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Drosophila carrying epilepsy-associated variants in the vitamin B6 metabolism gene PNPO display allele- and diet-dependent phenotypes. Proc Natl Acad Sci U S A 2022; 119:2115524119. [PMID: 35217610 PMCID: PMC8892510 DOI: 10.1073/pnas.2115524119] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/10/2022] [Indexed: 12/02/2022] Open
Abstract
Both genetic and environmental factors contribute to epilepsy. Understanding their contributions and interactions helps disease management. However, it is often challenging to study gene–environment interaction in humans due to their heterogeneous genetic background and less controllable environmental factors. The fruit fly, Drosophila melanogaster, has been proven to be a powerful model to study human diseases, including epilepsy. We generated knock-in flies carrying different epilepsy-associated pyridox(am)ine 5′-phosphate oxidase (PNPO) alleles and studied the developmental, behavioral, electrophysiological, and fitness effects of each mutant allele under different dietary conditions. We showed that phenotypes in knock-in flies are allele and diet dependent, providing clues for timely and specific diet interventions. Our results offer biological insights into mechanisms underlying phenotypic variations and specific therapeutic strategies. Pyridox(am)ine 5′-phosphate oxidase (PNPO) catalyzes the rate-limiting step in the synthesis of pyridoxal 5′-phosphate (PLP), the active form of vitamin B6 required for the synthesis of neurotransmitters gamma-aminobutyric acid (GABA) and the monoamines. Pathogenic variants in PNPO have been increasingly identified in patients with neonatal epileptic encephalopathy and early-onset epilepsy. These patients often exhibit different types of seizures and variable comorbidities. Recently, the PNPO gene has also been implicated in epilepsy in adults. It is unclear how these phenotypic variations are linked to specific PNPO alleles and to what degree diet can modify their expression. Using CRISPR-Cas9, we generated four knock-in Drosophila alleles, hWT, hR116Q, hD33V , and hR95H, in which the endogenous Drosophila PNPO was replaced by wild-type human PNPO complementary DNA (cDNA) and three epilepsy-associated variants. We found that these knock-in flies exhibited a wide range of phenotypes, including developmental impairments, abnormal locomotor activities, spontaneous seizures, and shortened life span. These phenotypes are allele dependent, varying with the known biochemical severity of these mutations and our characterized molecular defects. We also showed that diet treatments further diversified the phenotypes among alleles, and PLP supplementation at larval and adult stages prevented developmental impairments and seizures in adult flies, respectively. Furthermore, we found that hR95H had a significant dominant-negative effect, rendering heterozygous flies susceptible to seizures and premature death. Together, these results provide biological bases for the various phenotypes resulting from multifunction of PNPO, specific molecular and/or genetic properties of each PNPO variant, and differential allele–diet interactions.
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Barile A, Battista T, Fiorillo A, di Salvo ML, Malatesta F, Tramonti A, Ilari A, Contestabile R. Identification and characterization of the pyridoxal 5'-phosphate allosteric site in Escherichia coli pyridoxine 5'-phosphate oxidase. J Biol Chem 2021; 296:100795. [PMID: 34019876 PMCID: PMC8215295 DOI: 10.1016/j.jbc.2021.100795] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2021] [Revised: 05/10/2021] [Accepted: 05/14/2021] [Indexed: 11/16/2022] Open
Abstract
Pyridoxal 5’-phosphate (PLP), the catalytically active form of vitamin B6, plays a pivotal role in metabolism as an enzyme cofactor. PLP is a very reactive molecule and can be very toxic unless its intracellular concentration is finely regulated. In Escherichia coli, PLP formation is catalyzed by pyridoxine 5’-phosphate oxidase (PNPO), a homodimeric FMN-dependent enzyme that is responsible for the last step of PLP biosynthesis and is also involved in the PLP salvage pathway. We have recently observed that E. coli PNPO undergoes an allosteric feedback inhibition by PLP, caused by a strong allosteric coupling between PLP binding at the allosteric site and substrate binding at the active site. Here we report the crystallographic identification of the PLP allosteric site, located at the interface between the enzyme subunits and mainly circumscribed by three arginine residues (Arg23, Arg24, and Arg215) that form an “arginine cage” and efficiently trap PLP. The crystal structure of the PNPO–PLP complex, characterized by a marked structural asymmetry, presents only one PLP molecule bound at the allosteric site of one monomer and sheds light on the allosteric inhibition mechanism that makes the enzyme-substrate–PLP ternary complex catalytically incompetent. Site-directed mutagenesis studies focused on the arginine cage validate the identity of the allosteric site and provide an effective means to modulate the allosteric properties of the enzyme, from the loosening of the allosteric coupling (in the R23L/R24L and R23L/R215L variants) to the complete loss of allosteric properties (in the R23L/R24L/R21L variant).
