1
|
Oyamada Y, Ogawa S, Fujishiro T. Nickel-chelatase activity of SirB variants mimicking the His arrangement in the naturally occurring nickel-chelatase CfbA. FEBS Open Bio 2024; 14:1291-1302. [PMID: 38923868 PMCID: PMC11301274 DOI: 10.1002/2211-5463.13849] [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: 01/27/2024] [Revised: 05/09/2024] [Accepted: 06/10/2024] [Indexed: 06/28/2024] Open
Abstract
Metal-tetrapyrrole cofactors are involved in multiple cellular functions, and chelatases are key enzymes for the biosynthesis of these cofactors. CfbA is an ancestral, homodimeric-type class II chelatase which is able to use not only Ni2+ as a physiological metal substrate, but also Co2+ as a nonphysiological substrate with higher activity than for Ni2+. The Ni/Co-chelatase function found in CfbA is also observed in SirB, a descendant, monomeric-type class II chelatase. This is despite the distinct active site structure of CfbA and SirB; specifically, CfbA shows a unique four His residue arrangement, unlike other monomeric class II chelatases such as SirB. Herein, we studied the Ni-chelatase activity of SirB variants R134H, L200H, and R134H/L200H, the latter of which mimics the His alignment of CfbA. Our results showed that the SirB R134H variant exhibited the highest Ni-chelatase activity among the SirB enzymes, which in turn suggests that the position of His134 could be more important for the Ni-chelatase activity than that of His200. The SirB R134H/L200H variant showed lower activity than R134H, despite the four His residues found in SirB R134H/L200H. CD spectroscopy showed secondary structure denaturation and a slight difficulty in Ni-binding of SirB R134H/L200H, which may be related to its lower activity. Finally, a docking simulation suggested that the His134 of the SirB R134H variant could function as a base catalyst for the Ni-chelatase reaction in a class II chelatase architecture.
Collapse
Affiliation(s)
- Yuuma Oyamada
- Department of Biochemistry and Molecular Biology, Graduate School of Science and EngineeringSaitama UniversitySaitamaJapan
| | - Shoko Ogawa
- Department of Biochemistry and Molecular Biology, Graduate School of Science and EngineeringSaitama UniversitySaitamaJapan
| | - Takashi Fujishiro
- Department of Biochemistry and Molecular Biology, Graduate School of Science and EngineeringSaitama UniversitySaitamaJapan
| |
Collapse
|
2
|
The "beauty in the beast"-the multiple uses of Priestia megaterium in biotechnology. Appl Microbiol Biotechnol 2021; 105:5719-5737. [PMID: 34263356 PMCID: PMC8390425 DOI: 10.1007/s00253-021-11424-6] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2021] [Revised: 06/17/2021] [Accepted: 06/21/2021] [Indexed: 01/05/2023]
Abstract
Abstract Over 30 years, the Gram-positive bacterium Priestia megaterium (previously known as Bacillus megaterium) was systematically developed for biotechnological applications ranging from the production of small molecules like vitamin B12, over polymers like polyhydroxybutyrate (PHB) up to the in vivo and in vitro synthesis of multiple proteins and finally whole-cell applications. Here we describe the use of the natural vitamin B12 (cobalamin) producer P. megaterium for the elucidation of the biosynthetic pathway and the subsequent systematic knowledge-based development for production purposes. The formation of PHB, a natural product of P. megaterium and potential petro-plastic substitute, is covered and discussed. Further important biotechnological characteristics of P. megaterium for recombinant protein production including high protein secretion capacity and simple cultivation on value-added carbon sources are outlined. This includes the advanced system with almost 30 commercially available expression vectors for the intracellular and extracellular production of recombinant proteins at the g/L scale. We also revealed a novel P. megaterium transcription-translation system as a complementary and versatile biotechnological tool kit. As an impressive biotechnology application, the formation of various cytochrome P450 is also critically highlighted. Finally, whole cellular applications in plant protection are completing the overall picture of P. megaterium as a versatile giant cell factory. Key points • The use of Priestia megaterium for the biosynthesis of small molecules and recombinant proteins through to whole-cell applications is reviewed. • P. megaterium can act as a promising alternative host in biotechnological production processes.
Collapse
|
3
|
Osman D, Cooke A, Young TR, Deery E, Robinson NJ, Warren MJ. The requirement for cobalt in vitamin B 12: A paradigm for protein metalation. BIOCHIMICA ET BIOPHYSICA ACTA. MOLECULAR CELL RESEARCH 2021; 1868:118896. [PMID: 33096143 PMCID: PMC7689651 DOI: 10.1016/j.bbamcr.2020.118896] [Citation(s) in RCA: 52] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/08/2020] [Revised: 10/13/2020] [Accepted: 10/14/2020] [Indexed: 12/20/2022]
Abstract
Vitamin B12, cobalamin, is a cobalt-containing ring-contracted modified tetrapyrrole that represents one of the most complex small molecules made by nature. In prokaryotes it is utilised as a cofactor, coenzyme, light sensor and gene regulator yet has a restricted role in assisting only two enzymes within specific eukaryotes including mammals. This deployment disparity is reflected in another unique attribute of vitamin B12 in that its biosynthesis is limited to only certain prokaryotes, with synthesisers pivotal in establishing mutualistic microbial communities. The core component of cobalamin is the corrin macrocycle that acts as the main ligand for the cobalt. Within this review we investigate why cobalt is paired specifically with the corrin ring, how cobalt is inserted during the biosynthetic process, how cobalt is made available within the cell and explore the cellular control of cobalt and cobalamin levels. The partitioning of cobalt for cobalamin biosynthesis exemplifies how cells assist metalation.
Collapse
Affiliation(s)
- Deenah Osman
- Department of Biosciences, Durham University, Durham DH1 3LE, UK; Department of Chemistry, Durham University, Durham DH1 3LE, UK.
| | - Anastasia Cooke
- School of Biosciences, University of Kent, Canterbury, Kent CT2 7NJ, UK.
| | - Tessa R Young
- Department of Biosciences, Durham University, Durham DH1 3LE, UK; Department of Chemistry, Durham University, Durham DH1 3LE, UK.
| | - Evelyne Deery
- School of Biosciences, University of Kent, Canterbury, Kent CT2 7NJ, UK.
| | - Nigel J Robinson
- Department of Biosciences, Durham University, Durham DH1 3LE, UK; Department of Chemistry, Durham University, Durham DH1 3LE, UK.
| | - Martin J Warren
- School of Biosciences, University of Kent, Canterbury, Kent CT2 7NJ, UK; Quadram Institute Bioscience, Norwich Research Park, Norwich NR4 7UQ, UK; Biomedical Research Centre, University of East Anglia, Norwich NR4 7TJ, UK.
| |
Collapse
|
4
|
Abstract
Modified tetrapyrroles are large macrocyclic compounds, consisting of diverse conjugation and metal chelation systems and imparting an array of colors to the biological structures that contain them. Tetrapyrroles represent some of the most complex small molecules synthesized by cells and are involved in many essential processes that are fundamental to life on Earth, including photosynthesis, respiration, and catalysis. These molecules are all derived from a common template through a series of enzyme-mediated transformations that alter the oxidation state of the macrocycle and also modify its size, its side-chain composition, and the nature of the centrally chelated metal ion. The different modified tetrapyrroles include chlorophylls, hemes, siroheme, corrins (including vitamin B12), coenzyme F430, heme d1, and bilins. After nearly a century of study, almost all of the more than 90 different enzymes that synthesize this family of compounds are now known, and expression of reconstructed operons in heterologous hosts has confirmed that most pathways are complete. Aside from the highly diverse nature of the chemical reactions catalyzed, an interesting aspect of comparative biochemistry is to see how different enzymes and even entire pathways have evolved to perform alternative chemical reactions to produce the same end products in the presence and absence of oxygen. Although there is still much to learn, our current understanding of tetrapyrrole biogenesis represents a remarkable biochemical milestone that is summarized in this review.
