The larger molecular mass proteins may represent a 2:1 combination of two inhibin molecules to one FS. Proteins of 133 kDa and > 220 kDa may be multimers of the 66-kDa or 97-kDa complexes. When radiolabeled activin was crosslinked to FS, 66-kDa, 97-kDa, and larger molecular mass bands were detected by autoradiography. When rh-activin A and FS were combined and cross-linked in molar combinations, a 97-kDa product was detected predominantly when the ratio of FS to activin was 2:1 (Fig. 1C) after SDS-PAGE and silver staining. buy flovent inhaler
This result is consistent with an association of two FS molecules with one activin A protein (one FS per (3A subunit). Lastly, FS and activin or inhibin complexes were not retained in complex form when the proteins were analyzed by SDS-PAGE under reducing or nonreducing conditions if the complexes were not first cross-linked (not pictured). To confirm this assignment, a cocktail of monoclonal antibodies (6FS7, 7FS30) specific for FS detected 66-kDa bands and 97-kDa bands in FS-activin samples (Fig. 1C). Analysis of the recombinant complexes using antibodies against the inhibin or activin subunits was not very successful, suggesting that epitopes for these molecules are partially or completely masked when the proteins are associated with FS.