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Sharon I, Hilvert D, Schmeing TM. Cyanophycin and its biosynthesis: not hot but very cool. Nat Prod Rep 2023; 40:1479-1497. [PMID: 37231979 DOI: 10.1039/d2np00092j] [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] [Indexed: 05/27/2023]
Abstract
Covering: 1878 to early 2023Cyanophycin is a biopolymer consisting of a poly-aspartate backbone with arginines linked to each Asp sidechain through isopeptide bonds. Cyanophycin is made by cyanophycin synthetase 1 or 2 through ATP-dependent polymerization of Asp and Arg, or β-Asp-Arg, respectively. It is degraded into dipeptides by exo-cyanophycinases, and these dipeptides are hydrolyzed into free amino acids by general or dedicated isodipeptidase enzymes. When synthesized, chains of cyanophycin coalesce into large, inert, membrane-less granules. Although discovered in cyanobacteria, cyanophycin is made by species throughout the bacterial kingdom, and cyanophycin metabolism provides advantages for toxic bloom forming algae and some human pathogens. Some bacteria have developed dedicated schemes for cyanophycin accumulation and use, which include fine temporal and spatial regulation. Cyanophycin has also been heterologously produced in a variety of host organisms to a remarkable level, over 50% of the host's dry mass, and has potential for a variety of green industrial applications. In this review, we summarize the progression of cyanophycin research, with an emphasis on recent structural studies of enzymes in the cyanophycin biosynthetic pathway. These include several unexpected revelations that show cyanophycin synthetase to be a very cool, multi-functional macromolecular machine.
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Affiliation(s)
- Itai Sharon
- Department of Biochemistry and Centre de Recherche en Biologie Structurale, McGill University, Montréal, QC, Canada, H3G 0B1.
| | - Donald Hilvert
- Laboratory of Organic Chemistry, ETH Zürich, CH-8093 Zürich, Switzerland
| | - T Martin Schmeing
- Department of Biochemistry and Centre de Recherche en Biologie Structurale, McGill University, Montréal, QC, Canada, H3G 0B1.
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2
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Sharon I, Grogg M, Hilvert D, Schmeing TM. Structure and Function of the β-Asp-Arg Polymerase Cyanophycin Synthetase 2. ACS Chem Biol 2022; 17:670-679. [PMID: 35179888 DOI: 10.1021/acschembio.1c01007] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Cyanophycin is a biopolymer composed of long chains of β-Asp-Arg. It is widespread in nature, being synthesized by many clades of bacteria, which use it as a cellular reservoir of nitrogen, carbon, and energy. Two enzymes are known to produce cyanophycin: cyanophycin synthetase 1 (CphA1), which builds cyanophycin from the amino acids Asp and Arg by alternating between two separate reactions for backbone extension and side chain modification, and cyanophycin synthetase 2 (CphA2), which polymerizes β-Asp-Arg dipeptides. CphA2 is evolutionarily related to CphA1, but questions about CphA2's altered structure and function remain unresolved. Cyanophycin and related molecules have drawn interest as green biopolymers. Because it only has a single active site, CphA2 could be more useful than CphA1 for biotechnological applications seeking to produce modified cyanophycin. In this study, we report biochemical assays on nine cyanobacterial CphA2 enzymes and report the crystal structure of CphA2 from Gloeothece citriformis at 3.0 Å resolution. The structure reveals a homodimeric, three-domain architecture. One domain harbors the polymerization active site and the two other domains have structural roles. The structure and biochemical assays explain how CphA2 binds and polymerizes β-Asp-Arg and highlights differences in in vitro oligomerization and activity between CphA2 enzymes. Using the structure and distinct activity profile as a guide, we introduced a single point mutation that converted Gloeothece citriformis CphA2 from a primer-dependent enzyme into a primer-independent enzyme.
