Conversion of Human Choriogonadotropin into a Follitropin by Protein Engineering

• Published in: Proceedings of the National Academy of Sciences - PNAS 1991-02, Vol.88 (3), p.760-764
• Main Authors: Campbell, Robert K., Dean-Emig, Diana M., Moyle, William R.
• Format: Article
• Language: English
• Subjects: 550201 - Biochemistry- Tracer Techniques; AMINO ACID SEQUENCE; Amino acids; Analytical, structural and metabolic biochemistry; ANDROGENS; ANDROSTANES; Animals; ANTIBODIES; BASIC BIOLOGICAL SCIENCES; BETA DECAY RADIOISOTOPES; Biochemistry; Biological and medical sciences; BIOTECHNOLOGY; CELL CONSTITUENTS; Cell Line; Chimeras; Chorionic Gonadotropin - genetics; Chorionic Gonadotropin - metabolism; Chorionic Gonadotropin - pharmacology; Corpus Luteum - metabolism; DAYS LIVING RADIOISOTOPES; DOSE-RESPONSE RELATIONSHIPS; ELECTRON CAPTURE RADIOISOTOPES; Female; Follicle Stimulating Hormone - genetics; Follicle Stimulating Hormone - metabolism; Follicle Stimulating Hormone - pharmacology; follitropin; FSH; Fundamental and applied biological sciences. Psychology; GENETIC ENGINEERING; Genetic Engineering - methods; GONADOTROPINS; Granulosa cells; HORMONES; Humans; HYDROXY COMPOUNDS; IMMUNOLOGY; INTERMEDIATE MASS NUCLEI; INTERNAL CONVERSION RADIOISOTOPES; IODINE 125; IODINE ISOTOPES; ISOTOPES; KETONES; Kinetics; Leydig Cells - drug effects; Leydig Cells - metabolism; Male; Molecular Sequence Data; MOLECULAR STRUCTURE; MONOCLONAL ANTIBODIES; Mutagenesis, Insertional; NUCLEI; ODD-EVEN NUCLEI; ORGANIC COMPOUNDS; PEPTIDE HORMONES; PITUITARY HORMONES; PLASMIDS; Protein hormones. Growth factors. Cytokines; PROTEINS; RADIOISOTOPES; Rats; Receptors; Receptors, LH - drug effects; Receptors, LH - metabolism; Recombinant Proteins - metabolism; Recombinant Proteins - pharmacology; REPRODUCTION; Sandwiches; Sequence Homology, Nucleic Acid; Sex hormones; STEROID HORMONES; STEROIDS; TESTOSTERONE; Testosterone - biosynthesis; Transfection
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.88.3.760

Human reproduction is dependent upon the actions of follicle-stimulating hormone (hFSH), luteinizing hormone (hLH), and chorionic gonadotropin (hCG). While the α subunits of these heterodimeric proteins can be interchanged without effect on receptor-binding specificity, their β subunits differ and direct hormone binding to either LH/CG or FSH receptors. Previous studies employing chemical modifications of the hormones, monoclonal antibodies, or synthetic peptides have implicated hCG β-subunit residues between Cys-38 and Cys-57 and corresponding regions of hLHβ and hFSHβ in receptor recognition and activation. Since the β subunits of hCG or hLH and hFSH exhibit very little sequence similarity in this region, we postulated that these residues might contribute to hormone specificity. To test this hypothesis we constructed chimeric hCG/hFSH β subunits, coexpressed them with the human α subunit, and examined their ability to interact with LH and FSH receptors and hormone-specific monoclonal antibodies. Surprisingly, substitution of hFSHβ residues 33-52 for hCGβ residues 39-58 had no effect on receptor binding or stimulation. However, substitution of hFSHβ residues 88-108 in place of the carboxyl terminus of hCGβ (residues 94-145) resulted in a hormone analog identical to hFSH in its ability to bind and stimulate FSH receptors. The altered binding specificity displayed by this analog is not attributable solely to the replacement of hCGβ residues 108-145 or substitution of residues in the "determinant loop" located between hCGβ residues 93 and 100.