Tyrosine kinase of the non-receptor type, phosphorylates the marelle protein. Required maternally for the establishment of the normal array of embryonic segments: involved in the control of pair-rule gene transcription in a stripe-specific manner. Together with Hsp83 and piwi, mediates canalization, also known as developmental robustness, likely via epigenetic silencing of existing genetic variants and suppression of transposon-induced new genetic variation. ATP + L-tyrosyl-[protein] = ADP + H(+) + O-phospho-L-tyrosyl-[protein] Forms a complex with Hsp83 and piwi; probably Hop mediates the interaction between piwi and Hsp83. Wholly intracellular, possibly membrane associated. Expressed both maternally and zygotically throughout development. Possesses two phosphotransferase domains. The second one probably contains the catalytic domain (By similarity), while the presence of slight differences suggest a different role for domain 1 (By similarity). Belongs to the protein kinase superfamily. Tyr protein kinase family. JAK subfamily.