Collapse
Affiliation(s)
- Donald A Bryant
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, Montana 59717
| | - C Neil Hunter
- Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield S10 2TN, United Kingdom
| | - Martin J Warren
- School of Biosciences, University of Kent, Canterbury CT2 7NJ, United Kingdom
- Quadram Institute Bioscience, Norwich Research Park, Norwich NR4 7UQ, United Kingdom
| |
Collapse
|
5
|
Fujishiro T, Shimada Y, Nakamura R, Ooi M. Structure of sirohydrochlorin ferrochelatase SirB: the last of the structures of the class II chelatase family. Dalton Trans 2019; 48:6083-6090. [PMID: 30778451 DOI: 10.1039/c8dt04727h] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The crystal structure of Bacillus subtilis SirB, which catalyses the insertion of Fe2+ into the substrate sirohydrochlorin (SHC) in siroheme biosynthesis, is reported herein as the last of the structures of class II chelatases. The structure of SirB with Co2+ showed that the active site of SirB is located at the N-terminal domain with metal-binding amino acid residues His10, Glu43, and His76, which was also predicted for CbiX, but is distinct from the C-terminal active sites of CbiK and HemH. The biosynthetic model reactions using SirB, Co2+ and uroporphyrin I or protoporphyrin IX as a SHC analogue revealed that SirB showed chelatase activity for uroporphyrin I, but not for protoporphyrin IX. Simulations of tetrapyrroles docking to SirB provided an insight into its tetrapyrrole substrate recognition: SHC and uroporphyrin I were suitably bound beside the Co2+ ion-binding site at the active site cavity; protoporphyrin IX was also docked to the active site but its orientation was different from those of the other two tetrapyrroles. Summarizing the present data, it was proposed that the key structural features for substrate recognition of SirB could be the hydrophobic area at the active site as well as the substituents of the tetrapyrroles.
Collapse
Affiliation(s)
- Takashi Fujishiro
- Department of Biochemistry and Molecular Biology, Graduate School of Science and Engineering, Saitama University, 255 Shimo-Okubo, Sakura-ku, Saitama 338-8570, Japan.
| | | | | | | |
Collapse
|
6
|
Koppel N, Bisanz JE, Pandelia ME, Turnbaugh PJ, Balskus EP. Discovery and characterization of a prevalent human gut bacterial enzyme sufficient for the inactivation of a family of plant toxins. eLife 2018; 7:33953. [PMID: 29761785 PMCID: PMC5953540 DOI: 10.7554/elife.33953] [Citation(s) in RCA: 78] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2017] [Accepted: 04/11/2018] [Indexed: 12/21/2022] Open
Abstract
Although the human gut microbiome plays a prominent role in xenobiotic transformation, most of the genes and enzymes responsible for this metabolism are unknown. Recently, we linked the two-gene 'cardiac glycoside reductase' (cgr) operon encoded by the gut Actinobacterium Eggerthella lenta to inactivation of the cardiac medication and plant natural product digoxin. Here, we compared the genomes of 25 E. lenta strains and close relatives, revealing an expanded 8-gene cgr-associated gene cluster present in all digoxin metabolizers and absent in non-metabolizers. Using heterologous expression and in vitro biochemical characterization, we discovered that a single flavin- and [4Fe-4S] cluster-dependent reductase, Cgr2, is sufficient for digoxin inactivation. Unexpectedly, Cgr2 displayed strict specificity for digoxin and other cardenolides. Quantification of cgr2 in gut microbiomes revealed that this gene is widespread and conserved in the human population. Together, these results demonstrate that human-associated gut bacteria maintain specialized enzymes that protect against ingested plant toxins.
Collapse
Affiliation(s)
- Nitzan Koppel
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, United States
| | - Jordan E Bisanz
- Department of Microbiology & Immunology, University of California, San Francisco, United States
| | | | - Peter J Turnbaugh
- Department of Microbiology & Immunology, University of California, San Francisco, United States.,Chan Zuckerberg Biohub, San Francisco, United States
| | - Emily P Balskus
- Department of Chemistry and Chemical Biology, Harvard University, Cambridge, United States.,Broad Institute, Cambridge, United States
| |
Collapse
|
7
|
Walworth NG, Lee MD, Suffridge C, Qu P, Fu FX, Saito MA, Webb EA, Sañudo-Wilhelmy SA, Hutchins DA. Functional Genomics and Phylogenetic Evidence Suggest Genus-Wide Cobalamin Production by the Globally Distributed Marine Nitrogen Fixer Trichodesmium. Front Microbiol 2018; 9:189. [PMID: 29487583 PMCID: PMC5816740 DOI: 10.3389/fmicb.2018.00189] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2017] [Accepted: 01/26/2018] [Indexed: 11/17/2022] Open
Abstract
Only select prokaryotes can biosynthesize vitamin B12 (i.e., cobalamins), but these organic co-enzymes are required by all microbial life and can be vanishingly scarce across extensive ocean biomes. Although global ocean genome data suggest cyanobacteria to be a major euphotic source of cobalamins, recent studies have highlighted that >95% of cyanobacteria can only produce a cobalamin analog, pseudo-B12, due to the absence of the BluB protein that synthesizes the α ligand 5,6-dimethylbenzimidizole (DMB) required to biosynthesize cobalamins. Pseudo-B12 is substantially less bioavailable to eukaryotic algae, as only certain taxa can intracellularly remodel it to one of the cobalamins. Here we present phylogenetic, metagenomic, transcriptomic, proteomic, and chemical analyses providing multiple lines of evidence that the nitrogen-fixing cyanobacterium Trichodesmium transcribes and translates the biosynthetic, cobalamin-requiring BluB enzyme. Phylogenetic evidence suggests that the Trichodesmium DMB biosynthesis gene, bluB, is of ancient origin, which could have aided in its ecological differentiation from other nitrogen-fixing cyanobacteria. Additionally, orthologue analyses reveal two genes encoding iron-dependent B12 biosynthetic enzymes (cbiX and isiB), suggesting that iron availability may be linked not only to new nitrogen supplies from nitrogen fixation, but also to B12 inputs by Trichodesmium. These analyses suggest that Trichodesmium contains the genus-wide genomic potential for a previously unrecognized role as a source of cobalamins, which may prove to considerably impact marine biogeochemical cycles.
Collapse
Affiliation(s)
- Nathan G Walworth
- Department of Biological Sciences, University of Southern California, Los Angeles, CA, United States
| | - Michael D Lee
- Department of Biological Sciences, University of Southern California, Los Angeles, CA, United States
| | - Christopher Suffridge
- Department of Biological Sciences, University of Southern California, Los Angeles, CA, United States
| | - Pingping Qu
- Department of Biological Sciences, University of Southern California, Los Angeles, CA, United States
| | - Fei-Xue Fu
- Department of Biological Sciences, University of Southern California, Los Angeles, CA, United States
| | - Mak A Saito
- Marine Chemistry and Geochemistry Department, Woods Hole Oceanographic Institution, Woods Hole, MA, United States
| | - Eric A Webb
- Department of Biological Sciences, University of Southern California, Los Angeles, CA, United States
| | - Sergio A Sañudo-Wilhelmy
- Department of Biological Sciences, University of Southern California, Los Angeles, CA, United States
| | - David A Hutchins
- Department of Biological Sciences, University of Southern California, Los Angeles, CA, United States
| |
Collapse
|
8
|
Pallares IG, Moore TC, Escalante-Semerena JC, Brunold TC. Spectroscopic Studies of the EutT Adenosyltransferase from Salmonella enterica: Evidence of a Tetrahedrally Coordinated Divalent Transition Metal Cofactor with Cysteine Ligation. Biochemistry 2017; 56:364-375. [PMID: 28045498 DOI: 10.1021/acs.biochem.6b00750] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The EutT enzyme from Salmonella enterica, a member of the family of ATP:cobalt(I) corrinoid adenosyltransferase (ACAT) enzymes, requires a divalent transition metal ion for catalysis, with Fe(II) yielding the highest activity. EutT contains a unique cysteine-rich HX11CCX2C(83) motif (where H and the last C occupy the 67th and 83rd positions, respectively, in the amino acid sequence) not found in other ACATs and employs an unprecedented mechanism for the formation of adenosylcobalamin. Recent kinetic and spectroscopic studies of this enzyme revealed that residues in the HX11CCX2C(83) motif are required for the tight binding of the divalent metal ion and are critical for the formation of a four-coordinate (4c) cob(II)alamin [Co(II)Cbl] intermediate in the catalytic cycle. However, it remained unknown which, if any, of the residues in the HX11CCX2C(83) motif bind the divalent metal ion. To address this issue, we have characterized Co(II)-substituted wild-type EutT (EutTWT/Co) by using electronic absorption, electron paramagnetic resonance, and magnetic circular dichroism (MCD) spectroscopies. Our results indicate that the reduced catalytic activity of EutTWT/Co relative to that of the Fe(II)-containing enzyme arises from the incomplete incorporation of Co(II) ions and, thus, a decrease in the relative population of 4c Co(II)Cbl. Our MCD data for EutTWT/Co also reveal that the Co(II) ions reside in a distorted tetrahedral coordination environment with direct cysteine sulfur ligation. Additional spectroscopic studies of EutT/Co variants possessing a single alanine substitution of either His67, His75, Cys79, Cys80, or Cys83 indicate that Cys80 coordinates to the Co(II) ion, while the additional residues are important for maintaining the structural integrity and/or high affinity of the metal binding site.
