Low-M(r) iron isolated from guinea pig reticulocytes as AMP-Fe and ATP-Fe complexes

Guinea pig reticulocytes were pulse-labelled with ⁵⁹Fe bound to transferrin. Haemolysates prepared from these reticulocytes were subjected to rapid (NH₄)₂SO₄ precipitation and then chromatography on an anion-exchange resin. ATP-bound ⁵⁹Fe was the dominant species in the reticulocyte cytosol; 2,3-bisphosphoglycerate and GTP iron complexes were not detected despite the fact that these were stable with (NH₄)₂SO₄ precipitation and readily detected with anion-exchange chromatography. AMP-bound Fe was a minor component of the cytosol following rapid (NH₄)₂SO₄ precipitation, and the major component when iron was released from transferrin by haemolysates. We speculate that ATP-Fe may be degraded in the cell to permit utilization of its iron for haem synthesis.