Volume 90 Issue 41 | p. 42 | Concentrates
Issue Date: October 8, 2012

Bacteria Confiscate Unstable Iron-Citrate Complex

Unique protein may give Bacillus cereus a leg up in sequestering the life-essential element iron
Department: Science & Technology
News Channels: Biological SCENE, Materials SCENE
Keywords: iron chelator, citrate, siderophore, bacillus cereus
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A model for Fe3(citrate)3 shows iron in orange, citrate oxygen in red, citrate carbon in white, and protein ligands or water oxygen in green.
Credit: Proc. Natl. Acad. Sci. USA
A model for Fe3(citrate)3 shows iron in orange, citrate oxygen in red, citrate carbon in white, and protein ligands or solution water oxygen in green.
 
A model for Fe3(citrate)3 shows iron in orange, citrate oxygen in red, citrate carbon in white, and protein ligands or water oxygen in green.
Credit: Proc. Natl. Acad. Sci. USA

A unique bacterial protein selectively binds an unstable triferric citrate complex to import iron into Bacillus cereus cells, reports a team from the University of California, Berkeley (Proc. Natl. Acad. Sci. USA, DOI: 10.1073/pnas.1210131109). Iron is an essential element that bacteria commonly sequester by sending ligands, called siderophores, to chelate insoluble Fe3+ in the environment. Selective binding and transport proteins then convey the complexes back into the cells. Common siderophores include citrate ([COH(COO)(CH2COO)2]3–) and citrate-based ligands. Citrate’s carboxyl and hydroxyl groups coordinate Fe3+. Previously, however, citrate-binding proteins were observed harboring only Fe(citrate)2 and Fe2(citrate)2. Kenneth N. Raymond and colleagues have now identified a B. cereus protein, christened ferric citrate-binding protein C, or FctC, that selectively binds Fe3(citrate)3 even when other iron-citrate species are present in solution. Only a few closely related species have genes for similar proteins, so FctC may give the B. cereus group an advantage by enabling import of iron complexes that other bacteria cannot sequester.

 
Chemical & Engineering News
ISSN 0009-2347
Copyright © American Chemical Society

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