Figure 8.
Proposed model of the postsecretional activation cascade of the three proteases in P. aeruginosa. In the cytoplasm, the prepro-forms of the proteases are expressed under transcriptional control of QS, and their SPs are removed during translocation over the cytoplasmic membrane. In the extracellular space, the pro-form of LasB is first processed to its mature active form by unknown QS-dependent factors. The activated LasB, in turn, activates PIV by degrading PIVpp. In the case of PIV, cleavage of PP occurs, even in the QS mutant. PIV relieved from inhibition by PP processes pro-LasA into mature and active forms. LasB also plays an auxiliary role in activation of LasA.