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Ghebreamlak S, Stoian SA, Lees NS, Cronin B, Smith F, Ross MO, Telser J, Hoffman BM, Duin EC. The Active-Site [4Fe-4S] Cluster in the Isoprenoid Biosynthesis Enzyme IspH Adopts Unexpected Redox States during Ligand Binding and Catalysis. J Am Chem Soc 2024; 146:3926-3942. [PMID: 38291562 DOI: 10.1021/jacs.3c11674] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2024]
Abstract
(E)-4-Hydroxy-3-methylbut-2-enyl diphosphate reductase, or IspH (formerly known as LytB), catalyzes the terminal step of the bacterial methylerythritol phosphate (MEP) pathway for isoprene synthesis. This step converts (E)-4-hydroxy-3-methylbut-2-enyl diphosphate (HMBPP) into one of two possible isomeric products, either isopentenyl diphosphate (IPP) or dimethylallyl diphosphate (DMAPP). This reaction involves the removal of the C4 hydroxyl group of HMBPP and addition of two electrons. IspH contains a [4Fe-4S] cluster in its active site, and multiple cluster-based paramagnetic species of uncertain redox and ligation states can be detected after incubation with reductant, addition of a ligand, or during catalysis. To characterize the clusters in these species, 57Fe-labeled samples of IspH were prepared and studied by electron paramagnetic resonance (EPR), 57Fe electron-nuclear double resonance (ENDOR), and Mössbauer spectroscopies. Notably, this ENDOR study provides a rarely reported, complete determination of the 57Fe hyperfine tensors for all four Fe ions in a [4Fe-4S] cluster. The resting state of the enzyme (Ox) has a diamagnetic [4Fe-4S]2+ cluster. Reduction generates [4Fe-4S]+ (Red) with both S = 1/2 and S = 3/2 spin ground states. When the reduced enzyme is incubated with substrate, a transient paramagnetic reaction intermediate is detected (Int) which is thought to contain a cluster-bound substrate-derived species. The EPR properties of Int are indicative of a 3+ iron-sulfur cluster oxidation state, and the Mössbauer spectra presented here confirm this. Incubation of reduced enzyme with the product IPP induced yet another paramagnetic [4Fe-4S]+ species (Red+P) with S = 1/2. However, the g-tensor of this state is commonly associated with a 3+ oxidation state, while Mössbauer parameters show features typical for 2+ clusters. Implications of these complicated results are discussed.
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Affiliation(s)
- Selamawit Ghebreamlak
- Department of Chemistry and Biochemistry, Auburn University, 179 Chemistry Building, Auburn, Alabama 36849, United States
| | - Sebastian A Stoian
- Department of Chemistry, University of Idaho, 875 Perimeter Drive, MS 2343 Moscow, Idaho 83844, United States
| | - Nicholas S Lees
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - Bryan Cronin
- Department of Chemistry and Biochemistry, Auburn University, 179 Chemistry Building, Auburn, Alabama 36849, United States
| | - Forrest Smith
- Department of Drug Discovery & Development, Auburn University, 4306 Walker Building, Auburn, Alabama 36849, United States
| | - Matthew O Ross
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - Joshua Telser
- Department of Biological, Chemical and Physical Sciences, Roosevelt University, 430 S. Michigan Avenue, Chicago, Illinois 60605, United States
| | - Brian M Hoffman
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - Evert C Duin
- Department of Chemistry and Biochemistry, Auburn University, 179 Chemistry Building, Auburn, Alabama 36849, United States
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Brown AC, Suess DLM. Valence Localization in Alkyne and Alkene Adducts of Synthetic [Fe 4S 4] + Clusters. Inorg Chem 2023; 62:1911-1918. [PMID: 35704768 PMCID: PMC9751231 DOI: 10.1021/acs.inorgchem.2c01353] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Reported herein are alkyne and alkene adducts of synthetic [Fe4S4]+ clusters that model intermediates and inhibitor-bound states in enzymes involved in isoprenoid biosynthesis. Treatment of the N-heterocyclic carbene-ligated cluster [(IMes)3Fe4S4(OEt2)][BArF4] (IMes = 1,3-dimesitylimidazol-2-ylidene; [BArF4]- = tetrakis(3,5-bis(trifluoromethyl)phenyl)borate) with phenylacetylene (PhCCH) or cis-cyclooctene (COE) results in displacement of the Et2O ligand to yield the corresponding π complexes, [(IMes)3Fe4S4(PhCCH)][BArF4] and [(IMes)3Fe4S4(COE)][BArF4]. EPR spectroscopic analysis demonstrates that both clusters are doublets with giso > 2 and thus are spectroscopically faithful models of the analogous species characterized in the isoprenoid biosynthetic enzymes IspG and IspH. Structural and Mössbauer spectroscopic analysis reveals that both complexes are best described as [Fe4S4]+ clusters in which the unique Fe site engages in modest back-bonding to the π-acidic ligand. Paramagnetic NMR studies show that, even at room temperature, the alkyne/alkene-bound Fe centers harbor minority spin and therefore adopt an Fe2+ valence. We propose that such valence localization could likewise occur in Fe-S enzymes that interact with π-acidic molecules.
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Huang S, Xue Y, Ma Y, Zhou C. Microbial (E)-4-hydroxy-3-methylbut-2-enyl pyrophosphate reductase (IspH) and its biotechnological potential: A mini review. Front Bioeng Biotechnol 2022; 10:1057938. [DOI: 10.3389/fbioe.2022.1057938] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2022] [Accepted: 11/10/2022] [Indexed: 11/30/2022] Open
Abstract
(E)-4-hydroxy-3-methylbut-2-enyl pyrophosphate (HMBPP) reductase (IspH) is a [4Fe-4S] cluster-containing enzyme, involved in isoprenoid biosynthesis as the final enzyme of the methylerythritol phosphate (MEP) pathway found in many bacteria and malaria parasites. In recent years, many studies have revealed that isoprenoid compounds are an alternative to petroleum-derived fuels. Thus, ecofriendly methods harnessing the methylerythritol phosphate pathway in microbes to synthesize isoprenoid compounds and IspH itself have received notable attention from researchers. In addition to its applications in the field of biosynthesis, IspH is considered to be an attractive drug target for infectious diseases such as malaria and tuberculosis due to its survivability in most pathogenic bacterium and its absence in humans. In this mini-review, we summarize previous reports that have systematically illuminated the fundamental and structural properties, substrate binding and catalysis, proposed catalytic mechanism, and novel catalytic activities of IspH. Potential bioengineering and biotechnological applications of IspH are also discussed.
