Tyrosine kinase of the non-receptor type, involved in the IFN-alpha/beta/gamma signal pathway. Kinase partner for the interleukin (IL)-2 receptor as well as interleukin (IL)-10 receptor. Directly phosphorylates STAT but also activates STAT signaling through the transactivation of other JAK kinases associated with signaling receptors. ATP + L-tyrosyl-[protein] = ADP + H(+) + O-phospho-L-tyrosyl-[protein] Mn(2+) was used in the in vitro kinase assay but Mg(2+) is likely to be the in vivo cofactor. Interacts with IL31RA. Interacts with IFNAR2. Interacts with IFNGR1. Interacts with JAKMIP1. Interacts with SHB. Interacts (via N-terminus) with IL2RB and IL10RA (via its cytoplasmic domain) (By similarity). Interacts with FER (PubMed:12738762). Wholly intracellular, possibly membrane associated. The FERM domain mediates interaction with JAKMIP1. The protein kinase 1 domain is also called the pseudokinase domain and has a regulatory role through the transactivation of other JAK kinases associated with signaling receptors. The protein kinase 2 domain is the catalytically active domain. Ubiquitinated by RNF125; leading to its degradation by the proteasome. Autophosphorylated. Phosphorylated on tyrosine residues in response to interferon gamma signaling. Dephosphorylation of Tyr-1034 and Tyr-1034 by PTPN2 negatively regulates cytokine-mediated signaling. Belongs to the protein kinase superfamily. Tyr protein kinase family. JAK subfamily.