hCG

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.

http://www.chem.gla.ac.uk/research/groups/protein/glyco/GPH.html

The three dimensional crystal structure of hCG has been publish by Wu et al., Lapthorn et al., and Lustbader et al. (1,2,3)

http://wulab.tch.harvard.edu/PDF/Lustbader_hCG.pdf

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