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Kumar A, Anjum F, Hassan MI, Shamsi A, Singh RP. Identification and prioritization of novel therapeutic candidates against glutamate racemase from Klebsiella pneumoniae. PLoS One 2025; 20:e0317622. [PMID: 39913383 PMCID: PMC11801594 DOI: 10.1371/journal.pone.0317622] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2024] [Accepted: 12/31/2024] [Indexed: 02/09/2025] Open
Abstract
BACKGROUND Klebsiella pneumoniae, a gram-negative bacterium in the Enterobacteriaceae family, is non-motile, encapsulated, and a major cause of nosocomial infections, particularly in intensive care units. The bacterium possesses a thick polysaccharide capsule and fimbriae, which contribute to its virulence, resistance to phagocytosis, and attachment to host cells. The bacterium has developed serious resistance to most antibiotics currently in use. OBJECTIVE This study aims to investigate the structural properties of MurI (glutamate racemase) from Klebsiella pneumoniae and to identify potential candidate inhibitors against the protein, which will help in the development of new strategies to combat the infections related to MDR strains of Klebsiella pneumoniae. METHODS The 3D structure of the protein was modelled using SWISS-MODEL, which utilizes the homology modelling technique. After refinement, the structure was subjected to virtual high throughput screening on the TACC server using Enamine AC collection. The obtained molecules were then put through various screening parameters to obtain promising lead candidates, and the selected molecules were then subjected to MD simulations. The data obtained from MD simulations was then assessed with the help of different global dynamics analyses. The protein-ligand complexes were also subjected to MM/PBSA-based binding free energy calculation using the g_mmpbsa program. RESULTS The screening parameters employed on the molecules obtained via virtual screening from the TACC server revealed that Z1542321346 and Z2356864560 out of four molecules have better potential to act as potential inhibitors for MurI protein. The binding free energy values, which came out to be -27.26±3.06 kcal/mol and -29.53±4.29 kcal/mol for Z1542321346 and Z2356864560 molecules, respectively, favoured these molecules in terms of inhibition potential towards targeted protein. CONCLUSION The investigation of MurI via computational approach and the subsequent analysis of potential inhibitors can pave the way for developing new therapeutic strategies to combat the infections and antibiotic resistance of Klebsiella pneumoniae. This study could significantly help the medical fraternity in the treatment of infections caused by this multidrug-resistant pathogen.
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Affiliation(s)
- Ankit Kumar
- Department of Biotechnology, Sharda School of Engineering and Technology, Sharda University, Greater Noida, Uttar Pradesh, India
| | - Farah Anjum
- Department of Clinical Laboratory Sciences, College of Applied Medical Sciences, Taif University, Taif, Saudi Arabia
| | - Md Imtaiyaz Hassan
- Centre for Interdisciplinary Research in Basic Sciences, Jamia Millia Islamia, New Delhi, India
| | - Anas Shamsi
- Centre of Medical and Bio-Allied Health Sciences Research, Ajman University, Ajman, United Arab Emirates
| | - Rashmi Prabha Singh
- Department of Life Science, Sharda School of Basic Sciences and Research, Sharda University, Greater Noida, Uttar Pradesh, India
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Nguyen A, Roy JJS, Kim JH, Yun KH, Lee W, Kim KK, Kim T, Chaurasia AK. Repeated Exposure of Vancomycin to Vancomycin-Susceptible Staphylococcus aureus (VSSA) Parent Emerged VISA and VRSA Strains with Enhanced Virulence Potentials. J Microbiol 2024; 62:535-553. [PMID: 38814539 DOI: 10.1007/s12275-024-00139-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2023] [Revised: 04/18/2024] [Accepted: 04/21/2024] [Indexed: 05/31/2024]
Abstract
The emergence of resistance against the last-resort antibiotic vancomycin in staphylococcal infections is a serious concern for human health. Although various drug-resistant pathogens of diverse genetic backgrounds show higher virulence potential, the underlying mechanism behind this is not yet clear due to variability in their genetic dispositions. In this study, we investigated the correlation between resistance and virulence in adaptively evolved isogenic strains. The vancomycin-susceptible Staphylococcus aureus USA300 was exposed to various concentrations of vancomycin repeatedly as a mimic of the clinical regimen to obtain mutation(s)-accrued-clonally-selected (MACS) strains. The phenotypic analyses followed by expression of the representative genes responsible for virulence and resistance of MACS strains were investigated. MACS strains obtained under 2 and 8 µg/ml vancomycin, named Van2 and Van8, respectively; showed enhanced vancomycin minimal inhibitory concentrations (MIC) to 4 and 16 µg/ml, respectively. The cell adhesion and invasion of MACS strains increased in proportion to their MICs. The correlation between resistance and virulence potential was partially explained by the differential expression of genes known to be involved in both virulence and resistance in MACS strains compared to parent S. aureus USA300. Repeated treatment of vancomycin against vancomycin-susceptible S. aureus (VSSA) leads to the emergence of vancomycin-resistant strains with variable levels of enhanced virulence potentials.
