1
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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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2
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Bearne SL, Hayden JA. Application of circular dichroism-based assays to racemases and epimerases: Recognition and catalysis of reactions of chiral substrates by mandelate racemase. Methods Enzymol 2023; 685:127-169. [PMID: 37245900 DOI: 10.1016/bs.mie.2023.03.014] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Racemases and epimerases have attracted much interest because of their astonishing ability to catalyze the rapid α-deprotonation of carbon acid substrates with high pKa values (∼13-30) leading to the formation of d-amino acids or various carbohydrate diastereomers that serve important roles in both normal physiology and pathology. Enzymatic assays to measure the initial rates of reactions catalyzed by these enzymes are discussed using mandelate racemase (MR) as an example. For MR, a convenient, rapid, and versatile circular dichroism (CD)-based assay has been used to determine the kinetic parameters accompanying the MR-catalyzed racemization of mandelate and alternative substrates. This direct, continuous assay permits real time monitoring of reaction progress, the rapid determination of initial velocities, and immediate recognition of anomalous behaviors. MR recognizes chiral substrates primarily through interactions of the phenyl ring of (R)- or (S)-mandelate with the hydrophobic R- or S-pocket at the active site, respectively. During catalysis, the carboxylate and α-hydroxyl groups of the substrate remain fixed in place through interactions with the Mg2+ ion and multiple H-bonding interactions, while the phenyl ring moves between the R- and S-pockets. The minimal requirements for the substrate appear to be the presence of a glycolate or glycolamide moiety, and a hydrophobic group of limited size that can stabilize the carbanionic intermediate through resonance or strong inductive effects. Similar CD-based assays may be applied to determine the activity of other racemases or epimerases with proper consideration of the molar ellipticity, wavelength, overall absorbance of the sample, and the light pathlength.
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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.
| | - Joshua A Hayden
- Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, NS, Canada
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3
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Ngo HPT, Nguyen DQ, Park H, Park YS, Kwak K, Kim T, Lee JH, Cho KS, Kang LW. Conformational change of organic cofactor PLP is essential for catalysis in PLP-dependent enzymes. BMB Rep 2022; 55:439-446. [PMID: 36104257 PMCID: PMC9537024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2022] [Revised: 06/21/2022] [Accepted: 07/11/2022] [Indexed: 03/08/2024] Open
Abstract
Pyridoxal 5'-phosphate (PLP)-dependent enzymes are ubiquitous, catalyzing various biochemical reactions of approximately 4% of all classified enzymatic activities. They transform amines and amino acids into important metabolites or signaling molecules and are important drug targets in many diseases. In the crystal structures of PLP-dependent enzymes, organic cofactor PLP showed diverse conformations depending on the catalytic step. The conformational change of PLP is essential in the catalytic mechanism. In the study, we review the sophisticated catalytic mechanism of PLP, especially in transaldimination reactions. Most drugs targeting PLP-dependent enzymes make a covalent bond to PLP with the transaldimination reaction. A detailed understanding of organic cofactor PLP will help develop a new drug against PLP-dependent enzymes. [BMB Reports 2022; 55(9): 439-446].
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Affiliation(s)
- Ho-Phuong-Thuy Ngo
- Department of Biological Sciences, Konkuk University, Seoul 05029, Korea
| | - Diem Quynh Nguyen
- Department of Biological Sciences, Konkuk University, Seoul 05029, Korea
| | - Hyunjae Park
- Department of Biological Sciences, Konkuk University, Seoul 05029, Korea
| | - Yoon Sik Park
- Department of Biological Sciences, Konkuk University, Seoul 05029, Korea
| | - Kiwoong Kwak
- Department of Biological Sciences, Konkuk University, Seoul 05029, Korea
| | - Taejoon Kim
- Department of Biological Sciences, Konkuk University, Seoul 05029, Korea
| | - Jang Ho Lee
- Department of Biological Sciences, Konkuk University, Seoul 05029, Korea
| | - Kyoung Sang Cho
- Department of Biological Sciences, Konkuk University, Seoul 05029, Korea
| | - Lin-Woo Kang
- Department of Biological Sciences, Konkuk University, Seoul 05029, Korea
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4
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Nakamura R, Ogawa S, Takahashi Y, Fujishiro T. Cycloserine enantiomers inhibit PLP‐dependent cysteine desulfurase SufS via distinct mechanisms. FEBS J 2022; 289:5947-5970. [DOI: 10.1111/febs.16455] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2021] [Revised: 03/20/2022] [Accepted: 04/07/2022] [Indexed: 01/31/2023]
Affiliation(s)
- Ryosuke Nakamura
- Department of Biochemistry and Molecular Biology Graduate School of Science and Engineering Saitama University Japan
| | - Shoko Ogawa
- Department of Biochemistry and Molecular Biology Graduate School of Science and Engineering Saitama University Japan
| | - Yasuhiro Takahashi
- Department of Biochemistry and Molecular Biology Graduate School of Science and Engineering Saitama University Japan
| | - Takashi Fujishiro
- Department of Biochemistry and Molecular Biology Graduate School of Science and Engineering Saitama University Japan
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5
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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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6
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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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7
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Seddon JA, Weld ED, Schaaf HS, Garcia-Prats AJ, Kim S, Hesseling AC. Conducting efficacy trials in children with MDR-TB: what is the rationale and how should they be done? Int J Tuberc Lung Dis 2019; 22:24-33. [PMID: 29665950 DOI: 10.5588/ijtld.17.0359] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
Paediatric anti-tuberculosis treatment trials have traditionally been limited to Phase I/II studies evaluating the drug pharmacokinetics and safety in children, with assumptions about efficacy made by extrapolating data from adults. However, it is increasingly being recognised that, in some circumstances, efficacy trials are required in children. The current treatment for children with multidrug-resistant tuberculosis (MDR-TB) is long and toxic; shorter, safer regimens, using novel agents, require urgent evaluation. Given the changing pattern of drug metabolism, disease spectrum and rates of TB disease confirmation with age, decisions around inclusion criteria require careful consideration. The most straightforward MDR-TB efficacy trial would include only children with confirmed MDR-TB and no additional drug resistance. Given that it may be unclear at the time treatment is initiated whether the diagnosis will ultimately be confirmed and what the final drug resistance profile will be, this presents a unique challenge in children. Recruiting only these children would, however, limit the generalisability of such a trial, as in reality the majority of children with TB do not have bacteriologically confirmed disease. Given the good existing treatment outcomes with current routine regimens for children with MDR-TB, conducting a superiority trial may not be the optimal design. Demonstrating non-inferiority of efficacy, but superiority with regard to safety, would be an alternative strategy. Using standardised control and experimental MDR-TB treatment regimens is challenging given the wide spectrum of paediatric disease. However, using variable regimens would make interpretation challenging. A paediatric MDR-TB efficacy trial is urgently needed, and with global collaboration and capacity building, is highly feasible.
