Ephrin-B proteins are thought to play key roles in cellular functions as diverse as neuronal migration and blood vessel development (Flanagan and Vancerhaeghen, 1998, Dufour et al., 2003, Oike et al., 2002). Ephrin-B molecules expressed at the membrane surface bind to the EphB family receptors on target cells during cell-to cell contact. This interaction leads to cell signaling in the target cell but also generates a reverse signal in the cell expressing Ephrin-B on its surface. This reverse signaling event is thought to be critical for vessel maturation and neuronal development. Importantly, tyrosine phosphorylation of Ephrin-B is thought to be a critical component of this reverse signaling event (Palmer et al., 2002). Recent work suggests that phosphorylation of a specific Ephrin-B residue (Tyr298) plays a key role in Ephrin-B signaling (Kalo, et al., 2001).Synonyms: CEK5 LIgand, CEK5-L, EFL-3, EFL3, EFNB1, ELK-L, EPH-related receptor tyrosine kinase ligand 2, EPLG2, LERK-2, LERK2