アクティブボード・２００９年　３月
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研究発表を行った学会；
・特定領域研究「タンパク質の社会」若手ワークショップ.
　２００８年　９月２５日(東京)

タイトル；The proper ratio of GrpE to DnaK is important for protein-quality control by DnaK-DnaJ-GrpE chaperone system and for cell division.
　
発表者；　杉本　真也　氏
　　　（熊本大学　発生医学研究センター　細胞複製分野）
Abstract；
A balance of the intracellular concentrations of molecular chaperones in response to environmental conditions is quite important for cellular homeostasis. Here, physiological consequence of overexpression of GrpE in wild-type Escherichia coli MC4100 was examined. Overexpression of GrpE resulted in defects in cell division and growth, but that 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. In vitro luciferase-refolding activity assay using purified DnaK/DnaJ/GrpE proteins demonstrated that high concentrations of GrpE significantly inhibited the 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 the defect in the functionality of the DnaK chaperone system; this would result in filamentous morphology via abnormalities in the cell-division machinery.