Fig. 3. Affinity purification of p68 on streptavidin-coated magnetic beads with biotinylated MiSat fragment. The fractions were subjected to 12% (A) or 10% (B) SDS-PAGE and stained with Coomassie Blue. (A) Lane 2, NM proteins; lane 3, NM proteins washed from the beads by 0.5 M NaCl in GMSA buffer; lane 4, proteins washed from the beads by boiling in SDS-PAGE sample buffer. (B) Influence of competitor DNA (MiSat, lane 3; pUC19, lane 4) on the eluate composition. The probes in lane 4 contained 50-fold excess of pUC19, in lane 3, 10-fold weight excess of MiSat containing p238 as competitor DNA when loaded into affinity column. The nuclear matrix extract loaded is shown in lane 2. P68 and lamin B (L) bands are indicated. The binding activity of fractions in GMSA is indicated at the top. Size markers are shown in lane 1 of panels A and B.