Time-Resolved Investigations of Heterobimetallic Cofactor Assembly in R2lox Reveal Distinct Mn/Fe Intermediates.

The assembly mechanism of the Mn/Fe ligand-binding oxidases (R2lox), a family of proteins that are homologous to the nonheme diiron carboxylate enzymes, has been investigated using time-resolved techniques. Multiple heterobimetallic intermediates that exhibit unique spectral features, including visible absorption bands and exceptionally broad electron paramagnetic resonance signatures, are observed through optical and magnetic resonance spectroscopies. On the basis of comparison to known diiron species and model compounds, the spectra have been attributed to (μ-peroxo)-Mn/Fe and high-valent Mn/Fe species.