J Proteins Catalytically Activate Hsp70 Molecules to Trap a Wide Range of Peptide Sequences

ArticleinMolecular Cell 2(5):593-603 · December 1998with7 Reads
Impact Factor: 14.02 · DOI: 10.1016/S1097-2765(00)80158-6 · Source: PubMed

    Abstract

    Proteins of the Hsp70 family of ATPases, such as BiP, function together with J proteins to bind polypeptides in numerous cellular processes. Using a solid phase binding assay, we demonstrate that a conserved segment of the J proteins, the J domain, catalytically activates BiP molecules to bind peptides in its immediate vicinity. The J domain interacts with the ATP form of BiP and stimulates hydrolysis resulting in the rapid trapping of peptides, which are then only slowly released upon nucleotide exchange. Activation by the J domain allows BiP to trap peptides or proteins that it would not bind on its own. These results explain why BiP and probably all other Hsp70s can interact with a wide range of substrates and suggest that the J partner primarily determines the substrate specificity of Hsp70s.