Janus kinase

Janus kinase (JAK) is a family of intracellular, nonreceptor tyrosine kinases that transduce cytokine-mediated signals via the JAK-STAT pathway. They were initially named 'just another kinase' 1 and 2 (since they were just two of a large number of discoveries in a PCR-based screen of kinases), but were ultimately published as 'Janus kinase'. The name is taken from the two-faced Roman god of beginnings, endings and duality, Janus, because the JAKs possess two near-identical phosphate-transferring domains. One domain exhibits the kinase activity, while the other negatively regulates the kinase activity of the first. Janus kinase (JAK) is a family of intracellular, nonreceptor tyrosine kinases that transduce cytokine-mediated signals via the JAK-STAT pathway. They were initially named 'just another kinase' 1 and 2 (since they were just two of a large number of discoveries in a PCR-based screen of kinases), but were ultimately published as 'Janus kinase'. The name is taken from the two-faced Roman god of beginnings, endings and duality, Janus, because the JAKs possess two near-identical phosphate-transferring domains. One domain exhibits the kinase activity, while the other negatively regulates the kinase activity of the first.