FIG. 1.

YscP regulates the substrate specificity of the Yersinia TTSS. (A) Surface localization of YscF in the yscP-null strain. The wild-type strain YPIII(pIB102) (WT) and the yscP-null mutant YPIII(pIB69) were grown at 37°C in BHI medium with or without calcium. The bacteria were harvested by centrifugation, and the pellets were sheared to release surface organelles from the bacterial surface. The bacteria were then centrifuged to separate cell pellet and sheared fractions. Two microliters of the pellet, diluted 1:10, and 5 μl of undiluted supernatant were separated on SDS-PAGE gels, and Western blots were performed by using an anti-YscF antiserum. (B) Yop secretion by the yscP-null strain. Bacteria were grown at 37°C in BHI medium without calcium to induce secretion. Bacteria were centrifuged to separate cell pellet and supernatant fractions. Equal amounts of supernatant fractions were separated by SDS-PAGE and stained with Coomassie brilliant blue. The yscP-null strain was transcomplemented by pPE34, which expresses YscP under the control of an arabinose-inducible promoter.