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Affiliation(s)
- Itai Sharon
- Department of Biochemistry and Centre de recherche en biologie structurale, McGill University, Montréal H3G 0B1, Quebec, Canada
| | - Marcel Grogg
- Laboratory of Organic Chemistry, ETH Zürich, CH-8093 Zürich, Switzerland
| | - Donald Hilvert
- Laboratory of Organic Chemistry, ETH Zürich, CH-8093 Zürich, Switzerland
| | - T. Martin Schmeing
- Department of Biochemistry and Centre de recherche en biologie structurale, McGill University, Montréal H3G 0B1, Quebec, Canada
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3
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Sharon I, Haque AS, Grogg M, Lahiri I, Seebach D, Leschziner AE, Hilvert D, Schmeing TM. Structures and function of the amino acid polymerase cyanophycin synthetase. Nat Chem Biol 2021; 17:1101-1110. [PMID: 34385683 DOI: 10.1038/s41589-021-00854-y] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2021] [Accepted: 07/08/2021] [Indexed: 12/13/2022]
Abstract
Cyanophycin is a natural biopolymer produced by a wide range of bacteria, consisting of a chain of poly-L-Asp residues with L-Arg residues attached to the β-carboxylate sidechains by isopeptide bonds. Cyanophycin is synthesized from ATP, aspartic acid and arginine by a homooligomeric enzyme called cyanophycin synthetase (CphA1). CphA1 has domains that are homologous to glutathione synthetases and muramyl ligases, but no other structural information has been available. Here, we present cryo-electron microscopy and X-ray crystallography structures of cyanophycin synthetases from three different bacteria, including cocomplex structures of CphA1 with ATP and cyanophycin polymer analogs at 2.6 Å resolution. These structures reveal two distinct tetrameric architectures, show the configuration of active sites and polymer-binding regions, indicate dynamic conformational changes and afford insight into catalytic mechanism. Accompanying biochemical interrogation of substrate binding sites, catalytic centers and oligomerization interfaces combine with the structures to provide a holistic understanding of cyanophycin biosynthesis.
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Affiliation(s)
- Itai Sharon
- Department of Biochemistry and Centre de Recherche en Biologie Structurale, McGill University, Montréal, Quebec, Canada
| | - Asfarul S Haque
- Department of Biochemistry and Centre de Recherche en Biologie Structurale, McGill University, Montréal, Quebec, Canada
| | - Marcel Grogg
- Laboratory of Organic Chemistry, ETH Zürich, Zürich, Switzerland
| | - Indrajit Lahiri
- Department of Cellular and Molecular Medicine, and Section of Molecular Biology, Division of Biological Sciences, University of California San Diego (UCSD), La Jolla, CA, USA
| | - Dieter Seebach
- Laboratory of Organic Chemistry, ETH Zürich, Zürich, Switzerland
| | - Andres E Leschziner
- Department of Cellular and Molecular Medicine, and Section of Molecular Biology, Division of Biological Sciences, University of California San Diego (UCSD), La Jolla, CA, USA
| | - Donald Hilvert
- Laboratory of Organic Chemistry, ETH Zürich, Zürich, Switzerland
| | - T Martin Schmeing
- Department of Biochemistry and Centre de Recherche en Biologie Structurale, McGill University, Montréal, Quebec, Canada.
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Jez JM. Structural biology of plant sulfur metabolism: from sulfate to glutathione. JOURNAL OF EXPERIMENTAL BOTANY 2019; 70:4089-4103. [PMID: 30825314 DOI: 10.1093/jxb/erz094] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/07/2019] [Accepted: 02/12/2019] [Indexed: 06/09/2023]
Abstract
Sulfur is an essential element for all organisms. Plants must assimilate this nutrient from the environment and convert it into metabolically useful forms for the biosynthesis of a wide range of compounds, including cysteine and glutathione. This review summarizes structural biology studies on the enzymes involved in plant sulfur assimilation [ATP sulfurylase, adenosine-5'-phosphate (APS) reductase, and sulfite reductase], cysteine biosynthesis (serine acetyltransferase and O-acetylserine sulfhydrylase), and glutathione biosynthesis (glutamate-cysteine ligase and glutathione synthetase) pathways. Overall, X-ray crystal structures of enzymes in these core pathways provide molecular-level information on the chemical events that allow plants to incorporate sulfur into essential metabolites and revealed new biochemical regulatory mechanisms, such as structural rearrangements, protein-protein interactions, and thiol-based redox switches, for controlling different steps in these pathways.
