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Wittmann D, Wang C, Grimm B. More indications for redox-sensitive cysteine residues of the Arabidopsis 5-aminolevulinate dehydratase. FRONTIERS IN PLANT SCIENCE 2024; 14:1294802. [PMID: 38317833 PMCID: PMC10839789 DOI: 10.3389/fpls.2023.1294802] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/15/2023] [Accepted: 12/28/2023] [Indexed: 02/07/2024]
Abstract
Redox-dependent thiol-disulfide switches of cysteine residues are one of the significant posttranslational modifications of proteins to control rapidly their stability, activity, and protein interaction. Redox control also modulates the tetrapyrrole biosynthesis (TBS). Among the redox-dependent TBS enzymes, 5-aminolevulinic acid dehydratase (ALAD) was previously recognized to interact with reductants, such a thioredoxins or NADPH-dependent thioredoxin reductase C. In this report, we aim to verify the redox sensitivity of ALAD and identify the redox-reactive cysteine residues among the six cysteines of the mature protein form Arabidopsis. Based on structural modelling and comparative studies of wild-type ALAD and ALAD mutants with single and double Cys➔Ser substitutions under oxidizing and reducing conditions, we aim to predict the dimerization and oligomerisation of ALAD as well as the crucial Cys residues for disulfide bridge formation and enzyme activity. The Cys404Ser mutation led to a drastic inactivation of ALAD and redox-dependent properties of ALAD were severely impaired, when Cys71 was simultaneously mutated with Cys152 or Cys251. Cys71 is located in a flexible N-terminal arm of ALAD, which could allow intramolecular disulfide bridges with Cys residues at the surface of the remaining globule ALAD structure. As a result, we propose different roles of Cys residues for redox control, catalytic activity and Mg2+-dependent assembly.
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Affiliation(s)
- Daniel Wittmann
- Institute of Biology/Plant Physiology, Humboldt-Universität zu Berlin, Berlin, Germany
| | - Chao Wang
- State Key Laboratory of Crop Stress Adaptation and Improvement, School of Life Sciences, Henan University, Kaifeng, China
| | - Bernhard Grimm
- Institute of Biology/Plant Physiology, Humboldt-Universität zu Berlin, Berlin, Germany
- State Key Laboratory of Crop Stress Adaptation and Improvement, School of Life Sciences, Henan University, Kaifeng, China
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2
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San Juan I, Pereira-Ortuzar T, Cendoya X, Laín A, To-Figueras J, Mateos B, Planes FJ, Bernardo-Seisdedos G, Mato JM, Millet O. ALAD Inhibition by Porphobilinogen Rationalizes the Accumulation of δ-Aminolevulinate in Acute Porphyrias. Biochemistry 2022; 61:2409-2416. [PMID: 36241173 DOI: 10.1021/acs.biochem.2c00434] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Patients with major forms of acute hepatic porphyria present acute neurological attacks with overproduction of porphobilinogen (PBG) and δ-aminolevulinic acid (ALA). Even if ALA is considered the most likely agent inducing the acute symptoms, the mechanism of its accumulation has not been experimentally demonstrated. In the most frequent form, acute intermittent porphyria (AIP), inherited gene mutations induce a deficiency in PBG deaminase; thus, accumulation of the substrate PBG is biochemically obligated but not that of ALA. A similar scenario is observed in other forms of acute hepatic porphyria (i.e., porphyria variegate, VP) in which PBG deaminase is inhibited by metabolic intermediates. Here, we have investigated the molecular basis of δ-aminolevulinate accumulation using in vitro fluxomics monitored by NMR spectroscopy and other biophysical techniques. Our results show that porphobilinogen, the natural product of δ-aminolevulinate deaminase, effectively inhibits its anabolic enzyme at abnormally low concentrations. Structurally, this high affinity can be explained by the interactions that porphobilinogen generates with the active site, most of them shared with the substrate. Enzymatically, our flux analysis of an altered heme pathway demonstrates that a minimum accumulation of porphobilinogen will immediately trigger the accumulation of δ-aminolevulinate, a long-lasting observation in patients suffering from acute porphyrias.
