1
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Van Wieren A, Durrant JD, Majumdar S. Computational and experimental analyses of alanine racemase suggest new avenues for developing allosteric small-molecule antibiotics. Drug Dev Res 2023; 84:999-1007. [PMID: 37129190 PMCID: PMC10524904 DOI: 10.1002/ddr.22068] [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: 12/13/2022] [Revised: 02/23/2023] [Accepted: 04/10/2023] [Indexed: 05/03/2023]
Abstract
Given the ever-present threat of antibacterial resistance, there is an urgent need to identify new antibacterial drugs and targets. One such target is alanine racemase (Alr), an enzyme required for bacterial cell-wall biosynthesis. Alr is an attractive drug target because it is essential for bacterial survival but is absent in humans. Existing drugs targeting Alr lack specificity and have severe side effects. We here investigate alternative mechanisms of Alr inhibition. Alr functions exclusively as an obligate homodimer, so we probed seven conserved interactions on the dimer interface, distant from the enzymatic active site, to identify possible allosteric influences on activity. Using the Alr from Mycobacterium tuberculosis (MT) as a model, we found that the Lys261/Asp135 salt bridge is critical for catalytic activity. The Lys261Ala mutation completely inactivated the enzyme, and the Asp135Ala mutation reduced catalytic activity eight-fold. Further investigation suggested a potential drug-binding site near the Lys261/Asp135 salt bridge that may be useful for allosteric drug discovery.
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Affiliation(s)
- Arie Van Wieren
- Madia Department of Chemistry, Biochemistry, Physics and Engineering, Indiana University of Pennsylvania, Indiana, PA 15705
- Current address: The Johns Hopkins University School of Medicine, Baltimore, MD 21205
| | - Jacob D Durrant
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260
| | - Sudipta Majumdar
- Madia Department of Chemistry, Biochemistry, Physics and Engineering, Indiana University of Pennsylvania, Indiana, PA 15705
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2
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Bakunova AK, Matyuta IO, Nikolaeva AY, Boyko KM, Popov VO, Bezsudnova EY. Mechanism of D-Cycloserine Inhibition of D-Amino Acid Transaminase from Haliscomenobacter hydrossis. BIOCHEMISTRY. BIOKHIMIIA 2023; 88:687-697. [PMID: 37331714 DOI: 10.1134/s0006297923050115] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/26/2022] [Revised: 02/10/2023] [Accepted: 02/11/2023] [Indexed: 06/20/2023]
Abstract
D-cycloserine inhibits pyridoxal-5'-phosphate (PLP)-dependent enzymes. Inhibition effect depend on organization of the active site and mechanism of the catalyzed reaction. D-cycloserine interacts with the PLP form of the enzyme similarly to the substrate (amino acid), and this interaction is predominantly reversible. Several products of the interaction of PLP with D-cycloserine are known. For some enzymes formation of a stable aromatic product - hydroxyisoxazole-pyridoxamine-5'-phosphate at certain pH - leads to irreversible inhibition. The aim of this work was to study the mechanism of D-cycloserine inhibition of the PLP-dependent D-amino acid transaminase from Haliscomenobacter hydrossis. Spectral methods revealed several products of interaction of D-cycloserine with PLP in the active site of transaminase: oxime between PLP and β-aminooxy-D-alanine, ketimine between pyridoxamine-5'-phosphate and cyclic form of D-cycloserine, and pyridoxamine-5'-phosphate. Formation of hydroxyisoxazole-pyridoxamine-5'-phosphate was not observed. 3D structure of the complex with D-cycloserine was obtained using X-ray diffraction analysis. In the active site of transaminase, a ketimine adduct between pyridoxamine-5'-phosphate and D-cycloserine in the cyclic form was found. Ketimine occupied two positions interacting with different active site residues via hydrogen bonds. Using kinetic and spectral methods we have shown that D-cycloserine inhibition is reversible, and activity of the inhibited transaminase from H. hydrossis could be restored by adding excess of keto substrate or excess of cofactor. The obtained results confirm reversibility of the inhibition by D-cycloserine and interconversion of various adducts of D-cycloserine and PLP.
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Affiliation(s)
- Alina K Bakunova
- Bach Institute of Biochemistry, Research Centre of Biotechnology, Russian Academy of Sciences, Moscow, 119071, Russia.
| | - Ilya O Matyuta
- Bach Institute of Biochemistry, Research Centre of Biotechnology, Russian Academy of Sciences, Moscow, 119071, Russia
| | - Alena Yu Nikolaeva
- Bach Institute of Biochemistry, Research Centre of Biotechnology, Russian Academy of Sciences, Moscow, 119071, Russia
- Kurchatov Complex of NBICS-Technologies, National Research Centre "Kurchatov Institute", Moscow, 123182, Russia
| | - Konstantin M Boyko
- Bach Institute of Biochemistry, Research Centre of Biotechnology, Russian Academy of Sciences, Moscow, 119071, Russia
| | - Vladimir O Popov
- Bach Institute of Biochemistry, Research Centre of Biotechnology, Russian Academy of Sciences, Moscow, 119071, Russia
- Faculty of Biology, Lomonosov Moscow State University, Moscow, 119991, Russia
| | - Ekaterina Yu Bezsudnova
- Bach Institute of Biochemistry, Research Centre of Biotechnology, Russian Academy of Sciences, Moscow, 119071, Russia.
