title: Escherichia coli SecB protein associates with exported protein precursors in vivo.
abstract: The product of the Escherichia coli secB gene is required for efficient export of proteins across the cytoplasmic membrane. The studies described in this report show that in wild-type growing cells, SecB protein associates with precursor forms of exported proteins, such as the periplasmic maltose-binding protein (MBP) and the outer-membrane proteins LamB and OmpA. In contrast, the cytoplasmic protein beta-galactosidase was not found in association with SecB. Pulse-chase analysis showed that the SecB-precursor MBP complex was short lived, as expected for a complex that represents an intermediate in the protein-export pathway. The results support the hypothesis that SecB protein associates with exported protein precursors in the cytoplasm and dissociates prior to or during translocation of precursors across the cell membrane.
authors.affiliation: Department of Physiology, Tufts University School of Medicine, Boston, MA 02111.
authors.forename: C A
authors.initials: CA
authors.lastname: Kumamoto
mesh_terms: D018528:ATP-Binding Cassette Transporters; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism*; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D004926:Escherichia coli / Q000254:growth & development / Q000378:metabolism*; D029968:Escherichia coli Proteins; D008320:Maltose / Q000378:metabolism; D058619:Maltose-Binding Proteins; D009004:Monosaccharide Transport Proteins; D033902:Periplasmic Binding Proteins; D011499:Protein Processing, Post-Translational
chemical_list: 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; C057842:SecB protein, Bacteria; C461599:maltose transport system, E coli; D008320:Maltose