This gene encodes a member of the RSK (ribosomal S6 kinase) family of serine/threonine kinases. This kinase contains 2 non-identical kinase catalytic domains and phosphorylates several residues of the S6 ribosomal protein. The kinase activity of this protein leads to an increase in protein synthesis and cell proliferation. Amplification of the region of DNA encoding this gene and overexpression of this kinase are seen in some breast cancer cell lines. Alternate translational start sites have been described and alternate transcriptional splice variants have been observed but have not been thoroughly characterized. A truncated, N-terminus His-tagged fusion protein corresponding to aa1-421 of human p70 S6 Kinase (containing a T412E mutation and a D18H mutation) expressed in Sf21 cells. The T412E mutant is more efficiently activated by PDK1 than is the wild type p70 S6 Kinase. Specific Activity: ~200U/mg Unit Definition: One unit of p70 S6 kinase activity is defined as 1nmol phosphate incorporated into 100uM S6 Kinase/Rsk-2 Substrate Peptide 2 (KKRNRTLTK) per minute at 30C with a final ATP concentration of 100uM. Quality Control Testing: MS Tryptic Fingerprint: Confirmed identity as p70 S6 Kinase with 32% amino acid coverage of the translated sequence. Kinase Assay: 8.75-87.50ng phosphorylated 100uM S6 Kinase/Rsk-2 Substrate Peptide 2 in the assay described. Storage and Stability: Aliquot to avoid repeated freezing and thawing and store at -70C. Aliquots are stable for 6 months after receipt. For maximum recovery of product, centrifuge the original vial after thawing and prior to removing the cap.