Collapse
Affiliation(s)
- Ivan G Pallares
- Department of Chemistry, University of Wisconsin-Madison , Madison, Wisconsin 53706, United States
| | - Theodore C Moore
- Department of Microbiology, University of Georgia , Athens, Georgia 30602, United States
| | | | - Thomas C Brunold
- Department of Chemistry, University of Wisconsin-Madison , Madison, Wisconsin 53706, United States
| |
Collapse
|
9
|
Fang H, Dong H, Cai T, Zheng P, Li H, Zhang D, Sun J. In Vitro Optimization of Enzymes Involved in Precorrin-2 Synthesis Using Response Surface Methodology. PLoS One 2016; 11:e0151149. [PMID: 26974652 PMCID: PMC4790935 DOI: 10.1371/journal.pone.0151149] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2015] [Accepted: 02/23/2016] [Indexed: 11/19/2022] Open
Abstract
In order to maximize the production of biologically-derived chemicals, kinetic analyses are first necessary for predicting the role of enzyme components and coordinating enzymes in the same reaction system. Precorrin-2 is a key precursor of cobalamin and siroheme synthesis. In this study, we sought to optimize the concentrations of several molecules involved in precorrin-2 synthesis in vitro: porphobilinogen synthase (PBGS), porphobilinogen deaminase (PBGD), uroporphyrinogen III synthase (UROS), and S-adenosyl-l-methionine-dependent urogen III methyltransferase (SUMT). Response surface methodology was applied to develop a kinetic model designed to maximize precorrin-2 productivity. The optimal molar ratios of PBGS, PBGD, UROS, and SUMT were found to be approximately 1:7:7:34, respectively. Maximum precorrin-2 production was achieved at 0.1966 ± 0.0028 μM/min, agreeing with the kinetic model's predicted value of 0.1950 μM/min. The optimal concentrations of the cofactor S-adenosyl-L-methionine (SAM) and substrate 5-aminolevulinic acid (ALA) were also determined to be 200 μM and 5 mM, respectively, in a tandem-enzyme assay. By optimizing the relative concentrations of these enzymes, we were able to minimize the effects of substrate inhibition and feedback inhibition by S-adenosylhomocysteine on SUMT and thereby increase the production of precorrin-2 by approximately five-fold. These results demonstrate the effectiveness of kinetic modeling via response surface methodology for maximizing the production of biologically-derived chemicals.
Collapse
Affiliation(s)
- Huan Fang
- Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, China
- Key Laboratory of Systems Microbial Biotechnology, Chinese Academy of Sciences, Tianjin, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Huina Dong
- Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, China
- Key Laboratory of Systems Microbial Biotechnology, Chinese Academy of Sciences, Tianjin, China
| | - Tao Cai
- Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, China
| | - Ping Zheng
- Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, China
- Key Laboratory of Systems Microbial Biotechnology, Chinese Academy of Sciences, Tianjin, China
| | - Haixing Li
- Sino-German Joint Research Institute, Nanchang University, Nanchang, Jiangxi, China
| | - Dawei Zhang
- Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, China
- Key Laboratory of Systems Microbial Biotechnology, Chinese Academy of Sciences, Tianjin, China
| | - Jibin Sun
- Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, China
- Key Laboratory of Systems Microbial Biotechnology, Chinese Academy of Sciences, Tianjin, China
| |
Collapse
|
10
|
Abstract
This review summarizes research performed over the last 23 years on the genetics, enzyme structures and functions, and regulation of the expression of the genes encoding functions involved in adenosylcobalamin (AdoCbl, or coenzyme B12) biosynthesis. It also discusses the role of coenzyme B12 in the physiology of Salmonella enterica serovar Typhimurium LT2 and Escherichia coli. John Roth's seminal contributions to the field of coenzyme B12 biosynthesis research brought the power of classical and molecular genetic, biochemical, and structural approaches to bear on the extremely challenging problem of dissecting the steps of what has turned out to be one of the most complex biosynthetic pathways known. In E. coli and serovar Typhimurium, uro'gen III represents the first branch point in the pathway, where the routes for cobalamin and siroheme synthesis diverge from that for heme synthesis. The cobalamin biosynthetic pathway in P. denitrificans was the first to be elucidated, but it was soon realized that there are at least two routes for cobalamin biosynthesis, representing aerobic and anaerobic variations. The expression of the AdoCbl biosynthetic operon is complex and is modulated at different levels. At the transcriptional level, a sensor response regulator protein activates the transcription of the operon in response to 1,2-Pdl in the environment. Serovar Typhimurium and E. coli use ethanolamine as a source of carbon, nitrogen, and energy. In addition, and unlike E. coli, serovar Typhimurium can also grow on 1,2-Pdl as the sole source of carbon and energy.
Collapse
|
11
|
Abstract
The metal binding preferences of most metalloproteins do not match their metal requirements. Thus, metallation of an estimated 30% of metalloenzymes is aided by metal delivery systems, with ∼ 25% acquiring preassembled metal cofactors. The remaining ∼ 70% are presumed to compete for metals from buffered metal pools. Metallation is further aided by maintaining the relative concentrations of these pools as an inverse function of the stabilities of the respective metal complexes. For example, magnesium enzymes always prefer to bind zinc, and these metals dominate the metalloenzymes without metal delivery systems. Therefore, the buffered concentration of zinc is held at least a million-fold below magnesium inside most cells.
Collapse
Affiliation(s)
- Andrew W Foster
- From the Department of Chemistry and School of Biological and Biomedical Sciences, Durham University, Durham DH1 3LE, United Kingdom
| | - Deenah Osman
- From the Department of Chemistry and School of Biological and Biomedical Sciences, Durham University, Durham DH1 3LE, United Kingdom
| | - Nigel J Robinson
- From the Department of Chemistry and School of Biological and Biomedical Sciences, Durham University, Durham DH1 3LE, United Kingdom
| |
Collapse
|
12
|
Moore SJ, Mayer MJ, Biedendieck R, Deery E, Warren MJ. Towards a cell factory for vitamin B12 production in Bacillus megaterium: bypassing of the cobalamin riboswitch control elements. N Biotechnol 2014; 31:553-61. [PMID: 24657453 DOI: 10.1016/j.nbt.2014.03.003] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2013] [Revised: 03/05/2014] [Accepted: 03/05/2014] [Indexed: 12/27/2022]
Abstract
Bacillus megaterium is a bacterium that has been used in the past for the industrial production of vitamin B12 (cobalamin), the anti-pernicious anaemia factor. Cobalamin is a modified tetrapyrrole with a cobalt ion coordinated within its macrocycle. More recently, B. megaterium has been developed as a host for the high-yield production of recombinant proteins using a xylose inducible promoter system. Herein, we revisit cobalamin production in B. megaterium DSM319. We have investigated the importance of cobalt for optimum growth and cobalamin production. The cobaltochelatase (CbiX(L)) is encoded within a 14-gene cobalamin biosynthetic (cbi) operon, whose gene-products oversee the transformation of uroporphyrinogen III into adenosylcobyrinic acid a,c-diamide, a key precursor of cobalamin synthesis. The production of CbiX(L) in response to exogenous cobalt was monitored. The metal was found to stimulate cobalamin biosynthesis and decrease the levels of CbiX(L). From this we were able to show that the entire cbi operon is transcriptionally regulated by a B12-riboswitch, with a switch-off point at approximately 5 nM cobalamin. To bypass the effects of the B12-riboswitch the cbi operon was cloned without these regulatory elements. Growth of these strains on minimal media supplemented with glycerol as a carbon source resulted in significant increases in cobalamin production (up to 200 μg L(-1)). In addition, a range of partially amidated intermediates up to adenosylcobyric acid was detected. These findings outline a potential way to develop B. megaterium as a cell factory for cobalamin production using cheap raw materials.
