Fig. 4.

Tightly bound dAMP associated with NrdE enhances inhibition of the B. subtilis Ib RNR by dATP. Spectrophotometric assays (500 μL) were conducted at 37 °C using 1-mM CDP, the indicated concentrations of dATP, the endogenous reducing system (40-μM TrxA, 0.4-μM TrxB, 0.2-mM NADPH), a 1:1 ratio of Mn(III)₂–Y• NrdF (0.9 Y•/β₂) and either apo-NrdE (black squares, 0.05 dAMP/α) or holo-NrdE (red squares, 1.2 dAMP/α). Each data point is the average of two replicates, and in most cases the error bars (±1 SD) are smaller than the marker.