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Synthesis, antimicrobial activity and molecular docking studies of spiroquinoline-indoline-dione and spiropyrazolo-indoline-dione derivatives. Sci Rep 2023; 13:1676. [PMID: 36717728 PMCID: PMC9885930 DOI: 10.1038/s41598-023-27777-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2022] [Accepted: 01/09/2023] [Indexed: 01/31/2023] Open
Abstract
Spiro[benzo[h]quinoline-7,3'-indoline]diones and spiro[indoline-3,4'-pyrazolo[3,4-b]quinoline]diones were efficiently synthesized via one-pot multi-component reactions under ultrasound-promoted conditions. Spiro[benzo[h]quinoline-7,3'-indoline]dione derivatives were successfully developed by the reaction of isatins, naphthalene-1-amine and 1,3-dicarbonyl compounds. The spiro[indoline-3,4'-pyrazolo[3,4-b]quinoline]dione derivatives were prepared by the reaction of isatins, 5-amino-1-methyl-3-pheylpyrazole, and 1,3-dicarbonyl compounds by using ( ±)-camphor-10-sulfonic acid as a catalyst in H2O/EtOH (3:1 v/v) solvent mixture. The antibacterial activity of the synthesized compounds was evaluated against, Enterococcus faecalis, Staphylococcus aureus and Candida albicans. Compounds 4b, 4h, and 6h showed the strongest antimicrobial activity toward both bacteria. The MIC values of these compounds ranged from 375-3000 µg/mL. The effect of these compounds (4b, 4h, 6h) as a function of applied dose and time was investigated by a kinetic study, and the interaction with these antimicrobial results was simulated by a molecular docking study. We also used the docking approach with Covid-19 since secondary bacterial infections. Docking showed that indoline-quinoline hybrid compounds 4b and 4h exerted the strongest docking binding value against the active sites of 6LU7. In addition, the synthesized compounds had a moderate to good free radical scavenging activity.
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Jiang Q, He X, Shui Y, Lyu X, Wang L, Xu L, Chen Z, Zou L, Zhou X, Cheng L, Li M. d-Alanine metabolic pathway, a potential target for antibacterial drug designing in Enterococcus faecalis. Microb Pathog 2021; 158:105078. [PMID: 34245823 DOI: 10.1016/j.micpath.2021.105078] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2021] [Accepted: 07/01/2021] [Indexed: 11/15/2022]
Abstract
Enterococcus faecalis (E. faecalis) is associated with persistent root canal infection because of its biofilm and various virulence factors. However, E. faecalis exhibits extensive drug resistance. d-Alanine (D-Ala) metabolism is essential for bacterial peptidoglycan biosynthesis. d-cycloserine (DCS), a second line drug used in the treatment of Mycobacterium tuberculosis infection, can inhibit two key enzymes in D-Ala metabolism: alanine racemase and d-alanine-d-alanine ligase. The aim of this study was to evaluate the effect of D-Ala metabolism on E. faecalis growth, cell wall integrity, biofilm formation and virulence gene expression by additional DCS with or without D-Ala. The results showed that DCS inhibited the planktonic growth and biofilm formation of E. faecalis in a dose-dependent manner. Both the minimum inhibitory concentration (MIC) and minimum biofilm inhibition concentration (MBIC) of DCS against E. faecalis were 200 μg/ml, whereas 50 μg/ml of DCS could inhibit planktonic growth and biofilm formation effectively. The addition of DCS also resulted in bacterial cell wall damage, biofilm surface roughness increase and biofilm adhesion force reduction. Moreover, the treatment of DCS downregulated the expression of asa1, esp, efaA, gelE, sprE, fsrB and ace genes. However, all of these inhibitory effects of DCS could be rescued by the addition of exogenous D-Ala. Meanwhile, DCS exhibited no toxicity to HGEs and HOKs. Therefore, D-Ala metabolic pathway in E. faecalis is a potential target for drug designing.
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Affiliation(s)
- Qingsong Jiang
- State Key Laboratory of Oral Diseases, National Clinical Research Center for Oral Diseases, West China School of Stomatology, Sichuan University, Chengdu, Sichuan, 610041, China
| | - Xiaoya He
- State Key Laboratory of Oral Diseases, National Clinical Research Center for Oral Diseases, West China School of Stomatology, Sichuan University, Chengdu, Sichuan, 610041, China
| | - Yusen Shui
- State Key Laboratory of Oral Diseases, National Clinical Research Center for Oral Diseases, West China School of Stomatology, Sichuan University, Chengdu, Sichuan, 610041, China
| | - Xiaoying Lyu
- State Key Laboratory of Oral Diseases, National Clinical Research Center for Oral Diseases, West China School of Stomatology, Sichuan University, Chengdu, Sichuan, 610041, China
| | - Liang Wang
- State Key Laboratory of Oral Diseases, National Clinical Research Center for Oral Diseases, West China School of Stomatology, Sichuan University, Chengdu, Sichuan, 610041, China
| | - Laijun Xu
- State Key Laboratory of Oral Diseases, National Clinical Research Center for Oral Diseases, West China School of Stomatology, Sichuan University, Chengdu, Sichuan, 610041, China
| | - Zhu Chen
- Department of Conservative Dentistry and Endodontics, Guiyang Hospital of Stomatology, Guiyang, China
| | - Ling Zou
- State Key Laboratory of Oral Diseases, National Clinical Research Center for Oral Diseases, West China School of Stomatology, Sichuan University, Chengdu, Sichuan, 610041, China
| | - Xuedong Zhou
- State Key Laboratory of Oral Diseases, National Clinical Research Center for Oral Diseases, West China School of Stomatology, Sichuan University, Chengdu, Sichuan, 610041, China
| | - Lei Cheng
- State Key Laboratory of Oral Diseases, National Clinical Research Center for Oral Diseases, West China School of Stomatology, Sichuan University, Chengdu, Sichuan, 610041, China
| | - Mingyun Li
- State Key Laboratory of Oral Diseases, National Clinical Research Center for Oral Diseases, West China School of Stomatology, Sichuan University, Chengdu, Sichuan, 610041, China.
