Hsp104 is a molecular chaperone required for stress tolerance and for maintenance of [psi(+)] prions in the budding yeast Saccharomyces cerevisiae. Hsp104 can protect yeast cells against high temperature and high concentration of ethanol but mutation studies have shown this protein is not required for normal growth. Hsp104 was cloned into an E. coli expression vector and was purified to apparent homogeneity by using conventional column chromatography techniques.