1
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Liu ZC, Wng Q, Zheng Q, Zhao WL, Chen C, Ruan LY, Xu H, Meng HH, Zhao WL, Liu WY, Zhong JG, Luo BZX, Norbu K, Zhou F, Wang JS, Feng X. Acute hepatotoxicity and nephrotoxicity risk assessment of the Tibetan medicine 25 flavors of the turquoise pill based on 1H-NMR metabonomics. JOURNAL OF ETHNOPHARMACOLOGY 2021; 279:113916. [PMID: 33571615 DOI: 10.1016/j.jep.2021.113916] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/04/2020] [Revised: 02/04/2021] [Accepted: 02/05/2021] [Indexed: 06/12/2023]
Abstract
ETHNOPHARMACOLOGICAL RELEVANCE 25 flavors of the turquoise pill, a traditional Tibetan medicine for the treatment of various types of hepatitis, has not been investigated on its safety, especially the component mineral turquoise, which is believed to be essential but worried for its potential toxicity. AIM OF THE STUDY To explore the potential acute toxicity and function of 25 flavors of the turquoise pill and turquoise, the possible mechanism of the effects of turquoise and 25 flavors of the turquoise pill were systematically studied based on 1H NMR metabolomics. MATERIALS AND METHODS The rats were administered with turquoise and 25 flavors of the turquoise pill by gavage for 7 days, and samples of serum, liver, and kidney were collected. The potential toxicity and function of turquoise and 25 flavors of the turquoise pill on the liver and kidney of SD rats were evaluated by 1H NMR metabonomics, histopathology, and biochemical indexes. RESULTS The results demonstrated that 25 flavors of the turquoise pill could scavenge free oxygen radicals, strengthen aerobic respiration and inhibit glycolysis in the liver. It did not cause oxidative stress in the kidney with no obvious damage. By modulation of branched-chain amino acids (BCAAs), 25 flavors of the turquoise pill can improve the utilization of glucose and promote aerobic respiration of the kidney. CONCLUSION Considering the high dosage and short duration used in this study relative to their typical clinical usage, administration of 25 flavors of the turquoise pill and its component mineral turquoise are safe to livers and kidneys.
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Affiliation(s)
- Zhi-Chao Liu
- Center of Molecular Metabolism, Nanjing University of Science and Technology, 200 Xiaolingwei Street, Nanjing, 210094, China
| | - Qian Wng
- Beijing Hospital of Tibetan Medicine, China Tibetology Research Center, Beijing, 100029, China
| | - Qi Zheng
- Center of Molecular Metabolism, Nanjing University of Science and Technology, 200 Xiaolingwei Street, Nanjing, 210094, China
| | - Wen-Li Zhao
- Center of Molecular Metabolism, Nanjing University of Science and Technology, 200 Xiaolingwei Street, Nanjing, 210094, China
| | - Cheng Chen
- Center of Molecular Metabolism, Nanjing University of Science and Technology, 200 Xiaolingwei Street, Nanjing, 210094, China
| | - Ling-Yu Ruan
- Center of Molecular Metabolism, Nanjing University of Science and Technology, 200 Xiaolingwei Street, Nanjing, 210094, China
| | - Han Xu
- Center of Molecular Metabolism, Nanjing University of Science and Technology, 200 Xiaolingwei Street, Nanjing, 210094, China
| | - Hui-Hui Meng
- Center of Molecular Metabolism, Nanjing University of Science and Technology, 200 Xiaolingwei Street, Nanjing, 210094, China
| | - Wen-Long Zhao
- Center of Molecular Metabolism, Nanjing University of Science and Technology, 200 Xiaolingwei Street, Nanjing, 210094, China
| | - Wen-Ya Liu
- Center of Molecular Metabolism, Nanjing University of Science and Technology, 200 Xiaolingwei Street, Nanjing, 210094, China
| | - Jia-Ge Zhong
- Beijing Hospital of Tibetan Medicine, China Tibetology Research Center, Beijing, 100029, China
| | - Bu-Zha-Xi Luo
- Beijing Hospital of Tibetan Medicine, China Tibetology Research Center, Beijing, 100029, China
| | - Kelsang Norbu
- Tibet Ganlu Tibetan Medicine Co., Ltd, Lhasa, 851400, China
| | - Feng Zhou
- Tibet Ganlu Tibetan Medicine Co., Ltd, Lhasa, 851400, China
| | - Jun-Song Wang
- Center of Molecular Metabolism, Nanjing University of Science and Technology, 200 Xiaolingwei Street, Nanjing, 210094, China.
| | - Xin Feng
- Beijing Hospital of Tibetan Medicine, China Tibetology Research Center, Beijing, 100029, China.
