1
|
Kim SK, Kim H, Woo SG, Kim TH, Rha E, Kwon KK, Lee H, Lee SG, Lee DH. CRISPRi-based programmable logic inverter cascade for antibiotic-free selection and maintenance of multiple plasmids. Nucleic Acids Res 2022; 50:13155-13171. [PMID: 36511859 PMCID: PMC9825151 DOI: 10.1093/nar/gkac1104] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2022] [Revised: 10/27/2022] [Accepted: 11/03/2022] [Indexed: 12/14/2022] Open
Abstract
Antibiotics have been widely used for plasmid-mediated cell engineering. However, continued use of antibiotics increases the metabolic burden, horizontal gene transfer risks, and biomanufacturing costs. There are limited approaches to maintaining multiple plasmids without antibiotics. Herein, we developed an inverter cascade using CRISPRi by building a plasmid containing a single guide RNA (sgRNA) landing pad (pSLiP); this inhibited host cell growth by repressing an essential cellular gene. Anti-sgRNAs on separate plasmids restored cell growth by blocking the expression of growth-inhibitory sgRNAs in pSLiP. We maintained three plasmids in Escherichia coli with a single antibiotic selective marker. To completely avoid antibiotic use and maintain the CRISPRi-based logic inverter cascade, we created a novel d-glutamate auxotrophic E. coli. This enabled the stable maintenance of the plasmid without antibiotics, enhanced the production of the terpenoid, (-)-α-bisabolol, and generation of an antibiotic-resistance gene-free plasmid. CRISPRi is therefore widely applicable in genetic circuits and may allow for antibiotic-free biomanufacturing.
Collapse
Affiliation(s)
| | | | - Seung Gyun Woo
- Synthetic Biology Research Center, Korea Research Institute of Bioscience and Biotechnology (KRIBB), Daejeon 34141, Republic of Korea,Department of Biosystems and Bioengineering, KRIBB School of Biotechnology, University of Science and Technology, Daejeon 34143, Republic of Korea
| | - Tae Hyun Kim
- Synthetic Biology Research Center, Korea Research Institute of Bioscience and Biotechnology (KRIBB), Daejeon 34141, Republic of Korea,Department of Biosystems and Bioengineering, KRIBB School of Biotechnology, University of Science and Technology, Daejeon 34143, Republic of Korea
| | - Eugene Rha
- Synthetic Biology Research Center, Korea Research Institute of Bioscience and Biotechnology (KRIBB), Daejeon 34141, Republic of Korea
| | - Kil Koang Kwon
- Synthetic Biology Research Center, Korea Research Institute of Bioscience and Biotechnology (KRIBB), Daejeon 34141, Republic of Korea
| | - Hyewon Lee
- Synthetic Biology Research Center, Korea Research Institute of Bioscience and Biotechnology (KRIBB), Daejeon 34141, Republic of Korea
| | - Seung-Goo Lee
- To whom correspondence should be addressed. Tel: +82 42 860 4373; Fax: +82 42 860 4489;
| | - Dae-Hee Lee
- Correspondence may also be addressed to Dae-Hee Lee. Tel: +82 42 879 8225; Fax: +82 42 860 4489;
| |
Collapse
|
2
|
Schulz-Mirbach H, Müller A, Wu T, Pfister P, Aslan S, Schada von Borzyskowski L, Erb TJ, Bar-Even A, Lindner SN. On the flexibility of the cellular amination network in E coli. eLife 2022; 11:e77492. [PMID: 35876664 PMCID: PMC9436414 DOI: 10.7554/elife.77492] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2022] [Accepted: 07/22/2022] [Indexed: 12/03/2022] Open
Abstract
Ammonium (NH4+) is essential to generate the nitrogenous building blocks of life. It gets assimilated via the canonical biosynthetic routes to glutamate and is further distributed throughout metabolism via a network of transaminases. To study the flexibility of this network, we constructed an Escherichia coli glutamate auxotrophic strain. This strain allowed us to systematically study which amino acids serve as amine sources. We found that several amino acids complemented the auxotrophy either by producing glutamate via transamination reactions or by their conversion to glutamate. In this network, we identified aspartate transaminase AspC as a major connector between many amino acids and glutamate. Additionally, we extended the transaminase network by the amino acids β-alanine, alanine, glycine, and serine as new amine sources and identified d-amino acid dehydrogenase (DadA) as an intracellular amino acid sink removing substrates from transaminase reactions. Finally, ammonium assimilation routes producing aspartate or leucine were introduced. Our study reveals the high flexibility of the cellular amination network, both in terms of transaminase promiscuity and adaptability to new connections and ammonium entry points.
Collapse
Affiliation(s)
| | - Alexandra Müller
- Max Planck Institute of Molecular Plant PhysiologyPotsdamGermany
| | - Tong Wu
- Max Planck Institute of Molecular Plant PhysiologyPotsdamGermany
| | - Pascal Pfister
- Max Planck Institute for Terrestrial MicrobiologyMarburgGermany
| | - Selçuk Aslan
- Max Planck Institute of Molecular Plant PhysiologyPotsdamGermany
| | - Lennart Schada von Borzyskowski
- Max Planck Institute for Terrestrial MicrobiologyMarburgGermany
- Institute of Biology Leiden, Leiden UniversityLeidenNetherlands
| | - Tobias J Erb
- Max Planck Institute for Terrestrial MicrobiologyMarburgGermany
- Center for Synthetic Microbiology (SYNMIKRO)MarburgGermany
| | - Arren Bar-Even
- Max Planck Institute of Molecular Plant PhysiologyPotsdamGermany
| | - Steffen N Lindner
- Max Planck Institute of Molecular Plant PhysiologyPotsdamGermany
- Department of Biochemistry, Charité – Universitätsmedizin BerlinBerlinGermany
| |
Collapse
|
3
|
Ogasawara Y, Dairi T. Discovery of an alternative pathway of peptidoglycan biosynthesis: A new target for pathway specific inhibitors. J Ind Microbiol Biotechnol 2021; 48:6296644. [PMID: 34114638 PMCID: PMC8788868 DOI: 10.1093/jimb/kuab038] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2021] [Accepted: 06/07/2021] [Indexed: 11/13/2022]
Abstract
Peptidoglycan in bacterial cell walls is a biopolymer consisting of sugars and amino acids and plays important role in maintaining cell integrity from the environment. Its biosynthesis is a major target for antibiotics and the genes and enzymes involved in the biosynthetic pathway have been well studied. However, we recently identified an alternative pathway in the early stage of peptidoglycan biosynthesis in Xanthomonas oryzae, a plant pathogen causing bacterial blight disease of rice. The distribution of the alternative pathway is limited to relatively few bacterial genera that contain many pathogenic species, including Xylella and Stenotrophomonas, besides Xanthomonas. Thus, the alternative pathway is an attractive target for the development of narrow spectrum antibiotics specific to pathogens. In this minireview, we summarize the discovery of the alternative pathway and identification of its specific inhibitors.