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Jobelius H, Bianchino GI, Borel F, Chaignon P, Seemann M. The Reductive Dehydroxylation Catalyzed by IspH, a Source of Inspiration for the Development of Novel Anti-Infectives. MOLECULES (BASEL, SWITZERLAND) 2022; 27:molecules27030708. [PMID: 35163971 PMCID: PMC8837944 DOI: 10.3390/molecules27030708] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/05/2021] [Revised: 01/11/2022] [Accepted: 01/18/2022] [Indexed: 11/16/2022]
Abstract
The non-mevalonate or also called MEP pathway is an essential route for the biosynthesis of isoprenoid precursors in most bacteria and in microorganisms belonging to the Apicomplexa phylum, such as the parasite responsible for malaria. The absence of this pathway in mammalians makes it an interesting target for the discovery of novel anti-infectives. As last enzyme of this pathway, IspH is an oxygen sensitive [4Fe-4S] metalloenzyme that catalyzes 2H+/2e− reductions and a water elimination by involving non-conventional bioinorganic and bioorganometallic intermediates. After a detailed description of the discovery of the [4Fe-4S] cluster of IspH, this review focuses on the IspH mechanism discussing the results that have been obtained in the last decades using an approach combining chemistry, enzymology, crystallography, spectroscopies, and docking calculations. Considering the interesting druggability of this enzyme, a section about the inhibitors of IspH discovered up to now is reported as well. The presented results constitute a useful and rational help to inaugurate the design and development of new potential chemotherapeutics against pathogenic organisms.
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Affiliation(s)
- Hannah Jobelius
- Equipe Chimie Biologique et Applications Thérapeutiques, Institut de Chimie de Strasbourg UMR 7177, Université de Strasbourg/CNRS, 4, rue Blaise Pascal, 67070 Strasbourg, France; (H.J.); (G.I.B.); (P.C.)
| | - Gabriella Ines Bianchino
- Equipe Chimie Biologique et Applications Thérapeutiques, Institut de Chimie de Strasbourg UMR 7177, Université de Strasbourg/CNRS, 4, rue Blaise Pascal, 67070 Strasbourg, France; (H.J.); (G.I.B.); (P.C.)
| | - Franck Borel
- Institut de Biologie Structurale, Université Grenoble Alpes/CEA/CNRS, 38000 Grenoble, France;
| | - Philippe Chaignon
- Equipe Chimie Biologique et Applications Thérapeutiques, Institut de Chimie de Strasbourg UMR 7177, Université de Strasbourg/CNRS, 4, rue Blaise Pascal, 67070 Strasbourg, France; (H.J.); (G.I.B.); (P.C.)
| | - Myriam Seemann
- Equipe Chimie Biologique et Applications Thérapeutiques, Institut de Chimie de Strasbourg UMR 7177, Université de Strasbourg/CNRS, 4, rue Blaise Pascal, 67070 Strasbourg, France; (H.J.); (G.I.B.); (P.C.)
- Correspondence:
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McSkimming A, Sridharan A, Thompson NB, Müller P, Suess DLM. An [Fe 4S 4] 3+-Alkyl Cluster Stabilized by an Expanded Scorpionate Ligand. J Am Chem Soc 2020; 142:14314-14323. [PMID: 32692919 DOI: 10.1021/jacs.0c06334] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Alkyl-ligated iron-sulfur clusters in the [Fe4S4]3+ charge state have been proposed as short-lived intermediates in a number of enzymatic reactions. To better understand the properties of these intermediates, we have prepared and characterized the first synthetic [Fe4S4]3+-alkyl cluster. Isolation of this highly reactive species was made possible by the development of an expanded scorpionate ligand suited to the encapsulation of cuboidal clusters. Like the proposed enzymatic intermediates, this synthetic [Fe4S4]3+-alkyl cluster adopts an S = 1/2 ground state with giso > 2. Mössbauer spectroscopic studies reveal that the alkylated Fe has an unusually low isomer shift, which reflects the highly covalent Fe-C bond and the localization of Fe3+ at the alkylated site in the solid state. Paramagnetic 1H NMR studies establish that this valence localization persists in solution at physiologically relevant temperatures, an effect that has not been observed for [Fe4S4]3+ clusters outside of a protein. These findings establish the unusual electronic-structure effects imparted by the strong-field alkyl ligand and lay the foundation for understanding the electronic structures of [Fe4S4]3+-alkyl intermediates in biology.
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Affiliation(s)
- Alex McSkimming
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Arun Sridharan
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Niklas B Thompson
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Peter Müller
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Daniel L M Suess
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
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Chaignon P, Petit BE, Vincent B, Allouche L, Seemann M. Methylerythritol Phosphate Pathway: Enzymatic Evidence for a Rotation in the LytB/IspH-Catalyzed Reaction. Chemistry 2020; 26:1032-1036. [PMID: 31756006 DOI: 10.1002/chem.201904676] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2019] [Indexed: 11/10/2022]
Abstract
IspH/LytB, an oxygen-sensitive [4Fe-4S] enzyme, catalyzes the last step of the methylerythritol phosphate (MEP) pathway, a target for the development of new antimicrobial agents. This metalloenzyme converts (E)-4-hydroxy-3-methylbut-2-en-1-yl diphosphate (HMBPP) into the two isoprenoid precursors: isopentenyl diphosphate (IPP) and dimethylallyl diphosphate (DMAPP). Here, the synthesis of (S)-[4-2 H1 ]HMBPP and (R)-[4-2 H1 ]HMBPP is reported together with a detailed NMR analysis of the products formed after their respective incubation with E. coli IspH/LytB in the presence of the biological reduction system used by E. coli to reduce the [4Fe-4S] center. (S)-[4-2 H1 ]HMBPP was converted into [4-2 H1 ]DMAPP and (E)-[4-2 H1 ]IPP, whereas (R)-[4-2 H1 ]HMBPP yielded [4-2 H1 ]DMAPP and (Z)-[4-2 H1 ]IPP, hence providing the direct enzymatic evidence that the mechanism catalyzed by IspH/LytB involves a rotation of the CH2 OH group of the substrate to display it away from the [4Fe-4S].