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2
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Arturo EC, Merkel GW, Hansen MR, Lisowski S, Almeida D, Gupta K, Jaffe EK. Manipulation of a cation-π sandwich reveals conformational flexibility in phenylalanine hydroxylase. Biochimie 2021; 183:63-77. [PMID: 33221376 PMCID: PMC9856217 DOI: 10.1016/j.biochi.2020.11.011] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2020] [Revised: 11/04/2020] [Accepted: 11/10/2020] [Indexed: 01/24/2023]
Abstract
Phenylalanine hydroxylase (PAH) is an allosteric enzyme that maintains phenylalanine (Phe) below neurotoxic levels; its failure results in phenylketonuria, an inborn error of amino acid metabolism. Wild type (WT) PAH equilibrates among resting-state (RS-PAH) and activated (A-PAH) conformations, whose equilibrium position depends upon allosteric Phe binding. The RS-PAH conformation of WT rat PAH (rPAH) contains a cation-π sandwich involving Phe80 that cannot exist in the A-PAH conformation. Phe80 variants F80A, F80D, F80L, and F80R were prepared and evaluated using native PAGE, size exclusion chromatography, ion exchange behavior, intrinsic protein fluorescence, enzyme kinetics, and limited proteolysis, each as a function of [Phe]. Like WT rPAH, F80A and F80D show allosteric activation by Phe while F80L and F80R are constitutively active. Maximal activity of all variants suggests relief of a rate-determining conformational change. Limited proteolysis of WT rPAH (minus Phe) reveals facile cleavage within a 4-helix bundle that is buried in the RS-PAH tetramer interface, reflecting dynamic dissociation of that tetramer. This cleavage is not seen for the Phe80 variants, which all show proteolytic hypersensitivity in a linker that repositions during the RS-PAH to A-PAH interchange. Hypersensitivity is corrected by addition of Phe such that all variants become like WT rPAH and achieve the A-PAH conformation. Thus, manipulation of Phe80 perturbs the conformational space sampled by PAH, increasing sampling of on-pathway intermediates in the RS-PAH and A-PAH interchange. The behavior of the Phe80 variants mimics that of disease-associated R68S and suggests a molecular basis for proteolytic susceptibility in PKU-associated human PAH variants.
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Affiliation(s)
- Emilia C. Arturo
- Molecular Therapeutics Program, Fox Chase Cancer Center, Philadelphia, Pennsylvania, 10111,Department of Biochemistry and Molecular Biology, Drexel University College of Medicine, Philadelphia, PA 19102
| | - George W. Merkel
- Molecular Therapeutics Program, Fox Chase Cancer Center, Philadelphia, Pennsylvania, 10111
| | - Michael R. Hansen
- Molecular Therapeutics Program, Fox Chase Cancer Center, Philadelphia, Pennsylvania, 10111
| | - Sophia Lisowski
- Molecular Therapeutics Program, Fox Chase Cancer Center, Philadelphia, Pennsylvania, 10111
| | - Deeanne Almeida
- Molecular Therapeutics Program, Fox Chase Cancer Center, Philadelphia, Pennsylvania, 10111
| | - Kushol Gupta
- Department pf Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104
| | - Eileen K. Jaffe
- Molecular Therapeutics Program, Fox Chase Cancer Center, Philadelphia, Pennsylvania, 10111,To whom correspondence should be addressed: Eileen K. Jaffe: Molecular Therapeutics, Fox Chase Cancer Center, Philadelphia, PA 19111; ; Tel.(215) 728-3695; Fax. (215) 728-2412
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3
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Potential hepatoxicity risk of the shell of Herpetospermum caudigerum Wall in rats based on 1H-NMR metabonomics. J Pharm Biomed Anal 2019; 176:112800. [DOI: 10.1016/j.jpba.2019.112800] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2019] [Revised: 07/09/2019] [Accepted: 07/31/2019] [Indexed: 12/19/2022]
