TonB interacts with nonreceptor proteins in the outer membrane of Escherichia coli

Penelope I. Higgs, Tracy E. Letain, Kelley K. Merriam, Neal S. Burke, Ha Jeung Park, Chul Hee Kang, Kathleen Postle

Research output: Contribution to journalArticle

21 Citations (Scopus)

Abstract

The Escherichia coli TonB protein serves to couple the cytoplasmic membrane proton motive force to active transport of iron-siderophore complexes and vitamin B12 across the outer membrane. Consistent with this role, TonB has been demonstrated to participate in strong interactions with both the cytoplasmic and outer membranes. The cytoplasmic membrane determinants for that interaction have been previously characterized in some detail. Here we begin to examine the nature of TonB interactions with the outer membrane. Although the presence of the siderophore enterochelin (also known as enterobactin) greatly enhanced detectable cross-linking between TonB and the outer membrane receptor, FepA, the absence of enterochelin did not prevent the localization of TonB to the outer membrane. Furthermore, the absence of FepA or indeed of all the iron-responsive outer membrane receptors did not alter this association of TonB with the outer membrane. This suggested that TonB interactions with the outer membrane were not limited to the TonB-dependent outer membrane receptors. Hydrolysis of the murein layer with lysozyme did not alter the distribution of TonB, suggesting that peptidoglycan was not responsible for the outer membrane association of TonB. Conversely, the interaction of TonB with the outer membrane was disrupted by the addition of 4 M NaCl, suggesting that these interactions were proteinaceous. Subsequently, two additional contacts of TonB with the outer membrane proteins Lpp and, putatively, OmpA were identified by in vivo cross-linking. These contacts corresponded to the 43-kDa and part of the 77-kDa TonB-specific complexes described previously. Surprisingly, mutations in these proteins individually did not appear to affect TonB phenotypes. These results suggest that there may be multiple redundant sites where TonB can interact with the outer membrane prior to transducing energy to the outer membrane receptors.

Original languageEnglish (US)
Pages (from-to)1640-1648
Number of pages9
JournalJournal of bacteriology
Volume184
Issue number6
DOIs
StatePublished - Mar 12 2002

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Escherichia coli
Membranes
Proteins
Enterobactin
Siderophores
Peptidoglycan
Cell Membrane
Iron
Proton-Motive Force
Active Biological Transport
Escherichia coli Proteins
Vitamin B 12
Muramidase
Membrane Proteins
Hydrolysis
Phenotype
Mutation

All Science Journal Classification (ASJC) codes

  • Microbiology
  • Molecular Biology

Cite this

Higgs, P. I., Letain, T. E., Merriam, K. K., Burke, N. S., Park, H. J., Kang, C. H., & Postle, K. (2002). TonB interacts with nonreceptor proteins in the outer membrane of Escherichia coli. Journal of bacteriology, 184(6), 1640-1648. https://doi.org/10.1128/JB.184.6.1640-1648.2002
Higgs, Penelope I. ; Letain, Tracy E. ; Merriam, Kelley K. ; Burke, Neal S. ; Park, Ha Jeung ; Kang, Chul Hee ; Postle, Kathleen. / TonB interacts with nonreceptor proteins in the outer membrane of Escherichia coli. In: Journal of bacteriology. 2002 ; Vol. 184, No. 6. pp. 1640-1648.
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Higgs, PI, Letain, TE, Merriam, KK, Burke, NS, Park, HJ, Kang, CH & Postle, K 2002, 'TonB interacts with nonreceptor proteins in the outer membrane of Escherichia coli', Journal of bacteriology, vol. 184, no. 6, pp. 1640-1648. https://doi.org/10.1128/JB.184.6.1640-1648.2002

TonB interacts with nonreceptor proteins in the outer membrane of Escherichia coli. / Higgs, Penelope I.; Letain, Tracy E.; Merriam, Kelley K.; Burke, Neal S.; Park, Ha Jeung; Kang, Chul Hee; Postle, Kathleen.

In: Journal of bacteriology, Vol. 184, No. 6, 12.03.2002, p. 1640-1648.

Research output: Contribution to journalArticle

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T1 - TonB interacts with nonreceptor proteins in the outer membrane of Escherichia coli

AU - Higgs, Penelope I.

AU - Letain, Tracy E.

AU - Merriam, Kelley K.

AU - Burke, Neal S.

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AU - Kang, Chul Hee

AU - Postle, Kathleen

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N2 - The Escherichia coli TonB protein serves to couple the cytoplasmic membrane proton motive force to active transport of iron-siderophore complexes and vitamin B12 across the outer membrane. Consistent with this role, TonB has been demonstrated to participate in strong interactions with both the cytoplasmic and outer membranes. The cytoplasmic membrane determinants for that interaction have been previously characterized in some detail. Here we begin to examine the nature of TonB interactions with the outer membrane. Although the presence of the siderophore enterochelin (also known as enterobactin) greatly enhanced detectable cross-linking between TonB and the outer membrane receptor, FepA, the absence of enterochelin did not prevent the localization of TonB to the outer membrane. Furthermore, the absence of FepA or indeed of all the iron-responsive outer membrane receptors did not alter this association of TonB with the outer membrane. This suggested that TonB interactions with the outer membrane were not limited to the TonB-dependent outer membrane receptors. Hydrolysis of the murein layer with lysozyme did not alter the distribution of TonB, suggesting that peptidoglycan was not responsible for the outer membrane association of TonB. Conversely, the interaction of TonB with the outer membrane was disrupted by the addition of 4 M NaCl, suggesting that these interactions were proteinaceous. Subsequently, two additional contacts of TonB with the outer membrane proteins Lpp and, putatively, OmpA were identified by in vivo cross-linking. These contacts corresponded to the 43-kDa and part of the 77-kDa TonB-specific complexes described previously. Surprisingly, mutations in these proteins individually did not appear to affect TonB phenotypes. These results suggest that there may be multiple redundant sites where TonB can interact with the outer membrane prior to transducing energy to the outer membrane receptors.

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