Collapse
Affiliation(s)
- Yasushi Ogasawara
- Graduate School of Engineering, Hokkaido University, N13 & W8, Kita-ku, Sapporo, Hokkaido 060-8628, Japan
| | - Tohru Dairi
- Graduate School of Engineering, Hokkaido University, N13 & W8, Kita-ku, Sapporo, Hokkaido 060-8628, Japan
| |
Collapse
|
4
|
Muhammad M, Bai J, Alhassan AJ, Sule H, Ju J, Zhao B, Liu D. Significance of Glutamate Racemase for the Viability and Cell Wall Integrity of Streptococcus iniae. BIOCHEMISTRY (MOSCOW) 2020; 85:248-256. [PMID: 32093601 DOI: 10.1134/s0006297920020121] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Streptococcus iniae is a pathogenic and zoonotic bacterium responsible for human diseases and mortality of many fish species. Recently, this bacterium has demonstrated an increasing trend for antibiotics resistance, which has warranted a search for new approaches to tackle its infection. Glutamate racemase (MurI) is a ubiquitous enzyme of the peptidoglycan synthesis pathway that plays an important role in the cell wall integrity maintenance; however, the significance of this enzyme differs in different species. In this study, we knocked out the MurI gene in S. iniae in order to elucidate the role of glutamate racemase in maintaining cell wall integrity in this bacterial species. We also cloned, expressed, and purified MurI and determined its biochemical characteristics. Biochemical analysis revealed that the MurI gene in S. iniae encodes a functional enzyme with a molecular weight of 30 kDa, temperature optimum at 35°C, and pH optimum at 8.5. Metal ions, such as Cu2+, Mn2+, Co2+ and Zn2+, inhibited the enzyme activity. MurI was found to be essential for the viability and cell wall integrity of S. iniae. The optimal growth of the MurI-deficient S. iniae mutant can be achieved only by adding a high concentration of D-glutamate to the medium. Membrane permeability assay of the mutant showed an increasing extent of the cell wall damage with time upon D-glutamate starvation. Moreover, the mutant lost its virulence when incubated in fish blood. Our results demonstrated that the MurI knockout leads to the generation of S. iniae auxotroph with damaged cell walls.
Collapse
Affiliation(s)
- M Muhammad
- College of Life Science, Hebei Normal University, Shijiazhuang, 050024, China.,Kano University of Science and Technology, Department of Biochemistry, Wudil, Nigeria
| | - J Bai
- College of Life Science, Hebei Normal University, Shijiazhuang, 050024, China
| | - A J Alhassan
- Bayero University Kano, Department of Biochemistry, Kano, Nigeria
| | - H Sule
- Bayero University Kano, Department of Medical Laboratory Science, Kano, Nigeria
| | - J Ju
- College of Life Science, Hebei Normal University, Shijiazhuang, 050024, China
| | - B Zhao
- College of Life Science, Hebei Normal University, Shijiazhuang, 050024, China.
| | - D Liu
- College of Life Science, Hebei Normal University, Shijiazhuang, 050024, China.
| |
Collapse
|
5
|
Vornhagen J, Sun Y, Breen P, Forsyth V, Zhao L, Mobley HLT, Bachman MA. The Klebsiella pneumoniae citrate synthase gene, gltA, influences site specific fitness during infection. PLoS Pathog 2019; 15:e1008010. [PMID: 31449551 PMCID: PMC6730947 DOI: 10.1371/journal.ppat.1008010] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2019] [Revised: 09/06/2019] [Accepted: 07/29/2019] [Indexed: 01/09/2023] Open
Abstract
Klebsiella pneumoniae (Kp), one of the most common causes of healthcare-associated infections, increases patient morbidity, mortality, and hospitalization costs. Kp must acquire nutrients from the host for successful infection; however, the host is able to prevent bacterial nutrient acquisition through multiple systems. This includes the innate immune protein lipocalin 2 (Lcn2), which prevents Kp iron acquisition. To identify novel Lcn2-dependent Kp factors that mediate evasion of nutritional immunity during lung infection, we undertook an InSeq study using a pool of >20,000 transposon mutants administered to Lcn2+/+ and Lcn2-/- mice. Comparing transposon mutant frequencies between mouse genotypes, we identified the Kp citrate synthase, GltA, as potentially interacting with Lcn2, and this novel finding was independently validated. Interestingly, in vitro studies suggest that this interaction is not direct. Given that GltA is involved in oxidative metabolism, we screened the ability of this mutant to use a variety of carbon and nitrogen sources. The results indicated that the gltA mutant has a distinct amino acid auxotrophy rendering it reliant upon glutamate family amino acids for growth. Deletion of Lcn2 from the host leads to increased amino acid levels in bronchioloalveolar lavage fluid, corresponding to increased fitness of the gltA mutant in vivo and ex vivo. Accordingly, addition of glutamate family amino acids to Lcn2+/+ bronchioloalveolar lavage fluid rescued growth of the gltA mutant. Using a variety of mouse models of infection, we show that GltA is an organ-specific fitness factor required for complete fitness in the spleen, liver, and gut, but dispensable in the bloodstream. Similar to bronchioloalveolar lavage fluid, addition of glutamate family amino acids to Lcn2+/+ organ lysates was sufficient to rescue the loss of gltA. Together, this study describes a critical role for GltA in Kp infection and provides unique insight into how metabolic flexibility impacts bacterial fitness during infection. The bacteria Klebsiella pneumoniae (Kp) is an important cause of infection in healthcare settings. These infections can be difficult to treat, as they frequently occur in chronically ill patients and the bacteria have the ability to acquire multiple antibiotic resistance markers. Kp is a common colonizer of the intestinal tract in hospitalized patients, and can progress to infections of the bloodstream, respiratory, and urinary tract. However, the bacterial factors that allow Kp to replicate in these different body sites are unclear. In this study, we found that the Kp citrate synthase, GltA, enables bacterial replication in the lung and intestine by enhancing the ability of Kp to use diverse nutrients in a mechanism known as metabolic flexibility. Kp lacking GltA require specific amino acids that are abundant in blood, but not other body sites. The work in this study provides novel insight into why Kp is a successful hospital pathogen that can colonize and infect multiple body sites.
