1
|
Zhao JR, Zuo SQ, Xiao F, Guo FZ, Chen LY, Bi K, Cheng DY, Xu ZN. Advances in biotin biosynthesis and biotechnological production in microorganisms. World J Microbiol Biotechnol 2024; 40:163. [PMID: 38613659 DOI: 10.1007/s11274-024-03971-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2024] [Accepted: 03/28/2024] [Indexed: 04/15/2024]
Abstract
Biotin, also known as vitamin H or B7, acts as a crucial cofactor in the central metabolism processes of fatty acids, amino acids, and carbohydrates. Biotin has important applications in food additives, biomedicine, and other fields. While the ability to synthesize biotin de novo is confined to microorganisms and plants, humans and animals require substantial daily intake, primarily through dietary sources and intestinal microflora. Currently, chemical synthesis stands as the primary method for commercial biotin production, although microbial biotin production offers an environmentally sustainable alternative with promising prospects. This review presents a comprehensive overview of the pathways involved in de novo biotin synthesis in various species of microbes and insights into its regulatory and transport systems. Furthermore, diverse strategies are discussed to improve the biotin production here, including mutation breeding, rational metabolic engineering design, artificial genetic modification, and process optimization. The review also presents the potential strategies for addressing current challenges for industrial-scale bioproduction of biotin in the future. This review is very helpful for exploring efficient and sustainable strategies for large-scale biotin production.
Collapse
Affiliation(s)
- Jia-Run Zhao
- Key Laboratory of Biomass Chemical Engineering of Ministry of Education, College of Chemical and Biological Engineering, Zhejiang University, Hangzhou, 310027, China
- Institute of Biological Engineering, College of Chemical and Biological Engineering, Zhejiang University, Hangzhou, 310027, China
| | - Si-Qi Zuo
- Key Laboratory of Biomass Chemical Engineering of Ministry of Education, College of Chemical and Biological Engineering, Zhejiang University, Hangzhou, 310027, China
- Institute of Biological Engineering, College of Chemical and Biological Engineering, Zhejiang University, Hangzhou, 310027, China
| | - Feng Xiao
- Key Laboratory of Biomass Chemical Engineering of Ministry of Education, College of Chemical and Biological Engineering, Zhejiang University, Hangzhou, 310027, China
- Institute of Biological Engineering, College of Chemical and Biological Engineering, Zhejiang University, Hangzhou, 310027, China
- ZJU-Hangzhou Global Scientific and Technological Innovation Center, Zhejiang University, Hangzhou, 310000, China
| | - Feng-Zhu Guo
- Zhejiang Sliver-Elephant Bio-engineering Co., Ltd., Tiantai, 317200, China
| | - Lu-Yi Chen
- Zhejiang Sliver-Elephant Bio-engineering Co., Ltd., Tiantai, 317200, China
| | - Ke Bi
- Key Laboratory of Biomass Chemical Engineering of Ministry of Education, College of Chemical and Biological Engineering, Zhejiang University, Hangzhou, 310027, China
- Institute of Biological Engineering, College of Chemical and Biological Engineering, Zhejiang University, Hangzhou, 310027, China
| | - Dong-Yuan Cheng
- Key Laboratory of Biomass Chemical Engineering of Ministry of Education, College of Chemical and Biological Engineering, Zhejiang University, Hangzhou, 310027, China
- Institute of Biological Engineering, College of Chemical and Biological Engineering, Zhejiang University, Hangzhou, 310027, China
| | - Zhi-Nan Xu
- Key Laboratory of Biomass Chemical Engineering of Ministry of Education, College of Chemical and Biological Engineering, Zhejiang University, Hangzhou, 310027, China.
