Probable receptor tyrosine kinase. During postembryonic development, involved in the initiation of metamorphosis probably by inducing the production of ecdysone in response to prothoracicotropic hormone (PTTH) (By similarity). Binding to PTTH stimulates activation of canonical MAPK signaling leading to ERK phosphorylation (PubMed:19965758, PubMed:26928300). ATP + L-tyrosyl-[protein] = ADP + H(+) + O-phospho-L-tyrosyl-[protein] Homodimer; disulfide-linked. Expressed in the prothoracic gland in 4th and 5th instar stage larvae, and P0 stage pupae. Also detected at lower level in testes and ovaries of 5th instar larvae. Contains 3 very unusual FN3 domains in the extracellular domain. The second FN3 domain is involved in the binding to PTTH dimer. May be auto-phosphorylated on tyrosine residues. At least one of the 3 cysteine residues Cys-381, Cys-393 or Cys-394 is involved in the formation of interchain disulfide bonds. The disulfide bond sites in the extracellular region are not involved in homodimer formation. Belongs to the protein kinase superfamily. Tyr protein kinase family.