title: Regions of maltose-binding protein that influence SecB-dependent and SecA-dependent export in Escherichia coli.
abstract: In Escherichia coli, the efficient export of maltose-binding protein (MBP) is dependent on the chaperone SecB, whereas export of ribose-binding protein (RBP) is SecB independent. To localize the regions of MBP involved in interaction with SecB, hybrids between MBP and RBP in SecB mutant cells were constructed and analyzed. One hybrid consisted of the signal peptide and first third of the mature moiety of MBP, followed by the C-terminal two-thirds of RBP (MBP-RBP112). This hybrid was dependent upon SecB for its efficient export and exhibited a strong export defect in secA mutant cells. A hybrid between RBP and MBP with the same fusion point was also constructed (RBP-MBP116). The RBP-MBP116 hybrid remained SecB independent and only exhibited a partial export defect in secA mutant cells. In addition, MBP species with specific alterations in the early mature region were less dependent on SecB for their efficient export. The export of these altered MBP species was also less affected in secA mutant cells and in cells treated with sodium azide. These results present additional evidence for the targeting role of SecB.
authors.affiliation: Department of Microbiology and Immunology, School of Medicine, University of North Carolina, Chapel Hill 27599-7290.
authors.forename: S M
authors.initials: SM
authors.lastname: Strobel
authors.forename: J G
authors.initials: JG
authors.lastname: Cannon
authors.forename: P J
authors.initials: PJ
authors.lastname: Bassford
mesh_terms: D018528:ATP-Binding Cassette Transporters; D000251:Adenosine Triphosphatases / Q000378:metabolism*; D001426:Bacterial Proteins / Q000378:metabolism*; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins; D005798:Genes, Bacterial; D007700:Kinetics; D008320:Maltose / Q000378:metabolism*; D058619:Maltose-Binding Proteins; D026901:Membrane Transport Proteins; D009004:Monosaccharide Transport Proteins; D016297:Mutagenesis, Site-Directed; D033902:Periplasmic Binding Proteins; D010957:Plasmids; D011498:Protein Precursors / Q000378:metabolism; D000069816:SEC Translocation Channels; D000081416:SecA Proteins
chemical_list: D018528:ATP-Binding Cassette Transporters; D001426:Bacterial Proteins; D002352:Carrier Proteins; D029968:Escherichia coli Proteins; D058619:Maltose-Binding Proteins; D026901:Membrane Transport Proteins; D009004:Monosaccharide Transport Proteins; D033902:Periplasmic Binding Proteins; D011498:Protein Precursors; C028003:RbsB protein, E coli; D000069816:SEC Translocation Channels; C461599:maltose transport system, E coli; D008320:Maltose; D000251:Adenosine Triphosphatases; D000081416:SecA Proteins