Interaction of hsp70 with unfolded proteins: effects of temperature and nucleotides on the kinetics of binding

  1. D R Palleros,
  2. W J Welch, and
  3. A L Fink
  1. Department of Chemistry and Biochemistry, University of California, Santa Cruz 95064.

Abstract

Circular dichroism and HPLC gel filtration were used to show that cytosolic hsp70 is thermally stable but undergoes a conformational transition (midpoint, 43 degrees C; 57 degrees C in the presence of ATP or ADP) leading to oligomerization. hsp70 binds to unfolded, but not to folded, proteins in a temperature-dependent manner; complex formation is significant only at physiologically relevant temperatures. hsp70 binds ADP more tightly than ATP to form a binary complex, which binds to the unfolded protein more rapidly than free hsp70. ADP also inhibits the ATP-induced dissociation of the hsp70-protein complex. A regulatory role for the hsp70-nucleotide binary complexes is proposed.

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  1. PNAS July 1, 1991 vol. 88 no. 13 5719-5723
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