Expression of the Serratia marcescens lipoproteins gene in Escherichia coli

The lipoprotein gene (lpp) of Serratia marcescens was cloned in a lambda phage vector (K. Nakamura and M. Inouye, Proc. Natl. Acad. Sci. U.S.A. 77: 1369-1373, 1980). This lpp gene was recloned in plasmid vectors pBR322 and pSC101. When a lipoprotein-deficient (lpp) mutant of Escherichia coli was transformed with pBR322 carrying the S. marcescens lpp gene, cells became nonleaky for ribonuclease, resistant to ethylenediaminetetraacetic acid, and sensitive to globomycin. The lipoprotein was found exclusively in the outer membrane fraction. These results indicate that the S. marcescens lipoprotein was normally secreted across the cytoplasmic membrane, modified, and assembled in the E. coli outer membrane. The amount of the free-form lipoprotein produced in this system was three times higher than that produced in lpp + C. coli cells, whereas there was no difference in the amount of the bound-form lipoprotein. On the other hand, lpp E. coli cells which harbored pSC101 carrying the S. marcescens lpp gene produced only one-third of the free-form lipoprotein produced in lpp E. coli cells which harbored pSC101 carrying the E. coli lpp gene. One of the major factors causing this difference in efficiency of gene expression between the lpp genes of S. marcescens and E. coli appears to be a deletion mutation at the transcription termination region found in the cloned S. marcescens lpp gene. The functional half-life of the S. marcescens lpp messenger ribonucleic acid in E. coli was found to be found half that of the E. coli lpp messenger ribonucleic acid.