Nonheme iron-thiolate complexes as structural models of sulfoxide synthase active sites.

作者: Danushka M. Ekanayake , Anne A. Fischer , Maya E. Elwood , Alexandra M. Guzek , Sergey V. Lindeman

DOI: 10.1039/D0DT03403G

关键词: CrystallographyElectron paramagnetic resonanceImidazoleTrigonal bipyramidal molecular geometryActive siteLigandChelationDenticitySulfoxideChemistry

摘要: Two mononuclear iron(ii)-thiolate complexes have been prepared that represent structural models of the nonheme iron enzymes EgtB and OvoA, which catalyze O2-dependent formation carbon-sulfur bonds in biosynthesis thiohistidine compounds. The series Fe(ii) reported here feature tripodal N4 chelates (LA LB) contain both pyridyl imidazolyl donors = (1H-imidazol-4-yl)-N,N-bis((pyridin-2-yl)methyl)methanamine; LB N,N-bis((1-methylimidazol-2-yl)methyl)-2-pyridylmethylamine). Further coordination with monodentate aromatic or aliphatic thiolate ligands yielded five-coordinate, high-spin [FeII(LA)(SMes)]BPh4 (1) [FeII(LB)(SCy)]BPh4 (2), where SMes 2,4,6-trimethylthiophenolate SCy cyclohexanethiolate. X-ray crystal structures revealed 1 2 possess trigonal bipyramidal geometries formed by N4S ligand set. In each case, is positioned cis to an imidazole donor, replicating arrangement Cys- His-based substrates active site EgtB. geometric electronic were analyzed UV-vis absorption Mossbauer spectroscopies tandem density functional theory (DFT) calculations. Exposure nitric oxide (NO) six-coordinate FeNO adducts characterized infrared electron paramagnetic resonance (EPR) spectroscopies, confirming these are capable binding diatomic molecules. Reaction O2 causes oxidation disulfide products. implications results for development OvoA discussed.

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