AN ESTROGEN INDUCIBLE 104 KDA CHAPERONE GLYCOPROTEIN BINDS FERRIC IRON-CONTAINING PROTEINS - A POSSIBLE ROLE IN INTRACELLULAR IRON TRAFFICKING

We have previously described an estrogen inducible, intracellular, hom odimeric membrane glycoprotein (subunit M-r 104 kDa) which is structur ally related to 'chaperone' proteins (Poola, I. and Kiang J.G., J. Bio l. Chem. 269 (1993) 21762-21769). In this report we describe a novel f inding that the 104 kDa chaperone protein exhibits affinity for iron c ontaining proteins such as transferrins from several species, human la ctoferrin and microbial ferric binding protein (FBP). A single ferric ion in the above proteins appears to be sufficient for binding, It als o binds to immobilized ferritin, However, it does not exhibit any affi nity for apotransferrins, apolactoferrin, apoferritin and apoFBP. This is the first report of a chaperone protein that exhibits affinity for iron containing proteins. (C) 1997 Federation of European Biochemical Societies.