FIG. 2.

Fractionation of IκBα kinase activity. A schematic of the purification scheme used to purify cellular kinases that phosphorylate the amino terminus of IκBα is shown. S100 extract was obtained from untreated HeLa cells and fractionated on a phosphocellulose column washed with buffer containing 0.1 M KCl and eluted with 0.3 M KCl. This fraction was applied to a Q-Sepharose (Q-seph) column and eluted with 1.0 M KCl, followed by fractionation on a Superdex 200 column. Proteins with kinase activity for the 138 amino-terminal residues of IκBα were then fractionated on heparin agarose, mono Q FPLC, and mono S FPLC and eluted with KCl gradients as indicated. FT, column flowthrough.