Catalytic domain of the Serine/Threonine Kinase, c-Jun N-terminal Kinase 2STKs catalyze the transfer of the gamma-phosphoryl group from ATP to serine/threonine residues on protein substrates. JNK2 is expressed in every cell and tissue type. It is specifically translocated to the mitochondria during dopaminergic cell death. Specific substrates include the microtubule-associated proteins DCX and Tau, as well as TIF-IA which is involved in ribosomal RNA synthesis regulation. Mice deficient in Jnk2 show protection against arthritis, type 1 diabetes, atherosclerosis, abdominal aortic aneurysm, cardiac cell death, TNF-induced liver damage, and tumor growth, indicating that JNK2 may play roles in the pathogenesis of these diseases. Initially it was thought that JNK1 and JNK2 were functionally redundant as mice deficient in either genes could survive but disruption of both genes resulted in lethality. However, recent studies have shown that JNK1 and JNK2 perform distinct functions through specific binding partners and substrates. JNKs are mitogen-activated protein kinases (MAPKs) that are involved in many stress-activated responses including those during inflammation, neurodegeneration, apoptosis, and persistent pain sensitization, among others. The JNK2 subfamily is part of a larger superfamily that includes the catalytic domains of other STKs, protein tyrosine kinases, RIO kinases, aminoglycoside phosphotransferase, choline kinase, and phosphoinositide 3-kinase.