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Affiliation(s)
- Itxaso San Juan
- Precision Medicine and Metabolism Laboratory, CIC bioGUNE, Basque Research and Technology Alliance (BRTA), Bizkaia Science and Technology Park, 48160 Derio, Spain
| | - Tania Pereira-Ortuzar
- Precision Medicine and Metabolism Laboratory, CIC bioGUNE, Basque Research and Technology Alliance (BRTA), Bizkaia Science and Technology Park, 48160 Derio, Spain
| | - Xabier Cendoya
- , Universidad de Navarra, Tecnun Escuela de Ingeniería y Centro de Ingeniería Biomédica, San Sebastián 20009, Spain
| | - Ana Laín
- Precision Medicine and Metabolism Laboratory, CIC bioGUNE, Basque Research and Technology Alliance (BRTA), Bizkaia Science and Technology Park, 48160 Derio, Spain
| | - Jordi To-Figueras
- Biochemistry and Molecular Genetics Unit, Hospital Clinic, IDIBAPS, University of Barcelona, Villarroel 170, 08036 Barcelona, Spain
| | - Borja Mateos
- Precision Medicine and Metabolism Laboratory, CIC bioGUNE, Basque Research and Technology Alliance (BRTA), Bizkaia Science and Technology Park, 48160 Derio, Spain
| | - Francisco J Planes
- , Universidad de Navarra, Tecnun Escuela de Ingeniería y Centro de Ingeniería Biomédica, San Sebastián 20009, Spain.,Universidad de Navarra, DATAI Instituto de Ciencia de los Datos e Inteligencia Artificial, Pamplona 31009, Spain
| | - Ganeko Bernardo-Seisdedos
- Precision Medicine and Metabolism Laboratory, CIC bioGUNE, Basque Research and Technology Alliance (BRTA), Bizkaia Science and Technology Park, 48160 Derio, Spain.,ATLAS Molecular Pharma, Bizkaia Science and Technology Park, 48160 Derio, Spain
| | - José M Mato
- Precision Medicine and Metabolism Laboratory, CIC bioGUNE, Basque Research and Technology Alliance (BRTA), Bizkaia Science and Technology Park, 48160 Derio, Spain.,Biomedical Research Network on Hepatic and Digestive Diseases (CIBEREHD), Instituto de Salud Carlos III, Madrid 28029, Spain
| | - Oscar Millet
- Precision Medicine and Metabolism Laboratory, CIC bioGUNE, Basque Research and Technology Alliance (BRTA), Bizkaia Science and Technology Park, 48160 Derio, Spain.,ATLAS Molecular Pharma, Bizkaia Science and Technology Park, 48160 Derio, Spain.,Biomedical Research Network on Hepatic and Digestive Diseases (CIBEREHD), Instituto de Salud Carlos III, Madrid 28029, Spain
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3
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Azim N, Gardner QA, Rashid N, Akhtar M. Mechanistic studies on Pyrobaculum calidifontis porphobilinogen synthase (5-aminolevulinic acid dehydratase). Bioorg Chem 2019; 91:103117. [PMID: 31377385 DOI: 10.1016/j.bioorg.2019.103117] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2019] [Revised: 07/09/2019] [Accepted: 07/10/2019] [Indexed: 10/26/2022]
Abstract
Porphobilinogen synthase (PBG synthase) gene from Pyrobaculum calidifontis was cloned and expressed in E. coli. The recombinant enzyme was purified as an octamer and was found by mass spectrometry to have a subunit Mr of 37676.59 (calculated, 37676.3). The enzyme showed high thermal stability and retained almost all of its activity after incubation at 70 °C for 16 h in the presence of β-mercaptoethanol (β-ME) and zinc chloride. However, in the absence of the latter the enzyme was inactivated after 16 h although it regained full activity in the presence of β-ME and zinc chloride. The protein contained 4 mol of tightly bound zinc per octamer. Further, 4 mol of low affinity zinc could be incorporated following incubation with exogenous zinc salts. The enzyme was inactivated by incubation with levulinic acid followed by treatment with sodium borohydride. Tryptic digest of the modified enzyme and mass spectrometric analysis showed that Lys257 was the site of modification, which has previously been shown to be the site for the binding of 5-aminolevulinic acid giving rise to the propionate-half of porphobilinogen. P. calidifontis PBG synthase was inactivated by 5-chlorolevulinic acid and the residue modified was shown to be the central cysteine (Cys127) of the zinc-binding cysteine-triad, comprising Cys125, 127, 135. The present results in conjunction with earlier findings on zinc containing PBG synthases, are discussed which advocate that the catalytic role of zinc in the activation of the 5-aminolevulinic acid molecule forming the acetate-half of PBG is possible.