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Affiliation(s)
- An Nguyen
- Department of Precision Medicine, Graduate School of Basic Medical Science (GSBMS), Institute for Antimicrobial Resistance Research and Therapeutics, Sungkyunkwan University School of Medicine, Suwon, 16419, Republic of Korea
- Department of Biophysics, Sungkyunkwan University, Suwon, 16419, Republic of Korea
| | - J Jean Sophy Roy
- Department of Precision Medicine, Graduate School of Basic Medical Science (GSBMS), Institute for Antimicrobial Resistance Research and Therapeutics, Sungkyunkwan University School of Medicine, Suwon, 16419, Republic of Korea
| | - Ji-Hoon Kim
- School of Pharmacy, Sungkyunkwan University, Suwon, 16419, Republic of Korea
| | - Kyung-Hee Yun
- Department of Precision Medicine, Graduate School of Basic Medical Science (GSBMS), Institute for Antimicrobial Resistance Research and Therapeutics, Sungkyunkwan University School of Medicine, Suwon, 16419, Republic of Korea
| | - Wonsik Lee
- School of Pharmacy, Sungkyunkwan University, Suwon, 16419, Republic of Korea
| | - Kyeong Kyu Kim
- Department of Precision Medicine, Graduate School of Basic Medical Science (GSBMS), Institute for Antimicrobial Resistance Research and Therapeutics, Sungkyunkwan University School of Medicine, Suwon, 16419, Republic of Korea.
- Department of Biophysics, Sungkyunkwan University, Suwon, 16419, Republic of Korea.
| | - Truc Kim
- Department of Precision Medicine, Graduate School of Basic Medical Science (GSBMS), Institute for Antimicrobial Resistance Research and Therapeutics, Sungkyunkwan University School of Medicine, Suwon, 16419, Republic of Korea.
| | - Akhilesh Kumar Chaurasia
- Department of Precision Medicine, Graduate School of Basic Medical Science (GSBMS), Institute for Antimicrobial Resistance Research and Therapeutics, Sungkyunkwan University School of Medicine, Suwon, 16419, Republic of Korea.
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Qun T, Zhou T, Hao J, Wang C, Zhang K, Xu J, Wang X, Zhou W. Antibacterial activities of anthraquinones: structure-activity relationships and action mechanisms. RSC Med Chem 2023; 14:1446-1471. [PMID: 37593578 PMCID: PMC10429894 DOI: 10.1039/d3md00116d] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2023] [Accepted: 05/24/2023] [Indexed: 08/19/2023] Open
Abstract
With the increasing prevalence of untreatable infections caused by antibiotic-resistant bacteria, the discovery of new drugs from natural products has become a hot research topic. The antibacterial activity of anthraquinones widely distributed in traditional Chinese medicine has attracted much attention. Herein, the structure and activity relationships (SARs) of anthraquinones as bacteriostatic agents are reviewed and elucidated. The substituents of anthraquinone and its derivatives are closely related to their antibacterial activities. The stronger the polarity of anthraquinone substituents is, the more potent the antibacterial effects appear. The presence of hydroxyl groups is not necessary for the antibacterial activity of hydroxyanthraquinone derivatives. Substitution of di-isopentenyl groups can improve the antibacterial activity of anthraquinone derivatives. The rigid plane structure of anthraquinone lowers its water solubility and results in the reduced activity. Meanwhile, the antibacterial mechanisms of anthraquinone and its analogs are explored, mainly including biofilm formation inhibition, destruction of the cell wall, endotoxin inhibition, inhibition of nucleic acid and protein synthesis, and blockage of energy metabolism and other substances.