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Affiliation(s)
- Anna Barile
- Istituto di Biologia e Patologia Molecolari, Consiglio Nazionale delle Ricerche, Roma, Italy; Dipartimento di Scienze Biochimiche "A. Rossi Fanelli", Istituto Pasteur Italia - Fondazione Cenci Bolognetti, Sapienza Università di Roma, Roma, Italy
| | - Theo Battista
- Istituto di Biologia e Patologia Molecolari, Consiglio Nazionale delle Ricerche, Roma, Italy; Dipartimento di Scienze Biochimiche "A. Rossi Fanelli", Istituto Pasteur Italia - Fondazione Cenci Bolognetti, Sapienza Università di Roma, Roma, Italy
| | - Annarita Fiorillo
- Istituto di Biologia e Patologia Molecolari, Consiglio Nazionale delle Ricerche, Roma, Italy; Dipartimento di Scienze Biochimiche "A. Rossi Fanelli", Istituto Pasteur Italia - Fondazione Cenci Bolognetti, Sapienza Università di Roma, Roma, Italy
| | - Martino Luigi di Salvo
- Dipartimento di Scienze Biochimiche "A. Rossi Fanelli", Istituto Pasteur Italia - Fondazione Cenci Bolognetti, Sapienza Università di Roma, Roma, Italy
| | - Francesco Malatesta
- Dipartimento di Scienze Biochimiche "A. Rossi Fanelli", Istituto Pasteur Italia - Fondazione Cenci Bolognetti, Sapienza Università di Roma, Roma, Italy
| | - Angela Tramonti
- Istituto di Biologia e Patologia Molecolari, Consiglio Nazionale delle Ricerche, Roma, Italy; Dipartimento di Scienze Biochimiche "A. Rossi Fanelli", Istituto Pasteur Italia - Fondazione Cenci Bolognetti, Sapienza Università di Roma, Roma, Italy
| | - Andrea Ilari
- Istituto di Biologia e Patologia Molecolari, Consiglio Nazionale delle Ricerche, Roma, Italy
| | - Roberto Contestabile
- Dipartimento di Scienze Biochimiche "A. Rossi Fanelli", Istituto Pasteur Italia - Fondazione Cenci Bolognetti, Sapienza Università di Roma, Roma, Italy.
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Harold LK, Antoney J, Ahmed FH, Hards K, Carr PD, Rapson T, Greening C, Jackson CJ, Cook GM. FAD-sequestering proteins protect mycobacteria against hypoxic and oxidative stress. J Biol Chem 2018; 294:2903-2912. [PMID: 30567740 DOI: 10.1074/jbc.ra118.006237] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2018] [Revised: 12/14/2018] [Indexed: 12/13/2022] Open
Abstract
The ability to persist in the absence of growth triggered by low oxygen levels is a critical process for the survival of mycobacterial species in many environmental niches. MSMEG_5243 (fsq), a gene of unknown function in Mycobacterium smegmatis, is up-regulated in response to hypoxia and regulated by DosRDosS/DosT, an oxygen- and redox-sensing two-component system that is highly conserved in mycobacteria. In this communication, we demonstrate that MSMEG_5243 is a flavin-sequestering protein and henceforth refer to it as Fsq. Using an array of biochemical and structural analyses, we show that Fsq is a member of the diverse superfamily of flavin- and deazaflavin-dependent oxidoreductases (FDORs) and is widely distributed in mycobacterial species. We created a markerless deletion mutant of fsq and demonstrate that fsq is required for cell survival during hypoxia. Using fsq deletion and overexpression, we found that fsq enhances cellular resistance to hydrogen peroxide treatment. The X-ray crystal structure of Fsq, solved to 2.7 Å, revealed a homodimeric organization with FAD bound noncovalently. The Fsq structure also uncovered no potential substrate-binding cavities, as the FAD is fully enclosed, and electrochemical studies indicated that the Fsq:FAD complex is relatively inert and does not share common properties with electron-transfer proteins. Taken together, our results suggest that Fsq reduces the formation of reactive oxygen species (ROS) by sequestering free FAD during recovery from hypoxia, thereby protecting the cofactor from undergoing autoxidation to produce ROS. This finding represents a new paradigm in mycobacterial adaptation to hypoxia.
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Affiliation(s)
- Liam K Harold
- From the Department of Microbiology and Immunology, School of Biomedical Sciences, University of Otago, Dunedin 9054, New Zealand.,Maurice Wilkins Centre for Molecular Biodiscovery, The University of Auckland, Private Bag 92019, Auckland 1042, New Zealand
| | - James Antoney
- Research School of Chemistry, The Australian National University, Canberra, Australia.,The Commonwealth Scientific and Industrial Research Organisation, Land and Water Flagship, Canberra, Australian Capital Territory, Australia, and
| | - F Hafna Ahmed
- Research School of Chemistry, The Australian National University, Canberra, Australia.,The Commonwealth Scientific and Industrial Research Organisation, Land and Water Flagship, Canberra, Australian Capital Territory, Australia, and
| | - Kiel Hards
- From the Department of Microbiology and Immunology, School of Biomedical Sciences, University of Otago, Dunedin 9054, New Zealand
| | - Paul D Carr
- Research School of Chemistry, The Australian National University, Canberra, Australia
| | - Trevor Rapson
- The Commonwealth Scientific and Industrial Research Organisation, Land and Water Flagship, Canberra, Australian Capital Territory, Australia, and
| | - Chris Greening
- The Commonwealth Scientific and Industrial Research Organisation, Land and Water Flagship, Canberra, Australian Capital Territory, Australia, and .,School of Biological Sciences, Monash University, Melbourne, Australia
| | - Colin J Jackson
- Research School of Chemistry, The Australian National University, Canberra, Australia,
| | - Gregory M Cook
- From the Department of Microbiology and Immunology, School of Biomedical Sciences, University of Otago, Dunedin 9054, New Zealand, .,Maurice Wilkins Centre for Molecular Biodiscovery, The University of Auckland, Private Bag 92019, Auckland 1042, New Zealand
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Gu J, Chen Y, Guo H, Sun M, Yang M, Wang X, Zhang X, Deng J. Lysine acetylation regulates the activity of Escherichia coli pyridoxine 5'-phosphate oxidase. Acta Biochim Biophys Sin (Shanghai) 2017; 49:186-192. [PMID: 28039149 DOI: 10.1093/abbs/gmw129] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2016] [Indexed: 11/14/2022] Open
Abstract
Nɛ-lysine acetylation is one of the most abundant post-translational modifications in eukaryote and prokaryote. Protein acetylome of Escherichia coli has been screened using mass spectrometry (MS) technology, and many acetylated proteins have been identified, including the pyridoxine 5'-phosphate oxidase (EcPNPOx), but the biological roles played by lysine acetylation in EcPNPOx still remain unknown. In this study, EcPNPOx was firstly overexpressed and purified, and two acetylated lysine residues were identified by the subsequent liquid chromatography-tandem mass spectrometry analysis. Site-directed mutagenesis analysis demonstrated that acetylated lysine residues play important roles in the enzymatic activity and enzymatic properties of the protein. EcPNPOx could be non-enzymatically acetylated by acetyl-phosphate and deacetylated by CobB in vitro. Furthermore, enzymatic activities of acetylated and deacetylated EcPNPOx were compared in vitro, and results showed that acetylation led to a decrease of its enzymatic activity, which could be rescued by CobB deacetylation. Taken together, our data suggest that CobB modulates the enzymatic activity of EcPNPOx in vitro.
