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Peñalver M, Paradela A, Palacios-Cuéllar C, Pucciarelli MG, García-Del Portillo F. Experimental evidence of d-glutamate racemase activity in the uncultivated bacterium Candidatus Saccharimonas aalborgensis. Environ Microbiol 2024; 26:e16621. [PMID: 38558504 DOI: 10.1111/1462-2920.16621] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2024] [Accepted: 03/16/2024] [Indexed: 04/04/2024]
Abstract
The Candidate Phyla Radiation (CPR) encompasses widespread uncultivated bacteria with reduced genomes and limited metabolic capacities. Most CPR bacteria lack the minimal set of enzymes required for peptidoglycan (PG) synthesis, leaving it unclear how these bacteria produce this essential envelope component. In this study, we analysed the distribution of d-amino acid racemases that produce the universal PG components d-glutamate (d-Glu) or d-alanine (d-Ala). We also examined moonlighting enzymes that synthesize d-Glu or d-Ala. Unlike other phyla in the domain Bacteria, CPR bacteria do not exhibit these moonlighting activities and have, at most, one gene encoding either a Glu or Ala racemase. One of these 'orphan' racemases is a predicted Glu racemase (MurICPR) from the CPR bacterium Candidatus Saccharimonas aalborgenesis. The expression of MurICPR restores the growth of a Salmonella d-Glu auxotroph lacking its endogenous racemase and results in the substitution of l-Ala by serine as the first residue in a fraction of the PG stem peptides. In vitro, MurICPR exclusively racemizes Glu as a substrate. Therefore, Ca. Saccharimonas aalborgensis may couple Glu racemization to serine and d-Glu incorporation into the stem peptide. Our findings provide the first insights into the synthesis of PG by an uncultivated environmental bacterium and illustrate how to experimentally test enzymatic activities from CPR bacteria related to PG metabolism.
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Affiliation(s)
- Marcos Peñalver
- Laboratory of Intracellular Bacterial Pathogens, National Centre for Biotechnology (CNB-CSIC), Madrid, Spain
- Department of Molecular Biology, Universidad Autónoma de Madrid (UAM), Madrid, Spain
- Centro de Biologia Molecular Severo Ochoa (CBM), CSIC-UAM, Madrid, Spain
| | - Alberto Paradela
- Proteomics Facility, National Centre for Biotechnology (CNB-CSIC), Madrid, Spain
| | - César Palacios-Cuéllar
- Laboratory of Intracellular Bacterial Pathogens, National Centre for Biotechnology (CNB-CSIC), Madrid, Spain
| | - M Graciela Pucciarelli
- Laboratory of Intracellular Bacterial Pathogens, National Centre for Biotechnology (CNB-CSIC), Madrid, Spain
- Department of Molecular Biology, Universidad Autónoma de Madrid (UAM), Madrid, Spain
- Centro de Biologia Molecular Severo Ochoa (CBM), CSIC-UAM, Madrid, Spain
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Smith TE, Lee M, Person MD, Hesek D, Mobashery S, Moran NA. Horizontal-Acquisition of a Promiscuous Peptidoglycan-Recycling Enzyme Enables Aphids To Influence Symbiont Cell Wall Metabolism. mBio 2021; 12:e0263621. [PMID: 34933456 DOI: 10.1128/mBio.02636-21] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
During evolution, enzymes can undergo shifts in preferred substrates or in catalytic activities. An intriguing question is how enzyme function changes following horizontal gene transfer, especially for bacterial genes that have moved to animal genomes. Some insects have acquired genes that encode enzymes for the biosynthesis of bacterial cell wall components and that appear to function to support or control their obligate endosymbiotic bacteria. In aphids, the bacterial endosymbiont Buchnera aphidicola provides essential amino acids for aphid hosts but lacks most genes for remodeling of the bacterial cell wall. The aphid genome has acquired seven genes with putative functions in cell wall metabolism that are primarily expressed in the aphid cells harboring Buchnera. In analyses of aphid homogenates, we detected peptidoglycan (PGN) muropeptides indicative of the reactions of PGN hydrolases encoded by horizontally acquired aphid genes but not by Buchnera genes. We produced one such host enzyme, ApLdcA, and characterized its activity with both cell wall derived and synthetic PGN. Both ApLdcA and the homologous enzyme in Escherichia coli, which functions as an l,d-carboxypeptidase in the cytoplasmic PGN recycling pathway, exhibit turnover of PGN substrates containing stem pentapeptides and cross-linkages via l,d-endopeptidase activity, consistent with a potential role in cell wall remodeling. Our results suggest that ApLdcA derives its functions from the promiscuous activities of an ancestral LdcA enzyme, whose acquisition by the aphid genome may have enabled hosts to influence Buchnera cell wall metabolism as a means to control symbiont growth and division. IMPORTANCE Most enzymes are capable of performing biologically irrelevant side reactions. During evolution, promiscuous enzyme activities may acquire new biological roles, especially after horizontal gene transfer to new organisms. Pea aphids harbor obligate bacterial symbionts called Buchnera and encode horizontally acquired bacterial genes with putative roles in cell wall metabolism. Though Buchnera lacks cell wall endopeptidase genes, we found evidence of endopeptidase activity among peptidoglycan muropeptides purified from aphids. We characterized a multifunctional, aphid-encoded enzyme, ApLdcA, which displays l,d-endopeptidase activities considered promiscuous for the Escherichia coli homolog, for which these activities do not contribute to its native role in peptidoglycan recycling. These results exemplify the roles of enzyme promiscuity and horizontal gene transfer in enzyme evolution and demonstrate how aphids influence symbiont cell wall metabolism.