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Affiliation(s)
- Tang Qun
- Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences 200241 Shanghai China
| | - Tiantian Zhou
- School of Chinese Materia Medica, Guangdong Pharmaceutical University 440113 Guangzhou China
| | - Jiongkai Hao
- Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences 200241 Shanghai China
| | - Chunmei Wang
- Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences 200241 Shanghai China
- Key laboratory of Veterinary Chemical Drugs and Pharmaceutics, Ministry of Agriculture and Rural Affairs, Shanghai Research Institute, Chinese Academy of Agricultural Sciences Shanghai 200241 China
| | - Keyu Zhang
- Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences 200241 Shanghai China
- Key laboratory of Veterinary Chemical Drugs and Pharmaceutics, Ministry of Agriculture and Rural Affairs, Shanghai Research Institute, Chinese Academy of Agricultural Sciences Shanghai 200241 China
| | - Jing Xu
- Huanghua Agricultural and Rural Development Bureau Bohai New Area 061100 Hebei China
| | - Xiaoyang Wang
- Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences 200241 Shanghai China
- Key laboratory of Veterinary Chemical Drugs and Pharmaceutics, Ministry of Agriculture and Rural Affairs, Shanghai Research Institute, Chinese Academy of Agricultural Sciences Shanghai 200241 China
| | - Wen Zhou
- Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences 200241 Shanghai China
- Key laboratory of Veterinary Chemical Drugs and Pharmaceutics, Ministry of Agriculture and Rural Affairs, Shanghai Research Institute, Chinese Academy of Agricultural Sciences Shanghai 200241 China
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Bearne SL. Design and evaluation of substrate-product analog inhibitors for racemases and epimerases utilizing a 1,1-proton transfer mechanism. Methods Enzymol 2023; 690:397-444. [PMID: 37858537 DOI: 10.1016/bs.mie.2023.06.014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2023]
Abstract
Racemases and epimerases catalyze the inversion of stereochemistry at asymmetric carbon atoms to generate stereoisomers that often play important roles in normal and pathological physiology. Consequently, there is interest in developing inhibitors of these enzymes for drug discovery. A strategy for the rational design of substrate-product analog (SPA) inhibitors of racemases and epimerases utilizing a direct 1,1-proton transfer mechanism is elaborated. This strategy assumes that two groups on the asymmetric carbon atom remain fixed at active-site binding determinants, while the hydrogen and third, motile group move during catalysis, with the latter potentially traveling between an R- and S-pocket at the active site. SPAs incorporate structural features of the substrate and product, often with geminal disubstitution on the asymmetric carbon atom to simultaneously present the motile group to both the R- and S-pockets. For racemases operating on substrates bearing three polar groups (glutamate, aspartate, and serine racemases) or with compact, hydrophobic binding pockets (proline racemase), substituent motion is limited and the design strategy furnishes inhibitors with poor or modest binding affinities. The approach is most successful when substrates have a large, motile hydrophobic group that binds at a plastic and/or capacious hydrophobic site. Potent inhibitors were developed for mandelate racemase, isoleucine epimerase, and α-methylacyl-CoA racemase using the SPA inhibitor design strategy, exhibiting binding affinities ranging from substrate-like to exceeding that of the substrate by 100-fold. This rational approach for designing inhibitors of racemases and epimerases having the appropriate active-site architectures is a useful strategy for furnishing compounds for drug development.
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Affiliation(s)
- Stephen L Bearne
- Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, NS, Canada; Department of Chemistry, Dalhousie University, Halifax, NS, Canada.
