Fig. 8. The tethering factor behaves as a high molecular weight complex. (A) The anion exchange fraction enriched in tethering activity elutes predominantly as a single peak at the void volume of a size exclusion column (Sephacryl S-300). This fraction, and none of the others, has tethering activity. Gel electrophoretic analysis of the peak fraction with tethering activity is also shown in this panel. The complex of proteins purified as described above is present in this fraction. (B) Non-denaturing gel electrophoresis of equal amounts (20 µg) of protein from a KI wash (KI wash) and from the anion-exchange-enriched fraction (TF). A high molecular weight species of 670 kDa is evident in both samples, but more prominent in the highly active anion exchange fraction. PS, protein standard markers.