| Budget Amount *help |
¥17,330,000 (Direct Cost: ¥15,200,000、Indirect Cost: ¥2,130,000)
Fiscal Year 2007: ¥9,230,000 (Direct Cost: ¥7,100,000、Indirect Cost: ¥2,130,000)
Fiscal Year 2006: ¥8,100,000 (Direct Cost: ¥8,100,000)
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| Research Abstract |
Molecular mechanisms of the AAA ATPase domain of AAA family proteins such as ATP hydrolysis and handling of substrate proteins have been studied. Mutagenesis of residues around the pore region of the hexametric ATPase ring of an AAA protease, FtsH, indicated that some acidic residues are functionally important. We have found that degradation of unfolded polypeptides by some chimeras of FtsH and its C. elegans homologs did not require ATP hydrolysis, and that it was also independent of the conserved aromatic residues located at the pore, suggesting the possibility of energy-independent substrate translocation. We have obtained firm evidence for an intersubunit catalysis mechanism of ATP hydrolysis by AAA ATPases using mutants of the C. elegans fidgetin homolog, FIGL-1. We have observed that CDC-48.1 and CDC-48.2, p97 homologs in C. elegans, suppress aggregate formation of huntingtin fragments in an ATP-independent manner. Effects of SPAS-1, the C. elegans homolog of spastin, and human katanin on microtubule dynamics have been studied. Overexpression of wild-type SPAS-1 caused disassembly of microtubule network, whereas that of a Walker or pore mutant did not. On the other hand, severing of fluorescently labeled microtubules by human katanin was observed under a fluorescent microscope. It was found that pore mutants of katanin lost the microtubule-severing activity. Processes of microtubule-severing, which was dependent on both katanin and ATP, were observed under a high-speed atomic force microscope.
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