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5
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Zheng T, Jing M, Gong T, Yan J, Wang X, Xu M, Zhou X, Zeng J, Li Y. Regulatory mechanisms of exopolysaccharide synthesis and biofilm formation in Streptococcus mutans. J Oral Microbiol 2023; 15:2225257. [PMID: 37346997 PMCID: PMC10281425 DOI: 10.1080/20002297.2023.2225257] [Citation(s) in RCA: 19] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2022] [Revised: 06/07/2023] [Accepted: 06/08/2023] [Indexed: 06/23/2023] Open
Abstract
Background Dental caries is a chronic, multifactorial and biofilm-mediated oral bacterial infection affecting almost every age group and every geographical region. Streptococcus mutans is considered an important pathogen responsible for the initiation and development of dental caries. It produces exopolysaccharides in situ to promote the colonization of cariogenic bacteria and coordinate dental biofilm development. Objective The understanding of the regulatory mechanism of S. mutans biofilm formation can provide a theoretical basis for the prevention and treatment of caries. Design At present, an increasing number of studies have identified many regulatory systems in S. mutans that regulate biofilm formation, including second messengers (e.g. c-di-AMP, Ap4A), transcription factors (e.g. EpsR, RcrR, StsR, AhrC, FruR), two-component systems (e.g. CovR, VicR), small RNA (including sRNA0426, srn92532, and srn133489), acetylation modifications (e.g. ActG), CRISPR-associated proteins (e.g. Cas3), PTS systems (e.g. EIIAB), quorum-sensing signaling system (e.g. LuxS), enzymes (including Dex, YidC, CopZ, EzrA, lmrB, SprV, RecA, PdxR, MurI) and small-molecule metabolites. Results This review summarizes the recent progress in the molecular regulatory mechanisms of exopolysaccharides synthesis and biofilm formation in S. mutans.
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Affiliation(s)
- Ting Zheng
- State Key Laboratory of Oral Diseases, National Clinical Research Center for Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Meiling Jing
- State Key Laboratory of Oral Diseases, National Clinical Research Center for Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Tao Gong
- State Key Laboratory of Oral Diseases, National Clinical Research Center for Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Jiangchuan Yan
- State Key Laboratory of Oral Diseases, National Clinical Research Center for Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Xiaowan Wang
- State Key Laboratory of Oral Diseases, National Clinical Research Center for Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Mai Xu
- State Key Laboratory of Oral Diseases, National Clinical Research Center for Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Xuedong Zhou
- State Key Laboratory of Oral Diseases, National Clinical Research Center for Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China
- Department of Operative Dentistry and Endodontics, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Jumei Zeng
- West China School of Public Health and West China Fourth Hospital, Sichuan University, Chengdu, China
| | - Yuqing Li
- State Key Laboratory of Oral Diseases, National Clinical Research Center for Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China
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Folliero V, Dell’Annunziata F, Roscetto E, Amato A, Gasparro R, Zannella C, Casolaro V, De Filippis A, Catania MR, Franci G, Galdiero M. Rhein: A Novel Antibacterial Compound Against Streptococcus mutans Infection. Microbiol Res 2022; 261:127062. [DOI: 10.1016/j.micres.2022.127062] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2021] [Revised: 05/04/2022] [Accepted: 05/04/2022] [Indexed: 12/15/2022]
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7
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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] [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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Choi K, Son GJ, Ahmad S, Lee SY, Lee HJ, Lee SW. Contribution of the murI Gene Encoding Glutamate Racemase in the Motility and Virulence of Ralstonia solanacearum. THE PLANT PATHOLOGY JOURNAL 2020; 36:355-363. [PMID: 32788894 PMCID: PMC7403515 DOI: 10.5423/ppj.oa.03.2020.0049] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/04/2020] [Revised: 05/21/2020] [Accepted: 05/26/2020] [Indexed: 05/15/2023]
Abstract
Bacterial traits for virulence of Ralstonia solanacearum causing lethal wilt in plants were extensively studied but are not yet fully understood. Other than the known virulence factors of Ralstonia solanacearum, this study aimed to identify the novel gene(s) contributing to bacterial virulence of R. solanacearum. Among the transposon-inserted mutants that were previously generated, we selected mutant SL341F12 strain produced exopolysaccharide equivalent to wild type strain but showed reduced virulence compared to wild type. In this mutant, a transposon was found to disrupt the murI gene encoding glutamate racemase which converts L-glutamate to D-glutamate. SL341F12 lost its motility, and its virulence in the tomato plant was markedly diminished compared to that of the wild type. The altered phenotypes of SL341F12 were restored by introducing a full-length murI gene. The expression of genes required for flagella assembly was significantly reduced in SL341F12 compared to that of the wild type or complemented strain, indicating that the loss of bacterial motility in the mutant was due to reduced flagella assembly. A dramatic reduction of the mutant population compared to its wild type was apparent in planta (i.e., root) than its wild type but not in soil and rhizosphere. This may contribute to the impaired virulence in the mutant strain. Accordingly, we concluded that murI in R. solanacearum may be involved in controlling flagella assembly and consequently, the mutation affects bacterial motility and virulence.
