Functional characterization of heat shock protein 90 targeted compounds.

Heat shock protein 90 (Hsp90) is an attractive cancer target that possesses two potential binding domains at the C and N termini. Nevertheless, assays that can reliably distinguish between the C- and N-terminal Hsp90 inhibitors and quantitatively characterize candidate drugs are limited. Here we report an Hsp90 binding assay and ATPase inhibition assay that can not only separate the C- and N-terminal inhibitors but also quantitatively determine their respective IC50 values.