A Peroxodiiron(III/III) Intermediate Mediating Both N-Hydroxylation Steps in Biosynthesis of the N-Nitrosourea Pharmacophore of Streptozotocin by the Multi-domain Metalloenzyme SznF
| Autor: | Grace E. Kenney, Molly J. McBride, Tai L. Ng, Bo Zhang, J. Martin Bollinger, Anne Marie Crooke, Christina Tysoe, Carsten Krebs, Debangsu Sil, Emily P. Balskus, Amie K. Boal |
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| Rok vydání: | 2020 |
| Předmět: |
Oxidase test
biology Chemistry Stereochemistry General Chemistry Quadrupole splitting 010402 general chemistry 01 natural sciences Biochemistry Catalysis Cofactor 0104 chemical sciences Hydroxylation chemistry.chemical_compound Colloid and Surface Chemistry Biosynthesis biology.protein Moiety Molecule Pharmacophore |
| Zdroj: | Journal of the American Chemical Society. 142:11818-11828 |
| ISSN: | 1520-5126 0002-7863 |
| Popis: | The alkylating warhead of the pancreatic cancer drug streptozotocin (SZN) contains an N-nitrosourea moiety constructed from Nω-methyl-l-arginine (l-NMA) by the multi-domain metalloenzyme SznF. The enzyme's central heme-oxygenase-like (HO-like) domain sequentially hydroxylates Nδ and Nω' of l-NMA. Its C-terminal cupin domain then rearranges the triply modified arginine to Nδ-hydroxy-Nω-methyl-Nω-nitroso-l-citrulline, the proposed donor of the functional pharmacophore. Here we show that the HO-like domain of SznF can bind Fe(II) and use it to capture O2, forming a peroxo-Fe2(III/III) intermediate. This intermediate has absorption- and Mossbauer-spectroscopic features similar to those of complexes previously trapped in f erritin-like d iiron o xidases and oxygenases (FDOs) and, more recently, the HO-like fatty acid oxidase UndA. The SznF peroxo-Fe2(III/III) complex is an intermediate in both hydroxylation steps, as shown by the concentration-dependent acceleration of its decay upon exposure to either l-NMA or Nδ-hydroxy-Nω-methyl-l-Arg (l-HMA). The Fe2(III/III) cluster produced upon decay of the intermediate has a small Mossbauer quadrupole splitting parameter, implying that, unlike the corresponding product states of many FDOs, it lacks an oxo-bridge. The subsequent decomposition of the product cluster to one or more paramagnetic Fe(III) species over several hours explains why SznF was previously purified and crystallographically characterized without its cofactor. Programmed instability of the oxidized form of the cofactor appears to be a unifying characteristic of the emerging superfamily of H O-like d iiron o xidases and oxygenases (HDOs). |
| Databáze: | OpenAIRE |
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