Collapse
Affiliation(s)
- Simon J Moore
- School of Biosciences, University of Kent, Giles Lane, Canterbury, Kent CT2 7NJ, UK
| | - Matthias J Mayer
- School of Biosciences, University of Kent, Giles Lane, Canterbury, Kent CT2 7NJ, UK
| | - Rebekka Biedendieck
- Institute of Microbiology, Technische Universität Braunschweig, Braunschweig, Germany
| | - Evelyne Deery
- School of Biosciences, University of Kent, Giles Lane, Canterbury, Kent CT2 7NJ, UK
| | - Martin J Warren
- School of Biosciences, University of Kent, Giles Lane, Canterbury, Kent CT2 7NJ, UK.
| |
Collapse
|
13
|
Verma D, Satyanarayana T. Production of cellulase-free xylanase by the recombinant Bacillus subtilis and its applicability in paper pulp bleaching. Biotechnol Prog 2013; 29:1441-7. [PMID: 24124029 DOI: 10.1002/btpr.1826] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2013] [Revised: 09/29/2013] [Indexed: 11/11/2022]
Abstract
A metagenomic xylanase gene (Mxyl) was successfully cloned into shuttle vector pWH1520 and expressed in Bacillus subtilis extracellularly. On induction with xylose, recombinant xylanase secretion commenced after 6 h. Identifying critical variables for recombinant xylanase production by one-variable-at-time approach followed by optimization of the selected variables (xylose, inoculum density, incubation density) by response surface methodology (RSM) led to three-fold enhancement in extracellular xylanase production (119 U mL(-1) ). When the pulp was treated with recombinant xylanase at 80°C and pH 9.0, kappa number of the pulp was reduced with concomitant increase in brightness and 24% reduction in chlorine consumption. This is the first report on the expression of metagenomic xylanase gene in Bacillus subtilis extracellularly and its utility in developing an environment-friendly pulp bleaching process.
Collapse
Affiliation(s)
- Digvijay Verma
- Dept. of Microbiology, University of Delhi South Campus, New Delhi, 110021, India
| | | |
Collapse
|
14
|
Patterson CJ, Pernil R, Dainty SJ, Chakrabarti B, Henry CE, Money VA, Foster AW, Robinson NJ. Co(ll)-detection does not follow Kco(ll) gradient: channelling in Co(ll)-sensing. Metallomics 2013; 5:352-62. [PMID: 23420021 DOI: 10.1039/c3mt20241k] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The MerR-like transcriptional activator CoaR detects surplus Co(ll) to regulate Co(ll) efflux in a cyanobacterium. This organism also has cytosolic metal-sensors from three further families represented by Zn(ll)-sensors ZiaR and Zur plus Ni(ll)-sensor InrS. Here we discover by competition with Fura-2 that CoaR has KCo(ll) weaker than 7 × 10(-8) M, which is weaker than ZiaR, Zur and InrS (KCo(ll) = 6.94 ± 1.3 × 10(-10) M; 4.56 ± 0.16 × 10(-10) M; and 7.69 ± 1.1 × 10(-9) M respectively). KCo(ll) for CoaR is also weak in the CoaR-DNA adduct. Further, Co(ll) promotes DNA-dissociation by ZiaR and DNA-association by Zur in vitro in a manner analogous to Zn(ll), as monitored by fluorescence anisotropy. After 48 h exposure to maximum non-inhibitory [Co(ll)], CoaR responds in vivo yet the two Zn(ll)-sensors do not, despite their tighter KCo(ll) and despite Co(ll) triggering allostery in ZiaR and Zur in vitro. These data imply that the two Zn(ll) sensors fail to respond because they fail to gain access to Co(ll) under these conditions in vivo. Several lines of evidence suggest that CoaR is membrane associated via a domain with sequence similarity to precorrin isomerase, an enzyme of vitamin B12 biosynthesis. Moreover, site directed mutagenesis reveals that transcriptional activation requires CoaR residues that are predicted to form hydrogen bonds to a tetrapyrrole. The Co(ll)-requiring vitamin B12 biosynthetic pathway is also membrane associated suggesting putative mechanisms by which Co(ll)-containing tetrapyrroles and/or Co(ll) ions are channelled to CoaR.
Collapse
Affiliation(s)
- Carl J Patterson
- School/Department of Biological and Biomedical Sciences, Biophysical Sciences Institute, Durham University, DH1 3LE, UK
| | | | | | | | | | | | | | | |
Collapse
|
15
|
Elucidation of the anaerobic pathway for the corrin component of cobalamin (vitamin B12). Proc Natl Acad Sci U S A 2013; 110:14906-11. [PMID: 23922391 DOI: 10.1073/pnas.1308098110] [Citation(s) in RCA: 78] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
It has been known for the past 20 years that two pathways exist in nature for the de novo biosynthesis of the coenzyme form of vitamin B12, adenosylcobalamin, representing aerobic and anaerobic routes. In contrast to the aerobic pathway, the anaerobic route has remained enigmatic because many of its intermediates have proven technically challenging to isolate, because of their inherent instability. However, by studying the anaerobic cobalamin biosynthetic pathway in Bacillus megaterium and using homologously overproduced enzymes, it has been possible to isolate all of the intermediates between uroporphyrinogen III and cobyrinic acid. Consequently, it has been possible to detail the activities of purified cobinamide biosynthesis (Cbi) proteins CbiF, CbiG, CbiD, CbiJ, CbiET, and CbiC, as well as show the direct in vitro conversion of 5-aminolevulinic acid into cobyrinic acid using a mixture of 14 purified enzymes. This approach has resulted in the isolation of the long sought intermediates, cobalt-precorrin-6A and -6B and cobalt-precorrin-8. EPR, in particular, has proven an effective technique in following these transformations with the cobalt(II) paramagnetic electron in the dyz orbital, rather than the typical dz2. This result has allowed us to speculate that the metal ion plays an unexpected role in assisting the interconversion of pathway intermediates. By determining a function for all of the pathway enzymes, we complete the tool set for cobalamin biosynthesis and pave the way for not only enhancing cobalamin production, but also design of cobalamin derivatives through their combinatorial use and modification.
Collapse
|
16
|
Padmanabhan B, Yokoyama S, Bessho Y. Crystal structure of putative CbiT from Methanocaldococcus jannaschii: an intermediate enzyme activity in cobalamin (vitamin B12) biosynthesis. BMC STRUCTURAL BIOLOGY 2013; 13:10. [PMID: 23688113 PMCID: PMC3672029 DOI: 10.1186/1472-6807-13-10] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/02/2013] [Accepted: 05/10/2013] [Indexed: 11/10/2022]
Abstract
BACKGROUND In the anaerobic pathway of cobalamin (vitamin B12) synthesis, the CbiT enzyme plays two roles, as a cobalt-precorrin-7 C15-methyltransferase and a C12-decarboxylase, to produce the intermediate, cobalt-precorrin 8. RESULTS The primary structure of the hypothetical protein MJ0391, from Methanocaldococcus jannaschii, suggested that MJ0391 is a putative CbiT. Here, we report the crystal structure of MJ0391, solved by the MAD procedure and refined to final R-factor and R-free values of 19.8 & 27.3%, respectively, at 2.3 Å resolution. The asymmetric unit contains two NCS molecules, and the intact tetramer generated by crystallographic symmetry may be functionally important. The overall tertiary structure and the tetrameric arrangements are highly homologous to those found in MT0146/CbiT from Methanobacterium thermoautotrophicum. CONCLUSIONS The conservation of functional residues in the binding site for the co-factor, AdoMet, and in the putative precorrin-7 binding pocket suggested that MJ0391 may also possess CbiT activity. The putative function of MJ0391 is discussed, based on structural homology.
Collapse
Affiliation(s)
- Balasundaram Padmanabhan
- Department of Biophysics, National Institute of Mental Health and Neuro Sciences (NIMHANS), Bangalore 560029, India,RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo, Hyogo 679-5148, Japan
| | - Shigeyuki Yokoyama
- RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo, Hyogo 679-5148, Japan,Department of Biophysics and Biochemistry, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Yoshitaka Bessho
- RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo, Hyogo 679-5148, Japan,RIKEN SPring-8 Center, Harima Institute, 1-1-1 Kouto, Sayo, Hyogo 679-5148, Japan
| |
Collapse
|
17
|
Moore SJ, Biedendieck R, Lawrence AD, Deery E, Howard MJ, Rigby SEJ, Warren MJ. Characterization of the enzyme CbiH60 involved in anaerobic ring contraction of the cobalamin (vitamin B12) biosynthetic pathway. J Biol Chem 2013; 288:297-305. [PMID: 23155054 PMCID: PMC3537027 DOI: 10.1074/jbc.m112.422535] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2012] [Revised: 11/12/2012] [Indexed: 11/06/2022] Open
Abstract
The anaerobic pathway for the biosynthesis of cobalamin (vitamin B(12)) has remained poorly characterized because of the sensitivity of the pathway intermediates to oxygen and the low activity of enzymes. One of the major bottlenecks in the anaerobic pathway is the ring contraction step, which has not been observed previously with a purified enzyme system. The Gram-positive aerobic bacterium Bacillus megaterium has a complete anaerobic pathway that contains an unusual ring contraction enzyme, CbiH(60), that harbors a C-terminal extension with sequence similarity to the nitrite/sulfite reductase family. To improve solubility, the enzyme was homologously produced in the host B. megaterium DSM319. CbiH(60) was characterized by electron paramagnetic resonance and shown to contain a [4Fe-4S] center. Assays with purified recombinant CbiH(60) demonstrate that the enzyme converts both cobalt-precorrin-3 and cobalt factor III into the ring-contracted product cobalt-precorrin-4 in high yields, with the latter transformation dependent upon DTT and an intact Fe-S center. Furthermore, the ring contraction process was shown not to involve a change in the oxidation state of the central cobalt ion of the macrocycle.