Collapse
Affiliation(s)
- Jay Vornhagen
- Department of Pathology, University of Michigan, Ann Arbor, United States of America
| | - Yuang Sun
- Department of Pathology, University of Michigan, Ann Arbor, United States of America
| | - Paul Breen
- Department of Pathology, University of Michigan, Ann Arbor, United States of America
| | - Valerie Forsyth
- Department of Microbiology & Immunology, University of Michigan, Ann Arbor, United States of America
| | - Lili Zhao
- Department of Biostatistics, School of Public Health, University of Michigan, Ann Arbor, United States of America
| | - Harry L T Mobley
- Department of Microbiology & Immunology, University of Michigan, Ann Arbor, United States of America
| | - Michael A Bachman
- Department of Pathology, University of Michigan, Ann Arbor, United States of America
| |
Collapse
|
6
|
Ogasawara Y, Shigematsu M, Sato S, Kato H, Dairi T. Involvement of Peptide Epimerization in Poly-γ-glutamic Acid Biosynthesis. Org Lett 2019; 21:3972-3975. [PMID: 31090431 DOI: 10.1021/acs.orglett.9b01121] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Poly-γ-glutamic acid (PGA) is a promising polymer that comprises d- and l-glutamic acid (Glu) connected via an amide bond. PGA is biosynthesized by a transmembrane enzyme complex composed of PgsB, PgsC, and PgsA. However, the detailed reaction, especially the mechanism for introducing d-Glu residues into PGA, remains elusive. We herein report isotope tracer experiments with deuterated l- and d-Glu and demonstrate that epimerization of a growing peptide is involved in PGA biosynthesis.
Collapse
Affiliation(s)
- Yasushi Ogasawara
- Graduate School of Engineering , Hokkaido University , Sapporo , Hokkaido 060-8628 , Japan
| | - Mayuko Shigematsu
- Graduate School of Engineering , Hokkaido University , Sapporo , Hokkaido 060-8628 , Japan
| | - Shota Sato
- Graduate School of Engineering , Hokkaido University , Sapporo , Hokkaido 060-8628 , Japan
| | - Hinata Kato
- Graduate School of Engineering , Hokkaido University , Sapporo , Hokkaido 060-8628 , Japan
| | - Tohru Dairi
- Graduate School of Engineering , Hokkaido University , Sapporo , Hokkaido 060-8628 , Japan
| |
Collapse
|
7
|
Abstract
ABSTRACT
Peptides, biologically occurring oligomers of amino acids linked by amide bonds, are essential for living organisms. Many peptides isolated as natural products have biological functions such as antimicrobial, antivirus and insecticidal activities. Peptides often possess structural features or modifications not found in proteins, including the presence of nonproteinogenic amino acids, macrocyclic ring formation, heterocyclization, N-methylation and decoration by sugars or acyl groups. Nature employs various strategies to increase the structural diversity of peptides. Enzymes that modify peptides to yield mature natural products are of great interest for discovering new enzyme chemistry and are important for medicinal chemistry applications. We have discovered novel peptide modifying enzymes and have identified: (i) a new class of amide bond forming-enzymes; (ii) a pathway to biosynthesize a carbonylmethylene-containing pseudodipeptide structure; and (iii) two distinct peptide epimerases. In this review, an overview of our findings on peptide modifying enzymes is presented.
Collapse
|
8
|
Liechti G, Singh R, Rossi PL, Gray MD, Adams NE, Maurelli AT. Chlamydia trachomatis dapF Encodes a Bifunctional Enzyme Capable of Both d-Glutamate Racemase and Diaminopimelate Epimerase Activities. mBio 2018; 9:e00204-18. [PMID: 29615498 PMCID: PMC5885031 DOI: 10.1128/mbio.00204-18] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2018] [Accepted: 02/16/2018] [Indexed: 02/03/2023] Open
Abstract
Peptidoglycan is a sugar/amino acid polymer unique to bacteria and essential for division and cell shape maintenance. The d-amino acids that make up its cross-linked stem peptides are not abundant in nature and must be synthesized by bacteria de novo d-Glutamate is present at the second position of the pentapeptide stem and is strictly conserved in all bacterial species. In Gram-negative bacteria, d-glutamate is generated via the racemization of l-glutamate by glutamate racemase (MurI). Chlamydia trachomatis is the leading cause of infectious blindness and sexually transmitted bacterial infections worldwide. While its genome encodes a majority of the enzymes involved in peptidoglycan synthesis, no murI homologue has ever been annotated. Recent studies have revealed the presence of peptidoglycan in C. trachomatis and confirmed that its pentapeptide includes d-glutamate. In this study, we show that C. trachomatis synthesizes d-glutamate by utilizing a novel, bifunctional homologue of diaminopimelate epimerase (DapF). DapF catalyzes the final step in the synthesis of meso-diaminopimelate, another amino acid unique to peptidoglycan. Genetic complementation of an Escherichia coli murI mutant demonstrated that Chlamydia DapF can generate d-glutamate. Biochemical analysis showed robust activity, but unlike canonical glutamate racemases, activity was dependent on the cofactor pyridoxal phosphate. Genetic complementation, enzymatic characterization, and bioinformatic analyses indicate that chlamydial DapF shares characteristics with other promiscuous/primordial enzymes, presenting a potential mechanism for d-glutamate synthesis not only in Chlamydia but also numerous other genera within the Planctomycetes-Verrucomicrobiae-Chlamydiae superphylum that lack recognized glutamate racemases.IMPORTANCE Here we describe one of the last remaining "missing" steps in peptidoglycan synthesis in pathogenic Chlamydia species, the synthesis of d-glutamate. We have determined that the diaminopimelate epimerase (DapF) encoded by Chlamydia trachomatis is capable of carrying out both the epimerization of DAP and the pyridoxal phosphate-dependent racemization of glutamate. Enzyme promiscuity is thought to be the hallmark of early microbial life on this planet, and there is currently an active debate as to whether "moonlighting enzymes" represent primordial evolutionary relics or are a product of more recent reductionist evolutionary pressures. Given the large number of Chlamydia species (as well as members of the Planctomycetes-Verrucomicrobiae-Chlamydiae superphylum) that possess DapF but lack homologues of MurI, it is likely that DapF is a primordial isomerase that functions as both racemase and epimerase in these organisms, suggesting that specialized d-glutamate racemase enzymes never evolved in these microbes.