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Affiliation(s)
- Jing Gu
- Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan 430071, China
| | - Yuanyuan Chen
- Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan 430071, China
- Huazhong Agricultural University, Wuhan 430070, China
| | - Hongsen Guo
- Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan 430071, China
- Huazhong Agricultural University, Wuhan 430070, China
| | - Manluan Sun
- Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan 430071, China
- University of Chinese Academy of Sciences, Beijing 100039, China
| | - Mingkun Yang
- Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430071, China
| | - Xude Wang
- Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan 430071, China
| | - Xian'en Zhang
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
| | - Jiaoyu Deng
- Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan 430071, China
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Ahmed FH, Mohamed AE, Carr PD, Lee BM, Condic-Jurkic K, O'Mara ML, Jackson CJ. Rv2074 is a novel F420 H2 -dependent biliverdin reductase in Mycobacterium tuberculosis. Protein Sci 2016; 25:1692-709. [PMID: 27364382 DOI: 10.1002/pro.2975] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2016] [Accepted: 06/29/2016] [Indexed: 12/12/2022]
Abstract
Bilirubin is a potent antioxidant that is produced from the reduction of the heme degradation product biliverdin. In mammalian cells and Cyanobacteria, NADH/NADPH-dependent biliverdin reductases (BVRs) of the Rossmann-fold have been shown to catalyze this reaction. Here, we describe the characterization of Rv2074 from Mycobacterium tuberculosis, which belongs to a structurally and mechanistically distinct family of F420 H2 -dependent BVRs (F-BVRs) that are exclusively found in Actinobacteria. We have solved the crystal structure of Rv2074 bound to its cofactor, F420 , and used this alongside molecular dynamics simulations, site-directed mutagenesis and NMR spectroscopy to elucidate its catalytic mechanism. The production of bilirubin by Rv2074 could exploit the anti-oxidative properties of bilirubin and contribute to the range of immuno-evasive mechanisms that have evolved in M. tuberculosis to allow persistent infection.
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Affiliation(s)
- F Hafna Ahmed
- Research School of Chemistry, The Australian National University, Canberra, ACT, 2601, Australia
| | - A Elaaf Mohamed
- Research School of Chemistry, The Australian National University, Canberra, ACT, 2601, Australia
| | - Paul D Carr
- Research School of Chemistry, The Australian National University, Canberra, ACT, 2601, Australia
| | - Brendon M Lee
- Research School of Chemistry, The Australian National University, Canberra, ACT, 2601, Australia
| | - Karmen Condic-Jurkic
- Research School of Chemistry, The Australian National University, Canberra, ACT, 2601, Australia
| | - Megan L O'Mara
- Research School of Chemistry, The Australian National University, Canberra, ACT, 2601, Australia
| | - Colin J Jackson
- Research School of Chemistry, The Australian National University, Canberra, ACT, 2601, Australia
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6
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Ahmed FH, Carr PD, Lee BM, Afriat-Jurnou L, Mohamed AE, Hong NS, Flanagan J, Taylor MC, Greening C, Jackson CJ. Sequence-Structure-Function Classification of a Catalytically Diverse Oxidoreductase Superfamily in Mycobacteria. J Mol Biol 2015; 427:3554-3571. [PMID: 26434506 DOI: 10.1016/j.jmb.2015.09.021] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2015] [Revised: 09/23/2015] [Accepted: 09/24/2015] [Indexed: 12/11/2022]
Abstract
The deazaflavin cofactor F420 enhances the persistence of mycobacteria during hypoxia, oxidative stress, and antibiotic treatment. However, the identities and functions of the mycobacterial enzymes that utilize F420 under these conditions have yet to be resolved. In this work, we used sequence similarity networks to analyze the distribution of the largest F420-dependent protein family in mycobacteria. We show that these enzymes are part of a larger split β-barrel enzyme superfamily (flavin/deazaflavin oxidoreductases, FDORs) that include previously characterized pyridoxamine/pyridoxine-5'-phosphate oxidases and heme oxygenases. We show that these proteins variously utilize F420, flavin mononucleotide, flavin adenine dinucleotide, and heme cofactors. Functional annotation using phylogenetic, structural, and spectroscopic methods revealed their involvement in heme degradation, biliverdin reduction, fatty acid modification, and quinone reduction. Four novel crystal structures show that plasticity in substrate binding pockets and modifications to cofactor binding motifs enabled FDORs to carry out a variety of functions. This systematic classification and analysis provides a framework for further functional analysis of the roles of FDORs in mycobacterial pathogenesis and persistence.
