EphB4, also known as Htk, Myk1, Tyro11, and Mdk2, is a member of the Eph receptor family, which binds of the ephrin ligand family. Two classes of receptors exist, designated A and B, that have an extracellular domain made up of a globular domain, a cysteine-rich domain, and two fibronectin type III domains, followed by the transmembrane region and cytoplasmic region. The cytoplasmic region contains juxtamembrane motif with two tyrosines, which are the major autophosphorylation sites, along with a kinase domain, and a conserved sterile alpha motif (SAM) in the carboxyl terminus, which includes one conserved tyrosine. Ligand recognition and binding leads to activation of intrinsic kinase activity.