Figure 5.

Substitutions of interface residues abolish dATP-induced inhibition of E. coli class Ia RNR. Active conditions (black) contain 3 mm ATP. Inactive conditions (white) contain 175 μm dATP. Each experiment was performed in triplicate. The data in the left and right panels were collected on different days and reflect normal variation in the assay. RNR activity is defined as nanomoles of NADPH consumed in the RNR/TR/TRR-coupled assay, per min per mg of α₂ after subtraction for basal oxidation by TR/TRR. Typical reported WT enzyme activities are 2000–2500 nmol min⁻¹ mg⁻¹ (63).