Transcriptional regulation of the Yts1 type II secretion system of Yersinia enterocolitica and identification of secretion substrates.

Type II secretion systems (T2SSs) mediate the transport of proteins through the bacterial outer membrane. Although widespread in gamma-proteobacteria, they have so far not been characterized in the human pathogen Yersinia enterocolitica. We describe here genetic linkage of the Yts1 and Yts2 T2SSs with a transcriptional regulator in the highly pathogenic Y. enterocolitica biotype 1B. While the Yts2-associated PypC regulator activates the Yts2 operon, the PclR regulator does not induce transcription of its cognate Yts1 operon. Instead, Yts1 and pclR are activated by the addition of MgCl(2) to the growth medium at 17 degrees C and 26 degrees C, but not at 37 degrees C. We identified three proteins, ChiY, EngY (YE2830) and YE3650, that are secreted depending on a functional Yts1 T2SS in response to MgCl(2) at low temperature. While the activation of chiY by MgCl(2) depends on pclR, PclR overproduction is not sufficient for chiY transcription in an Escherichia coli background, demonstrating the need for additional Y. enterocolitica-specific factors. As ChiY and EngY both bind to chitin, and YE3650 shows motifs conserved in oligosaccharide-binding enzymes, all secreted proteins might be important for polysaccharide interaction/degradation during infection or in the environment.