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Affiliation(s)
- Philippe Chaignon
- Equipe Chimie Biologique et Applications Thérapeutiques, Institut de Chimie UMR 7177, Université de Strasbourg, CNRS, 4, rue Blaise Pascal, 67070, Strasbourg, France
| | - Benoît Eric Petit
- Equipe Chimie Biologique et Applications Thérapeutiques, Institut de Chimie UMR 7177, Université de Strasbourg, CNRS, 4, rue Blaise Pascal, 67070, Strasbourg, France
| | - Bruno Vincent
- Service de R.M.N., Fédération de Chimie Le Bel FR2010, Université de Strasbourg, CNRS, 1, rue Blaise Pascal, 67008, Strasbourg, France
| | - Lionel Allouche
- Service de R.M.N., Fédération de Chimie Le Bel FR2010, Université de Strasbourg, CNRS, 1, rue Blaise Pascal, 67008, Strasbourg, France
| | - Myriam Seemann
- Equipe Chimie Biologique et Applications Thérapeutiques, Institut de Chimie UMR 7177, Université de Strasbourg, CNRS, 4, rue Blaise Pascal, 67070, Strasbourg, France
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Ye M, Thompson NB, Brown AC, Suess DLM. A Synthetic Model of Enzymatic [Fe 4S 4]-Alkyl Intermediates. J Am Chem Soc 2019; 141:13330-13335. [PMID: 31373801 PMCID: PMC6748666 DOI: 10.1021/jacs.9b06975] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
![]()
Although
alkyl complexes of [Fe4S4] clusters
have been invoked as intermediates in a number of enzymatic reactions,
obtaining a detailed understanding of their reactivity patterns and
electronic structures has been difficult owing to their transient
nature. To address this challenge, we herein report the synthesis
and characterization of a 3:1 site-differentiated [Fe4S4]2+–alkyl cluster. Whereas [Fe4S4]2+ clusters typically exhibit pairwise delocalized
electronic structures in which each Fe has a formal valence of 2.5+,
Mössbauer spectroscopic and computational studies suggest that
the highly electron-releasing alkyl group partially localizes the
charge distribution within the cubane, an effect that has not been
previously observed in tetrahedrally coordinated [Fe4S4] clusters.
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Affiliation(s)
- Mengshan Ye
- Department of Chemistry , Massachusetts Institute of Technology , Cambridge , Massachusetts 02139 , United States
| | - Niklas B Thompson
- Department of Chemistry , Massachusetts Institute of Technology , Cambridge , Massachusetts 02139 , United States
| | - Alexandra C Brown
- Department of Chemistry , Massachusetts Institute of Technology , Cambridge , Massachusetts 02139 , United States
| | - Daniel L M Suess
- Department of Chemistry , Massachusetts Institute of Technology , Cambridge , Massachusetts 02139 , United States
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Abstract
IspH, (E)-1-hydroxy-2-methyl-but-2-enyl 4-diphosphate reductase, is an essential enzyme in isoprenoid biosynthesis and an important drug/herbicide target. Using X-ray crystallographic, bioinformatics, mutagenesis/kinetics/stability, and electron paramagnetic resonance (EPR) results, we show that organisms from different environments ultilize one of four main IspH classes. The classes are based on the arrangement of the aromatic residues near the 4Fe-4S cluster and the presence or absence of N- and C-terminal extensions. Class A enzymes are found primarily in anaerobic and microaerophilic bacteria. Class B enzymes are found in aerobic bacteria. Class C enzymes are found in cyanobacteria and plants. Class D enzymes are found in apicomplexan parasites. Using mutagenesis, we show that the cluster-associated aromatic groups in class A and class B IspHs enhance cluster oxidative stability. Y198A, F302A, and a C-terminal truncation mutant of the class B (Escherichia coli) IspH have catalytic activity lower than that of the wild-type protein when using methyl viologen as the electron donor, but higher activity with dithionite as the electron donor, due to ready access of the small reductant to the cluster, consistent with their increased oxygen and H2O2 sensitivity. F302A has the largest effect on the reaction rates, and EPR studies indicate this residue affects Fe-S cluster structure. Similar effects on cluster stability are seen with class A (F14A and Y98A) mutants; however, effects on ET rates are smaller, and there are no differences between the EPR spectra of mutant and wild-type proteins. Overall, the results are of general interest because they show, for the first time, that there are multiple IspH classes that have evolved to allow organisms to survive in diverse oxidative-stress environments.
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Affiliation(s)
- Guodong Rao
- Department of Chemistry, University of Illinois , Urbana, Illinois 61801, United States
| | - Eric Oldfield
- Department of Chemistry, University of Illinois , Urbana, Illinois 61801, United States
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Horitani M, Shisler K, Broderick WE, Hutcheson RU, Duschene KS, Marts AR, Hoffman BM, Broderick JB. Radical SAM catalysis via an organometallic intermediate with an Fe-[5'-C]-deoxyadenosyl bond. Science 2016; 352:822-5. [PMID: 27174986 DOI: 10.1126/science.aaf5327] [Citation(s) in RCA: 103] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2016] [Accepted: 03/29/2016] [Indexed: 11/02/2022]
Abstract
Radical S-adenosylmethionine (SAM) enzymes use a [4Fe-4S] cluster to cleave SAM to initiate diverse radical reactions. These reactions are thought to involve the 5'-deoxyadenosyl radical intermediate, which has not yet been detected. We used rapid freeze-quenching to trap a catalytically competent intermediate in the reaction catalyzed by the radical SAM enzyme pyruvate formate-lyase activating enzyme. Characterization of the intermediate by electron paramagnetic resonance and (13)C, (57)Fe electron nuclear double-resonance spectroscopies reveals that it contains an organometallic center in which the 5' carbon of a SAM-derived deoxyadenosyl moiety forms a bond with the unique iron site of the [4Fe-4S] cluster. Discovery of this intermediate extends the list of enzymatic bioorganometallic centers to the radical SAM enzymes, the largest enzyme superfamily known, and reveals intriguing parallels to B12 radical enzymes.