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4
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Tomé CS, Lopes RR, Sousa PMF, Amaro MP, Leandro J, Mertens HDT, Leandro P, Vicente JB. Structure of full-length wild-type human phenylalanine hydroxylase by small angle X-ray scattering reveals substrate-induced conformational stability. Sci Rep 2019; 9:13615. [PMID: 31541188 PMCID: PMC6754429 DOI: 10.1038/s41598-019-49944-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2019] [Accepted: 09/03/2019] [Indexed: 01/30/2023] Open
Abstract
Human phenylalanine hydroxylase (hPAH) hydroxylates L-phenylalanine (L-Phe) to L-tyrosine, a precursor for neurotransmitter biosynthesis. Phenylketonuria (PKU), caused by mutations in PAH that impair PAH function, leads to neurological impairment when untreated. Understanding the hPAH structural and regulatory properties is essential to outline PKU pathophysiological mechanisms. Each hPAH monomer comprises an N-terminal regulatory, a central catalytic and a C-terminal oligomerisation domain. To maintain physiological L-Phe levels, hPAH employs complex regulatory mechanisms. Resting PAH adopts an auto-inhibited conformation where regulatory domains block access to the active site. L-Phe-mediated allosteric activation induces a repositioning of the regulatory domains. Since a structure of activated wild-type hPAH is lacking, we addressed hPAH L-Phe-mediated conformational changes and report the first solution structure of the allosterically activated state. Our solution structures obtained by small-angle X-ray scattering support a tetramer with distorted P222 symmetry, where catalytic and oligomerisation domains form a core from which regulatory domains protrude, positioning themselves close to the active site entrance in the absence of L-Phe. Binding of L-Phe induces a large movement and dimerisation of regulatory domains, exposing the active site. Activated hPAH is more resistant to proteolytic cleavage and thermal denaturation, suggesting that the association of regulatory domains stabilises hPAH.
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Affiliation(s)
- Catarina S Tomé
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Oeiras, Portugal
- Instituto de Biologia Experimental e Tecnológica, Oeiras, Portugal
| | - Raquel R Lopes
- Research Institute for Medicines (iMed.ULisboa) and Department of Biochemistry and Human Biology, Faculty of Pharmacy, Universidade de Lisboa, Lisbon, Portugal
| | - Pedro M F Sousa
- Instituto de Biologia Experimental e Tecnológica, Oeiras, Portugal
| | - Mariana P Amaro
- Research Institute for Medicines (iMed.ULisboa) and Department of Biochemistry and Human Biology, Faculty of Pharmacy, Universidade de Lisboa, Lisbon, Portugal
- Department of Genetics and Genomic Sciences and Icahn Institute for Data Science and Genomic Technology, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - João Leandro
- Research Institute for Medicines (iMed.ULisboa) and Department of Biochemistry and Human Biology, Faculty of Pharmacy, Universidade de Lisboa, Lisbon, Portugal
- Department of Genetics and Genomic Sciences and Icahn Institute for Data Science and Genomic Technology, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | | | - Paula Leandro
- Research Institute for Medicines (iMed.ULisboa) and Department of Biochemistry and Human Biology, Faculty of Pharmacy, Universidade de Lisboa, Lisbon, Portugal.
| | - João B Vicente
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Oeiras, Portugal.