Collapse
Affiliation(s)
- Simon J. Moore
- From the School of Biosciences, University of Kent, Canterbury, Kent CT2 7NJ, United Kingdom
| | - Rebekka Biedendieck
- From the School of Biosciences, University of Kent, Canterbury, Kent CT2 7NJ, United Kingdom
- the Institute of Microbiology, Technische Universität Braunschweig, Braunschweig D-38106, Germany, and
| | - Andrew D. Lawrence
- From the School of Biosciences, University of Kent, Canterbury, Kent CT2 7NJ, United Kingdom
| | - Evelyne Deery
- From the School of Biosciences, University of Kent, Canterbury, Kent CT2 7NJ, United Kingdom
| | - Mark J. Howard
- From the School of Biosciences, University of Kent, Canterbury, Kent CT2 7NJ, United Kingdom
| | - Stephen E. J. Rigby
- the Manchester Interdisciplinary Biocentre, Faculty of Life Sciences, University of Manchester, Manchester M1 7DN, United Kingdom
| | - Martin J. Warren
- From the School of Biosciences, University of Kent, Canterbury, Kent CT2 7NJ, United Kingdom
| |
Collapse
|
18
|
Abstract
Vitamin B12 (cobalamin) is a cobalt-containing modified tetrapyrrole that is an essential nutrient for higher animals. Its biosynthesis is restricted to certain bacteria and requires approximately 30 enzymatic steps for its complete de novo construction. Remarkably, two distinct biosynthetic pathways exist, which are termed the aerobic and anaerobic routes. The anaerobic pathway has yet to be fully characterized due to the inherent instability of its oxygen-sensitive intermediates. Bacillus megaterium, a bacterium previously used for the commercial production of cobalamin, has a complete anaerobic pathway and this organism is now being used to investigate the anaerobic B12 pathway through the application of recent advances in recombinant protein production. The present paper provides a summary of recent findings in the anaerobic pathway and future perspectives.
Collapse
|
19
|
Characterization of the evolutionarily conserved iron–sulfur cluster of sirohydrochlorin ferrochelatase from Arabidopsis thaliana. Biochem J 2012; 444:227-37. [DOI: 10.1042/bj20111993] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Sirohaem is a cofactor of nitrite and sulfite reductases, essential for assimilation of nitrogen and sulfur. Sirohaem is synthesized from the central tetrapyrrole intermediate uroporphyrinogen III by methylation, oxidation and ferrochelation reactions. In Arabidopsis thaliana, the ferrochelation step is catalysed by sirohydrochlorin ferrochelatase (SirB), which, unlike its counterparts in bacteria, contains an [Fe–S] cluster. We determined the cluster to be a [4Fe–4S] type, which quickly oxidizes to a [2Fe–2S] form in the presence of oxygen. We also identified the cluster ligands as four conserved cysteine residues located at the C-terminus. A fifth conserved cysteine residue, Cys135, is not involved in ligating the cluster directly, but influences the oxygen-sensitivity of the [4Fe–4S] form, and possibly the affinity for the substrate metal. Substitution mutants of the enzyme lacking the Fe–S cluster or Cys135 retain the same specific activity in vitro and dimeric quaternary structure as the wild-type enzyme. The mutant variants also rescue a defined Escherichia coli sirohaem-deficient mutant. However, the mutant enzymes cannot complement Arabidopsis plants with a null AtSirB mutation, which exhibits post-germination arrest. These observations suggest an important physiological role for the Fe–S cluster in planta, highlighting the close association of iron, sulfur and tetrapyrrole metabolism.
Collapse
|
20
|
Xu XM, Møller SG. Iron-sulfur clusters: biogenesis, molecular mechanisms, and their functional significance. Antioxid Redox Signal 2011; 15:271-307. [PMID: 20812788 DOI: 10.1089/ars.2010.3259] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Iron-sulfur clusters [Fe-S] are small, ubiquitous inorganic cofactors representing one of the earliest catalysts during biomolecule evolution and are involved in fundamental biological reactions, including regulation of enzyme activity, mitochondrial respiration, ribosome biogenesis, cofactor biogenesis, gene expression regulation, and nucleotide metabolism. Although simple in structure, [Fe-S] biogenesis requires complex protein machineries and pathways for assembly. [Fe-S] are assembled from cysteine-derived sulfur and iron onto scaffold proteins followed by transfer to recipient apoproteins. Several predominant iron-sulfur biogenesis systems have been identified, including nitrogen fixation (NIF), sulfur utilization factor (SUF), iron-sulfur cluster (ISC), and cytosolic iron-sulfur protein assembly (CIA), and many protein components have been identified and characterized. In eukaryotes ISC is mainly localized to mitochondria, cytosolic iron-sulfur protein assembly to the cytosol, whereas plant sulfur utilization factor is localized mainly to plastids. Because of this spatial separation, evidence suggests cross-talk mediated by organelle export machineries and dual targeting mechanisms. Although research efforts in understanding iron-sulfur biogenesis has been centered on bacteria, yeast, and plants, recent efforts have implicated inappropriate [Fe-S] biogenesis to underlie many human diseases. In this review we detail our current understanding of [Fe-S] biogenesis across species boundaries highlighting evolutionary conservation and divergence and assembling our knowledge into a cellular context.
Collapse
Affiliation(s)
- Xiang Ming Xu
- Centre for Organelle Research CORE, University of Stavanger, Norway
| | | |
Collapse
|
21
|
Storbeck S, Saha S, Krausze J, Klink BU, Heinz DW, Layer G. Crystal structure of the heme d1 biosynthesis enzyme NirE in complex with its substrate reveals new insights into the catalytic mechanism of S-adenosyl-L-methionine-dependent uroporphyrinogen III methyltransferases. J Biol Chem 2011; 286:26754-67. [PMID: 21632530 DOI: 10.1074/jbc.m111.239855] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
During the biosynthesis of heme d(1), the essential cofactor of cytochrome cd(1) nitrite reductase, the NirE protein catalyzes the methylation of uroporphyrinogen III to precorrin-2 using S-adenosyl-L-methionine (SAM) as the methyl group donor. The crystal structure of Pseudomonas aeruginosa NirE in complex with its substrate uroporphyrinogen III and the reaction by-product S-adenosyl-L-homocysteine (SAH) was solved to 2.0 Å resolution. This represents the first enzyme-substrate complex structure for a SAM-dependent uroporphyrinogen III methyltransferase. The large substrate binds on top of the SAH in a "puckered" conformation in which the two pyrrole rings facing each other point into the same direction either upward or downward. Three arginine residues, a histidine, and a methionine are involved in the coordination of uroporphyrinogen III. Through site-directed mutagenesis of the nirE gene and biochemical characterization of the corresponding NirE variants the amino acid residues Arg-111, Glu-114, and Arg-149 were identified to be involved in NirE catalysis. Based on our structural and biochemical findings, we propose a potential catalytic mechanism for NirE in which the methyl transfer reaction is initiated by an arginine catalyzed proton abstraction from the C-20 position of the substrate.
