Production of recombinant eCG with potent FSH-like activity by site- directed mutagenesis

Equine chorionic gonadotropin (eCG) and luteinizing hormone (eLH) are encoded by a single gene and have identical peptide portions. They, however, differ in the structures of their attached oligosaccharides, which depend on the sites of their production. Recombinant eCG/LH (rec-eCG/LH) possesses dual LH and FSH activities. Mutant eCG/LH in which Asn 56 of the α-subunit was changed to Gln to remove the N-linked oligosaccharide showed complete loss of LH activity, whereas in contrast its FSH activity was more potent than that of the wild-type. Another mutant, which lacked the carboxyterminal portion of the β-subunit to which O-linked oligosaccharides are attached, showed LH activity similar to that of the wild-type, whereas it had the most potent FSH activity. Thus, the oligosaccharides attached to eCG/LH play differential roles in the expression of biological activity.