- Institute of Biological Engineering, College of Chemical and Biological Engineering, Zhejiang University, Hangzhou, 310027, China.
| |
Collapse
|
2
|
Ma B, Britt RD, Tao L. Radical SAM Enzyme PylB Generates a Lysyl Radical Intermediate in the Biosynthesis of Pyrrolysine by Using SAM as a Cofactor. J Am Chem Soc 2024; 146:6544-6556. [PMID: 38426740 DOI: 10.1021/jacs.3c11266] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/02/2024]
Abstract
Pyrrolysine, the 22nd amino acid encoded by the natural genetic code, is essential for methanogenic archaea to catabolize methylamines into methane. The structure of pyrrolysine consists of a methylated pyrroline carboxylate that is linked to the ε-amino group of the l-lysine via an amide bond. The biosynthesis of pyrrolysine requires three enzymes: PylB, PylC, and PylD. PylB is a radical S-adenosyl-l-methionine (SAM) enzyme and catalyzes the first biosynthetic step, the isomerization of l-lysine into methylornithine. PylC catalyzes an ATP-dependent ligation of methylornithine and a second l-lysine to form l-lysine-Nε-methylornithine. The last biosynthetic step is catalyzed by PylD via oxidation of the PylC product to form pyrrolysine. While enzymatic reactions of PylC and PylD have been well characterized by X-ray crystallography and in vitro studies, mechanistic understanding of PylB is still relatively limited. Here, we report the first in vitro activity of PylB to form methylornithine via the isomerization of l-lysine. We also identify a lysyl C4 radical intermediate that is trapped, with its electronic structure and geometric structure well characterized by EPR and ENDOR spectroscopy. In addition, we demonstrate that SAM functions as a catalytic cofactor in PylB catalysis rather than canonically as a cosubstrate. This work provides detailed mechanistic evidence for elucidating the carbon backbone rearrangement reaction catalyzed by PylB during the biosynthesis of pyrrolysine.
Collapse
Affiliation(s)
- Baixu Ma
- Department of Chemistry, Southern University of Science and Technology, Shenzhen 518055, China
| | - R David Britt
- Department of Chemistry, University of California, Davis, Davis, California 95616, United States
| | - Lizhi Tao
- Department of Chemistry, Southern University of Science and Technology, Shenzhen 518055, China
| |
Collapse
|
3
|
Eastman KAS, Jochimsen AS, Bandarian V. Intermolecular electron transfer in radical SAM enzymes as a new paradigm for reductive activation. J Biol Chem 2023; 299:105058. [PMID: 37460016 PMCID: PMC10470005 DOI: 10.1016/j.jbc.2023.105058] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2023] [Revised: 07/10/2023] [Accepted: 07/13/2023] [Indexed: 08/26/2023] Open
Abstract
Radical S-adenosyl-L-methionine (rSAM) enzymes bind one or more Fe-S clusters and catalyze transformations that produce complex and structurally diverse natural products. One of the clusters, a 4Fe-4S cluster, binds and reductively cleaves SAM to generate the 5'-deoxyadenosyl radical, which initiates the catalytic cycle by H-atom transfer from the substrate. The role(s) of the additional auxiliary Fe-S clusters (ACs) remains largely enigmatic. The rSAM enzyme PapB catalyzes the formation of thioether cross-links between the β-carbon of an Asp and a Cys thiolate found in the PapA peptide. One of the two ACs in the protein binds to the substrate thiol where, upon formation of a thioether bond, one reducing equivalent is returned to the protein. However, for the next catalytic cycle to occur, the protein must undergo an electronic state isomerization, returning the electron to the SAM-binding cluster. Using a series of iron-sulfur cluster deletion mutants, our data support a model whereby the isomerization is an obligatorily intermolecular electron transfer event that can be mediated by redox active proteins or small molecules, likely via the second AC in PapB. Surprisingly, a mixture of FMN and NADPH is sufficient to support both the reductive and the isomerization steps. These findings lead to a new paradigm involving intermolecular electron transfer steps in the activation of rSAM enzymes that require multiple iron-sulfur clusters for turnover. The implications of these results for the biological activation of rSAM enzymes are discussed.
