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Bin P, Liu W, Zhang X, Liu B, Zhu G. A novel antibacterial strategy for targeting the bacterial methionine biosynthesis pathway. Int J Antimicrob Agents 2024; 63:107057. [PMID: 38072168 DOI: 10.1016/j.ijantimicag.2023.107057] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2023] [Revised: 11/28/2023] [Accepted: 12/05/2023] [Indexed: 01/25/2024]
Abstract
Bacterial pathogens reprogramme their metabolic networks to support growth and establish infection at specific sites. Bacterial central metabolism has been considered attractive for developing antimicrobial drugs; however, most metabolic enzymes are conserved between humans and bacteria. This study found that blockade of methionine biosynthesis in Citrobacter rodentium and Salmonella enteritidis inhibited bacterial growth and activity of the type III secretion system, resulting in severe defects in colonization and pathogenicity. In addition, α-methyl-methionine was found to inhibit the activity of methionine biosynthetic enzyme MetA, and consequently reduce the virulence and pathogenicity of enteric pathogens. These findings highlight the crucial role of methionine in bacterial virulence, and describe a potential new drug target.
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Affiliation(s)
- Peng Bin
- College of Veterinary Medicine, Yangzhou University, Yangzhou, China; Joint Laboratory of International Cooperation on Prevention and Control Technology of Important Animal Diseases and Zoonoses of Jiangsu Higher Education Institutions, Yangzhou University, Yangzhou, Jiangsu, China; Jiangsu Co-Innovation Centre for Important Animal Infectious Diseases and Zoonoses, Joint International Research Laboratory of Agriculture and AgriProduct Safety of Ministry of Education of China, College of Veterinary Medicine, Yangzhou University, Yangzhou, China; College of Animal Science, South China Agricultural University, Guangzhou, China
| | - Wanyang Liu
- College of Veterinary Medicine, Yangzhou University, Yangzhou, China; Joint Laboratory of International Cooperation on Prevention and Control Technology of Important Animal Diseases and Zoonoses of Jiangsu Higher Education Institutions, Yangzhou University, Yangzhou, Jiangsu, China; Jiangsu Co-Innovation Centre for Important Animal Infectious Diseases and Zoonoses, Joint International Research Laboratory of Agriculture and AgriProduct Safety of Ministry of Education of China, College of Veterinary Medicine, Yangzhou University, Yangzhou, China
| | - Xiaojie Zhang
- College of Veterinary Medicine, Yangzhou University, Yangzhou, China; Joint Laboratory of International Cooperation on Prevention and Control Technology of Important Animal Diseases and Zoonoses of Jiangsu Higher Education Institutions, Yangzhou University, Yangzhou, Jiangsu, China; Jiangsu Co-Innovation Centre for Important Animal Infectious Diseases and Zoonoses, Joint International Research Laboratory of Agriculture and AgriProduct Safety of Ministry of Education of China, College of Veterinary Medicine, Yangzhou University, Yangzhou, China
| | - Baobao Liu
- College of Veterinary Medicine, Yangzhou University, Yangzhou, China; Joint Laboratory of International Cooperation on Prevention and Control Technology of Important Animal Diseases and Zoonoses of Jiangsu Higher Education Institutions, Yangzhou University, Yangzhou, Jiangsu, China; Jiangsu Co-Innovation Centre for Important Animal Infectious Diseases and Zoonoses, Joint International Research Laboratory of Agriculture and AgriProduct Safety of Ministry of Education of China, College of Veterinary Medicine, Yangzhou University, Yangzhou, China
| | - Guoqiang Zhu
- College of Veterinary Medicine, Yangzhou University, Yangzhou, China; Joint Laboratory of International Cooperation on Prevention and Control Technology of Important Animal Diseases and Zoonoses of Jiangsu Higher Education Institutions, Yangzhou University, Yangzhou, Jiangsu, China; Jiangsu Co-Innovation Centre for Important Animal Infectious Diseases and Zoonoses, Joint International Research Laboratory of Agriculture and AgriProduct Safety of Ministry of Education of China, College of Veterinary Medicine, Yangzhou University, Yangzhou, China.
