Purified (~70-90%). ERK1 is a protein serine/threonine kinase that is a member of the extracellular signal-regulated kinases (ERKs) which are activated in response to numerous growth factors and cytokines. Activation of ERK1 requires both tyrosine and threonine phosphorylation that is mediated by MEK. ERK1 is ubiquitously distributed in tissues with the highest expression in heart, brain and spinal cord. Activated ERK1 translocates into the nucleus where it phosphorylates various transcription factors (e.g., Elk-1, c-Myc, c-Jun, c-Fos, and C/EBP beta). Source: Recombinant protein corresponding to human ERK1, expressed in Insect cells. Molecular Weight: ~44kD Specific Activity: 380nmol/min/mg as per activity assay protocol. Endotoxin: <1EU/ug (LAL)