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Affiliation(s)
- Tetsuya Miyamoto
- Graduate School of Pharmaceutical Sciences, Kitasato University, 5-9-1 Shirokane, Minato-ku, Tokyo 108-8641, Japan
| | - Hiroshi Homma
- Graduate School of Pharmaceutical Sciences, Kitasato University, 5-9-1 Shirokane, Minato-ku, Tokyo 108-8641, Japan
| | - Tetsuya Miyamoto
- Graduate School of Pharmaceutical Sciences, Kitasato University, 5-9-1 Shirokane, Minato-ku, Tokyo 108-8641, Japan
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Liao L, Zhang Y, Wang Y, Fu Y, Zhang A, Qiu R, Yang S, Fang B. Construction and characterization of a novel glucose dehydrogenase-leucine dehydrogenase fusion enzyme for the biosynthesis of L-tert-leucine. Microb Cell Fact 2021; 20:3. [PMID: 33407464 PMCID: PMC7788806 DOI: 10.1186/s12934-020-01501-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2020] [Accepted: 12/23/2020] [Indexed: 11/24/2022] Open
Abstract
Background Biosynthesis of l-tert-leucine (l-tle), a significant pharmaceutical intermediate, by a cofactor regeneration system friendly and efficiently is a worthful goal all the time. The cofactor regeneration system of leucine dehydrogenase (LeuDH) and glucose dehydrogenase (GDH) has showed great coupling catalytic efficiency in the synthesis of l-tle, however the multi-enzyme complex of GDH and LeuDH has never been constructed successfully. Results In this work, a novel fusion enzyme (GDH–R3–LeuDH) for the efficient biosynthesis of l-tle was constructed by the fusion of LeuDH and GDH mediated with a rigid peptide linker. Compared with the free enzymes, both the environmental tolerance and thermal stability of GDH–R3–LeuDH had a great improved since the fusion structure. The fusion structure also accelerated the cofactor regeneration rate and maintained the enzyme activity, so the productivity and yield of l-tle by GDH–R3–LeuDH was all enhanced by twofold. Finally, the space–time yield of l-tle catalyzing by GDH–R3–LeuDH whole cells could achieve 2136 g/L/day in a 200 mL scale system under the optimal catalysis conditions (pH 9.0, 30 °C, 0.4 mM of NAD+ and 500 mM of a substrate including trimethylpyruvic acid and glucose). Conclusions It is the first report about the fusion of GDH and LeuDH as the multi-enzyme complex to synthesize l-tle and reach the highest space–time yield up to now. These results demonstrated the great potential of the GDH–R3–LeuDH fusion enzyme for the efficient biosynthesis of l-tle.
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Affiliation(s)
- Langxing Liao
- Department of Chemical and Biochemical Engineering, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, People's Republic of China
| | - Yonghui Zhang
- Department of Chemical and Biochemical Engineering, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, People's Republic of China.,College of Food and Biological Engineering, Jimei University, Xiamen, People's Republic of China
| | - Yali Wang
- Department of Chemical and Biochemical Engineering, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, People's Republic of China
| | - Yousi Fu
- Department of Chemical and Biochemical Engineering, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, People's Republic of China
| | - Aihui Zhang
- Department of Chemical and Biochemical Engineering, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, People's Republic of China
| | - Ruodian Qiu
- Department of Chemical and Biochemical Engineering, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, People's Republic of China
| | - Shuhao Yang
- Department of Chemical and Biochemical Engineering, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, People's Republic of China
| | - Baishan Fang
- Department of Chemical and Biochemical Engineering, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, People's Republic of China. .,The Key Lab for Synthetic Biotechnology of Xiamen City, Xiamen University, Xiamen, Fujian, People's Republic of China.
