ERBB3, also known as receptor tyrosine-protein kinase erbB-3, is a member of the epidermal growth factor receptor (EGFR/ERBB) family of receptor tyrosine kinases. ErbB3 has been shown to bind the ligands heregulin and NRG-2. Ligand binding causes a change in conformation that allows for dimerization, phosphorylation, and activation of signal transduction. ErbB3 can heterodimerize with any of the other three ErbB family members. The theoretical ErbB3 homodimer would be non-functional because the kinase-impaired protein requires transphosporylation by its binding partner to be active. Recombinant human ERBB3, fused to hIgG-His-tag at C-terminus, was expressed in insect cell and purified by using conventional chromatography techniques.