Glycoprotein gonadotropins. Structure and synthesis.

The four human glycoprotein hormones FSH, LH, CG and TSH are closely related in structure, each consisting of a common alpha-subunit and a specific beta-subunit. Amino acid sequences have been established by standard methods of protein sequencing and confirmed by base sequencing of the cDNAs encoding for the polypeptide units. Speculation on the structures involved in the binding of subunits and binding to receptors has been based on examination of these sequences for common or similar regions. There are asparagine-linked carbohydrate chains attached to the subunits and in addition O-glycosidically linked carbohydrate chains in beta-CG attached to serine molecules. The carbohydrates are essential for full biological activity. The progress so far and future possibilities for the synthesis of these glycoprotein hormones by the technique of genetic engineering are discussed.