Description
Native human FSH is a glycoprotein produced from pituitary glands. FSH is a heterodimeric hormone consisting of a 92 amino acids alpha subunit and a 111 amino acids beta subunit. The two principal gonadotropins in vertebrates are luteinizing hormone (LH) and follicle-stimulating hormone (FSH), although primates produce a third gonadotropin called chorionic gonadotropin (CG). LH and FSH are heterodimers consisting of two peptide chains, an alpha chain and a beta chain. LH and FSH share nearly identical alpha chains whereas the beta chain provides specificity for receptor interactions. The alpha subunit, common to each protein dimer (well conserved within species, but differing between them), and a unique beta subunit which confers biological specificity. The alpha chains are highly conserved proteins of about 100 amino acid residues which contain ten conserved cysteines all involved in disulfide bonds. Intracellular levels of free alpha subunits are greater than those of the mature glycoprotein, implying tat hormone assembly is limited by the amount of the specific beta subunit, and that synthesis of alpha and beta is independently regulated