Involved in the development. Negatively regulates tyrosine phosphorylation and activation state of dstC/STATc, probably by activating a dstC/STATc phosphatase. ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] ATP + L-tyrosyl-[protein] = ADP + H(+) + O-phospho-L-tyrosyl-[protein] Expression is initially low during the vegetative stage, but increases after 5 and 15 hours of development. Up-regulation of the expression at the postaggregative stages is observed. The truncated N-terminal protein kinase domain lacks most of its classical characteristics and in vitro, has no activity. The protein kinase domain 1 is predicted to be catalytically inactive. C-terminal tyrosine kinase domain is capable of autophosphorylation, in vitro. Belongs to the protein kinase superfamily. TKL Tyr protein kinase family.