title: From the common molecular basis of the AAA protein to various energy-dependent and -independent activities of AAA proteins.
abstract: AAA (ATPase associated with various cellular activities) proteins remodel substrate proteins and protein complexes upon ATP hydrolysis. Substrate remodelling is diverse, e.g. proteolysis, unfolding, disaggregation and disassembly. In the oligomeric ring of the AAA protein, there is a conserved aromatic residue which lines the central pore. Functional analysis indicates that this conserved residue in AAA proteases is involved in threading unfolded polypeptides. Katanin and spastin have microtubule-severing activity. These AAA proteins also possess a conserved aromatic residue at the central pore, suggesting its importance in their biological activity. We have constructed pore mutants of these AAA proteins and have obtained in vivo and in vitro results indicating the functional importance of the pore motif. Degradation of casein by the Escherichia coli AAA protease, FtsH, strictly requires ATP hydrolysis. We have constructed several chimaeric proteases by exchanging domains of FtsH and its homologues from Caenorhabditis elegans mitochondria, and examined their ATPase and protease activities in vitro. Interestingly, it has been found that some chimaeras are able to degrade casein in an ATP-independent manner. The proteolysis is supported by either ATP[S] (adenosine 5'-[gamma-thio]triphosphate) or ADP, as well as ATP. It is most likely that substrate translocation in these chimaeras occurs by facilitated diffusion. We have also investigated the roles of C. elegans p97 homologues in aggregation/disaggregation of polyglutamine repeats, and have found that p97 prevents filament formation of polyglutamine proteins in an ATP-independent fashion.
authors.affiliation: Division of Molecular Cell Biology, Institute of Molecular Embryology and Genetics, Kumamoto University, Kumamoto 860-0811, Japan. ogura@gpo.kumamoto-u.ac.jp
authors.forename: Teru
authors.initials: T
authors.lastname: Ogura
authors.forename: Yuka
authors.initials: Y
authors.lastname: Matsushita-Ishiodori
authors.forename: Ai
authors.initials: A
authors.lastname: Johjima
authors.forename: Masayo
authors.initials: M
authors.lastname: Nishizono
authors.forename: Shingo
authors.initials: S
authors.lastname: Nishikori
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Esaki
authors.forename: Kunitoshi
authors.initials: K
authors.lastname: Yamanaka
mesh_terms: D020816:Amino Acid Motifs; D000818:Animals; D017173:Caenorhabditis elegans / Q000201:enzymology*; D002460:Cell Line; D017124:Conserved Sequence; D006801:Humans; D008666:Metalloendopeptidases / Q000737:chemistry* / Q000378:metabolism*; D008870:Microtubules / Q000378:metabolism; D008958:Models, Molecular; D013816:Thermodynamics
chemical_list: D008666:Metalloendopeptidases; C114583:m-AAA proteases