Electromobility shift analysis of IsaB. A. Purified recombinant IsaB was analyzed by EMSA assay using a fluorescently labeled RNA probe. IsaB shifted the RNA probe in a concentration dependent manner. A. Lane 1, RNA probe alone Lane 2, RNA probe + 3.84 nmol of IsaB, Lane 3, RNA probe + 1.92 nmol of IsaB, Lane 4, RNA probe + 960 pmol of IsaB, Lane 5, RNA probe + 480 pmol of IsaB, Lane 6, RNA probe + 240 pmol of IsaB. At the highest concentrations of IsaB, the RNA probe appeared to aggregate within the wells, while at lower concentrations of IsaB (lanes 4–6) a fraction of the RNA shifted (arrow) but some RNA still remained in the wells. B. Effect of salmon sperm DNA on shift; 480 pmol IsaB and 270 pmol labeled. RNA were added to each reaction. Lane 1, RNA probe alone, Lane 2, IsaB, + RNA probe, Lane 3, IsaB + RNA probe and 1.35 nmol unlabeled DNA, Lane 4, IsaB + RNA and 135 pmol unlabeled DNA, Lane 5, IsaB + RNA and 13.5 pmol unlabeled DNA, Lane 6, IsaB + RNA and 1.35 pmol unlabeled DNA.