Fe–S clusters, fragile sentinels of the cell

Iron-sulfur (Fe–S) clusters are ubiquitous cofactors present in a myriad of proteins controlling processes as diverse as DNA replication, photosynthesis, respiration and gene regulation. Their assembly and delivery into apo-proteins are catalysed by different multi-protein systems conserved throughout prokaryotes and eukaryotes. Because so many cellular processes are dependent upon Fe–S proteins, alteration of the Fe–S clusters or of the systems that make them has profound impact on cellular physiology. The present review aims at covering and discussing those situations wherein these highly efficient redox sensitive cofactors turn from faithful sentinels into enfeebled assistants or, worse, into dangerous insiders.