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Affiliation(s)
- J A Seddon
- Centre for International Child Health, Department of Paediatrics, Imperial College London, London, UK
| | - E D Weld
- Division of Clinical Pharmacology, Division of Infectious Disease, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - H S Schaaf
- Desmond Tutu TB Centre, Department of Paediatrics and Child Health, Faculty of Medicine and Health Sciences, Stellenbosch University, Cape Town, South Africa
| | - A J Garcia-Prats
- Desmond Tutu TB Centre, Department of Paediatrics and Child Health, Faculty of Medicine and Health Sciences, Stellenbosch University, Cape Town, South Africa
| | - S Kim
- Center for Biostatistics in AIDS Research and Department of Biostatistics, Harvard T H Chan School of Public Health, Boston, Massachusetts, USA
| | - A C Hesseling
- Desmond Tutu TB Centre, Department of Paediatrics and Child Health, Faculty of Medicine and Health Sciences, Stellenbosch University, Cape Town, South Africa
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8
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O'Neill EC, Schorn M, Larson CB, Millán-Aguiñaga N. Targeted antibiotic discovery through biosynthesis-associated resistance determinants: target directed genome mining. Crit Rev Microbiol 2019; 45:255-277. [PMID: 30985219 DOI: 10.1080/1040841x.2019.1590307] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Intense competition between microbes in the environment has directed the evolution of antibiotic production in bacteria. Humans have harnessed these natural molecules for medicinal purposes, magnifying them from environmental concentrations to industrial scale. This increased exposure to antibiotics has amplified antibiotic resistance across bacteria, spurring a global antimicrobial crisis and a search for antibiotics with new modes of action. Genetic insights into these antibiotic-producing microbes reveal that they have evolved several resistance strategies to avoid self-toxicity, including product modification, substrate transport and binding, and target duplication or modification. Of these mechanisms, target duplication or modification will be highlighted in this review, as it uniquely links an antibiotic to its mode of action. We will further discuss and propose a strategy to mine microbial genomes for these genes and their associated biosynthetic gene clusters to discover novel antibiotics using target directed genome mining.
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Affiliation(s)
- Ellis C O'Neill
- a Department of Plant Sciences, University of Oxford , Oxford , Oxfordshire , UK
| | - Michelle Schorn
- b Center for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California , San Diego , CA , USA
| | - Charles B Larson
- b Center for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, University of California , San Diego , CA , USA
| | - Natalie Millán-Aguiñaga
- c Universidad Autónoma de Baja California, Facultad de Ciencias Marinas , Ensenada , Baja California , México
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9
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Duque E, Daddaoua A, Cordero BF, De la Torre J, Antonia Molina-Henares M, Ramos JL. Identification and elucidation of in vivo function of two alanine racemases from Pseudomonas putida KT2440. ENVIRONMENTAL MICROBIOLOGY REPORTS 2017; 9:581-588. [PMID: 28799718 DOI: 10.1111/1758-2229.12576] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/04/2017] [Accepted: 08/03/2017] [Indexed: 06/07/2023]
Abstract
The genome of Pseudomonas putida KT2440 contains two open reading frames (ORFs), PP_3722 and PP_5269, that encode proteins with a Pyridoxal phosphate binding motif and a high similarity to alanine racemases. Alanine racemases play a key role in the biosynthesis of D-alanine, a crucial amino acid in the peptidoglycan layer. For these ORFs, we generated single and double mutants and found that inactivation of PP_5269 resulted in D-alanine auxotrophy, while inactivation of PP_3722 did not. Furthermore, as expected, the PP_3722/PP_5269 double mutant was a strict auxotroph for D-alanine. These results indicate that PP_5269 is an alr allele and that it is the essential alanine racemase in P. putida. We observed that the PP_5269 mutant grew very slowly, while the double PP_5269/PP_3722 mutant did not grow at all. This suggests that PP_3722 may replace PP_5269 in vivo. In fact, when the ORF encoding PP_3772 was cloned into a wide host range expression vector, ORF PP_3722 successfully complemented P. putida PP_5269 mutants. We purified both proteins to homogeneity and while they exhibit similar KM values, the Vmax of PP_5269 is fourfold higher than that of PP_3722. Here, we propose that PP_5269 and PP_3722 encode functional alanine racemases and that these genes be named alr-1 and alr-2 respectively.
