The Janus (JAK) family of cytoplasmic tyrosine kinases has been implicated in signal transduction induced by cytokines and growth factors, physically associated with ligand-bound receptors. This association that results in tyrosine phosphorylation and activation. JAK1 is approximately 130kD and contains a C-terminal tyrosine kinase domain, an adjacent kinase or kinase-related domain, and five other domains that are highly conserved among JAK family members. Family members such as JAK1, JAK2, and TYK2 are ubiquitous, whereas JAK3 is predominantly expressed in T lymphocytes. Studies with mutant cells that do not express JAK1, JAK2, or TYK2 show that their activation is essential for cellular signaling. JAK family kinases may either phosphorylate each other or be phosphorylated by a yet undescribed tyrosine kinase. Different cytokines can activate via phosphorylation distinct JAK family members. In some cells, the membrane-associated gp130 protein has been implicated in the induction of JAK family phosphorylation, although gp130 itself has no known activity. Human Jak2 (GenBank Accession No. NM_004972), (a.a. 808-end) with N-terminal His tag MW 42.5kD, expressed in an Baculovirus infected Sf9 cell expression system. Specific Activity: 4 U/ug. One unit is defined as the amount of enzyme that will incorporate 1 nmol phosphate to the tyrosine substrate per minute at pH 7.4 and 30C Assay buffer: 50 mM HEPES, pH 7.4, 3 mM MgCl2, 3 mM MnCl2, 1 mM DTT, 3uM Na orthovanadate, 0.5 mM ATP, 30 ug/ml Poly (Glu:Tyr)4:1 substrate, and 0.04ug recombinant JAK2 Application: useful for the study of enzyme kinetics, screening inhibitors, and selectivity profiling. Stability: >6 months at -80 C
