1
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Tran JU, Brown BL. The yeast ALA synthase C-terminus positively controls enzyme structure and function. Protein Sci 2023; 32:e4600. [PMID: 36807942 PMCID: PMC10031213 DOI: 10.1002/pro.4600] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2022] [Revised: 02/07/2023] [Accepted: 02/15/2023] [Indexed: 02/23/2023]
Abstract
5-Aminolevulinic acid synthase (ALAS) is a pyridoxal 5'-phosphate (PLP)-dependent enzyme that catalyzes the first and rate-limiting step of heme biosynthesis in α-proteobacteria and several non-plant eukaryotes. All ALAS homologs contain a highly conserved catalytic core, but eukaryotes also have a unique C-terminal extension that plays a role in enzyme regulation. Several mutations in this region are implicated in multiple blood disorders in humans. In Saccharomyces cerevisiae ALAS (Hem1), the C-terminal extension wraps around the homodimer core to contact conserved ALAS motifs proximal to the opposite active site. To determine the importance of these Hem1 C-terminal interactions, we determined the crystal structure of S. cerevisiae Hem1 lacking the terminal 14 amino acids (Hem1 ΔCT). With truncation of the C-terminal extension, we show structurally and biochemically that multiple catalytic motifs become flexible, including an antiparallel β-sheet important to Fold-Type I PLP-dependent enzymes. The changes in protein conformation result in an altered cofactor microenvironment, decreased enzyme activity and catalytic efficiency, and ablation of subunit cooperativity. These findings suggest that the eukaryotic ALAS C-terminus has a homolog-specific role in mediating heme biosynthesis, indicating a mechanism for autoregulation that can be exploited to allosterically modulate heme biosynthesis in different organisms.
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Affiliation(s)
- Jenny U. Tran
- Department of BiochemistryVanderbilt University School of MedicineNashvilleTennesseeUSA
| | - Breann L. Brown
- Department of BiochemistryVanderbilt University School of MedicineNashvilleTennesseeUSA
- Center for Structural BiologyVanderbilt University School of MedicineNashvilleTennesseeUSA
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2
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Pu W, Chen J, Zhou Y, Qiu H, Shi T, Zhou W, Guo X, Cai N, Tan Z, Liu J, Feng J, Wang Y, Zheng P, Sun J. Systems metabolic engineering of Escherichia coli for hyper-production of 5‑aminolevulinic acid. BIOTECHNOLOGY FOR BIOFUELS AND BIOPRODUCTS 2023; 16:31. [PMID: 36829220 PMCID: PMC9951541 DOI: 10.1186/s13068-023-02280-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/13/2022] [Accepted: 02/09/2023] [Indexed: 02/26/2023]
Abstract
BACKGROUND 5-Aminolevulinic acid (5-ALA) is a promising biostimulant, feed nutrient, and photodynamic drug with wide applications in modern agriculture and therapy. Although microbial production of 5-ALA has been improved realized by using metabolic engineering strategies during the past few years, there is still a gap between the present production level and the requirement of industrialization. RESULTS In this study, pathway, protein, and cellular engineering strategies were systematically employed to construct an industrially competitive 5-ALA producing Escherichia coli. Pathways involved in precursor supply and product degradation were regulated by gene overexpression and synthetic sRNA-based repression to channel metabolic flux to 5-ALA biosynthesis. 5-ALA synthase was rationally engineered to release the inhibition of heme and improve the catalytic activity. 5-ALA transport and antioxidant defense systems were targeted to enhance cellular tolerance to intra- and extra-cellular 5-ALA. The final engineered strain produced 30.7 g/L of 5-ALA in bioreactors with a productivity of 1.02 g/L/h and a yield of 0.532 mol/mol glucose, represent a new record of 5-ALA bioproduction. CONCLUSIONS An industrially competitive 5-ALA producing E. coli strain was constructed with the metabolic engineering strategies at multiple layers (protein, pathway, and cellular engineering), and the strategies here can be useful for developing industrial-strength strains for biomanufacturing.
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Affiliation(s)
- Wei Pu
- grid.458513.e0000 0004 1763 3963Key Laboratory of Systems Microbial Biotechnology, Chinese Academy of Sciences, Tianjin Institute of Industrial Biotechnology, Tianjin, 300308 China ,National Technology Innovation Center of Synthetic Biology, Tianjin, 300308 China
| | - Jiuzhou Chen
- grid.458513.e0000 0004 1763 3963Key Laboratory of Systems Microbial Biotechnology, Chinese Academy of Sciences, Tianjin Institute of Industrial Biotechnology, Tianjin, 300308 China ,National Technology Innovation Center of Synthetic Biology, Tianjin, 300308 China
| | - Yingyu Zhou
- grid.458513.e0000 0004 1763 3963Key Laboratory of Systems Microbial Biotechnology, Chinese Academy of Sciences, Tianjin Institute of Industrial Biotechnology, Tianjin, 300308 China ,grid.413109.e0000 0000 9735 6249College of Biotechnology, Tianjin University of Science and Technology, Tianjin, 300457 China
| | - Huamin Qiu
- grid.458513.e0000 0004 1763 3963Key Laboratory of Systems Microbial Biotechnology, Chinese Academy of Sciences, Tianjin Institute of Industrial Biotechnology, Tianjin, 300308 China ,grid.410726.60000 0004 1797 8419University of Chinese Academy of Sciences, Beijing, 100049 China
| | - Tuo Shi
- grid.458513.e0000 0004 1763 3963Key Laboratory of Systems Microbial Biotechnology, Chinese Academy of Sciences, Tianjin Institute of Industrial Biotechnology, Tianjin, 300308 China ,National Technology Innovation Center of Synthetic Biology, Tianjin, 300308 China
| | - Wenjuan Zhou
- grid.458513.e0000 0004 1763 3963Key Laboratory of Systems Microbial Biotechnology, Chinese Academy of Sciences, Tianjin Institute of Industrial Biotechnology, Tianjin, 300308 China ,National Technology Innovation Center of Synthetic Biology, Tianjin, 300308 China
| | - Xuan Guo
- grid.458513.e0000 0004 1763 3963Key Laboratory of Systems Microbial Biotechnology, Chinese Academy of Sciences, Tianjin Institute of Industrial Biotechnology, Tianjin, 300308 China ,National Technology Innovation Center of Synthetic Biology, Tianjin, 300308 China
| | - Ningyun Cai
- grid.458513.e0000 0004 1763 3963Key Laboratory of Systems Microbial Biotechnology, Chinese Academy of Sciences, Tianjin Institute of Industrial Biotechnology, Tianjin, 300308 China ,grid.413109.e0000 0000 9735 6249College of Biotechnology, Tianjin University of Science and Technology, Tianjin, 300457 China
| | - Zijian Tan
- grid.458513.e0000 0004 1763 3963Key Laboratory of Systems Microbial Biotechnology, Chinese Academy of Sciences, Tianjin Institute of Industrial Biotechnology, Tianjin, 300308 China ,National Technology Innovation Center of Synthetic Biology, Tianjin, 300308 China
| | - Jiao Liu
- grid.458513.e0000 0004 1763 3963Key Laboratory of Systems Microbial Biotechnology, Chinese Academy of Sciences, Tianjin Institute of Industrial Biotechnology, Tianjin, 300308 China ,National Technology Innovation Center of Synthetic Biology, Tianjin, 300308 China
| | - Jinhui Feng
- grid.458513.e0000 0004 1763 3963Key Laboratory of Systems Microbial Biotechnology, Chinese Academy of Sciences, Tianjin Institute of Industrial Biotechnology, Tianjin, 300308 China ,National Technology Innovation Center of Synthetic Biology, Tianjin, 300308 China
| | - Yu Wang
- Key Laboratory of Systems Microbial Biotechnology, Chinese Academy of Sciences, Tianjin Institute of Industrial Biotechnology, Tianjin, 300308, China. .,National Technology Innovation Center of Synthetic Biology, Tianjin, 300308, China. .,University of Chinese Academy of Sciences, Beijing, 100049, China.
