| Budget Amount *help |
¥3,100,000 (Direct Cost: ¥3,100,000)
Fiscal Year 2000: ¥1,500,000 (Direct Cost: ¥1,500,000)
Fiscal Year 1999: ¥1,600,000 (Direct Cost: ¥1,600,000)
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| Research Abstract |
We have studied structure and cellular functions of an essential, membrane-bound ATP-dependent protease, FtsH in E.coli. FtsH forms oligomers, and oligomerization is essential for its activity. Site-directed mutagenesis and homology modeling revealed that the ATP-binding pocket is formed at the interface of neighboring subunits, and that invariant residues in the AAA ATPase-specific sequence, SRH, play important roles in ATP hydrolysis. These results have led us to propose an intermolecular catalysis model for the hexameric AAA ATPase. The model also suggests that unfolded substrates are threaded through the central hole of the hexameric ring of the ATPase, and that the size of the central hole is altered upon ATP hydrolysis. We have succeeded to crystallize the ATPase domain of FtsH, however X-ray diffraction data have not been sufficient to resolve the crystal structure. FtsH controls several cellular functions by degrading specific regulatory proteins such as sigma32 and LpxC.Sigma32 is the heat shock transcription factor and is degraded by FtsH.Efficient degradation of sigma32 by FtsH requires the DnaK chaperone system, which may alter sigma32 to a form competent to the FtsH action. We isolated two temperature-sensitive ftsH mutants newly, and mutations of these mutants were mapped to the C-terminal region of ftsH.Mini-F plasmids are unstably maintained in temperature-sensitive ftsH mutants at permissive temperatures for cell growth. We have also studied lysis-lysogeny decision of lambda phage and colicin tolerance in ftsH mutants. We have identified SpoVM as a substrate of B.subtilis FtsH, suggesting Ftsh's involvement in sporulation. SpoVM acts for the membrane and exerts an inhibitory effect on cell growth.
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