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Affiliation(s)
- Estrella Duque
- Department of Environmental Protection, CSIC-Estación Experimental del Zaidín, Granada, Spain
| | - Abdelali Daddaoua
- Department of Environmental Protection, CSIC-Estación Experimental del Zaidín, Granada, Spain
| | - Baldo F Cordero
- Department of Environmental Protection, CSIC-Estación Experimental del Zaidín, Granada, Spain
| | - Jesús De la Torre
- Department of Environmental Protection, CSIC-Estación Experimental del Zaidín, Granada, Spain
| | | | - Juan-Luis Ramos
- Department of Environmental Protection, CSIC-Estación Experimental del Zaidín, Granada, Spain
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10
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Structural and functional characterization of the alanine racemase from Streptomyces coelicolor A3(2). Biochem Biophys Res Commun 2017; 483:122-128. [DOI: 10.1016/j.bbrc.2016.12.183] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2016] [Accepted: 12/28/2016] [Indexed: 02/02/2023]
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11
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Structure-based function analysis of putative conserved proteins with isomerase activity from Haemophilus influenzae. 3 Biotech 2015; 5:741-763. [PMID: 28324524 PMCID: PMC4569619 DOI: 10.1007/s13205-014-0274-1] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2014] [Accepted: 12/18/2014] [Indexed: 01/09/2023] Open
Abstract
Haemophilus influenzae, a Gram-negative bacterium and a member of the family Pasteurellaceae, causes chronic bronchitis, bacteremia, meningitis, etc. The H. influenzae is the first organism whose genome was completely sequenced and annotated. Here, we have extensively analyzed the genome of H. influenzae using available proteins structure and function analysis tools. The objective of this analysis is to assign a precise function to hypothetical proteins (HPs) whose functions are not determined so far. Function prediction of these proteins is helpful in precise understanding of mechanisms of pathogenesis and biochemical pathways important for selecting novel therapeutic target. After an extensive analysis of H. Influenzae genome we have found 13 HPs showing high level of sequence and structural similarity to the enzyme isomerase. Consequently, the structures of HPs have been modeled and analyzed to determine their precise functions. We found these HPs are alanine racemase, lysine 2, 3-aminomutase, topoisomerase DNA-binding C4 zinc finger, pseudouridine synthase B, C and E (Rlu B, C and E), hydroxypyruvate isomerase, nucleoside-diphosphate-sugar epimerase, amidophosphoribosyltransferase, aldose-1-epimerase, tautomerase/MIF, Xylose isomerase-like, have TIM barrel domain and sedoheptulose-7-phosphate isomerase like activity, signifying their corresponding functions in the H. influenzae. This work provides a better understanding of the role HPs with isomerase activities in the survival and pathogenesis of H. influenzae.
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12
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Sugiyama M. Structural biological study of self-resistance determinants in antibiotic-producing actinomycetes. J Antibiot (Tokyo) 2015; 68:543-50. [PMID: 25873321 DOI: 10.1038/ja.2015.32] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2014] [Revised: 02/13/2015] [Accepted: 02/21/2015] [Indexed: 11/09/2022]
Abstract
As antibiotics act to inhibit the growth of bacteria, the drugs are useful for treating bacterial infectious diseases. However, microorganisms that produce antibiotics must be protected from the lethal effect of their own antibiotic product. In this review, the fruit of our group's current research on self-protection mechanisms of Streptomyces producing antibiotics that inhibit DNA, protein and bacterial cell wall syntheses will be described.
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Affiliation(s)
- Masanori Sugiyama
- Department of Molecular Microbiology and Biotechnology, Graduate School of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan
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13
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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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14
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Asojo OA, Nelson SK, Mootien S, Lee Y, Rezende WC, Hyman DA, Matsumoto MM, Reiling S, Kelleher A, Ledizet M, Koski RA, Anthony KG. Structural and biochemical analyses of alanine racemase from the multidrug-resistant Clostridium difficile strain 630. ACTA CRYSTALLOGRAPHICA. SECTION D, BIOLOGICAL CRYSTALLOGRAPHY 2014; 70:1922-33. [PMID: 25004969 PMCID: PMC4089486 DOI: 10.1107/s1399004714009419] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/01/2014] [Accepted: 04/26/2014] [Indexed: 05/04/2024]
Abstract
Clostridium difficile, a Gram-positive, spore-forming anaerobic bacterium, is the leading cause of infectious diarrhea among hospitalized patients. C. difficile is frequently associated with antibiotic treatment, and causes diseases ranging from antibiotic-associated diarrhea to life-threatening pseudomembranous colitis. The severity of C. difficile infections is exacerbated by the emergence of hypervirulent and multidrug-resistant strains, which are difficult to treat and are often associated with increased mortality rates. Alanine racemase (Alr) is a pyridoxal-5'-phosphate (PLP)-dependent enzyme that catalyzes the reversible racemization of L- and D-alanine. Since D-alanine is an essential component of the bacterial cell-wall peptidoglycan, and there are no known Alr homologs in humans, this enzyme is being tested as an antibiotic target. Cycloserine is an antibiotic that inhibits Alr. In this study, the catalytic properties and crystal structures of recombinant Alr from the virulent and multidrug-resistant C. difficile strain 630 are presented. Three crystal structures of C. difficile Alr (CdAlr), corresponding to the complex with PLP, the complex with cycloserine and a K271T mutant form of the enzyme with bound PLP, are presented. The structures are prototypical Alr homodimers with two active sites in which the cofactor PLP and cycloserine are localized. Kinetic analyses reveal that the K271T mutant CdAlr has the highest catalytic constants reported to date for any Alr. Additional studies are needed to identify the basis for the high catalytic activity. The structural and activity data presented are first steps towards using CdAlr for the development of structure-based therapeutics for C. difficile infections.