| | - Ping Zheng
- Key Laboratory of Systems Microbial Biotechnology, Chinese Academy of Sciences, Tianjin Institute of Industrial Biotechnology, Tianjin, 300308, China. .,National Technology Innovation Center of Synthetic Biology, Tianjin, 300308, China. .,University of Chinese Academy of Sciences, Beijing, 100049, China.
| | - Jibin Sun
- grid.458513.e0000 0004 1763 3963Key Laboratory of Systems Microbial Biotechnology, Chinese Academy of Sciences, Tianjin Institute of Industrial Biotechnology, Tianjin, 300308 China ,National Technology Innovation Center of Synthetic Biology, Tianjin, 300308 China ,grid.410726.60000 0004 1797 8419University of Chinese Academy of Sciences, Beijing, 100049 China
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3
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Tran JU, Brown BL. Structural Basis for Allostery in PLP-dependent Enzymes. Front Mol Biosci 2022; 9:884281. [PMID: 35547395 PMCID: PMC9081730 DOI: 10.3389/fmolb.2022.884281] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2022] [Accepted: 03/25/2022] [Indexed: 11/13/2022] Open
Abstract
Pyridoxal 5'-phosphate (PLP)-dependent enzymes are found ubiquitously in nature and are involved in a variety of biological pathways, from natural product synthesis to amino acid and glucose metabolism. The first structure of a PLP-dependent enzyme was reported over 40 years ago, and since that time, there is a steady wealth of structural and functional information revealed for a wide array of these enzymes. A functional mechanism that is gaining more appreciation due to its relevance in drug design is that of protein allostery, where binding of a protein or ligand at a distal site influences the structure, organization, and function at the active site. Here, we present a review of current structure-based mechanisms of allostery for select members of each PLP-dependent enzyme family. Knowledge of these mechanisms may have a larger potential for identifying key similarities and differences among enzyme families that can eventually be exploited for therapeutic development.
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Affiliation(s)
- Jenny U. Tran
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN, United States
| | - Breann L. Brown
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN, United States
- Center for Structural Biology, Vanderbilt University School of Medicine, Nashville, TN, United States
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4
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Bailey HJ, Bezerra GA, Marcero JR, Padhi S, Foster WR, Rembeza E, Roy A, Bishop DF, Desnick RJ, Bulusu G, Dailey HA, Yue WW. Human aminolevulinate synthase structure reveals a eukaryotic-specific autoinhibitory loop regulating substrate binding and product release. Nat Commun 2020; 11:2813. [PMID: 32499479 PMCID: PMC7272653 DOI: 10.1038/s41467-020-16586-x] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2019] [Accepted: 05/11/2020] [Indexed: 12/12/2022] Open
Abstract
5'-aminolevulinate synthase (ALAS) catalyzes the first step in heme biosynthesis, generating 5'-aminolevulinate from glycine and succinyl-CoA. Inherited frameshift indel mutations of human erythroid-specific isozyme ALAS2, within a C-terminal (Ct) extension of its catalytic core that is only present in higher eukaryotes, lead to gain-of-function X-linked protoporphyria (XLP). Here, we report the human ALAS2 crystal structure, revealing that its Ct-extension folds onto the catalytic core, sits atop the active site, and precludes binding of substrate succinyl-CoA. The Ct-extension is therefore an autoinhibitory element that must re-orient during catalysis, as supported by molecular dynamics simulations. Our data explain how Ct deletions in XLP alleviate autoinhibition and increase enzyme activity. Crystallography-based fragment screening reveals a binding hotspot around the Ct-extension, where fragments interfere with the Ct conformational dynamics and inhibit ALAS2 activity. These fragments represent a starting point to develop ALAS2 inhibitors as substrate reduction therapy for porphyria disorders that accumulate toxic heme intermediates.
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Affiliation(s)
- Henry J Bailey
- Structural Genomics Consortium, Nuffield Department of Medicine, University of Oxford, Oxford, OX3 7DQ, UK
| | - Gustavo A Bezerra
- Structural Genomics Consortium, Nuffield Department of Medicine, University of Oxford, Oxford, OX3 7DQ, UK
| | - Jason R Marcero
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA, 30602, USA
| | - Siladitya Padhi
- TCS Innovation Labs-Hyderabad (Life Sciences Division), Tata Consultancy Services Ltd, Hyderabad, 500081, India
| | - William R Foster
- Structural Genomics Consortium, Nuffield Department of Medicine, University of Oxford, Oxford, OX3 7DQ, UK
| | - Elzbieta Rembeza
- Structural Genomics Consortium, Nuffield Department of Medicine, University of Oxford, Oxford, OX3 7DQ, UK
| | - Arijit Roy
- TCS Innovation Labs-Hyderabad (Life Sciences Division), Tata Consultancy Services Ltd, Hyderabad, 500081, India
| | - David F Bishop
- Department of Genetics and Genomics Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, 10029, USA
| | - Robert J Desnick
- Department of Genetics and Genomics Sciences, Icahn School of Medicine at Mount Sinai, New York, NY, 10029, USA
| | - Gopalakrishnan Bulusu
- TCS Innovation Labs-Hyderabad (Life Sciences Division), Tata Consultancy Services Ltd, Hyderabad, 500081, India
| | - Harry A Dailey
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA, 30602, USA
| | - Wyatt W Yue
- Structural Genomics Consortium, Nuffield Department of Medicine, University of Oxford, Oxford, OX3 7DQ, UK.
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5
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Stojanovski BM, Hunter GA, Na I, Uversky VN, Jiang RHY, Ferreira GC. 5-Aminolevulinate synthase catalysis: The catcher in heme biosynthesis. Mol Genet Metab 2019; 128:178-189. [PMID: 31345668 PMCID: PMC6908770 DOI: 10.1016/j.ymgme.2019.06.003] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/19/2019] [Revised: 05/27/2019] [Accepted: 06/07/2019] [Indexed: 01/26/2023]
Abstract
5-Aminolevulinate (ALA) synthase (ALAS), a homodimeric pyridoxal-5'-phosphate (PLP)-dependent enzyme, catalyzes the first step of heme biosynthesis in metazoa, fungi and α-proteobacteria. In this review, we focus on the advances made in unraveling the mechanism of the ALAS-catalyzed reaction during the past decade. The interplay between the PLP cofactor and the protein moiety determines and modulates the multi-intermediate reaction cycle of ALAS, which involves the decarboxylative condensation of two substrates, glycine and succinyl-CoA. Substrate binding and catalysis are rapid, and product (ALA) release dominates the overall ALAS kinetic mechanism. Interconversion between a catalytically incompetent, open conformation and a catalytically competent, closed conformation is linked to ALAS catalysis. Reversion to the open conformation, coincident with ALA dissociation, defines the slowest step of the reaction cycle. These findings were further substantiated by introducing seven mutations in the16-amino acid loop that gates the active site, yielding an ALAS variant with a greatly increased rate of catalytic turnover and heightened specificity constants for both substrates. Recently, molecular dynamics (MD) simulation analysis of various dimeric ALAS forms revealed that the seven active site loop mutations caused the proteins to adopt different conformations. In particular, the emergence of a β-strand in the mutated loop, which interacted with two preexisting β-strands to form an anti-parallel three-stranded β-sheet, conferred the murine heptavariant with a more stable open conformation and prompted faster product release than wild-type mALAS2. Moreover, the dynamics of the mALAS2 active site loop anti-correlated with that of the 35 amino acid C-terminal sequence. This led us to propose that this C-terminal extension, which is absent in prokaryotic ALASs, finely tunes mammalian ALAS activity. Based on the above results, we extend our previous proposal to include that discovery of a ligand inducing the mammalian C-terminal extension to fold offers a good prospect for the development of a new drug for X-linked protoporphyria and/or other porphyrias associated with enhanced ALAS activity and/or porphyrin accumulation.