Collapse
Affiliation(s)
- George Liechti
- Department of Microbiology and Immunology, F. Edward Hébert School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, Maryland, USA
| | - Raghuveer Singh
- Emerging Pathogens Institute and Department of Environmental and Global Health, College of Public Health and Health Professions, University of Florida, Gainesville, Florida, USA
| | - Patricia L Rossi
- Department of Microbiology and Immunology, F. Edward Hébert School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, Maryland, USA
| | - Miranda D Gray
- Department of Microbiology and Immunology, F. Edward Hébert School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, Maryland, USA
| | - Nancy E Adams
- Department of Microbiology and Immunology, F. Edward Hébert School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, Maryland, USA
| | - Anthony T Maurelli
- Department of Microbiology and Immunology, F. Edward Hébert School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, Maryland, USA
- Emerging Pathogens Institute and Department of Environmental and Global Health, College of Public Health and Health Professions, University of Florida, Gainesville, Florida, USA
| |
Collapse
|
9
|
Ogasawara Y, Dairi T. Peptide Epimerization Machineries Found in Microorganisms. Front Microbiol 2018; 9:156. [PMID: 29467749 PMCID: PMC5808125 DOI: 10.3389/fmicb.2018.00156] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2017] [Accepted: 01/23/2018] [Indexed: 11/13/2022] Open
Abstract
D-Amino acid residues have been identified in peptides from a variety of eukaryotes and prokaryotes. In microorganisms, UDP-N-acetylmuramic acid pentapeptide (UDP-MurNAc-L-Ala-D-Glu-meso-diaminopimelate-D-Ala-D-Ala), a unit of peptidoglycan, is a representative. During its biosynthesis, D-Ala and D-Glu are generally supplied by racemases from the corresponding isomers. However, we recently identified a unique unidirectional L-Glu epimerase catalyzing the epimerization of the terminal L-Glu of UDP-MurNAc-L-Ala-L-Glu. Several such enzymes, introducing D-amino acid resides into peptides via epimerization, have been reported to date. This includes a L-Ala-D/L-Glu epimerase, which is possibly used during peptidoglycan degradation. In bacterial primary metabolisms, to the best of our knowledge, these two machineries are the only examples of peptide epimerization. However, a variety of peptides containing D-amino acid residues have been isolated from microorganisms as secondary metabolites. Their biosynthetic mechanisms have been studied and three different peptide epimerization machineries have been reported. The first is non-ribosomal peptide synthetase (NRPS). Excellent studies with dissected modules of gramicidin synthetase and tyrocidine synthetase revealed the reactions of the epimerization domains embedded in the enzymes. The obtained information is still utilized to predict epimerization domains in uncharacterized NRPSs. The second includes the biosynthetic enzymes of lantibiotics, which are ribosome-dependently supplied peptide antibiotics containing polycyclic thioether amino acids (lanthionines). A mechanism for the formation of the D-Ala moiety in lanthionine by two enzymes, dehydratases catalyzing the conversion of L-Ser into dehydroalanine and enzymes catalyzing nucleophilic attack of the thiol of cysteine into dehydroalanine, was clarified. Similarly, the formation of a D-Ala residue by reduction of the dehydroalanine residue was also reported. The last type of machinery includes radical-S-adenosylmethionine (rSAM)-dependent enzymes, which catalyze a variety of radical-mediated chemical transformations. In the biosynthesis of polytheonamide, a marine sponge-derived and ribosome-dependently supplied peptide composed of 48 amino acids, a rSAM enzyme (PoyD) is responsible for unidirectional epimerizations of multiple different amino acids in the precursor peptide. In this review, we briefly summarize the discovery and current mechanistic understanding of these peptide epimerization enzymes.
Collapse
Affiliation(s)
| | - Tohru Dairi
- Graduate School of Engineering, Hokkaido University, Sapporo, Japan
| |
Collapse
|
10
|
Investigation of the essentiality of glutamate racemase in Mycobacterium smegmatis. J Bacteriol 2014; 196:4239-44. [PMID: 25246478 DOI: 10.1128/jb.02090-14] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The mycobacterial cell wall frequently has been used as a target for drug development, and d-glutamate, synthesized by glutamate racemase (MurI), is an important component of peptidoglycan. While the essentiality of the murI gene has been shown in several bacterial species, including Escherichia coli, Bacillus anthracis, and Streptococcus pneumoniae, studies in mycobacteria have not yet provided definitive results. This study aimed to determine whether murI is indeed essential and can serve as a possible target for structure-aided drug design. We have achieved this goal by creating a ΔmurI strain of Mycobacterium smegmatis, a close relative of Mycobacterium tuberculosis. The deletion of the murI gene in M. smegmatis could be achieved only in minimal medium supplemented with D-glutamate, demonstrating that MurI is essential for growth and that glutamate racemase is the only source of D-glutamate for peptidoglycan synthesis in M. smegmatis.