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Affiliation(s)
- Oluwatoyin A. Asojo
- National School of Tropical Medicine, Department of Pediatrics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Sarah K. Nelson
- National School of Tropical Medicine, Department of Pediatrics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Sara Mootien
- L Diagnostics LLC, 300 George Street, New Haven, CT 06511, USA
| | - Yashang Lee
- L Diagnostics LLC, 300 George Street, New Haven, CT 06511, USA
| | - Wanderson C. Rezende
- National School of Tropical Medicine, Department of Pediatrics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Daniel A. Hyman
- National School of Tropical Medicine, Department of Pediatrics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Monica M. Matsumoto
- National School of Tropical Medicine, Department of Pediatrics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Scott Reiling
- Pathology and Microbiology Department, University of Nebraska Medical Center, Omaha, NE 68105, USA
| | - Alan Kelleher
- National School of Tropical Medicine, Department of Pediatrics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Michel Ledizet
- L Diagnostics LLC, 300 George Street, New Haven, CT 06511, USA
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15
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Ollivaux C, Soyez D, Toullec JY. Biogenesis of d
-amino acid containing peptides/proteins: where, when and how? J Pept Sci 2014; 20:595-612. [DOI: 10.1002/psc.2637] [Citation(s) in RCA: 85] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2013] [Revised: 03/13/2014] [Accepted: 03/18/2014] [Indexed: 12/12/2022]
Affiliation(s)
- Céline Ollivaux
- Sorbonne Universités, UPMC Univ Paris 06, UMR 8227; Integrative Biology of Marine Models, Station Biologique de Roscoff; CS 90074, F-29688 Roscoff cedex France
- CNRS, UMR 8227; Integrative Biology of Marine Models, Station Biologique de Roscoff; CS 90074, F-29688 Roscoff cedex France
| | - Daniel Soyez
- Sorbonne Universités, UPMC Univ Paris 06, ER3; Biogenèse des signaux peptidiques; 7 Quai Saint Bernard F-75251 Paris cedex 05 France
- CNRS, ER3; Biogenèse des signaux peptidiques; 7 Quai Saint Bernard F-75251 Paris cedex 05 France
| | - Jean-Yves Toullec
- Sorbonne Universités, UPMC Univ Paris 06, UMR 7144; Adaptation et Diversité en Milieu Marin, Station Biologique de Roscoff; CS 90074, F-29688 Roscoff cedex France
- CNRS, UMR 7144; Adaptation et Diversité en Milieu Marin, Station Biologique de Roscoff; CS 90074, F-29688 Roscoff cedex France
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16
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Nikolaidis I, Favini-Stabile S, Dessen A. Resistance to antibiotics targeted to the bacterial cell wall. Protein Sci 2014; 23:243-59. [PMID: 24375653 DOI: 10.1002/pro.2414] [Citation(s) in RCA: 87] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2013] [Revised: 12/21/2013] [Accepted: 12/23/2013] [Indexed: 11/10/2022]
Abstract
Peptidoglycan is the main component of the bacterial cell wall. It is a complex, three-dimensional mesh that surrounds the entire cell and is composed of strands of alternating glycan units crosslinked by short peptides. Its biosynthetic machinery has been, for the past five decades, a preferred target for the discovery of antibacterials. Synthesis of the peptidoglycan occurs sequentially within three cellular compartments (cytoplasm, membrane, and periplasm), and inhibitors of proteins that catalyze each stage have been identified, although not all are applicable for clinical use. A number of these antimicrobials, however, have been rendered inactive by resistance mechanisms. The employment of structural biology techniques has been instrumental in the understanding of such processes, as well as the development of strategies to overcome them. This review provides an overview of resistance mechanisms developed toward antibiotics that target bacterial cell wall precursors and its biosynthetic machinery. Strategies toward the development of novel inhibitors that could overcome resistance are also discussed.
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Affiliation(s)
- I Nikolaidis
- Institut de Biologie Structurale (IBS), Université Grenoble Alpes, 6 rue Jules Horowitz, 38027, Grenoble, France; Commissariat à l'Energie Atomique et aux Energies Alternatives (CEA), Grenoble, France; Centre National de la Recherche Scientifique (CNRS), UMR 5075, Grenoble, France; Bijvoet Center for Biomolecular Research, Department of Biochemistry of Membranes, Utrecht University, Utrecht, The Netherlands
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17
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Espaillat A, Carrasco-López C, Bernardo-García N, Pietrosemoli N, Otero LH, Álvarez L, de Pedro MA, Pazos F, Davis BM, Waldor MK, Hermoso JA, Cava F. Structural basis for the broad specificity of a new family of amino-acid racemases. ACTA CRYSTALLOGRAPHICA. SECTION D, BIOLOGICAL CRYSTALLOGRAPHY 2014; 70:79-90. [PMID: 24419381 PMCID: PMC4984259 DOI: 10.1107/s1399004713024838] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/02/2013] [Accepted: 09/05/2013] [Indexed: 02/02/2023]
Abstract
Broad-spectrum amino-acid racemases (Bsrs) enable bacteria to generate noncanonical D-amino acids, the roles of which in microbial physiology, including the modulation of cell-wall structure and the dissolution of biofilms, are just beginning to be appreciated. Here, extensive crystallographic, mutational, biochemical and bioinformatic studies were used to define the molecular features of the racemase BsrV that enable this enzyme to accommodate more diverse substrates than the related PLP-dependent alanine racemases. Conserved residues were identified that distinguish BsrV and a newly defined family of broad-spectrum racemases from alanine racemases, and these residues were found to be key mediators of the multispecificity of BrsV. Finally, the structural analysis of an additional Bsr that was identified in the bioinformatic analysis confirmed that the distinguishing features of BrsV are conserved among Bsr family members.