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Affiliation(s)
- Bosko M Stojanovski
- Department of Molecular Medicine, Morsani College of Medicine, University of South Florida, Tampa, FL 33612, USA.
| | - Gregory A Hunter
- Department of Molecular Medicine, Morsani College of Medicine, University of South Florida, Tampa, FL 33612, USA
| | - Insung Na
- Department of Molecular Medicine, Morsani College of Medicine, University of South Florida, Tampa, FL 33612, USA.
| | - Vladimir N Uversky
- Department of Molecular Medicine, Morsani College of Medicine, University of South Florida, Tampa, FL 33612, USA; USF Health Byrd Alzheimer's Research Institute, Morsani College of Medicine, University of South Florida, Tampa, FL 33612, USA; Institute for Biological Instrumentation of the Russian Academy of Sciences, Pushchino, Moscow region 142290, Russia
| | - Rays H Y Jiang
- Department of Global Health, College of Public Health, University of South Florida, Tampa, FL 33612, USA
| | - Gloria C Ferreira
- Department of Molecular Medicine, Morsani College of Medicine, University of South Florida, Tampa, FL 33612, USA; Department of Global Health, College of Public Health, University of South Florida, Tampa, FL 33612, USA; Department of Chemistry, College of Arts and Sciences, University of South Florida, Tampa, FL 33612, USA.
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6
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Molecular expression, characterization and mechanism of ALAS2 gain-of-function mutants. Mol Med 2019; 25:4. [PMID: 30678654 PMCID: PMC6344999 DOI: 10.1186/s10020-019-0070-9] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2018] [Accepted: 01/02/2019] [Indexed: 11/13/2022] Open
Abstract
Background X-linked protoporphyria (XLP) (MIM 300752) is an erythropoietic porphyria due to gain-of-function mutations in the last exon (Ducamp et al., Hum Mol Genet 22:1280-88, 2013) of the erythroid-specific aminolevulinate synthase gene (ALAS2). Five ALAS2 exon 11 variants identified by the NHBLI Exome sequencing project (p.R559H, p.E565D, p.R572C, p.S573F and p.Y586F) were expressed, purified and characterized in order to assess their possible contribution to XLP. To further characterize the XLP gain-of-function region, five novel ALAS2 truncation mutations (p.P561X, p.V562X, p.H563X, p.E569X and p.F575X) were also expressed and studied. Methods Site-directed mutagenesis was used to generate ALAS2 mutant clones and all were prokaryotically expressed, purified to near homogeneity and characterized by protein and enzyme kinetic assays. Standard deviations were calculated for 3 or more assay replicates. Results The five ALAS2 single nucleotide variants had from 1.3- to 1.9-fold increases in succinyl-CoA Vmax and 2- to 3-fold increases in thermostability suggesting that most could be gain-of-function modifiers of porphyria instead of causes. One SNP (p.R559H) had markedly low purification yield indicating enzyme instability as the likely cause for XLSA in an elderly patient with x-linked sideroblastic anemia. The five novel ALAS2 truncation mutations had increased Vmax values for both succinyl-CoA and glycine substrates (1.4 to 5.6-fold over wild-type), while the Kms for both substrates were only modestly changed. Of interest, the thermostabilities of the truncated ALAS2 mutants were significantly lower than wild-type, with an inverse relationship to Vmax fold-increase. Conclusions Patients with porphyrias should always be assessed for the presence of the ALAS2 gain-of-function modifier variants identified here. A key region of the ALAS2 carboxyterminal region is identified by the truncation mutations studied here and the correlation of increased thermolability with activity suggests that increased molecular flexibility/active site openness is the mechanism of enhanced function of mutations in this region providing further insights into the role of the carboxyl-terminal region of ALAS2 in the regulation of erythroid heme synthesis. Electronic supplementary material The online version of this article (10.1186/s10020-019-0070-9) contains supplementary material, which is available to authorized users.
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7
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Anti-Correlation between the Dynamics of the Active Site Loop and C-Terminal Tail in Relation to the Homodimer Asymmetry of the Mouse Erythroid 5-Aminolevulinate Synthase. Int J Mol Sci 2018; 19:ijms19071899. [PMID: 29958424 PMCID: PMC6073955 DOI: 10.3390/ijms19071899] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2018] [Revised: 06/21/2018] [Accepted: 06/22/2018] [Indexed: 11/17/2022] Open
Abstract
Biosynthesis of heme represents a complex process that involves multiple stages controlled by different enzymes. The first of these proteins is a pyridoxal 5′-phosphate (PLP)-dependent homodimeric enzyme, 5-aminolevulinate synthase (ALAS), that catalyzes the rate-limiting step in heme biosynthesis, the condensation of glycine with succinyl-CoA. Genetic mutations in human erythroid-specific ALAS (ALAS2) are associated with two inherited blood disorders, X-linked sideroblastic anemia (XLSA) and X-linked protoporphyria (XLPP). XLSA is caused by diminished ALAS2 activity leading to decreased ALA and heme syntheses and ultimately ineffective erythropoiesis, whereas XLPP results from “gain-of-function” ALAS2 mutations and consequent overproduction of protoporphyrin IX and increase in Zn2+-protoporphyrin levels. All XLPP-linked mutations affect the intrinsically disordered C-terminal tail of ALAS2. Our earlier molecular dynamics (MD) simulation-based analysis showed that the activity of ALAS2 could be regulated by the conformational flexibility of the active site loop whose structural features and dynamics could be changed due to mutations. We also revealed that the dynamic behavior of the two protomers of the ALAS2 dimer differed. However, how the structural dynamics of ALAS2 active site loop and C-terminal tail dynamics are related to each other and contribute to the homodimer asymmetry remained unanswered questions. In this study, we used bioinformatics and computational biology tools to evaluate the role(s) of the C-terminal tail dynamics in the structure and conformational dynamics of the murine ALAS2 homodimer active site loop. To assess the structural correlation between these two regions, we analyzed their structural displacements and determined their degree of correlation. Here, we report that the dynamics of ALAS2 active site loop is anti-correlated with the dynamics of the C-terminal tail and that this anti-correlation can represent a molecular basis for the functional and dynamic asymmetry of the ALAS2 homodimer.
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8
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Brown BL, Kardon JR, Sauer RT, Baker TA. Structure of the Mitochondrial Aminolevulinic Acid Synthase, a Key Heme Biosynthetic Enzyme. Structure 2018; 26:580-589.e4. [PMID: 29551290 DOI: 10.1016/j.str.2018.02.012] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2017] [Revised: 11/30/2017] [Accepted: 02/09/2018] [Indexed: 01/19/2023]
Abstract
5-Aminolevulinic acid synthase (ALAS) catalyzes the first step in heme biosynthesis. We present the crystal structure of a eukaryotic ALAS from Saccharomyces cerevisiae. In this homodimeric structure, one ALAS subunit contains covalently bound cofactor, pyridoxal 5'-phosphate (PLP), whereas the second is PLP free. Comparison between the subunits reveals PLP-coupled reordering of the active site and of additional regions to achieve the active conformation of the enzyme. The eukaryotic C-terminal extension, a region altered in multiple human disease alleles, wraps around the dimer and contacts active-site-proximal residues. Mutational analysis demonstrates that this C-terminal region that engages the active site is important for ALAS activity. Our discovery of structural elements that change conformation upon PLP binding and of direct contact between the C-terminal extension and the active site thus provides a structural basis for investigation of disruptions in the first step of heme biosynthesis and resulting human disorders.
