Crystal structure of the C-terminal three-helix bundle subdomain of C. elegans Hsp70.
Hsp70 chaperones are composed of two domains; the 40 kDa N-terminal nucleotide-binding domain (NDB) and the 30 kDa C-terminal substrate-binding domain (SBD). Structures of the SBD from Escherichia coli homologues DnaK and HscA show it can be further divided into an 18 kDa beta-sandwich subdomain, which forms the hydrophobic binding pocket, and a 10 kDa C-terminal three-helix bundle that forms a lid over the binding pocket. Across prokaryotes and eukaryotes, the NBD and beta-sandwich subdomain are well conserved in both sequence and structure. The C-terminal subdomain is, however, more evolutionary variable and the only eukaryotic structure from rat Hsc70 revealed a diverged helix-loop-helix fold. We have solved the crystal structure of the C-terminal 10 kDa subdomain from Caenorhabditis elegans Hsp70 which forms a helical-bundle similar to the prokaryotic homologues. This provides the first confirmation of the structural conservation of this subdomain in eukaryotes. Comparison with the rat structure reveals a domain-swap dimerisation mechanism; however, the C. elegans subdomain exists exclusively as a monomer in solution in agreement with the hypothesis that regions out with the C-terminal subdomain are necessary for Hsp70 self-association.
Worrall
Liam J
LJ
Centre for Translational and Chemical Biology, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3JR, UK.
Walkinshaw
Malcolm D
MD
D000595:Amino Acid Sequence; D000818:Animals; D029742:Caenorhabditis elegans Proteins / Q000737:chemistry* / Q000648:ultrastructure*; D003198:Computer Simulation; D003461:Crystallography; D018840:HSP70 Heat-Shock Proteins / Q000737:chemistry* / Q000648:ultrastructure*; D008956:Models, Chemical; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D051381:Rats; D017386:Sequence Homology, Amino Acid
D029742:Caenorhabditis elegans Proteins; D018840:HSP70 Heat-Shock Proteins