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Affiliation(s)
- F Hafna Ahmed
- Australian National University Research School of Chemistry, Sullivans Creek Road, Acton, ACT 2601, Australia
| | - Paul D Carr
- Australian National University Research School of Chemistry, Sullivans Creek Road, Acton, ACT 2601, Australia
| | - Brendon M Lee
- Australian National University Research School of Chemistry, Sullivans Creek Road, Acton, ACT 2601, Australia
| | - Livnat Afriat-Jurnou
- Australian National University Research School of Chemistry, Sullivans Creek Road, Acton, ACT 2601, Australia
| | - A Elaaf Mohamed
- Australian National University Research School of Chemistry, Sullivans Creek Road, Acton, ACT 2601, Australia
| | - Nan-Sook Hong
- Australian National University Research School of Chemistry, Sullivans Creek Road, Acton, ACT 2601, Australia
| | - Jack Flanagan
- University of Auckland Faculty of Medical and Health Sciences, 85 Park Road, Grafton, Auckland 2013, New Zealand
| | - Matthew C Taylor
- Commonwealth Scientific and Industrial Research Organisation Land and Water Flagship, Clunies Ross Street, Acton, ACT 2060, Australia
| | - Chris Greening
- Commonwealth Scientific and Industrial Research Organisation Land and Water Flagship, Clunies Ross Street, Acton, ACT 2060, Australia
| | - Colin J Jackson
- Australian National University Research School of Chemistry, Sullivans Creek Road, Acton, ACT 2601, Australia.
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7
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Experimental Evidence for a Revision in the Annotation of Putative Pyridoxamine 5'-Phosphate Oxidases P(N/M)P from Fungi. PLoS One 2015; 10:e0136761. [PMID: 26327315 PMCID: PMC4556617 DOI: 10.1371/journal.pone.0136761] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2015] [Accepted: 08/08/2015] [Indexed: 11/19/2022] Open
Abstract
Pyridoxinamine 5'-phosphate oxidases (P(N/M)P oxidases) that bind flavin mononucleotide (FMN) and oxidize pyridoxine 5'-phosphate or pyridoxamine 5'-phosphate to form pyridoxal 5'-phosphate (PLP) are an important class of enzymes that play a central role in cell metabolism. Failure to generate an adequate supply of PLP is very detrimental to most organisms and is often clinically manifested as a neurological disorder in mammals. In this study, we analyzed the function of YLR456W and YPR172W, two homologous genes of unknown function from S. cerevisiae that have been annotated as putative P(N/M)P oxidases based on sequence homology. Different experimental approaches indicated that neither protein catalyzes PLP formation nor binds FMN. On the other hand, our analysis confirmed the enzymatic activity of Pdx3, the S. cerevisiae protein previously implicated in PLP biosynthesis by genetic and structural characterization. After a careful sequence analysis comparing the putative and confirmed P(N/M)P oxidases, we found that the protein domain (PF01243) that led to the YLR456W and YPR172W annotation is a poor indicator of P(N/M)P oxidase activity. We suggest that a combination of two Pfam domains (PF01243 and PF10590) present in Pdx3 and other confirmed P(N/M)P oxidases would be a stronger predictor of this molecular function. This work exemplifies the importance of experimental validation to rectify genome annotation and proposes a revision in the annotation of at least 400 sequences from a wide variety of fungal species that are homologous to YLR456W and are currently misrepresented as putative P(N/M)P oxidases.
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Colinas M, Shaw HV, Loubéry S, Kaufmann M, Moulin M, Fitzpatrick TB. A pathway for repair of NAD(P)H in plants. J Biol Chem 2014; 289:14692-706. [PMID: 24706747 DOI: 10.1074/jbc.m114.556092] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Unwanted enzyme side reactions and spontaneous decomposition of metabolites can lead to a build-up of compounds that compete with natural enzyme substrates and must be dealt with for efficient metabolism. It has recently been realized that there are enzymes that process such compounds, formulating the concept of metabolite repair. NADH and NADPH are vital cellular redox cofactors but can form non-functional hydrates (named NAD(P)HX) spontaneously or enzymatically that compete with enzymes dependent on NAD(P)H, impairing normal enzyme function. Here we report on the functional characterization of components of a potential NAD(P)H repair pathway in plants comprising a stereospecific dehydratase (NNRD) and an epimerase (NNRE), the latter being fused to a vitamin B6 salvage enzyme. Through the use of the recombinant proteins, we show that the ATP-dependent NNRD and NNRE act concomitantly to restore NAD(P)HX to NAD(P)H. NNRD behaves as a tetramer and NNRE as a dimer, but the proteins do not physically interact. In vivo fluorescence analysis demonstrates that the proteins are localized to mitochondria and/or plastids, implicating these as the key organelles where this repair is required. Expression analysis indicates that whereas NNRE is present ubiquitously, NNRD is restricted to seeds but appears to be dispensable during the normal Arabidopsis life cycle.
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Affiliation(s)
- Maite Colinas
- From the Department of Botany and Plant Biology, University of Geneva, 1211 Geneva, Switzerland
| | - Holly V Shaw
- From the Department of Botany and Plant Biology, University of Geneva, 1211 Geneva, Switzerland
| | - Sylvain Loubéry
- From the Department of Botany and Plant Biology, University of Geneva, 1211 Geneva, Switzerland
| | - Markus Kaufmann
- From the Department of Botany and Plant Biology, University of Geneva, 1211 Geneva, Switzerland
| | - Michael Moulin
- From the Department of Botany and Plant Biology, University of Geneva, 1211 Geneva, Switzerland
| | - Teresa B Fitzpatrick
- From the Department of Botany and Plant Biology, University of Geneva, 1211 Geneva, Switzerland
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Ghatge MS, Contestabile R, di Salvo ML, Desai JV, Gandhi AK, Camara CM, Florio R, González IN, Parroni A, Schirch V, Safo MK. Pyridoxal 5'-phosphate is a slow tight binding inhibitor of E. coli pyridoxal kinase. PLoS One 2012; 7:e41680. [PMID: 22848564 PMCID: PMC3404986 DOI: 10.1371/journal.pone.0041680] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2012] [Accepted: 06/24/2012] [Indexed: 11/18/2022] Open
Abstract
Pyridoxal 5′-phosphate (PLP) is a cofactor for dozens of B6 requiring enzymes. PLP reacts with apo-B6 enzymes by forming an aldimine linkage with the ε-amino group of an active site lysine residue, thus yielding the catalytically active holo-B6 enzyme. During protein turnover, the PLP is salvaged by first converting it to pyridoxal by a phosphatase and then back to PLP by pyridoxal kinase. Nonetheless, PLP poses a potential toxicity problem for the cell since its reactive 4′-aldehyde moiety forms covalent adducts with other compounds and non-B6 proteins containing thiol or amino groups. The regulation of PLP homeostasis in the cell is thus an important, yet unresolved issue. In this report, using site-directed mutagenesis, kinetic, spectroscopic and chromatographic studies we show that pyridoxal kinase from E. coli forms a complex with the product PLP to form an inactive enzyme complex. Evidence is presented that, in the inhibited complex, PLP has formed an aldimine bond with an active site lysine residue during catalytic turnover. The rate of dissociation of PLP from the complex is very slow, being only partially released after a 2-hour incubation with PLP phosphatase. Interestingly, the inactive pyridoxal kinase•PLP complex can be partially reactivated by transferring the tightly bound PLP to an apo-B6 enzyme. These results open new perspectives on the mechanism of regulation and role of pyridoxal kinase in the Escherichia coli cell.
