Correction to “Terminal Hydride Complex of High-Spin Mn”

Journal of the American Chemical Society · 2024-09-18 · 1 citations

Correction to “Terminal Hydride Complex of High-Spin Mn”

Initial Steps in Methanobactin Biosynthesis: Substrate Binding by the Mixed-Valent Diiron Enzyme MbnBC

Biochemistry · 2024-04-08 · 10 citations

The MbnBC enzyme complex converts cysteine residues in a peptide substrate, MbnA, to oxazolone/thioamide groups during the biosynthesis of copper chelator methanobactin (Mbn). MbnBC belongs to the mixed-valent diiron oxygenase (MVDO) family, of which members use an Fe(II)Fe(III) cofactor to react with dioxygen for substrate modification. Several crystal structures of the inactive Fe(III)Fe(III) form of MbnBC alone and in complex with MbnA have been reported, but a mechanistic understanding requires determination of the oxidation states of the crystallographically observed Fe ions in the catalytically active Fe(II)Fe(III) state, along with the site of MbnA binding. Here, we have used electron nuclear double resonance (ENDOR) spectroscopy to determine such structural and electronic properties of the active site, in particular, the mode of substrate binding to the MV state, information not accessible by X-ray crystallography alone. The oxidation states of the two Fe ions were determined by 15N ENDOR analysis. The presence and locations of both bridging and terminal exogenous solvent ligands were determined using 1H and 2H ENDOR. In addition, 2H ENDOR using an isotopically labeled MbnA substrate indicates that MbnA binds to the Fe(III) ion of the cluster via the sulfur atom of its N-terminal modifiable cysteine residue, with displacement of a coordinated solvent ligand as shown by complementary 1H ENDOR. These results, which underscore the utility of ENDOR in studying MVDOs, provide a molecular picture of the initial steps in Mbn biosynthesis.

The Challenges and Opportunities of High-Spin Mn(II) EPR and ENDOR

Applied Magnetic Resonance · 2024-07-22 · 1 citations

Terminal Hydride Complex of High-Spin Mn

Journal of the American Chemical Society · 2024-06-28 · 5 citations

The iron–molybdenum cofactor of nitrogenase (FeMoco) catalyzes fixation of N2 via Fe hydride intermediates. Our understanding of these species has relied heavily on the characterization of well-defined 3d metal hydride complexes, which serve as putative spectroscopic models. Although the Fe ions in FeMoco, a weak-field cluster, are expected to adopt locally high-spin Fe2+/3+ configurations, synthetically accessible hydride complexes featuring d5 or d6 electron counts are almost exclusively low-spin. We report herein the isolation of a terminal hydride complex of four-coordinate, high-spin (d5; S = 5/2) Mn2+. Electron paramagnetic resonance and electron–nuclear double resonance studies reveal an unusually large degree of spin density on the hydrido ligand. In light of the isoelectronic relationship between Mn2+ and Fe3+, our results are expected to inform our understanding of the valence electronic structures of reactive hydride intermediates derived from FeMoco.

¹³C Electron Nuclear Double Resonance Spectroscopy-Guided Molecular Dynamics Computations Reveal the Structure of the Enzyme–Substrate Complex of an Active, <i>N</i>-Linked Glycosylated Lipoxygenase

Biochemistry · 2023 · 9 citations

• Chemistry
• Stereochemistry
• Crystallography

LOX inhibitors, and highlight the robustness of the ENDOR-guided MD approach to describe LOX-substrate structures.

Temporal and anatomic relationship between superficial and deep vein thromboses in hospitalized children

Thrombosis Research · 2021-01-26 · 1 citations

Coordination of the Copper Centers in Particulate Methane Monooxygenase: Comparison between Methanotrophs and Characterization of the Cu_CSite by EPR and ENDOR Spectroscopies

Journal of the American Chemical Society · 2021 · 45 citations

• Chemistry
• Inorganic chemistry
• Organic chemistry

is the likely site of biological methane oxidation by pMMO, a conclusion that will serve as a foundation for proposals regarding the mechanism of this reaction.

A New Reaction for Improved Calibration of EPR Rapid-Freeze Quench Times: Kinetics of Ethylene Diamine Tetraacetate (EDTA) Transfer from Calcium(II) to Copper(II)

Applied Magnetic Resonance · 2021-11-20 · 1 citations

The Soybean Lipoxygenase–Substrate Complex: Correlation between the Properties of Tunneling-Ready States and ENDOR-Detected Structures of Ground States

Biochemistry · 2020 · 31 citations

• Chemistry
• Crystallography
• Stereochemistry

provides a "ruler" for the DAD within the TRS. ENDOR measurements further corroborate the previous identification of a dynamical network coupling the buried active site of SLO to the surface. This study shows that subtle imperfections within the initial ground-state structures of E-S complexes are accompanied by compromised geometries at the TRS.

Composition and Structure of the Inorganic Core of Relaxed Intermediate <b>X</b>(Y122F) of <i>Escherichia coli</i> Ribonucleotide Reductase

Journal of the American Chemical Society · 2015-12-04 · 24 citations

Activation of the diferrous center of the β2 (R2) subunit of the class 1a Escherichia coli ribonucleotide reductases by reaction with O2 followed by one-electron reduction yields a spin-coupled, paramagnetic Fe(III)/Fe(IV) intermediate, denoted X, whose identity has been sought by multiple investigators for over a quarter of a century. To determine the composition and structure of X, the present study has applied (57)Fe, (14,15)N, (17)O, and (1)H electron nuclear double resonance (ENDOR) measurements combined with quantitative measurements of (17)O and (1)H electron paramagnetic resonance line-broadening studies to wild-type X, which is very short-lived, and to X prepared with the Y122F mutant, which has a lifetime of many seconds. Previous studies have established that over several seconds the as-formed X(Y122F) relaxes to an equilibrium structure. The present study focuses on the relaxed structure. It establishes that the inorganic core of relaxed X has the composition [(OH(-))Fe(III)-O-Fe(IV)]: there is no second inorganic oxygenic bridge, neither oxo nor hydroxo. Geometric analysis of the (14)N ENDOR data, together with recent extended X-ray absorption fine structure measurements of the Fe-Fe distance (Dassama, L. M.; et al. J. Am. Chem. Soc. 2013, 135, 16758), supports the view that X contains a "diamond-core" Fe(III)/Fe(IV) center, with the irons bridged by two ligands. One bridging ligand is the oxo bridge (OBr) derived from O2 gas. Given the absence of a second inorganic oxygenic bridge, the second bridging ligand must be protein derived, and is most plausibly assigned as a carboxyl oxygen from E238.