Her 3

ErbB3 (Her-3) is a member of the EGFR family of receptor tyrosine-kinases. However, despite the namesake of the protein family to which it belongs, ErbB3 does not have kinase activity. Rather, it is thought that ErbB3, when activated, becomes a substrate for dimerization and subsequent phosphorylation by ErbB1, ErbB2 and ErbB4.

Like many of the receptor tyrosine-kinases, ErbB3 is activated by extracellular ligand. Ligands known to bind to ErbB3 include heregulin.