Crystal structures of the ATPase domains of four human Hsp70 isoforms: HSA1L/Hsp70-hom, HSA2/Hsp70-2, HSPA6/Hsp70B’, and HSPA5/BiP/GRP78

Structural Genomics Consortium, Karolinska Institutet, Stockholm, Sweden.
PLoS ONE (Impact Factor: 3.23). 01/2010; 5(1):e8625. DOI: 10.1371/journal.pone.0008625
Source: PubMed


The 70-kDa heat shock proteins (Hsp70) are chaperones with central roles in processes that involve polypeptide remodeling events. Hsp70 proteins consist of two major functional domains: an N-terminal nucleotide binding domain (NBD) with ATPase activity, and a C-terminal substrate binding domain (SBD). We present the first crystal structures of four human Hsp70 isoforms, those of the NBDs of HSPA1L, HSPA2, HSPA5 and HSPA6. As previously with Hsp70 family members, all four proteins crystallized in a closed cleft conformation, although a slight cleft opening through rotation of subdomain IIB was observed for the HSPA5-ADP complex. The structures presented here support the view that the NBDs of human Hsp70 function by conserved mechanisms and contribute little to isoform specificity, which instead is brought about by the SBDs and by accessory proteins.

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    • "The NBD consists of 2 large domains (I and II), which can be further divided into 2 subdomains (A and B). Domains I and II form a cleft, with IA and IIA lining the base and IB and IIB forming the walls of the nucleotide binding pocket (Fig. 1A) [36] [37] [38] [39] [40]. The NBD is followed by a short linker domain that couples nucleotide hydrolysis in the NBD to the opening and closing of the substrate binding pocket of the SBD [41] [42] [43]. "
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    • "Furthermore, while several crystal structures are available for the human NBD, most capture it in a relatively closed conformation (Sriram et al., 1997; Wisniewska et al., 2010). In contrast, recent nuclear magnetic resonance (NMR) techniques and molecular dynamics studies suggest considerable flexibility and rearrangements in this domain with the cleft opening upon ADP binding (Bhattacharya et al., 2009; Woo et al., 2009). "
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    • "The FLAG-epitope allowed us to detect expression of this mutant protein. The position of the insertion was chosen since it is in-between the conserved domains of GRP78 deduced by sequence alignment map [44] and it lies outside of the ATP binding domain of GRP78 located between aa 125 and aa 280. This will avoid disrupting the critical ATPase function of GRP78 as well as preserving the ER targeting signal at the N-terminus. "
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