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Heidinger L, Perez K, Spatzal T, Einsle O, Weber S, Rees DC, Schleicher E. Analysis of early intermediate states of the nitrogenase reaction by regularization of EPR spectra. Nat Commun 2024; 15:4041. [PMID: 38740794 DOI: 10.1038/s41467-024-48271-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2023] [Accepted: 04/25/2024] [Indexed: 05/16/2024] Open
Abstract
Due to the complexity of the catalytic FeMo cofactor site in nitrogenases that mediates the reduction of molecular nitrogen to ammonium, mechanistic details of this reaction remain under debate. In this study, selenium- and sulfur-incorporated FeMo cofactors of the catalytic MoFe protein component from Azotobacter vinelandii are prepared under turnover conditions and investigated by using different EPR methods. Complex signal patterns are observed in the continuous wave EPR spectra of selenium-incorporated samples, which are analyzed by Tikhonov regularization, a method that has not yet been applied to high spin systems of transition metal cofactors, and by an already established grid-of-error approach. Both methods yield similar probability distributions that reveal the presence of at least four other species with different electronic structures in addition to the ground state E0. Two of these species were preliminary assigned to hydrogenated E2 states. In addition, advanced pulsed-EPR experiments are utilized to verify the incorporation of sulfur and selenium into the FeMo cofactor, and to assign hyperfine couplings of 33S and 77Se that directly couple to the FeMo cluster. With this analysis, we report selenium incorporation under turnover conditions as a straightforward approach to stabilize and analyze early intermediate states of the FeMo cofactor.
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Affiliation(s)
- Lorenz Heidinger
- Institut für Physikalische Chemie, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany
- Institut für Biochemie, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany
| | - Kathryn Perez
- Howard Hughes Medical Institute (HHMI), California Institute of Technology, Division of Chemistry and Chemical Engineering, Pasadena, CA, USA
| | - Thomas Spatzal
- Howard Hughes Medical Institute (HHMI), California Institute of Technology, Division of Chemistry and Chemical Engineering, Pasadena, CA, USA
| | - Oliver Einsle
- Institut für Biochemie, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany
| | - Stefan Weber
- Institut für Physikalische Chemie, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany
| | - Douglas C Rees
- Howard Hughes Medical Institute (HHMI), California Institute of Technology, Division of Chemistry and Chemical Engineering, Pasadena, CA, USA.
| | - Erik Schleicher
- Institut für Physikalische Chemie, Albert-Ludwigs-Universität Freiburg, Freiburg, Germany.
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Martin CB, Taabazuing CY, Knapp MJ. Dynamic Domain Links Substrate Binding and Catalysis in the Factor-Inhibiting-HIF-1. Biochemistry 2023; 62:2442-2449. [PMID: 37526986 DOI: 10.1021/acs.biochem.3c00231] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/03/2023]
Abstract
The interplay between active-site chemistry and functionally relevant enzyme motions can provide useful insights into selective enzyme modulation. Modulation of the hypoxia-sensing function of factor-inhibiting-HIF-1 (FIH) enzyme is a potential therapeutic strategy in disease states such as ischemia and cancer. The hypoxia-sensing function of FIH relies in major part on the tight coupling of the first half of the catalytic mechanism which involves O2 activation and eventual succinate production to the second half which involves HIF-1α/CTAD substrate hydroxylation. In this study, we demonstrate the role of a loop hinge domain in FIH (FIH102-118) called the 100s loop in maintaining this particular tight coupling. Molecular dynamics patterns from Gaussian Network Model (iGNM) database analysis of FIH identified the 100s loop as one dynamic domain containing a hinge residue (Tyr102) with a potential substrate positioning role. Enzymological and biophysical studies of the 100s loop point mutants revealed altered enzyme kinetics with the exception of the conservative FIH mutant Y102F, which suggests a sterics-related role for this residue. Removal of the bulk of Tyr102 (Y102A) resulted in succinate production, autohydroxylation, and an O2 binding environment comparable to wild-type FIH. However, the HIF-1α/CTAD substrate hydroxylation of this mutant was significantly reduced which implies that (1) the FIH loop hinge residue Tyr102 does not affect O2 activation, (2) the stacking steric interaction of Tyr102 is important in substrate positioning for productive hydroxylation, and (3) Tyr102 is important for the synchronization of O2 activation and substrate hydroxylation.
