possibility that unexpected complexity is present in BioR-mediated biotin regulation. Here we report that this is the case. The identity of the purified BioR proteins (BioR1 and BioR2) was confirmed with LC-QToF-MS. Phylogenetic analyses combined with GC percentage raised a possibility that the bioR2 gene might be acquired by horizontal gene transfer. Gel shift assays revealed that the predicted BioR-binding sites are functional for the two BioR homologs, in much similarity to the scenario seen with the BioR site of A. tumefaciens bioBFDAZ. Using the A. tumefaciens reporter system carrying a plasmid-borne LacZ fusion, we revealed that the two homologs of P. denitrificans BioR are functional repressors for biotin metabolism. As anticipated, not only does the addition of exogenous biotin stimulate efficiently the expression of bioYB operon encoding biotin transport/uptake system BioY, but also inhibits the transcription of the bioBFDAGC operon resembling the de novo biotin synthetic pathway. EMSA-based screening failed to demonstrate that the biotin-related metabolite is involved in BioR-DNA interplay, which is consistent with our former observation with Brucella BioR. Our finding defined a complex regulatory network for biotin metabolism in P. denitrificans by two BioR proteins.
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Affiliation(s)
- Youjun Feng
- Department of Medical Microbiology & Parasitology, Zhejiang University School of Medicine, Hangzhou, Zhejiang, 310058, China
| | - Ritesh Kumar
- Institute of Biosciences and Technology, Texas A&M Health Science Center, Houston, Texas, 77030
| | - Dmitry A Ravcheev
- Luxembourg Centre for Systems Biomedicine, University of Luxembourg, 2, avenue de l'Université, L-4365, Esch-sur-Alzette, Luxembourg
| | - Huimin Zhang
- Department of Medical Microbiology & Parasitology, Zhejiang University School of Medicine, Hangzhou, Zhejiang, 310058, China
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Zhang H, Luo Q, Gao H, Feng Y. A new regulatory mechanism for bacterial lipoic acid synthesis. Microbiologyopen 2015; 4:282-300. [PMID: 25611823 PMCID: PMC4398509 DOI: 10.1002/mbo3.237] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2014] [Revised: 12/01/2014] [Accepted: 12/09/2014] [Indexed: 01/15/2023] Open
Abstract
Lipoic acid, an essential enzyme cofactor, is required in three domains of life. In the past 60 years since its discovery, most of the pathway for lipoic acid synthesis and metabolism has been elucidated. However, genetic control of lipoic acid synthesis remains unclear. Here, we report integrative evidence that bacterial cAMP-dependent signaling is linked to lipoic acid synthesis in Shewanella species, the certain of unique marine-borne bacteria with special ability of metal reduction. Physiological requirement of protein lipoylation in γ-proteobacteria including Shewanella oneidensis was detected using Western blotting with rabbit anti-lipoyl protein primary antibody. The two genes (lipB and lipA) encoding lipoic acid synthesis pathway were proved to be organized into an operon lipBA in Shewanella, and the promoter was mapped. Electrophoretic mobility shift assays confirmed that the putative CRP-recognizable site (AAGTGTGATCTATCTTACATTT) binds to cAMP-CRP protein with origins of both Escherichia coli and Shewanella. The native lipBA promoter of Shewanella was fused to a LacZ reporter gene to create a chromosome lipBA-lacZ transcriptional fusion in E. coli and S. oneidensis, allowing us to directly assay its expression level by β-galactosidase activity. As anticipated, the removal of E. coli crp gene gave above fourfold increment of lipBA promoter-driven β-gal expression. The similar scenario was confirmed by both the real-time quantitative PCR and the LacZ transcriptional fusion in the crp mutant of Shewanella. Furthermore, the glucose effect on the lipBA expression of Shewanella was evaluated in the alternative microorganism E. coli. As anticipated, an addition of glucose into media effectively induces the transcriptional level of Shewanella lipBA in that the lowered cAMP level relieves the repression of lipBA by cAMP-CRP complex. Therefore, our finding might represent a first paradigm mechanism for genetic control of bacterial lipoic acid synthesis.
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Affiliation(s)
- Huimin Zhang
- Center for Infection and Immunity, Department of Medical Microbiology and Parasitology, School of Basic Medical Sciences, Zhejiang University, Hangzhou, Zhejiang, China
| | - Qixia Luo
- Institute of Microbiology, College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, China
| | - Haichun Gao
- Institute of Microbiology, College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, China
| | - Youjun Feng
- Center for Infection and Immunity, Department of Medical Microbiology and Parasitology, School of Basic Medical Sciences, Zhejiang University, Hangzhou, Zhejiang, China
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Beld J, Lee DJ, Burkart MD. Fatty acid biosynthesis revisited: structure elucidation and metabolic engineering. MOLECULAR BIOSYSTEMS 2015; 11:38-59. [PMID: 25360565 PMCID: PMC4276719 DOI: 10.1039/c4mb00443d] [Citation(s) in RCA: 121] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Fatty acids are primary metabolites synthesized by complex, elegant, and essential biosynthetic machinery. Fatty acid synthases resemble an iterative assembly line, with an acyl carrier protein conveying the growing fatty acid to necessary enzymatic domains for modification. Each catalytic domain is a unique enzyme spanning a wide range of folds and structures. Although they harbor the same enzymatic activities, two different types of fatty acid synthase architectures are observed in nature. During recent years, strained petroleum supplies have driven interest in engineering organisms to either produce more fatty acids or specific high value products. Such efforts require a fundamental understanding of the enzymatic activities and regulation of fatty acid synthases. Despite more than one hundred years of research, we continue to learn new lessons about fatty acid synthases' many intricate structural and regulatory elements. In this review, we summarize each enzymatic domain and discuss efforts to engineer fatty acid synthases, providing some clues to important challenges and opportunities in the field.
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Affiliation(s)
- Joris Beld
- Department of Chemistry and Biochemistry, University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0358, USA.
