ErbB3/Her3 Fc Chimera Protein, Human

Human Epidermal Growth Factor Receptor 3 (HER3/ErbB3) is a distinctive member of the epidermal growth factor receptor (EGFR/ErbB) family, which plays a central role in cell proliferation, differentiation, migration, and survival. Its most prominent feature is that its intracellular kinase domain exhibits extremely low, if not absent, catalytic activity compared to other family members (EGFR, HER2, HER4). Consequently, HER3 cannot signal alone and must heterodimerize with other active family members (primarily HER2) to be activated and initiate downstream signaling pathways.

Structurally, HER3, like other ErbB family members, consists of an extracellular ligand-binding domain, a single transmembrane helix, and an intracellular domain containing the kinase domain. Its extracellular domain specifically binds to ligands such as Neuregulin (NRG), triggering a conformational change that exposes its dimerization arm, enabling it to bind to EGFR or HER2.