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El Zahed SS, Brown ED. Chemical-Chemical Combinations Map Uncharted Interactions in Escherichia coli under Nutrient Stress. iScience 2018; 2:168-181. [PMID: 30428373 PMCID: PMC6136904 DOI: 10.1016/j.isci.2018.03.018] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2017] [Revised: 02/28/2018] [Accepted: 03/07/2018] [Indexed: 11/16/2022] Open
Abstract
Of the ∼4,400 genes that constitute Escherichia coli's genome, ∼300 genes are indispensable for its growth in nutrient-rich conditions. These encode housekeeping functions, including cell wall, DNA, RNA, and protein syntheses. Under conditions in which nutrients are limited to a carbon source, nitrogen source, essential phosphates, and salts, more than 100 additional genes become essential. These largely code for the synthesis of amino acids, vitamins, and nucleobases. Although much is known about this collection of ∼400 genes, their interactions under nutrient stress are uncharted. Using a chemical biology approach, we focused on 45 chemical probes targeting encoded proteins in this collection and mapped their interactions under nutrient-limited conditions. Encompassing 990 unique pairwise chemical combinations, we revealed a highly connected network of 186 interactions, of which 81 were synergistic and 105 were antagonistic. The network revealed signature interactions for each probe and highlighted new connectivity between housekeeping functions and those essential in nutrient stress. Chemical probes map a complex interaction network in E. coli under nutrient stress A total of 990 unique chemical combinations reveal a dense network of 186 interactions New connections between housekeeping functions and those in nutrient stress
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Affiliation(s)
- Sara S El Zahed
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON L8N 3Z5, Canada; Michael G. DeGroote Institute of Infectious Disease Research, McMaster University, Hamilton, ON L8N 3Z5, Canada
| | - Eric D Brown
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON L8N 3Z5, Canada; Michael G. DeGroote Institute of Infectious Disease Research, McMaster University, Hamilton, ON L8N 3Z5, Canada.
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Gehrke SS, Kumar G, Yokubynas NA, Côté JP, Wang W, French S, MacNair CR, Wright GD, Brown ED. Exploiting the Sensitivity of Nutrient Transporter Deletion Strains in Discovery of Natural Product Antimetabolites. ACS Infect Dis 2017; 3:955-965. [PMID: 29069544 DOI: 10.1021/acsinfecdis.7b00149] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Actinomycete secondary metabolites are a renowned source of antibacterial chemical scaffolds. Herein, we present a target-specific approach that increases the detection of antimetabolites from natural sources by screening actinomycete-derived extracts against nutrient transporter deletion strains. On the basis of the growth rescue patterns of a collection of 22 Escherichia coli (E. coli) auxotrophic deletion strains representative of the major nutrient biosynthetic pathways, we demonstrate that antimetabolite detection from actinomycete-derived extracts prepared using traditional extraction platforms is masked by nutrient supplementation. In particular, we find poor sensitivity for the detection of antimetabolites targeting vitamin biosynthesis. To circumvent this and as a proof of principle, we exploit the differential activity of actinomycete extracts against E. coli ΔyigM, a biotin transporter deletion strain versus wildtype E. coli. We achieve more than a 100-fold increase in antimetabolite sensitivity using this method and demonstrate a successful bioassay-guided purification of the known biotin antimetabolite, amiclenomycin. Our findings provide a unique solution to uncover the full potential of naturally derived antibiotics.
