Fig. 1

Schematic diagram of wild-type and mutant recombinant equine chorionic gonadotropin (rec-eCG). The wild-type and mutant N-linked and O-linked glycosylation sites on eCG. Asn⁵⁶ of the eCG α-subunit was replaced with Gln or the carboxyl-terminal peptide (CTP) region of O-linked oligosaccharides in the eCG β-subunit was deleted using polymerase chain reaction. The circles “N,” “X,” and “O-linked” denote N-linked oligosaccharide, non-glycosylated sites, and O-linked oligosaccharide at the eCG β-subunit, respectively. The four expression vectors were constructed (plasmids encoding eCGβ/α-wt and mutants designated as pcDNA3-eCGβ/α, pcDNA-eCGβ/αΔ56, pcDNA-eCGβ-D/α, and pcDNA3-eCGβ-D/αΔ56. eCGβ-D/αΔ56 implies a double mutant with substitution of Asn⁵⁶ of eCG α-subunit and deletion at the CTP region of the eCG β-subunit. The epitope myc-tags was inserted between the first and second amino acid residues of the β-subunit of the mature eCG protein