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28
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A new glimpse of FadR-DNA crosstalk revealed by deep dissection of the E. coli FadR regulatory protein. Protein Cell 2014; 5:928-39. [PMID: 25311842 PMCID: PMC4259882 DOI: 10.1007/s13238-014-0107-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2014] [Accepted: 08/29/2014] [Indexed: 12/01/2022] Open
Abstract
Escherichia coli (E. coli) FadR regulator plays dual roles in fatty acid metabolism, which not only represses the fatty acid degradation (fad) system, but also activates the unsaturated fatty acid synthesis pathway. Earlier structural and biochemical studies of FadR protein have provided insights into interplay between FadR protein with its DNA target and/or ligand, while the missing knowledge gap (esp. residues with indirect roles in DNA binding) remains unclear. Here we report this case through deep mapping of old E. coli fadR mutants accumulated. Molecular dissection of E. coli K113 strain, a fadR mutant that can grow on decanoic acid (C10) as sole carbon sources unexpectedly revealed a single point mutation of T178G in fadR locus (W60G in FadRk113). We also observed that a single genetically-recessive mutation of W60G in FadR regulatory protein can lead to loss of its DNA-binding activity, and thereby impair all the regulatory roles in fatty acid metabolisms. Structural analyses of FadR protein indicated that the hydrophobic interaction amongst the three amino acids (W60, F74 and W75) is critical for its DNA-binding ability by maintaining the configuration of its neighboring two β-sheets. Further site-directed mutagenesis analyses demonstrated that the FadR mutants (F74G and/or W75G) do not exhibit the detected DNA-binding activity, validating above structural reasoning.
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29
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Tang Q, Li X, Zou T, Zhang H, Wang Y, Gao R, Li Z, He J, Feng Y. Mycobacterium smegmatis BioQ defines a new regulatory network for biotin metabolism. Mol Microbiol 2014; 94:1006-1023. [PMID: 25287944 DOI: 10.1111/mmi.12817] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/28/2014] [Indexed: 02/06/2023]
Abstract
Biotin (vitamin H), the sulfur-containing enzyme cofactor, is an essential micronutrient for three domains of life. Given the fact that biotin is an energetically expensive molecule whose de novo biosynthesis demands 20 ATP equivalents each, it is reasonable that bacteria have evolved diversified mechanisms in various microorganisms to tightly control biotin metabolism. Unlike the Escherichia coli BirA, the prototypical bi-functional version of biotin protein ligase (BPL) in that it acts as a repressor for biotin biosynthesis pathway, the BirA protein of Mycobacterium smegmatis (M. smegmatis), a closely relative of the tuberculosis-causing pathogen, Mycobacterium tuberculosis, lacked the DNA-binding activity. It raised a possibility that an alternative new regulator might be present to compensate the loss of regulatory function. Here we report that this is the case. Genomic context analyses of M. smegmatis detected a newly identified BioQ homolog classified into the TetR family of transcription factor and its recognizable palindromes. The M. smegmatis BioQ protein was overexpressed and purified to homogeneity. Size-exclusion chromatography combined with chemical cross-linking studies demonstrated that the BioQ protein had a propensity to dimerize. The promoters of bioFD and bioQ/B were mapped using 5'-RACE. Electrophoretic mobility shift assays revealed that BioQ binds specifically to the promoter regions of bioFD and bioQ/B. Further DNase I foot-printing elucidated the BioQ-binding palindromes. Site-directed mutagenesis suggested the important residues critical for BioQ/DNA binding. The isogenic mutant of bioQ (ΔbioQ) was generated using the approach of homologous recombination. The in vivo data from the real-time qPCR combined with the lacZ transcriptional fusion experiments proved that removal of bioQ gave significant increment with expression of bio operons. Also, expression of bio operons were repressed by exogenous addition of biotin, and this repression seemed to depend on the presence of BioQ protein. Thereby, we believed that M. smegmatis BioQ is not only a negative auto-regulator but also a repressor for bioFD and bioB operons involved in the biotin biosynthesis pathway. Collectively, this finding defined the two-protein paradigm of BirA and BioQ, representing a new mechanism for bacterial biotin metabolism.
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Affiliation(s)
- Qing Tang
- State Key Laboratory of Agricultural Microbiology, College of Life Science and Technology, Huazhong Agricultural University, Wuhan, Hubei, 430070, China
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Feng Y, Cronan JE. PdhR, the pyruvate dehydrogenase repressor, does not regulate lipoic acid synthesis. Res Microbiol 2014; 165:429-38. [PMID: 24816490 PMCID: PMC4134263 DOI: 10.1016/j.resmic.2014.04.005] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2014] [Revised: 04/23/2014] [Accepted: 04/24/2014] [Indexed: 12/17/2022]
Abstract
Lipoic acid is a covalently-bound enzyme cofactor required for central metabolism all three domains of life. In the last 20 years the pathway of lipoic acid synthesis and metabolism has been established in Escherichia coli. Expression of the genes of the lipoic acid biosynthesis pathway was believed to be constitutive. However, in 2010 Kaleta and coworkers (BMC Syst. Biol. 4:116) predicted a binding site for the pyruvate dehydrogenase operon repressor, PdhR (referred to lipA site 1) upstream of lipA, the gene encoding lipoic acid synthase and concluded that PdhR regulates lipA transcription. We report in vivo and in vitro evidence that lipA is not controlled by PdhR and that the putative regulatory site deduced by the prior workers is nonfunctional and physiologically irrelevant. E. coli PdhR was purified to homogeneity and used for electrophoretic mobility shift assays. The lipA site 1 of Kaleta and coworkers failed to bind PdhR. The binding detected by these workers is due to another site (lipA site 3) located far upstream of the lipA promoter. Relative to the canonical PdhR binding site lipA site 3 is a half-palindrome and as expected had only weak PdhR binding ability. Manipulation of lipA site 3 to construct a palindrome gave significantly enhanced PdhR binding affinity. The native lipA promoter and the version carrying the artificial lipA3 palindrome were transcriptionally fused to a LacZ reporter gene to directly assay lipA expression. Deletion of pdhR gave no significant change in lipA promoter-driven β-galactosidase activity with either the native or constructed palindrome upstream sequences, indicating that PdhR plays no physiological role in regulation of lipA expression.
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Affiliation(s)
- Youjun Feng
- Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases & State Key Laboratory for Diagnosis and Treatment of Infectious Disease, First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310058, PR China; Department of Medical Microbiology and Parasitology, Zhejiang University School of Medicine, Hangzhou, Zhejiang 310058, PR China; Department of Microbiology, University of Illinois at Urbana-Champaign, IL 61801, USA
| | - John E Cronan
- Department of Microbiology, University of Illinois at Urbana-Champaign, IL 61801, USA; Department of Biochemistry, University of Illinois at Urbana-Champaign, IL 61801, USA.