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Affiliation(s)
- Breann L Brown
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Julia R Kardon
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA; Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Robert T Sauer
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Tania A Baker
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA; Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
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9
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Liu J, Kaganjo J, Zhang W, Zeilstra-Ryalls J. Investigating the bifunctionality of cyclizing and "classical" 5-aminolevulinate synthases. Protein Sci 2017; 27:402-410. [PMID: 29027286 DOI: 10.1002/pro.3324] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2017] [Revised: 10/10/2017] [Accepted: 10/10/2017] [Indexed: 11/07/2022]
Abstract
The precursor to all tetrapyrroles is 5-aminolevulinic acid, which is made either via the condensation of glycine and succinyl-CoA catalyzed by an ALA synthase (the C4 or Shemin pathway) or by a pathway that uses glutamyl-tRNA as a precursor and involves other enzymes (the C5 pathway). Certain ALA synthases also catalyze the cyclization of ALA-CoA to form 2-amino-3-hydroxycyclopent-2-en-1-one. Organisms with synthases that possess this second activity nevertheless rely upon the C5 pathway to supply ALA for tetrapyrrole biosynthesis. The C5 N units are components of a variety of secondary metabolites. Here, we show that an ALA synthase used exclusively for tetrapyrrole biosynthesis is also capable of catalyzing the cyclization reaction, albeit at much lower efficiency than the dedicated cyclases. Two absolutely conserved serines present in all known ALA-CoA cyclases are threonines in all known ALA synthases, suggesting they could be important in distinguishing the functions of these enzymes. We found that purified mutant proteins having single and double substitutions of the conserved residues are not improved in their respective alternate activities; rather, they are worse. Protein structural modeling and amino acid sequence alignments were explored within the context of what is known about the reaction mechanisms of these two different types of enzymes to consider what other features are important for the two activities.
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Affiliation(s)
- Joyce Liu
- Department of Bioengineering, University of California, Berkeley, California
| | - James Kaganjo
- Department of Biological Sciences, Bowling Green State University, Bowling Green, Ohio
| | - Wenjun Zhang
- Department of Chemical and Biomolecular Engineering, University of California, Berkeley, California
| | - Jill Zeilstra-Ryalls
- Department of Biological Sciences, Bowling Green State University, Bowling Green, Ohio
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10
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5-Aminolevulinic acid production from inexpensive glucose by engineering the C4 pathway in Escherichia coli. J Ind Microbiol Biotechnol 2017; 44:1127-1135. [PMID: 28382525 DOI: 10.1007/s10295-017-1940-1] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2016] [Accepted: 03/27/2017] [Indexed: 12/12/2022]
Abstract
5-Aminolevulinic acid (ALA), the first committed intermediate for natural biosynthesis of tetrapyrrole compounds, has recently drawn intensive attention due to its broad potential applications. In this study, we describe the construction of recombinant Escherichia coli strains for ALA production from glucose via the C4 pathway. The hemA gene from Rhodobacter capsulatus was optimally overexpressed using a ribosome binding site engineering strategy, which enhanced ALA production substantially from 20 to 689 mg/L. Following optimization of biosynthesis pathways towards coenzyme A and precursor (glycine and succinyl-CoA), and downregulation of hemB expression, the production of ALA was further increased to 2.81 g/L in batch-fermentation.
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11
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Fratz-Berilla EJ, Breydo L, Gouya L, Puy H, Uversky VN, Ferreira GC. Isoniazid inhibits human erythroid 5-aminolevulinate synthase: Molecular mechanism and tolerance study with four X-linked protoporphyria patients. Biochim Biophys Acta Mol Basis Dis 2017; 1863:428-439. [DOI: 10.1016/j.bbadis.2016.11.011] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2016] [Revised: 10/19/2016] [Accepted: 11/08/2016] [Indexed: 10/20/2022]
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12
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Na I, DeForte S, Stojanovski BM, Ferreira GC, Uversky VN. Molecular dynamics analysis of the structural and dynamic properties of the functionally enhanced hepta-variant of mouse 5-aminolevulinate synthase. J Biomol Struct Dyn 2017; 36:152-165. [PMID: 27928941 DOI: 10.1080/07391102.2016.1269688] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
Heme biosynthesis, a complex, multistage, and tightly controlled process, starts with 5-aminolevulinate (ALA) production, which, in metazoa and certain bacteria, is a reaction catalyzed by 5-aminolevulinate synthase (ALAS), a pyridoxal 5'-phosphate (PLP)-dependent enzyme. Functional aberrations in ALAS are associated with several human diseases. ALAS can adopt open and closed conformations, with segmental rearrangements of a C-terminal, 16-amino acid loop and an α-helix regulating accessibility to the ALAS active site. Of the murine erythroid ALAS (mALAS2) forms previously engineered to assess the role of the flexible C-terminal loop versus mALAS2 function one stood out due to its impressive gain in catalytic power. To elucidate how the simultaneously introduced seven mutations of this activity-enhanced variant affected structural and dynamic properties of mALAS2, we conducted extensive molecular dynamics simulation analysis of the dimeric forms of wild-type mALAS2, hepta-variant and Rhodobacter capsulatus ALAS (aka R. capsulatus HemA). This analysis revealed that the seven simultaneous mutations in the C-terminal loop, which extends over the active site of the enzyme, caused the bacterial and murine proteins to adopt different conformations. Specifically, a new β-strand in the mutated 'loop' led to interaction with two preexisting β-strands and formation of an anti-parallel three-stranded β-sheet, which likely endowed the murine hepta-variant a more 'stable' open conformation than that of wild-type mALAS2, consistent with a kinetic mechanism involving a faster closed-to-open conformation transition and product release for the mutated than wild-type enzyme. Further, the dynamic behavior of the mALAS2 protomers was strikingly different in the two dimeric forms.
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Affiliation(s)
- Insung Na
- a Department of Molecular Medicine , Morsani College of Medicine, University of South Florida , Tampa , FL 33612 , USA
| | - Shelly DeForte
- a Department of Molecular Medicine , Morsani College of Medicine, University of South Florida , Tampa , FL 33612 , USA
| | - Bosko M Stojanovski
- a Department of Molecular Medicine , Morsani College of Medicine, University of South Florida , Tampa , FL 33612 , USA
| | - Gloria C Ferreira
- a Department of Molecular Medicine , Morsani College of Medicine, University of South Florida , Tampa , FL 33612 , USA.,b Department of Chemistry , College of Arts and Sciences, University of South Florida , Tampa , FL 33612 , USA
| | - Vladimir N Uversky
- a Department of Molecular Medicine , Morsani College of Medicine, University of South Florida , Tampa , FL 33612 , USA.,c USF Health Byrd Alzheimer's Research Institute, Morsani College of Medicine , University of South Florida , Tampa , Florida 33612 , USA.,d Laboratory of Structural Dynamics, Stability and Folding of Proteins , Institute of Cytology, Russian Academy of Sciences , St. Petersburg , Russia
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Stojanovski BM, Breydo L, Uversky VN, Ferreira GC. Murine erythroid 5-aminolevulinate synthase: Truncation of a disordered N-terminal extension is not detrimental for catalysis. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2016; 1864:441-52. [DOI: 10.1016/j.bbapap.2016.02.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/19/2015] [Revised: 01/19/2016] [Accepted: 02/03/2016] [Indexed: 11/16/2022]
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Stojanovski BM, Ferreira GC. Asn-150 of Murine Erythroid 5-Aminolevulinate Synthase Modulates the Catalytic Balance between the Rates of the Reversible Reaction. J Biol Chem 2015; 290:30750-61. [PMID: 26511319 DOI: 10.1074/jbc.m115.655399] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2015] [Indexed: 11/06/2022] Open
Abstract
5-Aminolevulinate synthase (ALAS) catalyzes the first step in mammalian heme biosynthesis, the pyridoxal 5'-phosphate (PLP)-dependent and reversible reaction between glycine and succinyl-CoA to generate CoA, CO2, and 5-aminolevulinate (ALA). Apart from coordinating the positioning of succinyl-CoA, Rhodobacter capsulatus ALAS Asn-85 has a proposed role in regulating the opening of an active site channel. Here, we constructed a library of murine erythroid ALAS variants with substitutions at the position occupied by the analogous bacterial asparagine, screened for ALAS function, and characterized the catalytic properties of the N150H and N150F variants. Quinonoid intermediate formation occurred with a significantly reduced rate for either the N150H- or N150F-catalyzed condensation of glycine with succinyl-CoA during a single turnover. The introduced mutations caused modifications in the ALAS active site such that the resulting variants tipped the balance between the forward- and reverse-catalyzed reactions. Although wild-type ALAS catalyzes the conversion of ALA into the quinonoid intermediate at a rate 6.3-fold slower than the formation of the same quinonoid intermediate from glycine and succinyl-CoA, the N150F variant catalyzes the forward reaction at a mere 1.2-fold faster rate than that of the reverse reaction, and the N150H variant reverses the rate values with a 1.7-fold faster rate for the reverse reaction than that for the forward reaction. We conclude that the evolutionary selection of Asn-150 was significant for optimizing the forward enzymatic reaction at the expense of the reverse, thus ensuring that ALA is predominantly available for heme biosynthesis.
