Siderophore-mediated mechanism of gallium uptake demonstrated in the microorganism Ustilago sphaerogena.

The radioactive gallium analog of ferrichrome, Ga-67 deferriferrichrome, has been prepared and compared with ferrichrome in the specific siderophore-transport system of Ustilago sphaerogena. The gallium analog is taken up by the cells in an active transport process indistinguishable from that of ferrichrome. Ga(III) effectively competes with Fe(III) for siderophore ligands both in vitro and in vivo at a rate that is highly dependent upon the chemical nature of the ligand. The findings may explain how Ga(III) mimics Fe(III) in clinical use.