Jun Kinases (JNK), also called stress-activated protein (SAP) kinases, are proline-directed, serine/threonine-specific kinases that require phosphorylation on tyrosine for phosphotransferase activity. JNK was originally shown to phosphorylate microtubule-associated protein-2, but c-Jun and ATF2 appears to be an important physiological target of this kinase. Phosphorylation of Thr69 and Thr71 of ATF2 by JNK is important for the transcriptional activity of ATF2. cDNA cloning studies with rat and human libraries have shown that there are several isoforms of the JNK family. Many stimuli activate JNK including heat shock, hyperosmotic shock, UV irradiation, exposure to protein synthesis inhibitors such as cycloheximide and anisomycin, and treatment with proinflammatory cytokines such as tumor necrosis factor-a. Recombinant full-length protein corresponding to human JNK2a2/SAPK1a with an N-terminal 6X His-tag, expressed in Sf21 cells. JNK2a2/SAPK1a Kinase Assay: 2mg of unactive JNK2a2/SAPK1a was incubated with MKK7/SKK4. Activation of JNK2a2/SAPK1a was assessed by phosphorylation of ATF2 substrate. Specific Activity: 80u/mg when maximally activated. Unit Definition: One unit of JNK2a2/SAPK1a activity is defined as 1nmol phosphate incorporated into GST-ATF2 per minute. Storage and Stability: May be stored at 4C for short-term only. Aliquot to avoid repeated freezing and thawing. Store at -20C. Aliquots are stable for 6 months after receipt at -20C. For maximum recovery of product, centrifuge the original vial after thawing and prior to removing the cap. Further dilutions can be made in assay buffer.