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5
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Arturo EC, Gupta K, Hansen MR, Borne E, Jaffe EK. Biophysical characterization of full-length human phenylalanine hydroxylase provides a deeper understanding of its quaternary structure equilibrium. J Biol Chem 2019; 294:10131-10145. [PMID: 31076506 PMCID: PMC6664189 DOI: 10.1074/jbc.ra119.008294] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2019] [Revised: 05/09/2019] [Indexed: 11/06/2022] Open
Abstract
Dysfunction of human phenylalanine hydroxylase (hPAH, EC 1.14.16.1) is the primary cause of phenylketonuria, the most common inborn error of amino acid metabolism. The dynamic domain rearrangements of this multimeric protein have thwarted structural study of the full-length form for decades, until now. In this study, a tractable C29S variant of hPAH (C29S) yielded a 3.06 Å resolution crystal structure of the tetrameric resting-state conformation. We used size-exclusion chromatography in line with small-angle X-ray scattering (SEC-SAXS) to analyze the full-length hPAH solution structure both in the presence and absence of Phe, which serves as both substrate and allosteric activators. Allosteric Phe binding favors accumulation of an activated PAH tetramer conformation, which is biophysically distinct in solution. Protein characterization with enzyme kinetics and intrinsic fluorescence revealed that the C29S variant and hPAH are otherwise equivalent in their response to Phe, further supported by their behavior on various chromatography resins and by analytical ultracentrifugation. Modeling of resting-state and activated forms of C29S against SAXS data with available structural data created and evaluated several new models for the transition between the architecturally distinct conformations of PAH and highlighted unique intra- and inter-subunit interactions. Three best-fitting alternative models all placed the allosteric Phe-binding module 8-10 Å farther from the tetramer center than do all previous models. The structural insights into allosteric activation of hPAH reported here may help inform ongoing efforts to treat phenylketonuria with novel therapeutic approaches.
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Affiliation(s)
- Emilia C Arturo
- From the Molecular Therapeutics Program, Fox Chase Cancer Center, Temple University Health Systems, Philadelphia, Pennsylvania 19111
- the Department of Biochemistry and Molecular Biology, Drexel University College of Medicine, Philadelphia, Pennsylvania 19102, and
| | - Kushol Gupta
- the Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104
| | - Michael R Hansen
- From the Molecular Therapeutics Program, Fox Chase Cancer Center, Temple University Health Systems, Philadelphia, Pennsylvania 19111
| | - Elias Borne
- From the Molecular Therapeutics Program, Fox Chase Cancer Center, Temple University Health Systems, Philadelphia, Pennsylvania 19111
| | - Eileen K Jaffe
- From the Molecular Therapeutics Program, Fox Chase Cancer Center, Temple University Health Systems, Philadelphia, Pennsylvania 19111,
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6
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Jaffe EK. New protein structures provide an updated understanding of phenylketonuria. Mol Genet Metab 2017; 121:289-296. [PMID: 28645531 PMCID: PMC5549558 DOI: 10.1016/j.ymgme.2017.06.005] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/07/2017] [Accepted: 06/08/2017] [Indexed: 11/16/2022]
Abstract
Phenylketonuria (PKU) and less severe hyperphenylalaninemia (HPA) constitute the most common inborn error of amino acid metabolism, and is most often caused by defects in phenylalanine hydroxylase (PAH) function resulting in accumulation of Phe to neurotoxic levels. Despite the success of dietary intervention in preventing permanent neurological damage, individuals living with PKU clamor for additional non-dietary therapies. The bulk of disease-associated mutations are PAH missense variants, which occur throughout the entire 452 amino acid human PAH protein. While some disease-associated mutations affect protein structure (e.g. truncations) and others encode catalytically dead variants, most have been viewed as defective in protein folding/stability. Here we refine this view to address how PKU-associated missense variants can perturb the equilibrium among alternate native PAH structures (resting-state PAH and activated PAH), thus shifting the tipping point of this equilibrium to a neurotoxic Phe concentration. This refined view of PKU introduces opportunities for the design or discovery of therapeutic pharmacological chaperones that can help restore the tipping point to healthy Phe levels and how such a therapeutic might work with or without the inhibitory pharmacological chaperone BH4. Dysregulation of an equilibrium of architecturally distinct native PAH structures departs from the concept of "misfolding", provides an updated understanding of PKU, and presents an enhanced foundation for understanding genotype/phenotype relationships.
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Affiliation(s)
- Eileen K Jaffe
- Fox Chase Cancer Center - Temple University Health System, 333 Cottman Ave, Philadelphia, PA 19111, USA.
