An iron-regulated ferric reductase associated with the absorption of dietary iron

The ability of intestinal mucosa to absorb dietary ferric iron is attribute d to the presence of a brush-border membrane reductase activity that displa ys adaptive responses to iron status. We have isolated a complementary DNA, Dcytb (for duodenal cytochrome b), which encoded a putative plasma membran e di-heme protein in mouse duodenal mucosa. Dcytb shared between 45 and 50% similarity to the cytochrome b561 family of plasma membrane reductases, wa s highly expressed in the brush-border membrane of duodenal enterocytes, an d induced ferric reductase activity when expressed in Xenopus oocytes and c ultured cells. Duodenal expression Levels of Dcytb messenger RNA and protei n were regulated by changes in physiological modulators of iron absorption. Thus, Dcytb provides an important element in the iron absorption pathway.