Collapse
|
11
|
Kudan S, Kuttiyawong K, Pichyangkura R. Carboxy-terminus truncations of Bacillus licheniformis SK-1 CHI72 with distinct substrate specificity. BMB Rep 2011; 44:375-80. [PMID: 21699749 DOI: 10.5483/bmbrep.2011.44.6.375] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Bacillus licheniformis SK-1 naturally produces chitinase 72 (CHI72) with two truncation derivatives at the C-terminus, one with deletion of the chitin binding domain (ChBD), and the other with deletions of both fibronectin type III domain (FnIIID) and ChBD. We constructed deletions mutants of CHI72 with deletion of ChBD (CHI72ΔChBD) and deletions of both FnIIID and ChBD (CHI72ΔFnIIIDΔChBD), and studied their activity on soluble, amorphous and crystalline substrates. Interestingly, when equivalent amount of specific activity of each enzyme on soluble substrate was used, the product yield from CHI72- ΔChBD and CHI72ΔFnIIIDΔChBD on colloidal chitin was 2.5 and 1.6 fold higher than CHI72, respectively. In contrast, the product yield from CHI72ΔChBD and CHI72ΔFnIIID- ΔChBD on Β-chitin reduced to 0.7 and 0.5 fold of CHI72, respectively. These results suggest that CHI72 can modulate its substrate specificities through truncations of the functional domains at the C-terminus, producing a mixture of enzymes with elevated efficiency of hydrolysis.
Collapse
Affiliation(s)
- Sanya Kudan
- Biotechnology Program, Biochemistry Department, Faculty of Science, Chulalongkorn University, Bangkok, Thailand.
| | | | | |
Collapse
|
12
|
Abstract
We have generated extreme ionizing radiation resistance in a relatively sensitive bacterial species, Escherichia coli, by directed evolution. Four populations of Escherichia coli K-12 were derived independently from strain MG1655, with each specifically adapted to survive exposure to high doses of ionizing radiation. D(37) values for strains isolated from two of the populations approached that exhibited by Deinococcus radiodurans. Complete genomic sequencing was carried out on nine purified strains derived from these populations. Clear mutational patterns were observed that both pointed to key underlying mechanisms and guided further characterization of the strains. In these evolved populations, passive genomic protection is not in evidence. Instead, enhanced recombinational DNA repair makes a prominent but probably not exclusive contribution to genome reconstitution. Multiple genes, multiple alleles of some genes, multiple mechanisms, and multiple evolutionary pathways all play a role in the evolutionary acquisition of extreme radiation resistance. Several mutations in the recA gene and a deletion of the e14 prophage both demonstrably contribute to and partially explain the new phenotype. Mutations in additional components of the bacterial recombinational repair system and the replication restart primosome are also prominent, as are mutations in genes involved in cell division, protein turnover, and glutamate transport. At least some evolutionary pathways to extreme radiation resistance are constrained by the temporally ordered appearance of specific alleles.
Collapse
|
13
|
Fisher SL. Glutamate racemase as a target for drug discovery. Microb Biotechnol 2008; 1:345-60. [PMID: 21261855 PMCID: PMC3815242 DOI: 10.1111/j.1751-7915.2008.00031.x] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2007] [Revised: 01/11/2008] [Accepted: 02/15/2008] [Indexed: 11/28/2022] Open
Abstract
The bacterial cell wall is a highly cross-linked polymeric structure consisting of repeating peptidoglycan units, each of which contains a novel pentapeptide substitution which is cross-linked through transpeptidation. The incorporation of D-glutamate as the second residue is strictly conserved across the bacterial kingdom. Glutamate racemase, a member of the cofactor-independent, two-thiol-based family of amino acid racemases, has been implicated in the production and maintenance of sufficient d-glutamate pool levels required for growth. The subject of over four decades of research, it is now evident that the enzyme is conserved and essential for growth across the bacterial kingdom and has a conserved overall topology and active site architecture; however, several different mechanisms of regulation have been observed. These traits have recently been targeted in the discovery of both narrow and broad spectrum inhibitors. This review outlines the biological history of this enzyme, the recent biochemical and structural characterization of isozymes from a wide range of species and developments in the identification of inhibitors that target the enzyme as possible therapeutic agents.
Collapse
Affiliation(s)
- Stewart L Fisher
- Infection Discovery, AstraZeneca R&D Boston, 35 Gatehouse Drive, Waltham, MA 02451, USA.
| |
Collapse
|
14
|
Ashiuchi M, Nishikawa Y, Matsunaga K, Yamamoto M, Shimanouchi K, Misono H. Genetic design of conditional d-glutamate auxotrophy for Bacillus subtilis: Use of a vector-borne poly-γ-glutamate synthetic system. Biochem Biophys Res Commun 2007; 362:646-50. [PMID: 17720142 DOI: 10.1016/j.bbrc.2007.08.019] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2007] [Accepted: 08/03/2007] [Indexed: 11/26/2022]
Abstract
Bacillus subtilis possesses two glutamate racemase isozymes, RacE and YrpC. For the first time, we succeeded in constructing glutamate racemase-gene disruptants of B. subtilis. Phenotypic analysis of their D-glutamate auxotrophy indicated that the RacE-type glutamate racemase is important for ensuring maximum growth rate but dispensable. The YrpC-type glutamate racemase probably operates as an anaplerotic enzyme for RacE, especially under liquid culture conditions. We found novel applicability of RacE-less mutants inheriting only a marginal activity for endogenous D-glutamate supply, viz. the employment for the in vivo identification of D-glutamate-consuming systems. In fact, the genetic induction of a poly-gamma-glutamate synthetic system led a RacE-less mutant to severe growth suppression, which was overcome in the presence of a high concentration of exogenous D-glutamate. The results indicate that a significant amount of D-glutamate is consumed during poly-glutamate biosynthesis. To our knowledge, this is the first report of conditional D-glutamate auxotrophy for B. subtilis.
Collapse
Affiliation(s)
- Makoto Ashiuchi
- Department of Bioresources Science, Kochi University, Nankoku, Kochi 783-8502, Japan.
