This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. The Hsp70 chaperone system is ubiquitous family of proteins involved in a variety of critical cellular processes such as protein homeostasis, stress response and membrane translocation. Substrate refolding by Hsp70 occurs through the interaction of unfolded polypeptide substrates with DnaK (the E.coli Hsp70), as well as cochaperones DnaJ and GrpE, in a complex ATP-dependent chaperone cycle. However, the molecular mechanism by which substrates are refolded to their native state is poorly understood. The goal of this work is to probe the conformation of Hsp70-bound polypeptide substrates at high resolution using NMR spectroscopy. In particular, we study the nucleotide-induced changes in the backbone conformation of peptide substrates using Ca and C'secondary chemical shifts as residue-specific probes of secondary structure.