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Affiliation(s)
- Sebastian S. Gehrke
- Michael G. DeGroote
Institute of Infectious Disease Research, Department of Biochemistry
and Biomedical Science, McMaster University, 1200 Main Street West, Hamilton Ontario L8N 3ZS, Canada
| | - Garima Kumar
- Michael G. DeGroote
Institute of Infectious Disease Research, Department of Biochemistry
and Biomedical Science, McMaster University, 1200 Main Street West, Hamilton Ontario L8N 3ZS, Canada
| | - Nicole A. Yokubynas
- Michael G. DeGroote
Institute of Infectious Disease Research, Department of Biochemistry
and Biomedical Science, McMaster University, 1200 Main Street West, Hamilton Ontario L8N 3ZS, Canada
| | - Jean-Philippe Côté
- Michael G. DeGroote
Institute of Infectious Disease Research, Department of Biochemistry
and Biomedical Science, McMaster University, 1200 Main Street West, Hamilton Ontario L8N 3ZS, Canada
| | - Wenliang Wang
- Michael G. DeGroote
Institute of Infectious Disease Research, Department of Biochemistry
and Biomedical Science, McMaster University, 1200 Main Street West, Hamilton Ontario L8N 3ZS, Canada
| | - Shawn French
- Michael G. DeGroote
Institute of Infectious Disease Research, Department of Biochemistry
and Biomedical Science, McMaster University, 1200 Main Street West, Hamilton Ontario L8N 3ZS, Canada
| | - Craig R. MacNair
- Michael G. DeGroote
Institute of Infectious Disease Research, Department of Biochemistry
and Biomedical Science, McMaster University, 1200 Main Street West, Hamilton Ontario L8N 3ZS, Canada
| | - Gerard D. Wright
- Michael G. DeGroote
Institute of Infectious Disease Research, Department of Biochemistry
and Biomedical Science, McMaster University, 1200 Main Street West, Hamilton Ontario L8N 3ZS, Canada
| | - Eric D. Brown
- Michael G. DeGroote
Institute of Infectious Disease Research, Department of Biochemistry
and Biomedical Science, McMaster University, 1200 Main Street West, Hamilton Ontario L8N 3ZS, Canada
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4
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Fiedurek J, Trytek M, Szczodrak J. Strain improvement of industrially important microorganisms based on resistance to toxic metabolites and abiotic stress. J Basic Microbiol 2017; 57:445-459. [DOI: 10.1002/jobm.201600710] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2016] [Accepted: 03/04/2017] [Indexed: 11/06/2022]
Affiliation(s)
- Jan Fiedurek
- Department of Industrial Microbiology; Institute of Microbiology and Biotechnology; Maria Curie-Skłodowska University; Lublin Poland
| | - Mariusz Trytek
- Department of Industrial Microbiology; Institute of Microbiology and Biotechnology; Maria Curie-Skłodowska University; Lublin Poland
| | - Janusz Szczodrak
- Department of Industrial Microbiology; Institute of Microbiology and Biotechnology; Maria Curie-Skłodowska University; Lublin Poland
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Huang JF, Liu ZQ, Jin LQ, Tang XL, Shen ZY, Yin HH, Zheng YG. Metabolic engineering of Escherichia coli for microbial production of L-methionine. Biotechnol Bioeng 2016; 114:843-851. [PMID: 27723097 DOI: 10.1002/bit.26198] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2016] [Revised: 10/04/2016] [Accepted: 10/05/2016] [Indexed: 11/08/2022]
Abstract
L-methionine has attracted a great deal of attention for its nutritional, pharmaceutical, and clinical applications. In this study, Escherichia coli W3110 was engineered via deletion of a negative transcriptional regulator MetJ and over-expression of homoserine O-succinyltransferase MetA together with efflux transporter YjeH, resulting in L-methionine overproduction which is up to 413.16 mg/L. The partial inactivation of the L-methionine import system MetD via disruption of metI made the engineered E. coli ΔmetJ ΔmetI/pTrcA*H more tolerant to high L-ethionine concentration and accumulated L-methionine to a level 43.65% higher than that of E. coli W3110 ΔmetJ/pTrcA*H. Furthermore, deletion of lysA, which blocks the lysine biosynthesis pathway, led to a further 8.5-fold increase in L-methionine titer of E. coli ΔmetJ ΔmetI ΔlysA/pTrcA*H. Finally, addition of Na2 S2 O3 to the media led to an increase of fermentation titer of 11.45%. After optimization, constructed E. coli ΔmetJ ΔmetI ΔlysA/pTrcA*H was able to produce 9.75 g/L L-methionine with productivity of 0.20 g/L/h in a 5 L bioreactor. This novel metabolically tailored strain of E. coli provides an efficient platform for microbial production of L-methionine. Biotechnol. Bioeng. 2017;114: 843-851. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Jian-Feng Huang
