Partially deglycosylated human choriogonadotropin, stabilized by intersubunit disulfide bonds, shows full bioactivity.

Several studies indicate that in human choriogonadotropin the N-linked oligosaccharide at position 52 of the alpha-subunit is important for bioactivity. We have generated choriogonadotropin mutants in which the alpha52 glycosylation site is removed and the alpha and beta subunits are covalently linked by intersubunit disulfide bonds. These mutants display wild-type receptor binding and bioactivity. Furthermore, we show that removal of the alpha52 sugar leads to instability of heterodimeric choriogonadotropin. Therefore, we conclude that the alpha52 oligosaccharide of choriogonadotropin is not involved in signal transduction, but in the stability of the heterodimer.