tailieunhanh - Báo cáo khoa học: A hydrophobic segment within the C-terminal domain is essential for both client-binding and dimer formation of the HSP90-family molecular chaperone

Thea isoform of human 90-kDa heat shock protein (HSP90a) is composed of three domains: the N-terminal (residues 1–400); middle (residues 401–615) and C-terminal (residues 621–732). The middle domain is simultaneously associated with the N- and C-terminal domains, and the interactionwith the lattermediates thedimeric configuration of HSP90. Besides one in the N-terminal domain, an addi-tional client-binding site exists in the C-terminal domain of HSP90. | Eur. J. Biochem. 270 146-154 2003 FEBS 2003 doi A hydrophobic segment within the C-terminal domain is essential for both client-binding and dimer formation of the HSP90-family molecular chaperone Shin-ichi Yamada1 2 Toshio Ono2 Akio Mizuno1 and Takayuki K. Nemoto2 1 Division of Oral and Maxillofacial Surgery and 2 Division of Oral Molecular Biology Department of Developmental and Reconstructive Medicine Course of Medical and Dental Sciences Nagasaki University Graduate School of Biomedical Sciences Japan The a isoform of human 90-kDa heat shock protein HSP90a is composed of three domains the N-terminal residues 1-400 middle residues 401-615 and C-terminal residues 621-732 . The middle domain is simultaneously associated with the N- and C-terminal domains and the interaction with the latter mediates the dimeric configuration of HSP90. Besides one in the N-terminal domain an additional client-binding site exists in the C-terminal domain of HSP90. The aim of the present study is to elucidate the regions within the C-terminal domain responsible for the bindings to the middle domain and to a client protein and to define the relationship between the two functions. A bacterial two-hybrid system revealed that residues 650-697 of HSP90a were essential for the binding to the middle domain. An almost identical region residues 657-720 was required for the suppression of heat-induced aggregation of citrate synthase a model client protein. Replacement of either Leu665-Leu666 or Leu671-Leu672 to Ser-Ser within the hydrophobic segment residues 662-678 of the C-terminal domain caused the loss of bindings to both the middle domain and the client protein. The interaction between the middle and C-terminal domains was also found in human 94-kDa glucose-regulated protein. Moreover Escherichia coli HtpG a bacterial HSP90 homologue formed heterodimeric complexes with HSP90a and the 94-kDa glucose-regulated protein through their middle-C-terminal domains. .