title: Effects of Escherichia coli secB mutations on pre-maltose binding protein conformation and export kinetics.
abstract: Mutations affecting the secB gene of Escherichia coli cause a defect in protein export. This report presents the demonstration that the secB mutations caused a defect in co-translational processing of maltose binding protein (MBP). A significant amount of post-translational processing of pre-MBP occurred within 1 min after termination of pulse labeling; at later time points only a small amount of additional processing occurred. The conformation of the intracellular precursor form of MBP was examined in a secB::Tn5 mutant, using protease sensitivity (Randall, L. L., and Hardy, S. J. S. (1986) Cell 46, 921-928) as the assay. In contrast to the isogenic wild type strain, a population of pre-MBP that had folded into a protease resistant conformation was detected in the secB mutant. In addition, sublethal doses of chloramphenicol did not significantly affect protein export in the secB::Tn5 mutant and the secB::Tn5 mutation did not lead to defects in membrane energization.
mesh_terms: D018528:ATP-Binding Cassette Transporters; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone / Q000494:pharmacology; D002352:Carrier Proteins / Q000235:genetics* / Q000493:pharmacokinetics; D002701:Chloramphenicol / Q000494:pharmacology; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism; D029968:Escherichia coli Proteins; D007700:Kinetics; D058619:Maltose-Binding Proteins; D009004:Monosaccharide Transport Proteins; D009154:Mutation; D010447:Peptide Hydrolases / Q000378:metabolism; D011487:Protein Conformation; D011498:Protein Precursors / Q000235:genetics* / Q000493:pharmacokinetics
chemical_list: D018528:ATP-Binding Cassette Transporters; D002352:Carrier Proteins; D029968:Escherichia coli Proteins; D058619:Maltose-Binding Proteins; D009004:Monosaccharide Transport Proteins; D011498:Protein Precursors; C461599:maltose transport system, E coli; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone; D002701:Chloramphenicol; D010447:Peptide Hydrolases