Collapse
Affiliation(s)
- Sonja Storbeck
- Institute of Microbiology, Technische Universität Braunschweig, 38106 Braunschweig, Germany
| | | | | | | | | | | |
Collapse
|
22
|
Evolution in a family of chelatases facilitated by the introduction of active site asymmetry and protein oligomerization. Proc Natl Acad Sci U S A 2010; 108:97-102. [PMID: 21173279 DOI: 10.1073/pnas.1014298108] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The class II chelatases associated with heme, siroheme, and cobalamin biosynthesis are structurally related enzymes that insert a specific metal ion (Fe(2+) or Co(2+)) into the center of a modified tetrapyrrole (protoporphyrin or sirohydrochlorin). The structures of two related class II enzymes, CbiX(S) from Archaeoglobus fulgidus and CbiK from Salmonella enterica, that are responsible for the insertion of cobalt along the cobalamin biosynthesis pathway are presented in complex with their metallated product. A further structure of a CbiK from Desulfovibrio vulgaris Hildenborough reveals how cobalt is bound at the active site. The crystal structures show that the binding of sirohydrochlorin is distinctly different to porphyrin binding in the protoporphyrin ferrochelatases and provide a molecular overview of the mechanism of chelation. The structures also give insights into the evolution of chelatase form and function. Finally, the structure of a periplasmic form of Desulfovibrio vulgaris Hildenborough CbiK reveals a novel tetrameric arrangement of its subunits that are stabilized by the presence of a heme b cofactor. Whereas retaining colbaltochelatase activity, this protein has acquired a central cavity with the potential to chaperone or transport metals across the periplasmic space, thereby evolving a new use for an ancient protein subunit.
Collapse
|
23
|
Gene cloning, characterization, and heterologous expression of levansucrase from Bacillus amyloliquefaciens. J Ind Microbiol Biotechnol 2009; 37:195-204. [PMID: 19916084 DOI: 10.1007/s10295-009-0664-2] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2009] [Accepted: 10/25/2009] [Indexed: 10/20/2022]
Abstract
Although levan produced by Bacillus amyloliquefaciens is known to have efficient immunostimulant property which gives 100% survival of common carp when infected with Aeromonas hydrophila, no detailed reports are available describing kinetic studies of D: -glucose production and levan formation. In this study, we cloned and characterized the enzymatic kinetics using levansucrase expressed in Escherichia coli. Optimum pH for D: -glucose production and levan formation was 6.0 and 8.0, respectively, whereas optimum temperature was 30 degrees C and 4 degrees C, respectively. The K (m) and V (max) values for levansucrase were calculated to be 47.81 mM sucrose and 57.47 1mole/min mg protein, respectively. Prominent expression of levansucrase was obtained through xylose induction in Bacillus megaterium, where most of the His(6)-tagged protein was secreted into the culture broth, giving levansucrase activity of 12,906 U/l. Response-surface methodology (RSM) was further employed to optimize the fermentation conditions and improve the level of levansucrase production. Maximum levansucrase activity of 20,251 U/l was obtained in 12 h of fermentation carried out at 28 degrees C, starting induction with 0.735% xylose when A (600) was 1.2, which was 1.6- and 62-fold higher than those obtained in the nonoptimized conditions for the recombinant strain and the native strain, respectively.
Collapse
|
24
|
Storbeck S, Walther J, Müller J, Parmar V, Schiebel HM, Kemken D, Dülcks T, Warren MJ, Layer G. The Pseudomonas aeruginosa nirE gene encodes the S-adenosyl-L-methionine-dependent uroporphyrinogen III methyltransferase required for heme d1 biosynthesis. FEBS J 2009; 276:5973-82. [DOI: 10.1111/j.1742-4658.2009.07306.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
|
25
|
Schroeder S, Lawrence AD, Biedendieck R, Rose RS, Deery E, Graham RM, McLean KJ, Munro AW, Rigby SEJ, Warren MJ. Demonstration that CobG, the monooxygenase associated with the ring contraction process of the aerobic cobalamin (vitamin B12) biosynthetic pathway, contains an Fe-S center and a mononuclear non-heme iron center. J Biol Chem 2008; 284:4796-805. [PMID: 19068481 DOI: 10.1074/jbc.m807184200] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The ring contraction process that occurs during cobalamin (vitamin B(12)) biosynthesis is mediated via the action of two enzymes, CobG and CobJ. The first of these generates a tertiary alcohol at the C-20 position of precorrin-3A by functioning as a monooxygenase, a reaction that also forms a gamma lactone with the acetic acid side chain on ring A. The product, precorrin-3B, is then acted upon by CobJ, which methylates at the C-17 position and promotes ring contraction of the macrocycle by catalyzing a masked pinacol rearrangement. Here, we report the characterization of CobG enzymes from Pseudomonas denitrificans and Brucella melitensis. We show that both contain a [4Fe-4S] center as well as a mononuclear non-heme iron. Although both enzymes are active in vivo, the P. denitrificans enzyme was found to be inactive in vitro. Further analysis of this enzyme revealed that the mononuclear non-heme iron was not reducible, and it was concluded that it is rapidly inactivated once it is released from the bacterial cell. In contrast, the B. melitensis enzyme was found to be fully active in vitro and the mononuclear non-heme iron was reducible by dithionite. The reduced mononuclear non-heme was able to react with the oxygen analogue NO, but only in the presence of the substrate precorrin-3A. The cysteine residues responsible for binding the Fe-S center were identified by site-directed mutagenesis. A mechanism for CobG is presented.
Collapse
Affiliation(s)
- Susanne Schroeder
- Protein Science Group, Department of Biosciences, University of Kent, Canterbury, Kent CT27NJ, United Kingdom
| | | | | | | | | | | | | | | | | | | |
Collapse
|
26
|
Lobo SAL, Brindley AA, Romão CV, Leech HK, Warren MJ, Saraiva LM. Two Distinct Roles for Two Functional Cobaltochelatases (CbiK) in Desulfovibrio vulgaris Hildenborough. Biochemistry 2008; 47:5851-7. [DOI: 10.1021/bi800342c] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Susana A. L. Lobo
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Avenida da Republica (EAN), 2780-157 Oeiras, Portugal, and Protein Science Group, Department of Biosciences, University of Kent, Canterbury, Kent CT2 7NJ, United Kingdom
| | - Amanda A. Brindley
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Avenida da Republica (EAN), 2780-157 Oeiras, Portugal, and Protein Science Group, Department of Biosciences, University of Kent, Canterbury, Kent CT2 7NJ, United Kingdom
| | - Célia V. Romão
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Avenida da Republica (EAN), 2780-157 Oeiras, Portugal, and Protein Science Group, Department of Biosciences, University of Kent, Canterbury, Kent CT2 7NJ, United Kingdom
| | - Helen K. Leech
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Avenida da Republica (EAN), 2780-157 Oeiras, Portugal, and Protein Science Group, Department of Biosciences, University of Kent, Canterbury, Kent CT2 7NJ, United Kingdom
| | - Martin J. Warren
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Avenida da Republica (EAN), 2780-157 Oeiras, Portugal, and Protein Science Group, Department of Biosciences, University of Kent, Canterbury, Kent CT2 7NJ, United Kingdom
| | - Lígia M. Saraiva
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Avenida da Republica (EAN), 2780-157 Oeiras, Portugal, and Protein Science Group, Department of Biosciences, University of Kent, Canterbury, Kent CT2 7NJ, United Kingdom
| |
Collapse
|
27
|
Radha S, Gunasekaran P. Cloning and expression of keratinase gene in Bacillus megaterium and optimization of fermentation conditions for the production of keratinase by recombinant strain. J Appl Microbiol 2008; 103:1301-10. [PMID: 17897234 DOI: 10.1111/j.1365-2672.2007.03372.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
AIMS Cloning and expression of keratinase gene in Bacillus megaterium and optimization of fermentation conditions for the production of keratinase by recombinant strain. METHODS AND RESULTS The keratinase gene with and without leader sequence from the chromosomal DNA of Bacillus licheniformis MKU3 was amplified by PCR and cloned into pET30b and transferred into Escherichia coli BL21. The ker gene without leader sequence only expressed in E. coli and the recombinant strain produced an intracellular keratinase activity of 74.3 U ml(-1). The ker gene was further subcloned into E. coli-Bacillus shuttle vector, pWH1520. Bacillus megaterium ATCC 14945 carrying the recombinant plasmid pWHK3 expressed the ker gene placed under xylA promoter and produced an extracellular keratinase activity of 95 U ml(-1). Response surface methodology (RSM) was employed to optimize the fermentation condition and to improve the level of keratinase production by the recombinant strain. A maximum keratinolytic activity of 166.2 U ml(-1) (specific activity, 33.25 U mg(-1)) was obtained in 18 h of the fermentation carried out with an initial inoculum of 0.4 OD600 nm and xylose concentration of 0.75% w/v. CONCLUSIONS Bacillus licheniformis keratinase was cloned and successfully expressed using T7 promoter in E. coli and xylose inducible expression system in B. megaterium. Response surface methodology was employed to optimize the process parameters, which resulted in a three-fold higher level of keratinase production by the recombinant B. megaterium (pWHK3) than the wild type strain B. licheniformis MKU3. SIGNIFICANCE AND IMPACT OF THE STUDY This study suggests that B. megaterium is a suitable host for the expression of cloned genes from heterologous origin. Optimization of fermentation conditions improved the keratinase production by B. megaterium (pWHK3) and suggested that this recombinant strain could be used for the production of keratinase.
