Inside Scoop on Iron

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Science  18 Dec 1998:
Vol. 282, Issue 5397, pp. 2149
DOI: 10.1126/science.282.5397.2149e

As an essential constituent of many enzymes, iron is avidly sought and sequestered by microorganisms. Siderophores are small secreted molecules that chelate iron in a bioavailable form. Ferguson et al. (p. 2215; see the Perspective by Braun) present the crystal structure at 2.5 angstroms of the integral membrane protein FhuA from Escherichia coli. This protein mediates the energy-dependent transport of the iron-containing siderophore across the outer membrane. FhuA exhibits a remarkable cork-in-a-bottleneck conformation, and the structure of the protein in complex with its substrate reveals how subtle deformations of the cork translocate the iron chelate from the extracellular medium into the periplasmic space.

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