Interaction of hsp70 with unfolded proteins: effects of temperature and nucleotides on the kinetics of binding.
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.
Palleros
D R
DR
Department of Chemistry and Biochemistry, University of California, Santa Cruz 95064.
Welch
W J
WJ
Fink
A L
AL
D000244:Adenosine Diphosphate / Q000378:metabolism; D000251:Adenosine Triphosphatases / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002417:Cattle; D002942:Circular Dichroism; D006360:Heat-Shock Proteins / Q000378:metabolism*; D006358:Hot Temperature; D006801:Humans; D066298:In Vitro Techniques; D007768:Lactalbumin / Q000378:metabolism; D008836:Micrococcal Nuclease / Q000378:metabolism; D011485:Protein Binding; D011487:Protein Conformation; D011489:Protein Denaturation
D006360:Heat-Shock Proteins; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D007768:Lactalbumin; D008836:Micrococcal Nuclease; D000251:Adenosine Triphosphatases