Demonstration of a cell-associated, inactive precursor of an exocellular protease produced by Pseudomonas aeruginosa

Abstract

The enzymatically active form of protease 1, the major exocellular protein produced by P. aeruginosa strain 34362, existed exclusively exocellularly with no significant cell-associated activity. The presence of a cell-associated, enzymatically inactive protein which is serologically cross-reactive with, and convertible to, active enzyme was demonstrated. One method of conversion of precursor to active enzyme is via limited proteolysis. Two assay systems for precursor were developed, one a radioimmune assay and the other a proteolytic activation procedure. Localization studies suggest that the cell-associated precursor resides primarily in the envelope (periplasmic) fraction, and that the association while more tenacious than classical periplasmic enzymes is still an ionic rather than a covalent one. Kinetics of production studies showed the precursor to be synthesized early in the growth cycle and to accumulate prior to the rapid release of the active enzyme. MW studies showed only slight changes produced upon activation.