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Affiliation(s)
- Mohini S. Ghatge
- Department of Medicinal Chemistry, Institute for Structural Biology and Drug Discovery, Virginia Commonwealth University, Richmond, Virginia, United States of America
| | - Roberto Contestabile
- Istituto Pasteur-Fondazione Cenci Bolognetti and Dipartimento di Scienze Biochimiche, Sapienza Università di Roma, Roma, Italy
| | - Martino L. di Salvo
- Istituto Pasteur-Fondazione Cenci Bolognetti and Dipartimento di Scienze Biochimiche, Sapienza Università di Roma, Roma, Italy
| | - Jigar V. Desai
- Department of Medicinal Chemistry, Institute for Structural Biology and Drug Discovery, Virginia Commonwealth University, Richmond, Virginia, United States of America
| | - Amit K. Gandhi
- Department of Medicinal Chemistry, Institute for Structural Biology and Drug Discovery, Virginia Commonwealth University, Richmond, Virginia, United States of America
| | - Christina M. Camara
- Department of Medicinal Chemistry, Institute for Structural Biology and Drug Discovery, Virginia Commonwealth University, Richmond, Virginia, United States of America
| | - Rita Florio
- Istituto Pasteur-Fondazione Cenci Bolognetti and Dipartimento di Scienze Biochimiche, Sapienza Università di Roma, Roma, Italy
| | - Isabel N. González
- Consiglio Nazionale delle Ricerche, Istituto di Biologia Agroambientale e Forestale, Monterotondo Scalo, Roma, Italy
- Institute of Biocomputation and Physics of Complex Systems, Universidad de Zaragoza, Zaragoza, Spain
| | - Alessia Parroni
- Istituto Pasteur-Fondazione Cenci Bolognetti and Dipartimento di Scienze Biochimiche, Sapienza Università di Roma, Roma, Italy
| | - Verne Schirch
- Department of Medicinal Chemistry, Institute for Structural Biology and Drug Discovery, Virginia Commonwealth University, Richmond, Virginia, United States of America
| | - Martin K. Safo
- Department of Medicinal Chemistry, Institute for Structural Biology and Drug Discovery, Virginia Commonwealth University, Richmond, Virginia, United States of America
- * E-mail:
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Hilario E, Li Y, Niks D, Fan L. The structure of a Xanthomonas general stress protein involved in citrus canker reveals its flavin-binding property. ACTA CRYSTALLOGRAPHICA SECTION D: BIOLOGICAL CRYSTALLOGRAPHY 2012; 68:846-53. [PMID: 22751670 DOI: 10.1107/s0907444912014126] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/22/2012] [Accepted: 03/31/2012] [Indexed: 11/11/2022]
Abstract
Xanthomonas citri pv. citri (Xac) causes citrus canker and affects citrus agriculture worldwide. Functional genetic analysis has indicated that a putative general stress protein (XacGSP) encoded by the Xac2369 gene is involved in the bacterial infection. In this report, the crystal structure of XacGSP was determined to 2.5 Å resolution. There are four XacGSP molecules in the crystal asymmetric unit. Each XacGSP monomer folds into a six-stranded antiparallel β-barrel flanked by five α-helices. A C-terminal extension protrudes from the sixth β-strand of the β-barrel and pairs with its counterpart from another monomer to form a bridge between the two subunits of an XacGSP dimer. Two XacGSP dimers cross over each other to form a tetramer; the β-barrels from one dimer contact the β-barrels of the other, while the two bridges are distant from each other and do not make contacts. The three-dimensional structure of the XacGSP monomer is very similar to those of pyridoxine 5-phosphate oxidases, a group of enzymes that use flavin mononucleotide (FMN) as a cofactor. Consistent with this, purified XacGSP protein binds to both FMN and flavin adenine dinucleotide (FAD), suggesting that XacGSP may help the bacteria to react against the oxidative stress induced by the defense mechanisms of the plant.
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Affiliation(s)
- Eduardo Hilario
- Department of Biochemistry, University of California-Riverside, Riverside, California, USA
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Lapalikar GV, Taylor MC, Warden AC, Onagi H, Hennessy JE, Mulder RJ, Scott C, Brown SE, Russell RJ, Easton CJ, Oakeshott JG. Cofactor promiscuity among F420-dependent reductases enables them to catalyse both oxidation and reduction of the same substrate. Catal Sci Technol 2012. [DOI: 10.1039/c2cy20129a] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Mashalidis EH, Mukherjee T, Śledź P, Matak-Vinković D, Boshoff H, Abell C, Barry CE. Rv2607 from Mycobacterium tuberculosis is a pyridoxine 5'-phosphate oxidase with unusual substrate specificity. PLoS One 2011; 6:e27643. [PMID: 22110704 PMCID: PMC3215729 DOI: 10.1371/journal.pone.0027643] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2011] [Accepted: 10/21/2011] [Indexed: 11/26/2022] Open
Abstract
Despite intensive effort, the majority of the annotated Mycobacterium tuberculosis genome consists of genes encoding proteins of unknown or poorly understood function. For example, there are seven conserved hypothetical proteins annotated as homologs of pyridoxine 5′-phosphate oxidase (PNPOx), an enzyme that oxidizes pyridoxine 5′-phosphate (PNP) or pyridoxamine 5′-phosphate (PMP) to form pyridoxal 5′-phosphate (PLP). We have characterized the function of Rv2607 from Mycobacterium tuberculosis H37Rv and shown that it encodes a PNPOx that oxidizes PNP to PLP. The kcat and KM for this reaction were 0.01 s−1 and 360 µM, respectively. Unlike many PNPOx enzymes, Rv2607 does not recognize PMP as a substrate.
