title: Direct inter-subdomain interactions switch between the closed and open forms of the Hsp70 nucleotide-binding domain in the nucleotide-free state.
abstract: The 70 kDa heat-shock proteins (Hsp70s) are highly conserved chaperones that are involved in several cellular processes, such as protein folding, disaggregation and translocation. In this study, the crystal structures of the human Hsp70 nucleotide-binding domain (NBD) fragment were determined in the nucleotide-free state and in complex with adenosine 5'-(beta,gamma-imido)triphosphate (AMPPNP). The structure of the nucleotide-free NBD fragment is similar to that of the AMPPNP-bound NBD fragment and is designated as the ;closed form'. In the nucleotide-free NBD fragment the closed form is intrinsically supported through interactions between Tyr15, Lys56 and Glu268 which connect subdomains IA, IB and IIB at the centre of the protein. Interaction with the substrate-binding domain (SBD) of Hsp70 or the BAG domain of BAG1 impairs this subdomain connection and triggers the rotation of subdomain IIA around a hydrophobic helix from subdomain IA. The subdomain rotation is limited by Asp199 and Asp206 from subdomain IIA and clearly defines the open form of the NBD. The open form is further stabilized by a new interaction between Gly230 from subdomain IIB and Ser340 from subdomain IIA. The structure of the NBD in the nucleotide-free state is determined by switching of the inter-subdomain interactions.
authors.affiliation: Department of Biophysics and Biochemistry, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
authors.forename: Meiri
authors.initials: M
authors.lastname: Shida
authors.forename: Akihiko
authors.initials: A
authors.lastname: Arakawa
authors.forename: Ryohei
authors.initials: R
authors.lastname: Ishii
authors.forename: Seiichiro
authors.initials: S
authors.lastname: Kishishita
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Takagi
authors.forename: Mutsuko
authors.initials: M
authors.lastname: Kukimoto-Niino
authors.forename: Sumio
authors.initials: S
authors.lastname: Sugano
authors.forename: Akiko
authors.initials: A
authors.lastname: Tanaka
authors.forename: Mikako
authors.initials: M
authors.lastname: Shirouzu
authors.forename: Shigeyuki
authors.initials: S
authors.lastname: Yokoyama
mesh_terms: D001665:Binding Sites; D018360:Crystallography, X-Ray; D018840:HSP70 Heat-Shock Proteins / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism; D006801:Humans; D008958:Models, Molecular; D009711:Nucleotides / Q000378:metabolism*; D017434:Protein Structure, Tertiary
chemical_list: D018840:HSP70 Heat-Shock Proteins; D009711:Nucleotides