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7
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Abstract
X-ray scattering is uniquely suited to the study of disordered systems and thus has the potential to provide insight into dynamic processes where diffraction methods fail. In particular, while X-ray crystallography has been a staple of structural biology for more than half a century and will continue to remain so, a major limitation of this technique has been the lack of dynamic information. Solution X-ray scattering has become an invaluable tool in structural and mechanistic studies of biological macromolecules where large conformational changes are involved. Such systems include allosteric enzymes that play key roles in directing metabolic fluxes of biochemical pathways, as well as large, assembly-line type enzymes that synthesize secondary metabolites with pharmaceutical applications. Furthermore, crystallography has the potential to provide information on protein dynamics via the diffuse scattering patterns that are overlaid with Bragg diffraction. Historically, these patterns have been very difficult to interpret, but recent advances in X-ray detection have led to a renewed interest in diffuse scattering analysis as a way to probe correlated motions. Here, we will review X-ray scattering theory and highlight recent advances in scattering-based investigations of protein solutions and crystals, with a particular focus on complex enzymes.
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Affiliation(s)
- Steve P Meisburger
- Department of Chemistry, Princeton University , Princeton, New Jersey 08544, United States
| | - William C Thomas
- Department of Chemistry, Princeton University , Princeton, New Jersey 08544, United States
| | - Maxwell B Watkins
- Department of Chemistry, Princeton University , Princeton, New Jersey 08544, United States
| | - Nozomi Ando
- Department of Chemistry, Princeton University , Princeton, New Jersey 08544, United States
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8
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Tidemand KD, Christensen HEM, Hoeck N, Harris P, Boesen J, Peters GH. Stabilization of tryptophan hydroxylase 2 by l-phenylalanine-induced dimerization. FEBS Open Bio 2016; 6:987-999. [PMID: 27761358 PMCID: PMC5055035 DOI: 10.1002/2211-5463.12100] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2016] [Revised: 06/20/2016] [Accepted: 06/29/2016] [Indexed: 12/12/2022] Open
Abstract
Tryptophan hydroxylase 2 (TPH2) catalyses the initial and rate‐limiting step in the biosynthesis of serotonin, which is associated with a variety of disorders such as depression, obsessive compulsive disorder, and schizophrenia. Full‐length TPH2 is poorly characterized due to low purification quantities caused by its inherent instability. Three truncated variants of human TPH2 (rchTPH2; regulatory and catalytic domain, NΔ47‐rchTPH2; truncation of 47 residues in the N terminus of rchTPH2, and chTPH2; catalytic domain) were expressed, purified, and examined for changes in transition temperature, inactivation rate, and oligomeric state. chTPH2 displayed 14‐ and 11‐fold higher half‐lives compared to rchTPH2 and NΔ47‐rchTPH2, respectively. Differential scanning calorimetry experiments demonstrated that this is caused by premature unfolding of the less stable regulatory domain. By differential scanning fluorimetry, the unfolding transitions of rchTPH2 and NΔ47‐rchTPH2 are found to shift from polyphasic to apparent two‐state by the addition of l‐Trp or l‐Phe. Analytical gel filtration revealed that rchTPH2 and NΔ47‐rchTPH2 reside in a monomer–dimer equilibrium which is significantly shifted toward dimer in the presence of l‐Phe. The dimerizing effect induced by l‐Phe is accompanied by a stabilizing effect, which resulted in a threefold increase in half‐lives of rchTPH2 and NΔ47‐rchTPH2. Addition of l‐Phe to the purification buffer significantly increases the purification yields, which will facilitate characterization of hTPH2.
