Figure 7.

nthiOppA_1A1B and nthiOppA₂ differentially bind heme and peptide substrates. Cartoon representations of individual nthiOppA domains, nthiOppA_1A1B (A) and nthiOppA₂ (B), are highlighted in salmon/wheat and cyan, respectively. C and D, single-cycle kinetic analysis of nthiOppA_1A1B (C) and nthiOppA₂ (D) heme binding. Each sensogram depicts representative data fit to a 1:1 two-state reaction model, shown in red and dashed black lines, respectively. The tryptophan fluorescence quenching of nthiOppA_1A1B (E) and nthiOppA₂ (F) upon P4^GIINTL binding is shown. Representative data shown are fit to a one-site binding model.