Figure 2.

Immunoblot analysis of ATP sulfurylase and APS reductase in leaves of Arabidopsis during growth. Representative samples from the experiments shown in Figure 1 were analyzed by immunoblotting. For the ATP sulfurylase blot, 5 μg of total protein was loaded, whereas 15 μg was loaded for APS reductase. The relative enzyme activity loaded onto the gel is indicated below the blot with the lowest activity normalized to a value of 1. For ATP sulfurylase the absolute activity corresponding to the relative value of 1 was 32 nmol min⁻¹ mg⁻¹, whereas for APS reductase it was 0.45 nmol min⁻¹ mg⁻¹. The relative activity values correspond closely with the signal intensity determined by densitometry.