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Affiliation(s)
- Kasper D Tidemand
- Department of Chemistry Technical University of Denmark Kongens Lyngby Denmark
| | | | - Niclas Hoeck
- Department of Chemistry Technical University of Denmark Kongens Lyngby Denmark
| | - Pernille Harris
- Department of Chemistry Technical University of Denmark Kongens Lyngby Denmark
| | - Jane Boesen
- Department of Chemistry Technical University of Denmark Kongens Lyngby Denmark
| | - Günther H Peters
- Department of Chemistry Technical University of Denmark Kongens Lyngby Denmark
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9
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Becher I, Werner T, Doce C, Zaal EA, Tögel I, Khan CA, Rueger A, Muelbaier M, Salzer E, Berkers CR, Fitzpatrick PF, Bantscheff M, Savitski MM. Thermal profiling reveals phenylalanine hydroxylase as an off-target of panobinostat. Nat Chem Biol 2016; 12:908-910. [DOI: 10.1038/nchembio.2185] [Citation(s) in RCA: 133] [Impact Index Per Article: 16.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2016] [Accepted: 07/20/2016] [Indexed: 02/07/2023]
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10
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Neira JL, Hornos F, Bacarizo J, Cámara-Artigás A, Gómez J. The Monomeric Species of the Regulatory Domain of Tyrosine Hydroxylase Has a Low Conformational Stability. Biochemistry 2016; 55:3418-31. [PMID: 27224548 DOI: 10.1021/acs.biochem.6b00135] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Tyrosine hydroxylase (TyrH) catalyzes the hydroxylation of tyrosine to form 3,4-dihydroxyphenylalanine, the first step in the synthesis of catecholamine neurotransmitters. The protein contains a 159-residue regulatory domain (RD) at its N-terminus that forms dimers in solution; the N-terminal region of RDTyrH (residues 1-71) is absent in the solution structure of the domain. We have characterized the conformational stability of two species of RDTyrH (one containing the N-terminal region and another lacking the first 64 residues) to clarify how that N-terminal region modulates the conformational stability of RD. Under the conditions used in this study, the RD species lacking the first 64 residues is a monomer at pH 7.0, with a small conformational stability at 25 °C (4.7 ± 0.8 kcal mol(-1)). On the other hand, the entire RDTyrH is dimeric at physiological pH, with an estimated dissociation constant of 1.6 μM, as determined by zonal gel filtration chromatography; dimer dissociation was spectroscopically silent to circular dichroism but not to fluoresecence. Both RD species were disordered below physiological pH, but the acquisition of secondary native-like structure occurs at pHs lower than those measured for the attainment of tertiary native- and compactness-like arrangements.
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Affiliation(s)
- José L Neira
- Instituto de Biología Molecular y Celular, Universidad Miguel Hernández , 03202 Elche (Alicante), Spain.,Biocomputation and Complex Systems Physics Institute , 50009 Zaragoza, Spain
| | - Felipe Hornos
- Instituto de Biología Molecular y Celular, Universidad Miguel Hernández , 03202 Elche (Alicante), Spain
| | - Julio Bacarizo
- Department of Physical Chemistry, Biochemistry and Inorganic Chemistry, University of Almería , Agrifood Campus of International Excellence (ceiA3), Almería, Spain
| | - Ana Cámara-Artigás
- Department of Physical Chemistry, Biochemistry and Inorganic Chemistry, University of Almería , Agrifood Campus of International Excellence (ceiA3), Almería, Spain
| | - Javier Gómez
- Instituto de Biología Molecular y Celular, Universidad Miguel Hernández , 03202 Elche (Alicante), Spain
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11
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Abstract
More than 950 phenylalanine hydroxylase (PAH) gene variants have been identified in people with phenylketonuria (PKU). These vary in their consequences for the residual level of PAH activity, from having little or no effect to abolishing PAH activity completely. Advances in genotyping technology and the availability of locus-specific and genotype databases have greatly expanded our understanding of the correlations between individual gene variant, residual PAH activity, tetrahydrobiopterin (BH4 ) responsiveness, and the clinical PKU phenotype. Most patients (∼76%) have compound heterozygous PAH gene variants and one mutated allele may markedly influence the activity of the second mutated allele, which in turn may influence either positively or negatively the activity of the biologically active heterotetrameric form of the PAH. While it is possible to predict the level of BH4 responsiveness (∼71%) and PKU severity (∼78%) from the nature of the underlying gene variants, these relationships remain complex and incompletely understood. A greater understanding of these relationships may increase the potential for individualized management of PKU in future. Inherited deficiencies in BH4 metabolism account for about 1%-2% of all hyperphenylalaninemias and are clinically more severe than PKU. Almost 90% of all patients are deficient in 6-pyruvoyl-tetrahydropterin synthase and dihydropteridine reductase.