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Affiliation(s)
- Kihyuck Choi
- Department of Applied Bioscience, Dong-A University, Busan 49315, Korea
| | - Geun Ju Son
- Department of Applied Bioscience, Dong-A University, Busan 49315, Korea
| | - Shabir Ahmad
- Department of Microbiology and Biotechnology, Sarhad University of Science and Information Technology, Peshawar, Pakistan
| | - Seung Yeup Lee
- Department of Applied Bioscience, Dong-A University, Busan 49315, Korea
| | - Hyoung Ju Lee
- Department of Applied Bioscience, Dong-A University, Busan 49315, Korea
| | - Seon-Woo Lee
- Department of Applied Bioscience, Dong-A University, Busan 49315, Korea
- Corresponding author. Phone) +82-51-200-7551, FAX) +82-51-200-7505, E-mail)
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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] [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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10
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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: 0.4] [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.
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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.
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11
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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: 0.3] [Reference Citation Analysis] [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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He Z, Huang Z, Jiang W, Zhou W. Antimicrobial Activity of Cinnamaldehyde on Streptococcus mutans Biofilms. Front Microbiol 2019; 10:2241. [PMID: 31608045 PMCID: PMC6773874 DOI: 10.3389/fmicb.2019.02241] [Citation(s) in RCA: 89] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2019] [Accepted: 09/12/2019] [Indexed: 12/18/2022] Open
Abstract
Streptococcus mutans is considered the most relevant bacteria in the transition of non-pathogenic commensal oral microbiota to biofilms which contribute to the dental caries process. The present study aimed to evaluate the antimicrobial activity of a natural plant product, cinnamaldehyde against S. mutans biofilms. Minimum inhibitory concentrations (MIC), minimal bactericidal concentration (MBC), and growth curves were determined to assess its antimicrobial effect against planktonic S. mutans. The biofilm biomass and metabolism with different concentrations of cinnamaldehyde and different incubation time points were assessed using the crystal violet and MTT assays. The biofilms were visualized using confocal laser scanning microscopy (CLSM). Bacterial cell surface hydrophobicity, aggregation, acid production, and acid tolerance were evaluated after cinnamaldehyde treatment. The gene expression of virulence-related factors (gtfB, gtfC, gtfD, gbpB, comDE, vicR, ciaH, ldh and relA) was investigated by real-time PCR. The MIC and MBC of cinnamaldehyde against planktonic S. mutans were 1000 and 2000 μg/mL, respectively. The results showed that cinnamaldehyde can decrease biofilm biomass and metabolism at sub-MIC concentrations. CLSM images revealed that the biofilm-covered surface areas decreased with increasing concentrations of cinnamaldehyde. Cinnamaldehyde increased cell surface hydrophobicity, reduced S. mutans aggregation, inhibited acid production, and acid tolerance. Genes expressions in the biofilms were down-regulated in the presence of cinnamaldehyde. Therefore, our data demonstrated that cinnamaldehyde at sub-MIC level suppressed the microbial activity on S. mutans biofilm by modulating hydrophobicity, aggregation, acid production, acid tolerance, and virulence gene expression.
