EphB1, previously known as Elk (eph like kinase), is a receptor tyrosine kinase of the highly tissue restricted family of eph proteins. EphB1 and other ephB family members are type 1 membrane spanning proteins, comprised of immunoglobulin, fibronectin type III, and cysteine rich subdomains in the ecto domain, and the single uninterrupted cytoplasmic tyrosine kinase domain upstream of a carboxyterminal sterile alpha motif (SAM) domain. EphB family proteins bind ephrins of the B class. EphB1 is expressed predominately in developing neural structures in embryos, and in vascular epithelium of kidney, and other tissues. Upon binding to alternatively oligomerized ephrin B1, EphB1 signals regulation of cell attachment and cell to cell assembly. Members of this protein family are implicated in neuronal and vascular cell targeting.