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Affiliation(s)
- Akbar Espaillat
- Centro de Biología Molecular ‘Severo Ochoa’, Universidad Autónoma de Madrid–Consejo Superior de Investigaciones Científicas (CSIC), 28049 Madrid, Spain
- Department of Molecular Biology and Laboratory for Molecular Infection Medicine Sweden, Umeå Centre for Microbial Research, Umeå University, Umeå, Sweden
| | - César Carrasco-López
- Department of Crystallography and Structural Biology, Instituto de Química-Física ‘Rocasolano’–CSIC, 28006 Madrid, Spain
| | - Noelia Bernardo-García
- Department of Crystallography and Structural Biology, Instituto de Química-Física ‘Rocasolano’–CSIC, 28006 Madrid, Spain
| | | | - Lisandro H. Otero
- Department of Crystallography and Structural Biology, Instituto de Química-Física ‘Rocasolano’–CSIC, 28006 Madrid, Spain
| | - Laura Álvarez
- Centro de Biología Molecular ‘Severo Ochoa’, Universidad Autónoma de Madrid–Consejo Superior de Investigaciones Científicas (CSIC), 28049 Madrid, Spain
- Department of Molecular Biology and Laboratory for Molecular Infection Medicine Sweden, Umeå Centre for Microbial Research, Umeå University, Umeå, Sweden
| | - Miguel A. de Pedro
- Centro de Biología Molecular ‘Severo Ochoa’, Universidad Autónoma de Madrid–Consejo Superior de Investigaciones Científicas (CSIC), 28049 Madrid, Spain
| | | | - Brigid M. Davis
- Division of Infectious Diseases, Brigham and Women’s Hospital and Department of Microbiology and Immunobiology, Harvard Medical School and HHMI, Boston, MA 02115, USA
| | - Matthew K. Waldor
- Division of Infectious Diseases, Brigham and Women’s Hospital and Department of Microbiology and Immunobiology, Harvard Medical School and HHMI, Boston, MA 02115, USA
| | - Juan A. Hermoso
- Department of Crystallography and Structural Biology, Instituto de Química-Física ‘Rocasolano’–CSIC, 28006 Madrid, Spain
| | - Felipe Cava
- Centro de Biología Molecular ‘Severo Ochoa’, Universidad Autónoma de Madrid–Consejo Superior de Investigaciones Científicas (CSIC), 28049 Madrid, Spain
- Department of Molecular Biology and Laboratory for Molecular Infection Medicine Sweden, Umeå Centre for Microbial Research, Umeå University, Umeå, Sweden
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18
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Omotade TO, Heffron JD, Klimko CP, Marchand CL, Miller LL, Halasahoris SA, Bozue JA, Welkos SL, Cote CK. D-cycloserine or similar physiochemical compounds may be uniquely suited for use in Bacillus anthracis spore decontamination strategies. J Appl Microbiol 2013; 115:1343-56. [PMID: 23927578 DOI: 10.1111/jam.12322] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2013] [Revised: 07/18/2013] [Accepted: 07/30/2013] [Indexed: 02/06/2023]
Abstract
AIMS As observed in the aftermath of the anthrax attacks of 2001, decontamination and remediation of a site contaminated by the accidental or intentional release of Bacillus anthracis spores is difficult, costly and potentially damaging to the environment. The identification of novel strategies that neutralize the threat of spores while minimizing environmental damage remains a high priority. We investigated the efficacy of d-cycloserine (DCS), an antibiotic and inhibitor of the spore-associated enzyme (alanine racemase) responsible for converting l-alanine to d-alanine, as a spore germination enhancer and antimicrobial agent. METHODS AND RESULTS We characterized the impact of DCS exposure on both germinating spores and vegetative cells of fully virulent B. anthracis by evaluating spore germination kinetics, determining the minimum inhibitory concentrations (MICs) required to affect growth of the bacteria and performing macrophage viability assays. DCS enhanced germination induced by l-alanine and also efficiently killed the newly germinated spores. Furthermore, DCS proved nontoxic to macrophages at concentrations that provided protection from the killing effects of spores. Similar tests were conducted with Bacillus thuringiensis (subspecies kurstaki and Al Hakam) to determine its potential as a possible surrogate for B. anthracis field trials. Bacillus thuringiensis spores responded in a similar manner to B. anthracis spores when exposed to DCS. CONCLUSIONS These results further support that DCS augments the germination response of spores in the presence of l-alanine but also reveal that DCS is bactericidal towards germinating spores. SIGNIFICANCE AND IMPACT OF THE STUDY DCS (or similar compounds) may be uniquely suited for use as part of decontamination strategies by augmenting the induction of spore germination and then rendering the germinated spores nonviable.
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Affiliation(s)
- T O Omotade
- Bacteriology Division, United States Army Medical Research Institute of Infectious Diseases (USAMRIID), Fort Detrick, Frederick, MD, USA
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19
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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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20
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Xue Z, Hu Y, Xu S, Ohnishi K, Ma Y, Ju J, Zhao B. Characterization and preliminary mutation analysis of a thermostable alanine racemase from Thermoanaerobacter tengcongensis MB4. Extremophiles 2013; 17:611-21. [PMID: 23703245 DOI: 10.1007/s00792-013-0545-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2012] [Accepted: 05/12/2013] [Indexed: 10/26/2022]
Abstract
A thermostable alanine racemase from Thermoanaerobacter tengcongensis MB4 was successfully expressed in Escherichia coli and characterized. The full-length gene MBalr2 (1164 bp) encodes 388 amino acid residues including 6 out of 8 highly conserved amino acid residues at the entryway to the active site of alanine racemase. Recombinant MBAlr2 and three mutants (S171A, H359Y and double mutation S171A/H359Y) of MBAlr2 were purified by His6-tag affinity column and gel filtration chromatography. The purified protein MBAlr2 was a dimeric PLP-dependent enzyme with broad substrate specificity. The optimal racemization temperature and pH were 70-75 °C and 11.0, respectively. The kinetic parameters K m and V max of MBAlr2 at 70 °C, determined by HPLC, were 20.16 mM and 1414 μmol min(-1) for L-alanine, and 9.95 mM and 702.6 μmol min(-1) for D-alanine, respectively. Enzymatic assays showed that the activity of both mutants (S171A and H359Y) was lost, but the activity of mutant S171A/H359Y was recovered to 69.8 % of wild type, which suggested that residues Ser171 and His359 might be the important residues for catalytic mechanisms of MBAlr2.
