Figure 6. Purification of the the 40 kDa protein. Panel A represents a salt elution of the ~40 kDa protein from Heparin-sepharose as described by Baldridge and Fallon (1996). Values at top represent KCl concentrations. A southwestern blot is shown. Panel B shows enrichment of the 40 kDa protein by size fractionation and analysis by southwestern blotting. All lanes contain ~10 µg nuclear protein. Lane 1 is total nuclear protein; lane 2 shows protein that passed through a 50kDa filter; lane 3 shows nuclear proteins that passed through a 30 kDa filter, and lane 4 contains proteins between 30-50 kDa. Panel C. SDS-PAGE of the nuclear lysate (starting material, lane 1) and purified protein from Panel B, lane 4 (lane 2). The gel was stained with Coomassie blue.