Fig. 2. Characteristics of PqsL photoreactivity.

a PqsL photoreduction measured over several cycles of illumination (shaded intervals). The reaction of 10 µM PqsL was monitored by O₂ consumption, 1.25 mM NADPH was used as electron donor (one representative experiment shown). b Apparent velocity as a function of the wavelength of the illuminating light (black dots) together with the UV/Vis spectra of PqsL (orange, solid line) and NADH (orange, dashed line). c NAD⁺ formation from NADH oxidation by PqsL after 1 min (light green), 5 min (petrol blue) and 10 min (black) of illumination, as monitored by HPLC (one representative experiment). d Kinetics of light-induced oxygen consumption by PqsL supplemented with NADPH (blue circles), NADH (violet circles), NADPH + 2-ABA (green squares) and NADH + 2-ABA (ocher squares) or free FAD + NADPH (orange triangles). Rates of the PqsL reactions were corrected for the contribution of residual free FAD (calculated from K_D of the PqsL–FAD complex) and FAD photodegradation. Dashed lines/open circles show the rates of FAD-saturated PqsL prior to any corrections (i.e. rates as measured, normalized to FAD content). Line fits were calculated according to a Michaelis-Menten model. Parameters are provided in Supplementary Table 1. Experimental data on photoreduction of PqsL and free FAD with various alternative electron donors are provided in Supplementary Figs. 2 and 3. Error bars indicate SD of three identical measurements (panels b, d).