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Affiliation(s)
- Cristina B Martin
- Department of Chemistry, University of Massachusetts, Amherst, Massachusetts 01003, United States
| | - Cornelius Y Taabazuing
- Department of Chemistry, University of Massachusetts, Amherst, Massachusetts 01003, United States
| | - Michael J Knapp
- Department of Chemistry, University of Massachusetts, Amherst, Massachusetts 01003, United States
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3
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Mingroni MA, Chaplin Momaney V, Barlow AN, Jaen Maisonet I, Knapp MJ. Measurement of kinetic isotope effects on peptide hydroxylation using MALDI-MS. Methods Enzymol 2022; 679:363-380. [PMID: 36682871 DOI: 10.1016/bs.mie.2022.08.019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Primary kinetic isotope effects (KIEs) provide unique insight into enzymatic reactions, as they can reveal rate-limiting steps and detailed chemical mechanisms. HIF hydroxylases, part of a family of 2-oxoglutarate (2OG) oxygenases are central to the regulation of many crucial biological processes through O2-sensing, but present a challenge to monitor due to the large size of the protein substrate and the similarity between native and hydroxylated substrate. MALDI-TOF MS is a convenient tool to measure peptide masses, which can also be used to measure the discontinuous kinetics of peptide hydroxylation for Factor Inhibiting HIF (FIH). Using this technique, rate data can be observed from the mole-fraction of CTAD and CTAD-OH in small volumes, allowing noncompetitive H/D KIEs to be measured. Slow dCTAD substrate leads to extensive uncoupling of O2 consumption from peptide hydroxylation, leading to enzyme autohydroxylation, which is observed using UV-vis spectroscopy. Simultaneously measuring both the normal product, CTAD-OH, and the uncoupled product, autohydroxylated enzyme, the KIE on the microscopic step of hydrogen atom transfer (HAT) can be estimated. MALDI-MS analysis is a strong method for monitoring reactions that hydroxylate peptides, and can be generalized to other similar reactions, and simultaneous kinetic detection of branched products can provide valuable insight on microscopic KIEs at intermediate mechanistic steps.
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Affiliation(s)
- Michael A Mingroni
- Department of Chemistry, University of Massachusetts, Amherst, MA, United States
| | | | - Alexandra N Barlow
- Department of Chemistry, University of Massachusetts, Amherst, MA, United States
| | | | - Michael J Knapp
- Department of Chemistry, University of Massachusetts, Amherst, MA, United States.
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Yan H, Xie Y, Liu Y, Yuan L, Sheng R. ComABAN: refining molecular representation with the graph attention mechanism to accelerate drug discovery. Brief Bioinform 2022; 23:6674166. [PMID: 35998925 DOI: 10.1093/bib/bbac350] [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: 01/17/2022] [Revised: 07/16/2022] [Accepted: 07/27/2022] [Indexed: 11/14/2022] Open
Abstract
An unsolved challenge in developing molecular representation is determining an optimal method to characterize the molecular structure. Comprehension of intramolecular interactions is paramount toward achieving this goal. In this study, ComABAN, a new graph-attention-based approach, is proposed to improve the accuracy of molecular representation by simultaneously considering atom-atom, bond-bond and atom-bond interactions. In addition, we benchmark models extensively on 8 public and 680 proprietary industrial datasets spanning a wide variety of chemical end points. The results show that ComABAN has higher prediction accuracy compared with the classical machine learning method and the deep learning-based methods. Furthermore, the trained neural network was used to predict a library of 1.5 million molecules and picked out compounds with a classification result of grade I. Subsequently, these predicted molecules were scored and ranked using cascade docking, molecular dynamics simulations to generate five potential candidates. All five molecules showed high similarity to nanomolar bioactive inhibitors suppressing the expression of HIF-1α, and we synthesized three compounds (Y-1, Y-3, Y-4) and tested their inhibitory ability in vitro. Our results indicate that ComABAN is an effective tool for accelerating drug discovery.
