Accumulation of the prolipoprotein of the Escherichia coli outer membrane caused by benzyloxycarbonylalanine chloromethyl ketone.

Benzyloxycarbonylalanine chloromethyl ketone (Z-Ala-CH2Cl) was found to inhibit the processing of the prolipoprotein, a secretory precursor of the lipoprotein of the Escherichia coli outer membrane. The accumulation of the prolipoprotein in the presence of Z-Ala-CH2Cl was observed both in vivo and in vitro. Z-Ala-CH2Cl did not inhibit the processing of precursors of the other major outer membrane proteins. A preliminary experiment to identify the processing enzyme(s) of the prolipoprotein was carried out with use of Z-[3H]Ala-CH2Cl and revealed that two cytoplasmic membrane proteins with Mr = 78,000 and 46,000 were predominantly labeled.