Direct Detection of the α-Carbon Radical Intermediate Formed by OspD: Mechanistic Insights into Radical S-Adenosyl-l-methionine Peptide Epimerization.

ABSTRACT: OspD is a radical S-adenosyl-l-methionine (SAM) peptide epimerase that converts an isoleucine (Ile) and valine (Val) of the OspA substrate to d-amino acids during biosynthesis of the ribosomally synthesized and post-translationally modified peptide (RiPP) natural product landornamide A. OspD is proposed to carry out this reaction via α-carbon (Cα) H-atom abstraction to form a peptidyl Cα radical that is stereospecifically quenched by hydrogen atom transfer (HAT) from a conserved cysteine (Cys). Here we use site-directed mutagenesis, freeze-quench trapping, isotopic labeling, and electron paramagnetic resonance (EPR) spectroscopy to provide new insights into the OspD catalytic mechanism including the direct observation of the substrate peptide Cα radical intermediate. The putative qu

SUBMITTER: Walls WG 

PROVIDER: S-EPMC11302384 | biostudies-literature | 2024 Feb

REPOSITORIES: biostudies-literature