Define Iron Response Element and Iron Regulatory Protein?

The Iron Response Element (IRE) and the Iron Regulatory Protein (IRP) play key roles in co-ordinating regulation of iron uptake, storage and utilization. The IRE has specific sequences in the 5' un translated region of L and H chain ferritin rn RNAs. These sequences are conserved in evolution and form a specific RNA stein loop structure. The IRE interacts at high affinity with a cytoplasmic protein known as Iron Regulatory Protein. When the IRE is situated sufficiently close to the cap site and before the st M codon, binding of IRP prevents ribosome attachment and thereby inhibits translation initiation. The IRE binding activity of IRP varies as a function of iron availability: it increases after iron chelation, but decreases when iron supply is plentiful. As a result of the IRE-IRP interaction and the inhibition of fenitin synthesis, iron storage diminishes in iron-deprived cells. In contrast, cells with a high iron supply synthesize and store iron normally.

In addition, transferring receptor mRNA is regulated by IRP, but in the reverse. Here, iron deprivation increases the stability of transfemn receptor m RNA, whereas an abundance of iron has a destabilizing effect. Cells respond to natural fluctuations in iron metabolism by modulation of the IRPs. The co-ordinate opposite control of iron storage and uptake has physiologically a Cumulative effect. While iron deprivation is compensated by higher iron uptake and Less storage, iron overload is re-equilibrated by opposite effects. An individual's iron Status triggers a feedback control on ferritin and transferring receptor levels.