Duodenal cytochrome b or ferric-chelate reductase 3, a cytochrome b(561), as found in vertebrates, which might act as a ferric-chelate reductase, catalyzing the reduction of Fe(3+) to Fe(2+), such as associated with the transport of iron from the endosome to the cytoplasm. It is assumed that this protein uses ascorbate as the electron donor. This protein is expressed at the brush border of duodenal enterocytes and may play a role in the uptake of dietary Fe(3+), facilitating its transport into the mucosal cells. It may also be involved in the recycling of extracellular ascorbate in erythrocyte membranes, and act as a ferrireductase in epithelial cells of the respiratory system. Belongs to the cytochrome b(561) family, which are secretory vesicle-specific electron transport proteins. Cytochromes b(561) are integral membrane proteins that bind two heme groups non-covalently, and may have six alpha-helical trans-membrane segments.
Jiyao W et al.(2023). "The conserved domain database in 2023.",