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Affiliation(s)
- Zhangwei Xue
- College of Life Science, Hebei Normal University, Shijiazhuang 050024, China
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21
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Lee Y, Mootien S, Shoen C, Destefano M, Cirillo P, Asojo OA, Yeung KR, Ledizet M, Cynamon MH, Aristoff PA, Koski RA, Kaplan PA, Anthony KG. Inhibition of mycobacterial alanine racemase activity and growth by thiadiazolidinones. Biochem Pharmacol 2013; 86:222-30. [PMID: 23680030 DOI: 10.1016/j.bcp.2013.05.004] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2013] [Revised: 05/02/2013] [Accepted: 05/03/2013] [Indexed: 11/25/2022]
Abstract
The genus Mycobacterium includes non-pathogenic species such as M. smegmatis, and pathogenic species such as M. tuberculosis, the causative agent of tuberculosis (TB). Treatment of TB requires a lengthy regimen of several antibiotics, whose effectiveness has been compromised by the emergence of resistant strains. New antibiotics that can shorten the treatment course and those that have not been compromised by bacterial resistance are needed. In this study, we report that thiadiazolidinones, a relatively little-studied heterocyclic class, inhibit the activity of mycobacterial alanine racemase, an essential enzyme that converts l-alanine to d-alanine for peptidoglycan synthesis. Twelve members of the thiadiazolidinone family were evaluated for inhibition of M. tuberculosis and M. smegmatis alanine racemase activity and bacterial growth. Thiadiazolidinones inhibited M. tuberculosis and M. smegmatis alanine racemases to different extents with 50% inhibitory concentrations (IC50) ranging from <0.03 to 28μM and 23 to >150μM, respectively. The compounds also inhibited the growth of these bacteria, including multidrug resistant strains of M. tuberculosis. The minimal inhibitory concentrations (MIC) for drug-susceptible M. tuberculosis and M. smegmatis ranged from 6.25μg/ml to 100μg/ml, and from 1.56 to 6.25μg/ml for drug-resistant M. tuberculosis. The in vitro activities of thiadiazolidinones suggest that this family of compounds might represent starting points for medicinal chemistry efforts aimed at developing novel antimycobacterial agents.
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Affiliation(s)
- Yashang Lee
- L2 Diagnostics LLC, 300 George St., New Haven, CT 06511, USA
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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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23
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Wu HM, Kuan YC, Chu CH, Hsu WH, Wang WC. Crystal structures of lysine-preferred racemases, the non-antibiotic selectable markers for transgenic plants. PLoS One 2012; 7:e48301. [PMID: 23118975 PMCID: PMC3485190 DOI: 10.1371/journal.pone.0048301] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2012] [Accepted: 09/24/2012] [Indexed: 11/18/2022] Open
Abstract
Lysine racemase, a pyridoxal 5′-phosphate (PLP)-dependent amino acid racemase that catalyzes the interconversion of lysine enantiomers, is valuable to serve as a novel non-antibiotic selectable marker in the generation of transgenic plants. Here, we have determined the first crystal structure of a lysine racemase (Lyr) from Proteus mirabilis BCRC10725, which shows the highest activity toward lysine and weaker activity towards arginine. In addition, we establish the first broad-specificity amino acid racemase (Bar) structure from Pseudomonas putida DSM84, which presents not only the highest activity toward lysine but also remarkably broad substrate specificity. A complex structure of Bar-lysine is also established here. These structures demonstrate the similar fold of alanine racemase, which is a head-to-tail homodimer with each protomer containing an N-terminal (α/β)8 barrel and a C-terminal β-stranded domain. The active-site residues are located at the protomer interface that is a funnel-like cavity with two catalytic bases, one from each protomer, and the PLP binding site is at the bottom of this cavity. Structural comparisons, site-directed mutagenesis, kinetic, and modeling studies identify a conserved arginine and an adjacent conserved asparagine that fix the orientation of the PLP O3 atom in both structures and assist in the enzyme activity. Furthermore, side chains of two residues in α-helix 10 have been discovered to point toward the cavity and define the substrate specificity. Our results provide a structural foundation for the design of racemases with pre-determined substrate specificity and for the development of the non-antibiotic selection system in transgenic plants.
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Affiliation(s)
- Hsin-Mao Wu
- Institute of Molecular and Cellular Biology and Department of Life Science, National Tsing Hua University, Hsinchu, Taiwan
| | - Yi-Chia Kuan
- Institute of Molecular Biology, National Chung Hsing University, Taichung, Taiwan
| | - Chia-Han Chu
- Biomedical Science and Engineering Center, National Tsing Hua University, Hsinchu, Taiwan
| | - Wen-Hwei Hsu
- Institute of Molecular Biology, National Chung Hsing University, Taichung, Taiwan
| | - Wen-Ching Wang
- Institute of Molecular and Cellular Biology and Department of Life Science, National Tsing Hua University, Hsinchu, Taiwan
- Biomedical Science and Engineering Center, National Tsing Hua University, Hsinchu, Taiwan
- * E-mail:
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Development of a high-throughput screening method for racemase activity and its application to the identification of alanine racemase variants with activity towards l-arginine. Tetrahedron 2012. [DOI: 10.1016/j.tet.2012.06.062] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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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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26
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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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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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28
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Ju J, Xu S, Furukawa Y, Zhang Y, Misono H, Minamino T, Namba K, Zhao B, Ohnishi K. Correlation between catalytic activity and monomer-dimer equilibrium of bacterial alanine racemases. J Biochem 2010; 149:83-9. [PMID: 20971724 DOI: 10.1093/jb/mvq120] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
From the reaction mechanism and crystal structure analysis, a bacterial alanine racemase is believed to work as a homodimer with a substrate, l-alanine or d-alanine. We analysed oligomerization states of seven alanine racemases, biosynthetic and catabolic, from Escherichia coli, Salmonella typhimurium, Pseudomonas aeruginosa, P. putida and P. fluorescens, with three different methods, gel filtration chromatography, native PAGE and analytical ultracentrifugation. All alanine racemases were proved to be in a dynamic equilibrium between monomeric and dimeric form with every methods used in this study. In both biosynthetic and catabolic alanine racemases, association constants for dimerization were high for the enzymes with high V(max) values. The enzymes with low V(max) values gave the low association constants. We proposed that alanine racemases are classified into two types; the enzymes with low and high-equilibrium association constants for dimerization.