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Affiliation(s)
- Masaki Horitani
- Department of Chemistry, Northwestern University, Evanston, IL 60208, USA
| | - Krista Shisler
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, MT 59717, USA
| | - William E Broderick
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, MT 59717, USA
| | - Rachel U Hutcheson
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, MT 59717, USA
| | - Kaitlin S Duschene
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, MT 59717, USA
| | - Amy R Marts
- Department of Chemistry, Northwestern University, Evanston, IL 60208, USA
| | - Brian M Hoffman
- Department of Chemistry, Northwestern University, Evanston, IL 60208, USA.
| | - Joan B Broderick
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, MT 59717, USA.
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Rao G, O'Dowd B, Li J, Wang K, Oldfield E. IspH-RPS1 and IspH-UbiA: "Rosetta Stone" Proteins. Chem Sci 2015; 6:6813-6822. [PMID: 26865948 PMCID: PMC4746011 DOI: 10.1039/c5sc02600h] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
IspH forms fusion hybrids with RPS1 as well as UbiA, examples of Rosetta stone proteins.
The protein IspH, (E)-1-hydroxy-2-methyl-but-2-enyl 4-diphosphate (HMPPP) reductase, is an essential 4Fe–4S cluster-containing protein in the methylerythritol phosphate pathway for isoprenoid biosynthesis. Using a sequence similarity network we found that there are >400 IspH proteins that are about twice as large as most of the IspHs studied to date since their IspH domains are fused to either the ribosomal protein S1 (RPS1), or to a UbiA (4-hydroxybenzoate octaprenyltransferase)-like protein. Many of the IspH–RPS1 proteins are present in anaerobes found in the human gut and some, such as Clostridium botulinum, C. tetani and Fusobacterium nucleatum, are pathogens. The IspH–UbiAs are all found in sulfate-reducing anaerobes. The IspH domains in IspH–RPS1 are fused to 4 and in a few cases 6 tandem repeats in RPS1 that, in most organisms, bind to mRNA or form part of the bacterial ribosome. Mutants in which the four RPS1 domains were sequentially eliminated had similar IspH activity as wild-type protein, indicating they are not essential for IspH catalysis. Overall, the results are of interest since they represent the first isolation of a catalytically active IspH–RPS1, as well as the identification of IspH–UbiA hybrids, two “Rosetta stone” proteins that are likely to be functionally related—IspH producing the isoprenoids required for a UbiA-like prenyltransferase; the IspH–RPS1 hybrids, perhaps, being involved in the stringent response or as Fe/O2 sensors.
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Affiliation(s)
- Guodong Rao
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL, 61801
| | - Bing O'Dowd
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL, 61801
| | - Jikun Li
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL, 61801
| | - Ke Wang
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL, 61801
| | - Eric Oldfield
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL, 61801
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Brown AC, Kokoczka R, Parish T. LytB1 and LytB2 of Mycobacterium tuberculosis Are Not Genetically Redundant. PLoS One 2015; 10:e0135638. [PMID: 26309039 PMCID: PMC4550268 DOI: 10.1371/journal.pone.0135638] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2015] [Accepted: 07/23/2015] [Indexed: 11/26/2022] Open
Abstract
Mycobacterium tuberculosis synthesises isoprenoid precursors via the MEP/DOXP pathway and at least five enzymes in the pathway (Dxs1, Dxr/IspC, IspD, IspF, and GcpE/IspG) are required for growth in vitro. We investigated the role of LytB (IspH) in M. tuberculosis; M. tuberculosis is unusual in that it has two homologs–LytB1 and LytB2. We were unable to delete the lytB2 gene unless we provided an additional copy elsewhere, demonstrating that this is the essential homolog. We expressed lytB1 from the lytB2 promoter and confirmed that this could not complement for loss of function of lytB2, despite LytB1 possessing all the previously described conserved critical residues. Interestingly the sole LytB homolog of Mycobacterium smegmatis was able to compensate for loss of LytB2 in M. tuberculosis. We tested translational fusions of LytB1 and LytB2 for functionality in M. tuberculosis, but only a fusion with 90% N-terminal LytB2 and 10% C-terminal LytB1 was functional. In order to identify the key difference between the two proteins, site directed mutagenesis was used to change LytB2 residues into their counterparts in LytB1. None of these amino acid substitutions was essential for function and all lytB2 mutant alleles were functional. In contrast, mutation of the key residues for [Fe4S4] cluster formation, as well as a catalytic residue in LytB1 did not result in functional complementation. Thus, although LytB1 and LytB2 are not genetically redundant, this is not dependent on small amino acid changes, but is likely to be a result of major overall structural differences.
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Affiliation(s)
- Amanda Claire Brown
- Queen Mary University of London, London, E1 2AD, United Kingdom
- Barts & the London School of Medicine and Dentistry, London, E1 2AD, United Kingdom
| | - Rachel Kokoczka
- TB Discovery Research, Infectious Disease Research Institute, Seattle, WA, 98102, United States of America
| | - Tanya Parish
- Queen Mary University of London, London, E1 2AD, United Kingdom
- Barts & the London School of Medicine and Dentistry, London, E1 2AD, United Kingdom
- TB Discovery Research, Infectious Disease Research Institute, Seattle, WA, 98102, United States of America
- * E-mail:
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N-Terminal Region of GbIspH1, Ginkgo biloba IspH Type 1, May Be Involved in the pH-Dependent Regulation of Enzyme Activity. Bioinorg Chem Appl 2015; 2015:241479. [PMID: 25892986 PMCID: PMC4393896 DOI: 10.1155/2015/241479] [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: 01/24/2015] [Accepted: 02/28/2015] [Indexed: 11/18/2022] Open
Abstract
GbIspH1, IspH type 1 in Ginkgo biloba chloroplast, is the Fe/S enzyme catalyzing the reductive dehydroxylation of HMBPP to isopentenyl diphosphate (IPP) and dimethylallyl diphosphate (DMAPP) at the final step of methylerythritol phosphate pathway in chloroplast. Compared to the bacterial IspH, plant IspH, including GbIspH1, has an additional polypeptide chain at the N-terminus. Here, biochemical function of the N-terminal region of GbIspH1 was investigated with the N-terminal truncated GbIspH1 (GbIspH1-truncated). Both wild type GbIspH1 (GbIspH1-full) and GbIspH1-truncated were catalytically active and produced IPP and DMAPP in a ratio of 15 : 1. Kinetic parameters of KM (17.3 ± 1.9 and 14.9 ± 2.3 µM) and kcat (369 ± 10 and 347 ± 12 min−1) at pH 8.0 were obtained for GbIspH1-full and GbIspH1-truncated, respectively. Interestingly, GbIspH1-full and GbIspH1-truncated showed significantly different pH-dependent activities, and the maximum enzyme activities were obtained at pH 8.0 and 7.5, respectively. However, catalytic activation energies (Ea) of GbIspH1-full and GbIspH1-truncated were almost the same with 36.5 ± 1.6 and 35.0 ± 1.9 kJ/mol, respectively. It was suggested that the N-terminal region of GbIspH1 is involved in the pH-dependent regulation of enzyme activity during photosynthesis.
