DELETION OF THE PRC (TSP) GENE PROVIDES EVIDENCE FOR ADDITIONAL TAIL-SPECIFIC PROTEOLYTIC ACTIVITY IN ESCHERICHIA-COLI K-12

The Escherichia coli protease Pre (Tsp) exhibits specificity in vitro for proteins with nonpolar carboxyl termini. To determine whether Pre is responsible for the selective degradation in vivo of proteins with nonpolar carboxyl termini, we constructed a pre (tsp) deletion strain. Deletion of the pre gene did not prevent the rapid intracellular degr adation of a variant of the amino-terminal domain of lambda repressor with a nonpolar carboxyl terminus, even though this protein is a subst rate for Pre in vitro. Our results indicate that at least one addition al carboxy-terminal-specific proteolytic system must exist in E. coli.