Cleavage of the outer membrane protein OmpX by protealysin regulatesSerratia proteamaculansinvasion

Protealysin is a thermolysin-like protease ofSerratia proteamaculanscapable of specifically cleaving actin, which correlates with the invasive activity of these bacteria. Here, we show that inactivation of the protealysin gene does not inhibit invasion but, in contrast, leads to a twofold increase in theS. proteamaculansinvasive activity. By mass spectrometry, we identified the outer membrane protein OmpX as a substrate of protealysin. RecombinantE. colicarrying the OmpX gene truncated by 40 N-terminal residues or both the OmpX and protealysin genes, in contrast to the full-length OmpX, do not increase adhesion of these bacteria, indicating that the 40 N-terminal residues of OmpX are indispensable forS. proteamaculansinvasion. Our results show that both protealysin and its substrates can stimulateSerratiainvasion.