J proteins catalytically activate Hsp70 molecules to trap a wide range of peptide sequences |
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Authors: | B Misselwitz O Staeck TA Rapoport |
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Affiliation: | Howard Hughes Medical Institute, Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115, USA. |
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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. |
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