The mature portion of Escherichia coli maltose-binding protein (MBP) determines the dependence of MBP on SecB for export.
The product of the secB gene is required for export of a subset of secreted proteins to the outer membrane and periplasm of Escherichia coli. Precursor maltose-binding protein (MBP) accumulates in the cytoplasm of secB-carrying mutants, but export of alkaline phosphatase is only minimally affected by secB mutations. When export of MBP-alkaline phosphatase hybrid proteins was analyzed in wild-type and secB-carrying mutant strains, the first third of mature MBP was sufficient to render export of the hybrid proteins dependent on SecB. Substitution of a signal sequence from a SecB-independent protein had no effect on SecB-dependent export. These findings show that the first third of mature MBP is capable of conferring export incompetence on an otherwise competent protein.
Gannon
P M
PM
Department of Physiology, Tufts University School of Medicine, Boston, Massachusetts 02111.
Li
P
P
Kumamoto
C A
CA
D018528:ATP-Binding Cassette Transporters; D000469:Alkaline Phosphatase / Q000235:genetics; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics*; D001483:Base Sequence; D002352:Carrier Proteins / Q000235:genetics*; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins; D005796:Genes; D005798:Genes, Bacterial; D005838:Genotype; D008320:Maltose / Q000378:metabolism*; D058619:Maltose-Binding Proteins; D008969:Molecular Sequence Data; D009004:Monosaccharide Transport Proteins; D009154:Mutation; D010957:Plasmids
D018528:ATP-Binding Cassette Transporters; D001426:Bacterial Proteins; D002352:Carrier Proteins; D029968:Escherichia coli Proteins; D058619:Maltose-Binding Proteins; D009004:Monosaccharide Transport Proteins; C057842:SecB protein, Bacteria; C461599:maltose transport system, E coli; D008320:Maltose; D000469:Alkaline Phosphatase