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Affiliation(s)
- Joseph M Jez
- Department of Biology, Washington University in St. Louis, St. Louis, MO, USA
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5
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Škedelj V, Fonović UP, Molek P, Magnet S, Mainardi JL, Blanot D, Gobec S, Stojan J, Zega A. Kinetic mechanism of Enterococcus faecium d-aspartate ligase. Biochimie 2019; 158:217-223. [DOI: 10.1016/j.biochi.2019.01.012] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2018] [Accepted: 01/19/2019] [Indexed: 11/30/2022]
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Lilley CJ, Maqbool A, Wu D, Yusup HB, Jones LM, Birch PRJ, Banfield MJ, Urwin PE, Eves-van den Akker S. Effector gene birth in plant parasitic nematodes: Neofunctionalization of a housekeeping glutathione synthetase gene. PLoS Genet 2018; 14:e1007310. [PMID: 29641602 PMCID: PMC5919673 DOI: 10.1371/journal.pgen.1007310] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2017] [Revised: 04/26/2018] [Accepted: 03/16/2018] [Indexed: 11/24/2022] Open
Abstract
Plant pathogens and parasites are a major threat to global food security. Plant parasitism has arisen four times independently within the phylum Nematoda, resulting in at least one parasite of every major food crop in the world. Some species within the most economically important order (Tylenchida) secrete proteins termed effectors into their host during infection to re-programme host development and immunity. The precise detail of how nematodes evolve new effectors is not clear. Here we reconstruct the evolutionary history of a novel effector gene family. We show that during the evolution of plant parasitism in the Tylenchida, the housekeeping glutathione synthetase (GS) gene was extensively replicated. New GS paralogues acquired multiple dorsal gland promoter elements, altered spatial expression to the secretory dorsal gland, altered temporal expression to primarily parasitic stages, and gained a signal peptide for secretion. The gene products are delivered into the host plant cell during infection, giving rise to "GS-like effectors". Remarkably, by solving the structure of GS-like effectors we show that during this process they have also diversified in biochemical activity, and likely represent the founding members of a novel class of GS-like enzyme. Our results demonstrate the re-purposing of an endogenous housekeeping gene to form a family of effectors with modified functions. We anticipate that our discovery will be a blueprint to understand the evolution of other plant-parasitic nematode effectors, and the foundation to uncover a novel enzymatic function.
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Affiliation(s)
- Catherine J. Lilley
- Centre for Plant Sciences, Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom
| | - Abbas Maqbool
- Dept. of Biological Chemistry, John Innes Centre, Norwich Research Park, Norwich, United Kingdom
| | - Duqing Wu
- Centre for Plant Sciences, Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom
| | - Hazijah B. Yusup
- Centre for Plant Sciences, Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom
| | - Laura M. Jones
- Centre for Plant Sciences, Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom
| | - Paul R. J. Birch
- Cell and Molecular Sciences Group, Dundee Effector Consortium, James Hutton Institute, Invergowrie, Dundee, United Kingdom
- School of Life Sciences, University of Dundee, Dundee, United Kingdom
| | - Mark J. Banfield
- Dept. of Biological Chemistry, John Innes Centre, Norwich Research Park, Norwich, United Kingdom
| | - Peter E. Urwin
- Centre for Plant Sciences, Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom
| | - Sebastian Eves-van den Akker
- Dept. of Biological Chemistry, John Innes Centre, Norwich Research Park, Norwich, United Kingdom
- School of Life Sciences, University of Dundee, Dundee, United Kingdom
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7
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Jez JM, Ravilious GE, Herrmann J. Structural biology and regulation of the plant sulfation pathway. Chem Biol Interact 2016; 259:31-38. [DOI: 10.1016/j.cbi.2016.02.017] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2016] [Revised: 02/16/2016] [Accepted: 02/22/2016] [Indexed: 11/26/2022]
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8
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Wang Y, Xu H, Harich KC, White RH. Identification and Characterization of a Tyramine–Glutamate Ligase (MfnD) Involved in Methanofuran Biosynthesis. Biochemistry 2014; 53:6220-30. [DOI: 10.1021/bi500879h] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Affiliation(s)
- Yu Wang
- Department of Biochemistry, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061, United States
| | - Huimin Xu
- Department of Biochemistry, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061, United States
| | - Kim C. Harich
- Department of Biochemistry, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061, United States
| | - Robert H. White
- Department of Biochemistry, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061, United States
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Preuss ML, Cameron JC, Berg RH, Jez JM. Immunolocalization of glutathione biosynthesis enzymes in Arabidopsis thaliana. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2014; 75:9-13. [PMID: 24361505 DOI: 10.1016/j.plaphy.2013.11.027] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2013] [Accepted: 11/28/2013] [Indexed: 05/12/2023]
Abstract
In plants, glutathione serves as a versatile redox buffer and cellular protective compound against a range of biotic and abiotic stresses. Glutathione production involves glutamate-cysteine ligase (GCL), the redox-regulated limiting enzyme of the pathway, and glutathione synthetase (GS). Because the sub-cellular and sub-organellar localization of these enzymes will have an impact on metabolism, here we examine the localization of GCL and GS in the leaves of Arabidopsis thaliana. Immuno-electron microscopy of leaf cells indicates localization of GCL primarily to the chloroplast with GS found in both the chloroplast and cytosol. Detailed examination of the localization of both enzymes within chloroplasts was performed using fractionation followed by immunoblot analysis and indicates that GCL and GS are found in the stroma. The localization of these enzymes to the stroma of chloroplasts has implications for the redox-regulation of GCL and plant glutathione biosynthesis.