- Key Laboratory of Bioorganic Synthesis of Zhejiang Province, College of Biotechnology Bioengineering, Zhejiang University of Technology, Hangzhou, 310014, P. R. China.,Engineering Research Center of Bioconversion and Bio-Purification, Ministry of Education, Zhejiang University of Technology, Hangzhou, 310014, P. R. China
| | - Zhi-Qiang Liu
- Key Laboratory of Bioorganic Synthesis of Zhejiang Province, College of Biotechnology Bioengineering, Zhejiang University of Technology, Hangzhou, 310014, P. R. China.,Engineering Research Center of Bioconversion and Bio-Purification, Ministry of Education, Zhejiang University of Technology, Hangzhou, 310014, P. R. China
| | - Li-Qun Jin
- Key Laboratory of Bioorganic Synthesis of Zhejiang Province, College of Biotechnology Bioengineering, Zhejiang University of Technology, Hangzhou, 310014, P. R. China.,Engineering Research Center of Bioconversion and Bio-Purification, Ministry of Education, Zhejiang University of Technology, Hangzhou, 310014, P. R. China
| | - Xiao-Ling Tang
- Key Laboratory of Bioorganic Synthesis of Zhejiang Province, College of Biotechnology Bioengineering, Zhejiang University of Technology, Hangzhou, 310014, P. R. China.,Engineering Research Center of Bioconversion and Bio-Purification, Ministry of Education, Zhejiang University of Technology, Hangzhou, 310014, P. R. China
| | - Zhen-Yang Shen
- Key Laboratory of Bioorganic Synthesis of Zhejiang Province, College of Biotechnology Bioengineering, Zhejiang University of Technology, Hangzhou, 310014, P. R. China.,Engineering Research Center of Bioconversion and Bio-Purification, Ministry of Education, Zhejiang University of Technology, Hangzhou, 310014, P. R. China
| | - Huan-Huan Yin
- Key Laboratory of Bioorganic Synthesis of Zhejiang Province, College of Biotechnology Bioengineering, Zhejiang University of Technology, Hangzhou, 310014, P. R. China.,Engineering Research Center of Bioconversion and Bio-Purification, Ministry of Education, Zhejiang University of Technology, Hangzhou, 310014, P. R. China
| | - Yu-Guo Zheng
- Key Laboratory of Bioorganic Synthesis of Zhejiang Province, College of Biotechnology Bioengineering, Zhejiang University of Technology, Hangzhou, 310014, P. R. China.,Engineering Research Center of Bioconversion and Bio-Purification, Ministry of Education, Zhejiang University of Technology, Hangzhou, 310014, P. R. China
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Chalova VI, Kim J, Patterson PH, Ricke SC, Kim WK. Reduction of nitrogen excretion and emission in poultry: A review for organic poultry. JOURNAL OF ENVIRONMENTAL SCIENCE AND HEALTH. PART. B, PESTICIDES, FOOD CONTAMINANTS, AND AGRICULTURAL WASTES 2016; 51:230-235. [PMID: 26786395 DOI: 10.1080/03601234.2015.1120616] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Organic poultry is an alternative to conventional poultry which is rapidly developing as a response to customers' demand for better food and a cleaner environment. Although organic poultry manure can partially be utilized by organic horticultural producers, litter accumulation as well as excessive nitrogen still remains a challenge to maintain environment pureness, animal, and human health. Compared to conventional poultry, diet formulation without nitrogen overloading in organic poultry is even more complicated due to specific standards and regulations which limit the application of some supplements and imposes specific criteria to the ingredients in use. This is especially valid for methionine provision which supplementation as a crystalline form is only temporarily allowed. This review is focused on the utilization of various protein sources in the preparation of a diet composed of 100% organic ingredients which meet the avian physiology need for methionine, while avoiding protein overload. The potential to use unconventional protein sources such as invertebrates and microbial proteins to achieve optimal amino acid provision is also discussed.