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The β-galactosidase (BgaC) of the zoonotic pathogen Streptococcus suis is a surface protein without the involvement of bacterial virulence. Sci Rep 2014; 4:4140. [PMID: 24556915 PMCID: PMC3931136 DOI: 10.1038/srep04140] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2013] [Accepted: 01/30/2014] [Indexed: 12/27/2022] Open
Abstract
Streptococcal pathogens have evolved to express exoglycosidases, one of which is BgaC β-galactosidase, to deglycosidate host surface glycolconjucates with exposure of the polysaccharide receptor for bacterial adherence. The paradigm BgaC protein is the bgaC product of Streptococcus, a bacterial surface-exposed β-galactosidase. Here we report the functional definition of the BgaC homologue from an epidemic Chinese strain 05ZYH33 of the zoonotic pathogen Streptococcus suis. Bioinformatics analyses revealed that S. suis BgaC shared the conserved active sites (W240, W243 and Y454). The recombinant BgaC protein of S. suis was purified to homogeneity. Enzymatic assays confirmed its activity of β-galactosidase. Also, the hydrolysis activity was found to be region-specific and sugar-specific for the Gal β-1,3-GlcNAc moiety of oligosaccharides. Flow cytometry analyses combined with immune electron microscopy demonstrated that S. suis BgaC is an atypical surface-anchored protein in that it lacks the “LPXTG” motif for typical surface proteins. Integrative evidence from cell lines and mice-based experiments showed that an inactivation of bgaC does not significantly impair the ability of neither adherence nor anti-phagocytosis, and consequently failed to attenuate bacterial virulence, which is somewhat similar to the scenario seen with S. pneumoniae. Therefore we concluded that S. suis BgaC is an atypical surface-exposed protein without the involvement of bacterial virulence.
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32
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Feng Y, Napier BA, Manandhar M, Henke SK, Weiss DS, Cronan JE. A Francisella virulence factor catalyses an essential reaction of biotin synthesis. Mol Microbiol 2013; 91:300-14. [PMID: 24313380 DOI: 10.1111/mmi.12460] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/12/2013] [Indexed: 01/09/2023]
Abstract
We recently identified a gene (FTN_0818) required for Francisella virulence that seemed likely involved in biotin metabolism. However, the molecular function of this virulence determinant was unclear. Here we show that this protein named BioJ is the enzyme of the biotin biosynthesis pathway that determines the chain length of the biotin valeryl side-chain. Expression of bioJ allows growth of an Escherichia coli bioH strain on biotin-free medium, indicating functional equivalence of BioJ to the paradigm pimeloyl-ACP methyl ester carboxyl-esterase, BioH. BioJ was purified to homogeneity, shown to be monomeric and capable of hydrolysis of its physiological substrate methyl pimeloyl-ACP to pimeloyl-ACP, the precursor required to begin formation of the fused heterocyclic rings of biotin. Phylogenetic analyses confirmed that distinct from BioH, BioJ represents a novel subclade of the α/β-hydrolase family. Structure-guided mapping combined with site-directed mutagenesis revealed that the BioJ catalytic triad consists of Ser151, Asp248 and His278, all of which are essential for activity and virulence. The biotin synthesis pathway was reconstituted reaction in vitro and the physiological role of BioJ directly assayed. To the best of our knowledge, these data represent further evidence linking biotin synthesis to bacterial virulence.
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Affiliation(s)
- Youjun Feng
- Department of Microbiology, University of Illinois at Urbana-Champaign, IL, 61801, USA; Institute of Microbiology, College of Life Science, Zhejiang University, Hangzhou, Zhejiang Province, China
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Lin CY, Awano N, Masuda H, Park JH, Inouye M. Transcriptional repressor HipB regulates the multiple promoters in Escherichia coli. J Mol Microbiol Biotechnol 2013; 23:440-7. [PMID: 24089053 DOI: 10.1159/000354311] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
HipB is a DNA-binding protein in Escherichia coli and negatively regulates its own promoter by binding to the palindromic sequences [TATCCN8GGATA (N represents any nucleotides)] on the hipBA promoter. For such sequences, bioinformatic analysis revealed that there are a total of 39 palindromic sequences (TATCCN(x)GGATA: N is any nucleotides and x is the number of nucleotides from 1 to 30) in the promoter regions of 33 genes on the E. coli genome. Notably, eutH and fadH have two and three TATCCN(x)GGATA palindromic sequences located in their promoters, respectively. Another significant finding was that a palindromic sequence was also identified in the promoter region of hipAB locus, known to be involved in the RelA-dependent persister cell formation in bacteria. Here, we demonstrated that HipB binds to the palindromic structures in the eutH, fadH, as well as the relA promoter regions and represses their expressions. We further demonstrated that HipA enhances the repression of the relA promoter activity by HipB. This effect was not observed with D291A HipA mutant which was previously shown to lack an ability to interact with HipB, indicating that HipA enhances the HipB's repressor activity through direct interaction with HipB.
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Affiliation(s)
- Chun-Yi Lin
- Department of Biochemistry, Robert Wood Johnson Medical School and Center for Advanced Biotechnology and Medicine, Piscataway, N.J., USA
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Parsons JB, Rock CO. Bacterial lipids: metabolism and membrane homeostasis. Prog Lipid Res 2013; 52:249-76. [PMID: 23500459 PMCID: PMC3665635 DOI: 10.1016/j.plipres.2013.02.002] [Citation(s) in RCA: 298] [Impact Index Per Article: 27.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2013] [Revised: 02/27/2013] [Accepted: 02/28/2013] [Indexed: 11/29/2022]
Abstract
Membrane lipid homeostasis is a vital facet of bacterial cell physiology. For decades, research in bacterial lipid synthesis was largely confined to the Escherichia coli model system. This basic research provided a blueprint for the biochemistry of lipid metabolism that has largely defined the individual steps in bacterial fatty acid and phospholipids synthesis. The advent of genomic sequencing has revealed a surprising amount of diversity in the genes, enzymes and genetic organization of the components responsible for bacterial lipid synthesis. Although the chemical steps in fatty acid synthesis are largely conserved in bacteria, there are surprising differences in the structure and cofactor requirements for the enzymes that perform these reactions in Gram-positive and Gram-negative bacteria. This review summarizes how the explosion of new information on the diversity of biochemical and genetic regulatory mechanisms has impacted our understanding of bacterial lipid homeostasis. The potential and problems of developing therapeutics that block pathogen phospholipid synthesis are explored and evaluated. The study of bacterial lipid metabolism continues to be a rich source for new biochemistry that underlies the variety and adaptability of bacterial life styles.
