Figure 4. In vivo dissociation and secretion of YscU_CC in different Yersinia strains.

Calcium dependent regulation of Yop and YscU_CC secretion in wild-type Y. pseudotuberculosis, in a ΔyscC mutant and ΔyscN mutant strain without and with in trans complementation of YscU_CC. Bacteria transformed with empty pBADmycHis B (pBAD), or pBAD with one additional yscU_CC copy (pBAD(YscU_CC)), were grown for 2 h at 26°C and 3 h at 37°C in calcium depleted (−) or calcium supplemented (+) medium. The expression of yscU_CC was induced by addition of arabinose. Yop secretion is coupled to the secretion of YscU_CC in all analysed Yersinia strains and required a functional T3SS. Secreted Yops visualized on Coomassie stained PAGE gels; YscU_CC visualized on immunoblots with anti-YscU_CC peptide antibodies. “pellet” indicates intracellular proteins; “supernatant” denotes secreted proteins. The YopJ protein (black box) was subjected to densitometric analysis for quantification of secretion levels (see Table 2).