Prolipoprotein signal peptidase in Escherichia coli is distinct from the M13 procoat protein signal peptidase.

We have previously reported a signal peptidase activity in Escherichia coli cell envelope which processes prolipoprotein modified with glyceride (Tokunaga, M., Tokunaga, H., and Wu, H. C. (1982) Proc. Natl. Acad. Sci. U. S. A. 79, 2255-2259). To ascertain whether the processing enzyme for prolipoprotein is distinct from the signal peptidase for M13 procoat protein purified by Zwizinski and Wickner (Zwizinski, C., and Wickner, W. (1980) J. Biol. Chem. 255, 7973-7977), we have used antibody against purified procoat protein signal peptidase to study the processings of prolipoprotein and M13 procoat protein in vitro. the signal peptidase for modified prolipoprotein remained fully active in solubilized membrane preparations which had been treated with antibody against purified procoat protein signal peptidase whereas the activity towards procoat protein was completely abolished by immunoadsorption. Furthermore, both unmodified and glyceride-modified prolipoprotein were not cleaved by the highly purified signal peptidase preparation provided by Wickner. These data clearly indicate that prolipoprotein signal peptidase is distinct from the M13 procoat protein signal peptidase.