The ErbB3 gene encodes a member of the epidermal growth factor receptor (EGFR) family of receptor tyrosine kinases. ErbB3 is a membrane-bound protein which has a neuregulin binding domain but not an active kinase domain. It can therefore bind this ligand but cannot convey a signal into the cell via protein phosphorylation. However it does form heterodimers with other EGF receptor family members which do have kinase activity. Heterodimerization leads to the activation of pathways which lead to c