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Affiliation(s)
- Naseema Azim
- School of Biological Sciences, University of the Punjab, New Campus, Lahore 54590, Pakistan
| | | | - Naeem Rashid
- School of Biological Sciences, University of the Punjab, New Campus, Lahore 54590, Pakistan
| | - Muhammad Akhtar
- School of Biological Sciences, University of the Punjab, New Campus, Lahore 54590, Pakistan; Biological Sciences, University of Southampton SO17 1BJ, UK.
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4
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Towards Initial Indications for a Thiol-Based Redox Control of Arabidopsis 5-Aminolevulinic Acid Dehydratase. Antioxidants (Basel) 2018; 7:antiox7110152. [PMID: 30384439 PMCID: PMC6262466 DOI: 10.3390/antiox7110152] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2018] [Revised: 10/26/2018] [Accepted: 10/28/2018] [Indexed: 12/15/2022] Open
Abstract
Thiol-based redox control is one of the important posttranslational mechanisms of the tetrapyrrole biosynthesis pathway. Many enzymes of the pathway have been shown to interact with thioredoxin (TRX) and Nicotinamide adenine dinucleotide phosphate (NADPH)-dependent thioredoxin reductase C (NTRC). We examined the redox-dependency of 5-aminolevulinic acid dehydratase (ALAD), which catalyzed the conjugation of two 5-aminolevulinic acid (ALA) molecules to porphobilinogen. ALAD interacted with TRX f, TRX m and NTRC in chloroplasts. Consequently, less ALAD protein accumulated in the trx f1, ntrc and trx f1/ntrc mutants compared to wild-type control resulting in decreased ALAD activity. In a polyacrylamide gel under non-reducing conditions, ALAD monomers turned out to be present in reduced and two oxidized forms. The reduced and oxidized forms of ALAD differed in their catalytic activity. The addition of TRX stimulated ALAD activity. From our results it was concluded that (i) deficiency of the reducing power mainly affected the in planta stability of ALAD; and (ii) the reduced form of ALAD displayed increased enzymatic activity.
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Mills-Davies N, Butler D, Norton E, Thompson D, Sarwar M, Guo J, Gill R, Azim N, Coker A, Wood SP, Erskine PT, Coates L, Cooper JB, Rashid N, Akhtar M, Shoolingin-Jordan PM. Structural studies of substrate and product complexes of 5-aminolaevulinic acid dehydratase from humans,Escherichia coliand the hyperthermophilePyrobaculum calidifontis. ACTA CRYSTALLOGRAPHICA SECTION D-STRUCTURAL BIOLOGY 2017; 73:9-21. [DOI: 10.1107/s2059798316019525] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2016] [Accepted: 12/06/2016] [Indexed: 11/11/2022]
Abstract
A number of X-ray analyses of an enzyme involved in a key early stage of tetrapyrrole biosynthesis are reported. Two structures of human 5-aminolaevulinate dehydratase (ALAD), native and recombinant, have been determined at 2.8 Å resolution, showing that the enzyme adopts an octameric quaternary structure in accord with previously published analyses of the enzyme from a range of other species. However, this is in contrast to the finding that a disease-related F12L mutant of the human enzyme uniquely forms hexamers [Breiniget al.(2003),Nature Struct. Biol.10, 757–763]. Monomers of all ALADs adopt the TIM-barrel fold; the subunit conformation that assembles into the octamer includes the N-terminal tail of one monomer curled around the (α/β)8barrel of a neighbouring monomer. Both crystal forms of the human enzyme possess two monomers per asymmetric unit, termedAandB. In the native enzyme there are a number of distinct structural differences between theAandBmonomers, with the latter exhibiting greater disorder in a number of loop regions and in the active site. In contrast, the second monomer of the recombinant enzyme appears to be better defined and the active site of both monomers clearly possesses a zinc ion which is bound by three conserved cysteine residues. In native human ALAD, theAmonomer also has a ligand resembling the substrate ALA which is covalently bound by a Schiff base to one of the active-site lysines (Lys252) and is held in place by an ordered active-site loop. In contrast, these features of the active-site structure are disordered or absent in theBsubunit of the native human enzyme. The octameric structure of the zinc-dependent ALAD from the hyperthermophilePyrobaculum calidifontisis also reported at a somewhat lower resolution of 3.5 Å. Finally, the details are presented of a high-resolution structure of theEscherichia coliALAD enzyme co-crystallized with a noncovalently bound moiety of the product, porphobilinogen (PBG). This structure reveals that the pyrrole side-chain amino group is datively bound to the active-site zinc ion and that the PBG carboxylates interact with the enzymeviahydrogen bonds and salt bridges with invariant residues. A number of hydrogen-bond interactions that were previously observed in the structure of yeast ALAD with a cyclic intermediate resembling the product PBG appear to be weaker in the new structure, suggesting that these interactions are only optimal in the transition state.