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Singh R, Slade JA, Brockett M, Mendez D, Liechti GW, Maurelli AT. Competing Substrates for the Bifunctional Diaminopimelic Acid Epimerase/Glutamate Racemase Modulate Peptidoglycan Synthesis in Chlamydia trachomatis. Infect Immun 2020; 89:IAI.00401-20. [PMID: 33106295 PMCID: PMC7927921 DOI: 10.1128/iai.00401-20] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2020] [Accepted: 10/21/2020] [Indexed: 11/20/2022] Open
Abstract
The Chlamydia trachomatis genome encodes multiple bifunctional enzymes, such as DapF, which is capable of both diaminopimelic acid (DAP) epimerase and glutamate racemase activity. Our previous work demonstrated the bifunctional activity of chlamydial DapF in vitro and in a heterologous system (Escherichia coli). In the present study, we employed a substrate competition strategy to demonstrate DapF Ct function in vivo in C. trachomatis We reasoned that, because DapF Ct utilizes a shared substrate-binding site for both racemase and epimerase activities, only one activity can occur at a time. Therefore, an excess of one substrate relative to another must determine which activity is favored. We show that the addition of excess l-glutamate or meso-DAP (mDAP) to C. trachomatis resulted in 90% reduction in bacterial titers, compared to untreated controls. Excess l-glutamate reduced in vivo synthesis of mDAP by C. trachomatis to undetectable levels, thus confirming that excess racemase substrate led to inhibition of DapF Ct DAP epimerase activity. We previously showed that expression of dapFCt in a murI (racemase) ΔdapF (epimerase) double mutant of E. coli rescues the d-glutamate auxotrophic defect. Addition of excess mDAP inhibited growth of this strain, but overexpression of dapFCt allowed the mutant to overcome growth inhibition. These results confirm that DapF Ct is the primary target of these mDAP and l-glutamate treatments. Our findings demonstrate that suppression of either the glutamate racemase or epimerase activity of DapF compromises the growth of C. trachomatis Thus, a substrate competition strategy can be a useful tool for in vivo validation of an essential bifunctional enzyme.
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Affiliation(s)
- Raghuveer Singh
- Emerging Pathogens Institute, University of Florida, Gainesville, Florida, USA
- Department of Environmental and Global Health, College of Public Health and Health Professions, University of Florida, Gainesville, Florida, USA
| | - Jessica A Slade
- Emerging Pathogens Institute, University of Florida, Gainesville, Florida, USA
- Department of Environmental and Global Health, College of Public Health and Health Professions, University of Florida, Gainesville, Florida, USA
| | - Mary Brockett
- Department of Microbiology and Immunology, Uniformed Services University of the Health Sciences, Bethesda, Maryland, USA
| | - Daniel Mendez
- Emerging Pathogens Institute, University of Florida, Gainesville, Florida, USA
- Department of Environmental and Global Health, College of Public Health and Health Professions, University of Florida, Gainesville, Florida, USA
| | - George W Liechti
- Department of Microbiology and Immunology, Uniformed Services University of the Health Sciences, Bethesda, Maryland, USA
| | - Anthony T Maurelli
- Emerging Pathogens Institute, University of Florida, Gainesville, Florida, USA
- Department of Environmental and Global Health, College of Public Health and Health Professions, University of Florida, Gainesville, Florida, USA
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Maitra A, Munshi T, Healy J, Martin LT, Vollmer W, Keep NH, Bhakta S. Cell wall peptidoglycan in Mycobacterium tuberculosis: An Achilles' heel for the TB-causing pathogen. FEMS Microbiol Rev 2020; 43:548-575. [PMID: 31183501 PMCID: PMC6736417 DOI: 10.1093/femsre/fuz016] [Citation(s) in RCA: 89] [Impact Index Per Article: 22.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2019] [Accepted: 06/07/2019] [Indexed: 02/06/2023] Open
Abstract
Tuberculosis (TB), caused by the intracellular pathogen Mycobacterium tuberculosis, remains one of the leading causes of mortality across the world. There is an urgent requirement to build a robust arsenal of effective antimicrobials, targeting novel molecular mechanisms to overcome the challenges posed by the increase of antibiotic resistance in TB. Mycobacterium tuberculosis has a unique cell envelope structure and composition, containing a peptidoglycan layer that is essential for maintaining cellular integrity and for virulence. The enzymes involved in the biosynthesis, degradation, remodelling and recycling of peptidoglycan have resurfaced as attractive targets for anti-infective drug discovery. Here, we review the importance of peptidoglycan, including the structure, function and regulation of key enzymes involved in its metabolism. We also discuss known inhibitors of ATP-dependent Mur ligases, and discuss the potential for the development of pan-enzyme inhibitors targeting multiple Mur ligases.