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Rekittke I, Warkentin E, Jomaa H, Ermler U. Structure of the GcpE-HMBPP complex from Thermus thermophilius. Biochem Biophys Res Commun 2015; 458:246-50. [DOI: 10.1016/j.bbrc.2015.01.088] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2015] [Accepted: 01/19/2015] [Indexed: 11/28/2022]
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14
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Cutsail GE, Telser J, Hoffman BM. Advanced paramagnetic resonance spectroscopies of iron-sulfur proteins: Electron nuclear double resonance (ENDOR) and electron spin echo envelope modulation (ESEEM). BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2015; 1853:1370-94. [PMID: 25686535 DOI: 10.1016/j.bbamcr.2015.01.025] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/20/2014] [Revised: 01/29/2015] [Accepted: 01/29/2015] [Indexed: 12/20/2022]
Abstract
The advanced electron paramagnetic resonance (EPR) techniques, electron nuclear double resonance (ENDOR) and electron spin echo envelope modulation (ESEEM) spectroscopies, provide unique insights into the structure, coordination chemistry, and biochemical mechanism of nature's widely distributed iron-sulfur cluster (FeS) proteins. This review describes the ENDOR and ESEEM techniques and then provides a series of case studies on their application to a wide variety of FeS proteins including ferredoxins, nitrogenase, and radical SAM enzymes. This article is part of a Special Issue entitled: Fe/S proteins: Analysis, structure, function, biogenesis and diseases.
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Affiliation(s)
- George E Cutsail
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208, USA
| | - Joshua Telser
- Department of Biological, Chemical and Physical Sciences, Roosevelt University, Chicago, IL 60605, USA
| | - Brian M Hoffman
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208, USA.
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15
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Blachly PG, Sandala GM, Giammona D, Liu T, Bashford D, McCammon JA, Noodleman L. Use of Broken-Symmetry Density Functional Theory To Characterize the IspH Oxidized State: Implications for IspH Mechanism and Inhibition. J Chem Theory Comput 2014; 10:3871-3884. [PMID: 25221444 PMCID: PMC4159220 DOI: 10.1021/ct5005214] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2014] [Indexed: 12/31/2022]
Abstract
With current therapies becoming less efficacious due to increased drug resistance, new inhibitors of both bacterial and malarial targets are desperately needed. The recently discovered methylerythritol phosphate (MEP) pathway for isoprenoid synthesis provides novel targets for the development of such drugs. Particular attention has focused on the IspH protein, the final enzyme in the MEP pathway, which uses its [4Fe-4S] cluster to catalyze the formation of the isoprenoid precursors IPP and DMAPP from HMBPP. IspH catalysis is achieved via a 2e-/2H+ reductive dehydroxylation of HMBPP; the mechanism by which catalysis is achieved, however, is highly controversial. The work presented herein provides the first step in assessing different routes to catalysis by using computational methods. By performing broken-symmetry density functional theory (BS-DFT) calculations that employ both the conductor-like screening solvation model (DFT/COSMO) and a finite-difference Poisson-Boltzmann self-consistent reaction field methodology (DFT/SCRF), we evaluate geometries, energies, and Mössbauer signatures of the different protonation states that may exist in the oxidized state of the IspH catalytic cycle. From DFT/SCRF computations performed on the oxidized state, we find a state where the substrate, HMBPP, coordinates the apical iron in the [4Fe-4S] cluster as an alcohol group (ROH) to be one of two, isoenergetic, lowest-energy states. In this state, the HMBPP pyrophosphate moiety and an adjacent glutamate residue (E126) are both fully deprotonated, making the active site highly anionic. Our findings that this low-energy state also matches the experimental geometry of the active site and that its computed isomer shifts agree with experiment validate the use of the DFT/SCRF method to assess relative energies along the IspH reaction pathway. Additional studies of IspH catalytic intermediates are currently being pursued.
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Affiliation(s)
- Patrick G. Blachly
- Department
of Chemistry and Biochemistry, University
of California San Diego, 9500 Gilman Drive, Mail Code 0365, La Jolla, California 92093-0365, United States
| | - Gregory M. Sandala
- Department
of Chemistry and Biochemistry, Mount Allison
University, 63C York
Street, Sackville, New Brunswick E4L 1G8, Canada
| | - Debra
Ann Giammona
- Department
of Structural Biology, St. Jude Children’s
Research Hospital, 262
Danny Thomas Place, Memphis, Tennessee 38105, United States
| | - Tiqing Liu
- Skaggs School of Pharmacy and Pharmaceutical
Sciences, Howard Hughes Medical
Institute, and Department of Pharmacology, University
of California San Diego, La Jolla, California 92093-0365, United States
| | - Donald Bashford
- Department
of Structural Biology, St. Jude Children’s
Research Hospital, 262
Danny Thomas Place, Memphis, Tennessee 38105, United States
| | - J. Andrew McCammon
- Department
of Chemistry and Biochemistry, University
of California San Diego, 9500 Gilman Drive, Mail Code 0365, La Jolla, California 92093-0365, United States
- Skaggs School of Pharmacy and Pharmaceutical
Sciences, Howard Hughes Medical
Institute, and Department of Pharmacology, University
of California San Diego, La Jolla, California 92093-0365, United States
| | - Louis Noodleman
- Department
of Integrative Structural and Computational Biology, The Scripps Research Institute, TPC15, 10550 North Torrey Pines Road, La Jolla, California 92037, United States
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16
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Hsieh WY, Sung TY, Wang HT, Hsieh MH. Functional evidence for the critical amino-terminal conserved domain and key amino acids of Arabidopsis 4-HYDROXY-3-METHYLBUT-2-ENYL DIPHOSPHATE REDUCTASE. PLANT PHYSIOLOGY 2014; 166:57-69. [PMID: 25037211 PMCID: PMC4149731 DOI: 10.1104/pp.114.243642] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