Collapse
Affiliation(s)
- S Radha
- Department of Genetics, Center for Excellence in Genomic Sciences, School of Biological Sciences, Madurai Kamaraj University, Madurai, India
| | | |
Collapse
|
28
|
Sirijovski N, Mamedov F, Olsson U, Styring S, Hansson M. Rhodobacter capsulatus magnesium chelatase subunit BchH contains an oxygen sensitive iron-sulfur cluster. Arch Microbiol 2007; 188:599-608. [PMID: 17639347 DOI: 10.1007/s00203-007-0282-1] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2007] [Revised: 06/01/2007] [Accepted: 06/16/2007] [Indexed: 11/29/2022]
Abstract
Magnesium chelatase is the first unique enzyme of the bacteriochlorophyll biosynthetic pathway. It consists of three subunits (BchI, BchD, and BchH). Amino acid sequence analysis of the Rhodobacter capsulatus BchH revealed a novel cysteine motif (393CX2CX3CX14C) that was found in only six other proteobacteria (CX2CX3CX11-14C). The cysteine motif is likely to coordinate an unprecedented [Fe-S] cluster. Purified BchH demonstrated absorbance in the 460 nm region. This absorbance was abolished in BchH proteins with alanine substitutions at positions Cys396 and Cys414. These modified proteins were also EPR silent. In contrast, wild type BchH protein in the reduced state showed EPR signals resembling those of a [4Fe-4S] cluster with rhombic symmetry and g values at 1.90, 1.93, and 2.09, superimposed with a [3Fe-4S] cluster centered at g = 2.02. The [3Fe-4S] signal was observed independently of the [4Fe-4S] signal under oxidizing conditions. Mg-chelatase activity assays showed that the cluster is not catalytic. We suggest that the [4Fe-4S] and [3Fe-4S] signals originate from a single coordination site on the monomeric BchH protein and that the [4Fe-4S] cluster is sensitive to oxidation. It is speculated that the cluster participates in the switching between aerobic and anaerobic life of the proteobacteria.
Collapse
Affiliation(s)
- Nick Sirijovski
- Department of Biochemistry, Center for Molecular Protein Science, Lund University, PO Box 124, 221 00 Lund, Sweden.
| | | | | | | | | |
Collapse
|
29
|
Biedendieck R, Yang Y, Deckwer WD, Malten M, Jahn D. Plasmid system for the intracellular production and purification of affinity-tagged proteins in Bacillus megaterium. Biotechnol Bioeng 2007; 96:525-37. [PMID: 16964623 DOI: 10.1002/bit.21145] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
A multiple vector system for the intracellular high-level production of affinity tagged recombinant proteins in Bacillus megaterium was developed. The N- and C-terminal fusion of a protein of interest to a Strep II and a His(6)-tag is possible. Corresponding genes are expressed under the control of a xylose-inducible promoter in a xylose isomerase deficient host strain. The exemplatory protein production of green fluorescent protein (GFP) showed differences in produced and recovered protein amounts in dependence of the employed affinity tag and its N- or C-terminal location. Up to 9 mg GFP per liter shake flask culture were purified using one-step affinity chromatography. Integration of a protease cleavage site into the recombinant fusion protein allowed tag removal via tobacco etch virus (TEV) protease or Factor Xa treatment and a second affinity chromatographic step. Up to 274 mg/L culture were produced at 52 g CDW/L using a glucose limited fedbatch cultivation. GFP production and viability of the production host were followed by flow cytometry.
Collapse
Affiliation(s)
- Rebekka Biedendieck
- Institute of Microbiology, Technical University Braunschweig, Spielmannstrasse 7, D-38106 Braunschweig, Germany
| | | | | | | | | |
Collapse
|
30
|
Abstract
Cells require metal ions as cofactors for the assembly of metalloproteins. Principally one has to distinguish between metal ions that are directly incorporated into their cognate sites on proteins and those metal ions that have to become part of prosthetic groups, cofactors or complexes prior to insertion of theses moieties into target proteins. Molybdenum is only active as part of the molybdenum cofactor, iron can be part of diverse Fe-S clusters or of the heme group, while copper ions are directly delivered to their targets. We will focus in greater detail on molybdenum metabolism because molybdenum metabolism is a good example for demonstrating the role and the network of metals in metabolism: each of the three steps in the pathway of molybdenum cofactor formation depends on a different metal (iron, copper, molybdenum) and also the enzymes finally harbouring the molybdenum cofactor need additional metal-containing groups to function (iron sulfur-clusters, heme-iron).
Collapse
Affiliation(s)
- Ralf R Mendel
- Department of Plant Biology, Technical University of Braunschweig, 38106, Braunschweig, Germany.
| | | | | | | |
Collapse
|
31
|
Holliday GL, Thornton JM, Marquet A, Smith AG, Rébeillé F, Mendel R, Schubert HL, Lawrence AD, Warren MJ. Evolution of enzymes and pathways for the biosynthesis of cofactors. Nat Prod Rep 2007; 24:972-87. [PMID: 17898893 DOI: 10.1039/b703107f] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The evolution of metabolic pathways is discussed with reference to the biosynthesis of a number of vitamins and cofactors. Retrograde and patchwork models are highlighted and their relevance to our knowledge of pathway processes and enzymes is examined. Pathway complexity is explained in terms of the acquisition of broad specificity enzymes.
Collapse
Affiliation(s)
- Gemma L Holliday
- European Bioinformatics Institute, Wellcome Trust Genome Campus, Hinxton, UK CB10 1SD.
| | | | | | | | | | | | | | | | | |
Collapse
|
32
|
Yin J, Xu LX, Cherney MM, Raux-Deery E, Bindley AA, Savchenko A, Walker JR, Cuff ME, Warren MJ, James MNG. Crystal structure of the vitamin B12 biosynthetic cobaltochelatase, CbiXS, from Archaeoglobus fulgidus. ACTA ACUST UNITED AC 2006; 7:37-50. [PMID: 16835730 DOI: 10.1007/s10969-006-9008-x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2006] [Accepted: 04/20/2006] [Indexed: 10/24/2022]
Abstract
The Archaeoglobus fulgidus gene af0721 encodes CbiX(S), a small cobaltochelatase associated with the anaerobic biosynthesis of vitamin B12 (cobalamin). The protein was shown to have activity both in vivo and in vitro, catalyzing the insertion of Co2+ into sirohydrochlorin. The structure of CbiX(S) was determined in two different crystal forms and was shown to consist of a central mixed beta-sheet flanked by four alpha-helices, one of which originates in the C-terminus of a neighboring molecule. CbiX(S) is about half the size of other Class II tetrapyrrole chelatases. The overall topography of CbiX(S) exhibits substantial resemblance to both the N- and C-terminal regions of several members of the Class II metal chelatases involved in tetrapyrrole biosynthesis. Two histidines (His10 and His74), are in similar positions as the catalytic histidine residues in the anaerobic cobaltochelatase CbiK (His145 and His207). In light of the hypothesis that suggests the larger chelatases evolved via gene duplication and fusion from a CbiX(S)-like enzyme, the structure of AF0721 may represent that of an "ancestral" precursor of class II metal chelatases.
Collapse
Affiliation(s)
- Jiang Yin
- Group in Protein Structure and Function, Department of Biochemistry, University of Alberta, Edmonton, AB, Canada, T6G 2H7
| | | | | | | | | | | | | | | | | | | |
Collapse
|
33
|
Shepherd M, Dailey T, Dailey H. A new class of [2Fe-2S]-cluster-containing protoporphyrin (IX) ferrochelatases. Biochem J 2006; 397:47-52. [PMID: 16548850 PMCID: PMC1479749 DOI: 10.1042/bj20051967] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Protoporphyrin (IX) ferrochelatase catalyses the insertion of ferrous iron into protoporphyrin IX to form haem. These ferrochelatases exist as monomers and dimers, both with and without [2Fe-2S] clusters. The motifs for [2Fe-2S] cluster co-ordination are varied, but in all cases previously reported, three of the four cysteine ligands are present in the 30 C-terminal residues and the fourth ligand is internal. In the present study, we demonstrate that a group of micro-organisms exist which possess protoporphyrin (IX) ferrochelatases containing [2Fe-2S] clusters that are co-ordinated by a group of four cysteine residues contained in an internal amino acid segment of approx. 20 residues in length. This suggests that these ferrochelatases have evolved along a different lineage than other bacterial protoporphyrin (IX) ferrochelatases. For example, Myxococcus xanthus protoporphyrin (IX) ferrochelatase ligates a [2Fe-2S] cluster via cysteine residues present in an internal segment. Site-directed mutagenesis of this ferrochelatase demonstrates that changing one cysteine ligand into serine results in loss of the cluster, but unlike eukaryotic protoporphyrin (IX) ferrochelatases, this enzyme retains its activity. These data support a role for the [2Fe-2S] cluster in iron affinity, and strongly suggest convergent evolution of this feature in prokaryotes.