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Affiliation(s)
- Nenad Blau
- Dietmar-Hopp-Metabolic Center, University Children's Hospital, Heidelberg, Germany
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12
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Meisburger SP, Taylor AB, Khan CA, Zhang S, Fitzpatrick PF, Ando N. Domain Movements upon Activation of Phenylalanine Hydroxylase Characterized by Crystallography and Chromatography-Coupled Small-Angle X-ray Scattering. J Am Chem Soc 2016; 138:6506-16. [PMID: 27145334 PMCID: PMC4896396 DOI: 10.1021/jacs.6b01563] [Citation(s) in RCA: 82] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Mammalian phenylalanine hydroxylase (PheH) is an allosteric enzyme that catalyzes the first step in the catabolism of the amino acid phenylalanine. Following allosteric activation by high phenylalanine levels, the enzyme catalyzes the pterin-dependent conversion of phenylalanine to tyrosine. Inability to control elevated phenylalanine levels in the blood leads to increased risk of mental disabilities commonly associated with the inherited metabolic disorder, phenylketonuria. Although extensively studied, structural changes associated with allosteric activation in mammalian PheH have been elusive. Here, we examine the complex allosteric mechanisms of rat PheH using X-ray crystallography, isothermal titration calorimetry (ITC), and small-angle X-ray scattering (SAXS). We describe crystal structures of the preactivated state of the PheH tetramer depicting the regulatory domains docked against the catalytic domains and preventing substrate binding. Using SAXS, we further describe the domain movements involved in allosteric activation of PheH in solution and present the first demonstration of chromatography-coupled SAXS with Evolving Factor Analysis (EFA), a powerful method for separating scattering components in a model-independent way. Together, these results support a model for allostery in PheH in which phenylalanine stabilizes the dimerization of the regulatory domains and exposes the active site for substrate binding and other structural changes needed for activity.
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Affiliation(s)
- Steve P. Meisburger
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, USA
| | - Alexander B. Taylor
- Department of Biochemistry, University of Texas Health Science Center, San Antonio, Texas 78229, USA
| | - Crystal A. Khan
- Department of Biochemistry, University of Texas Health Science Center, San Antonio, Texas 78229, USA
| | - Shengnan Zhang
- Department of Biochemistry, University of Texas Health Science Center, San Antonio, Texas 78229, USA
| | - Paul F. Fitzpatrick
- Department of Biochemistry, University of Texas Health Science Center, San Antonio, Texas 78229, USA
| | - Nozomi Ando
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, USA
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13
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Zhang S, Fitzpatrick PF. Identification of the Allosteric Site for Phenylalanine in Rat Phenylalanine Hydroxylase. J Biol Chem 2016; 291:7418-25. [PMID: 26823465 DOI: 10.1074/jbc.m115.709998] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2015] [Indexed: 11/06/2022] Open
Abstract
Liver phenylalanine hydroxylase (PheH) is an allosteric enzyme that requires activation by phenylalanine for full activity. The location of the allosteric site for phenylalanine has not been established. NMR spectroscopy of the isolated regulatory domain (RDPheH(25-117) is the regulatory domain of PheH lacking residues 1-24) of the rat enzyme in the presence of phenylalanine is consistent with formation of a side-by-side ACT dimer. Six residues in RDPheH(25-117) were identified as being in the phenylalanine-binding site on the basis of intermolecular NOEs between unlabeled phenylalanine and isotopically labeled protein. The location of these residues is consistent with two allosteric sites per dimer, with each site containing residues from both monomers. Site-specific variants of five of the residues (E44Q, A47G, L48V, L62V, and H64N) decreased the affinity of RDPheH(25-117) for phenylalanine based on the ability to stabilize the dimer. Incorporation of the A47G, L48V, and H64N mutations into the intact protein increased the concentration of phenylalanine required for activation. The results identify the location of the allosteric site as the interface of the regulatory domain dimer formed in activated PheH.
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Affiliation(s)
- Shengnan Zhang
- From the Department of Biochemistry, University of Texas Health Science Center, San Antonio, Texas 78229
| | - Paul F Fitzpatrick
- From the Department of Biochemistry, University of Texas Health Science Center, San Antonio, Texas 78229
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