Fig. 9. Inhibition of UmuD processing by DinI and LexA-S119A. (A and B) The in vitro reactions were performed as described in Materials and methods. Different amounts of DinI (A) or LexA-S119A (B) were added to the reaction mixtures to measure the inhibition of processing of UmuD (6 µM). The proteins were analyzed by 16.5% SDS–PAGE with a Tricine buffer system. (C) The densities of the UmuD and UmuD′ bands in the presence of poly(dT) (A and B) or M13 ssDNA (data not shown) were measured, and the relative amounts of UmuD′ against UmuD + UmuD′ were plotted against the amount of DinI or LexA-S119A added to the reaction.