IspH inhibition by barbiturate analogs. A,B. Dose-response curves for EcIspH inhibition. C, Computational docking structure of 9 binding to oxidized AaIspH. View from electron transfer side. D, View from substrate binding side. E, Side view. F, Proposed binding of the barbiturate enolate group in 9 to the unique, 4th Fe in the 4Fe-4S cluster in oxidized AaIspH. G, 9 GHz EPR spectra of PaIspH. Oxidized protein (top, orange); dithionite reduce (red); dithionite reduced plus 5 eq. 9 (green); dithionote reduced plus 9 eq. 9 (blue).