Trop2 is about 46-kDa, single pass glycoprotein that was first described as a surface marker for human trophoblast cells. Trop2 is composed of 323 amino acids and contains a 248 amino acid extracellular domain, a hydrophobic transmembrane domain, and a short cytoplasmic tail. The extracellular domain of Trop2 is composed of GA733 type-1 and thyroglobulin type-1A motifs, both of which are also identifiable in Trop2 homolog, Trop-1/EpCAM (epithelial cell adhesion molecule) . The intron-less TACSTD2 (Trop2 gene) is located on chromosome 1p32. The 35 kDa de-glycosylated Trop2 polypeptide can undergo post-translational, N-linked glycosylation. The cytoplasmic domain of Trop2, which is 26-amino acids in length, contains a phosphatidyl-inositol 4,5-bisphosphate binding site (PIP2) and can be phosphorylated by protein kinase C (PKC) at the serine 303 position). This phosphorylation site enables Trop2 to act as a Ca2+ signal transducer . Trop2-induced Ca2+ delivery has been associated with cell cycle propagation through mitogen-activated protein kinase signaling cascade (MAPK).