Collapse
Affiliation(s)
| | | | - Vahe Bandarian
- University of Utah, Department of Chemistry, Salt Lake City, Utah, USA.
| |
Collapse
|
4
|
Rush K, Eastman KAS, Kincannon WM, Blackburn NJ, Bandarian V. Peptide Selenocysteine Substitutions Reveal Direct Substrate-Enzyme Interactions at Auxiliary Clusters in Radical S-Adenosyl-l-methionine Maturases. J Am Chem Soc 2023; 145:10167-10177. [PMID: 37104670 PMCID: PMC10177961 DOI: 10.1021/jacs.3c00831] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2023] [Indexed: 04/29/2023]
Abstract
Radical S-adenosyl-l-methionine (SAM) enzymes leverage the properties of one or more iron- and sulfide-containing metallocenters to catalyze complex and radical-mediated transformations. By far the most populous superfamily of radical SAM enzymes are those that, in addition to a 4Fe-4S cluster that binds and activates the SAM cofactor, also bind one or more additional auxiliary clusters (ACs) of largely unknown catalytic significance. In this report we examine the role of ACs in two RS enzymes, PapB and Tte1186, that catalyze formation of thioether cross-links in ribosomally synthesized and post-translationally modified peptides (RiPPs). Both enzymes catalyze a sulfur-to-carbon cross-link in a reaction that entails H atom transfer from an unactivated C-H to initiate catalysis, followed by formation of a C-S bond to yield the thioether. We show that both enzymes tolerate substitution of SeCys instead of Cys at the cross-linking site, allowing the systems to be subjected to Se K-edge X-ray spectroscopy. The EXAFS data show a direct interaction with the Fe of one of the ACs in the Michaelis complex, which is replaced with a Se-C interaction under reducing conditions that lead to the product complex. Site-directed deletion of the clusters in Tte1186 provide evidence for the identity of the AC. The implications of these observations in the context of the mechanism of these thioether cross-linking enzymes are discussed.
Collapse
Affiliation(s)
- Katherine
W. Rush
- Department
of Chemical Physiology and Biochemistry, Oregon Health & Science University, Portland, Oregon 97239, United States
- Department
of Chemistry, Reed College, 3203 SE Woodstock Blvd., Portland, Oregon 97202, United States
| | - Karsten A. S. Eastman
- Department
of Chemistry, University of Utah, 315 South 1400 East, Salt Lake City, Utah 84112, United States
| | - William M. Kincannon
- Department
of Chemistry, University of Utah, 315 South 1400 East, Salt Lake City, Utah 84112, United States
| | - Ninian J. Blackburn
- Department
of Chemical Physiology and Biochemistry, Oregon Health & Science University, Portland, Oregon 97239, United States
| | - Vahe Bandarian
- Department
of Chemistry, University of Utah, 315 South 1400 East, Salt Lake City, Utah 84112, United States
| |
Collapse
|
5
|
Young AP, Bandarian V. Insertion of 4-Demethylwyosine in tRNA Phe Catalyzed by the Radical S-Adenosyl-l-methionine Enzyme TYW1 Entails Oxidative Cleavage of Pyruvate to Form CO 2. Biochemistry 2022; 61:2643-2647. [PMID: 36326713 PMCID: PMC10874244 DOI: 10.1021/acs.biochem.2c00519] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The radical S-adenosyl-l-methionine (SAM) enzyme TYW1 catalyzes the condensation of C-2 and C-3 atoms of pyruvate with N-methylguanosine containing tRNAPhe to form 4-demethylwyosine (imG-14) modified tRNAPhe. The fate of C-1 is not known, and either formate or carbon dioxide (CO2) has been proposed. In this study, a coupled assay that transforms either CO2 or formate to oxaloacetate (OAA) was used to determine the fate of C-1. In the presence of [1-13C1]-pyruvate, 13C-enriched OAA was observed in a process that is concomitant with the formation of imG-14, under conditions that preferentially transform CO2 and not formate to OAA. These findings are discussed in the context of the cofactor content of TYW1 and a new role for the auxiliary cluster in catalyzing the oxidative cleavage of C-1-C-2 bond of pyruvate in the catalytic cycle of TYW1.