The plant 4-HYDROXY-3-METHYLBUT-2-ENYL DIPHOSPHATE REDUCTASE (HDR) catalyzes the last step of the methylerythritol phosphate pathway to synthesize isopentenyl diphosphate and its allyl isomer dimethylallyl diphosphate, which are common precursors for the synthesis of plastid isoprenoids. The Arabidopsis (Arabidopsis thaliana) genomic HDR transgene-induced gene-silencing lines are albino, variegated, or pale green, confirming that HDR is essential for plants. We used Escherichia coli isoprenoid synthesis H (Protein Data Bank code 3F7T) as a template for homology modeling to identify key amino acids of Arabidopsis HDR. The predicted model reveals that cysteine (Cys)-122, Cys-213, and Cys-350 are involved in iron-sulfur cluster formation and that histidine (His)-152, His-241, glutamate (Glu)-242, Glu-243, threonine (Thr)-244, Thr-312, serine-379, and asparagine-381 are related to substrate binding or catalysis. Glu-242 and Thr-244 are conserved only in cyanobacteria, green algae, and land plants, whereas the other key amino acids are absolutely conserved from bacteria to plants. We used site-directed mutagenesis and complementation assay to confirm that these amino acids, except His-152 and His-241, were critical for Arabidopsis HDR function. Furthermore, the Arabidopsis HDR contains an extra amino-terminal domain following the transit peptide that is highly conserved from cyanobacteria, and green algae to land plants but not existing in the other bacteria. We demonstrated that the amino-terminal conserved domain was essential for Arabidopsis and cyanobacterial HDR function. Further analysis of conserved amino acids in the amino-terminal conserved domain revealed that the tyrosine-72 residue was critical for Arabidopsis HDR. These results suggest that the structure and reaction mechanism of HDR evolution have become specific for oxygen-evolving photosynthesis organisms and that HDR probably evolved independently in cyanobacteria versus other prokaryotes.
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Affiliation(s)
- Wei-Yu Hsieh
- Institute of Plant and Microbial Biology, Academia Sinica, Taipei 11529, Taiwan
| | - Tzu-Ying Sung
- Institute of Plant and Microbial Biology, Academia Sinica, Taipei 11529, Taiwan
| | - Hsin-Tzu Wang
- Institute of Plant and Microbial Biology, Academia Sinica, Taipei 11529, Taiwan
| | - Ming-Hsiun Hsieh
- Institute of Plant and Microbial Biology, Academia Sinica, Taipei 11529, Taiwan
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17
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Span I, Wang K, Eisenreich W, Bacher A, Zhang Y, Oldfield E, Groll M. Insights into the binding of pyridines to the iron-sulfur enzyme IspH. J Am Chem Soc 2014; 136:7926-32. [PMID: 24813236 PMCID: PMC4063180 DOI: 10.1021/ja501127j] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2014] [Indexed: 11/29/2022]
Abstract
(E)-1-Hydroxy-2-methylbut-2-enyl 4-diphosphate reductase (IspH) is a [Fe4S4] cluster-containing enzyme involved in isoprenoid biosynthesis in many bacteria as well as in malaria parasites and is an important drug target. Several inhibitors including amino and thiol substrate analogues, as well as acetylene and pyridine diphosphates, have been reported. Here, we investigate the mode of binding of four pyridine diphosphates to Escherichia coli IspH by using X-ray crystallography. In three cases, one of the iron atoms in the cluster is absent, but in the structure with (pyridin-3-yl)methyl diphosphate, the most potent pyridine-analogue inhibitor reported previously, the fourth iron of the [Fe4S4] cluster is present and interacts with the pyridine ring of the ligand. Based on the results of quantum chemical calculations together with the crystallographic results we propose a side-on η(2) coordination of the nitrogen and the carbon in the 2-position of the pyridine ring to the unique fourth iron in the cluster, which is in the reduced state. The X-ray structure enables excellent predictions using density functional theory of the (14)N hyperfine coupling and quadrupole coupling constants reported previously using HYSCORE spectroscopy, as well as providing a further example of the ability of such [Fe4S4]-containing proteins to form organometallic complexes.
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Affiliation(s)
- Ingrid Span
- Center
for Integrated Protein Science Munich, Chemistry Department, Technische Universität München, Lichtenbergstrasse 4, 85747 Garching, Germany
| | - Ke Wang
- Department
of Chemistry, 600 South
Mathews Avenue, University
of Illinois at Urbana−Champaign, Urbana, Illinois 61801, United States
| | - Wolfgang Eisenreich
- Center
for Integrated Protein Science Munich, Chemistry Department, Technische Universität München, Lichtenbergstrasse 4, 85747 Garching, Germany
| | - Adelbert Bacher
- Center
for Integrated Protein Science Munich, Chemistry Department, Technische Universität München, Lichtenbergstrasse 4, 85747 Garching, Germany
| | - Yong Zhang
- Department
of Chemistry, Chemical Biology, and Biomedical Engineering, Stevens Institute of Technology, Castle Point on Hudson, Hoboken, New Jersey 07030, United States
| | - Eric Oldfield
- Department
of Chemistry, 600 South
Mathews Avenue, University
of Illinois at Urbana−Champaign, Urbana, Illinois 61801, United States
| | - Michael Groll
- Center
for Integrated Protein Science Munich, Chemistry Department, Technische Universität München, Lichtenbergstrasse 4, 85747 Garching, Germany
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18
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Wang W, Oldfield E. Biometallorganische Chemie mit IspG und IspH: Struktur, Funktion und Hemmung der an der Isoprenoid-Biosynthese beteiligten [Fe 4S 4]-Proteine. Angew Chem Int Ed Engl 2014. [DOI: 10.1002/ange.201306712] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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19
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Wang W, Oldfield E. Bioorganometallic chemistry with IspG and IspH: structure, function, and inhibition of the [Fe(4)S(4)] proteins involved in isoprenoid biosynthesis. Angew Chem Int Ed Engl 2014; 53:4294-310. [PMID: 24481599 DOI: 10.1002/anie.201306712] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2013] [Indexed: 11/12/2022]
Abstract
Enzymes of the methylerythritol phosphate pathway of isoprenoid biosynthesis are attractive anti-infective drug targets. The last two enzymes of this pathway, IspG and IspH, are [Fe4 S4 ] proteins that are not produced by humans and catalyze 2 H(+) / 2 e(-) reductions with novel mechanisms. In this Review, we summarize recent advances in structural, mechanistic, and inhibitory studies of these two enzymes. In particular, mechanistic proposals involving bioorganometallic intermediates are presented, and compared with other mechanistic possibilities. In addition, inhibitors based on substrate analogues as well as developed by rational design and compound-library screening, are discussed. The results presented support bioorganometallic catalytic mechanisms for IspG and IspH, and open up new routes to anti-infective drug design targeting [Fe4 S4 ] clusters in proteins.
