The αlytic protease pro-region does not require a physical linkage to activate the protease domain in vivo

Abstract

α-LYTlC protease, an extracellular serine protease of Lysobacter enzymogenes 495 , is synthesized as a pre-pro-protein¹. Previously it has been shown that when expressed in Escherichia coli, the protein is autocatalytically processed in the periplasmic space, and that the functional protease domain accumulates extracel-lularly². Engineered proteins lacking the 166 amino-acid pro-region were enzymatically inactive and remained cell-associated². By independently expressing the pro- and protease domains in vivo, evidence is provided here that direct covalent linkage is not required for production of active protease. We postulate that the pro-region acts as a template to promote the folding of the protease domain into an active configuration. Our results, combined with recent experiments on the evolutionarily unrelated subtilisin E (ref. 3), suggest that the ability of the pro-region of these bacterial proteases to facilitate folding of their protease domains is not a curiosity of a single system, but may reflect a general property of extracellular bacterial serine proteases.