Purity ~95% (SDS-PAGE). EphA3, also known as Cek4, Mek4, Hek, Tyro4, and Hek4, is a 135kD glycosylated member of the transmembrane Eph receptor tyrosine kinase family. The A and B classes of Eph proteins are distinguished by Ephrin ligand binding preference but have a common structural organization. EphA3 preferentially binds to Ephrin-A5. Eph-Ephrin interactions are widely involved in the regulation of cell migration, tissue morphogenesis, and cancer progression (1, 2). The 521aa extracellular domain (ECD) of human EphA3 contains an N-terminal Ephrin binding region, a cysteine-rich region, and two fibronectin type II domains. The 418 aa cytoplasmic domain contains the tyrosine kinase domain and a sterile alpha motif (SAM) (3, 4). Within the ECD, human EphA3 shares 96% aa sequence identity with mouse and rat EphA3. Alternate splicing generates a secreted isoform that consists of nearly the entire ECD. EphA3 is expressed in the developing forebrain, retinal axons, some spinal cord motor