Escherichia coli signal peptides direct inefficient secretion of an outer membrane protein (OmpA) and periplasmic proteins (maltose-binding protein, ribose-binding protein, and alkaline phosphatase) in Bacillus subtilis.
Signal peptides of gram-positive exoproteins generally carry a higher net positive charge at their amino termini (N regions) and have longer hydrophobic cores (h regions) and carboxy termini (C regions) than do signal peptides of Escherichia coli envelope proteins. To determine if these differences are functionally significant, the ability of Bacillus subtilis to secrete four different E. coli envelope proteins was tested. A pulse-chase analysis demonstrated that the periplasmic maltose-binding protein (MBP), ribose-binding protein (RBP), alkaline phosphatase (PhoA), and outer membrane protein OmpA were only inefficiently secreted. Inefficient secretion could be ascribed largely to properties of the homologous signal peptides, since replacing them with the B. amyloliquefaciens alkaline protease signal peptide resulted in significant increases in both the rate and extent of export. The relative efficiency with which the native precursors were secreted (OmpA >> RBP > MBP > PhoA) was most closely correlated with the overall hydrophobicity of their h regions. This correlation was strengthened by the observation that the B. amyloliquefaciens levansucrase signal peptide, whose h region has an overall hydrophobicity similar to that of E. coli signal peptides, was able to direct secretion of only modest levels of MBP and OmpA. These results imply that there are differences between the secretion machineries of B. subtilis and E. coli and demonstrate that the outer membrane protein OmpA can be translocated across the cytoplasmic membrane of B. subtilis.
Collier
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DN
Central Research and Development Division, E. I. DuPont de Nemours & Co., Wilmington, Delaware 19880-0328.
D018528:ATP-Binding Cassette Transporters; D000469:Alkaline Phosphatase / Q000378:metabolism; D000595:Amino Acid Sequence; D001412:Bacillus subtilis / Q000378:metabolism*; D001425:Bacterial Outer Membrane Proteins / Q000378:metabolism; D001426:Bacterial Proteins / Q000378:metabolism*; D001483:Base Sequence; D001692:Biological Transport; D002352:Carrier Proteins / Q000378:metabolism; D002451:Cell Compartmentation / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics*; D029968:Escherichia coli Proteins; D058619:Maltose-Binding Proteins; D008969:Molecular Sequence Data; D009004:Monosaccharide Transport Proteins; D033902:Periplasmic Binding Proteins; D011499:Protein Processing, Post-Translational; D021382:Protein Sorting Signals / Q000235:genetics* / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D013045:Species Specificity
D018528:ATP-Binding Cassette Transporters; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D002352:Carrier Proteins; D029968:Escherichia coli Proteins; C461619:MalE protein, E coli; D058619:Maltose-Binding Proteins; D009004:Monosaccharide Transport Proteins; D033902:Periplasmic Binding Proteins; D021382:Protein Sorting Signals; C028003:RbsB protein, E coli; D011994:Recombinant Proteins; C461599:maltose transport system, E coli; D000469:Alkaline Phosphatase