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Affiliation(s)
- Vesela I Chalova
- a Department of Biochemistry and Molecular Biology , University of Food Technologies , Plovdiv , Bulgaria
| | - Jihyuk Kim
- b Department of Animal Resources Science , Kongju National University , Yesan , Chungnam , Republic of Korea
| | - Paul H Patterson
- c Department of Animal Science , Pennsylvania State University , University Park , Pennsylvania , USA
| | - Steven C Ricke
- d Center for Food Safety and Department of Food Science, University of Arkansas , Fayetteville , Arkansas , USA
| | - Woo K Kim
- e Department of Poultry Science , University of Georgia , Athens , Georgia , USA
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7
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Shim J, Shin Y, Lee I, Kim SY. l-Methionine Production. ADVANCES IN BIOCHEMICAL ENGINEERING/BIOTECHNOLOGY 2016; 159:153-177. [DOI: 10.1007/10_2016_30] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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Veeravalli K, Laird MW, Fedesco M, Zhang Y, Yu XC. Strain engineering to prevent norleucine incorporation during recombinant protein production in Escherichia coli. Biotechnol Prog 2014; 31:204-11. [PMID: 25315437 DOI: 10.1002/btpr.1999] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2014] [Revised: 10/08/2014] [Indexed: 11/07/2022]
Abstract
Incorporation of norleucine in place of methionine residues during recombinant protein production in Escherichia coli is well known. Continuous feeding of methionine is commonly used in E. coli recombinant protein production processes to prevent norleucine incorporation. Although this strategy is effective in preventing norleucine incorporation, there are several disadvantages associated with continuous feeding. Continuous feeding increases the operational complexity and the overall cost of the fermentation process. In addition, the continuous feed leads to undesirable dilution of the fermentation medium possibly resulting in lower cell densities and recombinant protein yields. In this work, the genomes of three E. coli hosts were engineered by introducing chromosomal mutations that result in methionine overproduction in the cell. The recombinant protein purified from the fermentations using the methionine overproducing hosts had no norleucine incorporation. Furthermore, these studies demonstrated that the fermentations using one of the methionine overproducing hosts exhibited comparable fermentation performance as the control host in three different recombinant protein production processes.
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Affiliation(s)
- Karthik Veeravalli
- Dept. of Late Stage Cell Culture, Genentech Inc., South San Francisco, CA, 94080
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Saengkerdsub S, Muthaiyan A, Lingbeck JM, O'Bryan CA, Crandall PG, Ricke SC. Identification and methionine analog tolerance of environmental bacterial isolates selected on methionine analog containing medium. JOURNAL OF ENVIRONMENTAL SCIENCE AND HEALTH. PART. B, PESTICIDES, FOOD CONTAMINANTS, AND AGRICULTURAL WASTES 2014; 49:290-298. [PMID: 24502216 DOI: 10.1080/03601234.2014.868668] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Methionine is the first limiting amino acid in poultry feed. Currently, methionine supplement is synthesized from an expensive chemical process requiring hazardous chemicals. Therefore, the objectives of this study were isolation of methionine producing bacteria from environmental samples and quantification of methionine production in these isolated bacteria. MCGC medium was selected as the isolation medium for methionine-producing bacteria by using Corynebacterium glutamicum ATCC13032 and Escherichia coli ATCC23798 as the positive and negative controls, respectively. Thirty-nine bacterial strains were obtained from environmental samples. Only strains A121, A122, A151 and A181 were able to tolerate up to 0.1% (w/v) of ethionine or norleucine. These isolated strains were identified by sequencing small subunit rRNA genes. The results revealed that bacterial strains A121, A122, A151and A181 were Klebsiella species, Acinetobacter baumannii, A. baumannii and Pseudomonas aeruginosa, respectively. When methionine production in strains A121 and A181 was quantitated, strains A121 and A181 generated methionine up to 31.1 and 124.6 μg/ml, respectively.
