Probable receptor tyrosine kinase which is required for determination of anterior and posterior terminal structures in the embryo (PubMed:2927509, PubMed:8423783). During postembryonic development, involved in the initiation of metamorphosis probably by inducing the production of ecdysone in response to prothoracicotropic hormone Ptth (PubMed:19965758). Binding to Ptth stimulates activation of canonical MAPK signaling leading to ERK phosphorylation (By similarity). ATP + L-tyrosyl-[protein] = ADP + H(+) + O-phospho-L-tyrosyl-[protein] Expressed both maternally and zygotically. Expressed throughout the embryo but is activated specifically at the poles (PubMed:2927509, PubMed:8423783, PubMed:19965758). Expressed in the prothoracic gland in wandering L3 larvae (PubMed:19965758). May be auto-phosphorylated on tyrosine residues. RNAi-mediated knockdown in the prothoracic gland (PG) delays the onset of pupariation by prolonging the L3 larval stage. In addition, pupal size and, to a lesser extent, PG cell size are increased. Belongs to the protein kinase superfamily. Tyr protein kinase family.