Collapse
Affiliation(s)
| | - Vahe Bandarian
- Department of Chemistry, University of Utah, Salt Lake City, Utah 84112, United States
| |
Collapse
|
6
|
Chatterjee S, Hausinger RP. Sulfur incorporation into biomolecules: recent advances. Crit Rev Biochem Mol Biol 2022; 57:461-476. [PMID: 36403141 PMCID: PMC10192010 DOI: 10.1080/10409238.2022.2141678] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2022] [Revised: 10/05/2022] [Accepted: 10/26/2022] [Indexed: 11/21/2022]
Abstract
Sulfur is an essential element for a variety of cellular constituents in all living organisms and adds considerable functionality to a wide range of biomolecules. The pathways for incorporating sulfur into central metabolites of the cell such as cysteine, methionine, cystathionine, and homocysteine have long been established. Furthermore, the importance of persulfide intermediates during the biosynthesis of thionucleotide-containing tRNAs, iron-sulfur clusters, thiamin diphosphate, and the molybdenum cofactor are well known. This review briefly surveys these topics while emphasizing more recent aspects of sulfur metabolism that involve unconventional biosynthetic pathways. Sacrificial sulfur transfers from protein cysteinyl side chains to precursors of thiamin and the nickel-pincer nucleotide (NPN) cofactor are described. Newer aspects of synthesis for lipoic acid, biotin, and other compounds are summarized, focusing on the requisite iron-sulfur cluster destruction. Sulfur transfers by using a noncore sulfide ligand bound to a [4Fe-4S] cluster are highlighted for generating certain thioamides and for alternative biosynthetic pathways of thionucleotides and the NPN cofactor. Thioamide formation by activating an amide oxygen atom via phosphorylation also is illustrated. The discussion of these topics stresses the chemical reaction mechanisms of the transformations and generally avoids comments on the gene/protein nomenclature or the sources of the enzymes. This work sets the stage for future efforts to decipher the diverse mechanisms of sulfur incorporation into biological molecules.
Collapse
Affiliation(s)
- Shramana Chatterjee
- Department of Microbiology & Molecular Genetics, Michigan State University, East Lansing, MI, USA
| | - Robert P. Hausinger
- Department of Microbiology & Molecular Genetics, Michigan State University, East Lansing, MI, USA
- Department of Biochemistry & Molecular Biology, Michigan State University, East Lansing, MI, USA
| |
Collapse
|
7
|
Rao G, Chen N, Marchiori DA, Wang LP, Britt RD. Accumulation and Pulse Electron Paramagnetic Resonance Spectroscopic Investigation of the 4-Oxidobenzyl Radical Generated in the Radical S-Adenosyl-l-methionine Enzyme HydG. Biochemistry 2022; 61:107-116. [PMID: 34989236 DOI: 10.1021/acs.biochem.1c00619] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The radical S-adenosyl-l-methionine (SAM) enzyme HydG cleaves tyrosine to generate CO and CN- ligands of the [FeFe] hydrogenase H-cluster, accompanied by the formation of a 4-oxidobenzyl radical (4-OB•), which is the precursor to the HydG p-cresol byproduct. Native HydG only generates a small amount of 4-OB•, limiting detailed electron paramagnetic resonance (EPR) spectral characterization beyond our initial EPR lineshape study employing various tyrosine isotopologues. Here, we show that the concentration of trapped 4-OB• is significantly increased in reactions using HydG variants, in which the "dangler Fe" to which CO and CN- bind is missing or substituted by a redox-inert Zn2+ ion. This allows for the detailed characterization of 4-OB• using high-field EPR and electron nuclear double resonance spectroscopy to extract its g-values and 1H/13C hyperfine couplings. These results are compared to density functional theory-predicted values of several 4-OB• models with different sizes and protonation states, with a best fit to the deprotonated radical anion configuration of 4-OB•. Overall, our results depict a clearer electronic structure of the transient 4-OB• radical and provide new insights into the radical SAM chemistry of HydG.