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Affiliation(s)
- Arundhati Maitra
- Mycobacteria Research Laboratory, Institute of Structural and Molecular Biology, Department of Biological Sciences, Birkbeck, University of London, Malet Street, London WC1E 7HX, UK
| | - Tulika Munshi
- Mycobacteria Research Laboratory, Institute of Structural and Molecular Biology, Department of Biological Sciences, Birkbeck, University of London, Malet Street, London WC1E 7HX, UK
| | - Jess Healy
- Department of Pharmaceutical and Biological Chemistry, UCL School of Pharmacy, 29-39 Brunswick Square, London WC1N 1AX, UK
| | - Liam T Martin
- Mycobacteria Research Laboratory, Institute of Structural and Molecular Biology, Department of Biological Sciences, Birkbeck, University of London, Malet Street, London WC1E 7HX, UK
| | - Waldemar Vollmer
- The Centre for Bacterial Cell Biology, Institute for Cell and Molecular Biosciences, Newcastle University, Richardson Road, Newcastle upon Tyne, NE2 4AX, UK
| | - Nicholas H Keep
- Mycobacteria Research Laboratory, Institute of Structural and Molecular Biology, Department of Biological Sciences, Birkbeck, University of London, Malet Street, London WC1E 7HX, UK
| | - Sanjib Bhakta
- Mycobacteria Research Laboratory, Institute of Structural and Molecular Biology, Department of Biological Sciences, Birkbeck, University of London, Malet Street, London WC1E 7HX, UK
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Collingro A, Köstlbacher S, Horn M. Chlamydiae in the Environment. Trends Microbiol 2020; 28:877-88. [PMID: 32591108 DOI: 10.1016/j.tim.2020.05.020] [Citation(s) in RCA: 49] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2020] [Revised: 05/25/2020] [Accepted: 05/28/2020] [Indexed: 12/19/2022]
Abstract
Chlamydiae have been known for more than a century as major pathogens of humans. Yet they are also found ubiquitously in the environment where they thrive within protists and in an unmatched wide range of animals. This review summarizes recent advances in understanding chlamydial diversity and distribution in nature. Studying these environmental chlamydiae provides a novel perspective on basic chlamydial biology and evolution. A picture is beginning to emerge with chlamydiae representing one of the evolutionarily most ancient and successful groups of obligate intracellular bacteria.
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Lin JC, Wang XZ, Shen T, Zhang JY. iTRAQ-based quantitative analysis reveals the mechanism underlying the changes in physiological activity in a glutamate racemase mutant strain of Streptococcus mutans UA159. Mol Biol Rep 2020; 47:3719-3733. [PMID: 32338332 DOI: 10.1007/s11033-020-05463-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2020] [Accepted: 04/17/2020] [Indexed: 11/30/2022]
Abstract
Streptococcus mutans UA159 is responsible for human dental caries with robust cariogenic potential. Our previous study noted that a glutamate racemase (MurI) mutant strain (designated S. mutans FW1718), with the hereditary background of UA159, displayed alterations of morphogenesis, attenuated stress tolerance, and weakened biofilm-forming capabilities, accompanying with unclear mechanisms. In this study, we applied isobaric tags for relative and absolute quantitation (iTRAQ)-based proteomics to characterize the proteome profiles of the murI mutant strain vs. the wild-type strain in chemically defined media to elucidate the mechanisms by which S. mutans copes with MurI deficiency. Whole-cell proteins of S. mutans FW1718 and UA159 were assessed by iTRAQ-coupled LC-ESI-MS/MS. Furthermore, differentially expressed proteins (DEPs) were identified by Mascot, Gene Ontology (GO) annotation, Cluster of Orthologous Groups of proteins (COG), and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses. Finally, a protein-protein interaction (PPI) network was established using the Search Tool for the Retrieval of Interacting Genes/Proteins (STRING). Among 1173 total bacterial proteins identified, 112 DEPs exhibited altered expression patterns in S. mutans UA159 with or without the murI mutation. The ΔmurI cells displayed an increase in the relative expression of 93 proteins (fold change ≥ 1.2, p < 0.05) and a decrease in 29 proteins (fold change ≤ 0.833, p < 0.05) compared with the wild-type cells. PPI analysis revealed a complex network of DEPs containing 191 edges and 122 nodes. The DEPs significantly upregulated after murI knockout had roles in diverse functional processes spanning cell-wall biosynthesis, energy production, and DNA replication and repair. We identified distinct variations and diverse modulators caused by murI mutation in the proteome of S. mutans, indicating that the modification of cell membrane structure, redistribution of energy metabolism and enhanced nucleic acid machinery contributed to the S. mutans response to specific environmental contexts.
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Affiliation(s)
- Jia-Cheng Lin
- Department of Pediatric Dentistry, Guanghua School of Stomatology, Affiliated Stomatological Hospital, Guangdong Provincial Key Laboratory of Stomatology, Sun Yat-sen University, Guangzhou, Guangdong, China
| | - Xiang-Zhu Wang
- Operative Dentistry and Endodontics, Xiangya School of Stomatology, Xiangya Stomatological Hospital, Central South University, Changsha, Hunan, China
| | - Ting Shen
- Operative Dentistry and Endodontics, Xiangya School of Stomatology, Xiangya Stomatological Hospital, Central South University, Changsha, Hunan, China
| | - Jian-Ying Zhang
- Operative Dentistry and Endodontics, Xiangya School of Stomatology, Xiangya Stomatological Hospital, Central South University, Changsha, Hunan, China.
