Structure of TonB in Complex with FhuA, E. coli Outer Membrane Receptor

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Science  02 Jun 2006:
Vol. 312, Issue 5778, pp. 1399-1402
DOI: 10.1126/science.1128057

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The cytoplasmic membrane protein TonB spans the periplasm of the Gram-negative bacterial cell envelope, contacts cognate outer membrane receptors, and facilitates siderophore transport. The outer membrane receptor FhuA from Escherichia coli mediates TonB-dependent import of ferrichrome. We report the 3.3 angstrom resolution crystal structure of the TonB carboxyl-terminal domain in complex with FhuA. TonB contacts stabilize FhuA's amino-terminal residues, including those of the consensus Ton box sequence that form an interprotein β sheet with TonB through strand exchange. The highly conserved TonB residue arginine-166 is oriented to form multiple contacts with the FhuA cork, the globular domain enclosed by the β barrel.

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