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Affiliation(s)
- Joshua B Parsons
- Department of Infectious Diseases, St. Jude Children's Research Hospital, 262 Danny Thomas Place, Memphis, TN 38105, USA
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35
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Myers KS, Yan H, Ong IM, Chung D, Liang K, Tran F, Keleş S, Landick R, Kiley PJ. Genome-scale analysis of escherichia coli FNR reveals complex features of transcription factor binding. PLoS Genet 2013; 9:e1003565. [PMID: 23818864 PMCID: PMC3688515 DOI: 10.1371/journal.pgen.1003565] [Citation(s) in RCA: 132] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2013] [Accepted: 04/29/2013] [Indexed: 01/05/2023] Open
Abstract
FNR is a well-studied global regulator of anaerobiosis, which is widely conserved across bacteria. Despite the importance of FNR and anaerobiosis in microbial lifestyles, the factors that influence its function on a genome-wide scale are poorly understood. Here, we report a functional genomic analysis of FNR action. We find that FNR occupancy at many target sites is strongly influenced by nucleoid-associated proteins (NAPs) that restrict access to many FNR binding sites. At a genome-wide level, only a subset of predicted FNR binding sites were bound under anaerobic fermentative conditions and many appeared to be masked by the NAPs H-NS, IHF and Fis. Similar assays in cells lacking H-NS and its paralog StpA showed increased FNR occupancy at sites bound by H-NS in WT strains, indicating that large regions of the genome are not readily accessible for FNR binding. Genome accessibility may also explain our finding that genome-wide FNR occupancy did not correlate with the match to consensus at binding sites, suggesting that significant variation in ChIP signal was attributable to cross-linking or immunoprecipitation efficiency rather than differences in binding affinities for FNR sites. Correlation of FNR ChIP-seq peaks with transcriptomic data showed that less than half of the FNR-regulated operons could be attributed to direct FNR binding. Conversely, FNR bound some promoters without regulating expression presumably requiring changes in activity of condition-specific transcription factors. Such combinatorial regulation may allow Escherichia coli to respond rapidly to environmental changes and confer an ecological advantage in the anaerobic but nutrient-fluctuating environment of the mammalian gut. Regulation of gene expression by transcription factors (TFs) is key to adaptation to environmental changes. Our comprehensive, genome-scale analysis of a prototypical global TF, the anaerobic regulator FNR from Escherichia coli, leads to several novel and unanticipated insights into the influences on FNR binding genome-wide and the complex structure of bacterial regulons. We found that binding of NAPs restricts FNR binding at a subset of sites, suggesting that the bacterial genome is not freely accessible for FNR binding. Our finding that less than half of the predicted FNR binding sites were occupied in vivo further challenges the utility of using bioinformatic searches alone to predict regulon structure, reinforcing the need for experimental determination of TF binding. By correlating the occupancy data with transcriptomic data, we confirm that FNR serves as a global signal of anaerobiosis but expression of some operons in the FNR regulon require other regulators sensitive to alternative environmental stimuli. Thus, FNR binding and regulation appear to depend on both the nucleoprotein structure of the chromosome and on combinatorial binding of FNR with other regulators. Both of these phenomena are typical of TF binding in eukaryotes; our results establish that they are also features of bacterial TF binding.
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Affiliation(s)
- Kevin S. Myers
- Microbiology Doctoral Training Program, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
- Department of Biomolecular Chemistry, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Huihuang Yan
- Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Irene M. Ong
- Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Dongjun Chung
- Department of Statistics, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Kun Liang
- Department of Statistics, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
- Department of Biostatistics and Medical Informatics, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Frances Tran
- Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Sündüz Keleş
- Department of Statistics, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
- Department of Biostatistics and Medical Informatics, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Robert Landick
- Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
- Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
- Department of Bacteriology, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
- * E-mail: (RL); (PJK)
| | - Patricia J. Kiley
- Department of Biomolecular Chemistry, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
- Great Lakes Bioenergy Research Center, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
- * E-mail: (RL); (PJK)
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Brucella BioR regulator defines a complex regulatory mechanism for bacterial biotin metabolism. J Bacteriol 2013; 195:3451-67. [PMID: 23729648 DOI: 10.1128/jb.00378-13] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The enzyme cofactor biotin (vitamin H or B7) is an energetically expensive molecule whose de novo biosynthesis requires 20 ATP equivalents. It seems quite likely that diverse mechanisms have evolved to tightly regulate its biosynthesis. Unlike the model regulator BirA, a bifunctional biotin protein ligase with the capability of repressing the biotin biosynthetic pathway, BioR has been recently reported by us as an alternative machinery and a new type of GntR family transcriptional factor that can repress the expression of the bioBFDAZ operon in the plant pathogen Agrobacterium tumefaciens. However, quite unusually, a closely related human pathogen, Brucella melitensis, has four putative BioR-binding sites (both bioR and bioY possess one site in the promoter region, whereas the bioBFDAZ [bio] operon contains two tandem BioR boxes). This raised the question of whether BioR mediates the complex regulatory network of biotin metabolism. Here, we report that this is the case. The B. melitensis BioR ortholog was overexpressed and purified to homogeneity, and its solution structure was found to be dimeric. Functional complementation in a bioR isogenic mutant of A. tumefaciens elucidated that Brucella BioR is a functional repressor. Electrophoretic mobility shift assays demonstrated that the four predicted BioR sites of Brucella plus the BioR site of A. tumefaciens can all interact with the Brucella BioR protein. In a reporter strain that we developed on the basis of a double mutant of A. tumefaciens (the ΔbioR ΔbioBFDA mutant), the β-galactosidase (β-Gal) activity of three plasmid-borne transcriptional fusions (bioBbme-lacZ, bioYbme-lacZ, and bioRbme-lacZ) was dramatically decreased upon overexpression of Brucella bioR. Real-time quantitative PCR analyses showed that the expression of bioBFDA and bioY is significantly elevated upon removal of bioR from B. melitensis. Together, we conclude that Brucella BioR is not only a negative autoregulator but also a repressor of expression of bioY and bio operons that separately function in biotin transport and the biosynthesis pathway.
