Recognition of the beta-subunit of human chorionic gonadotropin and sub-determinants by target tissue receptors.

The beta-subunit of human chorionic gonadotropin, purified immunochemically to eliminate undissociated human chorionic gonadotropin, induced testosterone production by mouse Leydig cells at concentrations 400-fold higher than human chorionic gonadotropin. Steroidogenesis was also stimulated by a synthetic fragment of the beta-subunit of human chorionic gonadotropin conforming to the peptide sequence residues 39--71, whereas peptide sequence residues 39--56 and three C-terminal fragments (residues 115--145, 111--145 and 101--145) failed to cause steroidogenesis. These studies suggest the presence in the beta-subunit of human chorionic gonadotropin of determinants recognized by the tissue receptors, a part of these determinants residing between amino acid residues 57--71.