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Layer G, Reichelt J, Jahn D, Heinz DW. Structure and function of enzymes in heme biosynthesis. Protein Sci 2010; 19:1137-61. [PMID: 20506125 DOI: 10.1002/pro.405] [Citation(s) in RCA: 213] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Tetrapyrroles like hemes, chlorophylls, and cobalamin are complex macrocycles which play essential roles in almost all living organisms. Heme serves as prosthetic group of many proteins involved in fundamental biological processes like respiration, photosynthesis, and the metabolism and transport of oxygen. Further, enzymes such as catalases, peroxidases, or cytochromes P450 rely on heme as essential cofactors. Heme is synthesized in most organisms via a highly conserved biosynthetic route. In humans, defects in heme biosynthesis lead to severe metabolic disorders called porphyrias. The elucidation of the 3D structures for all heme biosynthetic enzymes over the last decade provided new insights into their function and elucidated the structural basis of many known diseases. In terms of structure and function several rather unique proteins were revealed such as the V-shaped glutamyl-tRNA reductase, the dipyrromethane cofactor containing porphobilinogen deaminase, or the "Radical SAM enzyme" coproporphyrinogen III dehydrogenase. This review summarizes the current understanding of the structure-function relationship for all heme biosynthetic enzymes and their potential interactions in the cell.
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Affiliation(s)
- Gunhild Layer
- Institute of Microbiology, Technische Universität Braunschweig, Braunschweig D-38106, Germany
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Lu Q, Ma J, Rong H, Fan J, Yuan Y, Li K, Gao Y, Zhang X, Teng M, Niu L. Cloning, expression, purification, crystallization and preliminary crystallographic analysis of 5-aminolaevulinic acid dehydratase from Bacillus subtilis. Acta Crystallogr Sect F Struct Biol Cryst Commun 2010; 66:1053-5. [PMID: 20823524 PMCID: PMC2935225 DOI: 10.1107/s1744309110027582] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2010] [Accepted: 07/12/2010] [Indexed: 11/10/2022]
Abstract
5-aminolaevulinic acid dehydratase (ALAD), a crucial enzyme in the biosynthesis of tetrapyrrole, catalyses the condensation of two 5-aminolaevulinic acid (ALA) molecules to form porphobilinogen (PBG). The gene encoding ALAD was amplified from genomic DNA of Bacillus subtilis and the protein was overexpressed in Escherichia coli strain BL21 (DE3). The protein was purified and crystallized with an additional MGSSHHHHHHSSGLVPRGSH- tag at the N-terminus of the target protein. Diffraction-quality single crystals were obtained by the hanging-drop vapour-diffusion method. An X-ray diffraction data set was collected at a resolution of 2.7 A.
