This receptor binds insulin-like growth factor 1 (IGF1) with a high affinity and IGF2 with a lower affinity. It has a tyrosine-protein kinase activity, which is necessary for the activation of the IGF1-stimulated downstream signaling cascade. Plays a role in oocyte maturation. Promotes head development by inhibiting Wnt signaling during embryogenesis. ATP + L-tyrosyl-[protein] = ADP + H(+) + O-phospho-L-tyrosyl-[protein] Autophosphorylation activates the kinase activity. Tetramer of 2 alpha and 2 beta chains linked by disulfide bonds. The alpha chains contribute to the formation of the ligand-binding domain, while the beta chain carries the kinase domain (By similarity). Expressed at the oocyte surface. Expressed both maternally and zygotically. Shows biphasic expression during early development. Expressed ubiquitously in fertilized eggs and throughout the midblastula transition. Expression then decreases at mid-gastrulation. Shortly after gastrulation, expression is seen throughout the dorsal side of the embryo with expression strongest in the anterior and absent ventrally. Expression increases along the dorsal midline at early neurulation and is seen in the head region as neurulation progresses, particularly in the area of the cement gland primordium. Also present in the anterior mesoderm but is absent from the neural tube and the most ventral part of the embryo. Remains expressed throughout early embryogenesis. By the tailbud stages, expression is anterior, in the head and the most rostral part of the neural tube. The cytoplasmic domain of the beta subunit is autophosphorylated on Tyr residues in response to low concentrations of insulin-like growth factor (IGF 1) and higher concentrations of insulin. Belongs to the protein kinase superfamily. Tyr protein kinase family. Insulin receptor subfamily.