Collapse
Affiliation(s)
- Guodong Rao
- Department of Chemistry, University of California Davis, Davis, California 95616, United States
| | - Nanhao Chen
- Department of Chemistry, University of California Davis, Davis, California 95616, United States
| | - David A Marchiori
- Department of Chemistry, University of California Davis, Davis, California 95616, United States
| | - Lee-Ping Wang
- Department of Chemistry, University of California Davis, Davis, California 95616, United States
| | - R David Britt
- Department of Chemistry, University of California Davis, Davis, California 95616, United States
| |
Collapse
|
8
|
Maiti BK, Maia LB, Moura JJG. Sulfide and transition metals - A partnership for life. J Inorg Biochem 2021; 227:111687. [PMID: 34953313 DOI: 10.1016/j.jinorgbio.2021.111687] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2021] [Revised: 11/24/2021] [Accepted: 11/28/2021] [Indexed: 12/13/2022]
Abstract
Sulfide and transition metals often came together in Biology. The variety of possible structural combinations enabled living organisms to evolve an array of highly versatile metal-sulfide centers to fulfill different physiological roles. The ubiquitous iron‑sulfur centers, with their structural, redox, and functional diversity, are certainly the best-known partners, but other metal-sulfide centers, involving copper, nickel, molybdenum or tungsten, are equally crucial for Life. This review provides a concise overview of the exclusive sulfide properties as a metal ligand, with emphasis on the structural aspects and biosynthesis. Sulfide as catalyst and as a substrate is discussed. Different enzymes are considered, including xanthine oxidase, formate dehydrogenases, nitrogenases and carbon monoxide dehydrogenases. The sulfide effect on the activity and function of iron‑sulfur, heme and zinc proteins is also addressed.
Collapse
Affiliation(s)
- Biplab K Maiti
- National Institute of Technology Sikkim, Department of Chemistry, Ravangla Campus, Barfung Block, Ravangla Sub Division, South Sikkim 737139, India.
| | - Luisa B Maia
- LAQV, REQUIMTE, Department of Chemistry, NOVA School of Science and Technology (FCT NOVA), Universidade NOVA de Lisboa, Campus de Caparica, Portugal.
| | - José J G Moura
- LAQV, REQUIMTE, Department of Chemistry, NOVA School of Science and Technology (FCT NOVA), Universidade NOVA de Lisboa, Campus de Caparica, Portugal.
| |
Collapse
|
9
|
Zhu W, Walker LM, Tao L, Iavarone AT, Wei X, Britt RD, Elliott SJ, Klinman JP. Structural Properties and Catalytic Implications of the SPASM Domain Iron-Sulfur Clusters in Methylorubrum extorquens PqqE. J Am Chem Soc 2020; 142:12620-12634. [PMID: 32643933 DOI: 10.1021/jacs.0c02044] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Understanding the relationship between the metallocofactor and its protein environment is the key to uncovering the mechanism of metalloenzymes. PqqE, a radical S-adenosylmethionine enzyme in pyrroloquinoline quinone (PQQ) biosynthesis, contains three iron-sulfur cluster binding sites. Two auxiliary iron-sulfur cluster binding sites, designated as AuxI and AuxII, use distinctive ligands compared to other proteins in the family while their functions remain unclear. Here, we investigate the electronic properties of these iron-sulfur clusters and compare the catalytic efficiency of wild-type (WT) Methylorubrum extorquens AM1 PqqE to a range of mutated constructs. Using native mass spectrometry, protein film electrochemistry, and electron paramagnetic resonance spectroscopy, we confirm the previously proposed incorporation of a mixture of [2Fe-2S] and [4Fe-4S] clusters at the AuxI site and are able to assign redox potentials to each of the three iron-sulfur clusters. Significantly, a conservative mutation at AuxI, C268H, shown to selectively incorporate a [4Fe-4S] cluster, catalyzes an enhancement of uncoupled S-adenosylmethionine cleavage relative to WT, together with the elimination of detectable peptide cross-linked product. While a [4Fe-4S] cluster can be tolerated at the AuxI site, the aggregate findings suggest a functional [2Fe-2S] configuration within the AuxI site. PqqE variants with nondestructive ligand replacements at AuxII also show that the reduction potential at this site can be manipulated by changing the electronegativity of the unique aspartate ligand. A number of novel mechanistic features are proposed based on the kinetic and spectroscopic data. Additionally, bioinformatic analyses suggest that the unique ligand environment of PqqE may be relevant to its role in PQQ biosynthesis within an oxygen-dependent biosynthetic pathway.
