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Active transport of an antibiotic rifamycin derivative by the outer-membrane protein FhuA

Active transport of an antibiotic rifamycin derivative by the outer-membrane protein FhuA

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FERGUSON, Andrew D., Jiri KÖDDING, Georg WALKER, Christoph BÖS, James W. COULTON, Kay DIEDERICHS, Volkmar BRAUN, Wolfram WELTE, 2001. Active transport of an antibiotic rifamycin derivative by the outer-membrane protein FhuA. In: Structure. 9(8), pp. 707-716. ISSN 0969-2126

@article{Ferguson2001Activ-6700, title={Active transport of an antibiotic rifamycin derivative by the outer-membrane protein FhuA}, year={2001}, doi={10.1016/S0969-2126(01)00631-1}, number={8}, volume={9}, issn={0969-2126}, journal={Structure}, pages={707--716}, author={Ferguson, Andrew D. and Ködding, Jiri and Walker, Georg and Bös, Christoph and Coulton, James W. and Diederichs, Kay and Braun, Volkmar and Welte, Wolfram} }

Braun, Volkmar Diederichs, Kay Diederichs, Kay Ködding, Jiri 2011-03-24T17:28:30Z Ködding, Jiri Braun, Volkmar Walker, Georg Bös, Christoph Ferguson, Andrew D. deposit-license Coulton, James W. Bös, Christoph Welte, Wolfram 2001 Active transport of an antibiotic rifamycin derivative by the outer-membrane protein FhuA Walker, Georg eng application/pdf BACKGROUND: FhuA, an integral membrane protein of Escherichia coli, actively transports ferrichrome and the structurally related antibiotic albomycin across the outer membrane. The transport is coupled to the proton motive force, which energizes FhuA through the inner-membrane protein TonB. FhuA also transports the semisynthetic rifamycin derivative CGP 4832, although the chemical structure of this antibiotic differs markedly from that of ferric hydroxamates.<br /><br />RESULTS: X-ray crystallography revealed that rifamycin CGP 4832 occupies the same ligand binding site as ferrichrome and albomycin, thus demonstrating a surprising lack of selectivity. However, the binding of rifamycin CGP 4832 is deviant from the complexes of FhuA with hydroxamate-type ligands in that it does not result in the unwinding of the switch helix but only in its destabilization, as reflected by increased B factors. Unwinding of the switch helix is proposed to be required for efficient binding of TonB to FhuA and for coupling the proton motive force of the cytoplasmic membrane with energy-dependent ligand transport. The transport data from cells expressing mutant FhuA proteins indicated conserved structural and mechanistic requirements for the transport of both types of compounds.<br /><br />CONCLUSIONS: We conclude that the binding of rifamycin CGP 4832 destabilizes the switch helix and promotes the formation of a transport-competent FhuA-TonB complex, albeit with lower efficiency than ferrichrome. Active transport of this rifamycin derivative explains the 200-fold increase in potency as compared to rifamycin, which is not a FhuA-specific ligand and permeates across the cell envelope by passive diffusion only. Coulton, James W. First publ. in: Structure 9 (2001), pp. 707 716 Ferguson, Andrew D. Welte, Wolfram 2011-03-24T17:28:30Z

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