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- Title
Structural basis for promotion of duodenal iron absorption by enteric ferric reductase with ascorbate.
- Authors
Ganasen, Menega; Togashi, Hiromi; Takeda, Hanae; Asakura, Honami; Tosha, Takehiko; Yamashita, Keitaro; Hirata, Kunio; Nariai, Yuko; Urano, Takeshi; Yuan, Xiaojing; Hamza, Iqbal; Mauk, A. Grant; Shiro, Yoshitsugu; Sugimoto, Hiroshi; Sawai, Hitomi
- Abstract
Dietary iron absorption is regulated by duodenal cytochrome b (Dcytb), an integral membrane protein that catalyzes reduction of nonheme Fe3+ by electron transfer from ascorbate across the membrane. This step is essential to enable iron uptake by the divalent metal transporter. Here we report the crystallographic structures of human Dcytb and its complex with ascorbate and Zn2+. Each monomer of the homodimeric protein possesses cytoplasmic and apical heme groups, as well as cytoplasmic and apical ascorbate-binding sites located adjacent to each heme. Zn2+ coordinates to two hydroxyl groups of the apical ascorbate and to a histidine residue. Biochemical analysis indicates that Fe3+ competes with Zn2+ for this binding site. These results provide a structural basis for the mechanism by which Fe3+ uptake is promoted by reducing agents and should facilitate structure-based development of improved agents for absorption of orally administered iron. Ganasen et al. report the crystallographic structures of human duodenal cytochrome b and its complex with ascorbate and Zn2+. This study provides mechanistic insights into how reducing agents promote the uptake of orally administered iron and may facilitate the development of such interventions.
- Subjects
IRON in the body; DIETARY supplements; CYTOCHROME b; DUODENUM; MEMBRANE proteins; CRYSTALLOGRAPHY; CYTOPLASM
- Publication
Communications Biology, 2018, Vol 1, Issue 1, pN.PAG
- ISSN
2399-3642
- Publication type
Article
- DOI
10.1038/s42003-018-0121-8