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Affiliation(s)
- Weixue Wang
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139 (USA)
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20
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Guerra F, Wang K, Li J, Wang W, Liu YL, Amin S, Oldfield E. Inhibition of the 4Fe-4S Proteins IspG and IspH: an EPR, ENDOR and HYSCORE Investigation. Chem Sci 2014; 5:1642-1649. [PMID: 24999381 DOI: 10.1039/c3sc53301h] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
IspG and IspH are proteins that are involved in isoprenoid biosynthesis in most bacteria as well as in malaria parasites and are important drug targets. They contain cubane-type 4Fe-4S clusters that are involved in unusual 2H+/2e- reductions. Here, we report the results of electron paramagnetic resonance spectroscopic investigations of the binding of amino- and thiolo-HMBPP (HMBPP=E-1-hydroxy-2-methyl-but-2-enyl 4-diphosphate) IspH substrate-analog inhibitors to both proteins, as well as the binding of HMBPP and an acetylene diphosphate inhibitor, to IspG. The results show that amino-HMBPP binds to reduced IspH by Fe-C π-bonding with the olefinic carbons interacting with the unique 4th Fe in the 4Fe-4S cluster, quite different to the direct Fe-N ligation seen with the oxidized protein. No such π-complex is observed when amino-HMBPP binds to reduced IspG. No EPR signal is observed with IspH in the presence of dithionite and thiolo-HMBPP, suggesting that the 4Fe-4S cluster is not reduced, consistent with the presence of a 420 nm feature in the absorption spectrum (characteristic of an oxidized cluster). However, with IspG, the EPR spectrum in the presence of dithionite and thiolo-HMBPP is very similar to that seen with HMBPP. The binding of HMBPP to IspG was studied using hyperfine sublevel correlation spectroscopy with 17O and 13C labeled samples: the results rule out direct Fe-O bonding and indicate π-bonding. Finally, the binding to IspG of a potent acetylene diphosphate inhibitor was studied by using electron-nuclear double resonance spectroscopy with 13C labeled ligands: the large hyperfine couplings indicate strong Fe-C π-bonding with the acetylenic group. These results illustrate a remarkable diversity in binding behavior for HMBPP-analog inhibitors, opening up new routes to inhibitor design of interest in the context of anti-bacterial and anti-malarial drug discovery, as well as "cubane-type" metallo-biochemistry, in general.
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Affiliation(s)
- Francisco Guerra
- Center for Biophysics and Computational Biology, University of Illinois at Urbana-Champaign, 607 South Mathews Avenue, Urbana, IL 61801
| | - Ke Wang
- Department of Chemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, IL 61801
| | - Jikun Li
- Center for Biophysics and Computational Biology, University of Illinois at Urbana-Champaign, 607 South Mathews Avenue, Urbana, IL 61801
| | - Weixue Wang
- Center for Biophysics and Computational Biology, University of Illinois at Urbana-Champaign, 607 South Mathews Avenue, Urbana, IL 61801
| | - Yi-Liang Liu
- Center for Biophysics and Computational Biology, University of Illinois at Urbana-Champaign, 607 South Mathews Avenue, Urbana, IL 61801
| | - Shivani Amin
- Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, IL 61801
| | - Eric Oldfield
- Center for Biophysics and Computational Biology, University of Illinois at Urbana-Champaign, 607 South Mathews Avenue, Urbana, IL 61801 ; Department of Chemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, IL 61801
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21
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Zhao L, Chang WC, Xiao Y, Liu HW, Liu P. Methylerythritol phosphate pathway of isoprenoid biosynthesis. Annu Rev Biochem 2013; 82:497-530. [PMID: 23746261 DOI: 10.1146/annurev-biochem-052010-100934] [Citation(s) in RCA: 162] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Isoprenoids are a class of natural products with more than 55,000 members. All isoprenoids are constructed from two precursors, isopentenyl diphosphate and its isomer dimethylallyl diphosphate. Two of the most important discoveries in isoprenoid biosynthetic studies in recent years are the elucidation of a second isoprenoid biosynthetic pathway [the methylerythritol phosphate (MEP) pathway] and a modified mevalonic acid (MVA) pathway. In this review, we summarize mechanistic insights on the MEP pathway enzymes. Because many isoprenoids have important biological activities, the need to produce them in sufficient quantities for downstream research efforts or commercial application is apparent. Recent advances in both MVA and MEP pathway-based synthetic biology are also illustrated by reviewing the landmark work of artemisinic acid and taxadien-5α-ol production through microbial fermentations.
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Affiliation(s)
- Lishan Zhao
- Amyris, Inc., Emeryville, California 94608, USA.
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22
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Ceunen S, Geuns JMC. Steviol glycosides: chemical diversity, metabolism, and function. JOURNAL OF NATURAL PRODUCTS 2013; 76:1201-28. [PMID: 23713723 DOI: 10.1021/np400203b] [Citation(s) in RCA: 184] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Steviol glycosides are a group of highly sweet diterpene glycosides discovered in only a few plant species, most notably the Paraguayan shrub Stevia rebaudiana. During the past few decades, the nutritional and pharmacological benefits of these secondary metabolites have become increasingly apparent. While these properties are now widely recognized, many aspects related to their in vivo biochemistry and metabolism and their relationship to the overall plant physiology of S. rebaudiana are not yet understood. Furthermore, the large size of the steviol glycoside pool commonly found within S. rebaudiana leaves implies a significant metabolic investment and poses questions regarding the benefits S. rebaudiana might gain from their accumulation. The current review intends to thoroughly discuss the available knowledge on these issues.
