FIG. 2.

SDS-PAGE analysis of whole-cell proteins from Y. pestis strains grown in PMH in the presence (+) or absence (−) of FeCl₃ (10 μM) or Ybt. Ybt was added since previous studies showed induction of Ybt protein expression when the siderophore was added to Ybt biosynthetic mutants (2, 22). Cultures from Y. pestis KIM6+ (lanes 1 to 3), KIM6-2071 (ΔybtU2071; lanes 4 to 6), KIM6-2046.3 (Δirp2-2046.3; lanes 7 to 9), KIM6-2072 (ΔybtT2072; lanes 10 to 12), and KIM6-2070.1 (ybtS::kan2070.1; lanes 13 to 15) were incubated with ³⁵S-labeled amino acids for 1 h. Total cellular proteins were separated on a 7.5% polyacrylamide gel and visualized by autoradiography. Arrows, iron-regulated proteins HMWP1 (240 kDa), HMWP2 (190 kDa), Psn (68 kDa), and YbtE (56 kDa) and the truncated irp2 gene product (ΔHMWP2) expressed by the Y. pestis in-frame deletion mutant KIM6-2046.3 (Δirp2-2046.3).