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Singh R, Liechti G, Slade JA, Maurelli AT. Chlamydia trachomatis Oligopeptide Transporter Performs Dual Functions of Oligopeptide Transport and Peptidoglycan Recycling. Infect Immun 2020; 88:e00086-20. [PMID: 32094256 DOI: 10.1128/IAI.00086-20] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2020] [Accepted: 02/18/2020] [Indexed: 12/20/2022] Open
Abstract
Peptidoglycan, the sugar-amino acid polymer that composes the bacterial cell wall, requires a significant expenditure of energy to synthesize and is highly immunogenic. To minimize the loss of an energetically expensive metabolite and avoid host detection, bacteria often recycle their peptidoglycan, transporting its components back into the cytoplasm, where they can be used for subsequent rounds of new synthesis. The peptidoglycan-recycling substrate binding protein (SBP) MppA, which is responsible for recycling peptidoglycan fragments in Escherichia coli, has not been annotated for most intracellular pathogens. One such pathogen, Chlamydia trachomatis, has a limited capacity to synthesize amino acids de novo and therefore must obtain oligopeptides from its host cell for growth. Bioinformatics analysis suggests that the putative C. trachomatis oligopeptide transporter OppABCDF (OppABCDF Ct ) encodes multiple SBPs (OppA1 Ct , OppA2 Ct , and OppA3 Ct ). Intracellular pathogens often encode multiple SBPs, while only one, OppA, is encoded in the E. coli opp operon. We hypothesized that the putative OppABCDF transporter of C. trachomatis functions in both oligopeptide transport and peptidoglycan recycling. We coexpressed the putative SBP genes (oppA1Ct , oppA2Ct , oppA3Ct ) along with oppBCDFCt in an E. coli mutant lacking the Opp transporter and determined that all three chlamydial OppA subunits supported oligopeptide transport. We also demonstrated the in vivo functionality of the chlamydial Opp transporter in C. trachomatis Importantly, we found that one chlamydial SBP, OppA3 Ct , possessed dual substrate recognition properties and is capable of transporting peptidoglycan fragments (tri-diaminopimelic acid) in E. coli and in C. trachomatis These findings suggest that Chlamydia evolved an oligopeptide transporter to facilitate the acquisition of oligopeptides for growth while simultaneously reducing the accumulation of immunostimulatory peptidoglycan fragments in the host cell cytosol. The latter property reflects bacterial pathoadaptation that dampens the host innate immune response to Chlamydia infection.
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Glasner ME, Truong DP, Morse BC. How enzyme promiscuity and horizontal gene transfer contribute to metabolic innovation. FEBS J 2020; 287:1323-1342. [PMID: 31858709 DOI: 10.1111/febs.15185] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2019] [Revised: 11/22/2019] [Accepted: 12/18/2019] [Indexed: 01/12/2023]
Abstract
Promiscuity is the coincidental ability of an enzyme to catalyze its native reaction and additional reactions that are not biological functions in the same active site. Promiscuity plays a central role in enzyme evolution and is thus a useful property for protein and metabolic engineering. This review examines enzyme evolution holistically, beginning with evaluating biochemical support for four enzyme evolution models. As expected, there is strong biochemical support for the subfunctionalization and innovation-amplification-divergence models, in which promiscuity is a central feature. In many cases, however, enzyme evolution is more complex than the models indicate, suggesting much is yet to be learned about selective pressures on enzyme function. A complete understanding of enzyme evolution must also explain the ability of metabolic networks to integrate new enzyme activities. Hidden within metabolic networks are underground metabolic pathways constructed from promiscuous activities. We discuss efforts to determine the diversity and pervasiveness of underground metabolism. Remarkably, several studies have discovered that some metabolic defects can be repaired via multiple underground routes. In prokaryotes, metabolic innovation is driven by connecting enzymes acquired by horizontal gene transfer (HGT) into the metabolic network. Thus, we end the review by discussing how the combination of promiscuity and HGT contribute to evolution of metabolism in prokaryotes. Future studies investigating the contribution of promiscuity to enzyme and metabolic evolution will need to integrate deeper probes into the influence of evolution on protein biophysics, enzymology, and metabolism with more complex and realistic evolutionary models. ENZYMES: lactate dehydrogenase (EC 1.1.1.27), malate dehydrogenase (EC 1.1.1.37), OSBS (EC 4.2.1.113), HisA (EC 5.3.1.16), TrpF, PriA (EC 5.3.1.24), R-mandelonitrile lyase (EC 4.1.2.10), Maleylacetate reductase (EC 1.3.1.32).