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D-Cycloserine destruction by alanine racemase and the limit of irreversible inhibition. Nat Chem Biol 2020; 16:686-694. [PMID: 32203411 PMCID: PMC7246083 DOI: 10.1038/s41589-020-0498-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2019] [Accepted: 02/06/2020] [Indexed: 11/08/2022]
Abstract
The broad-spectrum antibiotic D-cycloserine (DCS) is a key component of regimens used to treat multi- and extensively drug-resistant tuberculosis. DCS, a structural analog of D-alanine, binds to and inactivates two essential enzymes involved in peptidoglycan biosynthesis, alanine racemase (Alr) and D-Ala:D-Ala ligase. Inactivation of Alr is thought to proceed via a mechanism-based irreversible route, forming an adduct with the pyridoxal 5'-phosphate cofactor, leading to bacterial death. Inconsistent with this hypothesis, Mycobacterium tuberculosis Alr activity can be detected after exposure to clinically relevant DCS concentrations. To address this paradox, we investigated the chemical mechanism of Alr inhibition by DCS. Inhibition of M. tuberculosis Alr and other Alrs is reversible, mechanistically revealed by a previously unidentified DCS-adduct hydrolysis. Dissociation and subsequent rearrangement to a stable substituted oxime explains Alr reactivation in the cellular milieu. This knowledge provides a novel route for discovery of improved Alr inhibitors against M. tuberculosis and other bacteria.
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Dehbashi S, Tahmasebi H, Sedighi P, Davarian F, Arabestani MR. Development of high-resolution melting curve analysis in rapid detection of vanA gene, Enterococcus faecalis, and Enterococcus faecium from clinical isolates. Trop Med Health 2020; 48:8. [PMID: 32099522 PMCID: PMC7027104 DOI: 10.1186/s41182-020-00197-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2019] [Accepted: 02/10/2020] [Indexed: 12/18/2022] Open
Abstract
Background High-resolution melting analysis (HRMA) is a novel molecular technique based on the real-time PCR that can be used to detect vancomycin resistance Enterococcus (VRE). The purpose of this study was to identify VRE species with HRMA in clinical isolates. Results Out of 49 Enterococcus isolates, 11 (22.44%) E. faecium isolates and 19 (38.77%) E. faecalis isolates were detected. Average melting temperatures for divIVA in E.faecalis, alanine racemase in E.faecium, and vanA in VRE strains were obtained as 79.9 ± 0.5 °C, 85.4 ± 0.5 °C, and 82.99 ± 0.5 °C, respectively. Furthermore, the data showed that the HRMA method was sensitive to detect 100 CFU/ml for the divIVA, alanine racemase, and vanA genes. Also, out of 49 Enterococcus spp., which were isolated by HRMA assay, 8 isolates (16.32%) of E. faecium and 18 isolates (36.73%) of E. faecalis were detected. The vanA gene was reported in 2 isolates (25%) of E. faecium and 9 isolates (50%) of E. faecalis. Conclusions This study demonstrated that using the HRMA method, we can detect E. faecium, E. faecalis, and the vanA gene with high sensitivity and specificity.
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Affiliation(s)
- Sanaz Dehbashi
- 1Department of Microbiology, School of Medicine, Hamadan University of Medical Sciences, Pajoohesh junction, Hamadan, Iran
| | - Hamed Tahmasebi
- 2Department of Microbiology, School of Medicine, Zahedan University of Medical Sciences, Zahedan, Iran
| | | | - Faeze Davarian
- 4School of Paramedical, Hamadan University of Medical Sciences, Hamadan, Iran
| | - Mohammad Reza Arabestani
- 1Department of Microbiology, School of Medicine, Hamadan University of Medical Sciences, Pajoohesh junction, Hamadan, Iran.,5Nutritious Research Center, School of Medicine, Hamadan University of Medical Sciences, Hamadan, Iran
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7
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Biochemical characterization and mutational analysis of alanine racemase from Clostridium perfringens. J Biosci Bioeng 2019; 128:149-155. [DOI: 10.1016/j.jbiosc.2019.02.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2018] [Revised: 02/03/2019] [Accepted: 02/06/2019] [Indexed: 11/24/2022]
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8
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Singh H, Das S, Yadav J, Srivastava VK, Jyoti A, Kaushik S. In search of novel protein drug targets for treatment of Enterococcus faecalis infections. Chem Biol Drug Des 2019; 94:1721-1739. [PMID: 31260188 DOI: 10.1111/cbdd.13582] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2019] [Revised: 06/08/2019] [Accepted: 06/17/2019] [Indexed: 12/27/2022]
Abstract
Enterococcus faecalis (Ef) is one of the major pathogens involved in hospital-acquired infections. It can cause nosocomial bacteremia, surgical wound infection, and urinary tract infection. It is important to mention here that Ef is developing resistance against many commonly occurring antibiotics. The occurrence of multidrug resistance (MDR) and extensive-drug resistance (XDR) is now posing a major challenge to the medical community. In this regard, to combat the infections caused by Ef, we have to look for an alternative. Rational structure-based drug design exploits the three-dimensional structure of the target protein, which can be unraveled by various techniques such as X-ray crystallography or nuclear magnetic resonance (NMR) spectroscopy. In this review, we have discussed the complete picture of Ef infections, the possible treatment available at present, and the alternative treatment options to be explored. This study will help in better understanding of novel biological targets against Ef and the compounds, which are likely to bind with these targets. Using these detailed structural informations, rational structure-based drug design is achievable and tight inhibitors against Ef can be prepared.