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Affiliation(s)
- Mary L Preuss
- Department of Biological Sciences, Webster University, 470 East Lockwood Ave., WEBH 9A, Webster Groves, MO 63119, USA
| | - Jeffrey C Cameron
- Department of Biology, Washington University, One Brookings Drive, Campus Box 1137, St. Louis, MO 63130, USA
| | - R Howard Berg
- Donald Danforth Plant Science Center, 975 North Warson Rd., St. Louis, MO 63132, USA
| | - Joseph M Jez
- Department of Biology, Washington University, One Brookings Drive, Campus Box 1137, St. Louis, MO 63130, USA.
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10
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Gill SS, Anjum NA, Hasanuzzaman M, Gill R, Trivedi DK, Ahmad I, Pereira E, Tuteja N. Glutathione and glutathione reductase: a boon in disguise for plant abiotic stress defense operations. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2013; 70:204-12. [PMID: 23792825 DOI: 10.1016/j.plaphy.2013.05.032] [Citation(s) in RCA: 234] [Impact Index Per Article: 21.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/09/2013] [Accepted: 05/24/2013] [Indexed: 05/05/2023]
Abstract
Abiotic stresses such as salinity, drought, clilling, heavy metal are the major limiting factors for crop productivity. These stresses induce the overproduction of reactive oxygen species (ROS) which are highly reactive and toxic, which must be minimized to protect the cell from oxidative damage. The cell organelles, particularly chloroplast and mitochondria are the major sites of ROS production in plants where excessive rate of electron flow takes place. Plant cells are well equipped to efficiently scavenge ROS and its reaction products by the coordinated and concerted action of antioxidant machinery constituted by vital enzymatic and non-enzymatic antioxidant components. Glutathione reductase (GR, EC 1.6.4.2) and tripeptide glutathione (GSH, γ-Glutamyl-Cysteinyl-Glycine) are two major components of ascorbate-glutathione (AsA-GSH) pathway which play significant role in protecting cells against ROS and its reaction products-accrued potential anomalies. Both GR and GSH are physiologically linked together where, GR is a NAD(P)H-dependent enzymatic antioxidant and efficiently maintains the reduced pool of GSH - a cellular thiol. The differential modulation of both GR and GSH in plants has been widely implicated for the significance of these two enigmatic antioxidants as major components of plant defense operations. Considering recent informations gained through molecular-genetic studies, the current paper presents an overview of the structure, localization, biosynthesis (for GSH only), discusses GSH and GR significance in abiotic stress (such as salinity, drought, clilling, heavy metal)-exposed crop plants and also points out unexplored aspects in the current context for future studies.
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Affiliation(s)
- Sarvajeet Singh Gill
- Stress Physiology and Molecular Biology Lab, Centre for Biotechnology, Faculty of Life Sciences, MD University, Rohtak 124 001, India.
