title: Heat-shock proteins DnaK and GroEL facilitate export of LacZ hybrid proteins in E. coli.
abstract: The use of lacZ gene fusions, producing a hybrid protein containing an amino terminus specified by a target gene fused to the functional carboxy terminus of beta-galactosidase, has facilitated the study of protein targeting in various organisms. One of the best characterized fusions in Escherichia coli is phi(lamB-lacZ)42-1(Hyb), which produces a hybrid protein with the signal sequence and 181 N-terminal amino acids of the exported protein LamB, attached to LacZ. In common with other LacZ hybrids, the LamB-LacZ(42-1) protein is poorly exported from E. coli, conferring a Lac+ phenotype. beta-Galactosidase activity decreases markedly when cells producing the LamB-LacZ protein are grown at 42 degrees C or when a heat-shock response is induced at lower temperatures by overproducing heat-shock factor RpoH3, indicating the LacZ hybrids are being efficiently targeted to the cell envelope. We now report that the heat-shock proteins DnaK and GroEL can, in sufficient amounts, decrease beta-galactosidase activity and facilitate the export of lacZ-hybrid proteins.
authors.affiliation: Department of Biology, Princeton University, New Jersey 08544.
authors.forename: G J
authors.initials: GJ
authors.lastname: Phillips
authors.forename: T J
authors.initials: TJ
authors.lastname: Silhavy
mesh_terms: D018528:ATP-Binding Cassette Transporters; D001692:Biological Transport / Q000502:physiology; D002352:Carrier Proteins / Q000378:metabolism; D004926:Escherichia coli / Q000378:metabolism*; D029968:Escherichia coli Proteins; D006360:Heat-Shock Proteins / Q000502:physiology*; D008320:Maltose / Q000494:pharmacology; D058619:Maltose-Binding Proteins; D009004:Monosaccharide Transport Proteins; D010957:Plasmids; D021382:Protein Sorting Signals / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism*; D014169:Transformation, Bacterial; D001616:beta-Galactosidase / Q000378:metabolism
chemical_list: D018528:ATP-Binding Cassette Transporters; D002352:Carrier Proteins; D029968:Escherichia coli Proteins; D006360:Heat-Shock Proteins; D058619:Maltose-Binding Proteins; D009004:Monosaccharide Transport Proteins; D021382:Protein Sorting Signals; D011993:Recombinant Fusion Proteins; C461599:maltose transport system, E coli; D008320:Maltose; D001616:beta-Galactosidase