title: Substitution of only two residues of human Hsp90alpha causes impeded dimerization of Hsp90beta.
abstract: Two isoforms of the 90-kDa heat-shock protein (Hsp90), i.e., Hsp90alpha and Hsp90beta, are expressed in the cytosol of mammalian cells. Although Hsp90 predominantly exists as a dimer, the dimer-forming potential of the beta isoform of human and mouse Hsp90 is less than that of the alpha isoform. The 16 amino acid substitutions located in the 561-685 amino acid region of the C-terminal dimerization domain should be responsible for this impeded dimerization of Hsp90beta (Nemoto T, Ohara-Nemoto Y, Ota M, Takagi T, Yokoyama K. Eur J Biochem 233: 1-8, 1995). The present study was performed to define the amino acid substitutions that cause the impeded dimerization of Hsp90beta. Bacterial two-hybrid analysis revealed that among the 16 amino acids, the conversion from Ala(558) of Hsp90beta to Thr(566) of Hsp90alpha and that from Met(621) of Hsp90beta to Ala(629) of Hsp90alpha most efficiently reversed the dimeric interaction, and that the inverse changes from those of Hsp90alpha to Hsp90beta primarily explained the impeded dimerization of Hsp90beta We conclude that taken together, the conversion of Thr(566) and Ala(629) of Hsp90alpha to Ala(558) and Met(621) is primarily responsible for impeded dimerization of Hsp90beta.
authors.affiliation: Department of Oral Molecular Biology, Course of Medical and Dental Sciences, Nagasaki University Graduate School of Biomedical Sciences, 1-7-1 Sakamoto, Nagasaki, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Kobayakawa
authors.forename: Shin-Ichi
authors.initials: S
authors.lastname: Yamada
authors.forename: Akio
authors.initials: A
authors.lastname: Mizuno
authors.forename: Takayuki K
authors.initials: TK
authors.lastname: Nemoto
mesh_terms: D000409:Alanine / Q000737:chemistry; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D019281:Dimerization; D018841:HSP90 Heat-Shock Proteins / Q000737:chemistry* / Q000235:genetics / Q000502:physiology*; D006801:Humans; D066298:In Vitro Techniques; D008715:Methionine / Q000737:chemistry; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000737:chemistry; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013329:Structure-Activity Relationship; D020798:Two-Hybrid System Techniques
chemical_list: D018841:HSP90 Heat-Shock Proteins; C533585:HSP90AA2P protein, human; C493165:HSP90AB1 protein, human; D011993:Recombinant Fusion Proteins; D008715:Methionine; D000409:Alanine