Human chorionic gonadotropin is a glycoprotein composed of 237 amino acids with a molecular mass of 25.7 kDa. It is heterodimeric, with an α (alpha) subunit identical to that of luteinizing hormone (LH), follicle-stimulating hormone (FSH), thyroid-stimulating hormone (TSH), and β (beta) subunit that is unique to hCG. The beta subunits of the glycoprotein hormones are unique and give them their different biological characteristics.
The three dimensional crystal structure of hCG has been publish by Wu et al., Lapthorn et al., and Lustbader et al. (1,2,3)
1 – Lapthorn, A J, Harris, D.C., Littlejohn, A, Lustbader, J W, Canfield, R E, Machin, K J, Morgan, F J, Isaacs, N W: Crystal structure of human chorionic gonadotropin. Nature, 369, 455-461, 1994
2 – H Wu, JW Lustbader, Y Liu, RE Canfield, WA Hendrickson
Structure of human chorionic gonadotropin at 2.6 å resolution from MAD analysis of the selenomethionyl protein. Stucture, 2 (1994), pp. 6545–6558
3 – JW Lustbader, DL Yarmush, S Birken, D Puett, RE Canfield. The application of chemical studies of human chorionic gonadotropin to visualize its three-dimensional structure. Endocr Rev, 14 (1993), pp. 291–311