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Affiliation(s)
- Huihui Yan
- Collaborative Innovation Center of Yangtze River Delta Region Green Pharmaceuticals, Zhejiang University of Technology, Hangzhou, 310014, P. R. China.,College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, 310058, P. R. China Fax/Tel: 86-571-8820-845 E-mail:
| | - Yuanyuan Xie
- Collaborative Innovation Center of Yangtze River Delta Region Green Pharmaceuticals, Zhejiang University of Technology, Hangzhou, 310014, P. R. China
| | - Yao Liu
- College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, 310058, P. R. China Fax/Tel: 86-571-8820-845 E-mail:
| | - Leer Yuan
- College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, 310058, P. R. China Fax/Tel: 86-571-8820-845 E-mail:
| | - Rong Sheng
- College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, 310058, P. R. China Fax/Tel: 86-571-8820-845 E-mail:
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5
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Chen GY, Liu XY, Luo J, Yu XB, Liu Y, Tao QW. Integrating Network Pharmacology and Experimental Validation to Explore the Key Mechanism of Gubitong Recipe in the Treatment of Osteoarthritis. COMPUTATIONAL AND MATHEMATICAL METHODS IN MEDICINE 2022; 2022:7858925. [PMID: 35720033 PMCID: PMC9200584 DOI: 10.1155/2022/7858925] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/24/2022] [Revised: 04/25/2022] [Accepted: 05/17/2022] [Indexed: 02/06/2023]
Abstract
Background Gubitong Recipe (GBT) is a prescription based on the Traditional Chinese Medicine (TCM) theory of tonifying the kidney yang and strengthening the bone. A previous multicentral randomized clinical trial has shown that GBT can effectively relieve joint pain and improve quality of life with a high safety in treating osteoarthritis (OA). This study is aimed at elucidating the active compounds, potential targets, and mechanisms of GBT for treating OA. Method The network pharmacology method was used to predict the key active compounds, targets, and mechanisms of GBT in treating OA. An OA rat model was established with Hulth surgery, and the pathological changes of articular cartilage were observed to evaluate the effects of GBT. Chondrocytes were stimulated with LPS to establish in vitro models, and key targets and mechanisms predicted by network pharmacology were verified via qRT-PCR, ELISA, western blot, and immunofluorescence. The Contribution Index Model and molecular docking were used to determine the key active compounds of GBT and the major nodes affecting predicted pathways. Result A total of 500 compounds were acquired from related databases, where 87 active compounds and their 254 corresponding targets were identified. 2979 OA-related genes were collected from three databases, 150 of which were GBT-regulating OA genes. The compound-target network weight analysis and PPI results showed that IL-6 and PGE2 are key targets of GBT in treating OA. KEGG results showed that PI3K/AKT, Toll-like receptor, NFκB, TNF, and HIF-1 are the key signaling pathways. An in vivo experiment showed that GBT could effectively suppress cartilage degradation of OA rats. In vitro experiments demonstrated that GBT can inhibit the key targets of KEGG-related pathways. Molecular-docking results suggested that luteolin, licochalcone A, and β-carotene were key targets of GBT, and the mechanisms may be associated with the NFκB signaling pathway. Blockage experiments showed that the NFκB pathway is the key pathway of GBT in treating OA. Conclusion This study verified that GBT can effectively protect articular cartilage through multitarget and multipathway, and its inhibitory effect on the NFκB pathway is the most key mechanism in treating OA.
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Affiliation(s)
- Guang-yao Chen
- Beijing University of Chinese Medicine, Beijing 100029, China
| | - Xiao-yu Liu
- Beijing University of Chinese Medicine, Beijing 100029, China
| | - Jing Luo
- Department of TCM Rheumatology, China-Japan Friendship Hospital, Beijing 100029, China
- Beijing Key Lab for Immune-Mediated Inflammatory Diseases, China-Japan Friendship Hospital, Beijing 100029, China
| | - Xin-bo Yu
- Beijing University of Chinese Medicine, Beijing 100029, China
- Department of TCM Rheumatology, China-Japan Friendship Hospital, Beijing 100029, China
| | - Yi Liu
- Beijing University of Chinese Medicine, Beijing 100029, China
| | - Qing-wen Tao
- Department of TCM Rheumatology, China-Japan Friendship Hospital, Beijing 100029, China
- Beijing Key Lab for Immune-Mediated Inflammatory Diseases, China-Japan Friendship Hospital, Beijing 100029, China
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Greve JM, Pinkham AM, Thompson Z, Cowan JA. Active site characterization and activity of the human aspartyl (asparaginyl) β-hydroxylase. Metallomics 2021; 13:6372921. [PMID: 34543426 DOI: 10.1093/mtomcs/mfab056] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2021] [Accepted: 09/06/2021] [Indexed: 01/18/2023]
Abstract
Human aspartyl/asparaginyl beta-hydroxylase (HAAH) is a member of the superfamily of nonheme Fe2+/α-ketoglutarate (αKG) dependent oxygenase enzymes with a noncanonical active site. HAAH hydroxylates epidermal growth factor (EGF) like domains to form the β-hydroxylated product from substrate asparagine or aspartic acid and has been suggested to have a negative impact in a variety of cancers. In addition to iron, HAAH also binds divalent calcium, although the role of the latter is not understood. Herein, the metal binding chemistry and influence on enzyme stability and activity have been evaluated by a combined biochemical and biophysical approach. Metal binding parameters for the HAAH active site were determined by use of isothermal titration calorimetry, demonstrating a high-affinity regulatory binding site for Ca2+ in the catalytic domain in addition to the catalytic Fe2+ cofactor. We have analyzed various active site derivatives, utilizing LC-MS and a new HPLC technique to determine the role of metal binding and the second coordination sphere in enzyme activity, discovering a previously unreported residue as vital for HAAH turnover. This analysis of the in vitro biochemical function of HAAH furthers the understanding of its importance to cellular biochemistry and metabolic pathways.
