The Key Intermediate in Radical <i>S</i>-Adenosyl-methionine Catalysis: Caught in the Act

Rittle, Jonathan

doi:10.1021/acscentsci.9b01024

Cited by 2 publications

(2 citation statements)

References 8 publications

(20 reference statements)

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“…Here, we report that the removal of the dangler Fe atom in HydG leads to the enhanced accumulation of 4-OB • , which provides new opportunities to address fundamental questions in HydG rSAM chemistry. 34 With enhanced signal intensity, we can now perform a detailed EPR and electron nuclear double resonance (ENDOR) characterization of this 4-OB • species, including the determination of its g-values and 1 H and 13 C hyperfine parameters. In addition, although previous work has established the electronic structure of 4-OB • as having major spin density on the benzyl carbon, the question remains regarding the protonation state of the phenolic hydroxyl group.…”

Section: ■ Introductionmentioning

confidence: 78%

Section: Introductionmentioning

confidence: 99%

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Accumulation and Pulse Electron Paramagnetic Resonance Spectroscopic Investigation of the 4-Oxidobenzyl Radical Generated in the RadicalS-Adenosyl-l-methionine Enzyme HydG

et al. 2022

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The radical S-adenosyl-L-methionine (SAM) enzyme HydG cleaves tyrosine to generate CO and CN − ligands of the [FeFe] hydrogenase H-cluster, accompanied by the formation of a 4-oxidobenzyl radical (4-OB • ), which is the precursor to the HydG p-cresol byproduct. Native HydG only generates a small amount of 4-OB • , limiting detailed electron paramagnetic resonance (EPR) spectral characterization beyond our initial EPR lineshape study employing various tyrosine isotopologues. Here, we show that the concentration of trapped 4-OB • is significantly increased in reactions using HydG variants, in which the "dangler Fe" to which CO and CN − bind is missing or substituted by a redox-inert Zn 2+ ion. This allows for the detailed characterization of 4-OB • using high-field EPR and electron nuclear double resonance spectroscopy to extract its g-values and 1 H/ 13 C hyperfine couplings. These results are compared to density functional theory-predicted values of several 4-OB • models with different sizes and protonation states, with a best fit to the deprotonated radical anion configuration of 4-OB • . Overall, our results depict a clearer electronic structure of the transient 4-OB • radical and provide new insights into the radical SAM chemistry of HydG.

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Section: ■ Introductionmentioning

confidence: 78%

Section: Introductionmentioning

confidence: 99%