The chaperoning activity of hsp110 - Identification of functional domains by use of targeted deletions

hsp110 is one of major heat shock proteins of eukaryotic cells and is a div erged relative of the hsp70 family. It has been previously shown that hsp11 0 maintains heat-denatured luciferase in a soluble, folding competent state and also confers cellular heat resistance in vivo. In the present study th e functional domains of hsp110 that are responsible for its chaperoning act ivity are identified by targeted deletion mutagenesis using the DnaK struct ure as the model. The chaperoning activity of mutants is assessed based on their ability to solubilize heat-denatured luciferase as well as to refold luciferase in the presence of rabbit reticulocyte lysate. It is shown that these functions require only an internal region of hsp110 that includes the predicted peptide binding domain and two immediately adjacent C-terminal d omains. It is also shown that although hsp110 binds ATP, binding can be blo cked by its C-terminal region.