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Affiliation(s)
- Ellene H. Mashalidis
- National Institute of Allergy and Infectious Disease, National Institutes of Health, Bethesda, Maryland, United States of America
- Department of Chemistry, University of Cambridge, Cambridge, United Kingdom
| | - Tathagata Mukherjee
- National Institute of Allergy and Infectious Disease, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Paweł Śledź
- Department of Chemistry, University of Cambridge, Cambridge, United Kingdom
| | | | - Helena Boshoff
- National Institute of Allergy and Infectious Disease, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Chris Abell
- Department of Chemistry, University of Cambridge, Cambridge, United Kingdom
- * E-mail: (CA); (CEB)
| | - Clifton E. Barry
- National Institute of Allergy and Infectious Disease, National Institutes of Health, Bethesda, Maryland, United States of America
- * E-mail: (CA); (CEB)
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di Salvo ML, Contestabile R, Safo MK. Vitamin B6 salvage enzymes: Mechanism, structure and regulation. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2011; 1814:1597-608. [DOI: 10.1016/j.bbapap.2010.12.006] [Citation(s) in RCA: 128] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2010] [Accepted: 12/13/2010] [Indexed: 10/18/2022]
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14
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Musayev FN, Di Salvo ML, Saavedra MA, Contestabile R, Ghatge MS, Haynes A, Schirch V, Safo MK. Molecular basis of reduced pyridoxine 5'-phosphate oxidase catalytic activity in neonatal epileptic encephalopathy disorder. J Biol Chem 2009; 284:30949-56. [PMID: 19759001 DOI: 10.1074/jbc.m109.038372] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Mutations in pyridoxine 5'-phosphate oxidase are known to cause neonatal epileptic encephalopathy. This disorder has no cure or effective treatment and is often fatal. Pyridoxine 5'-phosphate oxidase catalyzes the oxidation of pyridoxine 5'-phosphate to pyridoxal 5'-phosphate, the active cofactor form of vitamin B(6) required by more than 140 different catalytic activities, including enzymes involved in amino acid metabolism and biosynthesis of neurotransmitters. Our aim is to elucidate the mechanism by which a homozygous missense mutation (R229W) in the oxidase, linked to neonatal epileptic encephalopathy, leads to reduced oxidase activity. The R229W variant is approximately 850-fold less efficient than the wild-type enzyme due to an approximately 192-fold decrease in pyridoxine 5'-phosphate affinity and an approximately 4.5-fold decrease in catalytic activity. There is also an approximately 50-fold reduction in the affinity of the R229W variant for the FMN cofactor. A 2.5 A crystal structure of the R229W variant shows that the substitution of Arg-229 at the FMN binding site has led to a loss of hydrogen-bond and/or salt-bridge interactions between FMN and Arg-229 and Ser-175. Additionally, the mutation has led to an alteration of the configuration of a beta-strand-loop-beta-strand structure at the active site, resulting in loss of two critical hydrogen-bond interactions involving residues His-227 and Arg-225, which are important for substrate binding and orientation for catalysis. These results provide a molecular basis for the phenotype associated with the R229W mutation, as well as providing a foundation for understanding the pathophysiological consequences of pyridoxine 5'-phosphate oxidase mutations.
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Affiliation(s)
- Faik N Musayev
- Department of Medicinal Chemistry, School of Pharmacy, and Institute for Structural Biology and Drug Discovery, Virginia Commonwealth University, Richmond, Virginia 23219, USA
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15
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Jackson CJ, Taylor MC, Tattersall DB, French NG, Carr PD, Ollis DL, Russell RJ, Oakeshott JG. Cloning, expression, purification, crystallization and preliminary X-ray studies of a pyridoxine 5'-phosphate oxidase from Mycobacterium smegmatis. Acta Crystallogr Sect F Struct Biol Cryst Commun 2008; 64:435-7. [PMID: 18453720 DOI: 10.1107/s1744309108011512] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2008] [Accepted: 04/22/2008] [Indexed: 11/10/2022]
Abstract
Pyridoxine 5'-phosphate oxidases (PNPOxs) are known to catalyse the terminal step in pyridoxal 5'-phosphate biosynthesis in a flavin mononucleotide-dependent manner in humans and Escherichia coli. Recent reports of a putative PNPOx from Mycobacterium tuberculosis, Rv1155, suggest that the cofactor or catalytic mechanism may differ in Mycobacterium species. To investigate this, a putative PNPOx from M. smegmatis, Msmeg_3380, has been cloned. This enzyme has been recombinantly expressed in E. coli and purified to homogeneity. Good-quality crystals of selenomethionine-substituted Msmeg_3380 were obtained by the hanging-drop vapour-diffusion technique and diffracted to 1.2 A using synchrotron radiation.