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Affiliation(s)
- Qianda Lu
- Hefei National Laboratory for Physical Sciences at Microscale and School of Life Sciences, University of Science and Technology of China, 96 Jinzhai Road, Hefei, Anhui 230027, People’s Republic of China
- Key Laboratory of Structural Biology, Chinese Academy of Sciences, 96 Jinzhai Road, Hefei, Anhui 230027, People’s Republic of China
| | - Jinming Ma
- Hefei National Laboratory for Physical Sciences at Microscale and School of Life Sciences, University of Science and Technology of China, 96 Jinzhai Road, Hefei, Anhui 230027, People’s Republic of China
- Key Laboratory of Structural Biology, Chinese Academy of Sciences, 96 Jinzhai Road, Hefei, Anhui 230027, People’s Republic of China
| | - Hui Rong
- Hefei National Laboratory for Physical Sciences at Microscale and School of Life Sciences, University of Science and Technology of China, 96 Jinzhai Road, Hefei, Anhui 230027, People’s Republic of China
- Key Laboratory of Structural Biology, Chinese Academy of Sciences, 96 Jinzhai Road, Hefei, Anhui 230027, People’s Republic of China
| | - Jun Fan
- School of Life Sciences, Anhui Agricultural University, 130 West Changjiang Road, Hefei, Anhui 230036, People’s Republic of China
| | - Ye Yuan
- Hefei National Laboratory for Physical Sciences at Microscale and School of Life Sciences, University of Science and Technology of China, 96 Jinzhai Road, Hefei, Anhui 230027, People’s Republic of China
- Key Laboratory of Structural Biology, Chinese Academy of Sciences, 96 Jinzhai Road, Hefei, Anhui 230027, People’s Republic of China
| | - Kuai Li
- Hefei National Laboratory for Physical Sciences at Microscale and School of Life Sciences, University of Science and Technology of China, 96 Jinzhai Road, Hefei, Anhui 230027, People’s Republic of China
- Key Laboratory of Structural Biology, Chinese Academy of Sciences, 96 Jinzhai Road, Hefei, Anhui 230027, People’s Republic of China
| | - Yongxiang Gao
- Hefei National Laboratory for Physical Sciences at Microscale and School of Life Sciences, University of Science and Technology of China, 96 Jinzhai Road, Hefei, Anhui 230027, People’s Republic of China
- Key Laboratory of Structural Biology, Chinese Academy of Sciences, 96 Jinzhai Road, Hefei, Anhui 230027, People’s Republic of China
| | - Xiao Zhang
- Hefei National Laboratory for Physical Sciences at Microscale and School of Life Sciences, University of Science and Technology of China, 96 Jinzhai Road, Hefei, Anhui 230027, People’s Republic of China
- Key Laboratory of Structural Biology, Chinese Academy of Sciences, 96 Jinzhai Road, Hefei, Anhui 230027, People’s Republic of China
| | - Maikun Teng
- Hefei National Laboratory for Physical Sciences at Microscale and School of Life Sciences, University of Science and Technology of China, 96 Jinzhai Road, Hefei, Anhui 230027, People’s Republic of China
- Key Laboratory of Structural Biology, Chinese Academy of Sciences, 96 Jinzhai Road, Hefei, Anhui 230027, People’s Republic of China
| | - Liwen Niu
- Hefei National Laboratory for Physical Sciences at Microscale and School of Life Sciences, University of Science and Technology of China, 96 Jinzhai Road, Hefei, Anhui 230027, People’s Republic of China
- Key Laboratory of Structural Biology, Chinese Academy of Sciences, 96 Jinzhai Road, Hefei, Anhui 230027, People’s Republic of China
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8
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Li N, Chu X, Liu X, Li D. Probing the active site of rat porphobilinogen synthase using newly developed inhibitors. Bioorg Chem 2008; 37:33-40. [PMID: 19095280 DOI: 10.1016/j.bioorg.2008.11.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2008] [Revised: 10/31/2008] [Accepted: 11/05/2008] [Indexed: 11/24/2022]
Abstract
The structurally related tetrapyrrolic pigments are a group of natural products that participate in many of the fundamental biosynthetic and catabolic processes of living organisms. Porphobilinogen synthase catalyzes a rate-limiting step for the biosyntheses of tetrapyrrolic natural products. In the present study, a variety of new substrate analogs and reaction intermediate analogs were synthesized, which were used as probes for studying the active site of rat porphobilinogen synthase. The compounds 1, 3, 6, 9, 14, 16, and 28 were found to be competitive inhibitors of rat porphobilinogen synthase with inhibition constants ranging from 0.96 to 73.04mM. Compounds 7, 10, 12, 13, 15, 17, 18, and 26 were found to be irreversible enzyme inhibitors. For irreversible inhibitors, loose-binding inhibitors were found to give stronger inactivation. The amino group and carboxyl group of the analogs were found to be important for their binding to the enzyme. This study increased our understanding of the active site of porphobilinogen synthase.