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Affiliation(s)
- Suwat Saengkerdsub
- a Center for Food Safety, and Department of Food Science , University of Arkansas , Fayetteville , Arkansas , USA
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Methionine Biosynthesis in Escherichia coli and Corynebacterium glutamicum. AMINO ACID BIOSYNTHESIS ~ PATHWAYS, REGULATION AND METABOLIC ENGINEERING 2006. [DOI: 10.1007/7171_2006_059] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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Usuda Y, Kurahashi O. Effects of deregulation of methionine biosynthesis on methionine excretion in Escherichia coli. Appl Environ Microbiol 2005; 71:3228-34. [PMID: 15933025 PMCID: PMC1151843 DOI: 10.1128/aem.71.6.3228-3234.2005] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Several regulators of methionine biosynthesis have been reported in Escherichia coli, which might represent barriers to the production of excess l-methionine (Met). In order to examine the effects of these factors on Met biosynthesis and metabolism, deletion mutations of the methionine repressor (metJ) and threonine biosynthetic (thrBC) genes were introduced into the W3110 wild-type strain of E. coli. Mutations of the metK gene encoding S-adenosylmethionine synthetase, which is involved in Met metabolism, were detected in 12 norleucine-resistant mutants. Three of the mutations in the metK structural gene were then introduced into metJ and thrBC double-mutant strains; one of the resultant strains was found to accumulate 0.13 g/liter Met. Mutations of the metA gene encoding homoserine succinyltransferase were detected in alpha-methylmethionine-resistant mutants, and these mutations were found to encode feedback-resistant enzymes in a 14C-labeled homoserine assay. Three metA mutations were introduced, using expression plasmids, into an E. coli strain that was shown to accumulate 0.24 g/liter Met. Combining mutations that affect the deregulation of Met biosynthesis and metabolism is therefore an effective approach for the production of Met-excreting strains.
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Affiliation(s)
- Yoshihiro Usuda
- Fermentation & Biotechnology Laboratories, Institute of Life Sciences, Ajinomoto Co. Inc., 1-1 Suzuki-cho, Kawasaki-ku, Kawasaki-shi 210-8681, Japan.
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Bartlem D, Lambein I, Okamoto T, Itaya A, Uda Y, Kijima F, Tamaki Y, Nambara E, Naito S. Mutation in the threonine synthase gene results in an over-accumulation of soluble methionine in Arabidopsis. PLANT PHYSIOLOGY 2000; 123:101-10. [PMID: 10806229 PMCID: PMC58986 DOI: 10.1104/pp.123.1.101] [Citation(s) in RCA: 86] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/22/1999] [Accepted: 01/25/2000] [Indexed: 05/17/2023]
Abstract
In higher plants, O-phosphohomoserine (OPH) represents a branch point between the methionine (Met) and threonine (Thr) biosynthetic pathways. It is believed that the enzymes Thr synthase (TS) and cystathionine gamma-synthase (CGS) actively compete for the OPH substrate for Thr and Met biosynthesis, respectively. We have isolated a mutant of Arabidopsis, designated mto2-1, that over-accumulates soluble Met 22-fold and contains markedly reduced levels of soluble Thr in young rosettes. The mto2-1 mutant carries a single base pair mutation within the gene encoding TS, resulting in a leucine-204 to arginine change. Accumulation of TS mRNA and protein was normal in young rosettes of mto2-1, whereas functional complementation analysis of an Escherichia coli thrC mutation suggested that the ability of mto2-1 TS to synthesize Thr is impaired. We concluded that the mutation within the TS gene is responsible for the mto2-1 phenotype, resulting in decreased Thr biosynthesis and a channeling of OPH to Met biosynthesis in young rosettes. Analysis of the mto2-1 mutant suggested that, in vivo, the feedback regulation of CGS is not sufficient alone for the control of Met biosynthesis in young rosettes and is dependent on TS activity. In addition, developmental analysis of soluble Met and Thr concentrations indicated that the accumulation of these amino acids is regulated in a temporal and spatial manner.
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Affiliation(s)
- D Bartlem
- Division of Applied Bioscience, Graduate School of Agriculture, Hokkaido University, Sapporo 060-8589, Japan
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