The expression of ferritin involved in iron metabolism is regulated at the translational level by the interaction of iron regulatory protein with iron-responsive element(IRE) in the 5`-untranslated region of ferritin transcript. To identify the role of structural element utilized for translational regulation of ferritin, we studied the effects of mutations in the ferritin IRE by measuring IRP binding activity and translational activity. Our data suggest that the cytosine at bulged position of IRE within ferritin is important for the formation of RNA secondary structure involved in translational regulation.