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16
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Pédelacq JD, Rho BS, Kim CY, Waldo GS, Lekin TP, Segelke BW, Rupp B, Hung LW, Kim SI, Terwilliger TC. Crystal structure of a putative pyridoxine 5′-phosphate oxidase (Rv2607) from Mycobacterium tuberculosis. Proteins 2005; 62:563-9. [PMID: 16374842 DOI: 10.1002/prot.20824] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The three-dimensional structure of Rv2607, a putative pyridoxine 5'-phosphate oxidase (PNPOx) from Mycobacterium tuberculosis, has been determined by X-ray crystallography to 2.5 A resolution. Rv2607 has a core domain similar to known PNPOx structures with a flavin mononucleotide (FMN) cofactor. Electron density for two FMN at the dimer interface is weak despite the bright yellow color of the protein solution and crystal. The shape and size of the putative binding pocket is markedly different from that of members of the PNPOx family, which may indicate some significant changes in the FMN binding mode of this protein relative to members of the family.
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Affiliation(s)
- Jean-Denis Pédelacq
- Bioscience Division, MS M888, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
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17
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Canaan S, Sulzenbacher G, Roig-Zamboni V, Scappuccini-Calvo L, Frassinetti F, Maurin D, Cambillau C, Bourne Y. Crystal structure of the conserved hypothetical protein Rv1155 from Mycobacterium tuberculosis. FEBS Lett 2005; 579:215-21. [PMID: 15620716 DOI: 10.1016/j.febslet.2004.11.069] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2004] [Revised: 11/16/2004] [Accepted: 11/21/2004] [Indexed: 11/27/2022]
Abstract
With the aim of elucidating the biological function of hypothetical proteins unique amongst the Actynomyces sub-group of bacteria, we have solved the crystal structure of the conserved hypothetical protein Rv1155 from Mycobacterium tuberculosis at 1.8 A resolution. Rv1155 is a homodimer both in the crystal structure and in solution and folds into two separate domains consisting of a six-stranded anti-parallel beta-barrel fold flanked by two alpha-helices and a helix-turn-helix domain. Both domains contribute to the formation of two deep clefts at the dimer interface. The overall fold of Rv1155 strikingly resembles that of flavin mononucleotide-binding protein and pyridoxamine 5'-phosphate oxydase, but the architecture of the putative binding pocket is markedly different, consistent with the lack of color of Rv1155 and its inability to bind FMN. Rv1155 thus appears to belong to a group of proteins with stringent conservation of the binding cleft, having evolved towards a new binding function.
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Affiliation(s)
- Stéphane Canaan
- Architecture et Fonction des Macromolécules Biologiques, CNRS UMR-6098, 31 Chemin Joseph Aiguier, F-13402 Marseille Cedex 20, France
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18
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Kang JH, Hong ML, Kim DW, Park J, Kang TC, Won MH, Baek NI, Moon BJ, Choi SY, Kwon OS. Genomic organization, tissue distribution and deletion mutation of human pyridoxine 5'-phosphate oxidase. ACTA ACUST UNITED AC 2004; 271:2452-61. [PMID: 15182361 DOI: 10.1111/j.1432-1033.2004.04175.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We used a combined computer and biochemical approach to characterize human pyridoxine 5'-phosphate oxidase (PNPO). The human PNPO gene is composed of seven exons and six introns, and spans approximately 8 kb. All exon/intron junctions contain the gt/ag consensus splicing site. The absence of TATA-like sequences, the presence of Sp1-binding sites and more importantly, the presence of CpG islands in the regulatory region of the PNPO gene are characteristic features of housekeeping genes. Northern blot analyses showed two species of poly(A)(+) RNA of approximately 2.4 and approximately 3.4 kb at identical intensity, whereas Western blot analysis showed that no protein isoform exists in any of the tissues examined. PCR-based analysis led to the idea that two messages are transcribed from a single copy gene, and that the size difference is due to differential usage of the polyadenylation signal. The major sites of PNPO expression are liver, skeletal muscle and kidneys while a very weak signal was detected in lung. The mRNA master dot-blot for multiple human tissues provided a complete map of the tissue distribution not only for PNPO but also for pyridoxal kinase and pyridoxal phosphatase. The data indicate that mRNA expression of all three enzymes essential for vitamin B(6) metabolism is ubiquitous but is highly regulated at the level of transcription in a tissue-specific manner. In addition, human brain PNPO cDNA was expressed in Escherichia coli, and the roles of both the N- and C-terminal regions were studied by creating sequential truncation mutants. Our results showed that deletion of the N-terminal 56 residues affects neither the binding of coenzyme nor catalytic activity.
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Affiliation(s)
- Jeong Han Kang
- Department of Biochemistry, College of Natural Sciences, Kyungpook National University, Taegu, Korea
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Musayev FN, Di Salvo ML, Ko TP, Schirch V, Safo MK. Structure and properties of recombinant human pyridoxine 5'-phosphate oxidase. Protein Sci 2003; 12:1455-63. [PMID: 12824491 PMCID: PMC2323923 DOI: 10.1110/ps.0356203] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2003] [Revised: 04/04/2003] [Accepted: 04/07/2003] [Indexed: 10/27/2022]
Abstract
Pyridoxine 5'-phosphate oxidase catalyzes the terminal step in the synthesis of pyridoxal 5'-phosphate. The cDNA for the human enzyme has been cloned and expressed in Escherichia coli. The purified human enzyme is a homodimer that exhibits a low catalytic rate constant of approximately 0.2 sec(-1) and K(m) values in the low micromolar range for both pyridoxine 5'phosphate and pyridoxamine 5'-phosphate. Pyridoxal 5'-phosphate is an effective product inhibitor. The three-dimensional fold of the human enzyme is very similar to those of the E. coli and yeast enzymes. The human and E. coli enzymes share 39% sequence identity, but the binding sites for the tightly bound FMN and substrate are highly conserved. As observed with the E. coli enzyme, the human enzyme binds one molecule of pyridoxal 5'-phosphate tightly on each subunit.
