The present invention discloses characterization of interactions between ligands and Hsp90 proteins, including GRP94, wherein ligand binding to the N-terminal nucleotide binding domain of GRP94 elicits a conformational change that converts the GRP94 from an inactive to an active conformation, and wherein the chaperone and peptide-binding activities of the GRP94 are markedly stimulated. Also disclosed are purification, screening, and therapeutic methods pertaining to the biological activity of GRP94, and in some instances HSP90, based upon the characterization of ligand interactions of Hsp90 peptide-binding proteins, including GRP94.