In this study, we characterize fromSaccharomyces cerevisiae: 1) a protein that has immunological similarities to human chorionic gonadotropin (hCG), and 2) a binding site for this hCG-like protein which also binds hCG and human luteinizing hormone (hLH).Saccharomyces cerevisiaechorionic gonadotropin-like protein (ScCGLP) was purified in several steps. This protein when analyzed by SDS-PAGE, under non-denaturing conditions, produced two bands, one at 110-kDa, and another at 57.5-kDa. Under denaturing conditions, only the 57.5-kDa band appeared. This 57.5-kDa band also reacted in a Western blot, using a polyclonal antibody directed against hCG. Purified ScCGLP reacted in the following hCG immunoassays: 1) polyclonal rabbit anti-hCG equilibrium assay, 2) carboxyl-tail hCG equilibrium assay, 3) two equilibrium assays using monoclonal antibodies, and 4) free alpha-chain subunit equilibrium assay using a monoclonal antibody.Characterization of hCG/hLH binding sites inSaccharomyces cerevisiaewas performed, and the ability of the ScCGLP to displace I125-hCG was also shown. Human CG and hLH were able to compete for I125-hCG binding toSaccharomyces cerevisiaeblastospores (Kds of approximately 10-8M), while ScCGLP competed with higher affinity (Kd = 9.41×10-10M).The hCG-like immunoactivity was also present inSaccharomycesgrowth media, as well as in all brands of commercial beer studied.