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Affiliation(s)
- Jenna M Greve
- Department of Chemistry and Biochemistry, The Ohio State University, 100 West 18th Avenue, Columbus, OH 43210, USA
| | - Andrew M Pinkham
- Department of Chemistry and Biochemistry, The Ohio State University, 100 West 18th Avenue, Columbus, OH 43210, USA
| | - Zechariah Thompson
- Department of Chemistry and Biochemistry, The Ohio State University, 100 West 18th Avenue, Columbus, OH 43210, USA
| | - J A Cowan
- Department of Chemistry and Biochemistry, The Ohio State University, 100 West 18th Avenue, Columbus, OH 43210, USA
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7
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Greve JM, Pinkham AM, Cowan JA. Human Aspartyl (Asparaginyl) Hydroxylase. A Multifaceted Enzyme with Broad Intra- and Extracellular Activity. Metallomics 2021; 13:6324587. [PMID: 34283245 DOI: 10.1093/mtomcs/mfab044] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2021] [Accepted: 06/29/2021] [Indexed: 01/12/2023]
Abstract
Human aspartyl (asparaginyl) β-hydroxylase (HAAH), a unique iron and 2-oxoglutarate dependent oxygenase, has shown increased importance as a suspected oncogenic protein. HAAH and its associated mRNA are upregulated in a wide variety of cancer types, however, the current role of HAAH in the malignant transformation of cells is unknown. HAAH is suspected to play an important role in NOTCH signaling via selective hydroxylation of aspartic acid and asparagine residues of epidermal growth factor (EGF)-like domains. HAAH hydroxylation also potentially mediates calcium signaling and oxygen sensing. In this review we summarize the current state of understanding of the biochemistry and chemical biology of this enzyme, identify key differences from other family members, outline its broader intra- and extracellular roles, and identify the most promising areas for future research efforts.
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Affiliation(s)
- Jenna M Greve
- Contribution from the Department of Chemistry and Biochemistry, The Ohio State University, 100 West 18th Avenue, Columbus, Ohio 43210, USA
| | - Andrew M Pinkham
- Contribution from the Department of Chemistry and Biochemistry, The Ohio State University, 100 West 18th Avenue, Columbus, Ohio 43210, USA
| | - J A Cowan
- Contribution from the Department of Chemistry and Biochemistry, The Ohio State University, 100 West 18th Avenue, Columbus, Ohio 43210, USA
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8
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Wu Y, Li Z, McDonough MA, Schofield CJ, Zhang X. Inhibition of the Oxygen-Sensing Asparaginyl Hydroxylase Factor Inhibiting Hypoxia-Inducible Factor: A Potential Hypoxia Response Modulating Strategy. J Med Chem 2021; 64:7189-7209. [PMID: 34029087 DOI: 10.1021/acs.jmedchem.1c00415] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Factor inhibiting hypoxia-inducible factor (FIH) is a JmjC domain 2-oxogluarate and Fe(II)-dependent oxygenase that catalyzes hydroxylation of specific asparagines in the C-terminal transcriptional activation domain of hypoxia-inducible factor alpha (HIF-α) isoforms. This modification suppresses the transcriptional activity of HIF by reducing its interaction with the transcriptional coactivators p300/CBP. By contrast with inhibition of the HIF prolyl hydroxylases (PHDs), inhibitors of FIH, which accepts multiple non-HIF substrates, are less studied; they are of interest due to their potential ability to alter metabolism (either in a HIF-dependent and/or -independent manner) and, provided HIF is upregulated, to modulate the course of the HIF-mediated hypoxic response. Here we review studies on the mechanism and inhibition of FIH. We discuss proposed biological roles of FIH including its regulation of HIF activity and potential roles of FIH-catalyzed oxidation of non-HIF substrates. We highlight potential therapeutic applications of FIH inhibitors.