Collapse
Affiliation(s)
- Wen Zhu
- California Institute for Quantitative Biosciences, University of California-Berkeley, Berkeley, California 94720, United States
| | - Lindsey M Walker
- Department of Chemistry, Boston University, Boston, Massachusetts 02215, United States
| | - Lizhi Tao
- Department of Chemistry, University of California-Davis, Davis, California 95616, United States
| | - Anthony T Iavarone
- California Institute for Quantitative Biosciences, University of California-Berkeley, Berkeley, California 94720, United States
| | - Xuetong Wei
- Department of Molecular and Cell Biology, University of California-Berkeley, Berkeley, California 94720, United States
| | - R David Britt
- Department of Chemistry, University of California-Davis, Davis, California 95616, United States
| | - Sean J Elliott
- Department of Chemistry, Boston University, Boston, Massachusetts 02215, United States
| | - Judith P Klinman
- California Institute for Quantitative Biosciences, University of California-Berkeley, Berkeley, California 94720, United States.,Department of Molecular and Cell Biology, University of California-Berkeley, Berkeley, California 94720, United States.,Department of Chemistry, University of California-Berkeley, Berkeley, California 94720, United States
| |
Collapse
|
10
|
Zhang B, Arcinas AJ, Radle MI, Silakov A, Booker SJ, Krebs C. First Step in Catalysis of the Radical S-Adenosylmethionine Methylthiotransferase MiaB Yields an Intermediate with a [3Fe-4S] 0-Like Auxiliary Cluster. J Am Chem Soc 2020; 142:1911-1924. [PMID: 31899624 PMCID: PMC7008301 DOI: 10.1021/jacs.9b11093] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The enzyme MiaB catalyzes the attachment of a methylthio (-SCH3) group at the C2 position of N6-(isopentenyl)adenosine (i6A) in the final step of the biosynthesis of the hypermodified tRNA nucleotide 2-methythio-N6-(isopentenyl)adenosine (ms2i6A). MiaB belongs to the expanding subgroup of enzymes of the radical S-adenosylmethionine (SAM) superfamily that harbor one or more auxiliary [4Fe-4S] clusters in addition to the [4Fe-4S] cluster that all family members require for the reductive cleavage of SAM to afford the common 5'-deoxyadenosyl 5'-radical (5'-dA•) intermediate. While the role of the radical SAM cluster in generating the 5'-dA• is well understood, the detailed role of the auxiliary cluster, which is essential for MiaB catalysis, remains unclear. It has been proposed that the auxiliary cluster may serve as a coordination site for exogenously derived sulfur destined for attachment to the substrate or that the cluster itself provides the sulfur atom and is sacrificed during turnover. In this work, we report spectroscopic and biochemical evidence that the auxiliary [4Fe-4S]2+ cluster in Bacteroides thetaiotaomicron (Bt) MiaB is converted to a [3Fe-4S]0-like cluster during the methylation step of catalysis. Mössbauer characterization of the MiaB [3Fe-4S]0-like cluster revealed unusual spectroscopic properties compared to those of other well-characterized cuboidal [3Fe-4S]0 clusters. Specifically, the Fe sites of the mixed-valent moiety do not have identical Mössbauer parameters. Our results support a mechanism where the auxiliary [4Fe-4S] cluster is the direct sulfur source during catalysis.
