Accumulation of glyceride-containing precursor of the outer membrane lipoprotein in the cytoplasmic membrane of Escherichia coli treated with globomycin

Abstract

The protein accumulated in the cell envelope of Escherichia coli treated with globomycin was identified as the precursor of the outer membrane lipoprotein. The prolipoprotein was almost exclusively localized in the cytoplasmic membrane. The prolipoprotein could be immunoprecipitated with antilipoprotein immunoglobulin and could be chased to the lipoprotein in both in vivo and in vitro. Globomycin inhibited the chase. The prolipoprotein contained glycerol and fatty acid residues, whereas no free sulfhydryl group was detected in it. From these results, it is concluded that the prolipoprotein possesses a glyceride which is covalently bound to the cysteine residue in the peptide as the lipoprotein does and that the removal of signal peptide takes place after the modification. The inhibition of bacterial growth with increasing concentrations of globomycin was accompanied by a gradual increase in the accumulation of the prolipoprotein. Furthermore, growth of the lipoprotein-negative mutant was highly resistant to globomycin. These results strongly indicate that the accumulation of the prolipoprotein in the cytoplasmic membrane causes the death of cells.