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Affiliation(s)
- Stijn Ceunen
- Laboratory of Functional Biology, Katholieke Universiteit Leuven, Kasteelpark Arenberg 31, BP 2436, B-3001 Heverlee, Belgium
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23
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Li J, Wang K, Smirnova TI, Khade RL, Zhang Y, Oldfield E. Isoprenoid Biosynthesis: Ferraoxetane or Allyl Anion Mechanism for IspH Catalysis? Angew Chem Int Ed Engl 2013. [DOI: 10.1002/ange.201302343] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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24
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Li J, Wang K, Smirnova TI, Khade RL, Zhang Y, Oldfield E. Isoprenoid biosynthesis: ferraoxetane or allyl anion mechanism for IspH catalysis? Angew Chem Int Ed Engl 2013; 52:6522-5. [PMID: 23649534 PMCID: PMC3821072 DOI: 10.1002/anie.201302343] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2013] [Indexed: 11/08/2022]
Affiliation(s)
- Jikun Li
- Center for Biophysics and Computational Biology, University of Illinois at Urbana-Champaign, 607 South Mathews Avenue, Urbana, IL 61801 (USA)
| | - Ke Wang
- Department of Chemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, IL 61801 (USA), Fax: (+1)217-244-0997
| | - Tatyana I. Smirnova
- Department of Chemistry, North Carolina State University, Raleigh, NC 27695 (USA)
| | - Rahul L. Khade
- Department of Chemistry, Chemical Biology, and Biomedical Engineering, Stevens Institute of Technology, Castle Point on Hudson, Hoboken NJ 07030 (USA)
| | - Yong Zhang
- Department of Chemistry, Chemical Biology, and Biomedical Engineering, Stevens Institute of Technology, Castle Point on Hudson, Hoboken NJ 07030 (USA)
| | - Eric Oldfield
- Department of Chemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana, IL 61801 (USA), Fax: (+1)217-244-0997
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25
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Span I, Wang K, Wang W, Jauch J, Eisenreich W, Bacher A, Oldfield E, Groll M. Structures of fluoro, amino, and thiol inhibitors bound to the [Fe4S4] protein IspH. Angew Chem Int Ed Engl 2013; 52:2118-21. [PMID: 23307751 PMCID: PMC3734547 DOI: 10.1002/anie.201208469] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2012] [Indexed: 11/06/2022]
Affiliation(s)
- Ingrid Span
- Center for Integrated Protein Science Munich, Chemie Department, Technische Universität München, Lichtenbergstrasse 4, 85747 Garching, Germany.
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26
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Janthawornpong K, Krasutsky S, Chaignon P, Rohmer M, Poulter CD, Seemann M. Inhibition of IspH, a [4Fe-4S]2+ enzyme involved in the biosynthesis of isoprenoids via the methylerythritol phosphate pathway. J Am Chem Soc 2013; 135:1816-22. [PMID: 23316732 DOI: 10.1021/ja309557s] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The MEP pathway, which is absent in animals but present in most pathogenic bacteria, in the parasite responsible for malaria and in plant plastids, is a target for the development of antimicrobial drugs. IspH, an oxygen-sensitive [4Fe-4S] enzyme, catalyzes the last step of this pathway and converts (E)-4-hydroxy-3-methylbut-2-en-1-yl diphosphate (HMBPP) into the two isoprenoid precursors: isopentenyl diphosphate (IPP) and dimethylallyl diphosphate (DMAPP). A crucial step in the mechanism of this enzyme is the binding of the C4 hydroxyl of HMBPP to the unique fourth iron site in the [4Fe-4S](2+) moiety. Here, we report the synthesis and the kinetic investigations of two new extremely potent inhibitors of E. coli IspH where the OH group of HMBPP is replaced by an amino and a thiol group. (E)-4-Mercapto-3-methylbut-2-en-1-yl diphosphate is a reversible tight-binding inhibitor of IspH with K(i) = 20 ± 2 nM. A detailed kinetic analysis revealed that (E)-4-amino-3-methylbut-2-en-1-yl diphosphate is a reversible slow-binding inhibitor of IspH with K(i) = 54 ± 19 nM. The slow binding behavior of this inhibitor is best described by a one-step mechanism with the slow step consisting of the formation of the enzyme-inhibitor (EI) complex.
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Affiliation(s)
- Karnjapan Janthawornpong
- Université de Strasbourg, CNRS UMR 7177, Institut Le Bel, 4 rue Blaise Pascal, CS 90032, 67081 Strasbourg Cedex, France
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27
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Span I, Wang K, Wang W, Jauch J, Eisenreich W, Bacher A, Oldfield E, Groll M. Fluor-, Amino- und Thiolinhibitoren im Komplex mit dem [Fe4
S4
]-Protein IspH. Angew Chem Int Ed Engl 2013. [DOI: 10.1002/ange.201208469] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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28
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Wang W, Wang K, Span I, Jauch J, Bacher A, Groll M, Oldfield E. Are free radicals involved in IspH catalysis? An EPR and crystallographic investigation. J Am Chem Soc 2012; 134:11225-34. [PMID: 22687151 DOI: 10.1021/ja303445z] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The [4Fe-4S] protein IspH in the methylerythritol phosphate isoprenoid biosynthesis pathway is an important anti-infective drug target, but its mechanism of action is still the subject of debate. Here, by using electron paramagnetic resonance (EPR) spectroscopy and (2)H, (17)O, and (57)Fe isotopic labeling, we have characterized and assigned two key reaction intermediates in IspH catalysis. The results are consistent with the bioorganometallic mechanism proposed earlier, and the mechanism is proposed to have similarities to that of ferredoxin, thioredoxin reductase, in that one electron is transferred to the [4Fe-4S](2+) cluster, which then performs a formal two-electron reduction of its substrate, generating an oxidized high potential iron-sulfur protein (HiPIP)-like intermediate. The two paramagnetic reaction intermediates observed correspond to the two intermediates proposed in the bioorganometallic mechanism: the early π-complex in which the substrate's 3-CH(2)OH group has rotated away from the reduced iron-sulfur cluster, and the next, η(3)-allyl complex formed after dehydroxylation. No free radical intermediates are observed, and the two paramagnetic intermediates observed do not fit in a Birch reduction-like or ferraoxetane mechanism. Additionally, we show by using EPR spectroscopy and X-ray crystallography that two substrate analogues (4 and 5) follow the same reaction mechanism.
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Affiliation(s)
- Weixue Wang
- Center for Biophysics and Computational Biology, 607 South Mathews Avenue, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
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