Further characterization of the ovine lutropin alpha and beta subunits prepared by the salt precipitation method.

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 alpha subunit. The subunits possessed low activity. The alpha and beta 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 alpha subunit could be completely reduced and reoxidized in the absence of denaturants. The reoxidized alpha subunit combines with the native beta subunit generating full activity. However, this recombined hormone tends to lose activity with time, suggesting that the reoxidation may not fully restore the native structur of the reduced alpha subunit. The native lutropin alpha subunit effectively combined with follitropin beta subunit generating complete follitropin activity.