The proper ratio of GrpE to Dnak is important for protein quality control by the Dnak-DnaJ-GrpE chaperone system and for cell division

Shinya Sugimoto, Kozue Saruwatari, Chihana Higashi, Kenji Sonomoto

Research output: Contribution to journalArticle

36 Citations (Scopus)

Abstract

A balance of the intracellular concentrations of molecular chaperenes 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-G1 22D, 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.

Original languageEnglish
Pages (from-to)1876-1885
Number of pages10
JournalMicrobiology
Volume154
Issue number7
DOIs
Publication statusPublished - Sep 11 2008

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All Science Journal Classification (ASJC) codes

  • Microbiology

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