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Affiliation(s)
- Harpreet Singh
- Amity Institute of Biotechnology, Amity University Rajasthan, Jaipur, India
| | - Satyajeet Das
- Amity Institute of Biotechnology, Amity University Rajasthan, Jaipur, India
| | - Jyoti Yadav
- Amity Institute of Biotechnology, Amity University Rajasthan, Jaipur, India
| | | | - Anupam Jyoti
- Amity Institute of Biotechnology, Amity University Rajasthan, Jaipur, India
| | - Sanket Kaushik
- Amity Institute of Biotechnology, Amity University Rajasthan, Jaipur, India
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Dong H, Han Q, Guo Y, Ju J, Wang S, Yuan C, Long W, He X, Xu S, Li S. Enzymatic characterization and crystal structure of biosynthetic alanine racemase from Pseudomonas aeruginosa PAO1. Biochem Biophys Res Commun 2018; 503:2319-2325. [PMID: 29964014 DOI: 10.1016/j.bbrc.2018.06.155] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2018] [Accepted: 06/27/2018] [Indexed: 02/02/2023]
Abstract
Alanine racemase is a pyridoxal-5'-phosphate (PLP)-dependent enzyme that reversibly catalyzes the conversion of l-alanine to d-alanine. d-alanine is an essential constituent in many prokaryotic cell structures. Inhibition of alanine racemase is lethal to prokaryotes, creating an attractive target for designing antibacterial drugs. Here we report the crystal structure of biosynthetic alanine racemase (Alr) from a pathogenic bacteria Pseudomonas aeruginosa PAO1. Structural studies showed that P. aeruginosa Alr (PaAlr) adopts a conserved homodimer structure. A guest substrate d-lysine was observed in the active site and refined to dual-conformation. Two buffer ions, malonate and acetate, were bound in the proximity to d-lysine. Biochemical characterization revealed the optimal reaction conditions for PaAlr.
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Affiliation(s)
- Hui Dong
- Key Laboratory of Tianjin Radiation and Molecular Nuclear Medicine, Institute of Radiation Medicine, Chinese Academy of Medical Sciences & Peking Union Medical College, Tianjin, 300192, China
| | - Qingqing Han
- College of Life Science, Hebei Normal University, Shijiazhuang, 050024, China
| | - Yu Guo
- Shanghai Institute for Advanced Immunochemical Studies, ShanghaiTech University, Shanghai, 201210, China; University of Chinese Academy of Sciences, Beijing, 100049, China; School of Life Science and Technology, ShanghaiTech University, Shanghai, 201210, China
| | - Jiansong Ju
- College of Life Science, Hebei Normal University, Shijiazhuang, 050024, China
| | - Shanshan Wang
- Shanghai Institute for Advanced Immunochemical Studies, ShanghaiTech University, Shanghai, 201210, China
| | - Chao Yuan
- Shanghai Institute for Advanced Immunochemical Studies, ShanghaiTech University, Shanghai, 201210, China; University of Chinese Academy of Sciences, Beijing, 100049, China; School of Life Science and Technology, ShanghaiTech University, Shanghai, 201210, China
| | - Wei Long
- Key Laboratory of Tianjin Radiation and Molecular Nuclear Medicine, Institute of Radiation Medicine, Chinese Academy of Medical Sciences & Peking Union Medical College, Tianjin, 300192, China
| | - Xin He
- Key Laboratory of Tianjin Radiation and Molecular Nuclear Medicine, Institute of Radiation Medicine, Chinese Academy of Medical Sciences & Peking Union Medical College, Tianjin, 300192, China
| | - Shujing Xu
- College of Life Science, Hebei Normal University, Shijiazhuang, 050024, China.
| | - Sheng Li
- Shanghai Institute for Advanced Immunochemical Studies, ShanghaiTech University, Shanghai, 201210, China.
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10
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Structural features and kinetic characterization of alanine racemase from Bacillus pseudofirmus OF4. Biochem Biophys Res Commun 2018; 497:139-145. [DOI: 10.1016/j.bbrc.2018.02.041] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2018] [Accepted: 02/05/2018] [Indexed: 02/02/2023]
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11
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Azam MA, Jayaram U. Induced fit docking, free energy calculation and molecular dynamics studies on Mycobacterium tuberculosis alanine racemase inhibitor. MOLECULAR SIMULATION 2017. [DOI: 10.1080/08927022.2017.1393811] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Affiliation(s)
- Mohammed Afzal Azam
- Department of Pharmaceutical Chemistry, JSS College of Pharmacy (A Constituent College of Jagadguru Sri Shivarathreeswara University, Mysuru) Udhagamandalam, India
| | - Unni Jayaram
- Department of Pharmaceutical Chemistry, JSS College of Pharmacy (A Constituent College of Jagadguru Sri Shivarathreeswara University, Mysuru) Udhagamandalam, India
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Abstract
Vancomycin resistance in Gram-positive bacteria results from the replacement of the d-alanyl–d-alanine target of peptidoglycan precursors with d-alanyl–d-lactate or d-alanyl–d-serine (d-Ala-d-Ser), to which vancomycin has low binding affinity. VanT is one of the proteins required for the production of d-Ala-d-Ser-terminating precursors by converting l-Ser to d-Ser. VanT is composed of two domains, an N-terminal membrane-bound domain, likely involved in l-Ser uptake, and a C-terminal cytoplasmic catalytic domain which is related to bacterial alanine racemases. To gain insight into the molecular function of VanT, the crystal structure of the catalytic domain of VanTG from VanG-type resistant Enterococcus faecalis BM4518 was determined. The structure showed significant similarity to type III pyridoxal 5′-phosphate (PLP)-dependent alanine racemases, which are essential for peptidoglycan synthesis. Comparative structural analysis between VanTG and alanine racemases as well as site-directed mutagenesis identified three specific active site positions centered around Asn696 which are responsible for the l-amino acid specificity. This analysis also suggested that VanT racemases evolved from regular alanine racemases by acquiring additional selectivity toward serine while preserving that for alanine. The 4-fold-lower relative catalytic efficiency of VanTG against l-Ser versus l-Ala implied that this enzyme relies on its membrane-bound domain for l-Ser transport to increase the overall rate of d-Ser production. These findings illustrate how vancomycin pressure selected for molecular adaptation of a housekeeping enzyme to a bifunctional enzyme to allow for peptidoglycan remodeling, a strategy increasingly observed in antibiotic-resistant bacteria. Vancomycin is one of the drugs of last resort against Gram-positive antibiotic-resistant pathogens. However, bacteria have evolved a sophisticated mechanism which remodels the drug target, the d-alanine ending precursors in cell wall synthesis, into precursors terminating with d-lactate or d-serine, to which vancomycin has less affinity. d-Ser is synthesized by VanT serine racemase, which has two unusual characteristics: (i) it is one of the few serine racemases identified in bacteria and (ii) it contains a membrane-bound domain involved in l-Ser uptake. The structure of the catalytic domain of VanTG showed high similarity to alanine racemases, and we identified three specific active site substitutions responsible for l-Ser specificity. The data provide the molecular basis for VanT evolution to a bifunctional enzyme coordinating both transport and racemization. Our findings also illustrate the evolution of the essential alanine racemase into a vancomycin resistance enzyme in response to antibiotic pressure.
