Ephrin-B1, also known as EFNB1, belongs to the Eph family. Ephrins, which act as ligands for Eph receptors, are cell-surface proteins that fall into two categories, ephrin-A and ephrin-B, based on their structure and function. EFNB1 proteins are transmembrane and have conserved cytoplasmic tyrosine residues that are phosphorylated upon interaction with an EphB receptor.