1
|
Oehlmann NN, Schmidt FV, Herzog M, Goldman AL, Rebelein JG. The iron nitrogenase reduces carbon dioxide to formate and methane under physiological conditions: A route to feedstock chemicals. SCIENCE ADVANCES 2024; 10:eado7729. [PMID: 39141735 PMCID: PMC11323892 DOI: 10.1126/sciadv.ado7729] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/20/2024] [Accepted: 07/09/2024] [Indexed: 08/16/2024]
Abstract
Nitrogenases are the only known enzymes that reduce molecular nitrogen (N2) to ammonia. Recent findings have demonstrated that nitrogenases also reduce the greenhouse gas carbon dioxide (CO2), suggesting CO2 to be a competitor of N2. However, the impact of omnipresent CO2 on N2 fixation has not been investigated to date. Here, we study the competing reduction of CO2 and N2 by the two nitrogenases of Rhodobacter capsulatus, the molybdenum and the iron nitrogenase. The iron nitrogenase is almost threefold more efficient in CO2 reduction and profoundly less selective for N2 than the molybdenum isoform under mixtures of N2 and CO2. Correspondingly, the growth rate of diazotrophically grown R. capsulatus strains relying on the iron nitrogenase notably decreased after adding CO2. The in vivo CO2 activity of the iron nitrogenase facilitates the light-driven extracellular accumulation of formate and methane, one-carbon substrates for other microbes, and feedstock chemicals for a circular economy.
Collapse
Affiliation(s)
- Niels N. Oehlmann
- Research Group Microbial Metalloenzymes, Max Planck Institute for Terrestrial Microbiology, 35043 Marburg, Germany
| | - Frederik V. Schmidt
- Research Group Microbial Metalloenzymes, Max Planck Institute for Terrestrial Microbiology, 35043 Marburg, Germany
| | - Marcello Herzog
- Research Group Microbial Metalloenzymes, Max Planck Institute for Terrestrial Microbiology, 35043 Marburg, Germany
| | - Annelise L. Goldman
- Research Group Microbial Metalloenzymes, Max Planck Institute for Terrestrial Microbiology, 35043 Marburg, Germany
| | - Johannes G. Rebelein
- Research Group Microbial Metalloenzymes, Max Planck Institute for Terrestrial Microbiology, 35043 Marburg, Germany
- Center for Synthetic Microbiology (SYNMIKRO), Philipps University Marburg, 35043 Marburg, Germany
| |
Collapse
|
2
|
Addison H, Glatter T, K. A. Hochberg G, Rebelein JG. Two distinct ferredoxins are essential for nitrogen fixation by the iron nitrogenase in Rhodobacter capsulatus. mBio 2024; 15:e0331423. [PMID: 38377621 PMCID: PMC10936413 DOI: 10.1128/mbio.03314-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2023] [Accepted: 01/29/2024] [Indexed: 02/22/2024] Open
Abstract
Nitrogenases are the only enzymes able to fix gaseous nitrogen into bioavailable ammonia and hence are essential for sustaining life. Catalysis by nitrogenases requires both a large amount of ATP and electrons donated by strongly reducing ferredoxins or flavodoxins. Our knowledge about the mechanisms of electron transfer to nitrogenase enzymes is limited: The electron transport to the iron (Fe)-nitrogenase has hardly been investigated. Here, we characterized the electron transfer pathway to the Fe-nitrogenase in Rhodobacter capsulatus via proteome analyses, genetic deletions, complementation studies, and phylogenetics. Proteome analyses revealed an upregulation of four ferredoxins under nitrogen-fixing conditions reliant on the Fe-nitrogenase in a molybdenum nitrogenase knockout strain, compared to non-nitrogen-fixing conditions. Based on these findings, R. capsulatus strains with deletions of ferredoxin (fdx) and flavodoxin (fld, nifF) genes were constructed to investigate their roles in nitrogen fixation by the Fe-nitrogenase. R. capsulatus deletion strains were characterized by monitoring diazotrophic growth and Fe-nitrogenase activity in vivo. Only deletions of fdxC or fdxN resulted in slower growth