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Affiliation(s)
- Margaret E Glasner
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX, USA
| | - Dat P Truong
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX, USA
| | - Benjamin C Morse
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX, USA
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Wang X, Chen C, Shen T, Zhang J. Heterologous expression, purification and biochemical characterization of a glutamate racemase (MurI) from Streptococcus mutans UA159. PeerJ 2019; 7:e8300. [PMID: 31875162 PMCID: PMC6927343 DOI: 10.7717/peerj.8300] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2019] [Accepted: 11/26/2019] [Indexed: 01/03/2023] Open
Abstract
Background Glutamate racemase (MurI) is a cofactor-independent enzyme that is essential to the bacterial peptidoglycan biosynthesis pathway and has therefore been considered an attractive target for the development of antimicrobial drugs. While in our previous study the essentiality of the murI gene was shown in Streptococcus mutans, the primary aetiologic agent of human dental caries, studies on S. mutans MurI have not yet provided definitive results. This study aimed to produce and characterize the biochemical properties of the MurI from the S. mutans UA159 genome. Methods Structure characterization prediction and multiple sequence alignment were performed by bioinformatic analysis. Recombinant His6-tagged S. mutans MurI was overexpressed in the expression vector pColdII and further purified using a Ni2+ affinity chromatography method. Protein solubility, purity and aggregation state were analyzed by SDS–PAGE, Western blotting, native PAGE and SEC-HPLC. Kinetic parameters were assessed by a circular dichroism (CD) assay. Kinetic constants were calculated based on the curve fit for the Michaelis–Menten equation. The effects of temperature and pH on enzymatic activity were determined by a series of coupled enzyme reaction mixtures. Results The glutamate racemase gene from S. mutans UA159 was amplified by PCR, cloned and expressed in Escherichia coli BL21 (DE3). The 264-amino-acid protein, as a mixture of dimeric and monomeric enzymes, was purified to electrophoretic homogeneity. In the CD assay, S. mutans MurI displayed unique kinetic parameters (Km, d-Glu→l-Glu = 0.3631 ± 0.3205 mM, Vmax, d-Glu→l-Glu = 0.1963 ± 0.0361 mM min−1, kcat, d-Glu→l-Glu = 0.0306 ± 0.0065 s−1, kcat/Km,d-Glu→l-Glu = 0.0844 ± 0.0128 s−1 mM−1, with d-glutamate as substrate; Km, l-Glu→d-Glu = 0.8077 ± 0.5081 mM, Vmax, l-Glu→d-Glu = 0.2421 ± 0.0418 mM min−1, kcat,l-Glu→d-Glu = 0.0378 ± 0.0056 s−1, kcat/Km,l-Glu→d-Glu = 0.0468 ± 0.0176 s−1 mM−1, with l-glutamate as substrate). S. mutans MurI possessed an assay temperature optimum of 37.5 °C and its optimum pH was 8.0. Conclusion The findings of this study provide insight into the structure and biochemical traits of the glutamate racemase in S. mutans and supply a conceivable guideline for employing glutamate racemase in anti-caries drug design.
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Affiliation(s)
- Xiangzhu Wang
- Department of Operative Dentistry and Endodotics, Xiangya School of Stomatology, Xiangya Stomatological Hospital, Central South University, Changsha, Hunan, China
| | - Chanchan Chen
- Department of Stomatology, Shenzhen Children's Hospital, Shenzhen, Guangdong, China
| | - Ting Shen
- Department of Operative Dentistry and Endodotics, Xiangya School of Stomatology, Xiangya Stomatological Hospital, Central South University, Changsha, Hunan, China
| | - Jiangying Zhang
- Department of Operative Dentistry and Endodotics, Xiangya School of Stomatology, Xiangya Stomatological Hospital, Central South University, Changsha, Hunan, China
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Bublitz DC, Chadwick GL, Magyar JS, Sandoz KM, Brooks DM, Mesnage S, Ladinsky MS, Garber AI, Bjorkman PJ, Orphan VJ, McCutcheon JP. Peptidoglycan Production by an Insect-Bacterial Mosaic. Cell 2019; 179:703-712.e7. [PMID: 31587897 PMCID: PMC6838666 DOI: 10.1016/j.cell.2019.08.054] [Citation(s) in RCA: 57] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2019] [Revised: 08/06/2019] [Accepted: 08/28/2019] [Indexed: 01/19/2023]
Abstract
Peptidoglycan (PG) is a defining feature of bacteria, involved in cell division, shape, and integrity. We previously reported that several genes related to PG biosynthesis were horizontally transferred from bacteria to the nuclear genome of mealybugs. Mealybugs are notable for containing a nested bacteria-within-bacterium endosymbiotic structure in specialized insect cells, where one bacterium, Moranella, lives in the cytoplasm of another bacterium, Tremblaya. Here we show that horizontally transferred genes on the mealybug genome work together with genes retained on the Moranella genome to produce a PG layer exclusively at the Moranella cell periphery. Furthermore, we show that an insect protein encoded by a horizontally transferred gene of bacterial origin is transported into the Moranella cytoplasm. These results provide a striking parallel to the genetic and biochemical mosaicism found in organelles, and prove that multiple horizontally transferred genes can become integrated into a functional pathway distributed between animal and bacterial endosymbiont genomes. Mealybugs have two bacterial endosymbionts; one symbiont lives inside the other The mealybug genome has acquired some bacterial peptidoglycan (PG)-related genes This insect-symbiont mosaic pathway produces a PG layer at the innermost symbiont Endosymbionts and organelles have evolved similar levels of biochemical integration
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Affiliation(s)
- DeAnna C Bublitz
- Division of Biological Sciences, University of Montana, Missoula, MT 59812, USA
| | - Grayson L Chadwick
- Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA
| | - John S Magyar
- Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA
| | - Kelsi M Sandoz
- Coxiella Pathogenesis Section, Laboratory of Bacteriology, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, NIH, Hamilton, MT 59840, USA
| | - Diane M Brooks
- Division of Biological Sciences, University of Montana, Missoula, MT 59812, USA
| | - Stéphane Mesnage
- Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield S10 2TN, UK
| | - Mark S Ladinsky
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - Arkadiy I Garber
- Division of Biological Sciences, University of Montana, Missoula, MT 59812, USA
| | - Pamela J Bjorkman
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - Victoria J Orphan
- Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA
| | - John P McCutcheon
- Division of Biological Sciences, University of Montana, Missoula, MT 59812, USA.
