Figure 1

Schematic depiction of the molecular structures of the cystine knot growth factor hCG and of hCG-variants. hCG consists of an α-subunit (hCGα) with 92 amino acids (aa) in length non-covalently linked to the hCGβ-subunit (145 aa). Nicked hCG (hCGn) and nicked hCGβ (hCGβn) contain nicks in the region of aa hCGβ44-48 and rarely around aa 77 of hCGβ. The most important metabolic product of hCG is the hCGβ core fragment (hCGβcf), which is composed of two peptides encompassing aa hCGβ6-40 and 55 to 92 covalently linked. The hCG-unique carboxyl-terminal peptide (CTP) is clipped and truncated hCG and hCGβ variants are generated (-CTPhCG and -CTPhCGβ). There are a multitude of glycosylation variants involving both N-glycosylated (hCGα aa 52 & 78, hCGβ aa 13 & 30) and O-glycosylated carbohydrate antennae (hCGβ aa Ser 121, 127, 132, 138) [41, 42].