IRP1, or Iron Regulatory Protein 1, is a key protein involved in the regulation of iron homeostasis in cells. It plays a crucial role in sensing cellular iron levels and controlling the expression of genes related to iron metabolism. When iron levels are low, IRP1 binds to specific RNA sequences called iron-responsive elements (IREs) in target mRNAs, stabilizing them and promoting the production of proteins that help import iron into the cell. In contrast, when iron levels are sufficient, IRP1 undergoes a conformational change and loses its ability to bind to IREs. This results in the degradation of mRNAs that encode proteins involved in iron uptake, thereby preventing excess iron accumulation. Overall, IRP1 is essential for maintaining the balance of iron in the body, which is vital for various biological processes.