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Feng Y, Zhang H, Cronan JE. Profligate biotin synthesis in α-proteobacteria - a developing or degenerating regulatory system? Mol Microbiol 2013; 88:77-92. [PMID: 23387333 DOI: 10.1111/mmi.12170] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/01/2013] [Indexed: 11/29/2022]
Abstract
Biotin (vitamin H) is a key enzyme cofactor required in all three domains of life. Although this cofactor was discovered over 70 years ago and has long been recognized as an essential nutrient for animals, our knowledge of the strategies bacteria use to sense biotin demand is very limited. The paradigm mechanism is that of Escherichia coli in which BirA protein, the prototypical bi-functional biotin protein ligase, both covalently attaches biotin to the acceptor proteins of central metabolism and represses transcription of the biotin biosynthetic pathway in response to biotin demand. However, in other bacteria the biotin protein ligase lacks a DNA-binding domain which raises the question of how these bacteria regulate the synthesis of biotin, an energetically expensive molecule. A bioinformatic study by Rodionov and Gelfand identified a protein termed BioR in α-proteobacteria and predicted that BioR would have the biotin operon regulatory role that in most other bacteria is fulfilled by the BirA DNA-binding domain. We have now tested this prediction in the plant pathogen Agrobacterium tumefaciens. As predicted the A. tumefaciens biotin protein ligase is a fully functional ligase that has no role in regulation of biotin synthesis whereas BioR represses transcription of the biotin synthesis genes. Moreover, as determined by electrophoretic mobility shift assays, BioR binds the predicted operator site, which is located downstream of the mapped transcription start site. qPCR measurements indicated that deletion of BioR resulted in a c. 15-fold increase of bio operon transcription in the presence of high biotin levels. Effective repression of a plasmid-borne bioB-lacZ reporter was seen only upon the overproduction of BioR. In contrast to E. coli and Bacillus subtilis where biotin synthesis is tightly controlled, A. tumefaciens synthesizes much more biotin than needed for modification of the biotin-requiring enzymes. Protein-bound biotin constitutes only about 0.5% of the total biotin, most of which is found in the culture medium. To the best of our knowledge, A. tumefaciens represents the first example of profligate biotin synthesis by a wild type bacterium.
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Affiliation(s)
- Youjun Feng
- Department of Microbiology, University of Illinois, Urbana, IL 61801, USA
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Biswas RK, Dutta D, Tripathi A, Feng Y, Banerjee M, Singh BN. Identification and characterization of Rv0494: a fatty acid-responsive protein of the GntR/FadR family from Mycobacterium tuberculosis. MICROBIOLOGY-SGM 2013; 159:913-923. [PMID: 23475950 DOI: 10.1099/mic.0.066654-0] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Escherichia coli FadR, a member of the GntR family of transcription factors, plays dual roles in fatty acid metabolism. FadR-DNA binding is inhibited by fatty acyl-CoAs, and thus FadR acts as a sensor of the fatty acid level in bacteria. We have identified FadR-binding sites in the upstream regions of genes showing altered expression after the disruption of fatty acid biosynthesis in Mycobacterium tuberculosis. A FadR homologue in M. tuberculosis, Rv0494, was identified, which binds to its operator in the upstream region of the kas operon. We have shown that FadRMt (Rv0494) directly binds to long-chain fatty acyl-CoA and that binding quenches the intrinsic fluorescence of the purified protein. FadR-DNA binding can be impaired by long-chain fatty acyl-CoA compounds. Overexpression of Rv0494 in Mycobacterium bovis BCG reduced the basal level expression of kas operon genes, thereby suggesting the repressor nature of this protein in fatty acid synthase II regulation. This is the first report, to the best of our knowledge, of a GntR/FadR family protein acting as a fatty acid-responsive transcriptional regulator in M. tuberculosis, suggesting a possible role for this protein in mycolic acid biosynthesis.
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Affiliation(s)
- Rajesh Kumar Biswas
- Division of Microbiology, CSIR-Central Drug Research Institute, Lucknow, 226021, India
| | - Debashis Dutta
- Division of Microbiology, CSIR-Central Drug Research Institute, Lucknow, 226021, India
| | - Ashutosh Tripathi
- Division of Microbiology, CSIR-Central Drug Research Institute, Lucknow, 226021, India
| | - Youjun Feng
- Department of Microbiology, University of Illinois, Urbana, Illinois, USA
| | - Monisha Banerjee
- Department of Zoology, Lucknow University, Lucknow, 226007, India
| | - Bhupendra N Singh
- Division of Microbiology, CSIR-Central Drug Research Institute, Lucknow, 226021, India
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Barzantny H, Guttmann S, Lässig C, Brune I, Tauch A. Transcriptional control of lipid metabolism by the MarR-like regulator FamR and the global regulator GlxR in the lipophilic axilla isolate Corynebacterium jeikeium K411. Microb Biotechnol 2012; 6:118-30. [PMID: 23163914 PMCID: PMC3917454 DOI: 10.1111/1751-7915.12004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2012] [Revised: 10/12/2012] [Accepted: 10/13/2012] [Indexed: 11/28/2022] Open
Abstract
Corynebacterial fatty acid metabolism has been associated with human body odour, and is therefore discussed as a potential target for the development of new deodorant additives. For this reason, the transcription levels of fad genes associated with lipid metabolism in the axilla isolate Corynebacterium jeikeium were analysed during growth on different lipid sources. The transcription of several fad genes was induced two- to ninefold in the presence of Tween 60, including the acyl-CoA dehydrogenase gene fadE6. DNA affinity chromatography identified the MarR-like protein FamR as candidate regulator of fadE6. DNA band shift assays and in vivo reporter gene fusions confirmed the direct interaction of FamR with the mapped fadE6 promoter region. Moreover, DNA affinity chromatography and DNA band shift assays detected the binding of GlxR to the promoter regions of fadE6 and famR, revealing a hierarchical control of fadE6 transcription by a feed-forward loop. Binding of GlxR and FamR to additional fad gene regions was demonstrated in vitro by DNA band shift assays, resulting in the co-regulation of fadA, fadD, fadE and fadH genes. These results shed first light on the hierarchical transcriptional control of lipid metabolism in C. jeikeium, a pathway associated with the development of human axillary odour.
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Affiliation(s)
- Helena Barzantny
- Institut für Genomforschung und Systembiologie, Centrum für Biotechnologie, Universität Bielefeld, Bielefeld, Germany.
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Attenuation of Streptococcus suis virulence by the alteration of bacterial surface architecture. Sci Rep 2012; 2:710. [PMID: 23050094 PMCID: PMC3464449 DOI: 10.1038/srep00710] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2012] [Accepted: 09/14/2012] [Indexed: 01/09/2023] Open
Abstract
NeuB, a sialic acid synthase catalyzes the last committed step of the de novo biosynthetic pathway of sialic acid, a major element of bacterial surface structure. Here we report a functional NeuB homologue of Streptococcus suis, a zoonotic agent, and systematically address its molecular and immunological role in bacterial virulence. Disruption of neuB led to thinner capsules and more susceptibility to pH, and cps2B inactivation resulted in complete absence of capsular polysaccharides. These two mutants both exhibited increased adhesion and invasion to Hep-2 cells and improved sensibility to phagocytosis. Not only do they retain the capability of inducing the release of host pro-inflammatory cytokines, but also result in the faster secretion of IL-8. Easier cleaning up of the mutant strains in whole blood is consistent with virulence attenuation seen with experimental infections of both mice and SPF-piglets. Therefore we concluded that altered architecture of S. suis surface attenuates its virulence.
