FIGURE 2 Fractions of Tetrahymena macronuclear proteins eluted from an ion-exchange chromatography column were analyzed by SDS-PAGE. Lane numbers (1 to 10) represent fraction numbers; L is the starting extract. Numbers on the left indicate molecular mass in kilodaltons. The p55 protein contains HAT activity and can be visualized in the activity gel both in the initial extract (lane L) and in the column fraction in lane 6 (arrows).