Characterization of a selenocysteine-ligated P450 compound I reveals direct link between electron donation and reactivity

Abstract

Strong electron-donation from the axial thiolate ligand of cytochrome P450 has been proposed to increase the reactivity of compound I with respect to C-H bond activation. However, it has proven difficult to test this hypothesis, and a direct link between reactivity and electron donation has yet to be established. To make this connection, we have prepared a selenolate-ligated cytochrome P450 compound I intermediate. This isoelectronic perturbation allows for direct comparisons with the wild-type enzyme. Selenium incorporation was achieved using a cysteine auxotrophic Escherichia coli strain. The intermediate was prepared with meta-chloroperbenzoic acid and characterized by UV-visible, Mössbauer and electron paramagnetic resonance spectroscopies. Measurements revealed increased asymmetry around the ferryl moiety, consistent with increased electron donation from the axial selenolate ligand. In line with this observation, we find that the selenolate-ligated compound I cleaves C-H bonds more rapidly than the wild-type intermediate.

Single-atom nanozymes

“…This indicates that the strong adsorption weakens the O─O bond and gives rise to a larger extent of O─O bond elongation. The weakening of the O─O bond can be ascribed to the filling of the antibonding * orbital of O 2 by electrons transferred via the electron push effect of axial-coordinated N in FeN 5 SA/CNF during adsorption (37). This behavior looks similar to that of the strong internal electron donor from axial thiolate ligand of cytochrome P450 (38,39).…”

Custom selenoprotein production enabled by laboratory evolution of recoded bacterial strains

“…In addition to enabling the incorporation of diselenide bonds as a protein engineering tool 41 , a reliable host for recombinant selenoprotein expression will find broad utility among the wider protein biology community. Replacing catalytic cysteine residues in enzymes with selenocysteine has enabled advances in mechanistic enzymology 42 , 43 , but progress has been hindered by inefficient protein expression in cysteine auxotrophs or by specialized protein ligation strategies 44 . In addition, these approaches have inherent limitations, requiring either the removal of cysteine residues or accepting indiscriminate selenocysteine incorporation, or a need for the truncated enzyme fragments to remain soluble.…”

Heteroatom Dopants Promote Two‐Electron O2 Reduction for Photocatalytic Production of H2O2 on Polymeric Carbon Nitride

“…In such a case, the electrons on the conjugated rings of S-doped CN can be donated to the antibonding p* orbital of adsorbed *O 2 (with À0.40 j e j) through the strong electron pushing effect between oxygen and carbon (1.87 , Figure S22c), which weakens the OÀO bond (1.29 ) (vs. free O 2 (1.23 )) and facilitates subsequent protonation in ORR kinetics. [43] The chemisorption of O 2 on the CN plane should be a prerequisite for highly selective ORR and the introduction of S dopants in the melon unit creates polarized active sites on which O 2 is preferably attracted. The large adsorption energy and close proximity of floating O 2 to the melon plane should facilitate the ratedetermining step of endoperoxide formation via the interaction of adsorbed *O 2 with H + and e À on the S dopant (*O 2 + H + + e À !*OOH).…”