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Affiliation(s)
- Zhiyan He
- Laboratory of Oral Microbiota and Systemic Diseases, Shanghai Key Laboratory of Stomatology and Shanghai Research Institute of Stomatology, Shanghai Ninth People's Hospital, College of Stomatology, Shanghai Jiao Tong University School of Medicine, Shanghai, China.,National Clinical Research Center for Oral Diseases, Shanghai Key Laboratory of Stomatology and Shanghai Research Institute of Stomatology, Shanghai, China
| | - Zhengwei Huang
- National Clinical Research Center for Oral Diseases, Shanghai Key Laboratory of Stomatology and Shanghai Research Institute of Stomatology, Shanghai, China.,Department of Endodontics, Shanghai Ninth People's Hospital, College of Stomatology, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Wei Jiang
- National Clinical Research Center for Oral Diseases, Shanghai Key Laboratory of Stomatology and Shanghai Research Institute of Stomatology, Shanghai, China.,Department of Endodontics, Shanghai Ninth People's Hospital, College of Stomatology, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Wei Zhou
- Laboratory of Oral Microbiota and Systemic Diseases, Shanghai Key Laboratory of Stomatology and Shanghai Research Institute of Stomatology, Shanghai Ninth People's Hospital, College of Stomatology, Shanghai Jiao Tong University School of Medicine, Shanghai, China.,National Clinical Research Center for Oral Diseases, Shanghai Key Laboratory of Stomatology and Shanghai Research Institute of Stomatology, Shanghai, China
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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: 0.1] [Reference Citation Analysis] [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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Ribeiro M, Malheiro J, Grenho L, Fernandes MH, Simões M. Cytotoxicity and antimicrobial action of selected phytochemicals against planktonic and sessile Streptococcus mutans. PeerJ 2018; 6:e4872. [PMID: 29888127 PMCID: PMC5991298 DOI: 10.7717/peerj.4872] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2018] [Accepted: 05/10/2018] [Indexed: 12/17/2022] Open
Abstract
Background Dental caries remains the most prevalent and costly oral infectious disease worldwide, encouraging the search for new and more effective antimicrobials. Therefore, the aim of this work was to study the antimicrobial action of selected phytochemicals (eugenol, citronellol, sabinene hydrate, trans-cinnamaldehyde, terpineol and cinnamic acid) against Streptococcus mutans in planktonic and biofilm states as well as the cytotoxicity of these compounds. Methods The antibacterial activity of the selected compounds was evaluated by the determination of the minimal bactericidal concentration. The resazurin assay was used to assess the metabolic activity of sessile S. mutans. The cytotoxicity was determined using a fibroblast cell line. Results Among the tested phytochemicals, citronellol, cinnamic acid and trans-cinnamaldehyde were the most effective against both planktonic and sessile S. mutans, an effect apparently related to their hydrophobic character. Additionally, these three compounds did not compromise fibroblasts cell viability. Discussion Citronellol, cinnamic acid and trans-cinnamaldehyde demonstrated significant antimicrobial activity and low cytotoxicity proposing their potential as a novel group of therapeutic compounds to control oral infectious diseases. Moreover, their effects are particularly relevant when benchmarked against eugenol, a phytochemical commonly used for prosthodontic applications in dentistry.
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Affiliation(s)
- Marta Ribeiro
- LEPABE-Department of Chemical Engineering, Faculty of Engineering-University of Porto, Porto, Portugal
| | - Joana Malheiro
- LEPABE-Department of Chemical Engineering, Faculty of Engineering-University of Porto, Porto, Portugal
| | - Liliana Grenho
- Laboratory for Bone Metabolism and Regeneration, Faculty of Dental Medicine, University of Porto, Porto, Portugal
| | - Maria Helena Fernandes
- Laboratory for Bone Metabolism and Regeneration, Faculty of Dental Medicine, University of Porto, Porto, Portugal.,REQUIMTE/LAQV, University of Porto, Porto, Portugal
| | - Manuel Simões
- LEPABE-Department of Chemical Engineering, Faculty of Engineering-University of Porto, Porto, Portugal
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