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13
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Sun X, He G, Wang X, Xu S, Ju J, Xu X. Crystal Structure of a Thermostable Alanine Racemase from Thermoanaerobacter tengcongensis MB4 Reveals the Role of Gln360 in Substrate Selection. PLoS One 2015. [PMID: 26218070 PMCID: PMC4517790 DOI: 10.1371/journal.pone.0133516] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Pyridoxal 5’-phosphate (PLP) dependent alanine racemase catalyzes racemization of L-Ala to D-Ala, a key component of the peptidoglycan network in bacterial cell wall. It has been extensively studied as an important antimicrobial drug target due to its restriction in eukaryotes. However, many marketed alanine racemase inhibitors also act on eukaryotic PLP-dependent enzymes and cause side effects. A thermostable alanine racemase (AlrTt) from Thermoanaerobacter tengcongensis MB4 contains an evolutionarily non-conserved residue Gln360 in inner layer of the substrate entryway, which is supposed to be a key determinant in substrate specificity. Here we determined the crystal structure of AlrTt in complex with L-Ala at 2.7 Å resolution, and investigated the role of Gln360 by saturation mutagenesis and kinetic analysis. Compared to typical bacterial alanine racemase, presence of Gln360 and conformational changes of active site residues disrupted the hydrogen bonding interactions necessary for proper PLP immobilization, and decreased both the substrate affinity and turnover number of AlrTt. However, it could be complemented by introduction of hydrophobic amino acids at Gln360, through steric blocking and interactions with a hydrophobic patch near active site pocket. These observations explained the low racemase activity of AlrTt, revealed the essential role of Gln360 in substrate selection, and its preference for hydrophobic amino acids especially Tyr in bacterial alanine racemization. Our work will contribute new insights into the alanine racemization mechanism for antimicrobial drug development.
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Affiliation(s)
- Xiaoliang Sun
- Institute of Ageing Research, School of Medicine, Hangzhou Normal University, Hangzhou, China
| | - Guangzheng He
- College of Life Science, Hebei Normal University, Shijiazhuang, China
| | - Xiaoyan Wang
- Institute of Ageing Research, School of Medicine, Hangzhou Normal University, Hangzhou, China
| | - Shujing Xu
- College of Life Science, Hebei Normal University, Shijiazhuang, China
| | - Jiansong Ju
- College of Life Science, Hebei Normal University, Shijiazhuang, China
- * E-mail: (JSJ); (XLX)
| | - Xiaoling Xu
- Institute of Ageing Research, School of Medicine, Hangzhou Normal University, Hangzhou, China
- * E-mail: (JSJ); (XLX)
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14
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Affiliation(s)
- Mohammed Afzal Azam
- Department of Pharmaceutical Chemistry, JSS College of Pharmacy, Udhagamandalam, Tamil Nadu, India
| | - Unni Jayaram
- Department of Pharmaceutical Chemistry, JSS College of Pharmacy, Udhagamandalam, Tamil Nadu, India
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15
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Liu D, Liu X, Zhang L, Jiao H, Ju J, Zhao B. Biochemical characteristics of an alanine racemase from Aeromonas hydrophil HBNUAh01. Microbiology (Reading) 2015. [DOI: 10.1134/s0026261715020071] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
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16
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Frank KL, Colomer-Winter C, Grindle SM, Lemos JA, Schlievert PM, Dunny GM. Transcriptome analysis of Enterococcus faecalis during mammalian infection shows cells undergo adaptation and exist in a stringent response state. PLoS One 2014; 9:e115839. [PMID: 25545155 PMCID: PMC4278851 DOI: 10.1371/journal.pone.0115839] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2014] [Accepted: 12/01/2014] [Indexed: 11/30/2022] Open
Abstract
As both a commensal and a major cause of healthcare-associated infections in humans, Enterococcus faecalis is a remarkably adaptable organism. We investigated how E. faecalis adapts in a mammalian host as a pathogen by characterizing changes in the transcriptome during infection in a rabbit model of subdermal abscess formation using transcriptional microarrays. The microarray experiments detected 222 and 291 differentially regulated genes in E. faecalis OG1RF at two and eight hours after subdermal chamber inoculation, respectively. The profile of significantly regulated genes at two hours post-inoculation included genes involved in stress response, metabolism, nutrient acquisition, and cell surface components, suggesting genome-wide adaptation to growth in an altered environment. At eight hours post-inoculation, 88% of the differentially expressed genes were down-regulated and matched a transcriptional profile consistent with a (p)ppGpp-mediated stringent response. Subsequent subdermal abscess infections with E. faecalis mutants lacking the (p)ppGpp synthetase/hydrolase RSH, the small synthetase RelQ, or both enzymes, suggest that intracellular (p)ppGpp levels, but not stringent response activation, influence persistence in the model. The ability of cells to synthesize (p)ppGpp was also found to be important for growth in human serum and whole blood. The data presented in this report provide the first genome-wide insights on E. faecalis in vivo gene expression and regulation measured by transcriptional profiling during infection in a mammalian host and show that (p)ppGpp levels affect viability of E. faecalis in multiple conditions relevant to mammalian infection. The subdermal abscess model can serve as a novel experimental system for studying the E. faecalis stringent response in the context of the mammalian immune system.