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11
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Probing the origins of glutathione biosynthesis through biochemical analysis of glutamate-cysteine ligase and glutathione synthetase from a model photosynthetic prokaryote. Biochem J 2013; 450:63-72. [PMID: 23170977 DOI: 10.1042/bj20121332] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Glutathione biosynthesis catalysed by GCL (glutamate-cysteine ligase) and GS (glutathione synthetase) is essential for maintaining redox homoeostasis and protection against oxidative damage in diverse eukaroytes and bacteria. This biosynthetic pathway probably evolved in cyanobacteria with the advent of oxygenic photosynthesis, but the biochemical characteristics of progenitor GCLs and GSs in these organisms are largely unexplored. In the present study we examined SynGCL and SynGS from Synechocystis sp. PCC 6803 using steady-state kinetics. Although SynGCL shares ~15% sequence identity with the enzyme from plants and α-proteobacteria, sequence comparison suggests that these enzymes share similar active site residues. Biochemically, SynGCL lacks the redox regulation associated with the plant enzymes and functions as a monomeric protein, indicating that evolution of redox regulation occurred later in the green lineage. Site-directed mutagenesis of SynGCL establishes this enzyme as part of the plant-like GCL family and identifies a catalytically essential arginine residue, which is structurally conserved across all forms of GCLs, including those from non-plant eukaryotes and γ-proteobacteria. A reaction mechanism for the synthesis of γ-glutamylcysteine by GCLs is proposed. Biochemical and kinetic analysis of SynGS reveals that this enzyme shares properties with other prokaryotic GSs. Initial velocity and product inhibition studies used to examine the kinetic mechanism of SynGS suggest that it and other prokaryotic GSs uses a random ter-reactant mechanism for the synthesis of glutathione. The present study provides new insight on the molecular mechanisms and evolution of glutathione biosynthesis; a key process required for enhancing bioenergy production in photosynthetic organisms.
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Ravilious GE, Jez JM. Structural biology of plant sulfur metabolism: From assimilation to biosynthesis. Nat Prod Rep 2012; 29:1138-52. [DOI: 10.1039/c2np20009k] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
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13
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He Y, Galant A, Pang Q, Strul JM, Balogun SF, Jez JM, Chen S. Structural and functional evolution of isopropylmalate dehydrogenases in the leucine and glucosinolate pathways of Arabidopsis thaliana. J Biol Chem 2011; 286:28794-28801. [PMID: 21697089 DOI: 10.1074/jbc.m111.262519] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The methionine chain-elongation pathway is required for aliphatic glucosinolate biosynthesis in plants and evolved from leucine biosynthesis. In Arabidopsis thaliana, three 3-isopropylmalate dehydrogenases (AtIPMDHs) play key roles in methionine chain-elongation for the synthesis of aliphatic glucosinolates (e.g. AtIPMDH1) and leucine (e.g. AtIPMDH2 and AtIPMDH3). Here we elucidate the molecular basis underlying the metabolic specialization of these enzymes. The 2.25 Å resolution crystal structure of AtIPMDH2 was solved to provide the first detailed molecular architecture of a plant IPMDH. Modeling of 3-isopropylmalate binding in the AtIPMDH2 active site and sequence comparisons of prokaryotic and eukaryotic IPMDH suggest that substitution of one active site residue may lead to altered substrate specificity and metabolic function. Site-directed mutagenesis of Phe-137 to a leucine in AtIPMDH1 (AtIPMDH1-F137L) reduced activity toward 3-(2'-methylthio)ethylmalate by 200-fold, but enhanced catalytic efficiency with 3-isopropylmalate to levels observed with AtIPMDH2 and AtIPMDH3. Conversely, the AtIPMDH2-L134F and AtIPMDH3-L133F mutants enhanced catalytic efficiency with 3-(2'-methylthio)ethylmalate ∼100-fold and reduced activity for 3-isopropylmalate. Furthermore, the altered in vivo glucosinolate profile of an Arabidopsis ipmdh1 T-DNA knock-out mutant could be restored to wild-type levels by constructs expressing AtIPMDH1, AtIPMDH2-L134F, or AtIPMDH3-L133F, but not by AtIPMDH1-F137L. These results indicate that a single amino acid substitution results in functional divergence of IPMDH in planta to affect substrate specificity and contributes to the evolution of specialized glucosinolate biosynthesis from the ancestral leucine pathway.
