CD34 is a 105-120 kDa, type I monomeric glycophosphoprotein and member of the sialomucin protein family. It is made up of a highly conserved cytoplasmic domain and transmembrane domain that is characterized by a heavily glycosylated N-terminal region and a well conserved C-terminal region. The N-terminal region plays a key role in determining interactions between CD34 with different ligands including E- and L-selectins.