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Affiliation(s)
- Yue Wu
- Jiangsu Key Laboratory of Drug Design and Optimization, and Department of Chemistry, China Pharmaceutical University, Nanjing 211198, China
| | - Zhihong Li
- Jiangsu Key Laboratory of Drug Design and Optimization, and Department of Chemistry, China Pharmaceutical University, Nanjing 211198, China
| | - Michael A McDonough
- Chemistry Research Laboratory, Department of Chemistry and the Ineos Institute for Antimicrobial Research, University of Oxford, 12 Mansfield Road, Oxford OX1 3TA, United Kingdom
| | - Christopher J Schofield
- Chemistry Research Laboratory, Department of Chemistry and the Ineos Institute for Antimicrobial Research, University of Oxford, 12 Mansfield Road, Oxford OX1 3TA, United Kingdom
| | - Xiaojin Zhang
- Jiangsu Key Laboratory of Drug Design and Optimization, and Department of Chemistry, China Pharmaceutical University, Nanjing 211198, China
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Martin CB, Chaplin VD, Eyles SJ, Knapp MJ. Protein Flexibility of the α-Ketoglutarate-Dependent Oxygenase Factor-Inhibiting HIF-1: Implications for Substrate Binding, Catalysis, and Regulation. Biochemistry 2019; 58:4047-4057. [PMID: 31499004 DOI: 10.1021/acs.biochem.9b00619] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Protein dynamics are crucial for the mechanistically ordered enzymes to bind to their substrate in the correct sequence and perform catalysis. Factor-inhibiting HIF-1 (FIH) is a nonheme Fe(II) α-ketoglutarate-dependent oxygenase that is a key hypoxia (low pO2) sensor in humans. As these hypoxia-sensing enzymes follow a multistep chemical mechanism consuming α-ketoglutarate, a protein substrate that is hydroxylated, and O2, understanding protein flexibility and the order of substrate binding may aid in the development of strategies for selective targeting. The primary substrate of FIH is the C-terminal transactivation domain (CTAD) of hypoxia-inducible factor 1α (HIF) that is hydroxylated on the side chain of Asn803. We assessed changes in protein flexibility connected to metal and αKG binding, finding that (M+αKG) binding significantly stabilized the cupin barrel core of FIH as evidenced by enhanced thermal stability and decreased protein dynamics as assessed by global amide hydrogen/deuterium exchange mass spectrometry and limited proteolysis. Confirming predictions of the consensus mechanism, (M+αKG) increased the affinity of FIH for CTAD as measured by titrations monitoring intrinsic tryptophan fluorescence. The decreased protein dynamics caused by (M+αKG) enforces a sequentially ordered substrate binding sequence in which αKG binds before CTAD, suggesting that selective inhibition may require inhibitors that target the binding sites of both αKG and the prime substrate. A consequence of the correlation between dynamics and αKG binding is that all relevant ligands must be included in binding-based inhibitor screens, as shown by testing permutations of M, αKG, and inhibitor.
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Affiliation(s)
- Cristina B Martin
- Department of Chemistry , University of Massachusetts , Amherst , Massachusetts 01003 , United States
| | - Vanessa D Chaplin
- Department of Chemistry , University of Massachusetts , Amherst , Massachusetts 01003 , United States
| | - Stephen J Eyles
- Department of Biochemistry and Molecular Biology , University of Massachusetts , Amherst , Massachusetts 01003 , United States
| | - Michael J Knapp
- Department of Chemistry , University of Massachusetts , Amherst , Massachusetts 01003 , United States
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Chaplin VD, Hangasky JA, Huang HT, Duan R, Maroney MJ, Knapp MJ. Chloride Supports O 2 Activation in the D201G Facial Triad Variant of Factor-Inhibiting Hypoxia Inducible Factor, an α-Ketoglutarate Dependent Oxygenase. Inorg Chem 2018; 57:12588-12595. [PMID: 30252455 DOI: 10.1021/acs.inorgchem.8b01736] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
α-Ketoglutarate (αKG) dependent oxygenases comprise a large superfamily of enzymes that activate O2 for varied reactions. While most of these enzymes contain a nonheme Fe bound by a His2(Asp/Glu) facial triad, a small number of αKG-dependent halogenases require only the two His ligands to bind Fe and activate O2. The enzyme "factor inhibiting HIF" (FIH) contains a His2Asp facial triad and selectively hydroxylates polypeptides; however, removal of the Asp ligand in the Asp201→Gly variant leads to a highly active enzyme, seemingly without a complete facial triad. Herein, we report on the formation of an Fe-Cl cofactor structure for the Asp201→Gly FIH variant using X-ray absorption spectroscopy (XAS), which provides insight into the structure of the His2Cl facial triad found in halogenases. The Asp201→Gly variant supports anion dependent peptide hydroxylation, demonstrating the requirement for a complete His2X facial triad to support O2 reactivity. Our results indicated that exogenous ligand binding to form a complete His2X facial triad was essential for O2 activation and provides a structural model for the His2Cl-bound nonheme Fe found in halogenases.