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Affiliation(s)
- Yan He
- Department of Biology, Genetics Institute, Plant Molecular, and Cellular Biology Program, University of Florida, Gainesville, Florida 32610 and
| | - Ashley Galant
- Department of Biology, Washington University, St. Louis, Missouri 63130
| | - Qiuying Pang
- Department of Biology, Genetics Institute, Plant Molecular, and Cellular Biology Program, University of Florida, Gainesville, Florida 32610 and
| | - Johanna M Strul
- Department of Biology, Genetics Institute, Plant Molecular, and Cellular Biology Program, University of Florida, Gainesville, Florida 32610 and
| | | | - Joseph M Jez
- Department of Biology, Washington University, St. Louis, Missouri 63130
| | - Sixue Chen
- Department of Biology, Genetics Institute, Plant Molecular, and Cellular Biology Program, University of Florida, Gainesville, Florida 32610 and.
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Jez JM. Toward protein engineering for phytoremediation: possibilities and challenges. INTERNATIONAL JOURNAL OF PHYTOREMEDIATION 2011; 13 Suppl 1:77-89. [PMID: 22046752 DOI: 10.1080/15226514.2011.568537] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The combination of rational protein engineering and directed evolution techniques allow for the redesign of enzymes with tailored properties for use in environmental remediation. This review summarizes current molecular methods for either altering or improving protein function and highlights examples of how these methods can address bioremediation problems. Although much of the protein engineering applied to environmental clean-up employs microbial systems, there is great potential for and significant challenges to translating these approaches to plant systems for phytoremediation purposes. Protein engineering technologies combined with genomic information and metabolic engineering strategies hold promise for the design of plants and microbes to remediate organic and inorganic pollutants.
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Affiliation(s)
- Joseph M Jez
- Department of Biology, Washington University, St. Louis, Missouri 63130, USA.
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15
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Galant A, Preuss ML, Cameron JC, Jez JM. Plant glutathione biosynthesis: diversity in biochemical regulation and reaction products. FRONTIERS IN PLANT SCIENCE 2011; 2:45. [PMID: 22645536 PMCID: PMC3355797 DOI: 10.3389/fpls.2011.00045] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/02/2011] [Accepted: 08/16/2011] [Indexed: 05/19/2023]
Abstract
In plants, exposure to temperature extremes, heavy metal-contaminated soils, drought, air pollutants, and pathogens results in the generation of reactive oxygen species that alter the intracellular redox environment, which in turn influences signaling pathways and cell fate. As part of their response to these stresses, plants produce glutathione. Glutathione acts as an anti-oxidant by quenching reactive oxygen species, and is involved in the ascorbate-glutathione cycle that eliminates damaging peroxides. Plants also use glutathione for the detoxification of xenobiotics, herbicides, air pollutants (sulfur dioxide and ozone), and toxic heavy metals. Two enzymes catalyze glutathione synthesis: glutamate-cysteine ligase, and glutathione synthetase. Glutathione is a ubiquitous protective compound in plants, but the structural and functional details of the proteins that synthesize it, as well as the potential biochemical mechanisms of their regulation, have only begun to be explored. As discussed here, the core reactions of glutathione synthesis are conserved across various organisms, but plants have diversified both the regulatory mechanisms that control its synthesis and the range of products derived from this pathway. Understanding the molecular basis of glutathione biosynthesis and its regulation will expand our knowledge of this component in the plant stress response network.