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Feng Y, Cronan JE. Crosstalk of Escherichia coli FadR with global regulators in expression of fatty acid transport genes. PLoS One 2012; 7:e46275. [PMID: 23029459 PMCID: PMC3460868 DOI: 10.1371/journal.pone.0046275] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2012] [Accepted: 08/29/2012] [Indexed: 02/03/2023] Open
Abstract
Escherichia coli FadR plays two regulatory roles in fatty acid metabolism. FadR represses the fatty acid degradation (fad) system and activates the unsaturated fatty acid synthetic pathway. Cross-talk between E. coli FadR and the ArcA-ArcB oxygen-responsive two-component system was observed that resulted in diverse regulation of certain fad regulon β-oxidation genes. We have extended such analyses to the fadL and fadD genes, the protein products of which are required for long chain fatty acid transport and have also studied the role of a third global regulator, the CRP-cAMP complex. The promoters of both the fadL and fadD genes contain two experimentally validated FadR-binding sites plus binding sites for ArcA and CRP-cAMP. Despite the presence of dual binding sites FadR only modestly regulates expression of these genes, indicating that the number of binding sites does not determine regulatory strength. We report complementary in vitro and in vivo studies indicating that the CRP-cAMP complex directly activates expression of fadL and fadD as well as the β-oxidation gene, fadH. The physiological relevance of the fadL and fadD transcription data was validated by direct assays of long chain fatty acid transport.
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Affiliation(s)
- Youjun Feng
- Department of Microbiology, University of Illinois, Urbana, Illinois, United States of America
| | - John E. Cronan
- Department of Microbiology, University of Illinois, Urbana, Illinois, United States of America
- Department of Biochemistry, University of Illinois, Urbana, Illinois, United States of America
- * E-mail:
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Wada T, Hatamoto Y, Kutsukake K. Functional and expressional analyses of the anti-FlhD4C2 factor gene ydiV in Escherichia coli. MICROBIOLOGY-SGM 2012; 158:1533-1542. [PMID: 22461489 DOI: 10.1099/mic.0.056036-0] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Although Escherichia coli and Salmonella enterica serovar Typhimurium have a similar flagellar regulatory system, the response of flagellar synthesis to nutrient conditions is quite different between the two: that is, in low-nutrient conditions, flagellar synthesis is inhibited in Salmonella and enhanced in E. coli. In Salmonella, this inhibition is mediated by an anti-FlhD(4)C(2) factor, YdiV, which is expressed in low-nutrient conditions and binds to FlhD(4)C(2) to inhibit the expression of the class 2 flagellar genes. The fliZ gene encodes a repressor of the ydiV gene, and thus is required for efficient flagellar gene expression in low-nutrient conditions in Salmonella. In this study, we showed that the E. coli ydiV gene encodes a protein which inhibits motility and flagellar production when expressed from a multicopy plasmid. We showed further that E. coli YdiV binds to FlhD(4)C(2) and inhibits its binding to the class 2 flagellar promoter. These results indicate that E. coli YdiV can also act as an anti-FlhD(4)C(2) factor. However, although the ydiV gene was transcribed efficiently in E. coli cells, the intracellular level of the YdiV protein was extremely low due to its inefficient translation. Consistent with this, E. coli cells did not require FliZ for efficient motility development. This indicates that, unlike in Salmonella, the FliZ-YdiV regulatory system does not work in the nutritional control of flagellar gene expression in E. coli.
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Affiliation(s)
- Takeo Wada
- Graduate School of Natural Science and Technology and Department of Biology, Faculty of Science, Okayama University, Tsushima-Naka 3-1-1, Kita-ku, Okayama 700-8530, Japan
| | - Yuki Hatamoto
- Graduate School of Natural Science and Technology and Department of Biology, Faculty of Science, Okayama University, Tsushima-Naka 3-1-1, Kita-ku, Okayama 700-8530, Japan
| | - Kazuhiro Kutsukake
- Graduate School of Natural Science and Technology and Department of Biology, Faculty of Science, Okayama University, Tsushima-Naka 3-1-1, Kita-ku, Okayama 700-8530, Japan
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Bi H, Christensen QH, Feng Y, Wang H, Cronan JE. The Burkholderia cenocepacia BDSF quorum sensing fatty acid is synthesized by a bifunctional crotonase homologue having both dehydratase and thioesterase activities. Mol Microbiol 2012; 83:840-55. [PMID: 22221091 DOI: 10.1111/j.1365-2958.2012.07968.x] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Signal molecules of the diffusible signal factor (DSF) family have been shown recently to be involved in regulation of pathogenesis and biofilm formation in diverse Gram-negative bacteria. DSF signals are reported to be active not only on their cognate bacteria, but also on unrelated bacteria and the pathogenic yeast, Candida albicans. DSFs are monounsaturated fatty acids of medium chain length containing an unusual cis-2 double bond. Although genetic analyses had identified genes involved in DSF synthesis, the pathway of DSF synthesis was unknown. The DSF of the important human pathogen Burkholderia cenocepacia (called BDSF) is cis-2-dodecenoic acid. We report that BDSF is synthesized from a fatty acid synthetic intermediate, the acyl carrier protein (ACP) thioester of 3-hydroxydodecanoic acid. This intermediate is intercepted by protein Bcam0581 and converted to cis-2-dodecenoyl-ACP. Bcam0581 is annotated as a homologue of crotonase, the first enzyme of the fatty acid degradation pathway. We demonstrated Bcam0581to be a bifunctional protein that not only catalysed dehydration of 3-hydroxydodecanoyl-ACP to cis-2-dodecenoyl-ACP, but also cleaved the thioester bond to give the free acid. Both activities required the same set of active-site residues. Although dehydratase and thioesterase activities are known activities of the crotonase superfamily, Bcam0581 is the first protein shown to have both activities.
