Fig 2.

Disulfide stress upon diamide treatment of E. coli cells grown in MOPS minimal medium. (A) The formation of disulfide bonds in the cytoplasm parallels the diamide concentration in the medium. The arrows in the growth curve represent the time points at which samples were taken to measure the diamide concentration in the medium (B) and PhoAΔ2-22 activity (C). (D) The Coomassie-stained protein gel and Western blot with alkaline phosphatase antibody show that the expression of PhoAΔ2-22 (arrow) is not significantly induced upon addition of diamide to the medium. The incubation times with diamide are indicated. The gain of activity can be attributed only to disulfide bond formation. Co, control.