Hsp70 and Its Cofactors

Polypeptide binding and release by Hsp70 is coupled to its nucleotidebinding state. Furthermore, Hsp70 proteins often act in concert with cofactors involved in the regulation of its ATPase cycle. These cofactors thereby indirectly contribute to the process of polypeptide binding and release (see chapter by Mayer et al., in this volume). 

For mitochondria, another independently interacting cytosolic factor, termed mitochondrial import stimulation factor (MSF), is also important for guiding preproteins to its surface (Mihara and Omura, 1996). Studies by Mihara and coworkers have indicated that cytosolic Hsp70 

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