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Affiliation(s)
- Nan Li
- Department of Biology and Chemistry, City University of Hong Kong, Kowloon, SAR, PR China
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Kokona B, Rigotti DJ, Wasson AS, Lawrence SH, Jaffe EK, Fairman R. Probing the oligomeric assemblies of pea porphobilinogen synthase by analytical ultracentrifugation. Biochemistry 2008; 47:10649-56. [PMID: 18795796 DOI: 10.1021/bi801128d] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The enzyme porphobilinogen synthase (PBGS) can exist in different nonadditive homooligomeric assemblies, and under appropriate conditions, the distribution of these assemblies can respond to ligands such as metals or substrate. PBGS from most organisms was believed to be octameric until work on a rare allele of human PBGS revealed an alternate hexameric assembly, which is also available to the wild-type enzyme at elevated pH [Breinig, S., et al. (2003) Nat. Struct. Biol. 10, 757-763]. Herein, we establish that the distribution of pea PBGS quaternary structures also contains octamers and hexamers, using both sedimentation velocity and sedimentation equilibrium experiments. We report results in which the octamer dominates under purification conditions and discuss conditions that influence the octamer:hexamer ratio. As predicted by PBGS crystal structures from related organisms, in the absence of magnesium, the octameric assembly is significantly destabilized, and the oligomeric distribution is dominated largely by the hexameric assembly. Although the PBGS hexamer-to-octamer oligomeric rearrangement is well documented under some conditions, both assemblies are very stable (under AU conditions) in the time frame of our ultracentrifuge experiments.
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Affiliation(s)
- Bashkim Kokona
- Department of Biology, Haverford College, 370 Lancaster Avenue, Haverford, Pennsylvania 19041, USA
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10
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Gacond S, Frère F, Nentwich M, Faurite JP, Frankenberg-Dinkel N, Neier R. Synthesis of Bisubstrate Inhibitors of Porphobilinogen Synthase fromPseudomonas aeruginosa. Chem Biodivers 2007; 4:189-202. [PMID: 17311232 DOI: 10.1002/cbdv.200790024] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Porphobilinogen synthase (PBGS) synthesizes porphobilinogen 2 (PBG), the common precursor of all natural tetrapyrroles, through an asymmetric condensation of two molecules of 5-aminolevulinic acid 1 (ALA). Symmetrically linked dimers 7-11 derived from levulinic acid 3 (gamma-oxovaleric acid) have been synthesized to mimic the assumed bisubstrate bound to the active site of the enzyme. Their inhibition potential was characterized by determination of the IC(50) and K(i) values using PBGS from Pseudomonas aeruginosa. The polarity and the size of the functional group linking the two levulinic acid 3 units have a strong influence on the inhibition behavior.
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Affiliation(s)
- Sabine Gacond
- Institute of Chemistry, University of Neuchâtel, Neuchâtel, Switzerland
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11
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Frère F, Nentwich M, Gacond S, Heinz DW, Neier R, Frankenberg-Dinkel N. Probing the active site of Pseudomonas aeruginosa porphobilinogen synthase using newly developed inhibitors. Biochemistry 2006; 45:8243-53. [PMID: 16819823 DOI: 10.1021/bi052611f] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Porphobilinogen synthase catalyzes the first committed step of the tetrapyrrole biosynthesis pathway. In an aldol-like condensation, two molecules of 5-aminolevulinic acid (ALA) form the first pyrrole, porphobilinogen. Newly synthesized analogues of a reaction intermediate of porphobilinogen synthase have been employed in studying the active site and the catalytic mechanism of this early enzyme of tetrapyrrole biosynthesis. This study combines structural and kinetic evaluation of the inhibition potency of these inhibitors. In addition, one of the determined protein structures provides for the first time structural evidence of a magnesium ion in the active site. From these results, we can corroborate an earlier postulated enzymatic mechanism that starts with formation of a C-C bond, linking C3 of the A-side ALA to C4 of the P-side ALA through an aldole addition. The obtained data are discussed with respect to the current literature.
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Affiliation(s)
- Frederic Frère
- Institute for Microbiology, Technical University Braunschweig, Spielmannstrasse 7, D-38106 Braunschweig, Germany
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