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Amin SA, Chavez E, Porokhin V, Nair NU, Hassoun S. Towards creating an extended metabolic model (EMM) for E. coli using enzyme promiscuity prediction and metabolomics data. Microb Cell Fact 2019; 18:109. [PMID: 31196115 PMCID: PMC6567437 DOI: 10.1186/s12934-019-1156-3] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2019] [Accepted: 06/05/2019] [Indexed: 01/26/2023] Open
Abstract
Background Metabolic models are indispensable in guiding cellular engineering and in advancing our understanding of systems biology. As not all enzymatic activities are fully known and/or annotated, metabolic models remain incomplete, resulting in suboptimal computational analysis and leading to unexpected experimental results. We posit that one major source of unaccounted metabolism is promiscuous enzymatic activity. It is now well-accepted that most, if not all, enzymes are promiscuous—i.e., they transform substrates other than their primary substrate. However, there have been no systematic analyses of genome-scale metabolic models to predict putative reactions and/or metabolites that arise from enzyme promiscuity. Results Our workflow utilizes PROXIMAL—a tool that uses reactant–product transformation patterns from the KEGG database—to predict putative structural modifications due to promiscuous enzymes. Using iML1515 as a model system, we first utilized a computational workflow, referred to as Extended Metabolite Model Annotation (EMMA), to predict promiscuous reactions catalyzed, and metabolites produced, by natively encoded enzymes in Escherichia coli. We predict hundreds of new metabolites that can be used to augment iML1515. We then validated our method by comparing predicted metabolites with the Escherichia coli Metabolome Database (ECMDB). Conclusions We utilized EMMA to augment the iML1515 metabolic model to more fully reflect cellular metabolic activity. This workflow uses enzyme promiscuity as basis to predict hundreds of reactions and metabolites that may exist in E. coli but may have not been documented in iML1515 or other databases. We provide detailed analysis of 23 predicted reactions and 16 associated metabolites. Interestingly, nine of these metabolites, which are in ECMDB, have not previously been documented in any other E. coli databases. Four of the predicted reactions provide putative transformations parallel to those already in iML1515. We suggest adding predicted metabolites and reactions to iML1515 to create an extended metabolic model (EMM) for E. coli. Electronic supplementary material The online version of this article (10.1186/s12934-019-1156-3) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Sara A Amin
- Department of Computer Science, Tufts University, Medford, MA, USA
| | - Elizabeth Chavez
- Department of Biology, University of North Carolina, Chapel Hill, NC, USA
| | | | - Nikhil U Nair
- Department of Chemical and Biological Engineering, Tufts University, Medford, MA, USA.
| | - Soha Hassoun
- Department of Computer Science, Tufts University, Medford, MA, USA. .,Department of Chemical and Biological Engineering, Tufts University, Medford, MA, USA.
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Shields RC, Jensen PA. The bare necessities: Uncovering essential and condition-critical genes with transposon sequencing. Mol Oral Microbiol 2019; 34:39-50. [PMID: 30739386 DOI: 10.1111/omi.12256] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2018] [Revised: 01/18/2019] [Accepted: 02/06/2019] [Indexed: 12/11/2022]
Abstract
Querying gene function in bacteria has been greatly accelerated by the advent of transposon sequencing (Tn-seq) technologies (related Tn-seq strategies are known as TraDIS, INSeq, RB-TnSeq, and HITS). Pooled populations of transposon mutants are cultured in an environment and next-generation sequencing tools are used to determine areas of the genome that are important for bacterial fitness. In this review we provide an overview of Tn-seq methodologies and discuss how Tn-seq has been applied, or could be applied, to the study of oral microbiology. These applications include studying the essential genome as a means to rationally design therapeutic agents. Tn-seq has also contributed to our understanding of well-studied biological processes in oral bacteria. Other important applications include in vivo pathogenesis studies and use of Tn-seq to probe the molecular basis of microbial interactions. We also highlight recent advancements in techniques that act in synergy with Tn-seq such as clustered regularly interspaced short palindromic repeats (CRISPR) interference and microfluidic chip platforms.
