Demonstration by radioligand-binding assay of the structural similarity of a partially synthetic growth hormone recombinant molecule to its natural analog and to native human growth hormone.

The recombinant resulting from the noncovalent interaction of a natural amino-terminal fragment of reduced and carbamoylmethylated human GH (residues 1-134) with a synthetic carboxyl-terminal fragment of reduced and carbamoyl-methylated human GH (residues 141-191) reacts in seven immunoassay systems and two receptor assay systems in a similar manner and with comparable potency to its naturally occurring analog, but with less avidity overall than does the native hormone. This similarity of reactivity is strong evidence for similarity of conformation among these molecules. The demonstration that a synthetic fragment can restore radioligand-binding properties to a proteolytic fragment of human GH implies that partially synthetic variant GH molecules have biological activity.