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Affiliation(s)
- Jiansong Ju
- College of Life Sciences, Hebei Normal University, Shijiazhuang 050016, Japan
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29
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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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30
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Couñago RM, Davlieva M, Strych U, Hill RE, Krause KL. Biochemical and structural characterization of alanine racemase from Bacillus anthracis (Ames). BMC STRUCTURAL BIOLOGY 2009; 9:53. [PMID: 19695097 PMCID: PMC2743695 DOI: 10.1186/1472-6807-9-53] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/06/2009] [Accepted: 08/20/2009] [Indexed: 12/04/2022]
Abstract
BACKGROUND Bacillus anthracis is the causative agent of anthrax and a potential bioterrorism threat. Here we report the biochemical and structural characterization of B. anthracis (Ames) alanine racemase (AlrBax), an essential enzyme in prokaryotes and a target for antimicrobial drug development. We also compare the native AlrBax structure to a recently reported structure of the same enzyme obtained through reductive lysine methylation. RESULTS B. anthracis has two open reading frames encoding for putative alanine racemases. We show that only one, dal1, is able to complement a D-alanine auxotrophic strain of E. coli. Purified Dal1, which we term AlrBax, is shown to be a dimer in solution by dynamic light scattering and has a Vmax for racemization (L- to D-alanine) of 101 U/mg. The crystal structure of unmodified AlrBax is reported here to 1.95 A resolution. Despite the overall similarity of the fold to other alanine racemases, AlrBax makes use of a chloride ion to position key active site residues for catalysis, a feature not yet observed for this enzyme in other species. Crystal contacts are more extensive in the methylated structure compared to the unmethylated structure. CONCLUSION The chloride ion in AlrBax is functioning effectively as a carbamylated lysine making it an integral and unique part of this structure. Despite differences in space group and crystal form, the two AlrBax structures are very similar, supporting the case that reductive methylation is a valid rescue strategy for proteins recalcitrant to crystallization, and does not, in this case, result in artifacts in the tertiary structure.
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Affiliation(s)
- Rafael M Couñago
- Department of Biochemistry, University of Otago, Dunedin, New Zealand
| | - Milya Davlieva
- Department of Biochemistry Rice University, Houston, TX, USA
| | - Ulrich Strych
- Department of Biology and Biochemistry, University of Houston, Houston, TX, USA
| | - Ryan E Hill
- 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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Characterization of endogenous pyridoxal 5′-phosphate-dependent alanine racemase from Bacillus pseudofirmus OF4. J Biosci Bioeng 2009; 107:225-9. [DOI: 10.1016/j.jbiosc.2008.11.005] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2008] [Revised: 10/30/2008] [Accepted: 11/05/2008] [Indexed: 11/24/2022]
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Andrimid producers encode an acetyl-CoA carboxyltransferase subunit resistant to the action of the antibiotic. Proc Natl Acad Sci U S A 2008; 105:13321-6. [PMID: 18768797 DOI: 10.1073/pnas.0806873105] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Andrimid is a hybrid nonribosomal peptide-polyketide antibiotic that blocks the carboxyl-transfer reaction of bacterial acetyl-CoA carboxylase (ACC) and thereby inhibits fatty acid biosynthesis with submicromolar potency. The andrimid biosynthetic gene cluster from Pantoea agglomerans encodes an admT gene with homology to the acetyl-CoA carboxyltransferase (CT) beta-subunit gene accD. Escherichia coli cells overexpressing admT showed resistance to andrimid. Co-overproduction of AdmT with E. coli CT alpha-subunit AccA allowed for the in vitro reconstitution of an active heterologous tetrameric CT A(2)T(2) complex. A subsequent andrimid-inhibition assay revealed an IC(50) of 500 nM for this hybrid A(2)T(2) in contrast to that of 12 nM for E. coli CT A(2)D(2). These results validated that AdmT is an AccD homolog that confers resistance in the andrimid producer. Mutagenesis studies guided by the x-ray crystal structure of the E. coli A(2)D(2) complex disclosed a single amino acid mutation of AdmT (L203M) responsible for 5-fold andrimid sensitivity (IC(50) = 100 nM). Complementarily, the E. coli AccD mutant M203L became 5-fold more resistant in the CT assays. This observation allowed for bioinformatic identification of several Vibrio cholerae strains in which accD genes encode the Met<-->Leu switches, and their occurrences correlate predictively with sensitivities to andrimid in vivo.
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Wu D, Hu T, Zhang L, Chen J, Du J, Ding J, Jiang H, Shen X. Residues Asp164 and Glu165 at the substrate entryway function potently in substrate orientation of alanine racemase from E. coli: Enzymatic characterization with crystal structure analysis. Protein Sci 2008; 17:1066-76. [PMID: 18434499 DOI: 10.1110/ps.083495908] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
Alanine racemase (Alr) is an important enzyme that catalyzes the interconversion of L-alanine and D-alanine, an essential building block in the peptidoglycan biosynthesis. For the small size of the Alr active site, its conserved substrate entryway has been proposed as a potential choice for drug design. In this work, we fully analyzed the crystal structures of the native, the D-cycloserine-bound, and four mutants (P219A, E221A, E221K, and E221P) of biosynthetic Alr from Escherichia coli (EcAlr) and studied the potential roles in substrate orientation for the key residues involved in the substrate entryway in conjunction with the enzymatic assays. Structurally, it was discovered that EcAlr is similar to the Pseudomonas aeruginosa catabolic Alr in both overall and active site geometries. Mutation of the conserved negatively charged residue aspartate 164 or glutamate 165 at the substrate entryway could obviously reduce the binding affinity of enzyme against the substrate and decrease the turnover numbers in both D- to L-Ala and L- to D-Ala directions, especially when mutated to lysine with the opposite charge. However, mutation of Pro219 or Glu221 had only negligible or a small influence on the enzymatic activity. Together with the enzymatic and structural investigation results, we thus proposed that the negatively charged residues Asp164 and Glu165 around the substrate entryway play an important role in substrate orientation with cooperation of the positively charged Arg280 and Arg300 on the opposite monomer. Our findings are expected to provide some useful structural information for inhibitor design targeting the substrate entryway of Alr.
