Crystallization and preliminary X-ray studies of extracellular signal-regulated kinase-2/MAP kinase with an incorporated His-tag

The extracellular signal-regulated kinase ERK2, a member of the protein kinase superfamily, phosphorylates a variety of cellular proteins in response to extracellular signals. ERK2 expressed in Escherichia coli as a fusion protein with the sequence Ala-His₆ at the N terminus has low basal activity and very low levels of phosphate incorporation, but can be fully activated. The Ala-His₆ ERK2 as expressed in the unphosphorylated form has been crystallized in space group P2₁. The cell constants are a=49.32 Å, b=71.42 Å, c=61.25 Å, and β=109.75°, and the crystals diffract to better than 1.8 Å resolution.