The Eph receptors are the largest family of receptor tyrosine kinases. They can be grouped into two subclasses based on sequence homology: the EphA and the EphB receptors. The ligands for the Eph receptors are the ephrins. The EphA receptors bind ephrin-A ligands, which are tethered to the membrane by a GPI linkage, and the EphB receptors bind ephrin-B ligands, which have a membrane spanning region. The Eph receptors are widely expressed during embryonic development, including in the nervous system and the vascular system. Ephrins and Eph receptors have been implicated in many developmental processes including neuronal network formation, guidance of cell migration, and axonal pathfinding. They remain expressed at lower levels in adult tissues and are upregulated in pathological conditions such as cancer. EphB4 is expressed in epithelial cells and in endothelial cells of embryonic veins, where its signaling mediates cell migration and proliferation via the PI3K pathway. It is upregulated in several types of tumors, including mammary tumors, colon cancer, and endometrial cancer. EphB4 has previously been designated Htk, Myk1, Tyro11 and Mdk2. Human EPHB4 ( GenBank Accession No. NM_004444.2), (a.a. 563-987) with N-terminal His tag, MW 50kD, expressed in an Baculovirus infected Sf9 cell expression system. Stability: >6 months at -80C Purity: >90% by SDS-PAGE. Specific Activity: 125 U/ug. One unit is defined as the amount of enzyme that will phosphorylate 1 pmol of tyrosine substarte per minute at pH 7.4 and 30 C Assay buffer: 50 mM HEPES, pH 7.4, 3 mM MgCl2, 3 mM MnCl2, 1 mM DTT, 3uM Na orthovanadate, 0.5 mM ATP, 30 ug/ml Poly (Glu:Tyr)4:1 substrate, and 0.04ug recombinant EPHB4. Application: useful for the study of enzyme kinetics, screening inhibitors, and selectivity profiling.