Collapse
|
11
|
Zhou S, Pan J, Davis KM, Schaperdoth I, Wang B, Boal AK, Krebs C, Bollinger JM. Steric Enforcement of cis-Epoxide Formation in the Radical C-O-Coupling Reaction by Which ( S)-2-Hydroxypropylphosphonate Epoxidase (HppE) Produces Fosfomycin. J Am Chem Soc 2019; 141:20397-20406. [PMID: 31769979 DOI: 10.1021/jacs.9b10974] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
(S)-2-Hydroxypropylphosphonate [(S)-2-HPP, 1] epoxidase (HppE) reduces H2O2 at its nonheme-iron cofactor to install the oxirane "warhead" of the antibiotic fosfomycin. The net replacement of the C1 pro-R hydrogen of 1 by its C2 oxygen, with inversion of configuration at C1, yields the cis-epoxide of the drug [(1R,2S)-epoxypropylphosphonic acid (cis-Fos, 2)]. Here we show that HppE achieves ∼95% selectivity for C1 inversion and cis-epoxide formation via steric guidance of a radical-coupling mechanism. Published structures of the HppE·FeII·1 and HppE·ZnII·2 complexes reveal distinct pockets for C3 of the substrate and product and identify four hydrophobic residues-Leu120, Leu144, Phe182, and Leu193-close to C3 in one of the complexes. Replacement of Leu193 in the substrate C3 pocket with the bulkier Phe enhances stereoselectivity (cis:trans ∼99:1), whereas the Leu120Phe substitution in the product C3 pocket diminishes it (∼82:18). Retention of C1 configuration and trans-epoxide formation become predominant with the bulk-reducing Phe182Ala substitution in the substrate C3 pocket (∼13:87), trifluorination of C3 (∼23:77), or both (∼1:99). The effect of C3 trifluorination is counteracted by the more constrained substrate C3 pockets in the Leu193Phe (∼56:44) and Leu144Phe/Leu193Phe (∼90:10) variants. The ability of HppE to epoxidize substrate analogues bearing halogens at C3, C1, or both is inconsistent with a published hypothesis of polar cyclization via a C1 carbocation. Rather, specific enzyme-substrate contacts drive inversion of the C1 radical-as proposed in a recent computational study-to direct formation of the more potently antibacterial cis-epoxide by radicaloid C-O coupling.
Collapse
Affiliation(s)
- Shengbin Zhou
- Department of Chemistry and Department of Biochemistry & Molecular Biology , The Pennsylvania State University , University Park , Pennsylvania 16802 , United States
| | - Juan Pan
- Department of Chemistry and Department of Biochemistry & Molecular Biology , The Pennsylvania State University , University Park , Pennsylvania 16802 , United States
| | - Katherine M Davis
- Department of Chemistry and Department of Biochemistry & Molecular Biology , The Pennsylvania State University , University Park , Pennsylvania 16802 , United States
| | - Irene Schaperdoth
- Department of Chemistry and Department of Biochemistry & Molecular Biology , The Pennsylvania State University , University Park , Pennsylvania 16802 , United States
| | - Bo Wang
- Department of Chemistry and Department of Biochemistry & Molecular Biology , The Pennsylvania State University , University Park , Pennsylvania 16802 , United States
| | - Amie K Boal
- Department of Chemistry and Department of Biochemistry & Molecular Biology , The Pennsylvania State University , University Park , Pennsylvania 16802 , United States
| | - Carsten Krebs
- Department of Chemistry and Department of Biochemistry & Molecular Biology , The Pennsylvania State University , University Park , Pennsylvania 16802 , United States
| | - J Martin Bollinger
- Department of Chemistry and Department of Biochemistry & Molecular Biology , The Pennsylvania State University , University Park , Pennsylvania 16802 , United States
| |
Collapse
|
12
|
Tao L, Zhu W, Klinman JP, Britt RD. Electron Paramagnetic Resonance Spectroscopic Identification of the Fe-S Clusters in the SPASM Domain-Containing Radical SAM Enzyme PqqE. Biochemistry 2019; 58:5173-5187. [PMID: 31769977 DOI: 10.1021/acs.biochem.9b00960] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Pyrroloquinoline quinone (PQQ) is an important redox active quinocofactor produced by a wide variety of bacteria. A key step in PQQ biosynthesis is a carbon-carbon cross-link reaction between glutamate and tyrosine side chains within the ribosomally synthesized peptide substrate PqqA. This reaction is catalyzed by the radical SAM enzyme