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Affiliation(s)
- Dalei Wu
- Drug Discovery and Design Center, State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, People's Republic of China
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Smith CA. Structure, function and dynamics in the mur family of bacterial cell wall ligases. J Mol Biol 2006; 362:640-55. [PMID: 16934839 DOI: 10.1016/j.jmb.2006.07.066] [Citation(s) in RCA: 129] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2006] [Revised: 07/23/2006] [Accepted: 07/26/2006] [Indexed: 10/24/2022]
Abstract
For bacteria, the structural integrity of its cell wall is of utmost importance for survival, and to this end, a rigid scaffold called peptidoglycan, comprised of sugar molecules and peptides, is synthesized and located outside the cytoplasmic membrane of the cell. Disruption of this peptidoglycan layer has for many years been a prime target for effective antibiotics, namely the penicillins and cephalosporins. Because this rigid layer is synthesized by a multi-step pathway numerous additional targets also exist that have no counterpart in the animal cell. Central to this pathway are four similar ligase enzymes, which add peptide groups to the sugar molecules, and interrupting these steps would ultimately prove fatal to the bacterial cell. The mechanisms of these ligases are well understood and the structures of all four of these ligases are now known. A detailed comparison of these four enzymes shows that considerable conformational changes are possible and that these changes, along with the recruitment of two different N-terminal binding domains, allows these enzymes to bind a substrate which at one end is identical and at the other has the growing polypeptide tail. Some insights into the structure-function relationships in these enzymes is presented.
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Affiliation(s)
- Clyde A Smith
- Stanford Synchrotron Radiation Laboratory, Menlo Park, CA 94025, USA.
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Ju J, Yokoigawa K, Misono H, Ohnishi K. Cloning of alanine racemase genes from Pseudomonas fluorescens strains and oligomerization states of gene products expressed in Escherichia coli. J Biosci Bioeng 2005; 100:409-17. [PMID: 16310730 DOI: 10.1263/jbb.100.409] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2005] [Accepted: 06/08/2005] [Indexed: 11/17/2022]
Abstract
Bacterial alanine racemase (EC 5.1.1.1) is a pyridoxal 5'-phosphate-dependent enzyme. Almost all eubacteria known to date possess a biosynthetic alr gene and some bacteria have an additional catabolic dadX gene. On the basis of the subunit structure, alanine racemases are classified into two types, monomeric and homodimeric. Alanine racemase genes were cloned from two distinct Pseudomonas fluorescens strains, the psychrotrophic TM5-2 strain and the soil-borne LRB3W1 strain, by means of complementing an Escherichia coli alanine racemase-deficient mutant. From the cloning results, both strains are likely to possess only one alanine racemase gene, dadX, in the same manner as the other P. fluorescens strains. Gene organization surrounding the dadX gene is highly conserved among Pseudomonas strains. The gene for D-amino acid dehydrogenase is located adjacent to the dadX gene in both strains. The DadX alanine racemases were expressed in E. coli as C-terminal His-tagged fusion proteins and purified to homogeneity. The catalytic activity of LRB3W1 DadX was higher than that of TM5-2 DadX. The association states of P. fluorescens DadX subunits in the E. coli alanine racemase-deficient mutant were analyzed by gel filtration chromatography. Alanine racemase subunits were demonstrated to exist as both monomers and dimers. The enzyme was in a monomer-dimer equilibrium, and the catalytic activity of the enzyme was proportional to the equilibrium association constant for dimerization.
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Affiliation(s)
- Jiansong Ju
- Department of Applied Bioresource Science, The United Graduate School of Agricultural Sciences, Ehime University, 3-5-7 Tarumi, Matsuyama, Ehime 790-8566, Japan
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Noda M, Kawahara Y, Ichikawa A, Matoba Y, Matsuo H, Lee DG, Kumagai T, Sugiyama M. Self-protection Mechanism in d-Cycloserine-producing Streptomyces lavendulae. J Biol Chem 2004; 279:46143-52. [PMID: 15302885 DOI: 10.1074/jbc.m404603200] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
An antibiotic, D-cycloserine (DCS), inhibits the catalytic activities of alanine racemase (ALR) and d-alanyl-d-alanine ligase (DDL), which are necessary for the biosynthesis of the bacterial cell wall. In this study, we cloned both genes encoding ALR and DDL, designated alrS and ddlS, respectively, from DCS-producing Streptomyces lavendulae ATCC25233. Each gene product was purified to homogeneity and characterized. Escherichia coli, transformed with a pET vector carrying alrS or ddlS, displays higher resistance to DCS than the same host carrying the E. coli ALR- or DDL-encoded gene inserted into the pET vector. Although the S. lavendulae DDL was competitively inhibited by DCS, the K(i) value (920 microM) was obviously higher (40 approximately 100-fold) than those for E. coli DdlA (9 microM) or DdlB (27 microM). The high K(i) value of the S. lavendulae DDL suggests that the enzyme may be a self-resistance determinant in the DCS-producing microorganism. Kinetic studies for the S. lavendulae ALR suggest that the time-dependent inactivation rate of the enzyme by DCS is absolutely slower than that of the E. coli ALR. We conclude that ALR from DCS-producing S. lavendulae is also one of the self-resistance determinants.
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Affiliation(s)
- Masafumi Noda
- Department of Molecular Microbiology and Biotechnology, Graduate School of Biomedical Sciences, Hiroshima University, Kasumi 1-2-3, Minami-Ku, Hiroshima 734-8551, Japan
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