Hsp90 is a widely conserved and ubiquitous molecular chaperone that participates in ATP-dependent protein remodeling in both eukaryotes and prokaryotes. It functions in conjunction with Hsp70 and the Hsp70 cochaperones, an Hsp40 (J-protein) and a nucleotide exchange factor. In E. coli the functional collaboration between Hsp90 Ec and Hsp70, DnaK, requires that the two chaperones directly interact. We used molecular docking to model the interaction of Hsp90 Ec and DnaK. The top-ranked docked model predicted that a region in the nucleotide-binding domain of DnaK interacted with a region in the middle domain of Hsp90 Ec. We then made substitution mutants in DnaK residues suggested by the model to interact with Hsp90 Ec. Eleven of the twelve mutants tested were defective or partially defective in their ability to interact with Hsp90 Ec in vivo in a bacterial two-hybrid assay and in vitro in a Bio-Layer Interferometry assay. These DnaK mutants were also defective in their ability to function collaboratively in protein remodeling with Hsp90 Ec , but retained the ability to act with DnaK cochaperones. Taken together these results suggest that a specific region in the nucleotide-binding domain of DnaK is involved in the interaction with Hsp90 Ec and this interaction is functionally important. Moreover, the region of DnaK that we found to be necessary for Hsp90 Ec binding includes residues that are also involved in J-protein binding, suggesting a functional interplay between DnaK, DnaK cochaperones and Hsp90 Ec .