Expression, purification and crystallization of human tau-protein kinase I/glycogen synthase kinase-3β

Human tau-protein kinase I (TPK-I; also known as glycogen synthase kinase-3β, GSK-3β) is a serine/threonine protein kinase. Full-length TPK-I/GSK-3β was expressed in Escherichia coli as a fusion protein with a 6×His tag at the C-terminus and was crystallized using the hanging-drop vapour-diffusion method. Prismatic crystals of ­dimensions 0.4 × 0.2 × 0.1 mm were obtained using 12–15%(w/v) polyethylene glycol 6000 as a precipitant at 278 K. The crystals belong to the orthorhombic space group P2₁2₁2₁, with unit-cell parameters a = 82.9, b = 86.1, c = 178.1 Å measured at 100 K, diffract to 2.3 Å resolution and seem to contain two enzyme molecules per asymmetric unit.