| | | | | | | | | | | |
Collapse
|
15
|
Baek DH, Song JJ, Kwon SJ, Park C, Jung CM, Sung MH. Characteristics of a new enantioselective thermostable dipeptidase from Brevibacillus borstelensis BCS-1 and its application to synthesis of a D-amino-acid-containing dipeptide. Appl Environ Microbiol 2004; 70:1570-5. [PMID: 15006780 PMCID: PMC368365 DOI: 10.1128/aem.70.3.1570-1575.2004] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A new thermostable dipeptidase gene was cloned from the thermophile Brevibacillus borstelensis BCS-1 by genetic complementation of the D-Glu auxotroph Escherichia coli WM335 on a plate containing D-Ala-D-Glu. Nucleotide sequence analysis revealed that the gene included an open reading frame coding for a 307-amino-acid sequence with an M(r) of 35,000. The deduced amino acid sequence of the dipeptidase exhibited 52% similarity with the dipeptidase from Listeria monocytogenes. The enzyme was purified to homogeneity from recombinant E. coli WM335 harboring the dipeptidase gene from B. borstelensis BCS-1. Investigation of the enantioselectivity (E) to the P(1) and P(1)' site of Ala-Ala revealed that the ratio of the specificity constant (k(cat)/K(m)) for L-enantioselectivity to the P(1) site of Ala-Ala was 23.4 +/- 2.2 [E = (k(cat)/K(m))(L,D)/(k(cat)/K(m))(D,D)], while the D-enantioselectivity to the P(1)' site of Ala-Ala was 16.4 +/- 0.5 [E = (k(cat)/K(m))(L,D)/(k(cat)/K(m))(L,L)] at 55 degrees C. The enzyme was stable up to 55 degrees C, and the optimal pH and temperature were 8.5 and 65 degrees C, respectively. The enzyme was able to hydrolyze L-Asp-D-Ala, L-Asp-D-AlaOMe, Z-D-Ala-D-AlaOBzl, and Z-L-Asp-D-AlaOBzl, yet it could not hydrolyze D-Ala-L-Asp, D-Ala-L-Ala, D-AlaNH(2), and L-AlaNH(2.) The enzyme also exhibited beta-lactamase activity similar to that of a human renal dipeptidase. The dipeptidase successfully synthesized the precursor of the dipeptide sweetener Z-L-Asp-D-AlaOBzl.
Collapse
Affiliation(s)
- Dae Heoun Baek
- Laboratory of Microbial Function, Korea Research Institute of Bioscience and Biotechnology, Yusong-Gu. BioLeaders Corporation, Joong-Gu, Daejeon, South Korea
| | | | | | | | | | | |
Collapse
|
16
|
Benson TE, Prince DB, Mutchler VT, Curry KA, Ho AM, Sarver RW, Hagadorn JC, Choi GH, Garlick RL. X-ray crystal structure of Staphylococcus aureus FemA. Structure 2002; 10:1107-15. [PMID: 12176388 DOI: 10.1016/s0969-2126(02)00807-9] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The latter stages of peptidoglycan biosynthesis in Staphylococci involve the synthesis of a pentaglycine bridge on the epsilon amino group of the pentapeptide lysine side chain. Genetic and biochemical evidence suggest that sequential addition of these glycines is catalyzed by three homologous enzymes, FemX (FmhB), FemA, and FemB. The first protein structure from this family, Staphylococcus aureus FemA, has been solved at 2.1 A resolution by X-ray crystallography. The FemA structure reveals a unique organization of several known protein folds involved in peptide and tRNA binding. The surface of the protein also reveals an L-shaped channel suitable for a peptidoglycan substrate. Analysis of the structural features of this enzyme provides clues to the mechanism of action of S. aureus FemA.
Collapse
Affiliation(s)
- Timothy E Benson
- Structural, Analytical, and Medicinal Chemistry, Pharmacia Corporation, Kalamazoo, MI 49007, USA.
| | | | | | | | | | | | | | | | | |
Collapse
|
17
|
Application of a thermostable glutamate racemase from Bacillus sp. SK-1 for the production of d-phenylalanine in a multi-enzyme system. ACTA ACUST UNITED AC 2002. [DOI: 10.1016/s1381-1177(02)00011-5] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
|
18
|
Benson TE, Harris MS, Choi GH, Cialdella JI, Herberg JT, Martin JP, Baldwin ET. A structural variation for MurB: X-ray crystal structure of Staphylococcus aureus UDP-N-acetylenolpyruvylglucosamine reductase (MurB). Biochemistry 2001; 40:2340-50. [PMID: 11327854 DOI: 10.1021/bi002162d] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The X-ray crystal structure of the substrate free form of Staphylococcus aureus UDP-N-acetylenolpyruvylglucosamine reductase (MurB) has been solved to 2.3 A resolution with an R-factor of 20.3% and a free R-factor of 22.3%. While the overall fold of the S. aureus enzyme is similar to that of the homologous Escherichia coli MurB X-ray crystal structure, notable distinctions between the S. aureus and E. coli MurB protein structures occur in residues involved in substrate binding. Analysis of available MurB sequences from other bacteria suggest that the S. aureus MurB structure is representative of a distinct structural class of UDP-N-acetylenolpyruvylglucosamine reductases including Bacillus subtilis and Helicobacter pylori that are characterized by a modified mechanism for substrate binding.
Collapse
Affiliation(s)
- T E Benson
- Structural, Analytical, and Medicinal Chemistry, Biology, and Protein Science, Pharmacia Corporation, 301 Henrietta Street, Kalamazoo, Michigan 49007, USA.
| | | | | | | | | | | | | |
Collapse
|
19
|
Abstract
This map is an update of the edition 9 map by Berlyn et al. (M. K. B. Berlyn, K. B. Low, and K. E. Rudd, p. 1715-1902, in F. C. Neidhardt et al., ed., Escherichia coli and Salmonella: cellular and molecular biology, 2nd ed., vol. 2, 1996). It uses coordinates established by the completed sequence, expressed as 100 minutes for the entire circular map, and adds new genes discovered and established since 1996 and eliminates those shown to correspond to other known genes. The latter are included as synonyms. An alphabetical list of genes showing map location, synonyms, the protein or RNA product of the gene, phenotypes of mutants, and reference citations is provided. In addition to genes known to correspond to gene sequences, other genes, often older, that are described by phenotype and older mapping techniques and that have not been correlated with sequences are included.
Collapse
Affiliation(s)
- M K Berlyn
- Department of Biology and School of Forestry and Environmental Studies, Yale University, New Haven, Connecticut 06520-8104, USA.
| |
Collapse
|
20
|
Pucci MJ, Thanassi JA, Discotto LF, Kessler RE, Dougherty TJ. Identification and characterization of cell wall-cell division gene clusters in pathogenic gram-positive cocci. J Bacteriol 1997; 179:5632-5. [PMID: 9287029 PMCID: PMC179445 DOI: 10.1128/jb.179.17.5632-5635.1997] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Clusters of peptidoglycan biosynthesis and cell division genes (DCW genes) were identified and sequenced in two gram-positive cocci, Staphylococcus aureus and Enterococcus faecalis. The results indicated some similarities in organization compared with previously reported bacterial DCW gene clusters, including the presence of penicillin-binding proteins at the left ends and ftsA and ftsZ cell division genes at the right ends of the clusters. However, there were also some important differences, including the absence of several genes, the comparative sizes of the div1B and ftsQ genes, and a wide range of amino acid sequence similarities when the genes of the gram-positive cocci were translated and compared to bacterial homologs.