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Affiliation(s)
- Vanessa D Chaplin
- Department of Chemistry , University of Massachusetts at Amherst , Amherst , Massachusetts 01003 , United States
| | - John A Hangasky
- Department of Chemistry , University of Massachusetts at Amherst , Amherst , Massachusetts 01003 , United States
| | - Hsin-Ting Huang
- Department of Chemistry , University of Massachusetts at Amherst , Amherst , Massachusetts 01003 , United States
| | - Ran Duan
- Department of Chemistry , University of Massachusetts at Amherst , Amherst , Massachusetts 01003 , United States
| | - Michael J Maroney
- Department of Chemistry , University of Massachusetts at Amherst , Amherst , Massachusetts 01003 , United States
| | - Michael J Knapp
- Department of Chemistry , University of Massachusetts at Amherst , Amherst , Massachusetts 01003 , United States
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Hangasky JA, Taabazuing CY, Martin CB, Eron SJ, Knapp MJ. The facial triad in the α-ketoglutarate dependent oxygenase FIH: A role for sterics in linking substrate binding to O 2 activation. J Inorg Biochem 2017; 166:26-33. [PMID: 27815979 PMCID: PMC5161613 DOI: 10.1016/j.jinorgbio.2016.10.007] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2016] [Revised: 10/07/2016] [Accepted: 10/13/2016] [Indexed: 02/06/2023]
Abstract
The factor inhibiting hypoxia inducible factor-1α (FIH) is a nonheme Fe(II)/αKG oxygenase using a 2-His-1-Asp facial triad. FIH activates O2 via oxidative decarboxylation of α-ketoglutarate (αKG) to generate an enzyme-based oxidant which hydroxylates the Asn803 residue within the C-terminal transactivation domain (CTAD) of HIF-1α. Tight coupling of these two sequential reactions requires a structural linkage between the Fe(II) and the substrate binding site to ensure that O2 activation occurs after substrate binds. We tested the hypothesis that the facial triad carboxylate (Asp201) of FIH linked substrate binding and O2 binding sites. Asp201 variants of FIH were constructed and thoroughly characterized in vitro using steady-state kinetics, crystallography, autohydroxylation, and coupling measurements. Our studies revealed each variant activated O2 with a catalytic efficiency similar to that of wild-type (WT) FIH (kcataKM(O2)=0.17μM-1min-1), but led to defects in the coupling of O2 activation to substrate hydroxylation. Steady-state kinetics showed similar catalytic efficiencies for hydroxylation by WT-FIH (kcat/KM(CTAD)=0.42μM-1min-1) and D201G (kcat/KM(CTAD)=0.34μM-1min-1); hydroxylation by D201E was greatly impaired, while hydroxylation by D201A was undetectable. Analysis of the crystal structure of the D201E variant revealed steric crowding near the diffusible ligand site supporting a role for sterics from the facial triad carboxylate in the O2 binding order. Our data support a model in which the facial triad carboxylate Asp201 provides both steric and polar contacts to favor O2 access to the Fe(II) only after substrate binds, leading to coupled turnover in FIH and other αKG oxygenases.
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Affiliation(s)
- John A Hangasky
- Department of Chemistry, University of Massachusetts, Amherst, United States
| | | | - Cristina B Martin
- Department of Chemistry, University of Massachusetts, Amherst, United States
| | - Scott J Eron
- Department of Chemistry, University of Massachusetts, Amherst, United States
| | - Michael J Knapp
- Department of Chemistry, University of Massachusetts, Amherst, United States.
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