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Affiliation(s)
| | - Gloria C Ferreira
- From the Department of Molecular Medicine, Morsani College of Medicine, and the Department of Chemistry, University of South Florida, Tampa, Florida 33612
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Fratz EJ, Clayton J, Hunter GA, Ducamp S, Breydo L, Uversky VN, Deybach JC, Gouya L, Puy H, Ferreira GC. Human Erythroid 5-Aminolevulinate Synthase Mutations Associated with X-Linked Protoporphyria Disrupt the Conformational Equilibrium and Enhance Product Release. Biochemistry 2015; 54:5617-31. [PMID: 26300302 PMCID: PMC4573335 DOI: 10.1021/acs.biochem.5b00407] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Regulation of 5-aminolevulinate synthase (ALAS) is at the origin of balanced heme production in mammals. Mutations in the C-terminal region of human erythroid-specific ALAS (hALAS2) are associated with X-linked protoporphyria (XLPP), a disease characterized by extreme photosensitivity, with elevated blood concentrations of free protoporphyrin IX and zinc protoporphyrin. To investigate the molecular basis for this disease, recombinant hALAS2 and variants of the enzyme harboring the gain-of-function XLPP mutations were constructed, purified, and analyzed kinetically, spectroscopically, and thermodynamically. Enhanced activities of the XLPP variants resulted from increases in the rate at which the product 5-aminolevulinate (ALA) was released from the enzyme. Circular dichroism spectroscopy revealed that the XLPP mutations altered the microenvironment of the pyridoxal 5'-phosphate cofactor, which underwent further and specific alterations upon succinyl-CoA binding. Transient kinetic analyses of the variant-catalyzed reactions and protein fluorescence quenching upon binding of ALA to the XLPP variants demonstrated that the protein conformational transition step associated with product release was predominantly affected. Of relevance is the fact that XLPP could also be modeled in cell culture. We propose that (1) the XLPP mutations destabilize the succinyl-CoA-induced hALAS2 closed conformation and thus accelerate ALA release, (2) the extended C-terminus of wild-type mammalian ALAS2 provides a regulatory role that allows for allosteric modulation of activity, thereby controlling the rate of erythroid heme biosynthesis, and (3) this control is disrupted in XLPP, resulting in porphyrin accumulation.
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Affiliation(s)
- Erica J. Fratz
- Department of Molecular Medicine, Morsani College of Medicine, University of South Florida, Tampa, Florida, 33612, USA
| | - Jerome Clayton
- Department of Molecular Medicine, Morsani College of Medicine, University of South Florida, Tampa, Florida, 33612, USA
| | - Gregory A. Hunter
- Department of Molecular Medicine, Morsani College of Medicine, University of South Florida, Tampa, Florida, 33612, USA
| | - Sarah Ducamp
- Assistance Publique-Hôpitaux de Paris, Centre Français des Porphyries, Hôpital Louis Mourier, 178 rue des Renouillers, 92701 Colombes CEDEX, France
- INSERM U1149, CNRS ERL 8252, Centre de Recherche sur l’inflammation, 16 rue Henri Huchard, 75018, Université Paris Diderot, Site Bichat, 75018 Paris, France; Laboratory of Excellence, GR-Ex, Paris, France
| | - Leonid Breydo
- Department of Molecular Medicine, Morsani College of Medicine, University of South Florida, Tampa, Florida, 33612, USA
| | - Vladimir N. Uversky
- Department of Molecular Medicine, Morsani College of Medicine, University of South Florida, Tampa, Florida, 33612, USA
| | - Jean-Charles Deybach
- Assistance Publique-Hôpitaux de Paris, Centre Français des Porphyries, Hôpital Louis Mourier, 178 rue des Renouillers, 92701 Colombes CEDEX, France
- INSERM U1149, CNRS ERL 8252, Centre de Recherche sur l’inflammation, 16 rue Henri Huchard, 75018, Université Paris Diderot, Site Bichat, 75018 Paris, France; Laboratory of Excellence, GR-Ex, Paris, France
| | - Laurent Gouya
- Assistance Publique-Hôpitaux de Paris, Centre Français des Porphyries, Hôpital Louis Mourier, 178 rue des Renouillers, 92701 Colombes CEDEX, France
- INSERM U1149, CNRS ERL 8252, Centre de Recherche sur l’inflammation, 16 rue Henri Huchard, 75018, Université Paris Diderot, Site Bichat, 75018 Paris, France; Laboratory of Excellence, GR-Ex, Paris, France
| | - Hervé Puy
- Assistance Publique-Hôpitaux de Paris, Centre Français des Porphyries, Hôpital Louis Mourier, 178 rue des Renouillers, 92701 Colombes CEDEX, France
- INSERM U1149, CNRS ERL 8252, Centre de Recherche sur l’inflammation, 16 rue Henri Huchard, 75018, Université Paris Diderot, Site Bichat, 75018 Paris, France; Laboratory of Excellence, GR-Ex, Paris, France
| | - Gloria C. Ferreira
- Department of Molecular Medicine, Morsani College of Medicine, University of South Florida, Tampa, Florida, 33612, USA
- Department of Chemistry, University of South Florida, Tampa, Florida, 33612, USA
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Acevedo-Rocha CG, Reetz MT. Assembly of Designed Oligonucleotides: a useful tool in synthetic biology for creating high-quality combinatorial DNA libraries. Methods Mol Biol 2015; 1179:189-206. [PMID: 25055779 DOI: 10.1007/978-1-4939-1053-3_13] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The method dubbed Assembly of Designed Oligonucleotides (ADO) is a powerful tool in synthetic biology to create combinatorial DNA libraries for gene, protein, metabolic, and genome engineering. In directed evolution of proteins, ADO benefits from using reduced amino acid alphabets for saturation mutagenesis and/or DNA shuffling, but all 20 canonical amino acids can be also used as building blocks. ADO is performed in a two-step reaction. The first involves a primer-free, polymerase cycling assembly or overlap extension PCR step using carefully designed overlapping oligonucleotides. The second step is a PCR amplification using the outer primers, resulting in a high-quality and bias-free double-stranded DNA library that can be assembled with other gene fragments and/or cloned into a suitable plasmid subsequently. The protocol can be performed in a few hours. In theory, neither the length of the DNA library nor the number of DNA changes has any limits. Furthermore, with the costs of synthetic DNA dropping every year, after an initial investment is made in the oligonucleotides, these can be exchanged for alternative ones with different sequences at any point in the process, fully exploiting the potential of creating highly diverse combinatorial libraries. In the example chosen here, we show the construction of a high-quality combinatorial ADO library targeting sixteen different codons simultaneously with nonredundant degenerate codons encoding various reduced alphabets of four amino acids along the heme region of the monooxygenase P450-BM3.
