title: The region adjacent to the highly immunogenic site and shielded by the middle domain is responsible for self-oligomerization/client binding of the HSP90 molecular chaperone.
abstract: We here investigated the mechanism of self-oligomerization of the 90-kDa heat shock protein (HSP90) molecular chaperone, because it is known that this oligomerization reflects the client-binding activity. The transition temperatures for the self-oligomerization of the full-length forms of human HSP90alpha and HtpG (bacterial HSP90), i.e., 45 and 60 degrees C, respectively, were identical to those for the dissociation of the recombinant N domain (residues 1-400 of human HSP90alpha and residues 1-336 of HtpG in our definition) from the remainder of the molecule. The N domain of human HSP90alpha expressed in Escherichia coli was oligomeric, and the oligomerization activity was localized within residues 311-350, i.e., C-terminally adjacent to the highly immunogenic site (residues 291-304). Particularly, residues 341-350 were critical on oligomerization. On the other hand, residues 289-389 were indispensable for the interaction with the M domain (residues 401-618) of the molecule. Oligomer formation of the N domain was efficiently suppressed by its extension until Lys546, i.e., residues 401-546, which is required for the interaction with the N domain. Among highly conserved amino acids at residues 289-400, Trp297, Pro379, and Phe384 were essential for the interaction with the M domain. With these observations taken together, we propose as the activation mechanism of HSP90 molecular chaperone that heat stress induces the liberation of the oligomerization/client-binding site of residues 311-350 by disrupting the intramolecular interaction between residues 289-389 and 401-546.
authors.affiliation: Division of Oral Molecular Biology, Nagasaki University Graduate School of Biomedical Sciences, 1-7-1 Sakamoto, Nagasaki 852-8588, Japan. tnemoto@net.nagasaki-u.ac.jp
authors.forename: Takayuki K
authors.initials: TK
authors.lastname: Nemoto
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Fukuma
authors.forename: Shin-ichi
authors.initials: S
authors.lastname: Yamada
authors.forename: Takeshi
authors.initials: T
authors.lastname: Kobayakawa
authors.forename: Toshio
authors.initials: T
authors.lastname: Ono
authors.forename: Yuko
authors.initials: Y
authors.lastname: Ohara-Nemoto
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D029968:Escherichia coli Proteins; D018841:HSP90 Heat-Shock Proteins / Q000737:chemistry* / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D006801:Humans; D009154:Mutation / Q000235:genetics; D010446:Peptide Fragments / Q000737:chemistry / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D011485:Protein Binding; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D013696:Temperature
chemical_list: D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D018841:HSP90 Heat-Shock Proteins; C489352:HtpG protein, E coli; D010446:Peptide Fragments; D011994:Recombinant Proteins; C066720:HtpG protein, bacteria