and reduced Fe-nitrogenase activity, whereas the double deletion of both fdxC and fdxN abolished diazotrophic growth. Differences in the proteomes of ∆fdxC and ∆fdxN strains, in conjunction with differing plasmid complementation behaviors of fdxC and fdxN, indicate that the two Fds likely possess different roles and functions. These findings will guide future engineering of the electron transport systems to nitrogenase enzymes, with the aim of increased electron flux and product formation.IMPORTANCENitrogenases are essential for biological nitrogen fixation, converting atmospheric nitrogen gas to bioavailable ammonia. The production of ammonia by diazotrophic organisms, harboring nitrogenases, is essential for sustaining plant growth. Hence, there is a large scientific interest in understanding the cellular mechanisms for nitrogen fixation via nitrogenases. Nitrogenases rely on highly reduced electrons to power catalysis, although we lack knowledge as to which proteins shuttle the electrons to nitrogenases within cells. Here, we characterized the electron transport to the iron (Fe)-nitrogenase in the model diazotroph Rhodobacter capsulatus, showing that two distinct ferredoxins are very important for nitrogen fixation despite having different redox centers. In addition, our research expands upon the debate on whether ferredoxins have functional redundancy or perform distinct roles within cells. Here, we observe that both essential ferredoxins likely have distinct roles based on differential proteome shifts of deletion strains and different complementation behaviors.
Collapse
Affiliation(s)
- Holly Addison
- Microbial Metalloenzymes Research Group, Max Planck Institute for Terrestrial Microbiology, Marburg, Germany
| | - Timo Glatter
- Core Facility for Mass Spectrometry & Proteomics, Max Planck Institute for Terrestrial Microbiology, Marburg, Germany
| | - Georg K. A. Hochberg
- Evolutionary Biochemistry Research Group, Max Planck Institute for Terrestrial Microbiology, Marburg, Germany
- Center for Synthetic Microbiology (SYNMIKRO), Philipps University Marburg, Marburg, Germany
| | - Johannes G. Rebelein
- Microbial Metalloenzymes Research Group, Max Planck Institute for Terrestrial Microbiology, Marburg, Germany
- Center for Synthetic Microbiology (SYNMIKRO), Philipps University Marburg, Marburg, Germany
| |
Collapse
|
3
|
Schmidt FV, Schulz L, Zarzycki J, Prinz S, Oehlmann NN, Erb TJ, Rebelein JG. Structural insights into the iron nitrogenase complex. Nat Struct Mol Biol 2024; 31:150-158. [PMID: 38062208 PMCID: PMC10803253 DOI: 10.1038/s41594-023-01124-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2023] [Accepted: 09/12/2023] [Indexed: 01/24/2024]
Abstract
Nitrogenases are best known for catalyzing the reduction of dinitrogen to ammonia at a complex metallic cofactor. Recently, nitrogenases were shown to reduce carbon dioxide (CO2) and carbon monoxide to hydrocarbons, offering a pathway to recycle carbon waste into hydrocarbon products. Among the three nitrogenase isozymes, the iron nitrogenase has the highest wild-type activity for the reduction of CO2, but the molecular architecture facilitating these activities has remained unknown. Here, we report a 2.35-Å cryogenic electron microscopy structure of the ADP·AlF3-stabilized iron nitrogenase complex from Rhodobacter capsulatus, revealing an [Fe8S9C-(R)-homocitrate] cluster in the active site. The enzyme complex suggests that the iron nitrogenase G subunit is involved in cluster stabilization and substrate channeling and confers specificity between nitrogenase reductase and catalytic component proteins. Moreover, the structure highlights a different interface between the two catalytic halves of the iron and the molybdenum nitrogenase, potentially influencing the intrasubunit 'communication' and thus the nitrogenase mechanism.