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Affiliation(s)
- Robert C Shields
- Department of Oral Biology, College of Dentistry, University of Florida, Gainesville, Florida
| | - Paul A Jensen
- Department of Bioengineering and Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois
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Rosenberg J, Commichau FM. Harnessing Underground Metabolism for Pathway Development. Trends Biotechnol 2019; 37:29-37. [DOI: 10.1016/j.tibtech.2018.08.001] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2018] [Revised: 07/17/2018] [Accepted: 08/06/2018] [Indexed: 01/13/2023]
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16
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Miyamoto T, Katane M, Saitoh Y, Sekine M, Homma H. Elucidation of the d-lysine biosynthetic pathway in the hyperthermophile Thermotoga maritima. FEBS J 2018; 286:601-614. [PMID: 30548096 DOI: 10.1111/febs.14720] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2018] [Revised: 10/29/2018] [Accepted: 12/03/2018] [Indexed: 12/31/2022]
Abstract
Various d-amino acids are involved in peptidoglycan and biofilm metabolism in bacteria, suggesting that these compounds are necessary for successful adaptation to environmental changes. In addition to the conventional d-alanine (d-Ala) and d-glutamate, the peptidoglycan of the hyperthermophilic bacterium Thermotoga maritima contains both l-lysine (l-Lys) and d-Lys, but not meso-diaminopimelate (meso-Dpm). d-Lys is an uncommon component of peptidoglycan, and its biosynthetic pathway remains unclear. In this study, we identified and characterized a novel Lys racemase (TM1597) and Dpm epimerase (TM1522) associated with the d-Lys biosynthetic pathway in T. maritima. The Lys racemase had a dimeric structure containing pyridoxal 5'-phosphate as a cofactor. Among the amino acids, it exhibited the highest racemase activity toward d- and l-Lys, and also had relatively high activity toward d- and l-enantiomers of ornithine and Ala. The Dpm epimerase had the highest epimerization activity toward ll- and meso-Dpm, and also measurably racemized certain amino acids, including Lys. These results suggest that Lys racemase contributes to production of d-Lys and d-Ala for use as peptidoglycan components, and that Dpm epimerase converts ll-Dpm to meso-Dpm, a precursor in the l-Lys biosynthetic pathway.
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Affiliation(s)
- Tetsuya Miyamoto
- Graduate School of Pharmaceutical Sciences, Kitasato University, Tokyo, Japan
| | - Masumi Katane
- Graduate School of Pharmaceutical Sciences, Kitasato University, Tokyo, Japan
| | - Yasuaki Saitoh
- Graduate School of Pharmaceutical Sciences, Kitasato University, Tokyo, Japan
| | - Masae Sekine
- Graduate School of Pharmaceutical Sciences, Kitasato University, Tokyo, Japan
| | - Hiroshi Homma
- Graduate School of Pharmaceutical Sciences, Kitasato University, Tokyo, Japan
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Mackie J, Kumar H, Bearne SL. Changes in quaternary structure cause a kinetic asymmetry of glutamate racemase-catalyzed homocysteic acid racemization. FEBS Lett 2018; 592:3399-3413. [PMID: 30194685 DOI: 10.1002/1873-3468.13248] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2018] [Revised: 07/30/2018] [Accepted: 08/24/2018] [Indexed: 11/07/2022]
Abstract
Glutamate racemases (GR) catalyze the racemization of d- and l-glutamate and are targets for the development of antibiotics. We demonstrate that GR from the periodontal pathogen Fusobacterium nucleatum (FnGR) catalyzes the racemization of d-homocysteic acid (d-HCA), while l-HCA is a poor substrate. This enantioselectivity arises because l-HCA perturbs FnGR's monomer-dimer equilibrium toward inactive monomer. The inhibitory effect of l-HCA may be overcome by increasing the total FnGR concentration or by adding glutamate, but not by blocking access to the active site through site-directed mutagenesis, suggesting that l-HCA binds at an allosteric site. This phenomenon is also exhibited by GR from Bacillus subtilis, suggesting that enantiospecific, "substrate"-induced dissociation of oligomers to form inactive monomers may furnish a new inhibition strategy.
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Affiliation(s)
- Joanna Mackie
- Department of Biochemistry & Molecular Biology, Dalhousie University, Halifax, Canada
| | - Himank Kumar
- Department of Biochemistry & Molecular Biology, Dalhousie University, Halifax, Canada
| | - Stephen L Bearne
- Department of Biochemistry & Molecular Biology, Dalhousie University, Halifax, Canada.,Department of Chemistry, Dalhousie University, Halifax, Canada
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