Human somatotropin: restoration of full biological activity by noncovalent interaction of a natural and a synthetic fragment of the hormone.

The recombinant hormone obtained by noncovalent interaction of the natural NH2-terminal fragment (consisting of 134 amino acid residues) with a synthetic COOH-terminal fragment of 52 amino acids of the reduced-carbamidomethylated human somatotropin molecule is found to exhibit full biological activity of the native hormone as evidenced by the tibia test. Radioimmunoassay data indicate that the semisynthetic recombinant hormone possesses essentially full immunoreactivity as compared to the native one. In addition, circular dichroism and fluorescence emission spectra of the semisynthetic recombinant are identical to that of the undisociated, plasmin modified, reduced-carbamidomethylated hormone.