The 70 kilodalton heat shock related proteins (Hsp70's) make up a pervasive family of molecular chaperones that inhibit protein aggregation and misfolding by repetitively binding and releasing unstructured or incorrectly folded segments of polypeptide, thereby providing an opportunity for correct (re)folding upon release. Although first characterized as proteins whose level increased in response to cell stress, various constitutively-expressed Hsp70 proteins are now known to participate in a spectrum of cellular processes under normal conditions, indicating an essential role in cell viability for this family of proteins.
Release of polypeptides by Hsp70 proteins is dependent on ATP. The polypeptide binding activity and ATPase activity reside in discrete and separable structural domains of the Hsp70 proteins. At the same time, the activities are coupled in such a manner that ATP binding induces polypeptide release.
Our work in this field has evolved from early crystallographic work on the ATPase fragment of the bovine heat shock cognate protein (Hsc70),through studies on the ATPase kinetic cycle and mechanism, and the ATP-induced conformational change of the protein.
Initial structure of ATPase fragment and its similarity with actin
Small-angle x-ray scattering studies of solution structure
Flaherty, K. M., DeLuca-Flaherty, C., and McKay, D. B. (1990). "Three-Dimensional Structure of the ATPase Fragment of a 70 Kilodalton Heat Shock Cognate Protein."
Nature 346, 623-628. [PubMed]
Flaherty, K. M., McKay, D. B., Kabsch, W., and Holmes, K. C. (1991). "Similarity of the Three-dimensional Structures of Actin and the ATPase Fragment of a 70-kDa Heat Shock Cognate Protein."
Proc. Natl. Acad. Sci. USA 88, 5041-5045.; [PubMed]
Wilbanks, S. M., Chen, L., Tsuruta, H., Hodgson, K. O., and
McKay, D. B. (1995). "Solution small-angle X-ray scattering study of the molecular chaperone Hsc70 and its subfragments."
Biochemistry 34, 12095-12106.; [PubMed]
Kinetics of ATPase cycle, peptide binding, and conformational changes
Wilbanks, S. M., DeLuca-Flaherty, C., and McKay, D. B. (1994). "Structural basis of the Hsc70 ATP hydrolytic activity. I. Kinetic analyses of active site mutants."
J. Biol. Chem. 269, 12893-12898. [PubMed]
Flaherty, K. M., Wilbanks, S. M., DeLuca-Flaherty, C., and McKay, D.
B. (1994). "Structural basis of the Hsc70 ATP hydrolytic activity. II. Structure of the active site with ADP or ATP bound to wild-type and mutant ATPase fragment."
J. Biol. Chem. 269, 12899-12907. [PubMed]
O'Brien, M. C., and McKay, D. B. (1995). "How potassium affects the activity of the molecular chaperone Hsc70: I. Potassium is required for
optimal ATPase activity."
J. Biol.Chem. 270, 2247-2250.
Wilbanks, S. M., and McKay, D. B. (1995). "How potassium affects the
activity of the molecular chaperone Hsc70: II. Potassium binds specifically in the ATPase active site."
J. Biol. Chem. 270, 2251-2257.
[ATPase fragment (with K+) coordinates]
O'Brien, M. C., Flaherty, K. M., and McKay, D. B. (1996). "Lysine 71 of the chaperone protein Hsc70 is essential for ATP hydrolysis."
J. Biol. Chem. 271, 15874-15878.
Wilbanks, S. M., and McKay, D. B. (1998). "Structural replacement of
active site cations by the e-amino group of lysine in the ATPase fragment of bovine Hsc70."
Biochemistry 37, 7456-7462.
Coupling between ATPase cycle and conformational change
Ha, J.-H., and McKay, D. B. (1994). "ATPase kinetics of recombinant
bovine 70 kilodaltion heat shock cognate protein and its amino-terminal ATPase domain."
Biochemistry 33, 14625-14635.
Ha, J.-H., and McKay, D. B. (1995). "Kinetics of nucleotide-induced changes in the tryptophan fluorescence of the molecular chaperone Hsc70 and its subfragments suggest the ATP-induced conformational change follows initial ATP binding."
Biochemistry 34, 11635-11644.
Ha, J.-H., Hellman, U., Johnson, E. R., Li, L., McKay, D. B.,
Sousa, M. S., Takeda, S., Wernstedt, C., and Wilbanks, S. M. (1997). "Destabilization of peptide binding and inter-domain communication by an E543K mutation in the bovine seventy kilodalton heat shock cognate protein, a molecular chaperone."
J. Biol. Chem. 272, 27796-27803.
Sousa, M. C., and McKay, D. B. (1998). "The hydroxyl of threonine 13
of the bovine 70 kilodalton heat shock cognate protein is essential for transducing the ATP-induced conformational change."
Biochemistry 37, 15392-15399.
Johnson, E. R., and McKay, D. B. (1999). "Mapping the role of active
site residues for tranducing an ATP-induced conformational change in the bovine 70-kDa heat shock cognate protein."
Biochemistry 38, 10823-10830.