Fig. 2.

Activity of E. coli QueF (assays with B. subtilis QueF gave qualitatively identical results). (A) UV continuous assays of NADPH consumption. Assays were performed in 100 mM Tris·HCl (pH 7.5)/100 μM preQ₀/100 μM NADPH and monitored at 340 nm. The concentrations of enzyme are the following: ○, no enzyme; •, 19 μg/ml; ⋄, 38 μg/ml; ▪, 95 μg/ml; □, 190 μg/ml. (B) HPLC chromatogram of synthetic preQ₁ (dashed) and preQ₀ (solid). (C) HPLC chromatograms of an E. coli QueF reaction (solid) and the reaction spiked with authentic preQ₁ (dashed).