FURTHER CHARACTERIZATION OF THE OVINE LUTROPIN α AND β SUBUNITS PREPARED BY THE SALT PRECIPITATION METHOD

Abstract

The subunits of ovine lutropin prepared by acid dissociation and salt precipitation were characterized by end group analysis, tryptic peptide mapping, SDS gel electrophoresis and biological activity. No evidence of internal peptide cleavage was found in the α subunit. The subunits possessed low activity. The α and β subunits recombined effectively to generate a complex that had full receptor binding activity and in vitro biological activity. The recombinants of subunits prepared by countercurrent distribution showed only 50% activity in both assays. The salt precipitation method α subunit could be completely reduced and reoxidized in the absence of denaturants. The reoxidized α subunit combines with the native β subunit generating full activity. However, this recombined hormone tends to lose activity with time, suggesting that the reoxidation may not fully restore the native structure of the reduced α subunit. The native lutropin α subunit effectively combined with follitropin β subunit generating complete follitropin activity.