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Affiliation(s)
- Ashley Galant
- Department of Biology, Washington University in St. LouisSt. Louis, MO, USA
| | - Mary L. Preuss
- Department of Biological Sciences, Webster UniversityWebster Groves, MO, USA
| | - Jeffrey C. Cameron
- Department of Biology, Washington University in St. LouisSt. Louis, MO, USA
| | - Joseph M. Jez
- Department of Biology, Washington University in St. LouisSt. Louis, MO, USA
- *Correspondence: Joseph M. Jez, Department of Biology, Washington University in St. Louis, One Brookings Drive, Campus Box 1137, St. Louis, MO 63130, USA. e-mail:
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16
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Yi H, Ravilious GE, Galant A, Krishnan HB, Jez JM. From sulfur to homoglutathione: thiol metabolism in soybean. Amino Acids 2010; 39:963-78. [PMID: 20364282 DOI: 10.1007/s00726-010-0572-9] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2009] [Accepted: 03/16/2010] [Indexed: 12/11/2022]
Abstract
Sulfur is an essential plant nutrient and is metabolized into the sulfur-containing amino acids (cysteine and methionine) and into molecules that protect plants against oxidative and environmental stresses. Although studies of thiol metabolism in the model plant Arabidopsis thaliana (thale cress) have expanded our understanding of these dynamic processes, our knowledge of how sulfur is assimilated and metabolized in crop plants, such as soybean (Glycine max), remains limited in comparison. Soybean is a major crop used worldwide for food and animal feed. Although soybeans are protein-rich, they do not contain high levels of the sulfur-containing amino acids, cysteine and methionine. Ultimately, unraveling the fundamental steps and regulation of thiol metabolism in soybean is important for optimizing crop yield and quality. Here we review the pathways from sulfur uptake to glutathione and homoglutathione synthesis in soybean, the potential biotechnology benefits of understanding and modifying these pathways, and how information from the soybean genome may guide the next steps in exploring this biochemical system.
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Affiliation(s)
- Hankuil Yi
- Department of Biology, Washington University, St. Louis, MO 63130, USA
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17
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Biterova EI, Barycki JJ. Structural basis for feedback and pharmacological inhibition of Saccharomyces cerevisiae glutamate cysteine ligase. J Biol Chem 2010; 285:14459-66. [PMID: 20220146 DOI: 10.1074/jbc.m110.104802] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Structural characterization of glutamate cysteine ligase (GCL), the enzyme that catalyzes the initial, rate-limiting step in glutathione biosynthesis, has revealed many of the molecular details of substrate recognition. To further delineate the mechanistic details of this critical enzyme, we have determined the structures of two inhibited forms of Saccharomyces cerevisiae GCL (ScGCL), which shares significant sequence identity with the human enzyme. In vivo, GCL activity is feedback regulated by glutathione. Examination of the structure of ScGCL-glutathione complex (2.5 A; R = 19.9%, R(free) = 25.1%) indicates that the inhibitor occupies both the glutamate- and the presumed cysteine-binding site and disrupts the previously observed Mg(2+) coordination in the ATP-binding site. l-Buthionine-S-sulfoximine (BSO) is a mechanism-based inhibitor of GCL and has been used extensively to deplete glutathione in cell culture and in vivo model systems. Inspection of the ScGCL-BSO structure (2.2 A; R = 18.1%, R(free) = 23.9%) confirms that BSO is phosphorylated on the sulfoximine nitrogen to generate the inhibitory species and reveals contacts that likely contribute to transition state stabilization. Overall, these structures advance our understanding of the molecular regulation of this critical enzyme and provide additional details of the catalytic mechanism of the enzyme.
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Affiliation(s)
- Ekaterina I Biterova
- Department of Biochemistry and the Redox Biology Center, University of Nebraska, Lincoln, Nebraska 68588, USA
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Yi H, Galant A, Ravilious GE, Preuss ML, Jez JM. Sensing sulfur conditions: simple to complex protein regulatory mechanisms in plant thiol metabolism. MOLECULAR PLANT 2010; 3:269-79. [PMID: 20080815 DOI: 10.1093/mp/ssp112] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
Sulfur is essential for plant growth and development, and the molecular systems for maintaining sulfur and thiol metabolism are tightly controlled. From a biochemical perspective, the regulation of plant thiol metabolism highlights nature's ability to engineer pathways that respond to multiple inputs and cellular demands under a range of conditions. In this review, we focus on the regulatory mechanisms that form the molecular basis of biochemical sulfur sensing in plants by translating the intracellular concentration of sulfur-containing compounds into control of key metabolic steps. These mechanisms range from the simple (substrate availability, thermodynamic properties of reactions, feedback inhibition, and organelle localization) to the elaborate (formation of multienzyme complexes and thiol-based redox switches). Ultimately, the dynamic interplay of these regulatory systems is critical for sensing and maintaining sulfur assimilation and thiol metabolism in plants.
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Affiliation(s)
- Hankuil Yi
- Department of Biology, Washington University, St Louis, MO 63130, USA
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