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Affiliation(s)
- Kristi L. Frank
- Department of Microbiology, University of Minnesota Medical School, Minneapolis, Minnesota, United States of America
| | - Cristina Colomer-Winter
- Center for Oral Biology and Department of Microbiology and Immunology, University of Rochester School of Medicine and Dentistry, Rochester, New York, United States of America
| | - Suzanne M. Grindle
- Department of Microbiology, University of Minnesota Medical School, Minneapolis, Minnesota, United States of America
| | - José A. Lemos
- Center for Oral Biology and Department of Microbiology and Immunology, University of Rochester School of Medicine and Dentistry, Rochester, New York, United States of America
| | - Patrick M. Schlievert
- Department of Microbiology, University of Minnesota Medical School, Minneapolis, Minnesota, United States of America
| | - Gary M. Dunny
- Department of Microbiology, University of Minnesota Medical School, Minneapolis, Minnesota, United States of America
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17
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Davis E, Scaletti-Hutchinson E, Opel-Reading H, Nakatani Y, Krause KL. The structure of alanine racemase from Acinetobacter baumannii. Acta Crystallogr F Struct Biol Commun 2014; 70:1199-205. [PMID: 25195891 PMCID: PMC4157418 DOI: 10.1107/s2053230x14017725] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2014] [Accepted: 08/01/2014] [Indexed: 01/11/2023] Open
Abstract
Acinetobacter baumannii is an opportunistic Gram-negative bacterium which is a common cause of hospital-acquired infections. Numerous antibiotic-resistant strains exist, emphasizing the need for the development of new antimicrobials. Alanine racemase (Alr) is a pyridoxal 5'-phosphate dependent enzyme that is responsible for racemization between enantiomers of alanine. As D-alanine is an essential component of the bacterial cell wall, its inhibition is lethal to prokaryotes, making it an excellent antibiotic drug target. The crystal structure of A. baumannii alanine racemase (AlrAba) from the highly antibiotic-resistant NCTC13302 strain has been solved to 1.9 Å resolution. Comparison of AlrAba with alanine racemases from closely related bacteria demonstrates a conserved overall fold. The substrate entryway and active site of the enzymes were shown to be highly conserved. The structure of AlrAba will provide the template required for future structure-based drug-design studies.
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Affiliation(s)
- Emily Davis
- Department of Biochemistry, University of Otago, Dunedin, New Zealand
| | | | | | - Yoshio Nakatani
- Department of Biochemistry, University of Otago, Dunedin, New Zealand
| | - Kurt L. Krause
- Department of Biochemistry, University of Otago, Dunedin, New Zealand
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18
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Dong H, Xu S, Lu X, He G, Zhao R, Chen S, Fu S, Ju J. Crystallization and preliminary X-ray study of a thermostable alanine racemase from Thermoanaerobacter tengcongensis MB4. Acta Crystallogr Sect F Struct Biol Cryst Commun 2013; 69:660-2. [PMID: 23722847 DOI: 10.1107/s1744309113011743] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2013] [Accepted: 04/29/2013] [Indexed: 11/10/2022]
Abstract
Alanine racemase (Alr(MB4)), a dimeric PLP-dependent thermostable enzyme from the anaerobic eubacterium Thermoanaerobacter tengcongensis MB4, was expressed and purified with a His(6) tag in a form suitable for X-ray crystallographic analysis. Crystals were grown by the hanging-drop vapour-diffusion method at 289 K using a solution consisting of 0.1 M bis-tris pH 7.0, 22%(w/v) polyethylene glycol 4000. X-ray diffraction data were collected to 2.6 Å resolution. The crystal belonged to the orthorhombic space group P2(1)2(1)2(1), with two protein molecules in an asymmetric unit.
