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Enhanced binding of TonB to a ligand-loaded outer membrane receptor : role of the oligomeric state of TomB in formation of a functional FhuA-TonB complex

Cezar M. Khursigara, Gregory De Crescenzo, Peter D. Pawelek et James W. Coulton

Article de revue (2004)

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Abstract

The ferric hydroxymate uptake (FhuA) receptor from Escherichia coli facilitates transport of siderophores ferricrocin and ferrichrome and siderophore-antibiotic conjugates such as albomycin and rifamycin CGP 4832. FhuA is also the receptor for phages T5, T1, Φ80, UC-1, for colicin M and for the antimicrobial peptide microcin MccJ21. Energy for transport is provided by the cytoplasmic membrane complex TonB·ExbB·ExbD, which uses the proton motive force of the cytoplasmic membrane to transduce energy to the outer membrane. To accomplish energy transfer, TonB contacts outer membrane receptors. However, the stoichiometry of TonB· receptor complexes and their sites of interaction remain uncertain. In this study, analyses of FhuA interactions with two recombinant TonB proteins by analytical ultracentrifugation revealed that TonB forms a 2:1 complex with FhuA. The presence of the FhuA-specific ligand ferricrocin enhanced the amounts of complex but is not essential for its formation. Surface plasmon resonance experiments demonstrated that FhuA·TonB interactions are multiple and have apparent affinities in the nanomolar range. TonB also possesses two distinct binding regions: one in the C terminus of the protein, for which binding to FhuA is ferricrocin-independent, and a higher affinity region outside the C terminus, for which ferricrocin enhances interactions with FhuA. Together these experiments establish that FhuA·TonB interactions are more intricate than originally predicted, that the TonB·FhuA stoichiometry is 2:1, and that ferricrocin modulates binding of FhuA to TonB at regions outside the C-terminal domain of TonB.

Sujet(s): 1800 Génie chimique > 1800 Génie chimique
Organismes subventionnaires: NSERC / CRSNG, Canadian Institutes of Health Research (CIHR)
URL de PolyPublie: https://publications.polymtl.ca/24907/
Titre de la revue: Journal of Biological Chemistry (vol. 279, no 9)
Maison d'édition: Elsevier
DOI: 10.1074/jbc.m311784200
URL officielle: https://doi.org/10.1074/jbc.m311784200
Date du dépôt: 18 avr. 2023 15:19
Dernière modification: 09 févr. 2025 02:35
Citer en APA 7: Khursigara, C. M., De Crescenzo, G., Pawelek, P. D., & Coulton, J. W. (2004). Enhanced binding of TonB to a ligand-loaded outer membrane receptor : role of the oligomeric state of TomB in formation of a functional FhuA-TonB complex. Journal of Biological Chemistry, 279(9), 7405-7412. https://doi.org/10.1074/jbc.m311784200

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