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Affiliation(s)
- Faik N Musayev
- Department of Medicinal Chemistry, Institute for Structural Biology and Drug Discovery, Virginia Commonwealth University, 800 E. Leigh Street, Richmond, VA 23219, USA
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di Salvo ML, Safo MK, Musayev FN, Bossa F, Schirch V. Structure and mechanism of Escherichia coli pyridoxine 5'-phosphate oxidase. BIOCHIMICA ET BIOPHYSICA ACTA 2003; 1647:76-82. [PMID: 12686112 DOI: 10.1016/s1570-9639(03)00060-8] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Escherichia coli pyridoxine 5'-phosphate oxidase (PNPOx) catalyzes the oxidation of either pyridoxine 5'-phosphate (PNP) or pyridoxamine 5'-phosphate (PMP), forming pyridoxal 5'-phosphate (PLP). This reaction serves as the terminal step in the de novo biosynthesis of PLP in E. coli and as a part of the salvage pathway of this coenzyme in both E. coli and mammalian cells. Recent studies have shown that in addition to the active site, PNPOx contains a noncatalytic site that binds PLP tightly. The crystal structures of PNPOx with one and two molecules of PLP bound have been determined. In the active site, the PLP pyridine ring is stacked almost parallel against the re-face of the middle ring of flavin mononucleotide (FMN). A large protein conformational change occurs upon binding of PLP. When the protein is soaked with excess PLP an additional molecule of this cofactor is bound about 11 A from the active site. A possible tunnel exists between the two sites. Site mutants were made of all residues at the active site that make interactions with the substrate. Stereospecificity studies showed that the enzyme is specific for removal of the proR hydrogen atom from the prochiral C4' carbon of PMP. The crystal structure and the stereospecificity studies suggest that the pair of electrons on C4' of the substrate are transferred to FMN as a hydride ion.
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Affiliation(s)
- Martino L di Salvo
- Dipartimento di Scienze Biochimiche A. Rossi Fanelli, Università La Sapienza, P.le Aldo Moro 5, 00185, via degli Apuli 9, Rome, Italy.
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21
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di Salvo ML, Ko TP, Musayev FN, Raboni S, Schirch V, Safo MK. Active site structure and stereospecificity of Escherichia coli pyridoxine-5'-phosphate oxidase. J Mol Biol 2002; 315:385-97. [PMID: 11786019 DOI: 10.1006/jmbi.2001.5254] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Pyridoxine-5'-phosphate oxidase catalyzes the oxidation of either the C4' alcohol group or amino group of the two substrates pyridoxine 5'-phosphate and pyridoxamine 5'-phosphate to an aldehyde, forming pyridoxal 5'-phosphate. A hydrogen atom is removed from C4' during the oxidation and a pair of electrons is transferred to tightly bound FMN. A new crystal form of the enzyme in complex with pyridoxal 5'-phosphate shows that the N-terminal segment of the protein folds over the active site to sequester the ligand from solvent during the catalytic cycle. Using (4'R)-[(3)H]PMP as substrate, nearly 100 % of the radiolabel appears in water after oxidation to pyridoxal 5'-phosphate. Thus, the enzyme is specific for removal of the proR hydrogen atom from the prochiral C4' carbon atom of pyridoxamine 5'-phosphate. Site mutants were made of all residues at the active site that interact with the oxygen atom or amine group on C4' of the substrates. Other residues that make interactions with the phosphate moiety of the substrate were mutated. The mutants showed a decrease in affinity, but exhibited considerable catalytic activity, showing that these residues are important for binding, but play a lesser role in catalysis. The exception is Arg197, which is important for both binding and catalysis. The R197 M mutant enzyme catalyzed removal of the proS hydrogen atom from (4'R)-[(3)H]PMP, showing that the guanidinium side-chain plays an important role in determining stereospecificity. The crystal structure and the stereospecificity studies suggests that the pair of electrons on C4' of the substrate are transferred to FMN as a hydride ion.
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Affiliation(s)
- Martino L di Salvo
- A. Rossi Fanelli Dipartimento di Scienze Biochimiche, Centro di Biologia Molecolare del Consiglio Nazionale delle Ricerche, Università La Sapienza, Rome, Italy
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Safo MK, Musayev FN, di Salvo ML, Schirch V. X-ray structure of Escherichia coli pyridoxine 5'-phosphate oxidase complexed with pyridoxal 5'-phosphate at 2.0 A resolution. J Mol Biol 2001; 310:817-26. [PMID: 11453690 DOI: 10.1006/jmbi.2001.4734] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Escherichia coli pyridoxine 5'-phosphate oxidase catalyzes the terminal step in the biosynthesis of pyridoxal 5'-phosphate by the FMN oxidation of pyridoxine 5'-phosphate forming FMNH(2) and H(2)O(2). Recent studies have shown that in addition to the active site, pyridoxine 5'-phosphate oxidase contains a non-catalytic site that binds pyridoxal 5'-phosphate tightly. The crystal structure of pyridoxine 5'-phosphate oxidase from E. coli with one or two molecules of pyridoxal 5'-phosphate bound to each monomer has been determined to 2.0 A resolution. One of the pyridoxal 5'-phosphate molecules is clearly bound at the active site with the aldehyde at C4' of pyridoxal 5'-phosphate near N5 of the bound FMN. A protein conformational change has occurred that partially closes the active site. The orientation of the bound pyridoxal 5'-phosphate suggests that the enzyme catalyzes a hydride ion transfer between C4' of pyridoxal 5'-phosphate and N5 of FMN. When the crystals are soaked with excess pyridoxal 5'-phosphate an additional molecule of this cofactor is also bound about 11 A from the active site. A possible tunnel exists between the two sites so that pyridoxal 5'-phosphate formed at the active site may transfer to the non-catalytic site without passing though the solvent.
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Affiliation(s)
- M K Safo
- Institute for Structural Biology and Drug Discovery, and Department of Biochemistry, Virginia Commonwealth University, Richmond, VA 23219, USA.
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