Collapse
Affiliation(s)
- M J Pucci
- Department of Microbiology, Bristol-Myers Squibb Pharmaceutical Research Institute, Wallingford, Connecticut 06492, USA.
| | | | | | | | | |
Collapse
|
21
|
Pucci MJ, Thanassi JA, Ho HT, Falk PJ, Dougherty TJ. Staphylococcus haemolyticus contains two D-glutamic acid biosynthetic activities, a glutamate racemase and a D-amino acid transaminase. J Bacteriol 1995; 177:336-42. [PMID: 7814322 PMCID: PMC176596 DOI: 10.1128/jb.177.2.336-342.1995] [Citation(s) in RCA: 50] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Two D-glutamic acid biosynthetic activities, glutamate racemase and D-amino acid transaminase, have been described previously for bacteria. To date, no bacterial species has been reported to possess both activities. Genetic complementation studies using Escherichia coli WM335, a D-glutamic acid auxotroph, and cloned chromosomal DNA fragments from Staphylococcus haemolyticus revealed two distinct DNA fragments containing open reading frames which, when present, allowed growth on medium without exogenous D-glutamic acid. Amino acid sequences of the two open reading frames derived from the DNA nucleotide sequences indicated extensive identity with the amino acid sequence of Pediococcus pentosaceous glutamate racemase in one case and with that of the D-amino acid transaminase of Bacillus spp. in the second case. Enzymatic assays of lysates of E. coli WM335 strains containing either the cloned staphylococcal racemase or transminase verified the identities of these activities. Subsequent DNA hybridization experiments indicated that Staphylococcus aureus, in addition to S. haemolyticus, contained homologous chromosomal DNA for each of these genes. These data suggest that S. haemolyticus, and probably S. aureus, contains genes for two D-glutamic acid biosynthetic activities, a glutamate racemase (dga gene) and a D-amino acid transaminase (dat gene).
Collapse
Affiliation(s)
- M J Pucci
- Department of Microbiology, Bristol-Myers Squibb Pharmaceutical Research Institute, Wallingford, Connecticut 06492-7660
| | | | | | | | | |
Collapse
|
22
|
Hufton SE, Ward RJ, Bunce NA, Armstrong JT, Fletcher AJ, Glass RE. Structure-function analysis of the vitamin B12 receptor of Escherichia coli by means of informational suppression. Mol Microbiol 1995; 15:381-93. [PMID: 7746157 DOI: 10.1111/j.1365-2958.1995.tb02251.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
We describe a genetic analysis of the vitamin B12 receptor of Escherichia coli. Through the use of informational suppression, we have been able to generate a family of receptor variants, each identical save for a single, known substitution (Ser, Gln, Lys, Tyr, Leu, Cys, Phe) at a known site. We have studied 22 different mutants, 14 in detail, distributed throughout the length of the btuB gene. Most amino acid substitutions have a pleiotropic effect with respect to all ligands tested, the two colicins E1 and E3, the T5-like bacteriophage BF23, and vitamin B12. (The dramatic effect of a single amino acid substitution is also well exemplified by the G142A missense change which renders the receptor completely non-functional.) In some instances, however, we have been able to modify a subset of receptor functions (viz. Q62, Q150 and Q299 and the response to phage BF23). These data are summarized on a two-dimensional folding model for the BtuB protein in the outer membrane (devised using both amphipathic beta-strand analysis and sequence conservation amongst the TonB-dependent receptors). In addition, we report that the extreme C-terminus of BtuB is vital for receptor localization and provide evidence for it being a membrane-spanning beta-sheet with residue L588 situated on its hydrophobic surface. Two of the C-terminal btuB mutations are located within the region of overlap with the recently identified dga (murl) gene.
Collapse
Affiliation(s)
- S E Hufton
- Department of Biochemistry, University of Nottingham Medical School, Queen's Medical Centre, UK
| | | | | | | | | | | |
Collapse
|
23
|
Choi SY, Esaki N, Ashiuchi M, Yoshimura T, Soda K. Bacterial glutamate racemase has high sequence similarity with myoglobins and forms an equimolar inactive complex with hemin. Proc Natl Acad Sci U S A 1994; 91:10144-7. [PMID: 7937852 PMCID: PMC44974 DOI: 10.1073/pnas.91.21.10144] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Glutamate racemase (EC 5.1.1.3), an enzyme of microbial origin, shows significant sequence homology with mammalian myoglobins, in particular in the regions corresponding to the E and F helices, which constitute the heme binding pocket of myoglobins. Glutamate racemase binds tightly an equimolar amount of hemin, leading to loss of racemase activity. Although this enzyme shows homology with aspartate racemase, the latter does not bind hemin. The glutamate racemase gene of Pediococcus pentosaceus has a 795-nt open reading frame and encodes 265-amino acid residues, which form a monomeric protein (M(r) 29,000). Neither racemase has cofactors, but they contain essential cysteine residues [Yohda, M., Okada, H. & Kumagai, H. (1991) Biochim. Biophys. Acta 1089, 234-240].
Collapse
Affiliation(s)
- S Y Choi
- Institute for Chemical Research, Kyoto University, Japan
| | | | | | | | | |
Collapse
|
24
|
Chapter 3 Biosynthesis of the bacterial peptidoglycan unit. ACTA ACUST UNITED AC 1994. [DOI: 10.1016/s0167-7306(08)60406-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
|
25
|
Pucci MJ, Novotny J, Discotto LF, Dougherty TJ. The Escherichia coli Dga (MurI) protein shares biological activity and structural domains with the Pediococcus pentosaceus glutamate racemase. J Bacteriol 1994; 176:528-30. [PMID: 7904596 PMCID: PMC205080 DOI: 10.1128/jb.176.2.528-530.1994] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
The Pediococcus pentosaceus glutamate racemase gene product complemented the D-glutamate auxotrophy of Escherichia coli WM335. Amino acid sequence analysis of the two proteins revealed 28% identity, primarily in six clusters scattered throughout the sequence. Further analyses indicated secondary structure similarities between the two proteins. These data support a recent report that the dga (murI) gene product is a glutamate racemase.
