Involved in iron-sulfur (Fe-S) cluster assembly (PubMed:16603772, PubMed:19305405, PubMed:21799759, PubMed:25430730). May act as a regulator of Fe-S biogenesis (PubMed:19305405, PubMed:21799759, PubMed:25430730). Can bind both Fe(2+) and Fe(3+) ions (PubMed:15530368, PubMed:16603772, PubMed:17244611, PubMed:17651435). In vivo, has a positive effect on Fe-S cluster biogenesis under iron-rich growth conditions (PubMed:25430730). In vitro, can inhibit IscS cysteine desulfurase activity and the formation of Fe-S clusters on IscU (PubMed:19305405, PubMed:21799759). In vitro, in the presence of IscS and cysteine, Fe(3+)-CyaY can be used as an iron donor during Fe-S cluster assembly on the scaffold protein IscU (PubMed:16603772). Binds iron under oxidative stress conditions, but not under conditions emulating the intracellular redox potential. Monomer (PubMed:16603772, PubMed:19305405, PubMed:28931050). Forms homodimers and higher oligomers in the presence of iron (PubMed:16603772, PubMed:28931050). Interacts with IscS (PubMed:16603772, PubMed:19305405, PubMed:25430730). Cells are not affected in cellular iron content and sensitivity to oxidants. Belongs to the frataxin family.