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Affiliation(s)
- Hui Dong
- Tianjin International Joint Academy of Biotechnology and Medicine, Tianjin 300457, People's Republic of China
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19
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Prosser GA, de Carvalho LPS. Kinetic mechanism and inhibition of Mycobacterium tuberculosis D-alanine:D-alanine ligase by the antibiotic D-cycloserine. FEBS J 2013; 280:1150-66. [PMID: 23286234 DOI: 10.1111/febs.12108] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2012] [Revised: 12/17/2012] [Accepted: 12/19/2012] [Indexed: 11/30/2022]
Abstract
D-cycloserine (DCS) is an antibiotic that is currently used in second-line treatment of tuberculosis. DCS is a structural analogue of D-alanine, and targets two enzymes involved in the cytosolic stages of peptidoglycan synthesis: alanine racemase (Alr) and D-alanine:D-alanine ligase (Ddl). The mechanisms of inhibition of DCS have been well-assessed using Alr and Ddl enzymes from various bacterial species, but little is known regarding the interactions of DCS with the mycobacterial orthologues of these enzymes. We have over-expressed and purified recombinant Mycobacterium tuberculosis Ddl (MtDdl; Rv2981c), and report a kinetic examination of the enzyme with both its native substrate and DCS. MtDdl is activated by K(+), follows an ordered ter ter mechanism and displays distinct affinities for D-Ala at each D-Ala binding site (K(m,D-Ala1) = 0.075 mm, K(m,D-Ala2) = 3.6 mm). ATP is the first substrate to bind and is necessary for subsequent binding of D-alanine or DCS. The pH dependence of MtDdl kinetic parameters indicate that general base chemistry is involved in the catalytic step. DCS was found to competitively inhibit D-Ala binding at both MtDdl D-Ala sites with equal affinity (K(i,DCS1) = 14 μm, K(i,DCS2) = 25 μm); however, each enzyme active site can only accommodate a single DCS molecule at a given time. The pH dependence of K(i,DCS2) revealed a loss of DCS binding affinity at high pH (pK(a) = 7.5), suggesting that DCS binds optimally in the zwitterionic form. The results of this study may assist in the design and development of novel Ddl-specific inhibitors for use as anti-mycobacterial agents.
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Affiliation(s)
- Gareth A Prosser
- Mycobacterial Research Division, Medical Research Council National Institute for Medical Research, London, UK
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20
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Palani K, Burley SK, Swaminathan S. Structure of alanine racemase from Oenococcus oeni with bound pyridoxal 5'-phosphate. Acta Crystallogr Sect F Struct Biol Cryst Commun 2012; 69:15-9. [PMID: 23295479 DOI: 10.1107/s1744309112047276] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2012] [Accepted: 11/16/2012] [Indexed: 11/10/2022]
Abstract
The crystal structure of alanine racemase from Oenococcus oeni has been determined at 1.7 Å resolution using the single-wavelength anomalous dispersion (SAD) method and selenium-labelled protein. The protein exists as a symmetric dimer in the crystal, with both protomers contributing to the two active sites. Pyridoxal 5'-phosphate, a cofactor, is bound to each monomer and forms a Schiff base with Lys39. Structural comparison of alanine racemase from O. oeni (Alr) with homologous family members revealed similar domain organization and cofactor binding.
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Affiliation(s)
- Kandavelu Palani
- Biology Department, Brookhaven National Laboratory, Upton, NY 11973, USA
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21
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Scaletti ER, Luckner SR, Krause KL. Structural features and kinetic characterization of alanine racemase from Staphylococcus aureus (Mu50). ACTA CRYSTALLOGRAPHICA. SECTION D, BIOLOGICAL CRYSTALLOGRAPHY 2012; 68:82-92. [PMID: 22194336 PMCID: PMC3245724 DOI: 10.1107/s0907444911050682] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/10/2011] [Accepted: 11/25/2011] [Indexed: 11/10/2022]
Abstract
Staphylococcus aureus is an opportunistic Gram-positive bacterium which causes a wide variety of diseases ranging from minor skin infections to potentially fatal conditions such as pneumonia, meningitis and septicaemia. The pathogen is a leading cause of nosocomial acquired infections, a problem that is exacerbated by the existence of methicillin- and glycopeptide antibiotic-resistant strains which can be challenging to treat. Alanine racemase (Alr) is a pyridoxal-5'-phosphate-dependent enzyme which catalyzes reversible racemization between enantiomers of alanine. As D-alanine is an essential component of the bacterial cell-wall peptidoglycan, inhibition of Alr is lethal to prokaryotes. Additionally, while ubiquitous amongst bacteria, this enzyme is absent in humans and most eukaryotes, making it an excellent antibiotic drug target. The crystal structure of S. aureus alanine racemase (Alr(Sas)), the sequence of which corresponds to that from the highly antibiotic-resistant Mu50 strain, has been solved to 2.15 Å resolution. Comparison of the Alr(Sas) structure with those of various alanine racemases demonstrates a conserved overall fold, with the enzyme sharing most similarity to those from other Gram-positive bacteria. Structural examination indicates that the active-site binding pocket, dimer interface and active-site entryway of the enzyme are potential targets for structure-aided inhibitor design. Kinetic constants were calculated in this study and are reported here. The potential for a disulfide bond in this structure is noted. This structural and biochemical information provides a template for future structure-based drug-development efforts targeting Alr(Sas).