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Affiliation(s)
- Carlos G Acevedo-Rocha
- Organische Synthese, Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, 45470, Mülheim, Germany
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Stojanovski BM, Breydo L, Hunter GA, Uversky VN, Ferreira GC. Catalytically active alkaline molten globular enzyme: Effect of pH and temperature on the structural integrity of 5-aminolevulinate synthase. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2014; 1844:2145-54. [PMID: 25240868 DOI: 10.1016/j.bbapap.2014.09.013] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/10/2014] [Revised: 08/27/2014] [Accepted: 09/10/2014] [Indexed: 11/30/2022]
Abstract
5-Aminolevulinate synthase (ALAS), a pyridoxal-5'phosphate (PLP)-dependent enzyme, catalyzes the first step of heme biosynthesis in mammals. Circular dichroism (CD) and fluorescence spectroscopies were used to examine the effects of pH (1.0-3.0 and 7.5-10.5) and temperature (20 and 37°C) on the structural integrity of ALAS. The secondary structure, as deduced from far-UV CD, is mostly resilient to pH and temperature changes. Partial unfolding was observed at pH2.0, but further decreasing pH resulted in acid-induced refolding of the secondary structure to nearly native levels. The tertiary structure rigidity, monitored by near-UV CD, is lost under acidic and specific alkaline conditions (pH10.5 and pH9.5/37°C), where ALAS populates a molten globule state. As the enzyme becomes less structured with increased alkalinity, the chiral environment of the internal aldimine is also modified, with a shift from a 420nm to 330nm dichroic band. Under acidic conditions, the PLP cofactor dissociates from ALAS. Reaction with 8-anilino-1-naphthalenesulfonic acid corroborates increased exposure of hydrophobic clusters in the alkaline and acidic molten globules, although the reaction is more pronounced with the latter. Furthermore, quenching the intrinsic fluorescence of ALAS with acrylamide at pH1.0 and 9.5 yielded subtly different dynamic quenching constants. The alkaline molten globule state of ALAS is catalytically active (pH9.5/37°C), although the kcat value is significantly decreased. Finally, the binding of 5-aminolevulinate restricts conformational fluctuations in the alkaline molten globule. Overall, our findings prove how the structural plasticity of ALAS contributes to reaching a functional enzyme.
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Affiliation(s)
- Bosko M Stojanovski
- Department of Molecular Medicine, Morsani College of Medicine, University of South Florida, Tampa, FL 33612, USA
| | - Leonid Breydo
- Department of Molecular Medicine, Morsani College of Medicine, University of South Florida, Tampa, FL 33612, USA
| | - Gregory A Hunter
- Department of Molecular Medicine, Morsani College of Medicine, University of South Florida, Tampa, FL 33612, USA
| | - Vladimir N Uversky
- Department of Molecular Medicine, Morsani College of Medicine, University of South Florida, Tampa, FL 33612, USA; USF Health Byrd Alzheimer's Research Institute, University of South Florida, Tampa, FL 33612, USA; Biology Department, Faculty of Science, King Abdulaziz University, Jeddah 21589, Saudi Arabia; Institute for Biological Instrumentation, Russian Academy of Sciences, 142290 Pushchino, Moscow Region, Russia
| | - Gloria C Ferreira
- Department of Molecular Medicine, Morsani College of Medicine, University of South Florida, Tampa, FL 33612, USA; Department of Chemistry, University of South Florida, Tampa, FL 33612, USA.
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Stojanovski BM, Hunter GA, Jahn M, Jahn D, Ferreira GC. Unstable reaction intermediates and hysteresis during the catalytic cycle of 5-aminolevulinate synthase: implications from using pseudo and alternate substrates and a promiscuous enzyme variant. J Biol Chem 2014; 289:22915-22925. [PMID: 24920668 DOI: 10.1074/jbc.m114.574731] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
5-Aminolevulinate (ALA), an essential metabolite in all heme-synthesizing organisms, results from the pyridoxal 5'-phosphate (PLP)-dependent enzymatic condensation of glycine with succinyl-CoA in non-plant eukaryotes and α-proteobacteria. The predicted chemical mechanism of this ALA synthase (ALAS)-catalyzed reaction includes a short-lived glycine quinonoid intermediate and an unstable 2-amino-3-ketoadipate intermediate. Using liquid chromatography coupled with tandem mass spectrometry to analyze the products from the reaction of murine erythroid ALAS (mALAS2) with O-methylglycine and succinyl-CoA, we directly identified the chemical nature of the inherently unstable 2-amino-3-ketoadipate intermediate, which predicates the glycine quinonoid species as its precursor. With stopped-flow absorption spectroscopy, we detected and confirmed the formation of the quinonoid intermediate upon reacting glycine with ALAS. Significantly, in the absence of the succinyl-CoA substrate, the external aldimine predominates over the glycine quinonoid intermediate. When instead of glycine, L-serine was reacted with ALAS, a lag phase was observed in the progress curve for the L-serine external aldimine formation, indicating a hysteretic behavior in ALAS. Hysteresis was not detected in the T148A-catalyzed L-serine external aldimine formation. These results with T148A, a mALAS2 variant, which, in contrast to wild-type mALAS2, is active with L-serine, suggest that active site Thr-148 modulates ALAS strict amino acid substrate specificity. The rate of ALA release is also controlled by a hysteretic kinetic mechanism (observed as a lag in the ALA external aldimine formation progress curve), consistent with conformational changes governing the dissociation of ALA from ALAS.
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Affiliation(s)
- Bosko M Stojanovski
- Department of Molecular Medicine, Morsani College of Medicine, University of South Florida, Tampa, Florida 33612 and
| | - Gregory A Hunter
- Department of Molecular Medicine, Morsani College of Medicine, University of South Florida, Tampa, Florida 33612 and
| | - Martina Jahn
- Institute of Microbiology, Technical University of Braunschweig, Spielmannstrasse 7, D-38106 Braunschweig, Germany
| | - Dieter Jahn
- Institute of Microbiology, Technical University of Braunschweig, Spielmannstrasse 7, D-38106 Braunschweig, Germany
| | - Gloria C Ferreira
- Department of Molecular Medicine, Morsani College of Medicine, University of South Florida, Tampa, Florida 33612 and.
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Fratz EJ, Hunter GA, Ferreira GC. Expression of murine 5-aminolevulinate synthase variants causes protoporphyrin IX accumulation and light-induced mammalian cell death. PLoS One 2014; 9:e93078. [PMID: 24718052 PMCID: PMC3981678 DOI: 10.1371/journal.pone.0093078] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2013] [Accepted: 03/02/2014] [Indexed: 01/11/2023] Open
Abstract
5-Aminolevulinate synthase (ALAS; EC 2.3.1.37) catalyzes the first committed step of heme biosynthesis in animals. The erythroid-specific ALAS isozyme (ALAS2) is negatively regulated by heme at the level of mitochondrial import and, in its mature form, certain mutations of the murine ALAS2 active site loop result in increased production of protoporphyrin IX (PPIX), the precursor for heme. Importantly, generation of PPIX is a crucial component in the widely used photodynamic therapies (PDT) of cancer and other dysplasias. ALAS2 variants that cause high levels of PPIX accumulation provide a new means of targeted, and potentially enhanced, photosensitization. In order to assess the prospective utility of ALAS2 variants in PPIX production for PDT, K562 human erythroleukemia cells and HeLa human cervical carcinoma cells were transfected with expression plasmids for ALAS2 variants with greater enzymatic activity than the wild-type enzyme. The levels of accumulated PPIX in ALAS2-expressing cells were analyzed using flow cytometry with fluorescence detection. Further, cells expressing ALAS2 variants were subjected to white light treatments (21–22 kLux) for 10 minutes after which cell viability was determined. Transfection of HeLa cells with expression plasmids for murine ALAS2 variants, specifically for those with mutated mitochondrial presequences and a mutation in the active site loop, caused significant cellular accumulation of PPIX, particularly in the membrane. Light treatments revealed that ALAS2 expression results in an increase in cell death in comparison to aminolevulinic acid (ALA) treatment producing a similar amount of PPIX. The delivery of stable and highly active ALAS2 variants has the potential to expand and improve upon current PDT regimes.
