The vulnerability of radical SAM enzymes to oxidants and soft metals
Radical S-adenosylmethionine enzymes (RSEs) drive diverse biological processes by catalyzing chemically difficult reactions. Each of these enzymes uses a solvent-exposed [4Fe–4S] cluster to coordinate and cleave its SAM co-reactant. This cluster is destroyed during oxic handling, forcing investigato...
| Main Authors: | , |
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| Format: | Article |
| Language: | English |
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Elsevier
2022-11-01
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| Series: | Redox Biology |
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| Online Access: | http://www.sciencedirect.com/science/article/pii/S2213231722002671 |
| _version_ | 1811198489392054272 |
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| author | Sanjay Kumar Rohaun James A. Imlay |
| author_facet | Sanjay Kumar Rohaun James A. Imlay |
| author_sort | Sanjay Kumar Rohaun |
| collection | DOAJ |
| description | Radical S-adenosylmethionine enzymes (RSEs) drive diverse biological processes by catalyzing chemically difficult reactions. Each of these enzymes uses a solvent-exposed [4Fe–4S] cluster to coordinate and cleave its SAM co-reactant. This cluster is destroyed during oxic handling, forcing investigators to work with these enzymes under anoxic conditions. Analogous substrate-binding [4Fe–4S] clusters in dehydratases are similarly sensitive to oxygen in vitro; they are also extremely vulnerable to reactive oxygen species (ROS) in vitro and in vivo. These observations suggested that ROS might similarly poison RSEs. This conjecture received apparent support by the observation that when E. coli experiences hydrogen peroxide stress, it induces a cluster-free isozyme of the RSE HemN. In the present study, surprisingly, the purified RSEs viperin and HemN proved quite resistant to peroxide and superoxide in vitro. Furthermore, pathways that require RSEs remained active inside E. coli cells that were acutely stressed by hydrogen peroxide and superoxide. Viperin, but not HemN, was gradually poisoned by molecular oxygen in vitro, forming an apparent [3Fe–4S]+ form that was readily reactivated. The modest rate of damage, and the known ability of cells to repair [3Fe–4S]+ clusters, suggest why these RSEs remain functional inside fully aerated organisms. In contrast, copper(I) damaged HemN and viperin in vitro as readily as it did fumarase, a known target of copper toxicity inside E. coli. Excess intracellular copper also impaired RSE-dependent biosynthetic processes. These data indicate that RSEs may be targets of copper stress but not of reactive oxygen species. |
| first_indexed | 2024-04-12T01:32:37Z |
| format | Article |
| id | doaj.art-05f25b70174d4c669f3ec6bdfcfa2ead |
| institution | Directory Open Access Journal |
| issn | 2213-2317 |
| language | English |
| last_indexed | 2024-04-12T01:32:37Z |
| publishDate | 2022-11-01 |
| publisher | Elsevier |
| record_format | Article |
| series | Redox Biology |
| spelling | doaj.art-05f25b70174d4c669f3ec6bdfcfa2ead2022-12-22T03:53:27ZengElsevierRedox Biology2213-23172022-11-0157102495The vulnerability of radical SAM enzymes to oxidants and soft metalsSanjay Kumar Rohaun0James A. Imlay1Department of Microbiology, University of Illinois, Urbana, IL, 61801, USACorresponding author.; Department of Microbiology, University of Illinois, Urbana, IL, 61801, USARadical S-adenosylmethionine enzymes (RSEs) drive diverse biological processes by catalyzing chemically difficult reactions. Each of these enzymes uses a solvent-exposed [4Fe–4S] cluster to coordinate and cleave its SAM co-reactant. This cluster is destroyed during oxic handling, forcing investigators to work with these enzymes under anoxic conditions. Analogous substrate-binding [4Fe–4S] clusters in dehydratases are similarly sensitive to oxygen in vitro; they are also extremely vulnerable to reactive oxygen species (ROS) in vitro and in vivo. These observations suggested that ROS might similarly poison RSEs. This conjecture received apparent support by the observation that when E. coli experiences hydrogen peroxide stress, it induces a cluster-free isozyme of the RSE HemN. In the present study, surprisingly, the purified RSEs viperin and HemN proved quite resistant to peroxide and superoxide in vitro. Furthermore, pathways that require RSEs remained active inside E. coli cells that were acutely stressed by hydrogen peroxide and superoxide. Viperin, but not HemN, was gradually poisoned by molecular oxygen in vitro, forming an apparent [3Fe–4S]+ form that was readily reactivated. The modest rate of damage, and the known ability of cells to repair [3Fe–4S]+ clusters, suggest why these RSEs remain functional inside fully aerated organisms. In contrast, copper(I) damaged HemN and viperin in vitro as readily as it did fumarase, a known target of copper toxicity inside E. coli. Excess intracellular copper also impaired RSE-dependent biosynthetic processes. These data indicate that RSEs may be targets of copper stress but not of reactive oxygen species.http://www.sciencedirect.com/science/article/pii/S2213231722002671Reactive oxygen speciesCopperNitric oxideIron-sulfur clusters |
| spellingShingle | Sanjay Kumar Rohaun James A. Imlay The vulnerability of radical SAM enzymes to oxidants and soft metals Redox Biology Reactive oxygen species Copper Nitric oxide Iron-sulfur clusters |
| title | The vulnerability of radical SAM enzymes to oxidants and soft metals |
| title_full | The vulnerability of radical SAM enzymes to oxidants and soft metals |
| title_fullStr | The vulnerability of radical SAM enzymes to oxidants and soft metals |
| title_full_unstemmed | The vulnerability of radical SAM enzymes to oxidants and soft metals |
| title_short | The vulnerability of radical SAM enzymes to oxidants and soft metals |
| title_sort | vulnerability of radical sam enzymes to oxidants and soft metals |
| topic | Reactive oxygen species Copper Nitric oxide Iron-sulfur clusters |
| url | http://www.sciencedirect.com/science/article/pii/S2213231722002671 |
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