Purification of an estrogen-regulated breast cancer protein by monoclonal antibody affinity chromatography.

An estrogen-regulated cytoplasmic protein has been purified from MCF-7 human breast cancer cells with anion exchange and monoclonal antibody affinity chromatographies. The purified protein has a monomeric mol wt of 28,000 and isoelectric species with pI's between 5.9 and 6.0. Amino acid analysis indicates the protein is acidic, is probably hydrophilic, and contains unusually low amounts of methionine and half cystine. This rapid, two-step procedure produces purified protein in high yield and demonstrates the power of monoclonal antibodies in protein purification.