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Affiliation(s)
- Erica J. Fratz
- Department of Molecular Medicine, Morsani College of Medicine, Tampa, Florida, United States of America
| | - Gregory A. Hunter
- Department of Molecular Medicine, Morsani College of Medicine, Tampa, Florida, United States of America
| | - Gloria C. Ferreira
- Department of Molecular Medicine, Morsani College of Medicine, Tampa, Florida, United States of America
- Department of Chemistry, University of South Florida, Tampa, Florida, United States of America
- * E-mail:
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Bishop DF, Tchaikovskii V, Nazarenko I, Desnick RJ. Molecular expression and characterization of erythroid-specific 5-aminolevulinate synthase gain-of-function mutations causing X-linked protoporphyria. Mol Med 2013; 19:18-25. [PMID: 23348515 DOI: 10.2119/molmed.2013.00003] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2013] [Accepted: 01/15/2013] [Indexed: 11/06/2022] Open
Abstract
X-linked protoporphyria (XLP) (MIM 300752) is a recently recognized erythropoietic porphyria due to gain-of-function mutations in the erythroid-specific aminolevulinate synthase gene (ALAS2). Previously, two exon 11 small deletions, c.1699_1670ΔAT (ΔAT) and c.1706_1709ΔAGTG (ΔAGTG), that prematurely truncated or elongated the ALAS2 polypeptide, were reported to increase enzymatic activity 20- to 40-fold, causing the erythroid accumulation of protoporphyrins, cutaneous photosensitivity and liver disease. The mutant ΔAT and ΔAGTG ALAS2 enzymes, two novel mutations, c.1734ΔG (ΔG) and c.1642C>T (p.Q548X), and an engineered deletion c.1670-1671TC>GA p.F557X were expressed, and their purified enzymes were characterized. Wild-type and ΔAGTG enzymes exhibited similar amounts of 54- and 52-kDa polypeptides on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), whereas the ΔAT and p.F557X had only 52-kDa polypeptides. Compared to the purified wild-type enzyme, ΔAT, ΔAGTG and Q548X enzymes had increased specific activities that were only 1.8-, 3.1- and 1.6-fold, respectively. Interestingly, binding studies demonstrated that the increased activity Q548X enzyme did not bind to succinyl-CoA synthetase. The elongated ΔG enzyme had wild-type specific activity, kinetics and thermostability; twice the wild-type purification yield (56 versus 25%); and was primarily a 54-kDa form, suggesting greater stability in vivo. On the basis of studies of mutant enzymes, the maximal gain-of function region spanned 57 amino acids between 533 and 580. Thus, these ALAS2 gain-of-function mutations increased the specific activity (ΔAT, ΔAGTG and p.Q548X) or stability (ΔG) of the enzyme, thereby leading to the increased erythroid protoporphyrin accumulation causing XLP.
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Affiliation(s)
- David F Bishop
- Department of Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, Mount Sinai Medical Center, New York, New York 10029, USA
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Ducamp S, Schneider-Yin X, de Rooij F, Clayton J, Fratz EJ, Rudd A, Ostapowicz G, Varigos G, Lefebvre T, Deybach JC, Gouya L, Wilson P, Ferreira GC, Minder EI, Puy H. Molecular and functional analysis of the C-terminal region of human erythroid-specific 5-aminolevulinic synthase associated with X-linked dominant protoporphyria (XLDPP). Hum Mol Genet 2012; 22:1280-8. [PMID: 23263862 DOI: 10.1093/hmg/dds531] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Frameshift mutations in the last coding exon of the 5-aminolevulinate synthase (ALAS) 2 gene were described to activate the enzyme causing increased levels of zinc- and metal-free protoporphyrin in patients with X-linked dominant protoporphyria (XLDPP). Only two such so-called gain-of-function mutations have been reported since the description of XLDPP in 2008. In this study of four newly identified XLDPP families, we identified two novel ALAS2 gene mutations, a nonsense p.Q548X and a frameshift c.1651-1677del26bp, along with a known mutation (delAGTG) found in two unrelated families. Of relevance, a de novo somatic and germinal mosaicism was present in a delAGTG family. Such a phenomenon may explain the high proportion of this mutation in XLDPP worldwide. Enhancements of over 3- and 14-fold in the catalytic rate and specificity constant of purified recombinant XLDPP variants in relation to those of wild-type ALAS2 confirmed the gain of function ascribed to these enzymes. The fact that both p.Q548X and c.1651-1677del26bp are located in close proximity and upstream from the two previously described mutations led us to propose the presence of a large gain-of-function domain within the C-terminus of ALAS2. To test this hypothesis, we generated four additional nonsense mutants (p.A539X, p.G544X, p.G576X and p.V583X) surrounding the human XLDPP mutations and defined an ALAS2 gain-of-function domain with a minimal size of 33 amino acids. The identification of this gain-of-function domain provides important information on the enzymatic activity of ALAS2, which was proposed to be constitutively inhibited, either directly or indirectly, through its own C-terminus.
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Affiliation(s)
- Sarah Ducamp
- AP-HP, Centre Franc¸ais des Porphyries, Hoˆ pital Louis Mourier, 178 rue des Renouillers, 92701 Colombes Cedex,France
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Bishop DF, Tchaikovskii V, Hoffbrand AV, Fraser ME, Margolis S. X-linked sideroblastic anemia due to carboxyl-terminal ALAS2 mutations that cause loss of binding to the β-subunit of succinyl-CoA synthetase (SUCLA2). J Biol Chem 2012; 287:28943-55. [PMID: 22740690 PMCID: PMC3436539 DOI: 10.1074/jbc.m111.306423] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2012] [Indexed: 11/06/2022] Open
Abstract
Mutations in the erythroid-specific aminolevulinic acid synthase gene (ALAS2) cause X-linked sideroblastic anemia (XLSA) by reducing mitochondrial enzymatic activity. Surprisingly, a patient with the classic XLSA phenotype had a novel exon 11 mutation encoding a recombinant enzyme (p.Met567Val) with normal activity, kinetics, and stability. Similarly, both an expressed adjacent XLSA mutation, p.Ser568Gly, and a mutation (p.Phe557Ter) lacking the 31 carboxyl-terminal residues also had normal or enhanced activity, kinetics, and stability. Because ALAS2 binds to the β subunit of succinyl-CoA synthetase (SUCLA2), the mutant proteins were tested for their ability to bind to this protein. Wild type ALAS2 bound strongly to a SUCLA2 affinity column, but the adjacent XLSA mutant enzymes and the truncated mutant did not bind. In contrast, vitamin B6-responsive XLSA mutations p.Arg452Cys and p.Arg452His, with normal in vitro enzyme activity and stability, did not interfere with binding to SUCLA2 but instead had loss of positive cooperativity for succinyl-CoA binding, an increased K(m) for succinyl-CoA, and reduced vitamin B6 affinity. Consistent with the association of SUCLA2 binding with in vivo ALAS2 activity, the p.Met567GlufsX2 mutant protein that causes X-linked protoporphyria bound strongly to SUCLA2, highlighting the probable role of an ALAS2-succinyl-CoA synthetase complex in the regulation of erythroid heme biosynthesis.