Collapse
Affiliation(s)
- Mark Shepherd
- Biomedical and Health Sciences Institute, Paul D. Coverdell Center, University of Georgia, Athens, GA 30602, U.S.A
| | - Tamara A. Dailey
- Biomedical and Health Sciences Institute, Paul D. Coverdell Center, University of Georgia, Athens, GA 30602, U.S.A
| | - Harry A. Dailey
- Biomedical and Health Sciences Institute, Paul D. Coverdell Center, University of Georgia, Athens, GA 30602, U.S.A
- To whom correspondence should be addressed (email )
| |
Collapse
|
34
|
Heldt D, Lawrence AD, Lindenmeyer M, Deery E, Heathcote P, Rigby SE, Warren MJ. Aerobic synthesis of vitamin B12: ring contraction and cobalt chelation. Biochem Soc Trans 2005; 33:815-9. [PMID: 16042605 DOI: 10.1042/bst0330815] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The aerobic biosynthetic pathway for vitamin B12 (cobalamin) biosynthesis is reviewed. Particular attention is focused on the ring contraction process, whereby an integral carbon atom of the tetrapyrrole-derived macrocycle is removed. Previous work had established that this chemically demanding step is facilitated by the action of a mono-oxygenase called CobG, which generates a hydroxy lactone intermediate. This mono-oxygenase contains both a non-haem iron and an Fe-S centre, but little information is known about its mechanism. Recent work has established that in bacteria such as Rhodobacter capsulatus, CobG is substituted by an isofunctional protein called CobZ. This protein has been shown to contain flavin, haem and Fe-S centres. A mechanism is proposed to explain the function of CobZ. Another interesting aspect of the aerobic cobalamin biosynthetic pathway is cobalt insertion, which displays some similarity to the process of magnesium chelation in chlorophyll synthesis. The genetic requirements of cobalt chelation and the subsequent reduction of the metal ion are discussed.
Collapse
Affiliation(s)
- D Heldt
- School of Biological Sciences, Queen Mary, University of London, Mile End Road, London E1 4NS, UK.
| | | | | | | | | | | | | |
Collapse
|
35
|
Frank S, Brindley AA, Deery E, Heathcote P, Lawrence AD, Leech HK, Pickersgill RW, Warren MJ. Anaerobic synthesis of vitamin B12: characterization of the early steps in the pathway. Biochem Soc Trans 2005; 33:811-4. [PMID: 16042604 DOI: 10.1042/bst0330811] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The anaerobic biosynthesis of vitamin B12 is slowly being unravelled. Recent work has shown that the first committed step along the anaerobic route involves the sirohydrochlorin (chelation of cobalt into factor II). The following enzyme in the pathway, CbiL, methylates cobalt-factor II to give cobalt-factor III. Recent progress on the molecular characterization of this enzyme has given a greater insight into its mode of action and specificity. Structural studies are being used to provide insights into how aspects of this highly complex biosynthetic pathway may have evolved. Between cobalt-factor III and cobyrinic acid, only one further intermediate has been identified. A combination of molecular genetics, recombinant DNA technology and bioorganic chemistry has led to some recent advances in assigning functions to the enzymes of the anaerobic pathway.
Collapse
Affiliation(s)
- S Frank
- School of Biological Sciences, Queen Mary, University of London, Mile End Road, London E1 4NS, UK.
| | | | | | | | | | | | | | | |
Collapse
|
36
|
Vévodová J, Graham RM, Raux E, Schubert HL, Roper DI, Brindley AA, Ian Scott A, Roessner CA, Stamford NPJ, Elizabeth Stroupe M, Getzoff ED, Warren MJ, Wilson KS. Structure/function studies on a S-adenosyl-L-methionine-dependent uroporphyrinogen III C methyltransferase (SUMT), a key regulatory enzyme of tetrapyrrole biosynthesis. J Mol Biol 2004; 344:419-33. [PMID: 15522295 DOI: 10.1016/j.jmb.2004.09.020] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2004] [Revised: 08/23/2004] [Accepted: 09/14/2004] [Indexed: 10/26/2022]
Abstract
The crystallographic structure of the Pseudomonas denitrificans S-adenosyl-L-methionine-dependent uroporphyrinogen III methyltransferase (SUMT), which is encoded by the cobA gene, has been solved by molecular replacement to 2.7A resolution. SUMT is a branchpoint enzyme that plays a key role in the biosynthesis of modified tetrapyrroles by controlling flux to compounds such as vitamin B(12) and sirohaem, and catalysing the transformation of uroporphyrinogen III into precorrin-2. The overall topology of the enzyme is similar to that of the SUMT module of sirohaem synthase (CysG) and the cobalt-precorrin-4 methyltransferase CbiF and, as with the latter structures, SUMT has the product S-adenosyl-L-homocysteine bound in the crystal. The roles of a number of residues within the SUMT structure are discussed with respect to their conservation either across the broader family of cobalamin biosynthetic methyltransferases or within the sub-group of SUMT members. The D47N, L49A, F106A, T130A, Y183A and M184A variants of SUMT were generated by mutagenesis of the cobA gene, and tested for SAM binding and enzymatic activity. Of these variants, only D47N and L49A bound the co-substrate S-adenosyl-L-methionine. Consequently, all the mutants were severely restricted in their capacity to synthesise precorrin-2, although both the D47N and L49A variants produced significant quantities of precorrin-1, the monomethylated derivative of uroporphyrinogen III. The activity of these variants is interpreted with respect to the structure of the enzyme.
Collapse
Affiliation(s)
- Jitka Vévodová
- Structural Biology Laboratory, Department of Chemistry, University of York, Heslington, York YO10 5YW, UK
| | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
37
|
Raux-Deery E, Leech HK, Nakrieko KA, McLean KJ, Munro AW, Heathcote P, Rigby SEJ, Smith AG, Warren MJ. Identification and characterization of the terminal enzyme of siroheme biosynthesis from Arabidopsis thaliana: a plastid-located sirohydrochlorin ferrochelatase containing a 2FE-2S center. J Biol Chem 2004; 280:4713-21. [PMID: 15545265 DOI: 10.1074/jbc.m411360200] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Higher plant sulfite and nitrite reductases contain siroheme as a prosthetic group. Siroheme is synthesized from the tetrapyrrole primogenitor uroporphyrinogen III in three steps involving methylation, oxidation, and ferrochelation reactions. In this paper we report on the Arabidopsis thaliana sirohydrochlorin ferrochelatase At-SirB. The complete precursor protein of 225 amino acids and shorter constructs in which the first 46 or 79 residues had been removed were shown to complement a defined Escherichia coli sirohydrochlorin ferrochelatase mutant. The mature form of the protein appeared to consist of only 150 amino acids, making it much smaller than previously characterized ferrochelatases. Green fluorescent protein tagging revealed that it is located in the chloroplast. The enzyme was easily produced in E. coli as a recombinant protein, and the isolated enzyme was found to have a specific activity of 48.5 nmol/min/mg. Significantly, the protein purified as a brown-colored solution with a UV-visible spectrum containing maxima at 415 and 455 nm, suggestive of an Fe-S center. EPR analysis of the recombinant protein produced a rhombic spectrum with G-values of 2.04, 1.94, and 1.90 and with temperature dependence consistent with a 2Fe-2S center. Redox titration demonstrated that the Fe-S center is highly unstable, with an apparent midpoint reduction potential of about -370 mV. This is the first Fe-S center to be reported in a higher plant ferrochelatase. The implications of the Fe-S center in an enzyme that is so closely associated with the metabolism of sulfur and iron are discussed.
Collapse
Affiliation(s)
- Evelyne Raux-Deery
- School of Biological Sciences, Queen Mary, University of London, Mile End Rd., London E1 4NS, United Kingdom
| | | | | | | | | | | | | | | | | |
Collapse
|