Abstract
Heat-shock protein 90 (HSP90) is an essential molecular chaperone in eukaryotes. It is important for chaperoning proteins that are important determinants of multistep carcinogenesis. HSP90's ATPase activity is associated with its chaperone function. Co-chaperones as well as posttranslational modifications (phosphorylation, acetylation, and S-nitrosylation) are important for regulating its ATPase activity. Yeast can be used to express and purify HSP90 and also detect its phosphorylation by pan-phosphoserine or phosphothreonine antibodies.