PqqE. Previous X-ray crystallographic and spectroscopic studies suggested that PqqE, like the other members of the SPASM domain family, contains two auxiliary Fe-S clusters (AuxI and AuxII) in addition to the radical SAM [4Fe-4S] cluster. However, a clear assignment of the electron paramagnetic resonance (EPR) signal of each Fe-S cluster was hindered by the isolation of a His6-tagged PqqE variant with an altered AuxI cluster. In this work, we are able to isolate soluble PqqE variants by using a less disruptive strep-tactin chromatographic approach. We have unambiguously identified the EPR signatures for four forms of Fe-S clusters present in PqqE through the use of multifrequency EPR spectroscopy: the RS [4Fe-4S] cluster, the AuxII [4Fe-4S] cluster, and two different clusters ([4Fe-4S] and [2Fe-2S]) bound in the AuxI site. The RS [4Fe-4S] cluster, the AuxII [4Fe-4S] cluster, and the [2Fe-2S] cluster form in the AuxI site can all be reduced by sodium dithionite, with g tensors of their reduced form determined as [2.040, 1.927, 1.897], [2.059, 1.940, 1.903], and [2.004, 1.958, 1.904], respectively. The AuxI [4Fe-4S] cluster that is determined on the basis of its relaxation profile can be reduced only by using low-potential reductants such as Ti(III) citrate or Eu(II)-DTPA to give rise to a g1 = 2.104 signal. Identification of the EPR signature for each cluster paves the way for further investigations of SPASM domain radical SAM enzymes.
Collapse
Affiliation(s)
- Lizhi Tao
- Department of Chemistry , University of California , Davis , California 95616 , United States
| | - Wen Zhu
- Department of Chemistry, Department of Molecular and Cell Biology, and California Institute for Quantitative Biosciences , University of California , Berkeley , California 94720 , United States
| | - Judith P Klinman
- Department of Chemistry, Department of Molecular and Cell Biology, and California Institute for Quantitative Biosciences , University of California , Berkeley , California 94720 , United States
| | - R David Britt
- Department of Chemistry , University of California , Davis , California 95616 , United States
| |
Collapse
|
13
|
Rao G, Pattenaude SA, Alwan K, Blackburn NJ, Britt RD, Rauchfuss TB. The binuclear cluster of [FeFe] hydrogenase is formed with sulfur donated by cysteine of an [Fe(Cys)(CO) 2(CN)] organometallic precursor. Proc Natl Acad Sci U S A 2019; 116:20850-5. [PMID: 31570604 DOI: 10.1073/pnas.1913324116] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The enzyme [FeFe]-hydrogenase (HydA1) contains a unique 6-iron cofactor, the H-cluster, that has unusual ligands to an Fe-Fe binuclear subcluster: CN-, CO, and an azadithiolate (adt) ligand that provides 2 S bridges between the 2 Fe atoms. In cells, the H-cluster is assembled by a collection of 3 maturases: HydE and HydF, whose roles aren't fully understood, and HydG, which has been shown to construct a [Fe(Cys)(CO)2(CN)] organometallic precursor to the binuclear cluster. Here, we report the in vitro assembly of the H-cluster in the absence of HydG, which is functionally replaced by adding a synthetic [Fe(Cys)(CO)2(CN)] carrier in the maturation reaction. The synthetic carrier and the HydG-generated analog exhibit similar infrared spectra. The carrier allows HydG-free maturation to HydA1, whose activity matches that of the native enzyme. Maturation with 13CN-containing carrier affords 13CN-labeled enzyme as verified by electron paramagnetic resonance (EPR)/electron nuclear double-resonance spectra. This synthetic surrogate approach complements existing biochemical strategies and greatly facilitates the understanding of pathways involved in the assembly of the H-cluster. As an immediate demonstration, we clarify that Cys is not the source of the carbon and nitrogen atoms in the adt ligand using pulse EPR to target the magnetic couplings introduced via a 13C3,15N-Cys-labeled synthetic carrier. Parallel mass-spectrometry experiments show that the Cys backbone is converted to pyruvate, consistent with a cysteine role in donating S in forming the adt bridge. This mechanistic scenario is confirmed via maturation with a seleno-Cys carrier to form HydA1-Se, where the incorporation of Se was characterized by extended X-ray absorption fine structure spectroscopy.
Collapse
|