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Affiliation(s)
- Hongkai Bi
- Departments of Microbiology Biochemistry, B103 Chemical and Life Sciences Laboratory, University of Illinois, 601 S. Goodwin Ave, Urbana, IL 61801, USA
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Cao M, Feng Y, Wang C, Zheng F, Li M, Liao H, Mao Y, Pan X, Wang J, Hu D, Hu F, Tang J. Functional definition of LuxS, an autoinducer-2 (AI-2) synthase and its role in full virulence of Streptococcus suis serotype 2. J Microbiol 2011; 49:1000-11. [PMID: 22203565 DOI: 10.1007/s12275-011-1523-1] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2011] [Accepted: 12/13/2011] [Indexed: 12/22/2022]
Abstract
Quorum sensing is a widespread chemical communication in response to fluctuation of bacterial population density, and has been implicated into bacterial biofilm formation and regulation of expression of virulence factors. The luxS gene product, S-ribosylhomocysteinase, catalizes the last committed step in biosynthetic pathway of autoinducer 2 (AI-2), a signaling molecule for inter-species quorum sensing. We found a luxS homologue in 05ZYH33, an epidemic strain of Streptococcus suis serotype 2 (SS2) in China. A luxS null mutant (ΔluxS) of 05ZYH33 strain was obtained using an approach of homologous recombination. LuxS was determined to be required for AI-2 production in 05ZYH33 strain of S. suis 2. Inactivation of luxS gene led to a wide range of phenotypic changes including thinner capsular walls, increased tolerance to H(2)O(2), reduced adherence capacity to epithelial cells, etc. In particular, loss of LuxS impaired dramatically its full virulence of SS2 in experimental model of piglets, and functional complementation restored it nearly to the level of parent strain. Genome-wide transcriptome analyses suggested that some known virulence factors such as CPS are down-regulated in the ΔluxS mutant, which might in part explain virulence attenuation by luxS deletion. Similarly, 29 of 71 genes with different expression level were proposed to be targets candidate regulated by LuxS/AI-2-dependent quorum sensing.
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Affiliation(s)
- Min Cao
- Department of Microbiology, Third Military Medical University, Chongqing, P. R. China
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Nannenga BL, Baneyx F. Enhanced expression of membrane proteins in E. coli with a P(BAD) promoter mutant: synergies with chaperone pathway engineering strategies. Microb Cell Fact 2011; 10:105. [PMID: 22151946 PMCID: PMC3265434 DOI: 10.1186/1475-2859-10-105] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2011] [Accepted: 12/09/2011] [Indexed: 11/10/2022] Open
Abstract
Background Membrane proteins (MPs) populate 20-30% of genomes sequenced to date and hold potential as therapeutic targets as well as for practical applications in bionanotechnology. However, MP toxicity and low yields in normally robust expression hosts such as E. coli has curtailed progress in our understanding of their structure and function. Results Using the seven transmembrane segments H. turkmenica deltarhodopsin (HtdR) as a reporter, we isolated a spontaneous mutant in the arabinose-inducible PBAD promoter leading to improved cell growth and a twofold increase in the recovery of active HtdR at 37°C. A single transversion in a conserved region of the cyclic AMP receptor protein binding site caused the phenotype by reducing htdR transcript levels by 65%. When the mutant promoter was used in conjunction with a host lacking the molecular chaperone Trigger Factor (Δtig cells), toxicity was further suppressed and the amount of correctly folded HtdR was 4-fold that present in the membranes of control cells. More importantly, while improved growth barely compensated for the reduction in transcription rates when another polytopic membrane protein (N. pharonis sensory rhodopsin II) was expressed under control of the mutant promoter in wild type cells, a 4-fold increase in productivity could be achieved in a Δtig host. Conclusions Our system, which combines a downregulated version of the tightly repressed PBAD promoter with a TF-deficient host may prove a valuable alternative to T7-based expression for the production of membrane proteins that have so far remained elusive targets.
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Affiliation(s)
- Brent L Nannenga
- Department of Chemical Engineering, University of Washington, Seattle, WA 98195-1750, USA
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Peng H, Feng Y, Zhu X, Lan X, Tang M, Wang J, Dong H, Chen B. MoDUO1, a Duo1-like gene, is required for full virulence of the rice blast fungus Magnaporthe oryzae. Curr Genet 2011; 57:409-20. [DOI: 10.1007/s00294-011-0355-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2011] [Revised: 08/04/2011] [Accepted: 08/21/2011] [Indexed: 10/17/2022]
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Feng Y, Cronan JE. The Vibrio cholerae fatty acid regulatory protein, FadR, represses transcription of plsB, the gene encoding the first enzyme of membrane phospholipid biosynthesis. Mol Microbiol 2011; 81:1020-33. [PMID: 21771112 DOI: 10.1111/j.1365-2958.2011.07748.x] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Glycerol-3-phosphate (sn-glycerol-3-P, G3P) acyltransferase catalyses the first committed step in the biosynthesis of membrane phospholipids, the acylation of G3P to form 1-acyl G3P (lysophosphatidic acid). The paradigm G3P acyltransferase is the Escherichia coli plsB gene product which acylates position-1 of G3P using fatty acids in thioester linkage to either acyl carrier protein (ACP) or CoA as acyl donors. Although the E. coli plsB gene was discovered about 30 years ago, no evidence for transcriptional control of its expression has been reported. However A.E. Kazakov and co-workers (J Bacteriol 2009; 191: 52-64) reported the presence of a putative FadR binding site upstream of the candidate plsB genes of Vibrio cholerae and three other Vibrio species suggesting that plsB might be regulated by FadR, a GntR family transcription factor thus far known only to regulate fatty acid synthesis and degradation. We report that the V. cholerae plsB homologue restored growth of E. coli strain BB26-36 which is a G3P auxotroph due to an altered G3P acyltransferase activity. The plsB promoter was also mapped and the predicted FadR-binding palindrome was found to span positions -19 to -35, upstream of the transcription start site. Gel shift assays confirmed that both V. cholerae FadR and E. coli FadR bound the V. cholerae plsB promoter region and binding was reversed upon addition of long-chain fatty acyl-CoA thioesters. The expression level of the V. cholerae plsB gene was elevated two- to threefold in an E. coli fadR null mutant strain indicating that FadR acts as a repressor of V. cholerae plsB expression. In both E. coli and V. cholerae the β-galactosidase activity of transcriptional fusions of the V. cholerae plsB promoter to lacZ increased two- to threefold upon supplementation of growth media with oleic acid. Therefore, V. cholerae co-ordinates fatty acid metabolism with 1-acyl G3P synthesis.