Collapse
Affiliation(s)
- Frederik V Schmidt
- Microbial Metalloenzymes Research Group, Max Planck Institute for Terrestrial Microbiology, Marburg, Germany
| | - Luca Schulz
- Department of Biochemistry and Synthetic Metabolism, Max Planck Institute for Terrestrial Microbiology, Marburg, Germany
| | - Jan Zarzycki
- Department of Biochemistry and Synthetic Metabolism, Max Planck Institute for Terrestrial Microbiology, Marburg, Germany
| | - Simone Prinz
- Central Electron Microscopy Facility, Max Planck Institute of Biophysics, Frankfurt am Main, Germany
| | - Niels N Oehlmann
- Microbial Metalloenzymes Research Group, Max Planck Institute for Terrestrial Microbiology, Marburg, Germany
| | - Tobias J Erb
- Department of Biochemistry and Synthetic Metabolism, Max Planck Institute for Terrestrial Microbiology, Marburg, Germany
| | - Johannes G Rebelein
- Microbial Metalloenzymes Research Group, Max Planck Institute for Terrestrial Microbiology, Marburg, Germany.
| |
Collapse
|
4
|
Bierbaumer S, Nattermann M, Schulz L, Zschoche R, Erb TJ, Winkler CK, Tinzl M, Glueck SM. Enzymatic Conversion of CO 2: From Natural to Artificial Utilization. Chem Rev 2023; 123:5702-5754. [PMID: 36692850 PMCID: PMC10176493 DOI: 10.1021/acs.chemrev.2c00581] [Citation(s) in RCA: 28] [Impact Index Per Article: 28.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2022] [Indexed: 01/25/2023]
Abstract
Enzymatic carbon dioxide fixation is one of the most important metabolic reactions as it allows the capture of inorganic carbon from the atmosphere and its conversion into organic biomass. However, due to the often unfavorable thermodynamics and the difficulties associated with the utilization of CO2, a gaseous substrate that is found in comparatively low concentrations in the atmosphere, such reactions remain challenging for biotechnological applications. Nature has tackled these problems by evolution of dedicated CO2-fixing enzymes, i.e., carboxylases, and embedding them in complex metabolic pathways. Biotechnology employs such carboxylating and decarboxylating enzymes for the carboxylation of aromatic and aliphatic substrates either by embedding them into more complex reaction cascades or by shifting the reaction equilibrium via reaction engineering. This review aims to provide an overview of natural CO2-fixing enzymes and their mechanistic similarities. We also discuss biocatalytic applications of carboxylases and decarboxylases for the synthesis of valuable products and provide a separate summary of strategies to improve the efficiency of such processes. We briefly summarize natural CO2 fixation pathways, provide a roadmap for the design and implementation of artificial carbon fixation pathways, and highlight examples of biocatalytic cascades involving carboxylases. Additionally, we suggest that biochemical utilization of reduced CO2 derivates, such as formate or methanol, represents a suitable alternative to direct use of CO2 and provide several examples. Our discussion closes with a techno-economic perspective on enzymatic CO2 fixation and its potential to reduce CO2 emissions.
