title: The proper ratio of GrpE to DnaK is important for protein quality control by the DnaK-DnaJ-GrpE chaperone system and for cell division.
abstract: A balance of the intracellular concentrations of molecular chaperones in response to environmental conditions is of considerable importance for cellular homeostasis. Here, the physiological consequences of overexpression of GrpE in wild-type Escherichia coli MC4100 were examined. Overexpression of GrpE resulted in defects in cell division and growth, but overexpression of GrpE-G122D, which carries the G122D point mutation resulting in impaired interaction with DnaK, did not; this indicated that the effect of GrpE overexpression could be related to the DnaK chaperone function. Phase-contrast and fluorescence micrographs suggested that the N-terminal GFP-fused GrpE was colocalized with DnaK on the surface of inclusion bodies. An in vitro luciferase-refolding activity assay using purified DnaK, DnaJ and GrpE proteins demonstrated that high concentrations of GrpE significantly inhibited DnaK-mediated refolding. Furthermore, cell-free extracts from wild-type cells and GrpE-G122D-overexpressing cells significantly enhanced the refolding of luciferase. In the GrpE-overexpressing cells, abnormal localization of the cell-division protein FtsZ was observed by indirect immunofluorescence microscopy. In conclusion, the overexpression of GrpE caused a defect in the functionality of the DnaK chaperone system; this would result in filamentous morphology via abnormalities in the cell-division machinery.
authors.affiliation: Laboratory of Functional Food Design, Department of Functional Metabolic Design, Bio-Architecture Center, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan.|Laboratory of Microbial Technology, Division of Microbial Science and Technology, Department of Bioscience and Biotechnology, Faculty of Agriculture, Graduate School, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan.
authors.forename: Shinya
authors.initials: S
authors.lastname: Sugimoto
authors.affiliation: Laboratory of Microbial Technology, Division of Microbial Science and Technology, Department of Bioscience and Biotechnology, Faculty of Agriculture, Graduate School, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan.
authors.forename: Kozue
authors.initials: K
authors.lastname: Saruwatari
authors.affiliation: Laboratory of Microbial Technology, Division of Microbial Science and Technology, Department of Bioscience and Biotechnology, Faculty of Agriculture, Graduate School, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan.
authors.forename: Chihana
authors.initials: C
authors.lastname: Higashi
authors.affiliation: Laboratory of Functional Food Design, Department of Functional Metabolic Design, Bio-Architecture Center, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan.|Laboratory of Microbial Technology, Division of Microbial Science and Technology, Department of Bioscience and Biotechnology, Faculty of Agriculture, Graduate School, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan.
authors.forename: Kenji
authors.initials: K
authors.lastname: Sonomoto
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D002455:Cell Division; D003598:Cytoskeletal Proteins / Q000235:genetics / Q000378:metabolism; D004926:Escherichia coli / Q000166:cytology* / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D050956:HSP40 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D006360:Heat-Shock Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D018832:Molecular Chaperones / Q000235:genetics / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D003598:Cytoskeletal Proteins; C494635:DnaJ protein, E coli; D029968:Escherichia coli Proteins; C071525:FtsZ protein, Bacteria; C489400:GrpE protein, E coli; D050956:HSP40 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D018832:Molecular Chaperones; C063842:dnaK protein, E coli