Absence of the COOH-terminal peptide on ectopic human chorionic gonadotropin beta-subunit (hCG beta).

A comparison of the physical properties and immunoreactivity of ectopic hCG beta from cultured cervical cancer cells and standard hCG beta was performed. The heterogeneity of the preparations was examined by ion-exchange chromatography, and the molecular size by analytical gel filtration. Two distinct forms of ectopic hCG beta were identified. One form was indistinguishable from standard hCG beta, while the other, although larger, lacked the characteristic COOH-terminal peptide (CTP). This was shown by the failure of antisera specific for determinants on the cTP to recognize this molecule, and by the apparent absence of the 0-linked oligosaccharides and thermolysin cleavage site normally found in this region.