Collapse
Affiliation(s)
- Sarah Bierbaumer
- Institute
of Chemistry, University of Graz, NAWI Graz, Heinrichstraße 28, 8010 Graz, Austria
| | - Maren Nattermann
- Department
of Biochemistry and Synthetic Metabolism, Max Planck Institute for Terrestrial Microbiology, Karl-von-Frisch Straße 10, 35043 Marburg, Germany
| | - Luca Schulz
- Department
of Biochemistry and Synthetic Metabolism, Max Planck Institute for Terrestrial Microbiology, Karl-von-Frisch Straße 10, 35043 Marburg, Germany
| | | | - Tobias J. Erb
- Department
of Biochemistry and Synthetic Metabolism, Max Planck Institute for Terrestrial Microbiology, Karl-von-Frisch Straße 10, 35043 Marburg, Germany
| | - Christoph K. Winkler
- Institute
of Chemistry, University of Graz, NAWI Graz, Heinrichstraße 28, 8010 Graz, Austria
| | - Matthias Tinzl
- Department
of Biochemistry and Synthetic Metabolism, Max Planck Institute for Terrestrial Microbiology, Karl-von-Frisch Straße 10, 35043 Marburg, Germany
| | - Silvia M. Glueck
- Institute
of Chemistry, University of Graz, NAWI Graz, Heinrichstraße 28, 8010 Graz, Austria
| |
Collapse
|
5
|
Valentino M, Sirico DG, Memmolo P, Miccio L, Bianco V, Ferraro P. Digital holographic approaches to the detection and characterization of microplastics in water environments. APPLIED OPTICS 2023; 62:D104-D118. [PMID: 37132775 DOI: 10.1364/ao.478700] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Microplastic (MP) pollution is seriously threatening the environmental health of the world, which has accelerated the development of new identification and characterization methods. Digital holography (DH) is one of the emerging tools to detect MPs in a high-throughput flow. Here, we review advances in MP screening by DH. We examine the problem from both the hardware and software viewpoints. Automatic analysis based on smart DH processing is reported by highlighting the role played by artificial intelligence for classification and regression tasks. In this framework, the continuous development and availability in recent years of field-portable holographic flow cytometers for water monitoring also is discussed.
Collapse
|
6
|
Gee LB, Myers WK, Nack-Lehman PA, Scott AD, Yan L, George SJ, Dong W, Dapper CH, Newton WE, Cramer SP. Nitrogenase Chemistry at 10 Kelvin─Phototautomerization and Recombination of CO-Inhibited α-H195Q Enzyme. Inorg Chem 2022; 61:11509-11513. [PMID: 35856737 DOI: 10.1021/acs.inorgchem.2c00818] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
CO-bound forms of nitrogenase are N2-reduction inhibited and likely intermediates in Fischer-Tropsch chemistry. Visible-light photolysis at 7 K was used to interrogate all three known CO-related EPR-active forms as exhibited by the α-H195Q variant of Azotobacter vinelandii nitrogenase MoFe protein. The hi(5)-CO EPR signal converted to the hi-CO EPR signal, which reverted at 10 K. FT-IR monitoring revealed an exquisitely light-sensitive "Hi-2" species with bands at 1932 and 1866 cm-1 that yielded "Hi-1" with bands at 1969 and 1692 cm-1, which reverted to "Hi-2". The similarities of photochemical behavior and recombination kinetics showed, for the first time, that hi-CO EPR and "Hi-1" IR signals arise from one chemical species. hi(5)-CO EPR and "Hi-2" IR signals are from a second species, and lo-CO EPR and "Lo-2" IR signals, formed after prolonged illumination, are from a third species. Comparing FT-IR data with CO-inhibited MoFe-protein crystal structures allowed assignment of CO-bonding geometries in these species.
Collapse
Affiliation(s)
- Leland B Gee
- Department of Chemistry, University of California, Davis, California 95616, United States.,LCLS, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States
| | - William K Myers
- Department of Chemistry, University of Oxford, Oxford 3QR OX1, United Kingdom
| | - Patrick A Nack-Lehman
- Department of Chemistry, University of California, Davis, California 95616, United States
| | - Aubrey D Scott
- Department of Chemistry, University of California, Davis, California 95616, United States
| | - Lifen Yan
- Department of Chemistry, University of California, Davis, California 95616, United States
| | - Simon J George
- Department of Chemistry, University of California, Davis, California 95616, United States
| | - Weibing Dong
- Department of Chemistry, University of California, Davis, California 95616, United States
| | - Christie H Dapper
- Department of Biochemistry, Virginia Tech, Blacksburg, Virginia 24061, United States
| | - William E Newton
- Department of Biochemistry, Virginia Tech, Blacksburg, Virginia 24061, United States
| | - Stephen P Cramer
- Department of Chemistry, University of California, Davis, California 95616, United States.,SETI Institute, Mountain View, California 94043, United States
| |
Collapse
|