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Affiliation(s)
- Emma R. Scaletti
- Department of Biochemistry, University of Otago, Dunedin, New Zealand
| | - Sylvia R. Luckner
- Department of Biochemistry, University of Otago, Dunedin, New Zealand
| | - Kurt L. Krause
- Department of Biochemistry, University of Otago, Dunedin, New Zealand
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22
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Kuan YC, Kao CH, Chen CH, Chen CC, Hu HY, Hsu WH. Biochemical characterization of a novel lysine racemase from Proteus mirabilis BCRC10725. Process Biochem 2011. [DOI: 10.1016/j.procbio.2011.06.019] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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23
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Conti P, Tamborini L, Pinto A, Blondel A, Minoprio P, Mozzarelli A, De Micheli C. Drug Discovery Targeting Amino Acid Racemases. Chem Rev 2011; 111:6919-46. [DOI: 10.1021/cr2000702] [Citation(s) in RCA: 87] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- Paola Conti
- Dipartimento di Scienze Farmaceutiche “P. Pratesi”, via Mangiagalli 25, 20133 Milano, Italy
| | - Lucia Tamborini
- Dipartimento di Scienze Farmaceutiche “P. Pratesi”, via Mangiagalli 25, 20133 Milano, Italy
| | - Andrea Pinto
- Dipartimento di Scienze Farmaceutiche “P. Pratesi”, via Mangiagalli 25, 20133 Milano, Italy
| | - Arnaud Blondel
- Institut Pasteur, Unité de Bioinformatique Structurale, CNRS-URA 2185, Département de Biologie Structurale et Chimie, 25 rue du Dr. Roux, 75724 Paris, France
| | - Paola Minoprio
- Institut Pasteur, Laboratoire des Processus Infectieux à Trypanosoma; Département d’Infection et Epidémiologie; 25 rue du Dr. Roux, 75724 Paris, France
| | - Andrea Mozzarelli
- Dipartimento di Biochimica e Biologia Molecolare, via G. P. Usberti 23/A, 43100 Parma, Italy
- Istituto di Biostrutture e Biosistemi, viale Medaglie d’oro, Roma, Italy
| | - Carlo De Micheli
- Dipartimento di Scienze Farmaceutiche “P. Pratesi”, via Mangiagalli 25, 20133 Milano, Italy
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24
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Im H, Sharpe ML, Strych U, Davlieva M, Krause KL. The crystal structure of alanine racemase from Streptococcus pneumoniae, a target for structure-based drug design. BMC Microbiol 2011; 11:116. [PMID: 21612658 PMCID: PMC3146814 DOI: 10.1186/1471-2180-11-116] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2010] [Accepted: 05/25/2011] [Indexed: 11/17/2022] Open
Abstract
Background Streptococcus pneumoniae is a globally important pathogen. The Gram-positive diplococcus is a leading cause of pneumonia, otitis media, bacteremia, and meningitis, and antibiotic resistant strains have become increasingly common over recent years.
Alanine racemase is a ubiquitous enzyme among bacteria and provides the essential cell wall precursor, D-alanine. Since it is absent in humans, this enzyme is an attractive target for the development of drugs against S. pneumoniae and other bacterial pathogens. Results Here we report the crystal structure of alanine racemase from S. pneumoniae (AlrSP). Crystals diffracted to a resolution of 2.0 Å and belong to the space group P3121 with the unit cell parameters a = b = 119.97 Å, c = 118.10 Å, α = β = 90° and γ = 120°. Structural comparisons show that AlrSP shares both an overall fold and key active site residues with other bacterial alanine racemases. The active site cavity is similar to other Gram positive alanine racemases, featuring a restricted but conserved entryway. Conclusions We have solved the structure of AlrSP, an essential step towards the development of an accurate pharmacophore model of the enzyme, and an important contribution towards our on-going alanine racemase structure-based drug design project. We have identified three regions on the enzyme that could be targeted for inhibitor design, the active site, the dimer interface, and the active site entryway.
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Affiliation(s)
- Hookang Im
- Research Institute of Pharmaceutical Sciences, College of Pharmacy, Seoul National University, Seoul, Korea
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25
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Lowther J, Yard BA, Johnson KA, Carter LG, Bhat VT, Raman MCC, Clarke DJ, Ramakers B, McMahon SA, Naismith JH, Campopiano DJ. Inhibition of the PLP-dependent enzyme serine palmitoyltransferase by cycloserine: evidence for a novel decarboxylative mechanism of inactivation. MOLECULAR BIOSYSTEMS 2010; 6:1682-93. [PMID: 20445930 PMCID: PMC3670083 DOI: 10.1039/c003743e] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Cycloserine (CS, 4-amino-3-isoxazolidone) is a cyclic amino acid mimic that is known to inhibit many essential pyridoxal 5'-phosphate (PLP)-dependent enzymes. Two CS enantiomers are known; D-cycloserine (DCS, also known as Seromycin) is a natural product that is used to treat resistant Mycobacterium tuberculosis infections as well as neurological disorders since it is a potent NMDA receptor agonist, and L-cycloserine (LCS) is a synthetic enantiomer whose usefulness as a drug has been hampered by its inherent toxicity arising through inhibition of sphingolipid metabolism. Previous studies on various PLP-dependent enzymes revealed a common mechanism of inhibition by both enantiomers of CS; the PLP cofactor is disabled by forming a stable 3-hydroxyisoxazole/pyridoxamine 5'-phosphate (PMP) adduct at the active site where the cycloserine ring remains intact. Here we describe a novel mechanism of CS inactivation of the PLP-dependent enzyme serine palmitoyltransferase (SPT) from Sphingomonas paucimobilis. SPT catalyses the condensation of l-serine and palmitoyl-CoA, the first step in the de novo sphingolipid biosynthetic pathway. We have used a range of kinetic, spectroscopic and structural techniques to postulate that both LCS and DCS inactivate SPT by transamination to form a free pyridoxamine 5'-phosphate (PMP) and beta-aminooxyacetaldehyde that remain bound at the active site. We suggest this occurs by ring opening of the cycloserine ring followed by decarboxylation. Enzyme kinetics show that inhibition is reversed by incubation with excess PLP and that LCS is a more effective SPT inhibitor than DCS. UV-visible spectroscopic data, combined with site-directed mutagenesis, suggest that a mobile Arg(378) residue is involved in cycloserine inactivation of SPT.
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Affiliation(s)
- Jonathan Lowther
- EaStChem, School of Chemistry, The University of Edinburgh, West Mains Road, Edinburgh, EH9 3JJ, Scotland, UK
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