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Affiliation(s)
- Youjun Feng
- Department of Microbiology, University of Illinois, Urbana, IL 61801, USA
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Agari Y, Agari K, Sakamoto K, Kuramitsu S, Shinkai A. TetR-family transcriptional repressor Thermus thermophilus FadR controls fatty acid degradation. MICROBIOLOGY-SGM 2011; 157:1589-1601. [PMID: 21349973 DOI: 10.1099/mic.0.048017-0] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
In the extremely thermophilic bacterium Thermus thermophilus HB8, one of the four TetR-family transcriptional regulators, which we named T. thermophilus FadR, negatively regulated the expression of several genes, including those involved in fatty acid degradation, both in vivo and in vitro. T. thermophilus FadR repressed the expression of the target genes by binding pseudopalindromic sequences covering the predicted -10 hexamers of their promoters, and medium-to-long straight-chain (C10-18) fatty acyl-CoA molecules were effective for transcriptional derepression. An X-ray crystal structure analysis revealed that T. thermophilus FadR bound one lauroyl (C12)-CoA molecule per FadR monomer, with its acyl chain moiety in the centre of the FadR molecule, enclosed within a tunnel-like substrate-binding pocket surrounded by hydrophobic residues, and the CoA moiety interacting with basic residues on the protein surface. The growth of T. thermophilus HB8, with palmitic acid as the sole carbon source, increased the expression of FadR-regulated genes. These results indicate that in T. thermophilus HB8, medium-to-long straight-chain fatty acids can be used for metabolic energy under the control of FadR, although the major fatty acids found in this strain are iso- and anteiso-branched-chain (C15 and 17) fatty acids.
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Affiliation(s)
- Yoshihiro Agari
- RIKEN SPring-8 Center, Harima Institute, 1-1-1 Kouto, Sayo, Hyogo 679-5148, Japan
| | - Kazuko Agari
- RIKEN SPring-8 Center, Harima Institute, 1-1-1 Kouto, Sayo, Hyogo 679-5148, Japan
| | - Keiko Sakamoto
- RIKEN SPring-8 Center, Harima Institute, 1-1-1 Kouto, Sayo, Hyogo 679-5148, Japan
| | - Seiki Kuramitsu
- Department of Biological Sciences, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan.,RIKEN SPring-8 Center, Harima Institute, 1-1-1 Kouto, Sayo, Hyogo 679-5148, Japan
| | - Akeo Shinkai
- RIKEN SPring-8 Center, Harima Institute, 1-1-1 Kouto, Sayo, Hyogo 679-5148, Japan
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Feng Y, Cronan JE. Complex binding of the FabR repressor of bacterial unsaturated fatty acid biosynthesis to its cognate promoters. Mol Microbiol 2011; 80:195-218. [PMID: 21276098 DOI: 10.1111/j.1365-2958.2011.07564.x] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Two transcriptional regulators, the FadR activator and the FabR repressor, control biosynthesis of unsaturated fatty acids in Escherichia coli. FabR represses expression of the two genes, fabA and fabB, required for unsaturated fatty acid synthesis and has been reported to require the presence of an unsaturated thioester (of either acyl carrier protein or CoA) in order to bind the fabA and fabB promoters in vitro. We report in vivo experiments in which unsaturated fatty acid synthesis was blocked in the absence of exogenous unsaturated fatty acids in a ΔfadR strain and found that the rates of transcription of fabA and fabB were unaffected by the lack of unsaturated thioesters. To examine the discrepancy between our in vivo results and the prior in vitro results we obtained active, natively folded forms of the E. coli and Vibrio cholerae FabRs by use of an in vitro transcription-translation system. We report that FabR bound the intact promoter regions of both fabA and fabB in the absence of unsaturated acyl thioesters, but bound the two promoters differently. Native FabR bound the fabA promoter region provided that the canonical FabR binding site is extended by inclusion of flanking sequences that overlap the neighbouring FadR binding site. In contrast, although binding to the fabB operator also required a flanking sequence, a non-specific sequence could suffice. However, unsaturated thioesters did allow FabR binding to the minimal FabR operator sites of both promoters which otherwise were not bound. Thus unsaturated thioester ligands were not essential for FabR/target DNA interaction, but acted to enhance binding. The gel mobility shift data plus in vivo expression data indicate that despite the remarkably similar arrangements of promoter elements, FadR predominately regulates fabA expression whereas FabR is the dominant regulator of fabB expression. We also report that E. coli fabR expression is not autoregulated. Complementation, qRT-PCR and fatty acid composition analyses demonstrated that V. cholerae FabR was a functional repressor of unsaturated fatty acid synthesis. However, in contrast to E. coli, gel mobility shift assays indicated that neither E. coli nor V. cholerae FabRs bound the V. cholerae fabB promoter, although both proteins efficiently bound the V. cholerae fabA promoter. This asymmetry was shown to be due to the lack of a FabR binding site within the V. cholerae fabB promoter region.
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Affiliation(s)
- Youjun Feng
- Department of Microbiology, University of Illinois, Urbana, IL 61801, USA
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Escherichia coli glycogen genes are organized in a single glgBXCAP transcriptional unit possessing an alternative suboperonic promoter within glgC that directs glgAP expression. Biochem J 2011; 433:107-17. [PMID: 21029047 DOI: 10.1042/bj20101186] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Although it is generally accepted that Escherichia coli glycogen genes are organized in two tandemly arranged, differentially regulated glgBX and glgCAP operons, RT (reverse transcriptase)-PCR analyses carried out in the present study showed that E. coli cells possess transcripts comprising the five glgBXCAP genes. glg::lacZY expression analyses in cells lacking the region immediately upstream of the glgB gene revealed an almost total abolishment of glgB, glgX and glgC expression, but only a 50-60% reduction of the wild-type glgA and glgP expression levels. Furthermore, similar analyses showed that glgA and glgP expression was almost totally abolished in cells lacking glgA upstream sequences, including glgC, glgB and the asd-glgB intergenic region upstream of glgB. These results indicate that E. coli glgBXCAP genes are organized in a single transcriptional unit controlled by promoter sequences occurring upstream of glgB, and that an alternative suboperonic promoter is located within glgC, driving expression of the glgA and glgP genes. Computer searches for consensus promoters, and analyses of glgB::lacZY and glgA::lacZY expression in cells containing deletions of glgB and glgA upstream sequences identified regions directing glgBXCAP and glgAP expression. 5' RACE (rapid amplification of cDNA ends) analyses located a glgBXCAP transcription start site 155 bp upstream of the glgB initiation codon, and a glgAP transcription start site 359 bp upstream of the glgA initiation codon. Finally, glg::lacZY expression analyses on cells lacking the relA or phoP regulatory genes indicated that both the glgBXCAP operon and the suboperonic promoter driving glgAP expression form part of both the RelA and PhoP-PhoQ regulons.
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