Intracellular iron-binding macromolecules in HeLa cells.

The concentration of the iron-chelating agent, desferrioxamine (Desferal), that just inhibits iron entry into HeLa cells is also the concentration that inhibits DNA synthesis. As a first step in clarification of the mechanism whereby iron may partake in DNA synthesis, we have partially characterized several of the intracellular iron-binding sites. Most cytoplasmic iron appears to be bound to a polysaccharide containing glucose that sediments at about 32 S. Nucleolar iron is bound to a single protein, the mobility of which is independent of the concentration of sodium dodecyl sulfate in an acrylamide gel. In contrast the pattern and mobility of nuclear iron, other than nucleolar, is heterogeneous and markedly affected by the concentration of sodium dodecyl sulfate. The evidence suggests that nuclear iron is bound to protein through one or more intermediate(s).