Figure 2.

Time-dependent formation of the radical species observed during turnover of RlmN_C118S→RCN (blue diamonds) and Cfr_C105A→RCN (red circles). Time dependence of radical formation was fitted using an A → B kinetic model, affording a rate constant of k = 1.4 min^–1 for RlmN_C118S→RCN (solid blue line) and k = 0.61 min^–1 for Cfr_C105A→RCN (solid red line). For comparison, the time dependence of the radical formed by wt Cfr during C8 methylation is shown as a dashed black line (concentrations were normalized to the maximum concentration of the RlmN-generated radical). Concentrations were estimated using the EPR signal of flavodoxin semiquinone (37.2 μM) as a standard. Corresponding EPR spectra are presented in the Supporting Information in Figure S2.