FIG. 4.
SDS-PAGE analysis of whole-cell proteins from Y. pestis strains grown in iron-deficient PMH2. Cultures from Y. pestis KIM6+ (lane 1), KIM6-2046.1 (irp2::kan2046.1) (lane 2), KIM6-2085+ (ΔybtD2085) (lane 3), and KIM6-2085(pYBTD4)+ (ΔybtD2085/ybtD+) (lane 4) were incubated with 35S-labeled amino acids for 1 h. To demonstrate the effect of exogenous siderophore on expression of proteins by KIM6-2085+ cells, KIM6+ culture supernatant containing Ybt siderophore (lane 5) or KIM6-2046.1 culture supernatant (lane 6) was added 1:1 at the same time as 35S-labeled amino acids. Total cellular proteins were separated on a 9% polyacrylamide gel and visualized by autoradiography. Sizes of molecular mass markers (in kilodaltons) are indicated. Arrows point to the iron-regulated proteins HMWP1 (240 kDa), HMWP2 (190 kDa), and Psn (68 kDa).