Iron is an essential element for a variety physiological process. A variety of proteins are involved in the transport of iron. Most dietary iron exists in the form of ferric iron complexes which must be reduced to yield ferrous ion before it can be taken up by protein transporters such as DCT1 (divalent cation transporter)/NRAMP2/DMT1. These transporters are especially active in small intestine where most dietary iron absorption is conducted. Ferrous Fe (II) is very unstable at physiological pH and quickly oxidized to ferric Fe (III). Therefore, highly specialized transmembrane electron transport system, maintained by ferric reductases, is required for the availability of intracellular ferrous ion. A number of ferric reductases have been identified in yeast, plants, and bacteria but the identity of such proteins remained unknown in the mammals. Most recently, a new gene called Dcytb (for duodenal cytochrome b) has been cloned and characterized in mouse duodenum that may function as mammalian ferric reductase. Dcytb (human 286aa, rat 290aa) is a 6-transmembrane domains protein with ~45% sequence identity with cytochrome b561 reductase. No sequence homology exists with plant and yeast Dcytb. The N-terminus of mouse Dcytb is almost identical with the rabbit's p30 protein called cytochrome b558. Putative biding sites for cytochrome b561 substrates (ascorbic acid and semidehydroascorbic acid) are partially conserved in Dcytb and b561. Unlike most proteins involved in iron metabolism, Dcytb gene lacks a definable iron-responsive element. Dcytb is highly expressed in the brush border membrane of duodenal entrecotes.
Intended for research use only. Not for use in human, therapeutic, or diagnostic applications.