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Affiliation(s)
- David F. Bishop
- From the Department of Genetics and Genomic Sciences, Mount Sinai School of Medicine, New York, New York 10029
| | - Vassili Tchaikovskii
- From the Department of Genetics and Genomic Sciences, Mount Sinai School of Medicine, New York, New York 10029
| | - A. Victor Hoffbrand
- the Department of Haematology, Royal Free Hospital, London NW3 2QG, United Kingdom, and
| | - Marie E. Fraser
- the Department of Biological Sciences, University of Calgary, Calgary, Alberta T2N 1N4, Canada
| | - Steven Margolis
- From the Department of Genetics and Genomic Sciences, Mount Sinai School of Medicine, New York, New York 10029
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Kadirvel S, Furuyama K, Harigae H, Kaneko K, Tamai Y, Ishida Y, Shibahara S. The carboxyl-terminal region of erythroid-specific 5-aminolevulinate synthase acts as an intrinsic modifier for its catalytic activity and protein stability. Exp Hematol 2012; 40:477-86.e1. [PMID: 22269113 DOI: 10.1016/j.exphem.2012.01.013] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2010] [Revised: 01/10/2012] [Accepted: 01/18/2012] [Indexed: 01/19/2023]
Abstract
Erythroid-specific 5-aminolevulinate synthase (ALAS2) is essential for hemoglobin production, and a loss-of-function mutation of ALAS2 gene causes X-linked sideroblastic anemia. Human ALAS2 protein consists of 587 amino acids and its carboxyl(C)-terminal region of 33 amino acids is conserved in higher eukaryotes, but is not present in prokaryotic ALAS. We explored the role of this C-terminal region in the pathogenesis of X-linked sideroblastic anemia. In vitro enzymatic activity was measured using bacterially expressed recombinant proteins. In vivo catalytic activity was evaluated by comparing the accumulation of porphyrins in eukaryotic cells stably expressing each mutant ALAS2 tagged with FLAG, and the half-life of each FLAG-tagged ALAS2 protein was determined by Western blot analysis. Two novel mutations (Val562Ala and Met567Ile) were identified in patients with X-linked sideroblastic anemia. Val562Ala showed the higher catalytic activity in vitro, but a shorter half-life in vivo compared to those of wild-type ALAS2 (WT). In contrast, the in vitro activity of Met567Ile mutant was about 25% of WT, while its half-life was longer than that of WT. However, in vivo catalytic activity of each mutant was lower than that of WT. In addition, the deletion of 33 amino acids at C-terminal end resulted in higher catalytic activity both in vitro and in vivo with the longer half-life compared to WT. In conclusion, the C-terminal region of ALAS2 protein may function as an intrinsic modifier that suppresses catalytic activity and increases the degradation of its protein, each function of which is enhanced by the Met567Ile mutation and the Val562Ala mutation, respectively.
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Affiliation(s)
- Senkottuvelan Kadirvel
- Department of Molecular Biology and Applied Physiology, Tohoku University School of Medicine, Sendai, Japan
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Abstract
Mutations in the uroporphyrinogen III synthase (UROS) gene cause congenital erythropoietic porphyria (CEP), an autosomal-recessive inborn error of erythroid heme biosynthesis. Clinical features of CEP include dermatologic and hematologic abnormalities of variable severity. The discovery of a new type of erythroid porphyria, X-linked dominant protoporphyria (XLDPP), which results from increased activity of 5-aminolevulinate synthase 2 (ALAS2), the rate-controlling enzyme of erythroid heme synthesis, led us to hypothesize that the CEP phenotype may be modulated by sequence variations in the ALAS2 gene. We genotyped ALAS2 in 4 unrelated CEP patients exhibiting the same C73R/P248Q UROS genotype. The most severe of the CEP patients, a young girl, proved to be heterozygous for a novel ALAS2 mutation: c.1757 A > T in exon 11. This mutation is predicted to affect the highly conserved and penultimate C-terminal amino acid of ALAS2 (Y586). The rate of 5-aminolevulinate release from Y586F was significantly increased over that of wild-type ALAS2. The contribution of the ALAS2 gain-of-function mutation to the CEP phenotype underscores the importance of modifier genes underlying CEP. We propose that ALAS2 gene mutations should be considered not only as causative of X-linked sideroblastic anemia (XLSA) and XLDPP but may also modulate gene function in other erythropoietic disorders.
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Turbeville TD, Zhang J, Adams WC, Hunter GA, Ferreira GC. Functional asymmetry for the active sites of linked 5-aminolevulinate synthase and 8-amino-7-oxononanoate synthase. Arch Biochem Biophys 2011; 511:107-17. [PMID: 21600186 DOI: 10.1016/j.abb.2011.05.002] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2011] [Revised: 05/03/2011] [Accepted: 05/04/2011] [Indexed: 11/25/2022]
Abstract
5-Aminolevulinate synthase (ALAS) and 8-amino-7-oxononanoate synthase (AONS) are homodimeric members of the α-oxoamine synthase family of pyridoxal 5'-phosphate (PLP)-dependent enzymes. Previously, linking two ALAS subunits into a single polypeptide chain dimer yielded an enzyme (ALAS/ALAS) with a significantly greater turnover number than that of wild-type ALAS. To examine the contribution of each active site to the enzymatic activity of ALAS/ALAS, the catalytic lysine, which also covalently binds the PLP cofactor, was substituted with alanine in one of the active sites. Albeit the chemical rate for the pre-steady-state burst of ALA formation was identical in both active sites of ALAS/ALAS, the k(cat) values of the variants differed significantly (4.4±0.2 vs. 21.6±0.7 min(-1)) depending on which of the two active sites harbored the mutation. We propose that the functional asymmetry for the active sites of ALAS/ALAS stems from linking the enzyme subunits and the introduced intermolecular strain alters the protein conformational flexibility and rates of product release. Moreover, active site functional asymmetry extends to chimeric ALAS/AONS proteins, which while having a different oligomeric state, exhibit different rates of product release from the two ALAS and two AONS active sites due to the created intermolecular strain.
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Affiliation(s)
- Tracy D Turbeville
- Department of Molecular Medicine, College of Medicine, University of South Florida, Tampa, FL 33612, USA
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26
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Hunter GA, Ferreira GC. Molecular enzymology of 5-aminolevulinate synthase, the gatekeeper of heme biosynthesis. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2011; 1814:1467-73. [PMID: 21215825 DOI: 10.1016/j.bbapap.2010.12.015] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/11/2010] [Revised: 12/15/2010] [Accepted: 12/30/2010] [Indexed: 02/06/2023]
Abstract
Pyridoxal-5'-phosphate (PLP) is an obligatory cofactor for the homodimeric mitochondrial enzyme 5-aminolevulinate synthase (ALAS), which controls metabolic flux into the porphyrin biosynthetic pathway in animals, fungi, and the α-subclass of proteobacteria. Recent work has provided an explanation for how this enzyme can utilize PLP to catalyze the mechanistically unusual cleavage of not one but two substrate amino acid α-carbon bonds, without violating the theory of stereoelectronic control of PLP reaction-type specificity. Ironically, the complex chemistry is kinetically insignificant, and it is the movement of an active site loop that defines k(cat) and ultimately, the rate of porphyrin biosynthesis. The kinetic behavior of the enzyme is consistent with an equilibrium ordered induced-fit mechanism wherein glycine must bind first and a portion of the intrinsic binding energy with succinyl-Coenzyme A is then utilized to perturb the enzyme conformational equilibrium towards a closed state wherein catalysis occurs. Return to the open conformation, coincident with ALA dissociation, is the slowest step of the reaction cycle. A diverse variety of loop mutations have been associated with hyperactivity, suggesting the enzyme has evolved to be purposefully slow, perhaps as a means to allow for rapid up-regulation of activity in response to an as yet undiscovered allosteric type effector. Recently it was discovered that human erythroid ALAS mutations can be associated with two very different diseases. Mutations that down-regulate activity can lead to X-linked sideroblastic anemia, which is characterized by abnormally high iron levels in mitochondria, while mutations that up-regulate activity are associated with X-linked dominant protoporphyria, which in contrast is phenotypically identified by abnormally high porphyrin levels. This article is part of a Special Issue entitled: Pyridoxal Phosphate Enzymology.
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Affiliation(s)
- Gregory A Hunter
- Department of Molecular Medicine, College of Medicine, University of South Florida, Tampa, Florida 33612-4799, USA
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