Collapse
Affiliation(s)
- M J Pucci
- Department of Microbiology, Bristol-Myers Squibb Research Institute, Wallingford, Connecticut 06492-7660
| | | | | | | |
Collapse
|
26
|
Abstract
A list of currently identified gene products of Escherichia coli is given, together with a bibliography that provides pointers to the literature on each gene product. A scheme to categorize cellular functions is used to classify the gene products of E. coli so far identified. A count shows that the numbers of genes concerned with small-molecule metabolism are on the same order as the numbers concerned with macromolecule biosynthesis and degradation. One large category is the category of tRNAs and their synthetases. Another is the category of transport elements. The categories of cell structure and cellular processes other than metabolism are smaller. Other subjects discussed are the occurrence in the E. coli genome of redundant pairs and groups of genes of identical or closely similar function, as well as variation in the degree of density of genetic information in different parts of the genome.
Collapse
Affiliation(s)
- M Riley
- Marine Biological Laboratory, Woods Hole, Massachusetts 02543
| |
Collapse
|
27
|
|
28
|
Balikó G, Venetianer P. An Escherichia coli gene in search of a function: phenotypic effects of the gene recently identified as murI. J Bacteriol 1993; 175:6571-7. [PMID: 8407834 PMCID: PMC206768 DOI: 10.1128/jb.175.20.6571-6577.1993] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Earlier we reported that an open reading frame located at 89.5 min of the Escherichia coli map (ORFI) codes for a protein of unknown function that could be overexpressed and purified to homogeneity (G. Balikó, A. Raukas, I. Boros, and P. Venetianer, Mol. Gen. Genet. 211:326-331, 1988). In the work described here, we attempted to learn the function of this protein by inactivating the chromosomal gene and providing it or its deletion derivatives on temperature-sensitive plasmids. We found that the presence of the functional ORFI gene is essential; cells are not viable at the nonpermissive temperature or when the region coding for the C-terminal 50 amino acids of the protein is deleted. At intermediate temperatures or when the gene is overexpressed, characteristic changes occur in cell morphology, nucleoid separation during cell division, and supercoiling of plasmids. The possible mechanisms of these effects are discussed in view of the fact that Doublet et al. (P. Doublet, J. van Heijenoort, and D. Mengin-Lecreulx, J. Bacteriol. 174:5772-5779, 1992) recently identified the ORFI gene as murI, involved in D-glutamic acid biosynthesis.
Collapse
Affiliation(s)
- G Balikó
- Institute of Biochemistry, Hungarian Academy of Sciences, Szeged
| | | |
Collapse
|
29
|
Doublet P, van Heijenoort J, Bohin JP, Mengin-Lecreulx D. The murI gene of Escherichia coli is an essential gene that encodes a glutamate racemase activity. J Bacteriol 1993; 175:2970-9. [PMID: 8098327 PMCID: PMC204615 DOI: 10.1128/jb.175.10.2970-2979.1993] [Citation(s) in RCA: 75] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
The murI gene of Escherichia coli was recently identified on the basis of its ability to complement the only mutant requiring D-glutamic acid for growth that had been described to date: strain WM335 of E. coli B/r (P. Doublet, J. van Heijenoort, and D. Mengin-Lecreulx, J. Bacteriol. 174:5772-5779, 1992). We report experiments of insertional mutagenesis of the murI gene which demonstrate that this gene is essential for the biosynthesis of D-glutamic acid, one of the specific components of cell wall peptidoglycan. A special strategy was used for the construction of strains with a disrupted copy of murI, because of a limited capability of E. coli strains grown in rich medium to internalize D-glutamic acid. The murI gene product was overproduced and identified as a glutamate racemase activity. UDP-N-acetylmuramoyl-L-alanine (UDP-MurNAc-L-Ala), which is the nucleotide substrate of the D-glutamic-acid-adding enzyme (the murD gene product) catalyzing the subsequent step in the pathway for peptidoglycan synthesis, appears to be an effector of the racemase activity.
Collapse
Affiliation(s)
- P Doublet
- URA 1131 du Centre National de la Recherche Scientifique (CNRS), Université Paris-Sud, Orsay, France
| | | | | | | |
Collapse
|
30
|
Gallo KA, Knowles JR. Purification, cloning, and cofactor independence of glutamate racemase from Lactobacillus. Biochemistry 1993; 32:3981-90. [PMID: 8385993 DOI: 10.1021/bi00066a019] [Citation(s) in RCA: 77] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Glutamate racemase has been purified more than 12,000-fold from Lactobacillus fermenti. The racemase gene has been cloned using standard hybridization techniques combined with a novel selection for in vivo glutamate racemase activity, and the racemase has been expressed in Escherichia coli as 20-25% of the total soluble cell protein. The cloned gene product is indistinguishable from that purified from Lactobacillus and is a monomer of M(r) 28,300. Both a coupled enzymatic assay and a circular dichroism assay show that the enzyme follows Michaelis-Menten kinetics, with a Km of 0.3 mM and a kcat of 70 s-1 in each reaction direction. Investigations into the cofactor dependence of glutamate racemase indicate that the enzyme employs neither pyridoxal phosphate nor a pyruvoyl group in the labilization of the proton at the stereogenic center of glutamate. Furthermore, the racemase activity is unaffected by the presence of the metal-chelating reagent EDTA. The gene sequence of the racemase is 24% identical to that of aspartate racemase from Streptococcus thermophilus and 30% identical to that of an unidentified open reading frame in the rrnB ribosomal RNA operon of E. coli. Because the two cysteine residues in glutamate racemase and their surrounding regions are well-conserved in both of these sequences, and since glutamate racemase is stabilized by the presence of reduced thiols, these residues are possible candidates for the enzymic bases that deprotonate glutamate at C-2.
Collapse
Affiliation(s)
- K A Gallo
- Department of Chemistry, Harvard University, Cambridge, Massachusetts 02138
| | | |
Collapse
|